Wave Shaping

TM 11-6625-2885-30/NAVAIR 16-35TS3614-2

On figure FO-3 sheet 2, inverter U15 and crystal Y1 make up a 10 MHz

clock. Counters U31 and U11 divide this clock by 20, producing 500 kHz.

Decade counters (U12, U14 and U24) divide this 500 kHz to 500 Hz.

Comparators U13, U22 and U34 pass 500 kHz clock pulses as long as the

count in U12, U14 and U24 is less than that preset in the CS frequency

patch field. Thus, the number of pulses passed in one second is 500 times

the CS frequency preset.

The passed pulses accumulate in a counter (U7 and U8). This counter (U7

and U8) provides the A input to a comparator (U9 and U39). When the count

in U7 and U8 reaches 250, flip-flop U20 sets the B input of the comparator

(U9 and U39) to O, while commanding a down count. When U7 and U8 reach a

count of O, U20 sets the B inputs of U9 and U39 to 250, while commanding

an up count. Thus, this counter (U7 and U8) counts up and down once for

every 500 pulses to it. This produces a triangular time function at the

preset CS frequency.

Digital-to-analog converter U1 changes the count in U7 and U8 into a

triangular analog signal at the preset CS frequency.

b. Wave Shaping. CS and Pulse Control Circuit

Card Assembly 1A2A2 shapes

an incoming triangle wave from 1A2A1. It produces

a sine wave with proper

baseline and amplitude to drive a linear modulator

in Transmitter Assembly

1A1. Figure FO-4 is the schematic diagram of this

circuit card.

In figure FO-4, the diode-resistor network between operational amplifiers

U31A and U32A shapes the incoming CS frequency triangle wave to a sine

wave. Variable resistor R2 sets the symmetry about zero at test point

TP-R.

Operational amplifier U32B offsets the baseline of the sine wave. Vari-

able resistor R25 controls the offset and fixed resistor R31 sets the

amplitude of the CS output waveform.

The CS output waveform controls a linear modulator in the transmitter

assembly.

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