Keysight Agile Signal Generator Service Guide 13
Troubleshooting
Highband/Midband/Lowband modules found on the block diagram. In
addition, this board contains the I/O circuitry for external modulation input
signals, pulse input/output signals, as well as the LF OUTPUT (Low-Frequency
Output) port. Also, the A15 board converts the analog voltages, as detected by
the Highband and Lowband detectors, to the digital signals required by the
DAC Board for ALC control. The A15 board accepts power from the A2 power
supply routed via A4 Mother Board and A10 Midplane.
Plug-in components to the A15 RF Deck Interface board include: A18 Low
Band Output Module, A16 Frequency Multiplier, A17 Agile Mod/Filter, A19
40 GHz Doubler (Option 540/54E), High Band Detector and Coupler, Electronic
Attenuator and Bypass Switch, Mechanical Attenuator.
A16 Frequency Multiplier
The 20 GHz multiplier takes a 675 MHz - 1.5 GHz input frequency from the
highband path on the A14 Lowband/Highband Switch and multiplies the input
signal up with four doubler stages to a maximum frequency of 21.5 GHz. Each
of the doublers contains various amplifiers, attenuators, switches, filters, and
detectors. In addition, there are two limiting amplifiers that provide stable
output levels, given a range of input signal levels. There are two outputs and
one input to the board. Outputs are the inputs to the midband path (1.35 to
6 GHz) and a highband path (5.4-21.5 GHz). The midband path bypasses the
3rd and 4th doublers and outputs a 1.35 to 6 GHz signal at around +17 dBm.
The highband path either bypasses the fourth doubler or goes through the
fourth doubler covering frequencies from 5.4 to 21.5 GHz. The output power of
the highband path is approximately 0 dBm.
A17 Agile Mod/Filter
One function of the A17 Agile Modulation Filter is to switch the highband,
midband and lowband signals into a common path. Therefore the output
frequency range of the A17 Agile Modulation Filter is 10 MHz to 20 GHz. For
frequencies
> 3.0 GHz, the A17 Agile Modulation Filter provides amplitude and
pulse modulation circuitry, power level control, and filtering. Frequencies
≤ 3.0 GHz are simply switched through the A17 Agile Modulation Filter and are
not filtered or modulated by any circuitry.
The highband and midband ALC limiting amplifier control within the A17 Agile
Modulation Filter provides level control and amplitude modulation. For pulse
operation, the pulse modulator within A17 is used. In 20 GHz signal
generators, the A17 Agile Modulation Filter output is routed to the A20 Output
Leveling Module. In 40 GHz signal generators, two outputs from the A17 Agile
Modulation Filter are routed to the A19 40 GHz Doubler, one input for
frequencies ≤ 20 GHz to a bypass switch and one to the 40 GHz Doubler input
circuit.
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