UM9401 / UM9402 / UM9415

Microsemi

Microwave Products

Page

7

TM

®

Copyright

 2007

Rev: 2009-02-05

COMMERCIAL TWO WAY RADIO

ANTENNA SWITCH DIODES

RoHS Compliant Versions Available

Maximum Transmitter Power

antenna switch can handle depends on the diode

follows:

2

)

(

2

1









 







D

O

D

MAX

T

R

xZ

P

P

[Watts]

Characteristic curves are shown in the data section

which gives both the maximum and typical diode

maximum power dissipation rating of the PIN diode

depends both on the length of the diode leads and the

temperature of the contacts to which the leads are

connected. A graph defining the maximum power

dissipation at various combinations of overall lead length

From these curves and the above equation, the power

handling capability of the PIN diode may be computed for

a specific application.

Curves are also presented which show the maximum

transmitter power that an antenna

switch using UM9401s and UM9415s can safely handle

for various forward currents and lead temperatures.

These curves are based on a typical design condition of a

½ in. total overall lead length, 50 Ω line impedance, and a

totally mismatched antenna (σ = ∞). For the case of a

perfectly matched antenna, the maximum transmitter

power can be increased by a factor of 4.

Design Information

A circuit configuration for a two-way radio antenna

switch using PIN diodes consists of a diode placed in

series with the transmitter and a shunt diode placed a

quarter wavelength from the antenna in the direction of

the receiver as shown. For low frequency operation, the

quarter wave line may be simulated by lumped elements.

Typical performance of antenna

switches using PIN diodes forward biased at 100 mA is

less than 0.2 dB insertion loss and 30 dB isolation during

transmit; at zero bias the receive insertion loss is less

than 0.3 dB. This performance is achievable across a ±20

% bandwidth at center frequencies ranging from 10 to 500

MHz.

ANTENNA

ANTENNA

DC SUPPLY

D1

D2

L

D1

D2

DC SUPPLY

/4

TRANSMITTER

TRANSMITTER

RECEIVER

RECEIVER

(H)

C = 1/2

L

CC