HP 85640A, Руководство по эксплуатации и обслуживанию

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buered 1st LO signal from the coupler . The mixer output is then
amplied.
Output amplier The signal from the output mixer passes through the low-pass lter of
the output amplier , which then amplies the signal to a usable range .
The amplier also contains a detector for leveling the output.
Bias board The bias board houses the ALC circuitry for the tracking generator .
It also distributes dc power to the rest of A2. ALC inputs originate
from the A3 Interface Assembly (for power level control), from the
rear-panel EXT ALC INPUT , and from the output amplier detector .
The ALC loop drives the modulator .
A3 Interface Assembly
The A3 interface assembly provides control signals for the A2 tracking generator's power
level and tracking oscillator . A3 also monitors A2's ALC MON (ALC monitor) line to check for
unleveled output. The A2 tracking generator 600 MHz drive signal originates on A3.
300 MHz to 600 MHz
converter
This circuitry receives the host spectrum analyzer's 300 MHz,
010 dBm CAL OUTPUT signal. The signal is doubled to 600 MHz
to drive the A2 tracking generator . The converter consists of two
amplication stages followed by a frequency doubler and A3U4, a
factory-selected attenuator . A3U4 is used to set the output power
from the converter to 08 dBm at 600 MHz. The circuit's 300 MHz
notch lter eliminates the 300 MHz fundamental signal.
P ower level control The power level of the A2 tracking generator is controlled by both
the front panel OUTPUT LEVEL vernier and the rear panel 0.5V/GHz
INPUT from the host spectrum analyzer . The 0.5V/GHz INPUT
provides slope (atness) compensation to the output power level.
Unlevel detector The A2 tracking generator provides the ALC MON (ALC monitor)
control line to the A3 interface . The A2 output is leveled when
ALC MON is between 00.545 V and +1.09 V . The unlevel detector
buers ALC MON and feeds this signal to a window comparator . The
window comparator output is low when the output is unleveled.
It is normal for the output to be unleveled momentarily
during retrace . The host spectrum analyzer's BLANKING signal
prevents a ashing UNLEVELED LED during retrace . The
BLANKING signal is high during retrace and low during a sweep .
P ower supply The power supply circuitry provides added ltering for the +15 V
and 015 V supplies and regulators for the +5 V and 610 V supplies .
Tracking control The tracking control circuitry generates the +TUNE control line .
This control line determines the A2 tracking generator's tracking
oscillator frequency . Tracking is controlled by setting the front panel
TRA CKING ADJUST potentiometer and A3R1 COR TRA CK (coarse
tracking). Noise on the +TUNE line may cause residual FM on the
tracking generator output.
7-22 Service Information HP 85640A RF T racking Generator Operation and Service Manual