E8257D/67D, E8663D PSG Signal Generators Service Guide 155
Troubleshooting
RF Path Description (Frequency Generation, Level Control, and Modulation)
RF Path Description
(Frequency Generation, Level Control, and Modulation)
The RF path can divide, pass through, and multiply the A28 YIG Oscillator (YO)
signal to generate the desired RF frequency. Depending on models and
options, the RF path includes hardware for amplitude, pulse, and digital (I/Q)
modulation and controls the RF output power level. The Synthesis /Reference
Block Description provides additional information on generating fundamental
frequencies of 3.2 GHz to 10 GHz.
All RF signals originate from the A28 YIG Oscillator (YO) output frequencies of
3.2 GHz to 10 GHz. RF output frequencies below 3.2 GHz are generated by
dividing the YO signal on the A6 Frac–N and A8 Lowband Output assembly. RF
output frequencies between 3.2 and 10 GHz pass through the A29 20 GHz
Doubler. RF output frequencies between 10 to 20 GHz are generated by
doubling the 5 to 10 GHz YO signal in the A29 20 GHz Doubler. In 40 GHz
analog models, RF output frequencies above 20 GHz are generated by
doubling the 10 to 20 GHz signal output of the A29 20 GHz Doubler in the
A27 40 GHz Doubler. In analog models with output frequencies greater than
40 GHz, the A27 40 GHz Doubler is replaced with the A36 Quadraplier. The
A36 Quadraplier generates all frequencies above 20 GHz. The A36 Quadraplier
contains two doublers. The first doubler is a 40 GHz doubler that doubles the
10 to 20 GHz from the A30 Modulation Filter to generate frequencies between
20 and 40 GHz. The second doubler in the A36 Quadraplier doubles
frequencies above 20 GHz (from the 40 GHz doubler) to generate frequencies
above 40 GHz.
In vector models with frequencies above 20 GHz, the RF output is generated
using the A37 Upconverter. The A37 Upconverter contains a mixer, band pass
filters, ALC and pulse modulation diodes, and amplifiers. The A27 40 GHz
Doubler is used to generate a 20 to 40 GHz LO input to the A37 Upconverter.
The input to the A27 40 GHz Doubler is an 11.4 to 19 GHz signal out of the A35
3–20 GHz IQ Modulator. A 5.7 to 9.5 GHz output from the A35 3–20 GHz IQ
Modulator is used for the A37 Upconverter IQ input. For frequencies of 20 to
28.5 GHz, the difference product from the mixer is used and between 28.5 and
44 GHz, the summing mixing product is used.
Analog Model
Hardware
In analog models, the RF Path comprises the following:
—A6 Frac–N
—A8 Output
— A12 Fast Pulse Modulation (Option UNW)
— A27 40 GHz Doubler (40 GHz models)
— A29 20 GHz Doubler
— A30 Modulation Filter
— A36 Quadraplier (> 40 GHz models)
— A38 Switch Filter (< 3.2 GHz if Option 1EH is installed)
— A43 Lowband Amp Filter
— AT1 Attenuator (if Option 1E1 is installed). Analog models have a 90 dB step
attenuator and vector models have a 115 dB step attenuator.
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