Signal processing method for FM-CW radar

• US 7,579,981 B2
• Filed: 01/02/2008
• Issued: 08/25/2009
• Est. Priority Date: 12/26/2003
• Status: Expired due to Fees

• Current Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Original Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Inventors: Kishida, Masayuki
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Barker; Matthew M
• Application Number:
  US11/968,577
• Publication Number:
  US 20080117095A1
• Time in Patent Office: 601 Days
• Field of Search: 342/109
• US Class Current: 342/109
• CPC Class Codes: G01S 13/345 using triangular modulation

Abstract

Disclosed is a signal processing method for an FM-CW radar that can accurately detect the relative distance, relative velocity, etc. with respect to a target approaching or receding at a high relative velocity, wherein predicted values for peak frequencies currently detected in upsweep and downsweep sections are computed from the previously detected relative distance and relative velocity, and it is determined whether any of the predicted values exceeds a detection frequency range and, if there is a peak frequency that exceeds the detection frequency range, the frequency is folded and the folded frequency is taken as one of the predicted values, the method then proceeding to search the currently detected peak frequencies to determine whether there are upsweep and downsweep peak frequencies approximately equal to the predicted values and, if such upsweep and downsweep peak frequency are found, the peak frequency approximately equal to the folded predicted value is folded and the folded peak frequency is used.

Claims

1. A signal processing method for an FM-CW radar which determines a relative distance and a relative velocity with respect to a target from peak frequencies occurring in an upsweep section and a downsweep section of a triangular FM-CW wave wherein,

when said target is a target that has previously been detected, predicted values for the peak frequencies currently detected in the upsweep and downsweep sections are computed from the relative distance and relative velocity previously detected with respect to said target, and it is determined whether any of said predicted values exceeds a detection frequency range, and if there is a peak frequency that exceeds said detection frequency range, said frequency is folded and said folded frequency is taken as one of said predicted values, said method then proceeding to search the currently detected peak frequencies to determine whether there are upsweep and downsweep peak frequencies substantially equal to said predicted values, and if said substantially equal frequencies are found, said found frequencies are folded and said folded frequencies are used to determine the relative distance and the relative velocity.

2. A signal processing method for an FM-CW radar as claimed in claim 1 wherein, in the case of a peak frequency for which a predicted value is negative, said predicted value is inverted in sign and taken as one of said predicted values, said method then proceeding to search the currently detected peak frequencies to determine whether there are upsweep and downsweep peak frequencies approximately equal to said predicted values, and if said upsweep and downsweep peak frequencies are found, said found frequencies are inverted in sign and then used to determine the relative distance and the relative velocity.

3. A signal processing method for an FM-CW radar as claimed in claim 1 wherein, in the case of a peak frequency for which a predicted value exceeds an upper limit frequency of said detection frequency range, said peak frequency is folded with respect to said upper limit frequency and said folded peak frequency is taken as one of said predicted values, said method then proceeding to search the currently detected peak frequencies to determine whether there are upsweep and downsweep peak frequencies substantially equal to said predicted values, and if said upsweep and downsweep peak frequencies are found, said found frequencies are folded with respect to said upper limit frequency and said folded peak frequencies are used to determine the relative distance and the relative velocity.