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Model
2001
CIRCUIT DESCRIPTION
4.1 MECHANICAL ARRANGEMENT
Before beginning the actual circuit description, i t would be
well to consider the mechanical arrangement of the instru-
ment. This will enable the following block diagram and cir-
cuit description to be associated with its physical position,
thereby, providing a better understanding of the overall in-
strument. The mechanical arrangement can be seen by re-
ferring to Figure 5-17 in the Maintenance section. This
TOP VIEW shows the Front Panel, plug-in module and the
rear chassis Power Supply sections.
4.2 SIMPLIFIED BLOCK DIAGRAM
The block diagram in Figure 4-1 contains both block and
module information.
The blocks contained within each
module are indicated by the module outline.
The Power Supply provides three regulated voltage sources
of +18, -18, and -20 volts for connections to the plug-in
modules.
The M1H module generates the sweep ramp, blanking and
scope horizontal voltages.
The M2H module contains four distinct circuits; a -16 volt
reference supply,
a
+ I 6 volt reference supply, an inverted
sweep ramp supply, and the sweep drive circuits.
The two reference supplies and the two sweep ramp voltages
provide the signals t o the Frontpanel frequency and sweep
width controls. The signal from these controls is then fed
t o the sweep drive circuit in the M2H module, where they
arecombined into a single signal, which drives the frequency
determined varactor diodes in the sweep oscillator modules.
Necessary level shifting, shaping and amplitude control is
provided by the sweep drive circuit.
The RF signal for BAND 1 ( 1 to 500 MHz) is generated in
the M9H module where the signal from two sweep oscilla-
tors are combined in a diode mixer.
The resultant,
difference signal, is fed to a 1-500 MHz pre-amplifier and
then t o the MlOH module. This module contains a voltage
variable attenuator and the final 1-500 MHz amplifier.
The output from this amplifier is then fed t o the M19H
module where a PIN diode switch completes the circuit to
the RF output circuit.
error between the two voltages is amplified in the leveler
amplifier located in the MlOH module. The error voltage
is then connected t o the voltage variable attenuator at the
input of the final 1 t o 500 MHz amplifier. This closed loop
system maintains a constant amplitude
RF
signal at the
monitor point, which compensates for amplitude variation
in the sweep oscillator, mixer, and amplifier circuit and
also creates a zero impedance at the monitor point.
I n
order to create a 50 ohm source impedance, a 50 ohm
resistor is connected between the zero impedance point
and the RF output system.
The sweep oscillators for bands 2
& 3
are located in the
M19H module. The RF output from the oscillators is fed
through voltage variable attenuators directly to the RF
output circuit without amplification.
Leveling for bands
2 & 3 is accomplished in the same manner a s for band 1.
The marker circuit is comprised of the marker adder
module M5H, and the individual marker generators M6's.
I n addition to the marker adding function of the M5H
module, i t also provides for selection and leveling of the
sweep sample signal in the same manner as the main RF
output signal was leveled. This provides a constant ampli-
tude sweep sample signal t o the individual marker modules
which is extremely important to obtain a "flat comb"
output from the harmonic generating marker modules. It
also standardizes the sweep sample amplitude in all 2001
instruments, which insures proper operation of field in-
stalled markers.
This constant amplitude sweep sample signal is then fed to
the individual M6 marker modules where it is combined in a
mixer with a crystal controlled CW signal. The resultant
difference signals ( b i r d y markers) are then fed back
to the marker adder module where they are combined, am-
plified, and shaped into a single composite signal. This
signal is then fed through the marker size control and t o
the Front Panel vertical output connector.
Leveling of the RF output is accomplished by a monitor
diode which measures the RF voltage and compares
it
t o a
reference voltage supply by the vernier output control. Any
Model 2001
4.1
MECHANICAL ARRANGEMENT
Before beginning the actual circuit description, it would be
well to consider the mechanical arrangement of the instru-
ment. This will enable the following block diagram and cir-
cuit description to be associated with its physical position,
thereby, providing a better understanding of the overall in-
strument. The mechanical arrangement can be seen by re-
ferring to Figure 5-17 in the Maintenance section.
This
TOP VIEW shows the Front Panel, plug-in module and the
rear chassis Power Supply sections.
4.2 SIMPLIFIED BLOCK DIAGRAM
The block diagram in Figure 4-1 contains both block and
module information.
The blocks contained within each
module are indicated by the module outline.
The Power Supply provides three regulated voltage sources
of + 18, -18, and -20 volts for connections to the plug-in
modules.
The M 1 H module generates the sweep ramp, blanking and
scope horizontal voltages_
The M2H module contains four distinct circuits; a -16 volt
reference supply, a +16 volt reference supply, an inverted
sweep ramp supply, and the sweep drive circuits.
The two reference supplies and the two sweep ramp voltages
provide the signals to the Front Panel frequency and sweep
width controls. The signal from these controls is then fed
to the sweep drive circuit in the M2H module, where they
are combined into a single signal, wh ich drives the frequency
determined varactor diodes in the sweep oscillator modules.
Necessary level shifting, shaping and amplitude control is
provided by the sweep drive circuit.
The RF signal for BAND 1 (1 to 500 MHz) is generated in
the M9H module where the signal from two sweep oscilla-
tors are combined in a diode mixer.
The resultant,
difference signal, is fed to a 1-500 MHz pre-amplifier and
then to the Ml0H module. This module contains a voltage
variable attenuator and the final 1-500 MHz amplifier.
The output from this amplifier is then fed to the M19H
module where a PIN diode switch completes the circuit to
the RF output circuit.
Leveling of the RF output is accomplished by a monitor
diode which measures the RF voltage and compares it to a
reference voltage supply by the vernier output control. Any
CIRCUIT DESCRIPTION
error between the two voltages is amplified in the leveler
amplifier located in the M 1 OH module. The error voltage
is then connected to the voltage variable attenuator at the
input of the final 1 to 500 MHz amplifier. This closed loop
system maintains a constant amplitude RF signal at the
monitor point, which compensates for amplitude variation
in the sweep oscillator, mixer, and amplifier circuit and
also creates a zero impedance at the monitor point.
In
order to create a 50 ohm source impedance, a 50 ohm
resistor is connected between the zero impedance point
and the R F output system.
The sweep oscillators for bands 2
&
3 are located in the
M19H module. The RF output from the oscillators is fed
through voltage variable attenuators directly to the RF
output circuit without amplification.
Leveling for bands
2
&
3 is accomplished in the same manner as for band 1.
The marker circuit is comprised of the marker adder
module M5H, and the individual marker generators M6's.
In addition to the marker adding function of the M5H
module, it also provides for selection and leveling of the
sweep sample signal in the same manner as the main RF
output signal was leveled. This provides a constant ampli-
tude sweep sample signal to the individual marker modules
which is extremely important to obtain a "flat comb"
output from the harmonic generating marker modules. It
also standardizes the sweep sample amplitude in all 2001
instruments, which insures proper operation of field in-
stalled markers.
Th is constant amplitude sweep sample signal is then fed to
the individual M6 marker modules where it is combined in a
mixer with a crystal controlled CW signal.
The resultant
difference signals (birdy markers) are then fed back
to the marker adder module where they are combined, am-
plified, and shaped into a single composite signal.
This
signal is then fed through the marker size control and to
the Front Panel vertical output connector.
4-3
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