Microwave Systems

Microwave Engineering CHO, Yong Heui

Microwave Engineering

EM Wave Lab 2

1. Microwave Systems

Transmission

Information

- Channel bandwidth

- Base band

- Inefficient wave radiation

Modulation – center frequency

Time domain Frequency domain

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Microwave Engineering

EM Wave Lab 3

Why’s modulation need?

Transmission efficiency

- Multiplexing

- Antenna length: wavelength

- Wave radiation: comparison with DC

Battery: DC Antenna: AC

1. Microwave Systems

Microwave Engineering

EM Wave Lab 4

Friis power transmission formula

Microwave radio link

R

tP rP

1. Microwave Systems

Microwave Engineering

EM Wave Lab 5

Friis power transmission formula

Power density:

Antenna gain: anisotropic radiation (G > 1)

isotropic radiation (G = 1)

Radiation pattern [dBi]: dB isotropic

2

2/

4mWG

R

PS t

t

1. Microwave Systems

Microwave Engineering

EM Wave Lab 6

Friis power transmission formula

Received power:

Effective area

-

er SAP

4

2

re

GA

WR

GGP

Prt

t

r

2

4

Friis transmission formula

1. Microwave Systems

Microwave Engineering

EM Wave Lab 7

Microwave transmitter (Tx)

Up-conversion: frequency

)cos()cos(2

1)cos()cos( yxyxyx

BBf BBLO ff BBLO ff

1. Microwave Systems

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Microwave Engineering

EM Wave Lab 8

Microwave receiver (Rx)

Down-conversion: frequency

)cos()cos(2

1)cos()cos( yxyxyx

BBfBBIF ff BBLO ff

IFLO fff IFff

1. Microwave Systems

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Microwave Engineering

EM Wave Lab 9

Microwave transceiver

Duplexer: bandpass filter or switch

- Loss, tx suppression, channel selection

IF: superheterodyne No IF: direct conversion

1. Microwave Systems

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Microwave Engineering

EM Wave Lab 10

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

1. Microwave Systems

Microwave Engineering

EM Wave Lab 11

tt

et

tt

DG

AD

GP

2

4

EIRP

Uplink calculation

rr

r

DG

D

21

4

2

FS

4

RL

]dB[EIRP FS rr GLP

1. Microwave Systems

Microwave Engineering

EM Wave Lab 12

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

1. Microwave Systems

Microwave Engineering

EM Wave Lab 13

Noise power

Thermal noise: white noise, Nyquist formula

Thermal Noise or Johnson Noise

BNN

kTBPn

0

Noise temperature

kB

NT

1. Microwave Systems

Microwave Engineering

EM Wave Lab 14

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

1. Microwave Systems

Microwave Engineering

EM Wave Lab 15

Multiplexing: resources

FDM (Frequency Division Multiplexing)

TDM (Time Division Multiplexing)

CDM (Code Division Multiplexing)

1. Microwave Systems

Communication

Microwave Engineering

EM Wave Lab 16

FDMA (FDM Access)

1. Microwave Systems

Resource: frequency

Guard band

Simple transceiver

Interference

Microwave Engineering

EM Wave Lab 17

1. Microwave Systems

TDMA (TDM Access)

Resource:

time

Guard time

Complicated

transceiver

GSM: Global System for Mobile commo

Microwave Engineering

EM Wave Lab 18

FH(Frequency Hopping)-CDMA

1. Microwave Systems

Resource: code

Precise clock

Very complicated transceiver

Bluetooth, military applications

Microwave Engineering

EM Wave Lab 19

DS(Direct Sequence)-CDMA

1. Microwave Systems

QPSK: Quadrature Phase Shift Keying

Microwave Engineering

EM Wave Lab 20

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

Microwave Engineering

EM Wave Lab 21

Attenuation

2. Applications

Attenuation by water and oxygen HF application

Microwave Engineering

EM Wave Lab 22

ELF application

Skin depth: long wavelength

Long antenna: 104km at USA

Unidirectional communication

Slow bit rate: redundancy

Information: code table

12

2. Applications

Microwave Engineering

EM Wave Lab 23

EHF application

Short antenna

Absorption: air, water(60 GHz)

Anti-collision radar: 76 GHz

ITS: Intelligent Transport System

Radar ITS

2. Applications