Processing method using an advanced waveform for unlocked coherent and wideband bistatic radar operation

• US 5,959,573 A
• Filed: 05/22/1998
• Issued: 09/28/1999
• Est. Priority Date: 05/22/1998
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Rosen, Robert A., Krikorian, Kapriel V.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US09/083,457
• Time in Patent Office: 494 Days
• Field of Search: 342/90, 342/147, 342/195, 342/196, 342/97, 342/95
• US Class Current: 342/90
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/24 using frequency agility of carrier wave
• CPC Class Codes: G01S 7/288 Coherent receivers
• CPC Class Codes: G01S 7/36 Means for anti-jamming , e.g. ECCM, i.e. electronic counter-counter measures

Abstract

A bistatic coherent unlocked radar system and processing method using an advanced waveform that permits bistatic unlocked coherent operation of an unlocked radar transmitter and receiver. The waveform implements intrapulse fine range resolution, pulse to pulse coherency and burst to burst frequency agility to provide for enhanced target detection and robust operation in electronic countermeasure environments. A continuous sequence of pulses at different frequencies is transmitted that may contain an acquisition frequency that is revisited) more times than the other frequencies. Energy reflected from a target is processed to detect energy at the acquisition frequency, for example, over a plurality of range bins and predetermined pulse repetition intervals. A range pattern is generated if the detected energy is above a predetermined threshold. The energy is centroided to indicate the relative angle to the target. The transmitted frequencies contained in the pattern of energy are identified. The receiver then frequency hops with the transmitter. The energy is coherently processed using Fourier transforms to determine the center in the pattern, which pattern center is indicative of the direction to the target.

Claims

1. A method for detecting a target using an unlocked transmitter and receiver of a bistatic radar system, comprising the steps of:

transmitting a continuous sequence of pulses containing predetermined sets of frequencies;

receiving energy transmitted by the transmitter and reflected from a target;

rejecting direct path energy received from the transmitter;

detecting the received reflected energy at the acquisition frequency over a plurality of range bins and over a predetermined pulse repetition intervals;

generating a range pattern if the detected energy is above a predetermined threshold;

determining a centroid that is indicative of the relative angle of the target once sufficient energy is collected in the range bins;

identifying frequencies in the pattern of energy within the region of interest;

frequency hopping with the frequencies transmitted by the transmitter; and

coherently processing the energy to determine the center in the pattern, which pattern center is indicative of the direction to the target.

2. The method of claim 1 wherein the step of transmitting a continuous sequence of pulses comprises transmitting a continuous pulse compressed sequence of pulses.

3. The method of claim 1 wherein an acquisition frequency is transmitted more times than the other frequencies to provide for improved acquisition.

4. The method of claim 1 wherein the step of detecting the received reflected energy comprises the step of scanning a receive beam in a direction toward the target.

5. The method of claim 1 wherein the step of coherently processing the energy comprises the step of coherently processing the energy using Fourier transforms.

6. A bistatic coherent unlocked radar system for tracking a target, comprising:

a transmitter for transmitting a continuous sequence of pulses containing predetermined sets of frequencies; and

a receiver that receives energy that is transmitted by the transmitter and that is reflected from target, that rejects direct path energy received from the transmitter, that detects the received reflected energy at the acquisition frequency over a plurality of range bins and over a predetermined pulse repetition intervals, that generates a range pattern if the detected energy is above a predetermined threshold, that determines a centroid that is indicative of the relative angle of the target once sufficient energy is collected in the range bins, that identifies frequencies in the pattern of energy within the region of interest, that frequency hops with the frequencies transmitted by the transmitter, and that coherently processes the energy to determine the center in the pattern, which pattern center is indicative of the direction to the target.

7. The system of claim 6 wherein the transmitter transmits a continuous pulse compressed sequence of pulses.

8. The system of claim 6 wherein the transmitter transmits an acquisition frequency more times than the other frequencies to provide for improved acquisition.

9. The system of claim 6 wherein the receiver detects the received reflected energy by scanning a receive beam in the vicinity of the target.

10. The system of claim 6 wherein the receiver coherently processes the energy using Fourier transforms.