CW Radar Sensor Phase Ambiguity Resolution
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Solution Overview
Problem
Existing radar systems face limitations in spatial resolution and range due to phase ambiguity issues, particularly when measuring distances beyond a single wavelength, and struggle with high-precision short-range measurements.
Innovation Solution
A radar sensor system comprising a pair of continuous wave (CW) radar transceivers with double periodic composite right/left hand (CRLH) substrate integrated waveguide (SIW) leaky wave antennas and a six-port interferometer, which allows for enhanced spatial resolution and extended range by generating power signals for computing relative displacement, thereby addressing phase ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase evaluation technique is used to improve spatial resolution, then subwavelength resolutions are achieved, but phase ambiguity occurs when distance exceeds one wavelength
Solution Approach 1:
The system segments the measurement process by using multiple continuous wave radars operating at different frequencies. Each radar provides phase measurements within its wavelength range, and by combining measurements from multiple frequency bands, the system achieves both subwavelength resolution and extended unambiguous range beyond a single wavelength.
Solution Approach 2:
The invention adds a frequency dimension to the measurement system. Instead of relying on a single frequency radar, multiple CW radars operating at different frequencies are employed, transforming the problem from a one-dimensional phase measurement into a multi-dimensional measurement space where phase ambiguity is resolved through frequency diversity.
2Measurement precision
If FMCW radar uses steep frequency ramps for high spatial resolution at short distances, then larger frequency shifts are generated, but nonlinear output signal is produced which is detrimental to performance
Solution Approach 1:
The invention replaces the FMCW frequency modulation mechanism with continuous wave transmission and phase comparison. Instead of using steep frequency ramps that cause nonlinear distortion, the system uses stable CW signals and extracts distance information through phase evaluation, eliminating the nonlinear output signal problem while maintaining high spatial resolution.
3Length of stationary object
If pulse radar measures short-range distances, then target distance can be derived from round-trip time, but low accuracy occurs in very short-time interval measurements
Solution Approach 1:
The invention changes the measurement parameter from time-of-flight (pulse radar) to phase difference (continuous wave radar). By using phase evaluation of CW signals, the system achieves high precision in short-time interval measurements corresponding to short ranges, overcoming the limitation of pulse radar where extremely short time intervals cannot be measured accurately.
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 achieves improved spatial resolution and increased detectable range beyond a single wavelength, enabling effective dynamic gesture recognition and other applications by accurately computing relative displacement using phase differences.
Implementation Method 1
a voltage-controlled oscillator (VCO) configured to generate an output signal having a specific frequency
Implementation Method 2
transmit a backward or forward main beam, wherein a direction of the transmitted main beam is determined by the specific frequency of the received transmission signal, and when the main beam is reflected back to the antenna by an object adjacent the sensor
Implementation Method 3
a six-port interferometer, provided within each CW radar transceiver, is configured to receive, by input ports of the six-port interferometer, the reference signal and the divided-backscattered signal from the divider circuit, whereby the six-port interferometer is configured to generate, based on the received reference and divided-backscattered signals, power signals at output ports of the six-port interferometer whereby the power signals are used for computing relative displacement L
Data Source
AI summary
Example embodiments describe a radar sensor, whereby the radar sensor comprises a pair of continuous wave (CW) radar transceivers that each has a leaky wave antenna that are provided adjacent to each other. Each CW radar transceiver comprises a microwave frequency transmission circuit configured to transmit and receive signals reflected off a nearby object. The transmitted and received signals are then processed by the radar sensor to determine a relative displacement between the detected object and the radar sensor. This determined relative displacement may then be used with machine learning techniques to identify dynamic gestures made within the radar sensor's range of detection.