FMCW Radar Chirp-Start Dithering for Spurious Signal Mitigation

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Solution Overview

Problem

FMCW radar systems are affected by spurious signals that cause erroneous distance and velocity determinations due to fixed-frequency spurs, leading to multiple target misinterpretations.

Innovation Solution

Dithering the chirp start frequency, ADC sampling window start time, and idle time between chirps to mitigate the impact of spurious signals, ensuring coherent signal processing and accurate object detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fixed-frequency chirps are transmitted, then the radar system operates with stable and predictable frequency, but spurious signals cause erroneous distance and velocity determinations

Engineering Contradiction:

Improveaccuracy of distance and velocity determinationVSAvoidspurious signal interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the chirp start frequency variable rather than fixed. The frequency is dithered according to a predetermined sequence, transforming the static frequency parameter into a dynamic one that changes over time, thereby mitigating the impact of fixed-frequency spurious signals

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the frequency parameter of the chirp signals by dithering the start frequency according to a predetermined sequence. This parameter change causes spurious signals to spread across multiple frequency bins rather than concentrating at a single frequency, improving measurement accuracy

Inventive Principle:

Principle #35Parameter changes

2Reliability

If dithering is applied to chirp start frequency, then spurious signal impact is mitigated, but signal processing complexity increases

Engineering Contradiction:

Improvemitigation of spurious signalsVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by predetermining the dithering sequence before signal processing. The predetermined sequence allows the system to pre-calculate compensation values, reducing the computational burden during real-time processing while maintaining the benefits of frequency dithering

Inventive Principle:

Principle #10Preliminary action

3Reliability

If ADC sampling window start time is fixed, then sampling is simple and consistent, but spurious signals remain coherent across chirps

Engineering Contradiction:

Improvecoherence of signal processingVSAvoidcoherence of spurious signals

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the ADC sampling window start time variable. The sampling window is shifted according to a predetermined sequence that corresponds to the frequency dithering, transforming the static sampling timing into a dynamic parameter that changes over time

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the timing parameter of the ADC sampling window by shifting the start time according to a predetermined sequence. This parameter change desynchronizes the sampling with respect to spurious signals while maintaining coherence with the desired signal through appropriate compensation

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3935406B1Dithering FMCW radar parameters to mitigate spurious signals

Publication Date: 2025.08.13 TEXAS INSTRUMENTS INC

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AI summary

A method (1200) for a radar system includes transmitting, by a transmit channel of the radar system, a frame comprising first, second, and third chirps (1202). Each chirp has a chirp start frequency, and the chirp start frequency of the transmitted chirps is dithered (1206). The method also includes receiving, by a receive channel of the radar system, a frame of reflected chirps based on the transmitted frame, and generating a digital intermediate frequency (IF) signal (1204).