Online Radar Phase Calibration via Static Environment Measurements
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Solution Overview
Problem
Radar systems in autonomous vehicles face challenges in accurately calibrating phase offsets due to factors like temperature changes, antenna position variations, and environmental factors, which affect the accuracy of angular resolution and introduce biases, and existing calibration methods are either expensive, complex, or unable to account for all error sources.
Innovation Solution
The radar system performs online phase calibration using static objects in the environment, leveraging doppler measurements and phase offsets to estimate calibration errors, allowing for continuous correction without the need for factory calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory calibration is performed, then initial phase offset accuracy is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The radar system performs self-calibration by using its own transmitted signals and receiving antennas to measure phase offsets and Doppler shifts from static environmental objects. The system automatically computes calibration errors and applies corrections without external calibration equipment or factory intervention, enabling continuous online calibration in real operating conditions.
Solution Approach 2:
Static objects in the environment serve as intermediaries for calibration. These objects reflect radar signals back to the receiving antennas, providing a stable reference for measuring phase offsets and Doppler shifts. The calibration process uses these environmental reflections as mediators to determine and correct phase calibration errors without requiring specialized calibration equipment.
2Measurement precision
If traditional calibration methods are used, then calibration accuracy is improved, but time consumption and equipment requirements increase
Solution Approach 1:
The calibration process operates continuously in the background during normal radar operation. The system constantly transmits signals, receives reflections from static objects, measures phase offsets and Doppler shifts, and updates calibration corrections without interrupting the radar's primary function of detecting moving targets. This eliminates the need for separate calibration sessions or equipment.
Solution Approach 2:
The patent replaces mechanical calibration equipment and manual adjustment procedures with signal processing-based calibration. Instead of using physical calibration targets, adjustable mechanical components, or factory calibration equipment, the system uses computational methods to measure phase offsets from reflected signals and automatically compute correction factors.
3Reliability
If phase offset calibration is performed using static objects, then calibration reliability is improved, but noise from static environment measurements must be filtered
Solution Approach 1:
The system uses Doppler shift measurements as feedback to identify and filter noise from static object measurements. Since static objects should produce zero Doppler shift, any measured Doppler signal indicates either a moving target or measurement noise. The calibration process uses this feedback to distinguish valid calibration data from noisy measurements and applies appropriate filtering to improve reliability.
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
This approach improves the accuracy and reliability of radar systems by accurately determining phase offset calibration errors, reducing the need for factory calibration and potentially saving time and equipment costs, while effectively filtering out noise from static environment measurements.
Implementation Method 1
A radar system may comprise a transmission system that transmits electromagnetic waves (e.g., radio waves) via one or more antennas and a detection system comprising an array of antennas
Implementation Method 2
determine, for a first reflected radar signal, a first doppler measurement indicating a velocity component based on a comparison of the first reflected radar signal to the transmitted radar signal
Data Source
AI summary
An apparatus comprising an antenna array comprising a plurality of antennas to receive a plurality of radar signals reflected by a plurality of objects responsive to a transmitted radar signal; a doppler measurement module to determine, for a first reflected radar signal of the plurality of reflected radar signals, a first doppler measurement indicating a velocity component based on a comparison of the first reflected radar signal to the transmitted radar signal; a phase offset measurement module to determine a first phase offset of the first reflected radar signal received at a first antenna of the plurality of antennas relative to a phase of the first reflected radar signal received at a reference antenna of the plurality of antennas; and a phase offset calibration module to determine, for the first antenna, a first phase offset calibration error based on the first doppler measurement and the first phase offset.