Communications: directive radio wave systems and devices (e.g. – Return signal controls radar system – Receiver
Reexamination Certificate
1999-12-13
2001-10-02
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls radar system
Receiver
C342S014000, C342S027000, C342S028000, C342S089000, C342S091000, C342S093000, C342S175000, C342S098000, C342S099000, C342S104000, C342S115000, C342S165000, C342S194000, C342S195000, C342S196000
Reexamination Certificate
active
06297764
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of radar, and more particularly, this invention relates to the field of processing radar signals to determine Doppler information.
BACKGROUND OF THE INVENTION
Electronic counter-measure receivers for training systems may be collocated with a radar transmitter. For pulse-Doppler and CW radar modes, the received signal is usually detected using a matched filter to maximize the probability of detection and processed through fast Fourier transform circuitry to provide Doppler information. The ideal matched filter is a time reversed copy of a transmitted pulse. The CW typically requires a separate and narrower channel and the ideal matched filter is a large fast Fourier transform circuitry with a long data record. Typically, the different modes, such as pulse-Doppler, pulse and CW, required different receiver designs of varying complexity. Thus, an additional cost was added when different modes were processed.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a radar receiver that can be colocated with a threat simulator radar, permit characterization of an aircraft's response, and use pulse-Doppler, pulse and CW modes.
The radar receiver of the present invention is an ECM receiver that can be colocated with a threat simulator radar, which will illuminate the target aircraft. The receiver permits characterization of the aircraft's response to a simulated threat radar signal.
The ECM receiver is provided with target location information from an IFF tracking system to keep it on target even under heavy counter-measures. The receiver is capable of processing CW, pulse and pulse-Doppler radar signals and their associated counter-measures. In particular, the counter-measures of interest are range gate pull-off (RGPO), velocity gate pull-off (VGPO), noise ECM and amplitude modulation of the pose ECM.
The radar receiver uses a sampled transmit signal to form a matched filter for signal detection. This provides several unique advantages, including nearly optimal detection, guaranteed coherence, and allows the use of better leakage and clutter rejection filters.
The pulse-Doppler radar receiver is blanked during transmit to protect the receiver front-end. The receiver uses that window of time to sample the transmit pulse for use as a reference for detection. The blanking is controlled by a blanking pulse that rises just prior to the start of transmit and falls shortly after the transmit pulse ends. This blanking pulse is made available to the ECM receiver and is used to switch both the front end and the signal processing chain between sampling the transmit signal and listening for the actual received signal.
The sampling is accomplished via an RF switch, and in one aspect of the present invention, an attenuator protects the receiver. The sampled signal is routed through the same signal path that the received signal will follow. The sampled RF transmit signal is first mixed to a 70 MHz IF and then digitized by an analog-to-digital converter (ADC). The sample rate is chosen to be 60 MHz so that the 70 MHz IF is aliased down to 10 MHz (with the higher frequency products removed by DDC filters). The signal is then digitally mixed with a local oscillator (LO) in quadrature to shift the signal to baseband. The local oscillator can be 10 MHz. The actual signal may be slightly shifted from baseband if any of the aforementioned frequencies are not exact. At this point, the data is conjugated, reversed in time, and then stored as the complex coefficients of the receivers matched FIR filter.
When the blanking pulse ends, the RF front-end is switched back to the antenna to listen for the signal. The switching of the DDC output is delayed to account for the signal path processing delay up to that point. Once the end of the blanking pulse passes through the delay, the output of the DDC is switched to the receive path and all of the DDC registers and buffers are cleared of any extraneous data.
The received data then follows the same signal path and upon exiting the DDC is routed into the FIR filter that is comprised of the processed transmit data samples. Since both the received data and the filter coefficients are processed through the same signal path, any residual frequency offset (from DC) will cancel, leaving the final signal that is truly baseband.
For application to the CW mode, the same processing chain is used. The primary difference is that an internal timing generator is used because there is no blanking pulse available since the transmitter is always transmitting. The other change is that the resulting range Doppler map is actually just a range-time map, which can be detected and integrated over time with no loss of information.
REFERENCES:
patent: 3987285 (1976-10-01), Perry
patent: 4266279 (1981-05-01), Hines
patent: 4622552 (1986-11-01), Andrews et al.
patent: 4635061 (1987-01-01), Lepere et al.
patent: 5151702 (1992-09-01), Urkowitz
patent: 5376939 (1994-12-01), Urkowitz
patent: 5440311 (1995-08-01), Gallagher et al.
patent: 5539412 (1996-07-01), Mendelson
patent: 5557560 (1996-09-01), Dix et al.
patent: 5784026 (1998-07-01), Smith et al.
Rhoa James
Seybold John S.
Wormington Terry
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Gregory Bernarr E.
Harris Corporation
LandOfFree
Radar receiver having matched filter processing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radar receiver having matched filter processing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radar receiver having matched filter processing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597353