Pulse-Doppler Radar Mutual Interference Processor

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Solution Overview

Problem

Radar systems, particularly pulse-Doppler radars, face significant challenges in suppressing mutual interference from nearby sensors, which leads to increased false alarm rates and reduced target detection sensitivity due to the masking of intended target signals by pulsed interference and clutter signals.

Innovation Solution

A method that generates measurement and correction signals to characterize and subtract pulsed interference from received energy signals, maintaining radar target detection sensitivity by processing these signals to isolate and remove interference while preserving clutter suppression capabilities of pulse-Doppler filters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If pulse-Doppler filters are used to suppress clutter signals, then clutter suppression capability is improved, but pulsed interference masks target signals and degrades detection sensitivity

Engineering Contradiction:

Improveclutter suppression capabilityVSAvoidtarget detection sensitivity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent segments the interference removal process into two distinct signal processing paths: one path (using measurement signals with clutter frequencies set to zero) estimates pulsed interference free of clutter, while another path (using correction signals) handles the complete interference including clutter frequencies. This segmentation allows each path to be optimized for its specific function, enabling effective interference removal without degrading clutter suppression capability.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If blanking is used to remove pulsed interference, then pulsed interference is effectively removed, but portions of clutter signals are also blanked and detection sensitivity is degraded

Engineering Contradiction:

Improvepulsed interference removalVSAvoiddetection sensitivity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent extracts the pulsed interference component from the received signals through correlation processing with measurement and correction signals. Instead of blanking (removing) portions of the signal, the interference is separated and subtracted, allowing the desired target and clutter signals to remain intact for subsequent processing by pulse-Doppler filters.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces measurement signals and correction signals as intermediary elements that facilitate the removal of pulsed interference. These intermediary signals are generated by correlating received signals with reference waveforms, and they enable the selective cancellation of interference without directly affecting the target or clutter signals.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If pulse-Doppler waveforms consist of long sequences of high-energy pulses, then radar resources are increased, but mutual interference becomes more likely and more resources are rendered useless

Engineering Contradiction:

Improveradar energy resourcesVSAvoidmutual interference susceptibility

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent employs feedback mechanisms where measurement signals are generated from the received signals themselves through correlation processing. This feedback loop allows the system to continuously adapt and remove interference in real-time, protecting the invested radar energy resources from being wasted due to mutual interference during long pulse sequences.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively reduces or removes pulsed interference, maintaining radar target detection sensitivity even in conditions with combined clutter and pulsed interference, without degrading the ability to suppress clutter signals.

Implementation Method 1

Radar (including sonar and lidar) has been known and used by man for 60 years or more

Methodology Applied

Scientific EffectRadar: Radar

Implementation Method 2

Pulse-Doppler radars use pulse-Doppler filters to convert the time-domain reflected radar signals to the frequency domain

Methodology Applied

Scientific EffectDoppler effect: Doppler Effect

Data Source

PatentUS7375676B1Mutual interference processor for pulse radar

Publication Date: 2008.05.20 LOCKHEED MARTIN CORP

AI summary

Pulsed or mutual interference in a pulse radar system is ameliorated by a process that includes a pulse-Doppler filter, some frequency bins of which correlate with clutter. Pulsed interference is identified, and the corresponding column vectors of a pulse-Doppler-filter-equivalent matrix are identified. The row values of the corresponding interference-affected column vectors that correlate with clutter are nulled. The vectors are orthogonalized, and then converted to measurement and correction signal vectors for application to the pulse-Doppler received signals. Vector dot products of the measurement signal vectors with the received signals are calculated, to produce pulsed interference measurements that are nominally free of clutter. The pulsed interference measurements are combined with the correction signals which are then subtracted from the received signals to produce signals that are nominally free of pulsed interference. In one embodiment, the pulsed interference-free received signals are applied to a pulse-Doppler filter to suppress the clutter signals.