Compensation for radar path length variation and phase error

• US 5,952,955 A
• Filed: 12/23/1997
• Issued: 09/14/1999
• Est. Priority Date: 12/23/1997
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Kennedy, Thomas A., Rosen, Robert A., Krikorian, Kapriel V., Robertson, Ralston S., Hulderman, Garry N.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/997,521
• Time in Patent Office: 630 Days
• Field of Search: 342/25, 342/102, 342/159, 342/161, 342/162, 342/165, 342/173, 342/174, 342/194, 342/195, 342/198, 342/203
• US Class Current: 342/25.00F
• CPC Class Codes: G01S 13/90 using synthetic aperture techniques , e.g. synthetic aperture radar [SAR] techniques
• CPC Class Codes: G01S 7/4021 of receivers

Abstract

Methods that compensate for phase errors caused by path length variations in a radar system, and that compensate for relative phase errors in upconvertor and downconverter references employed in the radar system. One method samples a signal reflected from a duplexer through a receiver during the time the radar pulse is transmitted. The signal reflected from the duplexer is compared to a radar echo pulse on a single pulse basis. The phase of the sampled signal is subtracted from the phase of the received radar echo pulse reflected to determine the phase error. In a second method, multiple samples are collected during the time each radar pulse is transmitted. Samples of the signal reflected from the duplexer and the radar echo pulse are compared on a pulse to pulse basis. The phase differences are averaged across the pulse duration. The averaged phase differences are integrated on a pulse to pulse basis to determine the phase error.

Claims

1. A signal processing method for use with a radar system compromising a duplexer 18 that couples transmitted radar pulses between a transmitter and an antenna 19 and between the antenna and a receiver that compensates for radar path length variations and phase errors, said method comprising the steps of:

sampling a signal reflected from the duplexer through the receiver 30 during the time the radar pulse is transmitted;

comparing the signal reflected from the duplexer to the radar echo pulse on a single pulse basis; and

subtracting the phase of the sampled signal from the phase of the received radar echo pulse reflected from a target to determine the phase error.

2. The method of claim 1 further comprising the step of:

filtering a plurality of pulses after the comparison step to reduce the noise on the signal reflected from the duplexer and to determine a smoothed estimate of the phase error.

3. A signal processing, method for use with a radar system comprising a duplexer that couples transmitted radar pulses between a transmitter and an antenna and between the antenna and a receiver that compensates for radar path length variations and phase errors, said method comprising the steps of:

collecting multiple samples during the time each radar pulse is transmitted;

comparing samples of the signal reflected from the duplexer and the radar echo pulse on a pulse to pulse basis;

averaging the phase differences across the pulse duration; and

integrating the averaged phase differences on a pulse to pulse basis to determine the phase error.

4. The method of claim 3 further comprising the step of:

filtering a plurality of pulses after the comparison step to reduce the noise on the signal reflected from the duplexer and to determine a smoothed estimate of the phase error.