Anritsu 682XXB, 683XXB 682XXB/683XXB MM 2-25

amplified, and coupled out for use in internal level-
ing. The detected RF sample is routed to the A10
ALC PCB.
The 0.01 to 2 GHz RF output from the down con-
verter goes to input connector J1 of the switched fil-
ter assembly.There, the 0.01 to 2 GHz RF signal is
multiplexed into the switched filter’s output path.
0.5 to 2.2 GHz
Digital Down
Converter
The 0.5 to 2.2 GHz Digital Down Converter assem-
bly (Figures 2-6 and 2-7), found in the 682X5B/
683X5B models, provides improved phase noise
across the 0.5 to 2.2 GHz frequency range. Power is
applied to the down converter assembly at all times;
however,the down converter amplifier is powered
on by the A13 YIG Driver PCB only when the 0.5 to
2.2 GHz frequency range is selected.
During CW or swept frequency operations in the 0.5
to 2.2 GHz frequency range, the 2 to 4.4 GHz RF
signal output from J3 of the switched filter assem-
bly goes to the input connector J1 of the digital
down converter.In the down converter, the 2 to
4.4 GHz RF signal is divided by 2 to produce fre-
quencies of 1 to 2.2 GHz and divided by 2 again to
develop frequencies of 0.5 to 1 GHz. From the fre-
quency dividers, the 0.5 to 2.2 GHz RF signal then
goes to the modulator which provides power level
control, AM, and pulse modulation of the RF sig-
nals.
In addition to the 0.5 to 2.2 GHz RF signal from the
frequency dividers, the modulator has two other in-
puts—the modulator control input and the pulse in-
put. The modulator control input adjusts the gain of
the modulator to control the power level of the RF
output signals. The modulator control signal is re-
ceived from the A9 PIN Control PCB where it is de-
veloped from the ALC control signal. Amplitude
modulation is accomplished by varying the modula-
tor control signal with the modulating signal. Pulse
modulation is achieved by switching the modulator
on and off at a rate determined by the modulating
pulse input. The modulating pulse input is received
via connector J4 from the A6 Pulse Generator PCB.
The modulating pulse signal is also routed out via
connector J5 to the switched filter assembly.
The RF signal from the modulator is amplified and
fed via PIN switches to the switched low-pass fil-
682XXB/683XXB MM 2-25
FUNCTIONAL RF DECK
DESCRIPTION ASSEMBLIES