Electronic countermeasure system

• US 4,990,920 A
• Filed: 04/06/1983
• Issued: 02/05/1991
• Est. Priority Date: 04/06/1983
• Status: Expired due to Term

• Current Assignee: Royden C. Sanders
• Original Assignee: Royden C. Sanders
• Inventors: Sanders, Royden C. Jr.
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US06/483,946
• Time in Patent Office: 2,862 Days
• Field of Search: 343/18 R, 343/18 E, 342/13, 342/14, 342/15
• US Class Current: 342/14
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• CPC Class Codes: G01S 7/38 Jamming means, e.g. producing false echoes

Abstract

A radar jamming system comprises a target vehicle and a slave vehicle. A master thread radar detection system is provided in the target vehicle and a slave transmitter system in the slave vehicle with a data link between the target vehicle and the slave vehicle. A threat analyzer is carried by the target vehicle, the threat analyzer being capable of measuring the distances between the target and thread radar as well as between the target and slave vehicle and includes means for calculating a suitable time delay signal and doppler shift for masking the target. The signals are transmitted to said slave vehicle by the data link and means carried by the slave vehicle under control of the data link generate and transmit a radar pulse having the calculated time delay and doppler shift. The signal emitted from the jammer is coincident with the signal reflected from the target in both time and frequency.

Claims

1. A radar jamming system comprising a target vehicle and a slave vehicle, a master threat radar detection system in the target vehicle and a slave transmitter system in the slave vehicle, a data link between the target vehicle and the slave vehicle, a threat analyzer carried by the target vehicle, said threat analyzer being capable of measuring the distance between the target vehicle and slave vehicle, means for calculating a suitable time delay signal and doppler shift for masking the target vehicle, said signals being transmitted to said slave vehicle by said data link, and means carried by said slave vehicle under control of the data link for generating and transmitting a radar pulse having the calculated time delay and doppler shift so that said pulse is coincident in both time and frequency with the target signal.

5. The system of claim 1 wherein the signal emitted from said slave vehicle is coincident at the threat radar with the signal reflected from the target vehicle in both time and frequency so as to mask said target vehicle.

2. An electronic countermeasure system carried by a target vehicle for threat detection and analysis and for control of radar signals to be emitted by a slave vehicle, said system comprising a receiving antenna and several transceiving antennas for receiving one or more separate threat radar signals, means for measuring and calculating with respect to each received signal, the distance between slave vehicle and target vehicle and the difference frequency Df and the time difference of arrival Ddo between the signal which arrives direct from threat radar and the signal which is relayed by the slave vehicle, means for calculating with respect to each threat radar signal the necessary delay and doppler shift of a radar signal sent from the slave to mask the return signal from the target vehicle, and means for transmitting to the slave vehicle appropriate signals regarding delay, doppler shift, bandwidth, gain and center frequency for signal to be transmitted by the slave vehicle so that said pulse is coincident in both time and frequency with the target signal.

3. A master radar countermeasure system comprising means for searching and receiving radar signals from a number of threat radars, means for determining which threat radars are in need of jamming and their order of priority, a separate threat analyzer for each of said threat radars, each threat analyzer being arranged to measure and calculate;

the distance between slave vehicle and target vehicle and the rate of change of the measured distance and means controlled by the threat analyzer for utilizing a slave vehicle containing a jammer, means in the threat analyzer for calculating the shift and delay necessary for the jamming signal so that the jamming signal is coincident with that from the target vehicle in both time and frequency to mask the target signal, and means for transmitting the calculated control signals to the slave vehicle.

4. A slave vehicle radar jamming system carried by a slave vehicle for receiving control signals from a target vehicle, comprising a data link decoder, a variable delay line, a doppler frequency synthesizer and means for combining a predetermined delay and doppler shift to a radar signal to be transmitted from the slave vehicle, said last means being controlled by the data link decoder, said delay and doppler shift providing a signal that is coincident in both time and frequency with the target signal.

6. A Master radar countermeasure system comprising means for searching and receiving radar signals from a number of threat radars, means for determining which threat radars are in need of jamming and their order of priority, a separate threat analyzer for each of said threat radars, each threat analyzer being arranged to measure and calculate:

(a) the distance B between slave vehicle and target vehicle

(b) delay distance Ddo which is the time difference between direct signal arrival and arrival of the signal retransmitted from slave vehicle

(c) rate of change dB/dt of distance between the slave vehicle and target vehicle

(d) difference frequency Df between the direct signal and the signal retransmitted from the slave vehicle

means for transmitting the calculated doppler shifts and delays to the slave vehicle and means on the slave vehicle for retransmitting the received threat radar signal with the same frequency, code, if any, and duration with said calculated doppler shifts and delays superposed on the retransmitted threat radar signal, so that the retransmitted threat radar signal emanating from the slave vehicle appears to the threat radar to be coincident and identical in phase, coding, and time to the reflected threat radar signal from the target vehicle, the signal from the slave being stronger than that from the target and being angularly spaced therefrom.

8. The system of claim 6 wherein Ds, the delay given to the transmitted signal from the slave vehicle jammer so as to mask the signal received from the target vehicle at the threat radar is calculated using the formula:

space="preserve" listing-type="equation">Ds=2B-2Ddo

9. The system of claim 6 wherein Dp, the doppler shift given to the jammer transmission from the slave vehicle so as to match the doppler of the target vehicle as received by the threat radar is calculated using the formula:

space="preserve" listing-type="equation">Dp=dB/dt-Df

10. The system of claim 6 wherein C, the distance between the target vehicle and the threat radar is calculated using the formula:

space="preserve" listing-type="equation">C=Ddo(2B-Ddo)/[2B(Cos<

A-1)+2Ddo]

where A is the angle measured from the target vehicle between the threat radar and the slave vehicle.

11. System of claim 6 wherein Ds and Dp are calculated using the formulas:

space="preserve" listing-type="equation">Ds=2B-2Ddo ##EQU1##

12. The system of claim 6 which additionally includes means for continuously monitoring the radar signal retransmitted from the slave, said means including means for subtracting Ds and Ddf to permit continuous measurement of Df and Ddo and means for calculating with respect to each threat radar signal the shift in doppler (Ds) and the time delay (Ddf) of a radar signal sent from the slave to provide a signal which is coincident with that from the target in both time and frequency but at a false angle so as to mask the target signal.

7. An electronic countermeasure system carried by a target vehicle for threat detection and analysis and for control of radar signals to be emitted by a slave vehicle, said system comprising a receiving antenna and several transceiving antennas for receiving one or more separate threat radar signals, means for measuring with respect to each received signal:

(a) the difference in time (Ddo) for the transmitted threat radar pulse to reach the target vehicle directly as compared to that retransmitted by the slave vehicle

(b) the doppler (dB/df) in the signal from the slave vehicle to the target vehicle

(c) the angle (<

A) between slave vehicle and threat radar as measured from target vehicle

(d) the difference frequency (Df) between signals which arrive directly from the threat radar and the signal retransmitted from the slave vehicle means for calculating Dp and Ds and C using the following equations;

Calculate Ds using the formula Ds=2B-2Ddo

Calculate Dp using the formula Dp=dB/dt-Df

Calculate the distance C by using the following formula

space="preserve" listing-type="equation">C=Ddo(2B-Ddo)/[2B(Cos<

A-1)+2Ddo]

Where;

Dp is the doppler shift given to the jammer transmission from the slave vehicle so as to match the doppler of the target vehicle as received by the threat radar

Ds is the delay given to the transmitted signal from the slave vehicle jammer so as to mask the signal received from the target vehicle at the threat radar

C is the distance between the target vehicle and the threat radar

the transmitted signal from the slave vehicle being coincident in both time and frequency with the target signal.