Radar Phase Shifter Field Calibration via Chirp Reflection Analysis
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Solution Overview
Problem
Radar systems employing phase shifters face non-linearity issues due to device-dependent characteristics, which factory calibration cannot fully address, especially considering temperature and aging effects, and on-chip loopback calibration is undesirable for onboard routing mismatches.
Innovation Solution
A radar system with a radar transceiver IC and processor that generates chirp signals, induces phase shifts, and determines the actual phase shift by analyzing reflections, allowing for real-time calibration of phase shifters using a method that involves transmitting frames of chirps with alternating phase shifts and processing the resulting digital signals to adjust for phase shifter drift and routing mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory calibration is performed during manufacturing, then initial phase accuracy is improved, but the calibration cannot capture temperature and aging effects during device operation
Solution Approach 1:
The system performs preliminary calibration at the factory to establish baseline phase accuracy, then uses field calibration to adjust for environmental changes. The field calibration process builds upon the factory calibration rather than replacing it entirely, allowing the system to maintain initial precision while adapting to operational conditions.
Solution Approach 2:
The calibration system transitions from static factory calibration to dynamic field calibration that continuously adapts to changing temperature and aging conditions. The phase shifter calibration is performed repeatedly in the field with different temperature conditions to capture the dynamic behavior of the device during operation.
2Measurement precision
If on-chip loopback calibration is used to determine phase response, then phase shift calibration is improved, but onboard routing mismatches cause calibration errors
Solution Approach 1:
The system uses an intermediary approach by performing calibration through the actual radar signal path rather than using internal loopback paths. This allows calibration to account for all real-world factors including onboard routing mismatches, while still using the processor to analyze and determine the calibration parameters.
Solution Approach 2:
The system implements feedback by transmitting chirp signals through the phase shifter and analyzing the reflected signals to determine actual phase response. This closed-loop feedback mechanism allows the system to automatically adjust and compensate for routing mismatches and other real-world variations.
3Device complexity
If phase shifters are calibrated statically at manufacturing, then device complexity is reduced, but reliability under varying operating conditions deteriorates
Solution Approach 1:
The system performs calibration periodically in the field under different operating conditions rather than relying solely on static factory calibration. This periodic recalibration maintains reliability without requiring continuous complex adjustments, balancing simplicity with accuracy.
Solution Approach 2:
The system changes calibration parameters by performing calibration at different temperature conditions and using these varied parameter sets to build a comprehensive calibration model. This approach improves reliability across operating conditions without significantly increasing device complexity.
Data Source
AI summary
A radar system is provided and includes a radar transceiver integrated circuit (IC) and a processor coupled to the radar transceiver IC. The radar transceiver IC includes a chirp generator configured to generate a plurality of chirp signals and a phase shifter configured to induce a signal phase shift. The radar transceiver IC is configured to transmit a frame of chirps based on the plurality of chirp signals and generate a plurality of digital signals, each digital signal corresponding to a respective reflection received based on the plurality of chirp signals. The processor is configured to control the phase shifter to induce the signal phase shift in a first subset of chirp signals of the plurality of chirp signals and determine a phase shift induced in the first subset of chirp signals by the phase shifter based on the digital signal.