Doppler correlation radar providing combined target detection and ranging

• US 3,882,494 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:
  US05/368,661
• Time in Patent Office: 694 Days
• Field of Search: 340/258A 343/5SA,5PD,7.7
• US Class Current: 342/136
• CPC Class Codes: G01S 13/325 using transmission of coded signals, e.g. P.S.K. signals
• 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 having serial detection and range bins portions permit a single decoder channel to provide a relatively soft aural signal to any detected target not within a selected range bin and a relatively loud aural signal to any detected target within the selected range bin.

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 including a pseudo-random code sequence, means for demodulating echo signals received from any moving target within a given range illuminated with said transmitted signal, range-bins switch means for selectively deriving a delayed pseudo-random code sequence having a delay corresponding to any one of a plurality of different range bins, means coupled to said range-bins switch for generating a decoding signal including a pseudo-random code sequence manifesting the delay selected by said range-bins switch, 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 signal of a moving target having a range within the range bin selected by said range bins switch means;

the improvement wherein;

said transmitting means is arranged to provide a cyclic encoded modulating signal, each cycle of said encoded modulating signal including at least one detection portion and one range bins portion which occur serially with respect to each other, said pseudo-random code sequence occurring only during said rangebins portion, said encoded modulating signal having a first format during a detection portion thereof, and said decoding signal generating means is arranged to provide a cyclic decoding signal, each cycle of said decoding signal including at least one detection portion and one range-bins portion which occur serially with respect to each other in predetermined phase relationship with respect to said detection portion and range-bins portion of said encoded modulating signal, said delayed pseudo-random sequence only occurring during said range-bins portion of said decoding signal, and said predeterMined phase relationship providing a cooperative relationship in which said delayed pseudo-random code sequence has an appreciable correlation with the pseudo-random sequence during said range-bins portion of said encoded modulating signal as manifested in said demodulated echo signals only when said moving target has a range within the range bin selected by said range-bins switch, said detection portion of said decoding signal having a second format cooperatively related to said first format of said detection portion of said encoded modulating signal so that with said predetermined phase relationship there is provided a partial but significant amount of correlation during said detection portion of said decoding signal when said moving target has a range within any of said plurality of different range bins, whereby the output from said correlation decoding means includes a relatively-low amplitude doppler-frequency signature signal of a moving target having a range within a given one of the range bins when said given one of said range bins is not selected by said range-bins switch and includes a relatively high-amplitude doppler-frequency signature signal of that moving target when said given one of said range bins is selected by said range-bins switch.

2. The system defined in claim 1, including coarse-range switch means for selectively dividing the maximum range of interest into a plurality of different range subintervals, said coarse-range switch means being coupled to said transmitting means, said range-bins switch means and said decoding signal generating means for selecting a different pair of a group of corresponding pairs of predetermined encoded modulating and decoding signals for each different range subinterval with the plurality of range bins associated with any selected coarse range subinterval being within that selected coarse-range subinterval.

3. The system defined in claim 2, wherein each range-bins portion of the encoded modulating signal of each respective pair includes a first number of contiguous code groups each having the same certain duration and each range-bins portion of the decoding signal of that pair includes a second number of contiguous code groups each having said certain duration and wherein each of the code groups corresponding with at least one relatively closer coarse-range subinterval has a duration smaller than that of each of the code groups corresponding with at least one relatively further coarse-range subinterval.

4. The system defined in claim 3, wherein each cycle of the encoded modulating signal of a pair includes a first half-cycle having serial detection and range bins portions and a second half-cycle which is the invert of said first half-cycle, and each cycle of the decoding signal of that pair has a format during the range-bins and detection portions of the respective first and second half-cycles thereof which have said cooperative relationship to the respective first and second half cycles of said encoded modulating signal of that pair.

5. The system defined in claim 4, wherein the range bins portion of the first half-cycle of an encoded modulating signal includes four contiguous code groups with each of the first three code groups manifesting a given pseudo-random code and the fourth code group manifesting the complement of the given psuedo-random code, wherein the first-half cycle of the range-bins portion of each decoding signal includes two contiguous code groups occurring isochronously with the first two of the four code groups of the corresponding encoded modulating signal, each of the two contiguous code groups of the decoding signal corresponding to the closest range subinterval manifesting the same delayed pseudo-random code and each of the two contiguous code groups of the decoding signal corresponding to each other range subinterval manifesting respective delayed pseudo-random codes which are complements of each other.

6. The system defined in claim 4, wherein the detection portioN of the first-half-cycle of each encoded modulating signal includes contiguous relatively high and relatively low level predetermined time periods of equal duration with respect to each other, with the duration of the time periods of an encoded modulating signal corresponding to a relatively closer range subinterval being shorter than the duration of the time periods of an encoded modulating signal corresponding to a relatively further range subinterval, said first half-cycle of the decoding signal corresponding to each encoded modulating signal including a pair of relatively high and low level time periods of equal duration with respect to each other which occur entirely during the occurrence of each time period of said corresponding encoded modulating signal, each decoding signal being blank during the part of the detection portion thereof which occurs in the absence of said high and low level time periods thereof.