Coherent, frequency multiplexed radar

• US 5,646,623 A
• Filed: 11/24/1981
• Issued: 07/08/1997
• Est. Priority Date: 05/15/1978
• Status: Expired due to Fees

• Current Assignee: Teledyne Instruments Incorporated (Teledyne Technologies Incorporated)
• Original Assignee: Teledyne Instruments Incorporated (Teledyne Technologies Incorporated)
• Inventors: Walters, Glenn A., Teschmacher, Lance M.
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US06/324,677
• Time in Patent Office: 5,705 Days
• Field of Search: 343/5 NQ, 343/17.2 PC, 343/5 HM, 343/5 BB, 343/9 R, 343/14, 343/17.5, 342/112, 342/129, 342/200
• US Class Current: 342/129
• CPC Class Codes: G01S 13/286 frequency shift keyed
• CPC Class Codes: G01S 13/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 7/038 Feedthrough nulling circuits

Abstract

Coherent, frequency multiplexed radar is a new generic type of continuous wave radar architecture wherein contiguous pulses of discrete frequency segmented signals are serially transmitted from an antenna, and after reflection from radar targets, signals from the same antenna are coherently processed in a parallel manner to provide correlated measurements of target'"'"'s pulse compressed range and radial velocity. Simultaneously transmitted and received signals are separated by frequency multiplexing.

Claims

1. A continuous wave, frequency-multiplexed radar system, comprising:

transmitter means for transmitting, against a target, a continuous output signal having successive cycles, each of said cycles including N mutually coherent, contiguous segments, wherein said output signal has a respective predetermined frequency during each of said segments;

receiver means for receiving a return signal produced by reflection of said output signal from said target, while said output signal is being transmitted;

separation means connected to said receiver means for, during each cycle, separating said return signal into N respective frequency components corresponding to said predetermined frequencies;

means for successively obtaining quadrature samples from said separated frequency components for each of the segments of a return signal cycle, said samples being obtained in a predetermined order during each of a plurality of range times following transmission of said signal cycle in said output signal; and

matched filter processing means for combining quadrature samples obtained from a succession of return signal cycles during a respective one of said range times to produce indications of the range and velocity of a target having a range corresponding to said range time.

2. The system of claim 1 wherein said segment frequencies are harmonically related.

3. The system of claim 2 wherein said N successive contiguous segments are pseudo-randomly ordered in each of said output signal cycles.

4. The system of claim 1 wherein all of the segments of a cycle are of the same time duration.

5. A method for measurement of target range and velocity by a continuous wave, frequency-multiplexed radar system including a transform processing means for combining signal samples to produce predetermined target indicia, comprising the steps of:

generating a continuous periodic output signal having successive periods, wherein each of said periods includes N contiguous, mutually coherent time segments in each of which said output signal has a respective predetermined frequency;

continuously transmitting said output signal against a remote target to generate a continuous reflection of said output signal from said target;

continuously receiving said reflected signal while said output signal is being transmitted;

separating N frequencies from said received signal;

obtaining quadrature samples from said separated frequencies for each of the periods of a received signal cycle, said samples being obtained in a predetermined order during each of a plurality of range times following transmission of said period in aid output signal;

for each of said predetermined frequencies, accumulating quadrature samples obtained from a succession of received signal cycles during a respective one of said range times; and

combining all quadrature samples accumulated during said range time to produce indications of the range and velocity of a target having a range from said radar system corresponding to said range time.

6. The method of claim 5 wherein the predetermined frequencies of said cycle time segments are harmonically related.

7. The method of claim 6 wherein time segments are pseudo-randomly ordered.

8. The method of claim 5 wherein all of said time segments are of equal duration.

9. A method for measurement of target range and velocity by a continuous wave, frequency-multiplexed radar system including a transform processing means for combining signal samples to produce predetermined target indicia, comprising the steps of:

generating a continuous periodic output signal having successive periods, wherein each of said periods includes N contiguous, mutually coherent time segments in each of which said output signal has a respective predetermined frequency;

continuously transmitting said output signal against a remote target to generate a continuous reflection of said output signal from said target;

continuously receiving said reflected signal while said output signal is being transmitted;

separating N frequencies from said received signal;

obtaining quadrature samples from said separated frequencies for each of the periods of a received signal cycle, said samples being obtained in a predetermined order during each of a plurality of range times following transmission of said period in said output signal;

for each of said predetermined frequencies, accumulating quadrature samples obtained from a succession of received signal cycles during a respective one of said range times;

pulse-compressing the accumulation of quadrature samples for each of said predetermined frequencies by further sampling each said sample during each of a plurality of fine range times occurring during said time;

progressively phase-shifting accumulated, pulse-compressed quadrature samples obtained during said fine range times and combining phase-shifted quadrature samples to obtain respective Doppler frequency accumulations; and

successively combining all of said respective Doppler frequency accumulations with each of said fine range accumulations to produce indications of the range and speed of a target having a range from said radar system corresponding to a respective one of said fine range times.