CW radar range measuring system with improved range resolution

• US 5,999,119 A
• Filed: 12/18/1996
• Issued: 12/07/1999
• Est. Priority Date: 12/18/1996
• Status: Expired due to Term

• Current Assignee: Valeo Radar Systems, Inc. (Valeo SE)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Marquis, David A, Shollenberger, Dean L, Carnes, deceased, I. Shaun, Russell, Mark E
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US08/768,388
• Time in Patent Office: 1,084 Days
• Field of Search: 342/145, 342/189, 342/162, 342/85, 342/135, 342/192, 342/196, 342/21
• US Class Current: 342/135
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/584 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 7/35 Details of non-pulse systems

Abstract

A CW radar range measuring system having a transmitter adapted to transmit a continuous wave radar signal phase encoded in accordance with a code and a receiver adapted to receive a radar return from the transmitted radar signal. The receiver includes an analog to digital converter section for converting a sequence of samples of the radar return into a corresponding sequence of digital words. A digital correlator/integrator is fed by the digital words and the code for providing an indication of radar return energy as a function of range from the transmitter. A processor is fed by the digital correlator/integrator for determining, from the indicated energy, target range. The system includes a frequency spectrum analyzer for determining a frequency spectrum of the digital words and wherein the processor determines the target Doppler frequency from such determined frequency spectrum. In one embodiment of the invention, the digital correlator/integrator is fed the digital words and the frequency analyzer is coupled between the digital correlator/integrator and the processor. In another embodiment of the invention the frequency analyzer is fed the digital words and the digital correlator/integrator is coupled between the frequency analyzer and the processor. In still another embodiment, target range may be determined to an accuracy less than that corresponding to a time delay of 1/f_s, the rate the at which the phase of the transmitted signal is phase encoded.

Claims

1. A CW radar range measuring system, comprising:

a transmitter for transmitting a continuous wave radar signal phase encoded in accordance with a transmit code;

an analog to digital converter section for converting a sequence of samples of the radar return into a corresponding sequence of digital words;

a receiver adapted to receive a radar return from the transmitted radar signal, such receiver comprising;

a receive code generator for storing a replica of the transmit code and for producing differently time delayed replica of such transmit code, such differently time delayed replica being produced a predetermined time after the phased encoded radar signal is transmitted;

a digital correlator/integrator fed by the digital samples produced by the analog to digital converter and the receive code produced by the receive code generator, for generating a plurality of range channels and for providing an indication of radar return energy as a function of range from the transmitter for each of the channels.

2. A CW radar range measuring system, comprising:

a transmitter for transmitting a continuous wave radar signal phase encoded in accordance with a transmit code stored in a transmitter code generator, such transmit code phase encoding the transmitted continuous wave signal at a predetermined rate, f_s, such rate f_s being produced by a source adapted to generate clock pulses at a rate Pf_s and dividing the rate produced by the clock pulse source to a rate f_s, where P is an integer greater than 1;

a receiver adapted to receive a radar return from the transmitted radar signal, such receiver comprising;

a time delay circuit, fed by a digital word representative of a desired time delay, Δ

, and the clock pulses produced by the clock pulse source, for producing at an output thereof the clock pulses produced by the clock pulse generator delayed in time by the desired time delay, Δ

, such desired time delay, Δ

, being equal to S/(Pf_s), where S is an integer less than (P-1);

a receive code generator for storing a replica of the transmit code and for producing differently time delayed replica of such transmit code in response to the clock pulses produced at the output of the time delay circuit;

an analog to digital converter section, responsive to the clock pulses produced at the output of the time delay circuit, for converting a sequence of samples of the radar return into a corresponding sequence of digital words at the rate f_s ;

a digital correlator/integrator fed by the digital words and the receive code produced by the receive code generator, for providing an indication of radar return energy as a function of range from the transmitter.

3. A CW range measuring system comprising:

a transmitter for transmitting a continuous wave radar signal phase encoded in accordance with a transmit code stored in a transmitter code generator, such transmit code phase encoding the transmitted continuous wave signal at a predetermined rate, f_s, such rate f_s being produced by a source adapted to generate clock pulses at a rate Pf_s and dividing the rate produced by the clock pulse source to a rate f_s, where P is an integer greater than 1;

a receiver adapted to receive a radar return from the transmitted radar signal, such receiver comprising;

a time delay circuit, fed by a digital word representative of a desired time delay, Δ

, and the clock pulses produced by the clock pulse source, for producing at an output thereof the clock pulses produced by the clock pulse generator delayed in time by the desired time delay, Δ

, such desired time delay, Δ

, being equal to S/(Pf_s), where S is an integer less than (P-1);

a receive code generator for storing a replica of the transmit code and for producing differently time delayed replica of such transmit code in response to the clock pulses produced at the output of the time delay circuit;

an analog to digital converter section, response to the clock pulses produced at the output of the time delay circuit, for converting a sequence of samples of the radar return into a corresponding sequence of digital words at the rate f_s ;

a digital correlator/integrator fed by the digital works and the receive code produced by the receive code generator, for generating a plurality of range channels and for providing an indication of radar return energy as a function of range from the transmitter for each of the range channels.