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Rf fundamentals

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To all those readers who are curious to understand the fundamentals of RF Circuit Design

Publié dans : Ingénierie

Rf fundamentals

  1. 1. RF Fundamentals Author S.Satish Babu RF& Digital Wireless Systems Engineer @Satish Sura
  2. 2. Course Contents Module – 1 Learning Basics of RF RF and Transmission Line Fundamentals RF and Transmission Line MeasurementsRF and Transmission Line Measurements Problem Solving Assignments @Satish Sura
  3. 3. Course Contents Module – 2 RF Communication Systems & Modulation Techniques Digital RF MeasurementsDigital RF Measurements RF System Design Blocks RF PCB Board Design Guidelines EMC Shielding @Satish Sura
  4. 4. Course Contents Module – 3 Wireless Technologies (ISM & Cellular) Bluetooth ZigbeeZigbee WiFi GSM/GPRS, WiMAX & LTE Antenna Design Basics @Satish Sura
  5. 5. MODULE – 1 @Satish Sura
  6. 6. What is RF? RF is anything related to “EM signals”. RF is characterized by Frequency and Amplitude. RF is synonymous with wireless and high frequency signals. describing anything from AM radio 535KHz to computer LAN at 2.4GHz and 5.0GHZ – TO – 90GHz. Electromagnetic Spectrum @Satish Sura Electromagnetic Spectrum
  7. 7. RF Properties All radio frequency signals have the following properties: Amplitude FrequencyFrequency Wavelength Phase and Polarization @Satish Sura
  8. 8. Frequency and Amplitude Frequency: The number of times a signal goes through a complete “up and down” cycle in one second of time – Measured in Hertz. Amplitude: The difference between the maximum and minimum value during one cycle – Measured in Volts. Related with strength or power of the signal @Satish Sura
  9. 9. Wavelength Wavelength: The wavelength of an RF signal is a function of the signal’s frequency and it’s speed through space. Wavelength: The distance a radio wave will travel during one cycle is given by: λ = c/f λ is the wave length, in metersλ is the wave length, in meters c is the speed of light, 3x10^8 m/s or 299793 m/s The value of speed 299793 m/s is in a vacuum without any kind of external influence, this is also the speed of RF wave f is the frequency in Hz @Satish Sura
  10. 10. Frequency (f) Wavelength(λ) Graph Remark 900MHz λ = 299793/900 = 0.33m Long wavelength Wavelength 2.4GHz λ = 299793/2.4 = 0.125m Medium wavelength 5.0GHz λ = 299793/5.0 = 0.06m Short wavelength @Satish Sura
  11. 11. Wavelength Also λ = V/f or Where : λ = Wavelength in meters V = Velocity of radio wave ( speed of light) f = Frequency of radio wave in Hertz EnergyEnergy E = hC / λ Where: E = Energy in Joules h = Plank’s constant(6.63 x 10^34) joules/sec C = Speed of Light λ = wave length in meters @Satish Sura
  12. 12. Assignment -1 Calculate the wavelength for the following frequencies and draw the graph. Frequency (f) Wavelength(λ) Graph 433MHz ? ? 700MHz ? ?700MHz ? ? 2.1GHz ? ? 2.3GHz ? ? 3.6GHz ? ? 60GHz ? ? @Satish Sura
  13. 13. Phase Phase is a method of expressing the relationship between the amplitudes of two RF signals that have the same frequency. Phase is measured in degrees . @Satish Sura
  14. 14. Polarization A radio wave is actually made of up of two fields: One electric, E – Plane One magnetic, H – Plane The sum of these two field is called the “electromagnetic field”, When energy is transferred back and forth from one field to the other it is called “Oscillation”one field to the other it is called “Oscillation” @Satish Sura
  15. 15. RF Fundamentals – Scientific Notations We use scientific notation that uses the power of ten to multiply the values milli (m) 1mV micro(µ) 1µV Kilo(k) 1kHz mega(M) 1MHz giga(G) 1GHz @Satish Sura
  16. 16. RF Fundamentals –Bandwidth Bandwidth:It is the difference between upper and lower frequencies in a contentious set of frequencies. It is typically measured in Hertz(Hz). It is the width of the range of frequencies that a signal occupies on a giventhat a signal occupies on a given transmission medium. Voice Transmission – 3KHz FM Radio Broadcast – 200KHz Analog TV broadcast – 6MHz @Satish Sura
  17. 17. The Radio Spectrum Frequency(f) Wavelength(λ) Band Description 30-300Hz ELF Extremely low frequency 300-3000Hz VF Voice Frequency 3-30kHz 100-10km VLF Very Low Frequency 30-300khz 10-1km LF Low Frequency 0.3-3MHz 1-0.1km MF Medium Frequency 3-30MHz 100-10m HF High Frequency 30-300MHz 10-1m VHF Very High Frequency 300-3000MHz 100-10cm UHF Ultra -high Frequency 3-30GHz 10-1cm SHF Super-high Frequency @Satish Sura 30-300GHz 10-1mm EHF Extremely High Frequency (millimeter wave)
  18. 18. RF – Transmission Line FundamentalsFundamentals @Satish Sura
  19. 19. RF – Transmission Lines In RF circuits, RF energy has to be transported: Over The Air Cables Transmission lines As we transport energy, it gets lost due to Resistance of the wire – lossy cable Radiation (the energy radiates out of the wire – the wire is acting as an antenna @Satish Sura
  20. 20. RF – Transmission Lines – Representation Transmission lines include (physical construction): Two parallel wires Coaxial cable Micro-strip line Optical fiberOptical fiber Waveguide (very high frequencies, very low loss, expensive) etc. @Satish Sura
  21. 21. Types of Transmission Modes @Satish Sura
  22. 22. Electric Field – E, Magnetic Field – M & Propagation Electric and magnetic fields are orthogonal to one another, and both are orthogonal to direction of propagation @Satish Sura
  23. 23. Example of TEM Mode Electric field E is radial Magnetic field H is azimuthal propagation @Satish Sura
  24. 24. Types of PCB Transmission Lines Many of RF components require controlled impedance transmission lines that will transport RF power to (or from) IC pins on the PCB. These transmission lines can be implemented on exterior layer (top or bottom), or Buried in an internal layer.Buried in an internal layer. Guidelines for these transmission lines include relating to: Microstrip, Suspended Stripline, Coplanar Waveguide (grounded), Characteristic Impedance @Satish Sura
  25. 25. Types of PCB Transmission Lines Microstrip Microstrip transmission line consists of fixed-width metal routing (the conductor), along with a solid unbroken ground plane located directly underneath (on the adjacent layer). A microstrip on Layer 1 (top metal) requires a solid ground plane on Layer 2.on Layer 2. The width of the routing, the thickness of the dielectric layer, and the type of dielectric determine the characteristic impedance (typically 50Ω or 75Ω). @Satish Sura
  26. 26. Types of PCB Transmission Lines Suspended Stripline Stripline transmission lines consists of a fixed-width routing on an inner layer, with solid ground planes above and below the center conductor. The conductor can be located midway between the ground planes.planes. This is the appropriate method for RF routing on inner layers. @Satish Sura
  27. 27. Types of PCB Transmission Lines Coplanar Waveguide (Grounded) A coplanar waveguide provides for better isolation between nearby RF lines, as well as other signal lines. This medium consists of a center conductor with ground planes on either side and below. Via "fences" are recommended on both sides of a coplanarVia "fences" are recommended on both sides of a coplanar waveguide. @Satish Sura
  28. 28. Types of PCB Transmission Lines Characteristic Impedance The outer laminated layers of typical PCBs often contain less glass content than the core of the board. For example, FR4 core is generally given as εR = 4.2, whereas the outer laminate (prepreg) layers are typically εR = 3.8. @Satish Sura
  29. 29. Dielectric Constant of Materials @Satish Sura
  30. 30. RF Attenuation and Wave Propagation @Satish Sura
  31. 31. RF wave travelling in a Substrate The RF wave travelling in a substrate (dielectric material) do speed down to the amount of: is the dielectric constant of substrate Example: Calculate the speed of an RF wave in a PCBExample: Calculate the speed of an RF wave in a PCB manufactured according to a basic FR4 spec. Calculation: For a basic FR4 PCB material the dielectric constant is 4.6 : 299792458/ 4.6 = 139.78*10^8 m/s @Satish Sura
  32. 32. Example1: Calculate the speed of an RF wave in a metal dielectric capacitor of Si3N4 , SiO2 which is 2.7-4.2 and 3.5-9 respectively. Example2: Calculate the speed of an RF wave in a Rogers RO4003C PCB dielectric material which is 3.55. Assignment -2 Example3: Calculate the speed of an RF wave in a Isola 370HR PCB dielectric material which is 4.04. Example4: What is the wave length transmitted from the commercial frequency band-33 of 1900MHz in air/FR-4 Isola 370HR? @Satish Sura
  33. 33. RF & Transmission Line MeasurementsMeasurements @Satish Sura
  34. 34. The logarithmic characteristic of the dB, makes it very convenient for expressing RF electrical power USE OF dB in RF for expressing RF electrical power and power ratios. @Satish Sura
  35. 35. In the RF world the common standard is to refer powers to 1 mW (0.001 Watts). Such power ratio, expressed in decibels, is called dBm. RF – Power (dBm) PdBm = 10log10 (PWatts / 1 mW) RF – Power (dB) Signal -1 has a power of P1 Watts Signal-2 has a power of P2 WattsSignal-2 has a power of P2 Watts PdB = 10log10 (P2 / P1) Signal-1 with an RMS voltage of V1 across the load Signal-2 with an RMS voltage of V2 across the load VdB = 20 log10 (V2 / V1) RF – Voltage @Satish Sura
  36. 36. Assignment – 3 Power unit: dBm, relative to 1mW Power in dBm = 10 × log (power in watts/0.001 watts) Example: 1 W is 10 × log 1000 = 30 dBm Calculate power for 2W, 10W, 20W, 100mW, 10mW in dBm @Satish Sura
  37. 37. Signal to Noise Ratio—SNR Ratio Signal to Noise Ratio or SNR is defined as the ratio of the transmitted power to the noise power. To calculate the SNR value, we add the Signal Value to the Noise Value to get the SNR ratio. A positive value of the SNR ratio is always better.A positive value of the SNR ratio is always better. For example, say Signal value is -55dBm and Noise value is -95dBm. The difference of Signal (-55dBm) + Noise (-95dBm) = 40db—This means SNR is 40. @Satish Sura
  38. 38. RF – Gain & Loss Gain Is the term used to describe an increase in an RF signal amplitude. Loss Loss describes a decrease in signal amplitude. Cable resistance can cause loss of signal, since resistance coverts @Satish Sura resistance can cause loss of signal, since resistance coverts electrical signals to heat.
  39. 39. When the decibel figure is positive, the second signal is stronger than the first one, and the power ratio is called gain. When the decibel figure is negative, the second signal is weaker than the first one, and the power ratio is called loss. In amplifiers the gain, also called the amplification factor, in often Gain & Loss Blocks of an RF System In amplifiers the gain, also called the amplification factor, in often expressed in decibels. @Satish Sura
  40. 40. Reflection Coefficient A forward travelling wave when transmitted by a travelling media (substrate, dielectric, wire, etc) and running to the load at the opposite end and at junctions between two different dielectrics, a part of it gets reflected back to the source. The quality of reflection caused at junctions of two different impedances are specified by reflection coefficient. The distance minimum to maximum of a wavelength is called quarter wavelength represented by λ/4 and has 90degree phase shift. @Satish Sura wavelength represented by λ/4 and has 90degree phase shift.
  41. 41. Return Loss VSWR VSWR is the voltage measured along the transmission line leading to an antenna and is the ration of peak amplitude of a standing wave to the minimum amplitude of standing wave Decibel is the logarithmic expression of the ratio between the power, voltage, or current of two signals. Return Loss @Satish Sura
  42. 42. Some Useful Values if a signal at the output of an amplifier is 100 times bigger then the signal at its input, the amplifier has a gain of 100 or, using the definitionsignal at its input, the amplifier has a gain of 100 or, using the definition of decibel, of 20 dB. +3 dB means two times bigger +10 dB means ten times bigger - 3 dB means one half -10 dB means one tenth Rule of thumb: Double the power = 3 dB increase Half the power = 3 dB decrease @Satish Sura
  43. 43. RF – Definitions & Equations dBm – relative to 1 mW dBc – relative to carrier dBi – related to Antenna 10mW = 10dBm, 0dBm = 1mW -110dBm = 1E-11mW = 0.00001nW For a 50 ohm load : -110dBm is 0.7uV, @Satish Sura For a 50 ohm load : -110dBm is 0.7uV, About dBm and W Voltage Ratio aV = 20 log (P2/P1) [aV] = dB Power Ratio aP = 10 log (P2/P1) [aP] = dB Voltage Level V‘ = 20 log (V/1μV) [V‘] = dBμV Power Level P‘ = 10 log (P/1mW) [P‘] = dBm e.g. 25mW max. allowed radiated power in the EU SRD band >> P‘ = 10 log (25mW/1mW) = 10 * 1,39794 dBm >> 14 dBm
  44. 44. RF & Logarithm co-existence Since RF often deals with very large and very small multiplicative ratios, we often work in logarithmic units. Log units are useful because we add multiplicative values 0dBm+20dB-10dB+20dB = 30dBm = 1000mW = 1W @Satish Sura
  45. 45. dBm - Voltage Chat @Satish Sura
  46. 46. Power Budget & Receiver Power Power Budget:The advantage of using decibels instead of Watts to express the power of a signal along an RF chain is that, instead of dividing or multiplying powers to take care of amplifications and attenuations, we just add or subtract the gains and the losses expressed in decibels. Using amplification and attenuation factors and expressing the powers in Watts, we obtain the value of the power at the receiver’s input in this way: PReceiver = PTransmitter×1/AttenuationCable1×Amplification×1/ AttenuationCable2 @Satish Sura
  47. 47. If we use dB to express the gains and the losses and dBm to express the powers, the calculation becomes a simple addition: PReceiver = PTransmitter + LossCable1 + GainAmplifier + LossCable2 Power Budget & Receiver Power The procedure of adding gains and losses to obtain the resulting power for an RF chain is very common and is called Power Budget Calculation @Satish Sura
  48. 48. Receiver Sensitivity: Minimum detectable input signal level for a given output SNR (also called noise floor). Also Receiver sensitivity is the lowest power level at which the receiver can detect an RF signal and demodulate data. Sensitivity is purely a receiver specification and is independent of the transmitter. Receiver Sensitivity @Satish Sura
  49. 49. The performance of any communication link depends on the quality of the equipment being used. Link budget is a way of quantifying the link performance. The received power in an RF link is determined by three factors: transmit power, transmitting antenna gain, and receiving antenna gain. If that power, minus the free space loss of the link path, is greater than Link Budget If that power, minus the free space loss of the link path, is greater than the minimum received signal level of the receiving radio, then a link is possible. The difference between the minimum received signal level and the actual received power is called the link margin. The link margin must be positive, and should be maximized (should be at least 10dB or more for reliable links). @Satish Sura
  50. 50. Link Budget Prx,Ptx – received and transmitted power (dB) Grx,Gtx – antenna gain (dBi) L – path loss Amisc – miscellaneous attenuation P rx = P tx + G tx + G rx – L – A misc @Satish Sura Receiver sensitivity can be got from spec of the device from OEM or from Telecom standard’s manual ex: 3GPP , IEEE etc From the fig site-to-site link being created across a distance of 200m with IEEE 802.11 bridge. Output power of the device 100mW = 20bBm Link Budget 20dBm – 3dB + 7dBi -83dB+7dBi – 3dB – (-94dBm) Link Budget = 39dB Conti…
  51. 51. Radio Range – Free Space Propagation How much loss can we have between TX and RX? Friis’ transmission equation for free space propagation: or Pt is the transmitted power, Pr is the received power Gt is the transmitter, Gr is the receiver antenna gain Lambda is the wavelength D is the distance between transmitter and receiver @Satish Sura
  52. 52. Assignment – 4 Calculate the link budget for the following figure @Satish Sura
  53. 53. Assignment – 5 Calculate the link budget for the following figure @Satish Sura
  54. 54. Free Space Losses Signal power getting diminished by geometric spreading of the wavefront, commonly known as Free Space Loss. loss in signal strength that occurs when an electromagnetic wave travels over a line of sight path in free space. The power of the signal is spread over a wave front, the area of which increases as the distance from the transmitter increases. Therefore, the power density diminishes. @Satish Sura density diminishes.
  55. 55. FSPL, is an essential basic parameter for many RF calculations. It can often be used as a first approximation for many short range calculations. it can be used as a first approximation for a number of areas where there are few obstructions. Free Space Path Loss (FSPL) In a free space, signal decreases in a way that is inversely proportionalIn a free space, signal decreases in a way that is inversely proportional to the square of the distance from the source of the radio signal and it is given by @Satish Sura
  56. 56. Free Space Path Loss (FSPL) - Formula or @Satish Sura Where: FSPL is the Free space path loss (meters) d is the distance of the receiver from the transmitter (meters) λ is the signal wavelength (meters) f is the signal frequency (Hertz) c is the speed of light in a vacuum (meters per second)
  57. 57. As we understand from our previous discussion, the RF comparisons and measurements are performed in decibels. Accordingly it is very convenient to express the free space path loss formula, FSPL, in terms of decibels. Free Space Path Loss (FSPL) – Logarithmic format FSPL (dB) = 20 log10 (d) + 20 log10 (f) + K Where: d is the distance of the receiver from the transmitter (m) f is the signal frequency (MHz) K is Constant has a value of -147.55 for the units used for d and f @Satish Sura
  58. 58. Assignment – 6 An RF Module operating at 2.480GHz frequency and has RF-Power of 1mW placed at a distance of 150m. Calculate the FSPL in dB. @Satish Sura
  59. 59. Link Margin LinkMargin = ReceivedPower - ReceiveSensitivity FSPL (dB ) = TxPower - TxCableLoss – TxAntennaGain + Fade Margin FSPL (dB ) = TxPower - TxCableLoss – TxAntennaGain + RxAntennaGain – RxCableLoss – RxSensitivity – Fade Margin @Satish Sura
  60. 60. Antennas will have certain amount of gain and this will affect the overall signal level. Any antenna gain will reduce the losses. Effect of Antenna Gain on Path Loss Where: Gtx is the gain of the transmitter antenna relative to an isotropic source (dBi) Grx is the gain of the receiver antenna relative to an isotropic source (dBi) Path Loss (dB) = 20 log10(d) + 20 log10(f) + K – Gtx - Grx @Satish Sura
  61. 61. Scattering Parameters (S-Parameters) An RF function is a two-port device with – Characteristic impedance (Z0): • Z0 = 50Ω for wireless communications devices • Z0 = 75Ω for cable TV devices – Gain and frequency characteristics S-Parameters of an RF device – S : input return loss or input reflection coefficient OR Forward– S11 : input return loss or input reflection coefficient OR Forward Reflection (input match - impedance) – S22 : output return loss or output reflection coefficient OR Reverse Reflection (output match - impedance) – S21 : gain or forward transmission coefficient OR Forward Transmission (gain or loss) – S12 : isolation or reverse transmission coefficient (leakage or isolation) @Satish Sura
  62. 62. Impedance Smith Chart This is an impedance chart transformed from rectangular Z. Normalized to 50 ohms, the center = R50+J0 or Zo (perfect match). For S11 or S22 (two-port), you get the complex impedance. @Satish Sura
  63. 63. Impedance Smith Chart @Satish Sura
  64. 64. Creating Matching Network Various topologies can be used: L, C, RVarious topologies can be used: L, C, R Avoid unwanted oscillations (L-C series/parallel) Yield can be a factor in topology (sensitivity) Use the fewest components (cost + efficient) Sweep or tune component values to see S-parameters Optimization: use to meet S-parameter specs (goals) @Satish Sura
  65. 65. Matching Circuit Definition @Satish Sura
  66. 66. Thank YouThank You @Satish Sura
  67. 67. MODULE – 2 @Satish Sura
  68. 68. RF Communication System && Modulation Techniques @Satish Sura
  69. 69. RF Communication Systems RF Communication systems is classified into three systems Simplex communication system Half – Duplex communication system Full – Duplex communication system Simplex System A radio technology that allows only one-way communication fromA radio technology that allows only one-way communication from a transmitter to a receiver Example : FM radio, TV @Satish Sura
  70. 70. RF Communication Systems Half-Duplex System Operation mode of a radio communication system in which each end can transmit and receive, but not simultaneously. The communication is bidirectional over the same frequency, but unidirectional for the duration of a message. These are TDD and TDMA systems. @Satish Sura
  71. 71. RF Communication Systems Full-Duplex System Radio systems in which each end can transmit and receive simultaneously Typically two frequencies are used to set up the communication channel. Each frequency is used solely for either transmitting or receiving. Applies to Frequency Division Duplex (FDD) systems @Satish Sura Applies to Frequency Division Duplex (FDD) systems
  72. 72. The Modern Wireless Standards @Satish Sura
  73. 73. Trends of Wireless Communication System @Satish Sura
  74. 74. Basic Wireless Communication System @Satish Sura
  75. 75. Modulation and Methods Modulation: The process of superimposing a low frequency signal onto a high frequency signal is called Modulation. Three types of modulation schemes are available. Amplitude Modulation – The amplitude of the carrier varies Frequency Modulation – The frequency of the carrier variesFrequency Modulation – The frequency of the carrier varies Phase Modulation – The phase of the carrier varies Modulation of Digital Signal is known as Shift Keying Amplitude Shift Keying Frequency Shift Keying Phase Shift Keying @Satish Sura
  76. 76. Amplitude Shift Keying (ASK): Pros: Simple Cons: Susceptible to noise Ex: Many legacy wireless systems, e.g. AMR Digital Modulation Frequency Shift Keying (FSK): Pros: less susceptible to noise Cons: theoretically requires larger bandwidth/bit than ASKCons: theoretically requires larger bandwidth/bit than ASK Popular in modern systems Gaussian FSK (GFSK), e.g. used in Bluetooth, more bandwidth efficient Phase Shift Keying (PSK): Pros: Less susceptible to noise, Bandwidth efficient Cons: Require synchronization in frequency and phase complicates receivers and transmitters Example: IEEE 802.15.4 / ZigBee @Satish Sura
  77. 77. Bluetooth Modulation Techniques, Freq, Carrier & Power Bluetooth frequencies are all located within the 2.4 GHz ISM band. The ISM band typically extends from 2400 MHz to 2483.5 MHz (i.e. 2.4000 - 2.4835 GHz). The Bluetooth channels are spaced 1 MHz apart. Bluetooth version 1 adopts GFSK - 720Kbps Bluetooth version 2 adopts Enhanced Data Rate (EDR) of π/4 DQPSK(2Mbps) and 8DPSK(3Mbps) with improved data rates.8DPSK(3Mbps) with improved data rates. Bluetooth version 3 is not through modulation technique, but by working with an IEEE 802.11g physical layer data rates of 25Mbps can be achieved. Bluetooth class 1 is designed for 100m & 20dBm, class 2 for 10m & 6 dBm, class 3 for 10cm and 0dBm. π/4 DQPSK 8DPSKGFSK @Satish Sura
  78. 78. BPSK,QPSK, QAM modulation Scheme @Satish Sura
  79. 79. Spread Spectrum Systems Data sent using spread spectrum is intentionally spread over a wide frequency range Appears as noise, so it is difficult to detect and jam Resistant to noise and interference thus increasing the probability that the signal will be received correctly Unlikely to interfere with other signals even if they are transmitted on the same frequency 2 types of Spread Spectrum common in ISM bands: @Satish Sura 2 types of Spread Spectrum common in ISM bands: Direct Sequence Spread Spectrum (DSSS) Frequency Hopping Spread Spectrum (FHSS)
  80. 80. General Model of a Spread Spectrum System @Satish Sura
  81. 81. Direct Sequence Spread Spectrum(DSSS) Each bit represented by multiple bits using spreading code Spreading code spreads signal across wider frequency band Good resistance against interferers @Satish Sura
  82. 82. Frequency Hopping Spread Spectrum (FHSS) Signal broadcast over a seemingly random series of frequencies Receiver hops between frequencies in sync with transmitter Jamming on one frequency affects only a few bits @Satish Sura
  83. 83. DSSS – BPSK Example DSSS-BPSK – Example @Satish Sura DSSS Example
  84. 84. A major disadvantage with fixed modulation (non-adaptive) on channels with varying signal-to-noise ratio (SNR) is that the bit-error-rate (BER) performance. Adaptive Modulation(QPSK,QAM) Most applications require a certain maximum BER. An adaptive modulation scheme, is designed to have a BER which is constant for all channel SNRs. The spectral efficiency of the fixed modulation is constant. The spectral efficiency will increase with increasing channel SNRs for adaptive scheme. @Satish Sura scheme. Thus, the adaptive link becomes much more efficient for data transmission. Applications: WiFi, LTE and high data hungry schemes.
  85. 85. 802.15.4 – Zigbee Modulation Techniques 802.15.4 was developed with lower data rate, simple connectivity and low power battery application in mind. 802.15.4 standard specifies communication can occur in the 868-868.8 MHz, the 902-928 MHz or the 2.400-2.4835 GHz Industrial Scientific and Medical (ISM) bands. The 2.4 GHz band is more popular as it is open in most of the countries worldwide. The 802.15.4 standard specifies, a maximum over-the-air data rate of 250 kbps. At 2.4 GHz, 802.15.4 specifies the use of Direct Sequence Spread Spectrum(DSSS)At 2.4 GHz, 802.15.4 specifies the use of Direct Sequence Spread Spectrum(DSSS) and uses an Offset Quadrature Phase Shift Keying (O-QPSK) with half-sine pulse shaping to modulate the RF carrier. 802.15.4 standard allows for communication in a point-to-point or a point-to- multipoint configuration. IEEE 802.15.4 has 16 channels 11 through 26 between 2.4 GHz and 2.4835 GHz each with a bandwidth of 2 MHz and an inter channel spacing of 5 MHz Typical distance of 70m-300m and 30ms network joining time. Conti….@Satish Sura
  86. 86. 802.15.4 – Zigbee Modulation Techniques @Satish Sura
  87. 87. WiFi modulation Scheme @Satish Sura
  88. 88. Cellular LTE Modulation Scheme LTE takes advantage of OFDMA, a multi-carrier scheme that allocates radio resources to multiple users. OFDMA uses Orthogonal Frequency Division Multiplexing (OFDM). OFDM splits the carrier frequency bandwidth into many small subcarriers spaced at 15 kHz, andinto many small subcarriers spaced at 15 kHz, and then modulates each individual subcarrier using the QPSK, 16-QAM, or 64 – QAM digital modulation formats. OFDMA assigns each user the bandwidth needed for their transmission. Unassigned subcarriers are off, thus reducing power consumption and interference. Conti…. @Satish Sura
  89. 89. OFDMA uses OFDM OFDMA: The scheduling and assignment of resources that makes OFDMA distinctive. In OFDM, the entire bandwidth belongs to a single user for a period of time. Cellular LTE Modulation Scheme single user for a period of time. In OFDMA, multiple users are sharing the bandwidth at each point in time. Conti….@Satish Sura
  90. 90. SC-FDMA In the uplink, LTE uses a pre-coded version of OFDM called SC-FDMA. SC-FDMA has a lower PAPR (Peak-to-Average Power Ratio) than OFDM. This lower PAPR reduces battery power consumption, requires a simpler amplifier design Cellular LTE Modulation Scheme consumption, requires a simpler amplifier design and improves uplink coverage and cell-edge performance. In SC-FDMA, data spreads across multiple subcarriers, unlike OFDMA where each subcarrier transports unique data. The need for a complex receiver makes SC- FDMA unacceptable for the downlink. Conti…. @Satish Sura
  91. 91. LTE Adaptive Modulation and Coding (AMC) Adaptive Modulation and Coding refers to the ability of the network to determine the modulation type and the coding rate dynamically based on the current RF channel conditions reported by the UE. The RF digital modulation used to transport the information is QPSK, 16-QAM, and 64-QAM. Each dot represents a possible symbol. In the QPSK case, there are four possible symbol states andIn the QPSK case, there are four possible symbol states and each symbol carries two bits (2^1) of information. In 16-QAM, there are 16 symbol states. Each 16-QAM symbol carries 4 bits (2^2) . In 64-QAM, there are 64 symbol states. Each 64-QAM symbol carries 6 bits (2^6) . Higher-order modulation is more sensitive to poor channel conditions than the lower-order modulation because the detector in the receiver must resolve smaller differences as the constellations become more dense. @Satish Sura
  92. 92. Digital RF Measurements @Satish Sura
  93. 93. Phase Noise in RF @Satish Sura In a receiver, the phase noise of the LO can mix with a large interfering signal from a neighboring channel and swamp out the signal from the desired channel even though most of the power in the interfering IF is removed by the IF filter. This process is referred to as reciprocal mixing.
  94. 94. Phase Noise in RF Phase noise or phase jitter is of particular importance, because it reduces the signal quality and hence increases the error rate of the communications link. Phase noise is an important aspect of frequency synthesizer and signal generator design, and levels of phase noise must be considered at the earliest stages of design of these items. @Satish Sura stages of design of these items. In a receive chain, the fact that the LO is not a perfect delta function means that there is a continuum of LO’s that can mix with interfering signals and produce energy at the same IF. Here we observe an adjacent channel signal mixing with the “skirt” of the LO and falling on top of the a weak IF signal from the desired channel. Phase Noise in Rx Chain
  95. 95. Noise Figure Where PO is the total output noise @Satish Sura Where PO is the total output noise power, PL is the output noise power that results from noise generated by the load at the output frequency, and PS is the output noise power that results from noise generated by the source at the input frequency.
  96. 96. How good are the transmitters making efficient use of the RF spectrum? Occupied Band Width (OBW) –Narrow Band OBW = Occupied Band Width Occupied Bandwidth (OBW) is a common measurement performed on radio transmitters. This measurement calculates the bandwidth containing the total integrated power occupied in a given signal bandwidth. •% Integrated Power Method: The occupied frequency bandwidth is calculated as the bandwidth containing the specified percentage of thecalculated as the bandwidth containing the specified percentage of the transmitted power. •> dBc Method: The occupied frequency bandwidth is defined as the bandwidth between the upper and lower frequency points at which the signal level is a desired number of dB below the peak carrier level. @Satish Sura
  97. 97. ACP is a measure of the nonlinear characteristics of a device under test (DUT) and indicates the amount of spectral regrowth occurring in adjacent channels. Measured using built-in function of spectrum analyzer Narrowband Transmitter Adjacent Channel Power (ACP) Low phase noise key parameter for low ACP ETSI: Absolute ACP requirement (dBm), ARIB: Relative (dBc) @Satish Sura
  98. 98. How good are the receiver at handling interferers at same frequency? Co-channel rejection Test method: Modulated Interferer Wanted signal 3 dB above sensitivity limit Receiver, Co-channel Rejection @Satish Sura
  99. 99. Receiver Selectivity Selectivity is a measure of the performance of a radio receiver to respond only to the radio signal it is tuned to (such as a radio station) and reject other signals nearby infrequency, such as another broadcast on an adjacent channel. Selectivity is usually measured as a ratio in decibels (dBs), comparing the signal strength received against that of a similar signal on another frequency. If the signal is at the adjacent channel of the selected signal, this measurement is also known as adjacent-channel rejection (ACR)signal, this measurement is also known as adjacent-channel rejection (ACR) or Adjacent-channel Selectivity (ACS) or Adjacent Channel Rejection Ratio (ACRR) @Satish Sura
  100. 100. Receiver, Blocking/desensitization Blocking/desensitization is a measure of how good a receiver is to reject an interferer “far away” (out of band) from the wanted signal Measured the same way as selectivity, but the interfering signalMeasured the same way as selectivity, but the interfering signal is usually not modulated Blocking can be further improved with a SAW filter @Satish Sura
  101. 101. Image Rejection No image rejection Image rejection @Satish Sura
  102. 102. How to achieve good RF sensitivity? Introduce high gain in front of the receiver External LNA needed Poor linearity (IP3) Poor blocking/selectivity “Removes” the losses in the“Removes” the losses in the SAW filter Lower noise bandwidth (narrowband) Blocking/linearity not changed Good selectivity Good frequency control needed @Satish Sura
  103. 103. ERROR VECTOR MAGNITUDE (EVM) Transmission modulation accuracy is measured using error vector magnitude (EVM). The magnitude of the phase difference as a function of time between an ideal reference signal and the measured transmitted signal. EVM is a measure that can beEVM is a measure that can be used to quantify the performance of a digital radio transmitter @Satish Sura
  104. 104. Adjacent Channel Power Ratio (ACPR) The adjacent channel power ratio of a wireless communication system is the integrated power in the carrier channel relative to the adjacent channel. @Satish Sura
  105. 105. Bit Error Rate (BER) Bit error rate is a form of measurement used for digital systems. As the signal level falls or the link quality degrades, so the number of errors in the transmission - bit errors - increases.increases. @Satish Sura
  106. 106. RF System Design BlocksRF System Design Blocks @Satish Sura
  107. 107. Basic Building Blocks of an RF System RF-IC Transmitter Receiver Transceiver Baseband Processor ADC & DAC SOC Crystal Reference frequency for the LO and the carrier frequency Clock & clock buffers Balun Balanced to unbalanced Converts a differential signal to a single-ended signal or vice versa Filter Used if needed to pass regulatory requirements / Antenna Matching regulatory requirements / improve selectivity Antenna Basic Transmitter Circuit Modern transmitters typically use fractional-N synthesizers. For angle modulation like FSK, MSK, O- QPSK, the synthesizer frequency is adjusted. For amplitude modulation like OOK and ASK, the amplifier level is adjusted@Satish Sura
  108. 108. Receiver Architecture Converts the incoming signal to an Intermediate Frequency (IF) signal and performs: Carrier frequency tuning – selects desired signal. Receiver Block Diagram Super Heterodyne Receiver selects desired signal. Filtering – separates signal from other modulated signals picked up. Amplification – compensates for transmission losses in the signal path Super Heterodyne Receiver @Satish Sura
  109. 109. Image Rejection Receiver Architecture Image rejection receiver –The image frequency is an undesired input frequency that is capable of producing the same intermediate frequency (IF) as the desired input frequency produces. Ex: AGC using ADC and filters. @Satish Sura
  110. 110. Transceiver Architecture Super Heterodyne Transceiver block diagram The Transceivers are highly integrated, low power, and high performance IC’s for operation and application specific bands. These are designed with emphasis on flexibility, robustness, ease of use, and low current consumption. The transmitter path of the IC’s are based on a direct closed-loop VCO modulation scheme using a low noise fractional-N RF frequency synthesizer. These have the characteristics of reducing spurious emission and pulling @Satish Sura These have the characteristics of reducing spurious emission and pulling effects.
  111. 111. Basic Building Blocks of Transceiver IC Simple Processor ADC & DAC Transmitter Receiver Clock Generator(PLL & REF Clock Modulator PAPA LNA Filters (BPF) Amplifiers Switches Fractional N Synthesizer Automatic Gain Controller(AGC) @Satish Sura
  112. 112. Understanding the Features of Transceiver IC @Satish Sura
  113. 113. Balun and Matching Circuit @Satish Sura
  114. 114. Extending the Operating Range of an RF System Increase the Output power Add an external Power Amplifier (PA) Increase the sensitivity Add an external Low Noise Amplifier (LNA) Increase both output power and sensitivity Add PA and LNA Use high gain antennas @Satish SuraUse high gain antennas Regulatory requirements need to be followed @Satish Sura
  115. 115. Signal from TXRX Switch pin level shifted and buffered CMOS and GaAs FET switches assures low RX current Simpler control without external LNA A TDMA Switch Adding an External PA to Increase Operating Range TRX @Satish Sura
  116. 116. Adding an External PA/LNA to the Operating Range Along With Duplexer An FDD Communication System @Satish Sura
  117. 117. 120 dB link budget at 433 MHz gives approximately 2000 meters Rule of Thumb: 6 dB improvement ~ twice the distance Double the frequency ~ half the range – 433 MHz longer range than 868 MHz Factors RF Range and Important Factors Factors Antenna (gain, sensitivity to body effects etc.) Sensitivity Output power Radio pollution (selectivity, blocking, IP3) Environment (Line of sight, obstructions, reflections, multipath fading) @Satish Sura
  118. 118. Bandpass Filters @Satish Sura A bandpass signal is a signal containing a band of frequencies not adjacent to zero frequency, such as a signal that comes out of a bandpass filter. An ideal bandpass filter would have a completely flat passband (e.g. with no gain/attenuation throughout) and would completely attenuate all frequencies outside the passband. In practice, no bandpass filter is ideal. there is a region just outside the intended passband where frequencies are attenuated, but not rejected is called filter roll-off.
  119. 119. RF PCB Board Design GuidelinesGuidelines @Satish Sura
  120. 120. Transmission Line Bends and Corner Compensation When transmission lines are required to bend (change direction) due to routing constraints, use a bend radius that is at least 3 times the center conductor width. Bend Radius ≥ 3 × (Line Width) This will minimize any characteristic impedance changes moving through the bend. In cases where a gradually curved bend is not possible, the transmissionIn cases where a gradually curved bend is not possible, the transmission line can undergo a right-angle bend (noncurved). The optimum microstrip right-angle miter is given by the formula of Douville and James: Where M is the fraction (%) of the miter. and is subject to the constraint that w/h ≥ 0.25. @Satish Sura
  121. 121. Transmission Line Bends and Corner Compensation @Satish Sura
  122. 122. Layer Changes for Transmission Lines When layout constraints required that a transmission line move to a different layer, it is recommended that at least two via holes be used for each transition to minimize the via inductance loading. A pair of vias will effectively cut the transition inductance by 50% The largest diameter via should be utilized that is compatible with the transmission line width. If space does not permit the use of larger vias, then two or three small size transition vias. @Satish Sura
  123. 123. Signal Line Isolation RF Transmission Lines: Lines should be kept as far apart as possible to avoid coupling. Signal lines that will carry high power levels should be kept away from all other lines whenever possible. An isolation better than approximately -45dB between RF lines is recommended.recommended. High-Speed Digital Signal Lines: These lines should be routed separately on a different layer than the RF signal lines, to prevent coupling. Digital noise (from clocks, PLLs, etc.) can couple onto RF signal lines, and these can be modulated onto RF carriers. In some cases digital noise can be up/down-converted. @Satish Sura
  124. 124. VCC/Power Lines: These should be routed on a dedicated layer if possible. Power line isolation from the rest of circuit is mandatory. Adequate decoupling/bypass capacitors should be provided at the main VCC distribution node, as well as at VCC branches. The choice of the bypass capacitances must be made based on the Signal Line Isolation The choice of the bypass capacitances must be made based on the overall frequency response of the RF IC, and the expected frequency distribution nature of any digital noise from clocks and PLLs. These lines should be separated from any RF lines that will transmit large amounts of RF power. @Satish Sura
  125. 125. Ground Planes The recommended practice is to use a solid (continuous) ground plane on Layer 2 assuming Layer 1 is used for the RF components and transmission lines. For striplines and offset striplines, ground planes above and below the center conductor are required. These planes must not be shared or assigned to signal or power nets, but must be uniquely allocated to ground.must be uniquely allocated to ground. Partial ground planes on a layer, sometimes required by design constraints, must underlie all RF components and transmission lines. Ground planes must not be broken under transmission line routing. Ground vias between layers should be added liberally throughout the RF portion of the PCB. This helps prevent accrual of parasitic ground inductance due to ground-current return paths. The vias also help to prevent cross-coupling from RF and other signal lines across the PCB. @Satish Sura
  126. 126. Consideration on Bias and Ground Layers While designing PCB stakup, the layers assigned to system bias (DC supply) and ground must be considered in terms of the return current for the components. The general guidance is to not have signals routed on layers between the bias layer and the ground layer. IncorrectIncorrect Layer Assignment Better Layer Assignment @Satish Sura
  127. 127. Power (Bias) Routing and Supply Decoupling A common practice is to use a "star" configuration for the power- supply routes, if a component has several supply connections. A larger decoupling capacitor (tens of µFds) is mounted at the "root" of the star, and smaller capacitors at each of the star branches. Choose the value of the capacitors depends on the operating frequency range of the RF IC.frequency range of the RF IC. The "star" configuration avoids long ground return paths that would result if all the pins connected to the same bias net were connected in series. @Satish Sura
  128. 128. Decoupling or Bypass Capacitors Real capacitors have limited effective frequency ranges due to their self-resonant frequency (SRF). Above the SRF, the capacitor is inductive, and therefore will not perform the decoupling or bypass function. When broadband decoupling is required, standard practice is to use several capacitors of increasing size (capacitance), all connected in parallel.parallel. @Satish Sura
  129. 129. Bypass Capacitor Layout Considerations Since the supply lines must be AC ground, it is important to minimize the parasitic inductance added to the AC ground return path. the vias connecting the VCC pad on the top layer to the inner power plane (layer) potentially impede the AC ground current return, forcing a longer return path with resulting higher parasitic inductance. In this alternate configuration, the AC ground return paths are not blocked by the power-plane vias. Generally this configuration requiresblocked by the power-plane vias. Generally this configuration requires somewhat more PCB area. @Satish Sura
  130. 130. Grounding of Shunt-Connected Components For shunt-connected (grounded) components (such as power- supply decoupling capacitors), the recommended practice is to use at least two grounding vias for each component. This reduces the effect of via parasitic inductance. @Satish Sura
  131. 131. IC Ground Plane ("Paddle") Most ICs require a solid ground plane on the component layer (top or bottom of PCB) directly underneath the component. This ground plane will carry DC and RF return currents through the PCB to the assigned ground plane. "ground paddle" is to provide a thermal heatsink, so the paddle should include the maximum number of thru vias that are allowed byshould include the maximum number of thru vias that are allowed by the PCB design rules. The maximum number of vias that can be accommodated by other layout considerations should be used. These vias are ideally thru-vias and must be plated. the vias should be filled with thermally conductive paste to enhance the heatsink. @Satish Sura
  132. 132. PCB Layout – Rule of Thumb for RF PCB Layout: Rules of thumb for RF Layout Keep via inductance as low as possible. Usually means larger holes or multiple parallel holes) Keep top ground continuous as possible. Similarly for bottom ground. Make the number of return paths equal forMake the number of return paths equal for both digital and RF Current flow is always through least impedance path. Therefore digital signals should not find a lower impedance path through the RF sections. Compact RF paths are better, but observe good RF isolation between pads and or traces. @Satish Sura
  133. 133. PCB Layout: Do’s and Don’ts of RF Layout Keep copper layer continuous for grounds. Keep connections to supply layers short Use IC packages which have higher self-resonance and lower package parasitic components. Use the chips star point ground return Avoid ground loops at the component level and or signal trace. Use vias to move the PCB self resonance higher than signal frequenciesUse vias to move the PCB self resonance higher than signal frequencies Keep trace and components spacing nothing less than 12 mils Keep via holes large at least 14.5 mils Separate high speed signals (e.g. clock signals) from low speed signals, digital from analog. Placement is critical to keep return paths free of mixed signals. Route digital signals traces so antenna field lines are not in parallel to lines of magnetic fields. Keep traces length runs under a ¼ wavelength when possible. @Satish Sura
  134. 134. RF Design Guidelines For Meeting Regulatory Requirements DC supply lines to the IC should have decoupling capacitors close to the IC. The printed circuit board (PCB) should have a solid ground plane in the RF section. Avoid cutouts or slots in this ground layer. Such slots can act as antennas and generate unwanted emissions. Study the harmonics specification of the IC and use a low-pass or band-passStudy the harmonics specification of the IC and use a low-pass or band-pass filter in the transmit path to suppress the harmonics sufficiently. If possible, chose the transmit frequency such that the harmonics do not fall into restricted bands. In most cases shielding may be necessary to reduce spurious emissions. If that is the case, filter all lines leaving the shielded case with decoupling capacitors close to the shield inside the shielding case. Conti ..@Satish Sura
  135. 135. RF Design Guidelines For Meeting Regulatory Requirements Chose proper values of decoupling capacitors. A large capacitance value is not always the best. Good results are achieved with capacitors which are in series resonance with their parasitic inductance at the RF frequency that needs to be filtered out. The loop bandwidth of the PLL oscillator can have an impact on the range of modulation bandwidth or adjacent channel power of a transmitter and the adjacent channel rejection of a receiver. Design the PLL loop filter carefully according to the data rate requirements. In case of battery driven equipment, use a brownout detector to switch off the transmitter before the PLL looses lock due to a low battery voltage. @Satish Sura
  136. 136. EMC Shielding @Satish Sura
  137. 137. EMI, RFI, and Shielding EMC is the ability of a device, unit of equipment, or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment. The equipment under design should neither produce spurious signals, nor should it be vulnerable to out-of-band external signals.signals, nor should it be vulnerable to out-of-band external signals. EMI/RFI can be fundamentally broken down into Source Path Receiver @Satish Sura
  138. 138. EMC Shielding EMI Coupling Paths Interference due to conduction (common-impedance) Interference due to capacitive or inductive coupling (near-field interference) Electromagnetic radiation (far-field interference) Noise Coupling Mechanisms Impedance mismatches and discontinuitiesImpedance mismatches and discontinuities Common-mode impedance mismatches → Differential Signals Capacitively Coupled (Electric Field Interference) dV/dt → Mutual Capacitance → Noise Current (Example: 1V/ns produces 1mA/pF) Inductively Coupled (Magnetic Field) di/dt → Mutual Inductance → Noise Voltage (Example: 1mA/ns produces 1mV/nH) @Satish Sura
  139. 139. Reducing Common-Impedance Noise EMC Shielding Common-impedance noise Decouple op amp power leads at LF and HF Reduce common-impedance Eliminate shared paths Techniques Low impedance electrolytic (LF) and local low inductance (HF) bypasses Low impedance electrolytic (LF) and local low inductance (HF) bypasses Use ground and power planes Optimize system design @Satish Sura
  140. 140. EMC Shielding Noise Induced by Near-Field Interference “Crosstalk” Reducing Capacitance-Coupled Noise Reduce Level of High dV/dt Noise Sources Use Proper Grounding Schemes for Cable Shields Reduce Stray CapacitanceReduce Stray Capacitance Equalize Input Lead Lengths Keep Traces Short Use Signal-Ground Signal-Routing Schemes Use Grounded Conductive Faraday Shields to Protect Against Electric Fields Conti…. @Satish Sura
  141. 141. EMC Shielding Noise Induced by Near-Field Interference “Crosstalk” Reducing Magnetically-Coupled Noise Careful Routing of Wiring Use Conductive Screens for HF Magnetic Shields Use High Permeability Shields for LF Magnetic Fields (mu-Metal) Reduce Loop Area of ReceiverReduce Loop Area of Receiver Twisted Pair Wiring Physical Wire Placement Orientation of Circuit to Interference Reduce Noise Sources Twisted Pair Wiring Driven Shields @Satish Sura
  142. 142. Reducing System Susceptibility To EMI Always Assume That Interference Exists! Use Conducting Enclosures Against Electric and HF Magnetic Fields Use mu-Metal Enclosures Against LF Magnetic Fields Implement Cable Shields Effectively Use Feedthrough Capacitors and Packaged PI Filters EMC Shielding Use Feedthrough Capacitors and Packaged PI Filters @Satish Sura
  143. 143. Board level RF Shielding @Satish Sura
  144. 144. EMI/EMC Design Considerations Critical circuits (i.e. clock circuits, clock driver, etc.) and functions should be grouped together, providing the shortest trace lengths between components. For conducted noise issues, the use of ferrite chokes and proper signal line layout can prevent a host of issues. Basic formula for RF emissions: E = 1.316 AIF2 /(DS) EMC Shielding Basic formula for RF emissions: E = 1.316 AIF2 /(DS) where: E = microvolts / meter A = radiating loop area in cm2 I = current in amps F = frequency in MHz D = measurement distance in meters S = shielding effectiveness ratio @Satish Sura
  145. 145. The most common cause of failures are caused by excessive loop area. High current and high frequency circuits should have the least minimum loop area. EMC Shielding EMI/EMC Design Considerations least minimum loop area. Proper Isolation between the groups preventing noise source imposed over the other. Use of more fine pitch components on a PCB Thinner solder paste thicknesses to prevent shorts or bridges @Satish Sura
  146. 146. EMC Shielding Board Level Shielding Removable Pickup Bridge Shielding @Satish Sura
  147. 147. EMC Shielding Board Level Shielding Recover with lid removable Board level shielding @Satish Sura
  148. 148. EMC Shielding Board Level Shielding @Satish Sura
  149. 149. Thank You @Satish Sura
  150. 150. MODULE – 3 @Satish Sura
  151. 151. RF – Technologies Bluetooth, ZigBee, WiFiBluetooth, ZigBee, WiFi & Cellular Author S.Satish Babu RF& Digital Wireless Systems Architect@Satish Sura
  152. 152. Discussion Points wireless network technology options Concept of ISM frequency band Comparison between different wireless technologies (PHY and MAC layers) BluetoothBluetooth ZigBee WiFi WiMAX LTE @Satish Sura
  153. 153. wireless network technology Trends Network definition Standard Given Name Wireless personal area network (WPAN) IEEE 802.15.1 Bluetooth Low-rate WPAN (LRWPAN) IEEE 802.15.4 ZigBee Wireless local area network (WLAN) IEEE 802.11 WiFi Wireless metropolitan area network (WMAN) IEEE 802.16 WiMAX Long Term Evolution (LTE) IMT- Advanced /3GPP LTE Advanced @Satish Sura
  154. 154. ISM frequency bands ISM (Industrial, Scientific and Medical) frequency bands: • 900 MHz band (902 … 928 MHz) • 2.4 GHz band (2.4 … 2.4835 GHz) • 5.8 GHz band (5.725 … 5.850 GHz) • 60 GHz band• 60 GHz band • … Anyone is allowed to use radio equipment for transmitting in these bands (provided specific transmission power limits are not exceeded) without obtaining a license. @Satish Sura
  155. 155. ISM frequency band at 2.4 GHz The ISM band at 2.4 GHz can be used by as long as: Transmitters using FH (Frequency Hopping) technology: Total transmission power < 100 mW Power density < 100 mW / 100 kHzPower density < 100 mW / 100 kHz Transmitters using DSSS technology: Total transmission power < 100 mW Power density < 10 mW / 1 MHz @Satish Sura
  156. 156. Multiplexing / Multiple Access / Duplexing Multiplexing / multiple access Signals to/from different users share a common channel using time division methods (TDMA), frequency division methods (FDMA), code division methods (CDMA), or randommethods (FDMA), code division methods (CDMA), or random access methods (CSMA). Duplexing: The signals moving between two elements in opposite directions can be separated using time division duplexing (TDD) or frequency division duplexing (FDD). In the case of CSMA, duplexing is not relevant. @Satish Sura
  157. 157. Wireless Personal Area Network (WPAN) » 10m ISM band: 2.4 … 2.4835 GHz Bluetooth Special Interest Group (SIG) @Satish Sura
  158. 158. Low-rate WPAN (LR-WPAN) » 10m ISM band: 2.4 … 2.4835 GHz ZigBee Alliance @Satish Sura
  159. 159. Wireless Fidelity (WiFi) » 100m The WiFi certification program of the Wireless Ethernet Compatibility Alliance (WECA) addresses compatibility of IEEE 802.11 equipment WiFi ensures interoperability of equipment from different vendors. @Satish Sura
  160. 160. Wireless Metropolitan Area Network (WMAN) » 5km Various frequency bands WiMAX, LTE-Advanced @Satish Sura
  161. 161. Maximum Channel Data Rates Network Maximum data rate IEEE 802.15.1 WPAN (Bluetooth) 1 Mbit/s (Bluetooth v. 1.2) 24 Mbit/s (Bluetooth v. 4.0 for IoT) IEEE 802.15.4 LRWPAN (ZigBee) 250 kbit/s (ZigBee) IEEE 802.11 WLAN 11 Mbit/s (802.11b) Test IEEE 802.11 WLAN (WiFi) 11 Mbit/s (802.11b) 54 Mbit/s (802.11g) 1 Gpbs (802.11ac/n) IEEE 802.16 WMAN (WiMAX) 134 Mbps (WiMAX) LTE-Advanced DL 3 Gbps, UL 1.5 Gbps; 30 bps/Hz spectral efficiency @Satish Sura
  162. 162. Modulation/Signal Spreading Test Network Modulation / spreading method IEEE 802.15.1 WPAN (Bluetooth) Gaussian FSK / FHSS IEEE 802.15.4 LRWPAN (ZigBee) Offset-QPSK / DSSS IEEE 802.11 WLAN DQPSK / DSSS (802.11b) Test IEEE 802.11 WLAN (WiFi) DQPSK / DSSS (802.11b) 64-QAM / OFDM (802.11g) IEEE 802.16 WMAN (WiMAX) 128-QAM / single carrier 64-QAM / OFDM LTE-Advanced 64QAM / single carrier 64QAM / OFDM @Satish Sura
  163. 163. BLUETOOTHBLUETOOTH @Satish Sura
  164. 164. IEEE definition of WPAN Wireless personal area networks (WPANs) are used to convey information over short distances among a private, intimate group of participant devices. Unlike a wireless local area network (WLAN), aUnlike a wireless local area network (WLAN), a connection made through a WPAN involves little or no infrastructure or direct connectivity to the world outside the link. This allows small, power-efficient, inexpensive solutions to be implemented for a wide range of devices. @Satish Sura
  165. 165. Bluetooth L IEEE 802.15.1 A widely used WPAN technology is known as Bluetooth (version 1.2 - version 4.0) The IEEE 802.15.1 standard specifies the architecture and operation of Bluetooth devices, but only as far asand operation of Bluetooth devices, but only as far as physical layer and medium access control (MAC) layer operation is concerned (the core system architecture). Higher protocol layers and applications defined in usage profiles are standardised by the Bluetooth SIG. @Satish Sura
  166. 166. Piconets Bluetooth enabled electronic devices connect and communicate wirelessly through short-range, ad-hoc networks known as piconets. Up to 8 devices in one piconet (1 master and 7 slave devices). Max range 10 m. networks known as piconets. Piconets are established dynamically and automatically as Bluetooth enabled devices enter and leave radio proximity. ad hoc => no base station @Satish Sura
  167. 167. Piconet operation The piconet master is a device in a piconet whose clock and device address are used to define the piconet physical channel characteristics. All other devices in the piconet are called piconet slaves. At any given time, data can be transferred between theAt any given time, data can be transferred between the master and one slave. The master switches rapidly from slave to slave in a round-robin fashion. Any device may switch the master/slave role at any time. @Satish Sura
  168. 168. Bluetooth radio and baseband parameters Topology Up to 7 simultaneous links Modulation Gaussian filtered FSK RF bandwidth 220 kHz (-3 dB), 1 MHz (-20 dB) RF band 2.4 GHz ISM frequency band RF carriers 79 (23 as reduced option) Carrier spacing 1 MHz Access method FHSS-TDD-TDMA Freq. hop rate 1600 hops/s @Satish Sura
  169. 169. Frequency hopping in action (1) Bluetooth technology operates in the 2.4 GHz ISM band, using a spread spectrum, frequency hopping, full-duplex signal at a nominal rate of 1600 hops/second. @Satish Sura
  170. 170. Frequency hopping spread spectrum (2) The adaptive frequency hopping (AFH) feature (from Bluetooth version 1.2 onward) is designed to reduce interference between wireless technologies sharing the 2.4 GHz spectrum. @Satish Sura
  171. 171. Frequency hopping spread spectrum (3) In addition to avoiding microwave oven interference, the adaptive frequency hopping (AFH) feature can also avoid interference from WLAN networks: @Satish Sura
  172. 172. Frequency hopping in action The piconet master decides on the frequency hopping sequence. All slaves must synchronize to this sequence. Then transmission can take place on a TDD-TDMA basis. @Satish Sura
  173. 173. Link delivery services Two types of links can be established between the piconet master and one or more slaves: Synchronous connection-oriented (SCO) link allocates a fixed bandwidth for a point-to-point connection involving the piconet master and a slave. Up to three simultaneous SCOpiconet master and a slave. Up to three simultaneous SCO links are supported in a piconet. Asynchronous connectionless or connection-oriented (ACL) link is a point-to-multipoint link between the master and all the slaves in the piconet. Only a single ACL link can exist in the piconet. @Satish Sura
  174. 174. Bluetooth core system architecture @Satish Sura
  175. 175. ZigbeeZigbee @Satish Sura
  176. 176. IEEE 802.15.4 LR-WPAN (ZigBee) ZigBee technology is simpler (and less expensive) than Bluetooth. The main objectives of an LR-WPAN like ZigBee are ease of installation, reliable data transfer, short-range operation, extremely low cost, and a reasonable battery life, whileextremely low cost, and a reasonable battery life, while maintaining a simple and flexible protocol. The raw data rate will be high enough (maximum of 250 kbit/s) to satisfy a set of simple needs such as interactive toys, but is also scalable down to the needs of sensor and automation needs (20 kbit/s or below) using wireless communications. @Satish Sura
  177. 177. LR-WPAN device types Two different device types can participate in an LR-WPAN network: Full-function devices (FFD) can operate in three modes serving as a personal area network (PAN) coordinator, a coordinator, or a device.coordinator, or a device. Reduced-function devices (RFD) are intended for applications that are extremely simple. An FFD can talk to RFDs or other FFDs, while an RFD can talk only to an FFD. @Satish Sura
  178. 178. Star topology In a star network, after an FFD is activated for the first time, it may establish its own network and become the PAN coordinator. The PAN coordinator can allow other devices to join its network. @Satish Sura
  179. 179. Peer-To-Peer Topology In a peer-to-peer network, each FFD is capable of communicating with any other FFD within its radio sphere of influence. One FFD will be nominated as the PAN coordinator. A peer-to-peer network can be ad-hoc, self-organizing and self-healing, and can combine devices using a mesh networking topology. @Satish Sura
  180. 180. ZigBee PHY and MAC parameters @Satish Sura
  181. 181. Antenna Design BasicsAntenna Design Basics @Satish Sura
  182. 182. Definition An antenna is basically a conductor exposed in space. If the length of the conductor is a certain ratio or multiple of the wavelength of the signal, it becomes an antenna. This condition is called “resonance”, as the electrical energy fed to antenna is radiated into free space.antenna is radiated into free space. @Satish Sura
  183. 183. Dipole Antenna The conductor has a length λ /2, where λ is the wave length of the electric signal. The signal generator feeds the antenna at its center point by a transmission line known as “antenna feed”. At this length, the voltage andfeed”. At this length, the voltage and current standing waves are formed across the length of the conductor The antenna geometry has two most important considerations: 1. Antenna length 2. Antenna feed @Satish Sura
  184. 184. Quarter-Wave / Monopole Antenna For a quarter-wave antenna that is used in most PCBs, the important considerations are: 1. Antenna length 2. Antenna feed 3. Shape and size of the ground plane and the return pathand the return path By having a ground at some distance below the conductor, an image is created of the same length (λ /4). The signal is fed single-ended. The ground plane acts as the return path. @Satish Sura
  185. 185. Antenna Wavelength Calculation @Satish Sura
  186. 186. Return Loss The power ratio of the reflected to the incident wave is called Return Loss S11 is the negative of return loss expressed in decibels @Satish Sura
  187. 187. Bandwidth Bandwidth indicates the frequency response of an antenna. Bandwidth signifies how well the antenna is matched to the 50-Ω transmission line over the entire band of interest. If the return loss is infinite, the antenna is said to be perfectly matchedmatched As a rule of thumb, a return loss ≥ 10 dB (equivalently, S11 ≤ –10 dB) is considered sufficient. @Satish Sura
  188. 188. Radiation efficiency A portion of the non-reflected power gets dissipated as heat or as thermal loss in the antenna. Thermal loss is due to the dielectric loss in the FR4 substrate and the conductor loss in the copper trace. This information is characterized as radiation efficiency.information is characterized as radiation efficiency. A radiation efficiency of 100 percent indicates that all non-reflected power is radiated to free space. @Satish Sura
  189. 189. Radiation pattern Radiation pattern indicates the directional property of radiation, that is, which directions have more radiation and which have less @Satish Sura
  190. 190. Antenna Design An Isotropic Antenna is a theoretical antenna that radiates a signal equally in all directions. A Dipole Antenna is commonly used in wireless systems and can be modeled similarly to a doughnut Power measurements are referenced to isotropic antenna in dBi The Dipole represents a directional antenna with a further reach in the X&Y Plane (at the cost of a smaller reach in the Z plane) to the Isotropic. @Satish Sura
  191. 191. Antenna Design - Types Single-ended antenna connection Usually matched to 50 ohm Requires a balun if the TRx-chip has a differential output Easy to measure the impedance with a network analyzer Easy to achieve high performance Differential antenna connectionDifferential antenna connection Can be matched directly to the impedance at the RF pins Can be used to reduce the number of external components Complicated to make good design, might need to use a simulation Difficult to measure the impedance Possible to achieve equivalent performance of single-ended @Satish Sura
  192. 192. Typical Single & Differential Ended Antennas @Satish Sura
  193. 193. Antenna Design - Types PCB antennas No extra cost development Requires more board area Size impacts at low frequencies and certain applications Good to high range Requires skilled resources and softwareRequires skilled resources and software Whip antennas Cost from (starting~ $1) Best for matching theoretical range Size not limiting application Chip antennas Less expensive (below $1) Lower range @Satish Sura
  194. 194. Solution – Antenna Design Antennas Affect: TRP (Total Radiated Power) – radiation efficiency and tuning TIS (Total Isotropic Sensitivity) – radiation efficiency, antenna placement (noise pickup) RSIC (Receiver Sensitivity Intermediate Channels) – if passing TIS, then RSIC failures are spurious emissions problemthen RSIC failures are spurious emissions problem RSE (Radiated Spurious Emissions) – antenna cable routing, antenna placement Conti ..@Satish Sura
  195. 195. Solution – Antenna Design Best Practices: Antennas must be designed into product before mechanical/industrial design is locked down: space is key As antenna size decreases, efficiency decreases – allocate space Nearly everything in today’s small IoT devices is part of the antenna system. Metal and other materials will detune an antenna, affect pattern, degrade efficiency, or couple and radiate Keep antenna away from metal such as PCB, display, cables, enclosureKeep antenna away from metal such as PCB, display, cables, enclosure Conti..@Satish Sura
  196. 196. Solution – Antenna Design Best Practices: Keep antennas away from noise sources – switching regulators, microprocessors (causes receiver de-sense) Keep antenna and RF transmissions away from power nets Tune antenna in final configuration Tune antenna to favor transmit frequencies instead of receiveTune antenna to favor transmit frequencies instead of receive Maintain evaluation board-size ground plane when using ceramic surface mount antennas. @Satish Sura
  197. 197. Solution – Off the Shelf Antennas Lower NRE, higher unit cost Fastest development route Can perform well with right ground plane and system design Datasheets only accurate for one very specific ground plane arrangement Cabled antennas can create EMI issues – coax shields often pick up and radiate spurious emissions, harmonics, or broadband noise. Bestand radiate spurious emissions, harmonics, or broadband noise. Best with clean, straight, cable routings @Satish Sura
  198. 198. Solution – Custom Antennas Break-even point can start as low as 10ku/yr, depending on OTS antenna price, antenna complexity Necessary to achieve performance in some enclosures and systems Cellular handset and tablet PC antennas are usually custom Allow for simulation not possible with off-the-shelf antennas, especially helpful for ECCespecially helpful for ECC @Satish Sura
  199. 199. Solution – Custom Antennas Lower frequency increases the antenna range Reducing the frequency by a factor of two doubles the range Lower frequency requires a larger antenna λ/4 at 433 MHz is 17.3 cm (6.81 in) λ/4 at 915 MHz is 8.2 cm (3.23 in) λ/4 at 2.4 GHz is 3.1 cm (1.22 in) Frequency vs. Size λ/4 at 2.4 GHz is 3.1 cm (1.22 in) A meandered structure can be used to reduce the size λ/4 at 2.4 GHz @Satish Sura
  200. 200. Solution – Inverted-F Antenna The F-antenna can be thought of as a tilted whip, where impedance matching is accomplished by tapping the antenna at the appropriate impedance point along its width. This antenna is used extensively because it is reasonably compact. Fairly Omni-directional radiation pattern, good efficiency, and is very simplesimple @Satish Sura
  201. 201. Solution – Custom Antennas The meander antenna or meander pattern, is an antenna with the wire folded back and forth where resonance is found in a much more compact structure Meander Antenna @Satish Sura
  202. 202. Antenna Design: Do’s and Don’ts Never place ground plane or tracks underneath the antenna Never place the antenna very close to metallic objects In the final product, ensure that the wiring and components do not get too close to the antenna A monopole antenna will need a reasonable ground plane area to be efficient Do the final tuning in the end product enclosure, not in open air Never install a chip antenna in a vastly different layout than the reference design and expect it to work without tuningdesign and expect it to work without tuning Do not use a metallic enclosure or metalized plastic for the antenna Test the plastic casing for high RF losses, preferably before production Never use low-Q loading components, or change manufacturer without retesting Do not use very narrow PCB tracks. The tracks should be relatively wide as space allows @Satish Sura
  203. 203. Antenna Design Tools EM Simulation Momentum Agilent http://eesof.tm.agilent.com/products/momentum_ma in.html HFSS Ansoft http://www.ansoft.com/products/hf/hfss/ IE3D Zeland http://www.zeland.com/ @Satish Sura
  204. 204. Thank YouThank You @Satish Sura

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