Servo loop processor
First Claim
1. A servo loop processor suitable for use in determining the time shift between first and second like signals, said first signal occurring in time prior to said second signal, said servo loop processor comprising:
- controllable delay means, connected to receive said first signal, for delaying said first signal, said controllable delay means having a delay control input;
comparison means for receiving said second signal and being coupled to the output of said delay means for receiving said delayed first signal, and for comparing said delayed first signal with said second signal and generating an error signal relating to the difference therebetween;
reference producing means for receiving said second signal, and for producing a reference signal in accordance therewith;
multiplier means, coupled to outputs of said comparison means and said reference producing means, for multiplying said error signal by said reference signal and for producing a correction signal in accordance therewith; and
,delay control means, coupled to an output of said multiplier means and to the delay control input of said controllable delay means, for controlling said controllable delay means so that said first signal is delayed by an amount intended to bring it into time correspondence with said second signal at which point said error signal reduces to zero.
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Abstract
A servo loop processor suitable for use in a passive radar range determining system is disclosed. Early and late overlapping video pulse trains derived from spaced receiving antennas are fed to separate first and second channels and are sampled and held from pulse period to pulse period to form signals representing the amplitude envelopes of the received pulse trains. The output of the first channel is variably delayed and the delayed signal is compared with the undelayed output of the second channel to create an error signal. The output of the second channel is also differentiated, and the result is sampled and held to create a reference signal that has the proper phase relationship with the error signal so that the error signal can be multiplied by the reference signal to create a correction signal. The resulting correction signal is integrated and fed back to control the time delay applied to the output of the first channel such that a closed servo loop is formed. At balance, the integrated correction signal is related to the distance between the radar antenna transmitting the pulse trains, and the receiving antennas. In an alternative embodiment, envelope signals representing the first and second channel pulse trains are converted from analog to digital form, and the digitized second channel output is subtracted from the same digitized signal delayed by a fixed interval to form a digital version of the above-mentioned reference signal. A digital version of the error signal, derived as above, is then multiplied by the digital reference signal to create a digital correction signal, which after integration, controls the time delay of the first channel output signal.
13 Citations
22 Claims
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1. A servo loop processor suitable for use in determining the time shift between first and second like signals, said first signal occurring in time prior to said second signal, said servo loop processor comprising:
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controllable delay means, connected to receive said first signal, for delaying said first signal, said controllable delay means having a delay control input; comparison means for receiving said second signal and being coupled to the output of said delay means for receiving said delayed first signal, and for comparing said delayed first signal with said second signal and generating an error signal relating to the difference therebetween; reference producing means for receiving said second signal, and for producing a reference signal in accordance therewith; multiplier means, coupled to outputs of said comparison means and said reference producing means, for multiplying said error signal by said reference signal and for producing a correction signal in accordance therewith; and
,delay control means, coupled to an output of said multiplier means and to the delay control input of said controllable delay means, for controlling said controllable delay means so that said first signal is delayed by an amount intended to bring it into time correspondence with said second signal at which point said error signal reduces to zero. - View Dependent Claims (2, 3, 4, 5, 12, 13, 14, 15, 16, 17, 18)
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6. A servo loop processor suitable for use in a passive radar range determining system adapted to receive video pulse trains, generated by a transmitting radar antenna, at two spaced receiving antennas, the envelopes of said video pulse trains overlapping to the point that they are almost, but not quite, coincident, said servo loop processor comprising:
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a first envelope generating means connected to receive the earliest occurring video pulse train, for generating a first envelope signal related to the envelope of the waveform of said earliest video pulse train; a second envelope generating means, connected to receive the latest occurring video pulse train, for generating a second envelope signal related to the envelope of the waveform of said latest video pulse train; control means for controlling said first and second envelope generating means; reference signal generating means connected to said second envelope generating means for generating a reference signal in accordance therewith, said reference signal having a quadrature relationship with said second envelope signal; and
,servo loop means, connected to receive said reference signal, the output of said first envelope generating means and the output of said second envelope generating means, for controllably delaying the output of said first envelope generating means as a function of a multiplication of said reference signal by an error signal that represents the difference between said delayed output of said first envelope generating means and said output of said second envelope generating means, until said delayed output corresponds in time to the output of said second envelope generating means. - View Dependent Claims (7, 8, 9, 10, 11)
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19. A servo loop processor suitable for use in a passive system for monitoring a radar signal source that transmits a train of video pulses, and in which the passive system is associated with antennas that receive the pulse train at a finite time differential characterized by the envelopes of the received video pulse trains overlapping to the point that they are almost, but not quite, coincident, said servo loop processor comprising:
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first envelope detection means connected to receive the earliest occurring video pulse train, for generating a first envelope signal related to the envelope of said earliest occurring video pulse train; second envelope detection means, connected to receive the latest occurring video pulse train, for generating a second envelope signal related to the envelope of said latest occurring video pulse train; first fixed delay means for receiving said second envelope signal and having a first delay output producing a version of said second envelope signal delayed by a first predetermined interval, and having a second delay output for producing a version of said second envelope signal having a second predetermined delay interval, wherein said second predetermined delay interval is less than said first predetermined delay interval; a controllable delay means, connected to receive said first envelope signal, for delaying said first envelope signal, said controllable delay means having a delay control input; a second fixed delay means connected in series with said controllable delay means for delaying said first envelope signal by an additional amount equal to said second predetermined delay interval of said second output of said first fixed delay means; comparison means for receiving said first envelope signal after it has been delayed by said controllable delay means and by said second fixed delay means, and for receiving said second envelope signal from said second output of said first fixed delay means and thus after said second envelope signal has been delayed by said second predetermined interval, said comparison means comparing the thusly delayed first and second envelope signals and generating an error signal relating to the difference therebetween; reference signal subtraction means coupled to the first output of said fixed delay means and to said second envelope detection means for subtracting said first envelope signal delayed by said first predetermined interval from the undelayed first envelope signal so as to produce a reference signal having a predetermined phase relationship with said second envelope signal; multiplier means coupled to receive said reference signal from said reference signal subtraction means and to receive said error signal from said comparison means, and for multiplying said error signal by said reference signal to produce a correction signal in accordance therewith; and
,delay control means coupled to an output of said multiplier means and to said delay control input of said controllable delay means, for controlling said controllable delay means so that said first envelope signal as delayed and applied to said comparison means is controllably delayed by an amount tending to bring it into time correspondence with said second envelope signal delayed by said second predetermined interval and applied to said comparison means. - View Dependent Claims (20, 21, 22)
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Specification