Range-gated pulse doppler radar system

• US 4,219,812 A
• Filed: 12/26/1978
• Issued: 08/26/1980
• Est. Priority Date: 12/26/1978
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Rittenbach, Otto E.
• Primary Examiner(s): Hubler, Malcolm F.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/973,356
• Time in Patent Office: 609 Days
• Field of Search: 343/7.3, 343/5 DP
• US Class Current: 342/110
• CPC Class Codes: G01S 13/64 Velocity measuring systems using range gates

Abstract

A range-gated radar system which includes a phase modulator that modulatesn r.f. generator with a signal which may be binary coded. In a preferred embodiment, the binary signal is a periodic signal of 2^N -1 bits per period. Starting at some arbitrary point in the sequence, K contiguous bits are transmitted then M contiguous bits are passed over, then K more bits are transmitted, and so on. The quantities M+K and 2^N -1 have no primary factors in common. The radar system may be a doppler radar system using balanced digital processing which involves separating the upper and lower sideband components of modulation that exist in the return radar signal as a result of the motion of scatterers and subtracting them.

Claims

1. A range-gated radar system including an antenna and transmit-receive device which comprises:

a source of r.f. energy;

a source of a coded binary signal; and

means for phase-modulating said r.f. energy source with said coded binary signal;

said coded binary signal source comprising means for generating a periodic bit sequence having 2ⁿ -1 bits per period, where N is any integer greater than one;

means for selecting K contiguous bits from said sequence starting at some arbitrary point in the sequence;

means for passing over the next M contiguous bits in said sequence wherein 1≦

K≦

M and wherein (2^N -1) and (K+M) have no prime factors in common.

2. A range-gated radar system according to claim 1 including a code delay line connected to the output of said coded binary signal source;

a demodulator code gate responsive to the output of said code delay line;

an in-phase r.f. demodulator coupled to said source of r.f. energy, the output of which is in phase with said source, and to the return signal from the transmit-receive device received by said antenna; and

an in-phase code demodulator responsive to the output of said demodulator code gate and to the output of said in-phase r.f. demodulator.

3. A range-gated radar system according to claim 2 including an in-phase code frequency bandpass filter disposed intermediate said in-phase r.f. demodulator and said in-phase code demodulator.

4. A range-gated radar system according to claim 3 including an in-phase doppler bandpass filter coupled to the output of said in-phase code demodulator.

5. A range-gated radar system according to claim 4 including a noncoherent integrator coupled to the in-phase doppler bandpass filter, and a threshold detector in the output of said noncoherent integrator.

6. A range-gated radar system according to claim 4 further including an r.f. phase shifter coupled to said r.f. energy source the output of which is in phase quadrature with said r.f. energy source;

a quadrature r.f. demodulator connected to the output of said r.f. phase shifter and to said return signal;

a quadrature code frequency bandpass filter in the output of said quadrature r.f. demodulator;

a quadrature code demodulator responsive to the output of said demodulator code gate and to the filtered output of said quadrature r.f. demodulator; and

a quadrature doppler frequency bandpass filter coupled to the output of said quadrature code demodulator.

7. A range-gated radar system according to claim 6 further including a first noncoherent integrator coupled to the in-phase doppler bandpass filter;

a first threshold detector in the output of said first noncoherent integrator;

a second noncoherent integrator coupled to the quadrature doppler bandpass filter; and

a second threshold detector coupled to the output of said second noncoherent integrator.