3. Data Forms
Data (Information) can be analog or digital. The term analog data
refers to information that is continuous; digital data refers to
information that has discrete states. Analog data take on
continuous values. Digital data take on discrete values.
In communication systems, we commonly use periodic analog signals
and non-periodic digital signals
6. Signal Parameters
Frequency (F): is the rate of change with respect to time.
Change in a short span of time, means high frequency.
Change over a long span of time means low frequency.
10. Modulation, Why?
Frequency Assignment
Reduction of noise/interference
Multiplexing
Bandwidth limitations of equipment
Frequency characteristics of antennas
Atmospheric/cable properties
11. Modulation
Analogue modulation:
A higher frequency signal is generated by varying some characteristic of a high
frequency signal (carrier) on a continuous basis.
Amplitude Modulation (AM), Frequency Modulation (FM), Phase Modulation
(PM)
Digital modulation:
Signals are converted to binary data, encoded, and translated to higher frequency.
Frequency Shift Keying (FSK), Binary Phase Shift Keying (BPSK) [ (GMSK)],
Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation
(QAM)
16. Comparisons of Digital and Analog
Communication Systems
Digital Communication System Analog Communication System
Advantage : Disadvantages :
inexpensive digital circuits
privacy preserved (data encryption) expensive analog components : L&C
can merge different data (voice, video and data) no privacy
and transmit over a common digital can not merge data from diff. sources
transmission system no error correction capability
error correction by coding
Disadvantages : Advantages :
larger bandwidth smaller bandwidth
synchronization problem is relatively difficult synchronization problem is relatively easier
19. Manchester Encoding
It is a form of binary phase-shift keying (BPSK) that has
gained wide acceptance as the modulation scheme for low-
cost radio-frequency (RF) transmission of digital data.
Manchester is a simple method for encoding digital serial
data of arbitrary bit patterns without having any long strings
of continuous zeros or ones, and having the encoding clock
rate embedded within the transmitted data.
These two characteristics enable low-cost data-recovery
circuits to be constructed that can decode transmitted data
with variable signal strengths from transmitters with
imprecise, low-cost, data-rate clocks.
22. Specifications
Range in open space(Standard Conditions) : 100 Meters
RX Receiver Frequency : 433 MHz
RX Typical Sensitivity : 105 dBm
RX Supply Current : 3.5 mA
RX IF Frequency : 1MHz
Low Power Consumption
Easy For Application
RX Operating Voltage : 5V
TX Frequency Range : 433.92 MHz
TX Supply Voltage : 3V ~ 6V
TX Out Put Power : 4 ~ 12 Dbm
25. HT12D Decoder
Features:
Operating voltage: 2.4V~12V
Low power and high noise immunity CMOS technology
Low standby current
Capable of decoding 12 bits of information
Binary address setting
Received codes are checked 3 times
Address/Data number combination
8 address bits and 4 data bits
26. HT12E Encoder
Features:
Operating voltage 2.4V~12V
Low power and high noise immunity CMOS technology
Low standby current: 0.1A (typ.) at VDD=5V
Four words
Built-in oscillator needs only 5% resistor
Data code has positive polarity
28. CIP – 8bits Decoder/Encoder
Features:
Latched or momentary outputs
No programming necessary
Very easy to use
Very low component count
Low current consumption
Up to 25mA per decoder output
Eight bit data (D0 to D7)
Eight bit binary address (0 to 255)
Selectable baud rates (2400/4800)
High noise immunity
Standard 20-pin PDIP package