전자파 연구실 1 duplexer design project duplexer antenna a duplexer is a three port network...

전자파 연구실

1Duplexer design projectDuplexer design project

Duplexer

antenna

A duplexer is a three port network that allows bi-directional communication over a single frequency channel which is composed of transmitting and receiving band.

frequency

transmitting receivingPower spectrum

Receiving circuit

Transmitting circuit

Introduction

One channel

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To share one antenna, the duplexer should separate the frequency spectrum into transmitting and receiving spectrum. Then, the separated bands are diverted to a transmitting network and a receiving network. To realize these functions, a duplexer which is a variant filter network should be synthesized. A simple duplexer is frequently synthesized in a parallel combination of two filters of which pass bands contain receiving frequency band and transmitting band.

A simple duplexerA simple duplexer

Duplexer

Receiving filter

Transmitting filter

ftransmitting receiving

Transfer function

ftransmitting receiving

Transfer function

전자파 연구실

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transmitting receiving

Example : PCS duplexerExample : PCS duplexer

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Design considerationDesign consideration

In a wireless system, the transmitting power level is very larger than the receiving power level. So care should be taken not to interfere the receiving power level. This consideration is taken into implementing the filter transfer function. Usually, each of the filter transfer functions (transmitting and receiving) should contain a transmission zero in the other frequency band. That is, the receiver transfer function should contain a transmission zero in the transmitting band and the transmitting network transfer function should contain a transmission zero in the receiving band.

Transmission zero

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Design assignmentDesign assignment

To design a simple duplexer filter, implement the transmitting and the receiving filters by a cascade of low pass, high pass, band pass filter or band stop filter network that covers the specified frequency band.

Receiving ortransmitting filter

LPF, HPF, BPF or BSF

LPF, HPF, BPF or BSF

Reports on this design project should include the followings :

1.A duplexer schematic circuit.2.PSpice simulation results that show the duplexer meets the design specification.3.Detailed explanations on how the values of lumped elements are determined.

전자파 연구실

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20log10|H|> -3dB 20log10|H|> -3dB

20log10|H|< -40dB20log10|H|< -40dB

SpecificationSpecification

20log10|H|< -20dB 20log10|H|< -20dB

Receiving filter

Transmitting filter

50Ω

50Ω

50Ω

in

out

V

VsH )(

outV

outV

inV


1.75GHz 1.78GHz 1.84GHz 1.87GHz1.65GHz 1.97GHz

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Example : duplexerExample : duplexer

Vi

Vo2

Vo1

VARVAR4

C4=1/(Q4*R*w4)L4=Q4*R/w4w4=2*pi*f4f4=1.8e9Q4=50

EqnVarVAR

VAR3


EqnVarVAR

VAR2


EqnVarVAR

VAR1

C1=1/(Q1*R*w0)L1=Q1*R/w0w0=2*pi*f0f0=1.8e9R=50Q1=51

EqnVar

ACAC1

Step=Stop=1.9 GHzStart=1.6 GHz

AC

V_ACSRC1

Freq=freqVac=polar(1,0) V

RR3R=50 Ohm

RR2R=50 Ohm

RR1R=50 Ohm

SLCSLC2

C=C4 FL=L4 H

SLCSLC1

C=C2 FL=L2 H

SLCSLC3

C=C3 FL=L3 H

SLCSLC4

C=C1 FL=L1 H

transmitting

receiving

Band pass filter

Band reject filter

50,1

,00

RQR

CQR

L

0Q

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1.65 1.70 1.75 1.80 1.851.60 1.90

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

-50

5

freq, GHz

dB(V

o2/V

i)dB

(Vo1

/Vi)

1.65 1.70 1.75 1.80 1.851.60 1.90

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

-50

5

freq, GHz

dB(V

o2/V

i)

1.65 1.70 1.75 1.80 1.851.60 1.90

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

-50

5

freq, GHz

dB(V

o1/V

i)

ResultResult

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Hint :Hint :

(1) To satisfy the specifications of the duplexer, adjust Q’s, center frequencies, the order of band pass or band stop filters until they are met.

(2) A filter with the order higher than 1 can be constructed from the low pass filter prototypes (see page 10). Relevant impedance, frequency, BPF, BSF, HPF transformation should be made.

전자파 연구실

1010Reference materialReference material 1,1 0 Lc RR

Value of n

g1 g2 g3 g4 g5 g6 g7

1 2.000 1.000

2 1.414 1.414 1.000

3 1.000 2.000 1.000 1.000

4 0.7654 1.848 1.848 0.7654 1.000

5 0.6180 1.618 2.000 1.618 0.618 1.000

6 0.5176 1.414 1.932 1.932 1.414 0.5176 1.000

NV

VsH

2

2

1

22

1

1)(

N-th order low pass filter proto-types :

1

N-th order Butterworth filter

or

전자파 연구실

1111Filter transformationFilter transformation1. Impedance transformation

000 1 RZZ

00

Inductor.

LRLsLRZsLZ

a

0

01

Capacitor.

R

CC

sC

RZ

sCZ

b

2. Frequency transformation

]/[frequency offcut ]/[1frequency offcut sradsrad c

cc

LLL

sZsLZ

a

Inductor.

c

c

CC

Cs

ZsC

Z

b

11

Capacitor. dB0

21S

dB3 10log

]/[1 sraddB0

21S

dB3 10log

]/[ sradC

FilterFilter

1

1

FilterFilter

0R

0R

전자파 연구실

LPF prototypes : LPF prototypes : ωωcc=1rad/s, R=1rad/s, Rss=R=RLL=1=1ΩΩ

1

H2

1

11

F1

1

1

1

1

H414.1

F414.1

H414.1

1

1

1

1F1

H1H1

F2

1st order LPF 2nd order LPF

3rd order LPF

H2

F2

F414.1

전자파 연구실 1 duplexer design project duplexer antenna a duplexer is a three port network...

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