TM 11-5840-281-35/1
(1) The electronic filter is essentially a
provide sufficiently low impedance so that excessive
lowpass filter with rolloff occurring at approximately 15
degeneration will not occur.
Hz.
The gain of the filter in its pass band is
(7)
The
open-loop
phase-gain
approximately 1.0 db. In operation, the electronic filter
,characteristic of the first integrator is determined by
acts similarly to a double integrator with an output-to-
capacitor C705, with resistor R720 in parallel with the
input feedback loop, except that the high Q resonance
output impedance of tube V703A, and by the phaselag
characteristic of a pure double integrator with feedback
network comprised of capacitor C704 and resistor R716,
has been effectively damped.
with resistor R717 in parallel with resistor R718.
(2) The actual electronic filter circuit is
Capacitors C702 and C703 compensate for the input
comprised of three loops. The first loop, which forms the
capacities of both V702B and V702A, respectively,
first integrator, is that around tubes V701, V702, and
preventing the introduction of additional phase shift. The
V703 through capacitor C701 to the grid of tube V701A.
output of the first integrator is taken at the cathode of
The second loop, which forms the second integrator, is
tube V703B and applied to the grid of tube V704B in the
that around tubes V704, V705, and V706 through resistor
second integrator.
R727 and capacitor C706 to the grid of tube V704A. The
(8) Differential amplifier tube V704 provides
third loop is the overall loop from the cathodes of tube
for negative feedback to the grid of tube V704A in the
V706 through resistors R741 and R702 to the junction of
second integrator, yet allows the polarity to be such that
resistors R701, R702, and R703.
negative feedback is obtained in the overall loop. The
(3) The first two stages (tube V701 and
open-loop phase-gain characteristic of the second
V702) of the first integrator are connected as differential
integrator is determined by capacitor C710, with resistor
amplifiers to minimize drift resulting from power supply
R734 in parallel with the output impedance of tube
variations. Variations in the +200 volt or -200 volt supply
V705B, and the phase-lag network comprised of
result in identical variations at the plates of tubes V701A
capacitor C709 and resistor R731, with resistor R730 in
and V701B and the grids of tubes V702A and V702B;
parallel with resistor R732. Additional phase shifting of
consequently, there is little amplification of supply voltage
the second integrator loop is accomplished by the phase-
variations.
lead network, comprised of capacitor C708 with resistors
(4) The purpose of resistor R709 is to
R723 and R727. In addition, capacitor C708 eliminates
present the same grid circuit resistance to tube V701B
the effects of the input capacity of tube V704A.
as exists at the grid of tube V701A, to minimize drift due
(9) The bandwidth and damping ratio of the
to variations in grid current Capacitor C711 reduces the
overall (or third) loop is determined primarily by resistors
grid current impedance at high frequencies and prevents
R701, R702, R703; capacitor C701; resistors R723,
oscillation due to stray feedback to this grid.
A
R727; and capacitor C706.
secondary function of capacitor C711, together with
(10) To attenuate 400-Hz pulses and other
resistor R709, is to filter noise and ripple from the -35
noise picked up between Radar Receiver-Transmitter
volt supply.
RT-818/TPN-18 and Control-Indicator C-6988/TPN-18,
(5) Control R705 and resistors R708 and
re filters are employed in Control-Indicator C-6988/TPN-
R743 provide an offset adjustment to set the proper level
18.
The filters are resistors R1138, R1142, and
of angle volts at the output of the electronic filter. The
capacitor C1102 in Pulse Generator O-1333/TPN-18;
adjustment range is such that the output voltage can be
and resistor R2101 and capacitor C2101 in the fixed coil
adjusted over a range of at least -6.5 to -10.5 volts with
amplifier. To compensate for the resulting phase delay
the input grounded. This will permit the output to be
introduced to the angle volts, resistors R741, R742, and
adjusted to zero when the angle data input voltage is in
capacitor C712 in the third feedback loop provide phase-
the vicinity of -8.7 volts. The offset voltage source is the
lead compensation.
same as that supplying the antenna angle data control;
(11) The outputs of the elevation and
consequently, the accuracy of the zero adjustment is not
azimuth electronic filters are applied to AZ-EL
affected by variations in the -35 volt supply.
SWITCHING relay K715 in Remote Switching Control C-
(6) The purpose of divider resistors R719
6989/TPN-18. In the precision modes, relay K715
and R721, at the cathode of tube V703A, is to
alternately selects the outputs of the two electronic filters
to produce the az-el angle
2-33
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