Phase Shifter Self-Test Circuit for Automotive Radar
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Solution Overview
Problem
Existing self-driving car radar systems face issues with device mismatch due to temperature and aging, which can distort beam patterns and cause sidelobe formation, leading to incorrect obstacle detection, necessitating a cost-effective and reliable mechanism for calibrating phase shifters.
Innovation Solution
A self-test method and circuit that measure and combine in-phase and quadrature components of output signals with predetermined phase differences to verify the operation of phase shifters, using a phase shifter, I/Q mixer, processing circuit, and self-test circuit with multipliers and comparators to determine if the relationship corresponds to the expected phase difference within an error tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing calibration mechanisms are implemented, then phase shifter accuracy is improved, but system cost and complexity increase
Solution Approach 1:
The system performs self-calibration by using its own output signal as the reference. The DUT output signal is fed back through a feedback path to the I/Q mixer, where it is compared with the original transmit signal. This self-referential approach eliminates the need for external calibration equipment, reducing system complexity and cost while maintaining calibration accuracy.
Solution Approach 2:
A feedback path is implemented that routes the DUT output signal back to the I/Q mixer for comparison with the transmit signal. This feedback mechanism enables continuous monitoring and calibration of phase shifter performance, allowing the system to detect and correct phase errors without external intervention, thereby improving accuracy without proportionally increasing complexity.
2Measurement precision
If external calibration equipment is used, then measurement accuracy is improved, but system cost increases
Solution Approach 1:
The system creates a copy of the transmit signal through the feedback path and uses this copied signal as the reference for comparison at the I/Q mixer. Instead of requiring expensive external calibration equipment, the system generates its own reference copy, achieving accurate phase measurement while avoiding additional cost and complexity.
Solution Approach 2:
The I/Q mixer serves multiple functions: it performs both the primary signal processing function and the calibration reference comparison function. By making the I/Q mixer multi-functional, the system eliminates the need for separate calibration equipment, reducing overall system cost while maintaining measurement accuracy.
3Measurement precision
If beam-steering with phased array is implemented, then measurement range and resolution are improved, but susceptibility to device mismatch increases
Solution Approach 1:
The system performs preliminary calibration by comparing phase relationships before actual beam-steering operations. The self-test method detects and corrects phase mismatches in advance, ensuring that the phased array operates with accurate phase relationships, thereby maintaining beam pattern stability and reliability while preserving measurement precision.
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 solution effectively verifies the operation of phase shifters, reducing the likelihood of sidelobe formation and incorrect obstacle detection, thereby enhancing the reliability and safety of automotive radar systems while maintaining cost-effectiveness.
Implementation Method 1
The I/Q mixer mixes the output signal with a reference signal to obtain in-phase and quadrature components of the output signal
Data Source
AI summary
Illustrative methods and circuits to verify operation of phase shifters. One illustrative method includes: obtaining a first set of in-phase and quadrature components (I1,Q1) of a phase shifter output signal with a first setting; measuring a second set of components (I2,Q2) with a second setting, the second setting being offset from the first by a predetermined phase difference; and combining the first and second sets to determine whether their relationship corresponds to the predetermined phase difference. An illustrative transmitter includes: a phase shifter, an I/Q mixer, and a processing circuit. The phase shifter converts a transmit signal into an output signal having a programmable phase shift. The I/Q mixer mixes the output signal with a reference signal to obtain in-phase and quadrature components of the output signal. The processing circuit is coupled to the I/Q mixer implement the disclosed method.