This information is decoded by U3A and amplified by U5. The outputs of U5 are approximatley +3 V when a band is valid and approximatley -22 V otherwise. These signals are used to drive FET switches on the A6All Slope Generator and the A6A12 YTX Driver.

Preselector Peak @J

A second latch, UlO, receives the same six lines a U9, but receives a different strobe, LCK5. This strobe is valid when the six lines have preselector peaking information. The outputs of this latch drive eight bits of a DAC which produces 0 to 10 V at the output of U4B corresponding to DAC values of 0.00 to 63.75. This voltage goes to the A6A12 YTX Driver. This circuit is used to adjust the tacking of the YTX when [PRESELECTOR PEAK) or (SHIFT) a), (K) (+dBm), or (SHIFT) Ide] is keyed in.

Hysteresis, Sample-Hold Control, and Filter Capacitor @

U8 is a Quad D-Latch which is used to decode information relating to Hysteresis, Sample and Hold, and Filter Capacitor information. Four lines from the 50-wire Instrument Bus go to the inuts of the latch. The latch is strobed when these lines have valid RF Module information.

The instrument controller is able to connect the filter capacitor across the YTX, and control the Hysteresis and Sample and Hold circuits on the YTX Driver.

Slope Offset @

U7 receives the -0.525 V/GHz signal from the A6A12 YTX Driver, amplifies and offsets it such that a t1.83 V/GH z ramp centered about 6 V is produced at TP8. Qll to Q15 and associated circuitry produce the offset for each band, and R2 varies the A-Band offset to position the A-Band slope breakpoints.

Slope Breakpoint Generator @

The signal at TP8 has a maximum range on Band C (5.8 to 12.5 GHz, second harmonic) of approximately 0 to 12 V. This signal is applied to two voltage dividers R36/R37 and R38/R39, which drive the positive inputs to U6A and U6B respectively. The voltage at the inputs to these op amps is clamped by CR5 and CR6 such that U6A sees only the first half of the full band ramp and U6B sees only the second half. In this manner, each full band

is divided into two segments with one breakpoint in the center. Both U6A and U6B are configured for a gain of 2 and an offset of approximately -6.2 V, for a 0 V output at midband and unity gain overall.

Upper Segment Generator @ and Lower Segment Generator @

The outputs of U6 drive variable gain amplifiers as shown in Figure 1.

2 A6All