Power Dividers and Directional Couplers

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# Power Dividers and Directional Couplers - PowerPoint PPT Presentation

Power Dividers and Directional Couplers. Divider or coupler. Divider or coupler. Power combining. Power division . Four-Port Network (Directional Couplers). Assume all ports are matched. 1. 2. Input. Through or direct. Isolated. Coupled. 4. 3. Directional Coupler.

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Presentation Transcript
Power Dividers and Directional Couplers

Divider or

coupler

Divider or

coupler

Power combining

Power division

Four-Port Network (Directional Couplers)

Assume all ports are matched

1

2

Input

Through or

direct

Isolated

Coupled

4

3

Directional Coupler

-2bL

-bL

-bL

0

Kf a1

Kf a1

Kb a1

Kf a1

Directional Couplers

Two-hole Waveguide Couplers

Pf

Pb

Port 3

b4

Port 4

b3

L

b2

Port 1

a1

0

a1

-bL

Port 2

Pi

Pt

Kf and Kr

are the forward

and reverse aperture coupling coeffiecients

Multi-element Couplers

To achieve good directivity over a band of frequencies, couplers

With many apertures may be used.

Coupled

Isolated

B1

A

B0

A

F1

A

Bb

F0

A

Bf

Input

n=1

n=0

A

Through

d

Cn

Let the aperture coupling in the forward direction be

And the reverse coupling in the reverse direction be

Dn

Chebyshev Response

In order to obtain an equal-ripple characteristics in the pass band

The array factor F is made proportional to Chebyshev polynomial.

Branch-Line Coupler

Z02

Z0

Z0

b2

Port 1

Port 2

Even-mode

pair

Odd-mode

pair

l

b1

Z01

l

Z01

a1/2

a1/2

a1/2

Port 3

-a1/2

Port 4

Z0

Z02

Z0

b3

b4

Short circuits

Open circuits

Even-mode excitation

Odd-mode excitation

Parallel-Coupled Lines Directional Coupler

L

Direct Port 2

Input

Port 1

Isolated Port 4

Coupled Port 3

a1/2

L

Direct Port 2

Input

Port 1

H wall

a1/2

Isolated Port 4

Coupled Port 3

Even Mode excitation

Z0

I3

Z0

I4

3

4

Z0e

Z0o

I2

I1

2

Z0

1

Z0

V

Even

Odd

Vb+

1/2

1/2

Microstrip Hybrid Ring

Even

Odd

a

3

2

Vb+

1/2

-1/2

l/4

or -Vb+

l/4

l/4

Va+

1

4

Va+

or -Va+

Zc

Z1

3l/4

a

The hybrid ring (rat-race)

Ports 1 and 3 are uncoupled, ports 2 and 4 are uncoupled

q1

Vb+

Va+

jB2

jB1

Y1

Yc

Yc

Equivalent circuit for

one half of Hybrid ring

Port 2

Port 2

l/4

l/4

1/2

1/2

2

1

2

1

Port 1

Port 1

To

Te

Ge

Go

l/8

l/8

3l/8

3l/8

O.C

S.C

Even Mode

Odd Mode

O.C

S.C

P2

Z2

P1

Z1

Z3

P3

Power Dividers

A lossless three port juntion

R

l/4

Z2

Zc

ZL2

Z3

ZL3

G

z3

z2

I3

-Y23

I3

I2

Yc

sc

V2

V2

V3

-Y33+Y23

-Y22+Y23

Y3

Y2

,q

,q

Equivalent circuit between

Port 2&3 with port 3 sc and

R removed

Equivalent circuit with port

2 and 3 excited

Passive Microwave Devices

Attenuators

R1

R1

R2

Zc

Zc

R1

R1

R2

Vg

T section

p section

OC

l/4

Bias Current Input

l/4

input

output

l1

l/4

l/4

Length l2

Bias

Circuit

Ground

Bias

Circuit

Ground

l/4

Bias Current Input

l/4

oc

Incremental-line-type phase shifter

Phase shifters

Bl=q

V+1

V+2

V+3

V+4

V-1

V-2

V-3

V-4

l/4

Bias

Current

Input

jB

jB

l/4

OC

A phase shifter using switched reactive elements

Transmission matrix of a normalized shunt suceptance jB:

Transmission matrix of a section of transmission line of

Electrical length q:

Relationship among wave amplitudes:

Choose V-4 = 0, then V+4 = V+1 /A11Thus T14 = 1/ A11

If tanq = 2/Bthen :

l/4

d1

P’

P

d

A phase shifter using open circuited stubs spaced l/4

Apart. P and P’ are switched into the circuit when the

Diodes are off and on, respectively.