5-10 Keysight N5221A/22A Service GuideTheory of OperationSynthesized Source Group Operation5-Refer to Table 5-3 and Figure 5-3 for band numbers and frequencies discussedhere.In bands 2-10, the output of the swept VCO is passed directly or through adivide-by-2, 4, or 8 circuit to produce the output frequencies as listed in Table5-3.In band 6, the output of the swept VCO is passed through a divide-by-4 circuitand then sent to a Direct Digital Synthesizer to produce the output frequenciesfor bands 2-4 as listed in Table 5-3.In bands 11-21, the swept VCO signal is passed through a doubler circuitwhere the signal for some bands are sent directly to the output of thesynthesizer board while other bands are passed through another doublercircuit then to the output of the synthesizer board to produce the outputfrequencies listed in Table 5-3.The output of the A11 13.5 GHz synthesizer board (the LO synthesizer) is 7.438MHz higher than the output of the A4 and A13 13.5 GHz synthesizer boards(the source synthesizers). This is because the output of the A11 13.5 GHzsynthesizer board is routed through the A21 LO multiplier/amplifier 26.5 boardto the A23 and A24 mixer bricks where they are mixed with the test signals toproduce a 7.438 MHz IF signal for each of eight receivers (A–D and R1–R4).Refer to “A23 and A24 Mixer Bricks” on page 5-21 for a more completedescription.A5 and A8 26.5 GHz Source BoardsIn bands 2–9, the input signals from the A4 or A13 13.5 GHz synthesizer boardare passed through to both outputs (main and secondary) unchanged.For bands 10-15, the input signals are passed directly to the secondary outputor amplified and filtered, then sent to the main output.For bands 16-21, the input signals are doubled, filtered, and amplified. Thesignals for these bands are then either passed directly to the secondary outputor passed through more amplification and filtering and sent to the main output.Together these signals for bands 2–21 create the full synthesized sourceoutput frequency range of 10 MHz to 26.5 GHz. These output frequencies foreach band are listed in Table 5-3.The A5 26.5 GHz source board provides an EXT TSET DRIVE RF OUT signal tothe rear panel. This signal is output at a frequency range of 3.2–26.5 GHz foruse with an external test set. This output is terminated with a 50-ohm load onthe A8 26.5 GHz source.The companion signal, EXT TEST SET DRIVE LO, is output from the A23 mixerbrick. Refer to “A23 and A24 Mixer Bricks” on page 5-21.
