Anritsu 37 D Series, Руководство по обслуживанию, Страница: 50 / 190

When operating below 38 GHz, signals pass through the SDM
(through the pass-through or doubling sections) and are routed to the
Transfer Switch (a different model switch than is used in the 20 GHz
and 40 GHz instruments). The signal path and down conversion
scheme is nearly identical to the 20 GHz and 40 GHz instruments,
with the exception of the Port 1 and Port 2 MUX coupler circuits,
which are used to pass above-38 GHz or below-38 GHz signals at the
appropriate time during the sweep. ALC control is accomplished using
the Port 1 and Port 2 MUX couplers.
When operating above 38 GHz, the signal from the 16.8 GHz lowpass
filter of the Source Module is fed into a simple SPDT switch. If the in-
strument is sweeping in the forward mode ( S21 or S11), RF is then
switched into the Port 1 (Ref A) Source Quadrupler Module (SQM). If
in the reverse mode (S12 or S22), RF is switched into the Port 2
(Ref B) SQM. Signals then pass through the 37 GHz High Pass Filters
and Test Signals are created within the Port 1 and Port 2 MUX cou-
plers.
Reference Signal paths remain as shown in Figure 3-3 for all four
S Parameters. Test Signal paths for transmission measurements are
as shown in Figure 3-4, but during reflection measurements, Test A
and Test B Signal paths are swapped (Test A is emitted from Port 1
during S11, and Test B is emitted from Port 2 during S22 measure-
ments).
ANALOG SUBSYSTEM ASSEMBLIES THEORY OF OPERATION
3-14 37XXXD MM