Agilent Technologies 856290216 service manual Low-Pass Filter, Sweep Generator

Low-Pass Filter

Refer to function block AB of A4 Log Amplifier Schematic Diagram (sheet 4 of 4) in the

HP 8560 E-Series Spectrum Analyzer Component Level Information.

1.Connect a DVM positive probe to A4J9 pin 4.

2.On the HP 85623 spectrum analyzer, press (CAL).

3.Press FULL IF ADJUST. Observe the DVM reading between the displayed messages

IF ADJUSTSTATUS: 300 kHz RBW and IF ADJUST STATUS: 3 kHz RBW. Duringthistime period, the voltage should be within a 2 to 10 Vdc range.

4.Observe the DVM reading while IF ADJUST STATUS: AMPLITUDE is displayed. The reading should be within the 2 to 10 Vdc range.

5.If the DVM reading is outside the range in step 3 but inside the range in step 4, suspect one of the reactive components of the filter.

Sweep Generator

Refer to function block Z of A4 Log Amplifier Schematic Diagram (sheet 4 of 4) in the

HP 8560 E-Series Spectrum Analyzer Component Level Information.

A properly operating sweep generator generates a series of negative-going parabolas. Before the sweep, switches A4U802C and A4U802D turn on, shorting A4C802 and A4C801 (the output is at 0 volts). These switches open to start the sweep. The output of A4U804A, pin 1, is 0.35 V to 10 V, depending on the sweep width selected by A4U802A and A4U803A. This voltage appears across A4R801. Capacitor A4C801 integrates the current through A4R801. The output of A4U804B is a straight, negative-going ramp. Capacitor A4C802 and resistor A4R802 integrate the output of A4U804A which starts a negative ramp (A4U804C) at the beginning of the sweep. The ramp from A4U804B is added to the current in A4R802 via A4U803B. Integrating this ramp results in the parabolic output waveform.

AM/FM Demodulation, Audio Amplifier, and Speaker

Refer to function blocks R, S, and T of A4 Log Amplifier Schematic (sheet 4 of 4) Diagram in the HP 8560 E-Series Spectrum Analyzer Component Level Information.

If the audio circuits are not functioning use the following procedure to isolate the problem:

1. Set an AM signal generator controls as follows:

Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lOOMHz

Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -6 dBm

Modulation type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80% AM

Modulationfrequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 Hz

2. Set the HP 85623 spectrum analyzer controls as follows:

Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lOO MHz Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz Sweep time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50ms Reference level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 dBm Resolution bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 kHz Amplitude scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LINEAR

9-38 IF Section