Subaperture Clutter Filter for SAR Communication Signal Detection

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Solution Overview

Problem

Synthetic aperture radar (SAR) systems face interference from radar clutter, which can degrade communication signal performance by appearing as noise or interference, making it difficult to distinguish and extract communication signals from received signals containing both radar clutter and communication data.

Innovation Solution

A method involving the generation of subapertures from received signals, where one subaperture contains only radar clutter and another contains both radar clutter and a communication signal, allowing for the filtering of radar clutter based on the radar signature to identify and extract the communication signal, utilizing band-limited communication transmitters and deramp processing to separate the signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If radar systems transmit electromagnetic radiation for both SAR imaging and RF communication simultaneously, then the radar antenna can perform dual functions of imaging and communication, but the radar clutter return appears as noise or interference on the communication channel, degrading communication performance

Engineering Contradiction:

Improvedual-function capabilityVSAvoidcommunication channel performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The received signal is divided into multiple subapertures, where the first subaperture contains only radar clutter and the second subaperture contains the communication signal mixed with radar clutter. This segmentation allows separate processing of clutter and signal components to improve communication detection reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The radar clutter component is extracted from the received signal by processing the first subaperture separately, then this extracted clutter is used to filter the second subaperture. This extraction approach removes the harmful clutter interference while preserving the communication signal.

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If the communication signal uses the same frequency as the radar transmission signal, then the radar antenna can receive both radar return and communication signal simultaneously, but it becomes difficult to distinguish and extract the communication signal from the received signal containing both radar clutter and communication data

Engineering Contradiction:

Improvefrequency reuse capabilityVSAvoidsignal discrimination difficulty

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The problem is solved by transitioning from frequency-domain separation to time-domain or spatial-domain separation through subaperture division. By dividing the received signal into different subapertures with different temporal or spatial characteristics, the patent enables signal discrimination despite frequency overlap between radar and communication signals.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Different subapertures are assigned different processing characteristics - the first subaperture is processed to extract pure clutter characteristics, while the second subaperture is processed with clutter filtering to reveal the communication signal. This local quality differentiation enables effective signal detection.

Inventive Principle:

Principle #3Local quality

3Productivity

If radar clutter is present in the received signal, then the radar system can perform normal SAR imaging, but the clutter degrades communication signal detection by appearing as noise or interference

Engineering Contradiction:

ImproveSAR imaging capabilityVSAvoidcommunication signal detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The radar clutter, which was previously harmful to communication detection, is converted into a useful resource. By extracting the clutter characteristics from the first subaperture and using them to filter the second subaperture, the patent transforms the harmful clutter into a reference signal that enables effective communication signal detection through CFAR processing.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9429644B1Subaperture clutter filter with CFAR signal detection

Publication Date: 2016.08.30 NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA LLC

AI summary

The various technologies presented herein relate to the determination of whether a received signal comprising radar clutter further comprises a communication signal. The communication signal can comprise of a preamble, a data symbol, communication data, etc. A first portion of the radar clutter is analyzed to determine a radar signature of the first portion of the radar clutter. A second portion of the radar clutter can be extracted based on the radar signature of the first portion. Following extraction, any residual signal can be analyzed to retrieve preamble data, etc. The received signal can be based upon a linear frequency modulation (e.g., a chirp modulation) whereby the chirp frequency can be determined and the frequency of transmission of the communication signal can be based accordingly thereon. The duration and/or bandwidth of the communication signal can be a portion of the duration and/or the bandwidth of the radar clutter.