FMCW Radar Phase Shifting to Suppress False Doppler Peaks
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Solution Overview
Problem
Existing FMCW radar systems face challenges in accurately determining the presence, location, and velocity of objects due to phase shifter non-linearity errors, which cause false Doppler shift peaks and inter-transmitter coupling, affecting the accuracy of angle and velocity determinations.
Innovation Solution
The implementation of a frequency modulated continuous wave (FMCW) radar system with multiple transmitters, phase shifters, and receivers, utilizing phase shift coding and temperature compensation to mitigate phase shifter integral non-linearity errors, enabling improved spatial resolution and accurate object detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase shifters are used to transmit signals from multiple transmitters, then the radar system can determine object location and velocity, but phase shifter non-linearity errors cause false Doppler shift peaks and inter-transmitter coupling
Solution Approach 1:
The patent applies parameter changes by selecting specific base phase shift values (0, 2π/N, 4π/N, ..., 2π(N-1)/N radians) for N transmitters. These discrete phase shift values are chosen to minimize non-linearity errors and avoid false Doppler peaks. The phase shift codes are systematically varied across multiple chirps, and the processor uses these controlled parameter changes to distinguish between true Doppler shifts and artifacts caused by phase shifter non-linearity.
Solution Approach 2:
The patent implements feedback mechanisms where the processor monitors received signals and uses the known phase shift patterns to compensate for non-linearity errors. By comparing expected phase shifts with actual measured phase shifts, the system identifies and corrects for INL errors, thereby eliminating false Doppler peaks and inter-transmitter coupling effects.
2Measurement precision
If differentiated base phase shifts are applied to transmitted signals, then unique Doppler shifts per transmitter are achieved, but the system complexity increases due to temperature-dependent code offsets
Solution Approach 1:
The patent addresses temperature-dependent variations by dynamically adjusting phase shift code offsets based on temperature measurements. The system stores temperature-compensated phase shift values and selects appropriate offset values from pre-characterized data structures. This allows the system to maintain accurate Doppler differentiation across varying temperature conditions without requiring complex real-time calibration.
Solution Approach 2:
The patent performs preliminary characterization of phase shifter non-linearity and temperature effects during system calibration. Pre-computed compensation tables and lookup structures are generated in advance, allowing the processor to quickly apply corrections during normal operation without performing complex calculations in real-time.
3Measurement precision
If multiple phase shift codes are used across multiple chirps, then spatial resolution is improved, but the processing time and computational complexity increase
Solution Approach 1:
The patent performs preliminary organization of phase shift code sequences and pre-computation of expected signal patterns. The processor uses stored lookup tables containing phase shift mappings and compensation values, eliminating the need for complex real-time calculations. This preliminary preparation significantly reduces processing time while maintaining high spatial resolution through the use of multiple phase shift codes across multiple chirps.
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
The system enhances the accuracy of object detection by reducing false Doppler shift peaks and inter-transmitter coupling, allowing for precise determination of object presence, location, and velocity through advanced signal processing techniques.
Implementation Method 1
An FMCW radar transmits an electromagnetic radiation (EMR) signal with a known frequency that is modulated to vary up and down over time
Implementation Method 2
The radar receives a reflected signal corresponding to the transmitted signal
Implementation Method 3
Speed and direction of movement together correspond to a velocity of a detected object
Implementation Method 4
Different ones of the phase shifters have different respective base phase shifts selected in response to N. The transmitter is configured to transmit the phase shifted FMCW chirps
Data Source
AI summary
In described examples, a frequency modulated continuous wave (FMCW) radar system includes an FMCW signal generator, a number N transmitters, N phase shifters, multiple receivers, and a processor. The FMCW signal generator is configured to generate FMCW chirps. Different ones of the phase shifters have different respective base phase shifts selected in response to N. The transmitter is configured to transmit the phase shifted FMCW chirps. The receivers are configured to receive an FMCW chirp reflected by an object in range of the FMCW radar system. The processor is configured to determine a location of the object in range in response to the received FMCW chirp.