TM 9-4931-294-15/2
CHAPTER 2
THEORY OF OPERATION
Section I. THEORY OF SIGNAL SOURCE
provided. One is the ∆F mode, in which the frequency
2-1. General
This section contains a discussion on the
may be swept from 0 to 5k % of the total bandwidth in
interrelationship between the three assemblies
use. Another is the internal sweep mode which provides
constituting the signal source and a block diagram level
for sweeping the signal symmetrically about a center
theory discussion of the individual circuits within each
frequency, through any range within the frequency band
assembly. The signal source consists of a backward
of the rf head being utilized. The third is the external
sweep mode which provides for sweeping the rf
synchronizer and seven interchangeable rf heads. For
frequency in accordance with an external sweep signal.
more detailed discussions on the BWO power supply
Both the CW and sweep signals may be internally
and the tunable synchronizer, refer to the applicable
amplitude modulated by a square wave, the frequency of
manufacturer's instruction handbooks.
which is adjustable between 800 and 1, 200 Hz. The rf
2-2. Operational Capabilities
output power, in all modes of operation, may be
The signal source provides rf power in the frequency
maintained at a preset level by a leveling feedback loop.
range from 500 MHz to 40 GHz by means of seven rf
heads (eight frequency bands), each of which covers the
2-3. Basic Functions and Interrelationships
following segment of the 500MHz to 40GHz rf spectrum:
of Signal Source
a. The basic functions, in terms of inputs and
P-Band rf head ..............500 MHz to 1 GHz
outputs, of each of the three signal source assemblies
L-Band rf head...............1 to 2 GHz
are illustrated in figure 2-1. Each rf head contains a BWO
S-band rf head...............2 to 4 GHz
tube and circuitry associated with the BWO power
CX-band rf headcovers
supply. The BWO tubes require helix, anode, filament
and, in some tubes, collector potentials to produce the
C-Band .......................4 to 8 GHz
desired rf output frequencies and power levels. The
Xband .........................8 to 12, 4 GHz
helix voltage requirement of each tube is different,
U-Band rf head ..............12.4 to 18 GHz
however, it is within the range of 100 to 2, 000 volts dc.
K-Band rf head ..............18 to 26.5 GHz
The rf output frequency is dependent, primarily, upon this
Aband rf head ................26.5 to 40 GHz
voltage. The collector element of the P, I, and S-band
BWO tubes requires an operating potential which is 130
Either single frequency continuous wave (CW) signals
volts more positive than the helix voltage. The tubes in
or swept frequency signals may be obtained. In the CW
the other frequency bands do not require a collector
mode of operation, the signal source provides single
voltage. The anode voltage requirement of the BWO
7
frequency signals which are stable to one part in 10 . In
tube is within the range of 0 to 200 volts dc. This
sweep
operation
three
sweep
modes
are
operating potential controls the output
2-1