TM 11-6625-2575-14
FUNCTIONING OF EQUIPMENT
complementary transistors are interchanged in
the positive and negative supplies.
a. The AN/USM-203A sweep signal generator
c. The +30-volt supply uses a constant cur-
is a solid-state electronic instrument which pro-
rent generator ( Q2 ) to provide constant bias cur-
vides frequency coverage from 0.5 to 1200 MHz
rent to Q3 and Q4. Diode VR2 and resistor R3
in two bands. An external oscilloscope or graphic
protect the regulator against overloads by lim-
recorder is required for external display pur-
iting the drive to series-pass transistor Q1.
poses, or the instrument may be operated as a
Zener diode VR3 and temperature-compensating
cw generator.
diode CR7 provide the voltage reference. Resis-
tor R7 is used to adjust the output voltage to
USM-203A can be divided into five major sec-
+30 volts. Transistor Q4 amplifies differences
tions.
between the output voltage sample and the refer-
(1) Power supply.
ence voltage, and drives Q3 in Darlington connec-
tion with Q1 to automatically compensate for load
(2)
Sweep drive circuits.
voltage error. Capacitors C4, C5, and C6 are used
(3)
Automatic level control and blanking
(if required) for stabilization.
circuits.
d. The +200-volt supply is similar to the other
(4)
Rf circuits.
regulated sources except no constant current gen-
(5)
Marker circuits.
erator is used. Gas discharge tube 12 is the 82-
volt reference. Other components are specified to
NOTE
provide the +200-volt output.
No power supply connections
are
shown.
c. The following paragraphs describe the elec-
(fig. FO-3)
trical operation of the AN/USM-203A. Detailed
operation may be followed in the schematic dia-
modes of operation. These five modes are
gram (fig. FO-3).
achieved by changing the operating characteris-
tics of the basic rate generator, which consists
of a Schmitt trigger and a Miller integrator.
(fig. FO-3)
(1) The bistable Schmitt trigger consists
a. Five separate outputs are provided: +200
of Q101 and, Q102 and associated resistive net-
volts dc, +30 volts dc, and - 30 volts dc (all
works. The output at the collector of Q102 is a
regulated), +50 volts dc unregulated, and a 60-
square wave which is coupled to the blanking cir-
Hz line-synchronizing signal. The four dc sources
cuitry and to the Miller integrator.
supply the various sweep generator functions
(2) The Miller integrator consists of Q103
shown in the schematic diagrams. The line-sync
and Q104 and associated resistor and capacitor
signal is used in the rate generator.
networks. The integrated output at the collector
b. Each regulated dc source is a series-type
of Q104 is a triangular wave. The free-running
transistor regulator. The +30-volt and - 30-volt
condition is established by coupling the output
regulated sources are complementary duals. Cor-
of Q104 to the input of the Schmitt trigger. The
responding polarized capacitors and diodes in
output at the collector of Q104 is coupled to the
the respective supplies are of the same type,
linearity circuitry through emitter follower
but the polarities are reversed. To permit duality,
Q105.
