Agilent Technologies 8590 Series Service Manual page 371

Assembly Descriptions and Block Diagrams
RF and LO Section for 8592L, 8593E, 8594E, 8594L, 8594Q, 8595E, and 8596E Analyzers
Tracking Oscillator
The tracking oscillator enables the fine adjustment of the tracking
generator output frequency to compensate for the frequency
inaccuracies of the analyzer 21.4 MHz IF. The tracking oscillator
determines the residual FM and frequency drift of the tracking
generator. The 184.28 MHz output frequency is obtained by doubling
the output of a crystal oscillator operating at 92.14 MHz.
Upconverter
The upconverter mixes the tracking oscillator output with the buffered
600 MHz reference from the A9 third converter assembly. The
upconverter also contains a filter to pass only the 784.28 MHz upper
sideband.
Pentupler
The pentupler multiplies the 784.28 MHz signal by five to generate
3.9214 GHz, the analyzer first IF in low band. A dual cavity bandpass
filter centered at 3.9214 GHz eliminates all unwanted multiples of
784.28 MHz.
Modulator
The output of the pentupler is passed through a modulator to adjust the
power level into the output mixer. The modulator is controlled by an
ALC circuit on the bias board, which is fed by a detector in the output
amplifier. If the detected output power is too high, the ALC will drive
the modulator to decrease the input level into the output mixer,
resulting in a decrease in output power.
Coupler
The first LO signal from the A3A14 first LO distribution amplifier
assembly is coupled off, then buffered to drive the output mixer. The
main line of the coupler is fed to the LO OUTPUT connector on the rear
panel. The loss through the coupler main line is less than 2.5 dB.
Output Mixer
The 3.9214 GHz signal from the modulator is fed into the RF port of the
output mixer. The LO port of the output mixer is driven by the buffered
first LO signal from the coupler. The output of the mixer is then
amplified.
Chapter 9 371