Passive Radar Static Component Cancellation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Passive radar systems face challenges in detecting moving targets due to the significant power difference between static and dynamic signal contributions, which limits detection power and precision, as the dynamic contribution from moving targets has a low amplitude compared to the strong static contribution from fixed reflectors.

Innovation Solution

A passive radar system that includes a reception antenna, an analogue-digital converter, a moving target detection unit, and a digitised signal processing unit to estimate and subtract the static contribution during the calibration phase, using known sequences for synchronisation and multi-path propagation channel estimation, and a coupler to reduce the power difference between static and dynamic contributions during target detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the passive radar receives the transmitted signal through multi-path propagation, then the static contribution from fixed reflectors is strong, but the dynamic contribution from moving targets becomes very weak and difficult to detect

Engineering Contradiction:

Improvedetection powerVSAvoidsignal amplitude ratio

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent extracts and separates the static contribution from the received signal using a calibration phase where the radar transmits known sequences and processes the echoes to identify static components. This extracted static contribution is then removed from the total received signal, leaving the dynamic contribution from moving targets more prominent and detectable.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs a preliminary calibration phase before actual target detection, during which the static contribution is estimated and stored. This preliminary action prepares the system by pre-identifying the static components that will need to be removed during the usage phase, enabling more effective detection of moving targets.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the passive radar uses digital signal processing to extract dynamic contribution, then the detection capability is improved, but the filtering complexity increases significantly

Engineering Contradiction:

Improvetarget detection capabilityVSAvoidfiltering complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex digital filtering operations with a simpler subtraction operation. Instead of using sophisticated digital signal processing to separate static and dynamic contributions, the system subtracts the pre-estimated static contribution from the received signal, significantly reducing computational complexity while maintaining detection effectiveness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the approach from frequency-domain filtering to time-domain subtraction. By estimating the static contribution in the calibration phase and subtracting it directly from the received signal in the usage phase, the system avoids complex frequency-domain processing and reduces the computational parameters required for filtering.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the passive radar receives strong static signals from the transmitter and fixed reflectors, then the reception systems must be slaved on the strongest signal, but this causes saturation and limits detection of weak target signals

Engineering Contradiction:

Improvedetection sensitivityVSAvoidsignal saturation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the static contribution that causes saturation from the received signal. By identifying and removing this strong static component through the calibration and usage phases, the system prevents saturation of the reception systems and enables detection of weak dynamic signals from moving targets without being overwhelmed by the strong transmitter signals.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS11086003B2Passive radar with analogue cancellation of the static component

Publication Date: 2021.08.10 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

A passive radar comprises a reception antenna for a signal transmitted by a non-cooperative transmitter, the received signal comprising a static contribution related to propagation of the signal transmitted through a multi-path propagation channel and a dynamic contribution related to propagation of echoes of the transmitted signal from a moving target. The passive radar also comprises a reception chain that includes an analogue-digital converter capable of outputting a digitised signal, a moving target detection unit, a digitised signal processing unit configured to determine an estimation of the static contribution during a calibration phase of the passive radar, a transmission chain that can output an analogue signal representative of the estimation of the static contribution, and a directional coupler configured to output the signal received during the calibration phase of the passive radar to the reception chain.