1. Microwave
Systems
Microwave Engineering
CHO, Yong Heui

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
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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

4. Microwave Engineering
1. Microwave Systems
Friis power transmission formula
  Microwave radio link
R
Pt Pr
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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
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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)
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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)
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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
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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
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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
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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
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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]
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15. Microwave Engineering
1. Microwave Systems
Multiplexing: resources
  FDM (Frequency Division Multiplexing)
 TDM (Time Division Multiplexing)
 CDM (Code Division Multiplexing)
Communication
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16. Microwave Engineering
1. Microwave Systems
FDMA (FDM Access)
  Resource: frequency
 Guard band
 Simple transceiver
 Interference
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17. Microwave Engineering
1. Microwave Systems
TDMA (TDM Access)
  Resource:
time
 Guard time
 Complicated
transceiver
GSM: Global System for Mobile commo
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18. Microwave Engineering
1. Microwave Systems
FH(Frequency Hopping)-CDMA
  Resource: code
 Precise clock
 Very complicated transceiver
 Bluetooth, military applications
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19. Microwave Engineering
1. Microwave Systems
DS(Direct Sequence)-CDMA
QPSK: Quadrature Phase Shift Keying
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20. Microwave Engineering
2. Applications
Frequency spectrum
 Name Frequency[Hz] Wavelength Application
EHF 30G-300G 1cm-1mm Car radar
SHF 3G-30G 10cm-1cm Radar, satellite
UHF 300M-3G 1m-10cm TV, PCS, IMT2000
VHF 30M-300M 10m-1m FM, TV
HF 3M-30M 100m-10m Shortwave AM, HAM
MF 300k-3M 1km-100m AM
LF 30k-300k 10km-1km Navigation
VLF 3k-30k 100km-10km Submarine, navigation
ELF 30-300 10000km-1000km Submarine
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21. Microwave Engineering
2. Applications
Attenuation
 HF application
 Attenuation by water and oxygen
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22. Microwave Engineering
2. Applications
ELF application
  Skin depth: long wavelength
 Long antenna: 104km at USA
 Unidirectional communication
 Slow bit rate: redundancy
 Information: code table
2 1
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23. Microwave Engineering
2. Applications
EHF application
  Short antenna
 Absorption: air, water(60 GHz)
 Anti-collision radar: 76 GHz
 ITS: Intelligent Transport System
Radar ITS
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