Keysight N9038A, Service Manual, Page: 262 / 745

262 Keysight N9038A MXE Service Guide
L.O. Synthesizer
A14 L.O. Synthesizer Assembly Description
A14 L.O. Synthesizer Assembly Description
A14 L.O. Synthesizer Purpose
The A14 LO Synthesizer assembly has only one purpose and one output signal,
the 1st Local Oscillator (LO) for the A13 RF Front End assembly.
A14 L.O. Synthesizer Description
The main oscillator on the LO Synthesizer assembly is a Voltage Controlled
Oscillator (VCO) that has a frequency range from 570 MHz to 1150 MHz. This
VCO is then multiplied to the desired 1st LO frequency range required by the
A13 Front End assembly.
This VCO/Multiplier technology uses band pass filters after each multiplier
stage to suppress the undesired harmonics.
The LO Synthesizer assembly phase locks the 1st LO to the 4800 MHz
reference signal that is generated and phase locked to the 10 MHz reference
on the A16 Reference Assembly.
The quality of the 4800 MHz reference signal phase lock loop, the 1st LO phase
lock loop, as well as the 10 MHz internal reference signal all have a direct
bearing on the overall frequency stability of the instrument. Users can also
provide their own external reference signal to be used instead of the internal 10
MHz reference, which will also have a direct bearing on the overall stability of
the instrument.
After the different multiplier sections and amplifiers, the resultant frequency
range of the 1st LO provided to the A13 Front End assembly is 3.8 to 8.7 GHz
with an output power from +13 to +18 dBm.
The A14 LO Synthesizer assembly also contains a Field Programmable Gate
Array (FPGA) chip that is programmed from an onboard PROM chip when the
instrument is powered on. This code is updated if necessary when the
instrument software is updated.
Refer to
Chapter 15, “Block Diagrams”
.