On-Chip Reflection Coefficient Measurement for Rx Antenna Matching
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Solution Overview
Problem
Existing RF devices, particularly in automotive applications like ADAS, lack a reliable method to monitor the quality of Rx antenna connections without relying on open DC connections to ground, which is necessary for input balun operation and ESD protection, and cannot provide RF impedance information.
Innovation Solution
An on-chip measurement system using an Rx antenna switch to isolate and probe the Rx antenna, measuring phasors of reflected test signals, computing a complex ratio and reflection coefficient, and applying a transfer function to monitor impedance matching, enabling direct monitoring without additional components on the Rx path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If open DC connections to ground are used for input balun operation and ESD protection, then reliability is improved, but measurement precision of RF impedance is worsened due to inability to provide RF impedance information
Solution Approach 1:
A test signal generator and signal coupler are introduced as intermediary components to inject test signals into the Rx antenna path. These intermediaries enable RF impedance measurement without requiring direct DC connections to ground, allowing the system to maintain both reliability (through preserved DC paths) and measurement precision (through RF test signal injection and reflection coefficient measurement)
2Measurement precision
If additional components are added to monitor Rx antenna connection quality, then measurement precision is improved, but device complexity is worsened
Solution Approach 1:
The Rx chain is designed to serve multiple functions: it processes normal receive signals and simultaneously measures reflection coefficients for antenna connection monitoring. The existing Rx chain components (low noise amplifier, mixer, ADC) are utilized for both purposes, eliminating the need for separate dedicated measurement components and reducing overall device complexity while maintaining measurement precision
3Measurement precision
If DC connections to ground are removed for measurement purposes, then measurement precision is improved, but reliability is worsened due to impact on input balun operation and ESD protection
Solution Approach 1:
The measurement system operates in distinct time segments: during normal operation, DC connections remain intact for balun and ESD protection; during measurement intervals, the test signal generator injects RF test signals through the signal coupler to measure reflection coefficients. This temporal segmentation allows both reliability and measurement precision to coexist without conflict
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 provides reliable impedance matching monitoring for Rx antennas, allowing for input balun operation and ESD protection while detecting imperfect connections, independent of DC connections to ground, and minimizing impact on the RF device's front-end.
Implementation Method 1
a test signal generator to generate a test signal; a signal coupler to inject the test signal toward the Rx antenna
Implementation Method 2
an Rx antenna switch configured to: cause, while in a first switch state, the Rx antenna to be isolated from an Rx chain to generate a first reflected test signal, and permit, while in a second switch state, the test signal to probe the Rx antenna to generate a second reflected test signal
Implementation Method 3
the Rx chain configured to: measure a phasor Y1 of a first baseband signal generated based on the first reflected test signal, and measure a phasor Y2 of a second baseband signal generated based on the second reflected test signal
Data Source
AI summary
A device may include a receive (Rx) antenna input to couple an Rx antenna to an Rx chain, and a signal coupler to inject the test signal toward the Rx antenna. The device may include an Rx antenna switch to, in a first switch state, cause the Rx antenna to be isolated from the Rx chain and, in a second switch state, permit the test signal to probe the Rx antenna. The Rx chain may measure a phasor of a first baseband signal generated based on a first reflected test signal and a phasor of a second baseband signal generated based on a second reflected test signal. The device may include a control circuit to compute a complex ratio based on the phasors, compute a measured reflection coefficient based on the complex ratio and using a transfer function, and monitor an impedance matching of the Rx antenna.