TM 9-4931-294-15/2
power of the BWO tube. The required filament voltage is
mode of operation provides an rf output which is
6.3 volts dc.
modulated by a square wave, the frequency of which is
b. The primary function of the BWO power supply is
adjustable between 800 and 1, 200 Hz. Square wave
modulation is accomplished by superimposing a square
to generate, regulate, and control the above mentioned
wave on the anode voltage.
operating potentials required by the BWO tube.
capabilities of the signal source may also be utilized with
Secondary functions of the BWO power supply are to:
square wave operation.
(1) Provide ac power for operation of the tunable
b. External Pulse or Square Wave Modulation.
synchronizer.
External modulation can be used in the frequency range
(2) Provide sweep and blanking voltages for use
from 1.8 to 12.4 GHz. External modulation is achieved
by operating the signal source in the CW mode of
(3) Provide an adjustable bias voltage for an
operation and connecting a PIN modulator module' or
combination to its output. The PIN modulator attenuates
c. The tunable synchronizer provides for phase
the CW rf signal applied to its input in accordance with a
locking the output frequency of the BWO tube to an
pulse or square wave signal from the modulator. The
internal, crystal-derived reference frequency.
pulse repetition rate and pulse duration of the modulated
signal available at the output of the PIN modulator are
2-4. CW Mode of Operation
controlled by the control settings on the modulator. An
a. In the CW mode of operation the signal source
advantage of external modulation is that the rf frequency
provides rf power at a single frequency and power level.
of the signal can be phaselocked since the signal source
The frequency is settable to within 2% of the
in operated in the CW mode.
FREQUENCYMC counter indication on the rf head by
adjusting the helix voltage applied to the BWO tube by
2-6. Sweep Modes of Operation
means of the FREQUENCYMC control. The use of the
The three sweep modes of operation provide an rf output
tunable synchronizer provides frequency stability up to 1
7
This is accomplished by comparing the
which is swept linearly over a preselected frequency
part in 10'
range. In the ∆F mode, the signal is swept about the
phase of a sample of the BWO output frequency with a
crystal-derived reference frequency, and converting the
center frequency (set by the FREQUENCYMC control)
difference in phase to a correction voltage which is
from 0 to 570 of the total bandwidth adjustable by the
∆F% control). In the internal sweep mode of operation,
superimposed on the helix voltage.
Phaselock
synchronization may be utilized in the CW mode of
the sweep width may be adjusted by the SWEEP WIDTH
operation only.
control to any desired range within the rf band covered
b. A power leveling capability is provided to maintain
by the rf head in use. Sweep operation is accomplished
the rf power output level of the signal source constant
by superimposing a sawtooth waveform on the helix
with changing frequency and load impedance. (The
voltage. The amplitude of this superimposed sawtooth
impedance of a given load may change with frequency.)
determines the sweep width while its repetition rate
Leveling is accomplished by sampling the rf output power
determines the frequency at which the sweep occurs.
with an external coupler, detecting the sampled power
Sweep rates of 0.03 to 25 Hz are obtainable by adjusting
with a crystal detector and applying the dc voltage thus
the SWEEP RATE, FREQ RANGECPS and SWEEP
obtained to the LEVEL IN connector on the BWO power
RATE ADJ controls. The external sweep mode provides
supply. This dc leveling voltage controls the anode
for sweeping the rf frequency in accordance with the
voltage, thus correcting for changes in power output.
signal applied to the EXT SWP connector. In order to
maintain a constant rf power level during sweep
2-5. Square Wave and Pulse Modes of Operation
operation, it is necessary to utilize the power leveling
capabilities of the signal source.
Internal Square Wave Modulation.
The square wave
2-3