Front Panel-Rear Panel; Rf Section - HP 8340B Manual

The
rear panel interface signals (e.g. HP-IB,
SWEEP OUTPUT, Z-AXIS)
are also routed through or
generated
in the controller functional group. The sweep control signal from the controller stops and
starts the sweep generator. As mentioned, during bandcrossings, the sweep must be stopped to
phase
lock the
YO before
the
sweep can continue.
The controller monitors sweep events
such as
bandcrossings, end of sweep, and markers, and executes specific instructions according to each
sweep
event.
FRONT PANEL
-
REAR PANEL
Front Panel
The
front panel contains the user-interface displays and keyboard as well as various input and output
connectors. The displays have
a
dedicated microprocessor that keeps them updated. When the
instrument processor places
display data into the display interface
latch,
it
signals the display
pro¬
cessor that information
is
ready.
The
display processor immediately
takes
the data from the latch and
stores
it in
internal memory.
The
data
is handled when the
display processor has time.
The
keyboard communicates directly with the instrument processor. When
a
key
is
pressed, the
instrument processor either executes that key (if
it is
a
single key
operation),
or waits for completion of
the key
sequence. Different
key sequences not only allow you
to set the instrument for normal opera¬
tion, but also allow access to internal registers, latches,
D
to
A
converters, and calibration constants
for troubleshooting.
Rear Panel
A
rear panel schematic shows
all
interconnections between
the rear panel connectors and related
internal assemblies.
RF SECTION
The
RF Section contains the microcircuits and control
circuits
that produce the
10 MHz to 20.0 GHz
(HP 8341 B)
or
26.5
GHz (HP 8340B)
RF output from the 2.3
to
7.0 GHz
YO
loop output.
The RF
output from the
A45
directional coupler
in the
YO
loop is
fed to the modulator/splitter (mod/
splitter) in
the RF section. Band 0 (10
MHz
to 2.3 Ghz)
is
the heterodyne band and
is
produced by
mixing
a
swept
LO drive from the mod/splitter with the
phase-locked 3.7 GHz oscillator output. The
IP
signal from the low band mixer
is
routed through the low band power amplifier, the
switched-YIG-
tuned
multiplier
(SYTM), the high band coupler, and the 90
dB step attenuator before
it
reaches the RF
output connector. The
SYTM and high band coupler perform no function
in
this
band.
Band
1
(2.3 to 7.0 GHz) is the same as the
YO fundamental frequency. The RF from
the high
band
output
on
the mod/splitter
is
amplified by the high band
power
amplifier and
passes
through the
SYTM
to the high band coupler. Part of the RF
is
coupled
to the high band
detector for leveling through the
ALC Loop. After the coupler, the RF passes through the 90 dB step attenuator, to
the
RF
OUTPUT.
A-6
Assembly-Level Service Overall Instrument Theory Change
7 HP 8340B/41B