A28 Yig Oscillator (Yo); A29 20 Ghz Doubler; A38 Switch Filter And A43 Lowband Amp Filter (Option 1Eh); Reference/Synthesis Loop - Keysight Technologies E8257D Service Manual

Troubleshooting
Reference/Synthesis Loop Description
frequency to either the stop frequency or a band crossing. The Sweep DAC sets
the start frequency, and the sweep DAC output voltage directly relates to the
YIG output frequency:
— If sweep DAC output = 5V, YIG frequency = 5 GHz
— If sweep DAC output = 10V, YIG frequency = 10 GHz
Signals that are summed with the sweep DAC voltage include:
— delay compensation, which is calculated by the A18 CPU and is dependent
— YIG pre–tune (the pre–tune DAC is always set to 0 volts in sweep mode)
— frequency correction voltage from the A6 Frac–N, which is dependent on

A28 YIG Oscillator (YO)

The A28 YIG Oscillator output frequency (3.2 to 10 GHz) is controlled by the
amount of current through the main and FM coils. The main coil is used to set
the frequency and for FM ≤230 Hz. The FM coil is used for FM rates >230 Hz.
Both the A9 YIG Driver and the A28 YIG Oscillator contribute to phase noise
between 100 KHz and 1 MHz.

A29 20 GHz Doubler

The A29 20 GHz Doubler provides:
— a thru path for output frequencies from 3.2 to 10 GHz
— two internal couplers that provide a 3.2 to 10 GHz signal to both the A6
— a doubler path to generate frequencies from 10 to 20 GHz
— RF signal amplification and filtering
Both the A29 20 GHz Doubler and the A30 Modulation Filter contribute to
phase noise >3.2GHz.

A38 Switch Filter and A43 Lowband Amp Filter (Option 1EH)

The A38 and A43 assemblies provide reduced harmonics below 3.2 GHz. The
assemblies contain low pass filters that are switched in at different frequencies.
The switch filter has several modes. In the CW and analog modulation modes,
filters are on between 250 MHz and 2 GHz, with reduced power between
10 MHz and 2 GHz. In ramp, step and list sweep modes, filters are on between
250 MHz and 2 GHz, with reduced power between 250 MHz and 2 GHz. In IQ
mode, filters are on between 10 MHz and 2 GHz, with reduced power between
10 MHz and 2 GHz, and degrade IQ bandwidth.
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on the sweep rate and frequency band
the amount of frequency correction required
Frac–N for phase locking during sweep operation, and to generate
frequencies ≤3.2 GHz; and the A5 Sampler to provide the feedback needed
for fine tune correction in CW mode
E8257D/67D, E8663D PSG Signal Generators Service Guide