coupler in the switched filter path of high power
switched filter assemblies provides the RF signal for
the source quadrupler module (refer to Figure 2-5).
Whenever an instrument is generating RF signals of
>40 GHz, a RF signal is coupled out via J4 to the
source quadrupler module.
The switched low-pass filters provide rejection of the
harmonics that are generated by the YIG-tuned os-
cillator.The 2 to 20 GHz (>2.2 to 20 GHz for
682X5B/683X5B models) RF signal from the modu-
lator has four filtering paths and a through path.
The four filtering paths are 3.3 GHz, 5.5 GHz,
8.4 GHz, and 13.5 GHz. Signals above 13.5 GHz are
routed via the through path.
After routing through the appropriate path, the 2 to
20 GHz (>2.2 to 20 GHz for 682X5B/683X5B models)
RF signal is multiplexed by the PIN switches and
goes via a 20 GHz low-pass filter to the switched fil-
ter assembly output connector J2. The 0.01 to 2 GHz
(0.5 to 2.2 GHz for 682X5B/683X5B models) RF sig-
nal, from the down converter,is received at connec-
tor J1, then multiplexed through the same path to
the switched filter output.
From J2, the RF signal goes to either the directional
coupler (£20 GHz models) or the input connector J1
on the switched doubler module (>20 GHz models).
0.01 to 2 GHz
Down
Converter
The 0.01 to 2 GHz Down Converter assembly (Fig-
ures 2-4 and 2-5) contains a 6.5 GHz VCO that is
phase-locked to the 500 MHz reference signal from
the A3 Reference Loop PCB. The 6.5 GHz VCO’s
phase-lock condition is monitored by the CPU. The
6.5 GHz VCO is on at all times; however,the down
converter amplifier is powered on by the A13 YIG
Driver PCB only when the 0.01 to 2 GHz frequency
range is selected.
During CW or swept frequency operations in the
0.01 to 2 GHz frequency range, the 6.51 to 8.5 GHz
RF signal output from J3 of the switched filter as-
sembly goes to input connector J1 of the down con-
verter.The 6.51 to 8.5 GHz RF signal is then mixed
with the 6.5 GHz VCO signal resulting in a 0.01 to
2 GHz RF signal. The resultant RF signal is fed
through a 2 GHz low-pass filter,then amplified and
routed to the output connector J3. Aportion of the
down converter’s RF output signal is detected,
2-24 682XXB/683XXB MM
FUNCTIONAL RF DECK
DESCRIPTION ASSEMBLIES