UM9401_09 Datasheet, PDF (7/7 Pages) Microsemi Corporation – COMMERCIAL TWO WAY RADIO ANTENNA SWITCH DIODES

®
TM
Maximum Transmitter Power
The maximum CW transmitter power, P_T(max), a PIN diode
antenna switch can handle depends on the diode
resistance, R_S, power dissipation, P_D, antennae SWR, σ,
and the nominal impedance, Z_O. The expression is as
follows:
P_{T (MAX )}

P_D xZ_O
R_D



2
1
²

[Watts]
Characteristic curves are shown in the data section
which gives both the maximum and typical diode
resistance, R_S 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 (T_L) 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
UM9401 / UM9402 / UM9415
COMMERCIAL TWO WAY RADIO
ANTENNA SWITCH DIODES
RoHS Compliant Versions Available
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.
DC SUPPLY
TRANSMITTER
ANTENNA
D1
/4
DC SUPPLY
TRANSMITTER
ANTENNA
D1
L
D2 ^RECEIVER
D2 _RECEIVER
L = Z_O / 2 f_O (H)
C = 1/2 f_O Z_O (F)
L
C
C
Copyright  2007
Rev: 2009-02-05
Microsemi
Microwave Products
75 Technology Drive, Lowell, MA. 01851, 978-442-5600, Fax: [phone]
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