Radar with adaptive range sidelobe suppression

• US 5,481,270 A
• Filed: 03/04/1994
• Issued: 01/02/1996
• Est. Priority Date: 03/04/1994
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Martin Marietta Corporation
• Inventors: Bucci, Nicholas J., Freedman, Jerome E., Urkowitz, Harry
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US08/205,471
• Time in Patent Office: 669 Days
• Field of Search: 342/39, 342/101, 342/109, 342/128, 342/129, 342/130, 342/131, 342/132, 342/134, 342/135, 342/136, 342/145, 342/146, 342/159, 342/162, 342/195, 367/905
• US Class Current: 342/101
• CPC Class Codes: G01S 13/28 with time compression of received pulses
• CPC Class Codes: G01S 13/582 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 13/95 for meteorological use
• CPC Class Codes: G01S 7/411 Identification of targets based on measurements of radar reflectivity G01S7/415 takes precedence
• CPC Class Codes: G01S 7/415 Identification of targets based on measurements of movement associated with the target
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
• CPC Class Codes: Y10S 367/905 Side lobe reduction or shading

Abstract

A method and apparatus for identifying a remote target includes a transmitter for transmitting pulses of energy toward the target for generating echo signals, and a receiver for receiving the echo signals, and for generating received signals representing the target, noise and clutter. The received signals are applied through a plurality of cascaded channels, each including a Doppler filter cascaded with a multiplier, each also including range sidelobe suppression, for, in each of the cascaded channels, narrowband filtering the signals passing therethrough about a controllable center frequency, and for, if necessary, converting the signals passing therethrough to baseband, for thereby applying one of a plurality of Doppler filtered baseband signals to the input of each of the range sidelobe suppressors of each of the cascaded channels. The power of the Doppler filtered baseband signals in each range bin is evaluated for determining the frequency at which the spectral density is greatest. The center frequency of at least one of the cascaded Doppler channels is controlled such that one of the Doppler channels has its center frequency at the maximum-power frequency.

Claims

1. A radar system, comprising;

transmitting means for transmitting pulses of energy toward a target, for generating echo signals;

receiving means for receiving said echo signals, for generating received signals;

a plurality of Doppler filters, each of which is cascaded with a multiplier for forming a like plurality of cascaded channels, each of said cascaded channels including a received signal input port, a signal output port, and a frequency control signal input port, said received signal input port of each of said cascaded channels being coupled to said receiving means for receiving said received signals therefrom, for, in each of said channels, narrowband filtering the signals passing therethrough about a center frequency controllable in response to a frequency control signal, and for, if necessary, converting said signals passing therethrough to baseband, for thereby generating one of a plurality of Doppler filtered baseband signals at said output port of each of said cascaded channels, each of which Doppler filtered baseband signals is representative of a different range of target velocities;

signal processing means coupled to said signal output port of each said plurality of Doppler filters for receiving said Doppler filtered baseband signals therefrom, and for processing said Doppler filtered baseband signals for determining which range bin has the greatest amplitude attributable to echo signals, and for determining said amplitude, to thereby generate maximum reflectivity signals;

Doppler power spectrum determining means coupled to said signal processing means for receiving said maximum reflectivity signals therefrom, for generating an estimate of the power spectrum of said maximum reflectivity signals to determine a maximum-power frequency; and

control means coupled to said Doppler power spectrum determining means and to said plurality of cascaded channels, for generating and applying said frequency control signal to said frequency control input port of at least one of said cascaded channels, for controlling said cascaded channels such that at least said one of said cascaded channels has its said center frequency at said maximum-power frequency.

2. A radar system according to claim 1, wherein said cascaded channels comprise digital signal processing means controllable by coefficients, and said control means comprises:

memory means preprogrammed with sets of information, each set representing coefficients which establish a unique response of one of said cascaded channels.

3. A method for identifying a remote target, comprising the steps of:

transmitting pulses of energy toward said target, for generating echo signals;

receiving said echo signals, for thereby generating received signals organized into range traces;

applying said received signals through a plurality of Doppler filters, each of which iS cascaded with a multiplier to thereby form a like plurality of cascaded channels, for, in each of said channels, narrowband filtering the signals passing therethrough about a controllable center frequency, and for, if necessary, converting said signals passing therethrough to baseband, for thereby generating one of a plurality of Doppler filtered baseband signals at the output of each of said cascaded channels, each of which Doppler filtered baseband signals is a range trace representative of a different interval of target velocities;

determining, for each range trace of each of said Doppler filtered baseband signals, at least that one range bin of said range trace which has the greatest amplitude attributable to echo signals, and generating an amplitude signal representative thereof;

generating an estimate of the power spectrum of said amplitude signals of said one range bin to determine a maximum-power frequency; and

controlling said cascaded channels such that at least said one of said cascaded channels has its said center frequency at said maximum-power frequency.