PULSE COMPRESSION RADAR SYSTEM
First Claim
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1. A pulse compression radar system for producing, from each echo signal corresponding to a target illuminated by a relatively long time-varying coded pulse of electromagnetic energy transmitted from such system, a relatively short time-varying response signal at a time corresponding to the range of each such target, such system comprising:
- a. a clock pulse generator for producing a continuous train of clock pulses;
b. synchronizer means, responsive to the continuous train of clock pulses, for producing synchronizing signals and for producing groups of gated clock pulses during selected periods of time;
c. a coding filter, responsive to each successive clock pulse in a first group of gated clock pulses, for producing like groups of first and second digital numbers, the first portion of each one of such groups consisting of time-varying digital numbers indicative, respectively, of the real and the imaginary components of the modulation of the electromagnetic energy to be transmitted and the remainder of each one of such groups consisting of time-invariant digital numbers;
d. a transmitter/receiver, responsive to the first and the second time-varying digital numbers and to a first synchronizing signal, for converting such numbers into a relatively long time-varying coded pulse of electromagnetic energy to be transmitted and for demodulating each echo signal resulting therefrom to derive groups of third and fourth timevarying digital numbers indicative, respectively, of the real and imaginary components of each echo signal received during a selected period of time, such period being longer, by a period equal to the period required to produce the like groups of first and second digital numbers, than the period of time taken to produce the first group of gated clock pulses;
e. Fourier transform means, responsive to each clock pulse in a second and a third group of gated clock pulses, for producing the complex conjugate of the frequency spectrum represented by the like groups of first and second digital numbers and the frequency spectrum represented by the groups of third and the fourth time-varying digital numbers;
f. correlation means, responsive to the output signals from the Fourier transform means and to each clock pulse in the third group of gated clock pulses, for producing digital numbers representing the frequency spectrum of the relatively short time-varying response signal corresponding to each echo signal and the frequency spectrum, differing from the frequency spectrum of such response signal of spurious signals;
g. inverse Fourier transform means, responsive to the output signals from the correlation means and to each clock pulse in a fourth group of gated clock pulses, for producing a relatively short time-varying response signal at a time indicative of the range of each target and spurious signals at a time indicative of a shorter range; and
, h. gating means responsive to a second synchronizing signal, for inhibiting such spurious signals.
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Abstract
A pulse compression radar system wherein a coding signal indicative of the modulation to be impressed on a transmitted signal is read out of a read only memory and converted to: (a) an analog modulation signal impressed on a radio frequency carrier; and (b) the complex conjugate of the discrete Fourier transform of the coding signal stored in a memory. Each echo signal resulting from illumination of a different target by the modulated transmitted signal is converted to a corresponding digital form indicative of the modulation on each such echo signal, transformed in a discrete Fourier transform and correlated with the stored complex conjugate of the coding signal for the transmitted signal. The resulting correlation signal is weighted and then converted back to a time varying signal in an inverse discrete Fourier transform for utilization.
30 Citations
4 Claims
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1. A pulse compression radar system for producing, from each echo signal corresponding to a target illuminated by a relatively long time-varying coded pulse of electromagnetic energy transmitted from such system, a relatively short time-varying response signal at a time corresponding to the range of each such target, such system comprising:
- a. a clock pulse generator for producing a continuous train of clock pulses;
b. synchronizer means, responsive to the continuous train of clock pulses, for producing synchronizing signals and for producing groups of gated clock pulses during selected periods of time;
c. a coding filter, responsive to each successive clock pulse in a first group of gated clock pulses, for producing like groups of first and second digital numbers, the first portion of each one of such groups consisting of time-varying digital numbers indicative, respectively, of the real and the imaginary components of the modulation of the electromagnetic energy to be transmitted and the remainder of each one of such groups consisting of time-invariant digital numbers;
d. a transmitter/receiver, responsive to the first and the second time-varying digital numbers and to a first synchronizing signal, for converting such numbers into a relatively long time-varying coded pulse of electromagnetic energy to be transmitted and for demodulating each echo signal resulting therefrom to derive groups of third and fourth timevarying digital numbers indicative, respectively, of the real and imaginary components of each echo signal received during a selected period of time, such period being longer, by a period equal to the period required to produce the like groups of first and second digital numbers, than the period of time taken to produce the first group of gated clock pulses;
e. Fourier transform means, responsive to each clock pulse in a second and a third group of gated clock pulses, for producing the complex conjugate of the frequency spectrum represented by the like groups of first and second digital numbers and the frequency spectrum represented by the groups of third and the fourth time-varying digital numbers;
f. correlation means, responsive to the output signals from the Fourier transform means and to each clock pulse in the third group of gated clock pulses, for producing digital numbers representing the frequency spectrum of the relatively short time-varying response signal corresponding to each echo signal and the frequency spectrum, differing from the frequency spectrum of such response signal of spurious signals;
g. inverse Fourier transform means, responsive to the output signals from the correlation means and to each clock pulse in a fourth group of gated clock pulses, for producing a relatively short time-varying response signal at a time indicative of the range of each target and spurious signals at a time indicative of a shorter range; and
, h. gating means responsive to a second synchronizing signal, for inhibiting such spurious signals.
- a. a clock pulse generator for producing a continuous train of clock pulses;
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2. A pulse compression radar system as in claim 1 wherein the coding filter includes a read only memory, such memory being programmed to produce any one of a plurality of different groups of digital numbers, the first portion of each one of such groups corresponding to a different modulation of the electromagnetic energy to be transmitted.
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3. A pulse compression radar system as in claim 2 wherein the correlation means includes weighting means for selectively reducing the frequency spectrum of the spurious signals.
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4. A pulse compression radar system as in claim 3 having, additionally, means for converting the signals out of the gating means to analog signals.
Specification
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Current AssigneeBertram J. Goldstone
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Original AssigneeBertram J. Goldstone
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InventorsGoldstone, Bertram J.
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Primary Examiner(s)Hubler, Malcolm F.
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Application NumberUS05/077,768Time in Patent Office659 DaysField of Search343/17.2PC,5DPUS Class Current342/194CPC Class CodesG01S 13/28 with time compression of re...
