UM9401_05 データシートの表示（PDF） - Microsemi Corporation
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UM9401_05 Datasheet PDF : 11 Pages
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UM9401 / UM9402 / UM9415
COMMERCIAL TWO-WAY RADIO
ANTENNA SWITCH DIODES
The maximum CW transmitter power, PT(max), a PIN
diode antenna switch can handle depends on the
diode resistance, RS, power dissipation, PD, antennae
SWR, σ, and the nominal impedance, ZO. The
expression is as follows:
is less than 0.3 dB. This performance is achievable
across a ±20 % bandwidth at center frequencies
ranging from 10 to 500 MHz.
Characteristic curves are shown in the data section
which gives both the maximum and typical diode
resistance, RS as a function of forward current. The
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 (L) and lead temperature (TL) is given in the
data section. 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
DC SUPPLY
TRANSMITTER
ANTENNA
D1
/4
DC SUPPLY
TRANSMITTER
ANTENNA
D1
L
D2
RECEIVER
D2
RECEIVER
L = ZO / 2 πfO (H)
C = 1/2 πfO ZO (F)
L
C
C
Copyright 2005
Rev. 0, 2005-09-15
Microsemi
Page 7
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