Three subassemblies of the rf retie

TM 11-4920-296-14&P

then fed back into the rf microstrip module,

to the transponder. During the reply inter-

val, the rf signals from the transponder are

which directs them to mixer circuits within

fed first to the rf module circuits, which

the module. Simultaneously with reception

detect (demodulate) them and produce the

of reply pulses, the local oscillator output

corresponding video signals that are then

occurs from the local al oscillator-transmitter

processed in the digital circuits. Secondary

module; this LO signal is directed through

functions of the rf module include checking

the rf microstrip module circuits to the LO

the frequency and power of the rf reply

input of its mixer. Resulting 30-MHz if.

pulses, steering output interrogation pulses

pulses from the mixer are then directed by

during testing of diversity type transponders,

the rf microstrip module circuits to the if.

video module circuits.

and checking that reply pulses are received

from the correct transponder output. Cir-

2-49. During testing of diversity type

cuits of the rf module also control the rela-

tive amplitude of side-lobe pulses, with

transponders, the test set varies the ampli-

respect to other interrogation pulses.

tudes of the rf signals transmitted from the

NORMAL and DIVERSITY jacks, so that the

2-47. The three subassemblies of the rf

strongest signal is alternately transmitted

r e t i e are: the local oscillator-transmitter

from the NORMAL and then the DIVERSITY

jack. The actual steering signals for this

module the rf microstrip module; and the

alternating strongest signal are fed to the

if. video module. The local oscillator-

t r a n s m i t t e r retie contains two electrically-

rf microstrip module from the if, video

module, If operating correctly, the trans-

identical crystal-controlled oscillator

stages, which are gated to produce the out-

ponder will feed its reply pulses back into

put interrogation pulses (transmitter) and

the jack (NORMAL or DIVERSITY) that

transmitted the strongest signal interroga-

the local oscillator (LO) signal for the

tion. The rf microstrip module processes

r e c e i v e circuits (local oscillator). Both

the reply pulses in the same manner as for

oscillator circuits use crystals whose fun-

single-channel replies, and feeds the result-

damental frequency is 1/6 that of their out-

ing 30-MHz if. pulses to the if. video mod-

put frequency, and both produce outputs

ule. By use of the steering signals, and

greater than +4 dBm. The transmitter oscil-

detected rf sample signals from the rf

lator, gated by the interrogation input from

microstrip module, the if. video module

the digital circuits, produces output rf

logic circuits confirm that each transponder

pulses at 1030 MHz. During receive (reply)

reply is received via the correct jack

times, the local oscillator is gated by the

(NORMAL or DIVERSITY). By alternately

VIDEO GATE input from the digital section,

transmitting the strongest signal between

to produce the required 1060-MHz LO signal

the NORMAL and DIVERSITY jacks, the test

to the receive mixer circuits. The rf outputs

set checks the transponder ability to reply

from both oscillators are coupled to the rf

from either of its diversity outputs, in cor-

microstrip module circuits via coaxial

rect accord with the strongest signal

cables.

reception, If correct diversity reply action

2-48. The rf microstrip module serves to

occurs, the if. video module feeds a signal

to the digital circuits, which allows the

transfer signals between itself and the other

ACCEPT indication (providing all other

assemblies of the rf module Al, and also for

parameters of the reply signal are correct).

trasferring signals to and from the trans-

ponder under test. During single-charnel

2-50. In addition to the mixer and steering

transponder testing, the coded rf interroga-

circuits, the rf microstrip module contains

tion pulses (from the local oscillator-

attenuator circuits which control the trans-

transmitter module) are applied through the

mit (interrogation) pulse amplitudes, re-

rf microstrip module to the RADIATED

ceiver sensitivity, and side lobe pulse

TEST ANTENNA connector. From that

amplitude.

point, the interrogation pulses are radiated

2-51. The if. video module accepts the

(via the antenna) to the transponder. Reply

30-MHz if. pulses from the rf microstrip

pulses received from the transponder are

2-13