Time-Reversed RF Sensing for Multipath Target Detection

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Solution Overview

Problem

The impact of multipath propagation degrades RF sensing applications in wireless communication systems, particularly in urban and indoor environments, leading to challenges in target detection and tracking due to signal power spread and per-channel tap SNR drop, which are exacerbated in low SNR conditions.

Innovation Solution

Implementing time-reversed RF sensing signals generated based on channel conditions, using time reversal filters to compress multipath channels and enhance SNR for improved target detection and tracking, applicable in monostatic and bistatic RF sensing operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional RF sensing signals are transmitted, then the sensing coverage is provided, but multipath propagation degrades the target detection and tracking performance due to signal power spread and SNR drop

Engineering Contradiction:

Improvetarget detection and tracking performanceVSAvoidmultipath propagation effects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies time reversal to the RF sensing signal before transmission. By inverting the time domain characteristics of the signal based on channel impulse response, the multipath components that normally cause signal spread and SNR degradation are transformed to constructively interfere at the target location, thereby improving target detection and tracking performance in multipath environments

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent performs channel estimation and signal preprocessing before the actual RF sensing transmission. The channel impulse response is obtained in advance, and the sensing signal is pre-modulated with time reversal weights based on this channel information, so that when the signal propagates through the multipath channel, it automatically focuses energy at the target location without requiring real-time adaptation

Inventive Principle:

Principle #10Preliminary action

2Reliability

If time reversed RF sensing signals are transmitted, then target detection and tracking performance is enhanced, but additional signal processing complexity is introduced

Engineering Contradiction:

Improvetarget detection and tracking performanceVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent utilizes the channel's own multipath characteristics to improve performance. By estimating the channel impulse response and using its inherent time reversal symmetry, the system makes the multipath components work in favor of target detection rather than against it, thereby improving performance without requiring external assistance or complex adaptive algorithms

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20250383421A1Time reversal for radio frequency sensing

Publication Date: 2025.12.18 QUALCOMM INC

AI summary

Techniques are provided for utilizing time reversed reference signals for radio frequency (RF) sensing operations. An example method for performing radio frequency sensing operations includes transmitting a radio frequency reference signal, receiving channel information associated with the radio frequency reference signal, generating a time reversed radio frequency sensing signal based at least in part on the channel information, and transmitting the time reversed radio frequency sensing signal.