Microwave Systems

Microwave Systems

Microwave EngineeringCHO, Yong Heui

Microwave Engineering

전자파연구실2

1. Microwave Systems

Transmission

Information

- Channel bandwidth

- Base band

- Inefficient wave radiation

Modulation – center frequency

Time domain Frequency domain

출처: RFDH.com


전자파연구실3

Why’s modulation need?

Transmission efficiency

- Multiplexing

- Antenna length: wavelength

- Wave radiation: comparison with DC

Battery: DCAntenna: AC



전자파연구실4

Friis power transmission formula

Microwave radio link

R

tP rP



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Power density:

Antenna gain: anisotropic radiation (G > 1)

isotropic radiation (G = 1)

Radiation pattern [dBi]: dB isotropic

2

2/

4mWG

R

PS t

t



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Received power:

Effective area

-

er SAP

4

2

re

GA

WR

GGP

Prt

t

r

2

4

Friis transmission formula



전자파연구실7

Microwave transmitter (Tx)

Up-conversion: frequency

)cos()cos(2

1)cos()cos( yxyxyx

BBf BBLO ff BBLO ff


출처: RFDH.com


전자파연구실8

Microwave receiver (Rx)

Down-conversion: frequency

)cos()cos(2

1)cos()cos( yxyxyx

BBfBBIF ffBBLO ff

IFLO fff IFff


출처: RFDH.com


전자파연구실9

Microwave transceiver

Duplexer: bandpass filter or switch

- Loss, tx suppression, channel selection

IF: superheterodyneNo IF: direct conversion


출처: RFDH.com


전자파연구실10

0.6

dishdiameter 4

]GHz[14

]W[100

m

f

P

u

t

0.55

2

]GHz[12

]W[10

3dB

θ

f

P

d

t

Uplink and downlink

][000,40 kmR




tt

et

tt

DG

AD

GP

2

4

EIRP

Uplink calculation

rr

r

DG

D21

4

2

FS

4 RL

]dB[EIRP FS rr GLP




rr

r

DG

AD max2

4

Downlink calculation

tt

t

tt

DG

D

GP

21

4

EIRP

2

FS

4 RL

]dB[EIRP FS rr GLP




Noise power

Thermal noise: white noise, Nyquist formula

Thermal Noise or Johnson Noise

BNN

kTBPn

0

Noise temperature

kB

NT




Carrier to noise ratio

TkB

C

BN

C

N

C

0

C/No: related to carrier to noise ratio

G/T: Figure of merit

Carrier to noise ratio

]dB[EIRP FS rGLC

G/T: sensitivity of receiver




Multiplexing: resources

FDM (Frequency Division Multiplexing)

TDM (Time Division Multiplexing)

CDM (Code Division Multiplexing)


Communication



FDMA (FDM Access)


Resource: frequency

Guard band

Simple transceiver

Interference




TDMA (TDM Access)

Resource:

time

Guard time

Complicated

transceiver

GSM: Global System for Mobile commo



FH(Frequency Hopping)-CDMA


Resource: code

Precise clock

Very complicated transceiver

Bluetooth, military applications



DS(Direct Sequence)-CDMA


QPSK: Quadrature Phase Shift Keying



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

2. Applications



Attenuation

2. Applications

Attenuation by water and oxygen

HF application



ELF application

Skin depth: long wavelength

Long antenna: 104km at USA

Unidirectional communication

Slow bit rate: redundancy

Information: code table

12

2. Applications



EHF application

Short antenna

Absorption: air, water(60 GHz)

Anti-collision radar: 76 GHz

ITS: Intelligent Transport System

Radar ITS

2. Applications

Technology

Microwave Systems