2. Microwave Engineering
1. Microwave Systems
Transmission
Information
- Channel bandwidth
- Base band
- Inefficient wave radiation
Modulation – center frequency
출처: RFDH.com
Time domain Frequency domain
2 전자파연구실
3. Microwave Engineering
1. Microwave Systems
Why’s modulation need?
Transmission efficiency
- Multiplexing
- Antenna length: wavelength
- Wave radiation: comparison with DC
Battery: DC
Antenna: AC
3 전자파연구실
5. Microwave Engineering
1. Microwave Systems
Friis power transmission formula
Pt
Power density: S 2
Gt W / m 2
4 R
Antenna gain: anisotropic radiation (G > 1)
isotropic radiation (G = 1)
Radiation pattern [dBi]: dB isotropic
5 전자파연구실
6. Microwave Engineering
1. Microwave Systems
Friis power transmission formula
Received power: Pr SAe
Effective area
2
Gr
- Ae
4
2
Pr
Gt Gr W
Pt 4 R
Friis transmission formula
6 전자파연구실
7. Microwave Engineering
1. Microwave Systems
Microwave transmitter (Tx)
Up-conversion: frequency
f BB f LO f BB f LO f BB
출처: RFDH.com
1
cos(x) cos(y)
2
cos(x y ) cos(x y)
7 전자파연구실
8. Microwave Engineering
1. Microwave Systems
Microwave receiver (Rx)
Down-conversion: frequency
출처: RFDH.com
f f LO f IF f f IF
f LO f BB f IF f BB f BB
1
cos(x) cos(y)
2
cos(x y ) cos(x y)
8 전자파연구실
9. Microwave Engineering
1. Microwave Systems
Microwave transceiver
Duplexer: bandpass filter or switch
- Loss, tx suppression, channel selection
출처: RFDH.com
IF: superheterodyne
No IF: direct conversion
9 전자파연구실
10. Microwave Engineering
1. Microwave Systems
Uplink and downlink
Pt 10[ W ]
R 40,000[km] fd 12[GHz ]
θ3dB 2
0.55
Pt 100[ W ]
fu 14[GHz ]
4m diameter dish
0.6
10 전자파연구실
11. Microwave Engineering
1. Microwave Systems
Uplink calculation
4
Dr
Pr EIRP LFS Gr [dB] 1 2
Gr Dr
EIRP Pt Gt
4 2
Dt Ae 4 R
2 LFS
Gt Dt
11 전자파연구실
12. Microwave Engineering
1. Microwave Systems
Downlink calculation
EIRP Pt Gt
Pr EIRP LFS Gr [dB] 4
Dt
1 2
Gt Dt
Dr
4
Am ax 2
2 4 R
LFS
Gr Dr
12 전자파연구실
13. Microwave Engineering
1. Microwave Systems
Thermal Noise or Johnson Noise
Thermal noise: white noise, Nyquist formula
Pn kTB N
T
N N0 B kB
Noise power
Noise temperature
13 전자파연구실
14. Microwave Engineering
1. Microwave Systems
Carrier to noise ratio
C/No: related to carrier to noise ratio
G/T: Figure of merit
Carrier to noise ratio
C C C
N N0 B TkB
G/T: sensitivity of receiver
C EIRP LFS Gr [dB]
14 전자파연구실
16. Microwave Engineering
1. Microwave Systems
FDMA (FDM Access)
Resource: frequency
Guard band
Simple transceiver
Interference
16 전자파연구실
17. Microwave Engineering
1. Microwave Systems
TDMA (TDM Access)
Resource:
time
Guard time
Complicated
transceiver
GSM: Global System for Mobile commo
17 전자파연구실
18. Microwave Engineering
1. Microwave Systems
FH(Frequency Hopping)-CDMA
Resource: code
Precise clock
Very complicated transceiver
Bluetooth, military applications
18 전자파연구실