Third Converter (part of A15)

The third converter down-converts the 310.7 MHz IF to 10.7 MHz. A PIN-diode switch selects the LO signal used. For normal operation, a 300 MHz LO signal is used. The signal is derived from the 600 MHz reference PLL. During signal identification (SIG ID ON), the 298 MHz SIG ID oscillator is fed to the double balanced mixer on alternate sweeps. Signal identification is available as Option 008.

Flatness Compensation Amplifiers (part of AM)

The flatness compensation amplifiers amplify the output of the double-balanced mixer. The amplifier variable gain (0 to 45 dB) compensates for flatness variations within a band. Band conversion loss is compensated by step gain amplifiers in the IF section.

Control for the amplifiers originates from two DACs on the A3 Interface assembly. (DAC values are interpolated approximately every 17 MHz based on data obtained during the frequency response adjustment.) The Al5 flatness-compensation control circuitry converts the RF GAIN voltage, from A3, into two currents: RF GAIN1 and RF GAIN2. These currents drive PIN diodes in the flatness compensation amplifiers.

General Troubleshooting 7-45

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Agilent Technologies 856290216 service manual Third Converter part of A15, Flatness Compensation Amplifiers part of AM