U.S. patent number 3,720,952 [Application Number 04/421,826] was granted by the patent office on 1973-03-13 for signal processing apparatus.
Invention is credited to Leo Lawsine.
United States Patent |
3,720,952 |
Lawsine |
March 13, 1973 |
SIGNAL PROCESSING APPARATUS
Abstract
1. Apparatus for processing radar signals and the like,
comprising Wideband signal receiving and transmitting antenna
means; Circulator means having a first terminal connected with said
antenna means, said circulator means including also second and
third terminals; A first tuned microwave mixer set including a
first directional filter, a plurality of first directional filter
mixer units each tuned to a different discrete frequency band, and
first manifold means connecting said first mixer units with said
first directional filter; A second tuned microwave mixer set
including a second directional filter, a plurality of second
directional filter mixer units corresponding in number with said
first mixer units and being tuned to the corresponding frequency
bands thereof, respectively, and second manifold means connecting
said second mixer units with said second directional filter; First
common conductor means connecting the mixture units of the first
set with the second terminal of said circulator means, said first
conductor means containing series-connected series-connected
switch; Second common conductor means connecting the mixture units
of the second set with the third terminal of said circulator means;
Local oscillator signal generator means; First gate means
connecting said signal generator means with all of the mixer units
of said first set; A plurality of second gate means connecting said
signal generator means with the mixture units of said second set,
respectively; And signal processing means having input and output
terminals connected with the directional filters of said first and
second sets, respectively, for controlling the operation of said
switch and of said first and second gating means as a function of
the inherent characteristics of signals received by said antenna
means and for returning to the directional filter means of said
second set a modified facsimile signal.
Inventors: |
Lawsine; Leo (Arlington,
VA) |
Family
ID: |
23672198 |
Appl.
No.: |
04/421,826 |
Filed: |
December 29, 1964 |
Current U.S.
Class: |
342/15 |
Current CPC
Class: |
G01S
7/38 (20130101) |
Current International
Class: |
G01S
7/38 (20060101); H04k 003/00 () |
Field of
Search: |
;343/18,18E,6.5,6.8 |
Primary Examiner: Feinberg; Samuel
Assistant Examiner: Montone; G. E.
Claims
What is claimed is:
1. Apparatus for processing radar signals and the like,
comprising
wideband signal receiving and transmitting antenna means;
circulator means having a first terminal connected with said
antenna means, said circulator means including also second and
third terminals;
a first tuned microwave mixer set including a first directional
filter, a plurality of first directional filter mixer units each
tuned to a different discrete frequency band, and first manifold
means connecting said first mixer units with said first directional
filter;
a second tuned microwave mixer set including a second directional
filter, a plurality of second directional filter mixer units
corresponding in number with said first mixer units and being tuned
to the corresponding frequency bands thereof, respectively, and
second manifold means connecting said second mixer units with said
second directional filter;
first common conductor means connecting the mixer units of the
first set with the second terminal of said circulator means, said
first conductor means containing a series-connected switch;
second common conductor means connecting the mixer units of the
second set with the third terminal of said circulator means;
local oscillator signal generator means;
first gate means connecting said signal generator means with all of
the mixer units of said first set;
a plurality of second gate means connecting said signal generator
means with the mixer units of said second set, respectively;
and signal processing means having input and output terminals
connected with the directional filters of said first and second
sets, respectively, for controlling the operation of said switch
and of said first and second gating means as a function of the
inherent characteristics of signals received by said antenna means
and for returning to the directional filter means of said second
set a modified facsimile signal.
2. Apparatus for processing and repeating radar signals and the
like, comprising
wideband signal receiving and transmitting antenna means;
first and second circulator means each having a first terminal
connected with said antenna means, and second and third
terminals;
first, second, third and fourth microwave mixer sets each including
a directional filter, a plurality of directional filter mixer units
each tuned to a different discrete frequency band, and manifold
means connecting said filter mixer units with said directional
filter, the mixer units of said first and second sets being of the
same number and having corresponding frequency bands, respectively,
the mixer units of said third and fourth sets being of the same
number and having corresponding frequency bands, respectively;
first common conductor means including a first switch connecting
the mixer units of the first set with the second terminal of said
first circulator means;
second common conductor means connecting the mixer units of the
second set with the third terminal of said first circulator
means;
third conductor means including a second switch connecting the
mixer units of said third mixer set with the second terminal of the
second circulator means;
fourth conductor means connecting the mixer units of said fourth
mixer set with the third terminal of the second circulator
means;
signal processing and modifying means having input and output
terminals;
first diplexer means connecting the directional filters of said
first and third mixer sets with the input terminal of said signal
processing and modifying means;
second diplexer means connecting the output terminal of said signal
processing and modifying means with the directional filters of said
second and fourth mixer sets;
local oscillator signal generator means;
first gate means connecting said signal generator means with each
of the mixer units of said first and third mixer sets; and
a plurality of second gate means connecting said signal generator
means with the mixer units of said second and fourth mixer sets,
respectively;
said signal processing and modifying means being operable in
accordance with the inherent characteristic of the signal received
by said antenna means to control the operation of said first and
second gate means and said first and second switches.
3. An electronic countermeasure system for processing the
aircraft-seeking signals generated by a hostile radar installation
and for repeating to said radar installation false target echo
signals, comprising
wideband antenna means operable alternately to receive a first
radar signal and to transmit a processed second radar signal;
microwave front end means connected with said antenna means and
including first tuned mixer means for placing said first signal
within a given first frequency band;
second mixing means for modifying the output signal of said front
end means to produce a signal characteristic of, and having a lower
frequency than, said first radar signal;
delay means for delaying said low frequency signal, said delay
means including a variable delay device;
doppler correcting means controlling the operation of said variable
delay device to effect a doppler frequency shift of said low
frequency signal corresponding to a desired repeated echo range
rate;
means including third mixer means for placing the delayed and
doppler corrected signal in said first frequency band;
means including said first tuned mixer means for converting the
delayed and doppler corrected signal in said first frequency band
to the original frequency of said first radar signal and thereby
produce said second radar signal;
means including said antenna for transmitting said second radar
signal toward said hostile radar installation; and
computer means responsive to the low frequency signal produced by
said second mixing means for controlling the operation of said
first mixing means.
4. An electronic countermeasure system for processing an
aircraft-seeking hostile radar signal within a first frequency band
and for transmitting to said radar installation a processed false
target echo signal having a frequency corresponding with that of
the hostile radar signal, comprising
wideband antenna means operable alternately to receive a first
radar signal within said first frequency band;
microwave front end means connected with said antenna means for
changing the frequency of said first signal to place the same
within a second frequency band smaller than the hostile radar
signal
first frequency band, said front end means including a plurality of
channels each containing a plurality of tuned directional filter
mixer means, first signal generator means, and gage means
connecting said first signal generator means with each of said
directional filter mixer means, respectively, each of said
directional filter mixer means being tuned to a different
incremental portion of the hostile radar signal frequency band;
second mixer means for modifying the output signal of said front
end means to produce a second signal characteristic of said first
radar signal, said second mixing means including a balanced mixer
having a first input terminal connected with the output of the
microwave front end, a second input terminal, and an output
terminal, second signal generator means, and hybrid junction means
connecting said second generator means with said second input
terminal;
fixed and variable delay means connected with the output terminal
of said balanced mixer means for delaying said second signal;
doppler adjusting means controlling the operation of said variable
delay device to effect doppler frequency shift of said second
signal corresponding to a desired repeated echo range rate;
third mixer means including said second signal generator means and
said hybrid junction means for increasing the frequency of the
delayed second signal;
means including said microwave front end means for converting the
increased-frequency delayed signal to the first frequency band and
thereby produce a processed third radar signal;
means including said antenna for transmitting said processed third
radar signal toward said hostile radar installation; and
programmed computer means responsive to the second signal for
controlling the operation of said first and second signal
generating means, said gate means, said doppler adjusting means and
said antenna means as a function of the inherent characteristics of
said first signal.
Description
This invention relates generally to an improved electronic
countermeasure system for processing the aircraft and
spacecraft-seeking signals of one or more hostile radar
installations and for repeating to those installations false target
echo signals of corresponding frequency.
Many types of electronic countermeasure systems have been proposed
in the past for protecting aircraft and spaceborne vehicles against
detection by hostile radar. In general the known countermeasure
systems -- in addition to being complex and quite expensive -- are
often unreliable in operation and are restricted in operational
capabilities. Many of the known systems include equipment that is
large and massive, thus reducing the useable interior capacity and
flight range of the spacecraft. Furthermore, certain types of
complex countermeasure systems require manual operation and/or
control by highly trained technical personnel, further increasing
the size of the flight crew and the attendant problems of aircraft
design.
The primary object of the present invention is to provide an
improved electronic countermeasure system that is reliable and
flexible in operation, that is relatively inexpensive relative to
the known systems, and that lends itself to semi-automatic or
fully-automatic operation.
A more specific object of the invention is to provide a
countermeasure system for aircraft, seaborne and ground
installations that is instrumented to perform, in real time, all
the important deception repeater jamming operations. The system is
operable to repeat pulse or continuous wave signals against
anywhere from one to 100 hostile radars operating in either the
search or track mode. The system performs also against radars
provided with electronic counter-countermeasure means, such as
frequency diversity, frequency jumping, and random, staggered,
jittered or coded pulse repetition rate frequencies. The present
invention, which makes use of programmed computer control means in
response to the specific characteristics of the hostile radar
signal, is operable to repeat either earlier or later in time the
true target echo, whereby the repeated echo appears at a shorter or
longer range on a radar display (or as recorded on a data
processor). Furthermore, the present system includes doppler
correction means that supply a doppler frequency correction to
compensate for different simulated vehicle speeds in correlation
with the repeated echo.
The system of the present invention, which repeats a signal based
on the characteristics of the received signal, may be programmed to
change the time of retransmission, the time base (i.e., compress or
expand the time frame) or to communicate between a number of
systems. In the electronic countermeasure mode of operation, all of
the operational features are correlated in terms of time, frequency
and phase. The system is also applicable for use in the
communication mode as a link in a communication satellite network,
for example.
The invention is characterized by the provision of multi-spectral
component mixing program means affording precise control of time,
frequency and phase. Use is made of novel microwave front end means
in combination with special programmed computer control means.
With regard to a typical tactical mission, as the vehicle with the
electronic countermeasure deception jamming system approaches the
hostile radar, an analysis is continuously made of all program
inputs. Such information is partially derived from ancillary
equipment in the vehicle, and partly from intelligence supplied
prior to the mission. The date from these two sources are
associated with real and non-real time. Included are such
parameters as pulse repetition frequency, altitude, angle (azimuth
and elevation), pulse duration, scan rate, target cross section,
radar power, slant range, relative strength of main and side lobes,
speed of the vehicle, and the like. The operator of the vehicle
selects a predetermined program (on a tape, for example) in
accordance with the prearranged tactics and new factors as they
develop.
When the vehicle is within range of the hostile radar, the system
repeats during real time, the radar signals in both the search and
track modes. On each radar display, the false echo signal produced
by the system appears at least as strong as the expected target
echo (since the system operates as a one-way transmitter as
distinguished from the two-way reflection radar system). If the
false echo represents the radar signal repeated earlier, it appears
at a short range. Furthermore, it can be made to move faster than
the target echo -- i.e., it will simulate a higher speed by closing
the range faster. At the same time, the doppler frequency shift
(corresponding to the higher speed) is also generated. This doppler
shift may be achieved at speeds ranging from a few miles per hour
to speeds on the order of Mach 5 or greater.
Since the signal from the vehicle may be programmed to come down a
sidelobe of the radar beam, the repeated signal will also be false
in angle (for both the search and track modes). Even sophisticated
monopulse tracking radars could be deceived into tracking with
their side lobes.
The system is capable of automatically repeating pulse or
continuous wave signals against 100 or more radars, depending on
computer capacity, duty cycle, signal characteristics, electronic
countermeasure techniques and tactical requirements. The
operational capabilities are achieved by automatic processing of
the spectral components of the radar signal. Such frequency domain
operation utilizes unique techniques to control frequency and pulse
transmission instantly and automatically. To this end, the
frequency components are filled in or reinserted as directed by the
computer program.
Other objects and advantages of the invention will become apparent
from a study of the following specification when considered in
conjunction with the accompanying drawing, in which:
FIGS. 1 and 2 are simplified and detailed illustrations,
respectively, in block diagram form, of the wide band electronic
countermeasure deception repeater jammer system of the present
invention.
Referring first to FIG. 1, the wide band antenna 1 is of the
equiangular (or logarithmic) spiral type broadbanded over 2 or more
octaves. Such antennas are particularly suitable for high speed
airborne and space vehicles. The antenna phase centers are
frequency scanned by frequency scanner 2 at a programmed rate
(e.g., 20 or 30 megacycles) during reception and are directed to a
specific location during transmission. The frequency scanner is
controlled by a programmed computer 3 to perform several functions
as will be described in greater detail below. The computer, which
may be of any suitable type (for example, the General Electric
A-236 Real Time Computer including such units as a conventional
clock, counter, ring counter, memory, address matrix, address
scanner, subtractor and gate former circuits) is operable to
provide the unique results of the present invention. By means of
the antenna scanning means, an effective area, up to 180.degree.
solid angle, for example, may be scanned from the underside of an
airplane wing during reception, and steered to a selected location
within nanoseconds during transmission. For any radar mode of
operation (i.e., search or track) the system of the present
invention will receive, process and repeat continuous wave or
radiofrequency pulses in the range covering the microwave bands
generally used by radars. In describing system operation, a typical
signal range from 2-9 gigacycles has been selected.
During reception (i.e., the scanning period) the radar signal
passes through a crossed field amplifier 4 which serves as a
passive low loss device (0.5 decibels) in the "receive" direction.
The signal enters the microwave front end 5 where it is separated
by duplexer 6 into two or more paths depending on the desired
signal bands. In the illustrated embodiment, the signal is divided
into two bands (specifically, 2-4 and 4-9 gigacycles). Signals
falling in the lower and upper bands are fed to the tuned microwave
mixer sets 7 and 8, respectively, depending on the signal
frequency. Since the operation of the mixers 7 and 8 is identical,
in the following description only the processing of the signals in
the 2-4 gigacycle range will be described.
Local oscillator 9, which is also controlled by the computer 3,
generates signals in the 1-2 gigacycle range that are applied to
the tuned mixers 7 and 8 via the 10-gate computer-controlled
oscillator gate means 10. The local oscillator 9 may be a
carcinotron operating as a voltage tuned backward wave oscillator,
or a travelling wave tube with regeneration. The local oscillator
frequencies (in the 1-2 gigacycle range) may be obtained by
modulating the carcinotron sole with white Gaussian noise at a high
frequency rate, for example, in the range 10 to 30 megacycles. This
technique effectively fills in "frequency holes" that might result
from the use of Gaussian noise alone. The oscillator frequency
spectrum then contains all frequencies over the band 1-2
gigacycles. In the illustrated embodiment, the local oscillator
gate means comprise diode switches controlled by the computer
3.
The output signal from the tuned microwave mixer set 7, which
represents the sum and difference frequency components, is filtered
through unit 7 (which passes spectral components in the range 4-7
gigacycles) and is applied to the microwave amplifier 11. At the
input to amplifier 11 (which may be a traveling wave tube), the
signal level is approximately -90 decibels. For a nominal gain of
25 decibels, the amplifier output is on the order of -65 decibels.
Preferably the amplifier 11 is provided with instantaneous
automatic gain control for suppressing ring-around action.
The output from the amplifier is applied to the balanced mixer 12
for mixing with a signal that is supplied by the
computer-controlled local oscillator 13 via hybrid junction 14 as
programmed by the computer. The local oscillator frequency band
covers the range of 4.1-7.1 gigacycles. The output signal from
mixer 12, is amplified by the broadband intermediate frequency
amplifier 15 at 100 .+-. 60 megacycle bandwidth. Selection of the
IF bandwidth is based on the smallest anticipated time delay
inherent in the system (on the order of 0.05 to 0.1 microseconds).
The local oscillators 9 and 13 may time share a single local
oscillator component controlled by computer 3.
The derived 100 .+-. 60 megacycle broadband signal is fed through
the fixed and variable delay lines 16 and 17, and the delayed
signal is amplified by the intermediate frequency amplifier 18 and
is applied to one input of the balanced mixer 19. As indicated by
the broken line 20, the variable delay line 17 is associated with a
doppler correcting means 21 that is conventional in the art and
includes a variable speed means, servomotor amplifier means, a
motor, a generator, a differential generator and an attenuator.
While the amplifier 15, the fixed and variable delay means 16 and
17, the amplifier 18, and the doppler means 21 constitute
conventional matching components, the delay lines (generally
quartz) may be modified in accordance with the anticipated pulse
repetition frequency, the simulated vehicle speed (correlated with
the doppler frequency shift of the repeated pulse) and the tactical
considerations envisioned. In this respect, the range of
corrections applicable on doppler frequency shifts will vary from
0.1 to 15 microseconds or higher to cover a range of speeds from 80
miles per hour to Mach 13 or higher. A typical length of the quartz
line (for a 500 microsecond delay) is equivalent to about 40 miles
in range. The operation and structure of the doppler correcting
means will be described in greater detail below. Pulse repetition
information is also supplied by the IF amplifier 15 to the computer
3 via conductor 22. The programmed computer automatically utilizes
the spacing between consecutive pulses for timing and delay
purposes. Consequently, a received signal with random, jittered,
staggered or coded pulse repetition frequency will be processed in
such a manner that the repeated signal will appear as a valid
target return to the hostile radar.
In the balanced mixer 19, the 100 .+-. 60 megacycle signal is mixed
with the 4.1 to 7.1 gigacycle signal supplied by oscillator 13 via
hybrid junction 14 as controlled by the computer program. The
reconverted output of the mixer 19, having a typical level of -65
decibels, is now a broadband delayed signal. This signal is
amplified by microwave amplifier 23 (which comprises, for example,
a traveling wave tube) and appears as an approximately -40 decibel
signal level that is attenuated by attenuator 24 which supplies a
standard level to microwave amplifier 25. This latter amplifier
brings the output signal to a level suitable for processing by the
microwave front end means 5. Instantaneous automatic gain control
may be supplied to microwave amplifier 23 to prevent ring around
effects.
The delayed signal that is applied to the mixer set 8 of the front
end 5 is filtered to supply spectral components in the 4-7
gigacycle range that are mixed with the 1-2 gigacycle local
oscillator signals supplied via the computer controlled gates
10.
The resultant signal, which represents a reconstituted facsimile of
the original radar signal that is delayed in time and corrected for
a predetermined doppler shift, is then passed through duplexer 6 to
the crossed-field amplifier 4 which provides a nominal power gain
of approximately 20 decibels. As directed by the computer program,
the signal is amplified by the amplifier 4 and is repeated from
antenna 1 to a selected location or radar site.
Referring now to FIG. 2, the duplexer 6 of the microwave front end
includes a filter diplexer 40 that separates the incoming signal
into two or more paths (specifically, those including the bands 2-4
gigacycles and 4-9 gigacycles in the described embodiment). The
operation of each band path is substantially identical. The
duplexer 6 includes circulators 41 and 42 associated with the
respective bands. The 2-4 gigacycle range signals from the filter
diplexer 40 are applied, via circulator 41 and nanosecond switch
43, to the input directional filter manifold 44 having a
termination 45. The filter manifold coveys the signal to a
plurality of directional filter mixers 46-49 which serve as tuning
elements and mixers to separate the signal into discrete
overlapping narrow band channels. If needed, ancillary equipment
may be provided to afford adjustability as desired. Similarly the
4-9 gigacycle range signals from filter diplexer 40 are applied,
via circulator 42 and nanosecond switch 53, to the input
directional filter manifold 54 having a termination 55. The
switching operations of switches 43 and 53 during both the
reception and repeating periods are controlled by computer 3.
During reception switches 43 and 53 and the diode switch associated
with the output 110 of oscillator gate 10 are closed while the
diode switches associated with gates 101-109 are open. During
repeating, switches 43 and 53 and gate switch 110 are open, while
gate switches 101-109 are closed as determined by the computer
program. The switches 43 and 53 provide nanosecond operation.
Thus, in the reception period, for a signal in the 2-4 gigacycle
range, the local oscillator signal band (1-2 gigacycles) is fed to
all tuned mixer elements in such a manner that mixer outputs are
produced only in those elements that are tuned to the radar input
signal. The mixer output signal, which consists of the sum and
difference products, is routed via waveguide or stripline channels
(with suitable interfacing joints, if desired) to the output
directional filter manifold 60 having a termination 61. The signal
passes through directional filter 62 which filters out spectral
components in the range of 4-7 gigacycles. Filter 62 is designed
with proper bandpass or band rejection skirts to channel out only
4-7 gigacycle components. The spectral output is now passed through
filter diplexer 63 to microwave amplifier 11.
In a similar manner, a signal in the 4-9 gigacylce range is
processed from circulator 42 via switch 53 to the input directional
filter manifold 54. The signal is applied to one or more of the
directional filter mixers 66, 67, 68, 69 and 70 (in accordance with
signal frequency) and is mixed with the 1-2 gigacycle local
oscillator signal gated via diode switch gate 110. The resulting
mixer output signal is then routed via waveguide or stripline
channels to the output directional filter manifold 72 having a
termination 73. The signal is filtered through directional filter
74 which passes the 4-7 gigacycle spectrum components to microwave
amplifier 11 via diplexer 63.
The tuning ranges of the directional filter-mixers are as
follows:
During During reception transmission filter-mixer 46 134 2.0-2.5
gigacycle filter-mixer 47 135 2.5-3.0 gigacycle filter-mixer 48 136
3.0-3.5 gigacycle filter-mixer 49 137 3.5-4.0 gigacycle
filter-mixer 66 138 4.0-5.0 gigacycle filter-mixer 67 139 5.0-6.0
gigacycle filter-mixer 68 140 6.0-7.0 gigacycle filter-mixer 69 141
7.0-8.0 gigacycle filter-mixer 70 142 8.0-9.0 gigacycle
Thus the signal supplied to microwave amplifier 11 contains 4-7
gigacycle spectral components representative of the radar signal in
the range 2-9 gigacycles. As noted before, it is amplified by
amplifier 11 and is converted in balanced mixer 12 with the local
oscillator 4.1-7.1 gigacycle signal supplied via hybrid junction 14
as programmed by computer 3. The resulting signal is amplified by
intermediate frequency amplifier 15 with a passband of 100 .+-. 60
megacycles, and is fed to computer 3 and fixed delay line 16.
The computer 3 performs three distinct functions. First, it stores
the pulse repetition frequency information in the memory storage
section. Secondly, it controls the timing of all system functions,
such as starting, stopping and switching. Finally, it processes
pulse repetition frequency information (whether regular or
irregular). The storage and timing functions are accomplished in a
conventional manner and need not be described in detail. For the
processing of the pulse repetition rate frequency, however, novel
means are provided for utilizing the difference in time between
consecutive pulses to determine a gate width which will cause
certain pulses to be repeated at such a time that the hostile radar
is deceived (that is to cause the radar to accept the pulse as one
of its own reflected signals). Thus, the computer clock 90 times
all units of the computer at a given rate (for example, at a 1
megacycle rate). Thus, the signal supplied to computer 3 from the
intermediate frequency amplifier 15 via conductor 22 starts a
counter 91 which is gated by ring counter 92 operating at a nominal
rate of 2 megacycles. The counter 91 resets ring counter 92 which
shifts from gate 1 to gate 2 and so forth to gate n. The outputs on
lines 1, 2 ... n (corresponding to the gates) are committed to the
memory 93. Words t.sub.1, t.sub.2... t.sub.n are called from memory
93 by the address matrix 94 when actuated by the address scanner
95. The address scanner is essentially an addition unit which gates
the lines 1, 2 ... n from the memory so that words t.sub.1, t.sub.2
... t.sub.n will be allowed through subtractor 96. The subtractor
puts out differences .DELTA. t.sub.1, .DELTA.t.sub.2 ...
.DELTA.t.sub.n between consecutive pulse intervals into gate former
97 which forms 1 more pulse than the word. Thus a zero time
difference produces 1 pulse, 1 unit time difference produces 2
pulses, 2 units produces 3 pulses, and so forth. These pulse
outputs from the gate former modulate the crossed field amplifier 4
which repeats the radiofrequency signal in these several pulses so
that the hostile radar selects only its own radiofrequency pulse
signal and throws out all the other pulses. In this manner, it is
possible to repeat effectively against radar with irregular pulse
repetition rate frequencies, e.g., staggered, jittered, random,
coded signals and the like.
The fixed delay line 16 consists of one or more sections which
cover the radar pulse repetition frequency signal range with
anticipated pulse intervals. Variable delay line 17 supplies a fine
adjustment for the total delay and a rate of change of delay to
represent the range rate of the repeated echo. With respect to this
latter function, doppler correcting network 21 operates as follows.
The variable speed drive 120 is set for the airborne or spaceborne
vehicle in which it is installed. The drive output feeds servo
amplifier 121 that drives motor 122. The motor, which is calibrated
in terms of equivalent feet of delay line, is mechanically linked
with variable delay line 17, generator 123, and differential
generator 124. As part of the servo loop, the generator smooths out
variations in motor speed (whereby the speed is maintained
constant) such that the rate of change of the variable delay line
is a true equivalent of the input speed information (i.e., the
range rate). Differential generator 124 transforms the rate of
change of delay line into a doppler voltage which is passed to
attenuator 125 and then to microwave amplifier 23 (specifically, to
the helix of a travelling wave tube). This results in a phase
change of the delayed radiofrequency signal that is correlated with
the desired speed of the vehicle at all times.
The delayed intermediate frequency at 100 .+-. 60 megacycles is
mixed in balanced mixer 19 with the 1.4-7.1 gigacycle local
oscillator signal band generated by local oscillator 13 and gated
by hybrid junction 14. This reconversion produces delayed spectral
components which are attenuated and further amplified in microwave
amplifier 23.
The delayed signal is routed via filter diplexer 127 to directional
filters 128 and 129 which filter out the 4-7 gigacycle spectral
components. This signal appears in input directional filter
manifolds 130 and 131 having terminations 132 and 133,
respectively. The signal is routed to directional filter mixers
134-137 in the 2-4 gigacycle path and to directional filter mixers
138-142 in the 4-9 gigacycle path. Then one or more of the
filter-mixer units will be activated with the local oscillator band
1-2 gigacycle signal depending on those diode switch gates 101-109
which have been selected by the computer 3. The resulting mixer
output from the activated unit now represents a reconstituted
facsimile of the original radar signal delayed in time and
corrected for a predetermined doppler shift. The signal (or
signals) are then routed, via the output directional filter
manifolds 143 and 144 with termination 145 and 146, respectively,
to circulators 41 and 42 and to filter diplexer 40. In accordance
with the computer program, the delayed and doppler-corrected signal
is amplified in amplifier 4 which may be modulated with additional
pulse gates as previously described. The signal is now repeated and
beamed via wide band antenna 1 to a selected location or radar
site.
It is apparent that the system of the present invention constitutes
a wide-band, multi-spectral component mixer, duplexer system with
computer program control of timing, frequency and phase. The system
repeats signals earlier or later with the correct doppler frequency
and when feasible, will repeat also at a false angle. The operation
may be performed on 100 or more radars, depending on computer
capacity and system factors. The system performs satisfactorily
even for sophisticated radars using frequency diversity, frequency
jumping, monopulse tracking, random, jittered, staggered or coded
pulse repetition rate frequency, and so forth.
While in accordance with the provisions of the Patent Statutes, the
preferred form and embodiment of the invention has been illustrated
and described, it will be apparent to those skilled in the art that
various changes and modifications may be made in the apparatus
described without deviating from the invention set forth in the
following claims.
* * * * *