Doppler correlation radar providing coarse-range detection resolution

• US 3,882,495 A
• Filed: 06/11/1973
• Issued: 05/06/1975
• Est. Priority Date: 06/11/1973
• Status: Expired due to Term

• Current Assignee: Thomas Vincent Bolger
• Original Assignee: Thomas Vincent Bolger
• Inventors: Bolger, Thomas Vincent
• Primary Examiner(s): Hubler, Malcolm F.
• Application Number:
  US05/368,869
• Time in Patent Office: 694 Days
• Field of Search: 340/258A 343/5PD,5SA,7.7
• US Class Current: 342/189
• CPC Class Codes: G01S 13/52 Discriminating between fixed and moving objects or between objects moving at different speeds

Abstract

Special types of transmitted code and decoding signals for different selected range subintervals within the maximum range of interest result in the optimization of range sensitivity for each subinterval.

Claims

1. In a moving target correlation radar system of the type comprising means for transmitting a continuous carrier wave modulated with a predetermined encoded modulating signal, means for demodulating echo signals received from any moving target within a given range illuminated with said transmitted signal, means for generating a decoding signal, and doppler-frequency means including correlation decoding means for correlating said demodulated echo signals against said decoding signal to derive an output signal from said correlation decoding means which includes the doppler-frequency signature of any moving target then being detectEd;

the improvement wherein;

said moving targets comprise a predetermined plurality of different target types each having a distinctive dopplerfrequency signature and a distinctive radar cross-section, and said decoding signal generating means includes means for applying to said correlation decoding means at least a selected one of a group of different predetermined decoding signals each of which has a format corresponding to a different target type, each of said respective formats of said different decoding signals only correlating with said demodulated echo signal over a different range subinterval of said given range with the range subinterval corresponding to a target type of relatively smaller radar cross-section being closer than the range subinterval corresponding to a target type of relatively larger radar cross section.

2. The system defined in claim 1, wherein the amount of correlation for each different decoding signal has a peak value for targets at a predetermined range within the range subinterval corresponding to that decoding signal, has a value of zero at ranges within said given range which are outside of the range subinterval corresponding to that decoding signal and has values which increase toward said peak value as the range within the range subinterval corresponding to that decoding signal approaches said predetermined range from either side.

3. The system defined in claim 2, wherein said different range subintervals partially overlap but with said predetermined range of peak value of correlation of each range subinterval being situated solely within its own range subinterval, and time-controlled means synchronized with said encoded modulating signal for switching said decoding signals in order at those respective instants of time at which the amount of correlation of the further of any two overlapping range subintervals becomes larger than the amount of correlation of the closer of these two overlapping range subintervals.

4. The system defined in claim 1, wherein said different target types comprise a crawling man, a walking man and a moving vehicle.

5. The system defined in claim 1, wherein said correlation decoding means includes a separate correlation decoding channel corresponding with each of said group of different predetermined decoding signals, said respective decoding channels being coupled in parallel to simultaneously correlate said demodulated echo the decoding signal with which that respective decoding channel corresponds, and means for adding the outputs from all said decoding channels to obtain a signal proportional to the sum thereof as said output signal from said correlation decoding means.

6. In a moving target correlation radar system of the type comprising means for transmitting a continuous carrier wave modulated with a predetermined encoded modulating signal, homodyne means for demodulating echo signals received from any moving target within a given range illuminated with said transmitted signal, means for generating a decoding signal, and doppler-frequency means including correlation decoding means for correlating said demodulated echo signals against said decoding signal to derive an output signal from said correlation decoding means which includes the doppler-frequency signature of any moving target then being detected;

the improvement wherein;

said transmitting means includes means for generating a cyclic encoded modulating signal, each cycle of said encoded modulating signal including at least one pair of contiguous time periods each of which has substantially the same given duration, said encoded modulating signal having a relatively high level for the given duration of one of said pair of periods and a relatively low level for the given duration of the other of said pairs of periods, and said means for generating said decoding signal includes means for applying at least a selected one of a plurality of different predetermined cyclic decoding signals to said correlation decoding means, Each cycle of any one of said decoding signals including first and second substantially identical pairs of contiguous time periods, one corresponding period of each of said first and second pairs having a relatively high level for the duration of that one corresponding period and the other corresponding period of each of said first and second pairs having a relatively low level for the duration of that other corresponding period, the duration of each of said first and second pairs of said one of said decoding signals of being less than said given duration, said first pair of periods of said one of said different decoding signals having a given phase relationship with respect to said one period of said encoded modulating signal and said second pair of periods of said one of said different decoding signals having the same given phase relationship with respect to said other period of said encoded modulating signal, the respective value of said given phase relationship for each different decoding signal being different from each other, and each of said different decoding signals including a blank portion which occurs during any part of said periods of said encoded modulating signal not occupied by said first and second pairs of that decoding signal.

7. The system defined in claim 6, wherein the duration of each of said first and second pairs for each different decoding signal is different from each other.

8. The system defined in claim 6, wherein the boundary between said contiguous periods of said first pair of said one decoding signal occurs at a given delay no greater than said given duration from the beginning of said one period of said encoded demodulating signal, the boundary between said contiguous periods of said second pair of said one decoding signal occurs at the same given delay from the beginning of said other period of said encoded modulating signal, and the value of said given delay for each different decoding signal is different from each other.

9. The system defined in claim 8, wherein said given duration corresponds to twice said given range and the value of said given delay corresponds to no greater than said given range.