Method for reducing false alarm rate in radar images

• US 6,765,525 B2
• Filed: 02/21/2003
• Issued: 07/20/2004
• Est. Priority Date: 02/22/2002
• Status: Expired due to Term

• Current Assignee: Airbus Defence and Space GmbH
• Original Assignee: EADS Deutschland GmbH (Airbus SE)
• Inventors: Bickert, Bernhard, Meyer-Hilberg, Jochen
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US10/370,111
• Publication Number:
  US 20030210175A1
• Time in Patent Office: 515 Days
• Field of Search: 342/90, 342/93, 342/104, 342/114, 342/155, 342/159, 342/160, 342/162, 342/195
• US Class Current: 342/160
• CPC Class Codes: G01S 13/5242 with means for platform motion or scan motion compensation, e.g. airborne MTI
• CPC Class Codes: G01S 13/5244 Adaptive clutter cancellation specially adapted for airborne MTI, G01S13/5242
• CPC Class Codes: G01S 7/2927 by deriving and controlling a threshold value

Abstract

A method for reducing the false alarm rate, i.e. the number of alarms of fixed targets erroneously declared as moving targets in the radar images of two- or multi-channel MTI radar devices, wherein the suppression of fixed target echoes over the moving target echoes within the main antenna lobe occurs through a space time adaptive processing—STAP—filter. The method uses a comparison of the amplitude amounts or power values of the range Doppler frequency cells with a threshold that can be specified in constant terms and summary of the resulting alarms. A target function is compared with defined test functions and selection criteria are determined from suitable combined calculation methods that are applied to the test and target functions for the purpose of classifying a respective target alarm as a moving or fixed target alarm.

Claims

1. A method for reducing the false alarm rate produced by the number of alarms of fixed targets erroneously declared as moving targets in the radar images of two- or multi-channel MTI radar devices, comprising the steps of:

providing and using a space time adaptive processing filter in a visible side antenna lobe in the radar image for the suppression not fixed targets in the side antenna lobe,

comparing amplitude amounts or power values of range Doppler frequency cells with a threshold specified in constant terms and summing of resulting alarms from said comparison, wherein only those alarms whose amplitude amounts or power values are above the specified threshold are used and combined into clusters, wherein first a summary of alarms that is directed in a direction of the Doppler frequency into Doppler frequency clusters occurs based on their minimal distance to each other and subsequently a summary of Doppler frequency clusters that is directed in a distance direction into range Doppler frequency clusters occurs based on their minimal distance to each other,

comparing a target function with a test function, wherein the test function is an intersecting function of a two-dimensional characteristic function of the amplitude and phase progressions of a main antenna lobe as a function of the Doppler frequency and the target function is a characteristic function, calculated for each alarm, of the amplitude and phase progressions of a respective target as a function of the Doppler frequency on the Doppler frequency position of the respective target, and

determining selection criteria from suitable combined calculation methods that are applied to the test and target functions for the purpose of classifying a respective target alarm as a moving or fixed target alarm.

2. The method according to claim 1, wherein the constant specified threshold is determined from the mean value and the variance of the amplitudes or power values of all range Doppler frequency cells.

3. The method according to claim 1, wherein the two-dimensional characteristic function of the amplitude and phase progressions of the main antenna lobe is calculated pursuant to

4. The method according to claim 1, wherein for each target alarm, the characteristic function of the amplitude and phase progressions of the respective target are calculated pursuant to

5. The method according to claim 3, wherein the test function is a one-dimensional function pursuant to an intersection with f′

= constant from the two-dimensional characteristic function X_char(f, f′

).

6. The method according to claim 1, further comprising the steps of;

completing in a parallel step, a correlation of the target function with the test functions; and

pursuant to the least mean square—

LMS—

, approaching the least error square between the target and the test functions.

7. The method according to claim 6, comprising the further step of;

from the correlation function and the result of the computation pursuant to the LMS approach, extracting the following four selection criteria for the classification of a target as a moving target or fixed target;

1. the target speed estimated from the distance between the detected Doppler frequency position f₂ and the absolute position of the minimum of the LMS approach for the respective target,

2. the amplitude of the maximum of the correlation function,

3. the amplitude of the minimum of the LMS approach,

4. the distance of the position of the maximum of the amount of the correlation function and the position of the minimum of the logarithmized amplitude of the LMS approach.

8. The method according to claim 7, wherein each selection criterion is weighted with a specified probability value P_i, with which the identified target is a moving target.

9. The method according to claim 8, wherein the overall probability value P_Gesamt resulting from the individual specified probability values P_i is compared to a threshold value.

10. A method for reducing a false alarm rate in a system for detecting moving targets from radar images, comprising the steps of:

analyzing a visible side antenna lobe in a radar image by a time adaptive processing filter in order to suppress fixed targets in the side antenna lobe;

comparing values of range Doppler frequency cell with a specified threshold value;

providing an indication of alarms resulting from said step of comparing and summing said indicated alarms;

providing a summary of alarms directed in a direction of the Doppler frequency and providing Doppler frequency clusters based on their minimal distance to each other;

providing a summary of Doppler frequency clusters directed in a distance direction based on their minimal distance to each other;

comparing a target function with a test function, wherein said test function is an intersecting function of a 2-dimensional characteristic function of amplitude and phase progressions of a main antenna lobe as a function of the Doppler frequency and wherein the target function is a characteristic function, calculated for each alarm, of the amplitude and phase progressions of a respective target as a function of the Doppler frequency on the Doppler frequency position of the respective target; and

determining selection criteria from a suitable combined calculation method applied to the test and target functions in order to classify respective target alarms as a moving or fixed target alarm.