Anritsu 37 D Series, Maintenance Manual

Page: 49 / 190

Both Reference signals and both Test Signals are routed into the Sam-
pler/Down Conversion Modules for down conversion to 2.5 MHz
(3rd IF signal). This down conversion is accomplished by using LO1
and LO2 found on the A1 and A2 PCBs. Before use by the Sam-
pler/Down Conversion Module, the signal from LO1 is amplified by the
Power Amplifier assembly (mounted on the Sampler/Down Conversion
Module) for a power gain of about 30 dB. (The Power Amplifier and
Sampler/Down Conversion Module are tuned to match each other and
are not replaceable separately).
The individual Test and Reference 2.5 MHz signals are routed off the
Test Set Module to the A3, A4, and A6 IF Processor PCBs as shown in
Figures 3-2 and 3-3.
Test Set Module,
50 GHz and 65 GHz
Instruments
Refer to Figures 3-4 and 3-5 for a graphical representation of the fol-
lowing description:
Many RF components found in the 50 GHz and 65 GHz models per-
form nearly identical functions as components in the 20 GHz and
40 GHz models, with the following exceptions:
q Transfer Switch
q SPDT Switch
q Port 1 MUX Coupler
q Port 2 MUX Coupler
q Port 1 and Port 2 Source Quadrupler Modules
q 37 GHz High Pass Filters
As in the 20 GHz and 40 GHz models, two Reference Signals and two
Test Signals are created. The Reference Signals are used for phase
locking of the RF Source and for phase measurements. The Test Sig-
nals are routed to the DUT and are not involved in phase locking of
the Source Module. One Reference Signal and one Test Signal is gener-
ated at any given time during a normal S Parameter measurement.
The formulas for the S Parameters are the same as described above.
After the signals are received from the DUT, the down conversion
scheme is identical to the 20 GHz and 40 GHz models (described
above).
The RF from the Source Module is routed to either the SPDT switch or
to the SDM. Signals routed to the SPDT switch will eventually become
signals used by the instrument while operating over 38 GHz, and sig-
nals routed to the SDM will be used by the instrument while operating
below 38 GHz.
THEORY OF OPERATION ANALOG SUBSYSTEM ASSEMBLIES
37XXXD MM 3-13