RC-CR Phase Calibration Circuit for Measurement Receiver Accuracy
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Solution Overview
Problem
Measurement receivers in wireless communication systems face challenges in maintaining accurate phase difference between RC and CR paths due to mismatched loading impedance and layout variations, leading to RC-CR phase errors that affect calibration performance.
Innovation Solution
A circuit with a RC-CR phase error calibration mechanism, utilizing an array of capacitors and switches connected in parallel, adjusts the phase difference between output signals to fall within a predetermined range by controlling the switches, ensuring accurate phase shift across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RC-CR circuit is used for phase shifting in measurement receiver, then phase shift function is achieved, but phase error occurs due to mismatched loading impedance and layout variations
Solution Approach 1:
The patent applies preliminary action by performing phase error calibration before actual measurement operations. The system pre-determines calibration values for RC and CR paths based on measured phase errors, and stores these calibration values for subsequent use. This preliminary calibration process compensates for phase errors caused by mismatched loading impedance and layout variations before they affect measurement accuracy.
Solution Approach 2:
The patent changes parameters by adjusting capacitance values in the RC and CR paths through switchable capacitor arrays. The system varies capacitance values to compensate for phase errors, allowing dynamic adjustment of phase shift characteristics. By changing capacitance parameters based on measured phase errors, the system maintains accurate phase difference despite impedance mismatches and layout variations.
2Measurement precision
If calibration process is added to correct phase errors, then phase accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the calibration process into separate, independent steps: measuring phase error, determining calibration values for RC path and CR path separately, and storing calibration values in distinct storage elements. The capacitor arrays are segmented into multiple switchable units, allowing incremental adjustment rather than requiring complete circuit redesign. This segmentation reduces overall system complexity while maintaining calibration accuracy.
Solution Approach 2:
The system implements self-service by automatically measuring its own phase errors and generating appropriate calibration values without external intervention. The measurement receiver performs self-calibration by measuring phase differences between RC and CR paths, determining calibration values, and applying corrections autonomously. This self-calibrating capability eliminates the need for external calibration equipment or complex manual adjustment mechanisms.
3Adaptability or versatility
If switchable capacitor array is used for phase adjustment, then phase range coverage is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies feedback by measuring the actual phase error in the RC-CR circuit and using this measurement to determine appropriate calibration values. The system continuously monitors phase differences and adjusts capacitance values through the switchable capacitor arrays based on measured feedback. This closed-loop feedback mechanism compensates for manufacturing variations in capacitor values, allowing wide phase adjustment range without requiring extremely tight manufacturing precision for individual capacitor matching.
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 calibrates RC-CR phase errors, enhancing the accuracy of phase shift and improving the performance of measurement receivers in factory and live mode calibrations, particularly for FD I/Q image calibration in cellular transmitters.
Implementation Method 1
a RC-CR circuit, configured to phase-shift an input signal received at an input node of the RC-CR circuit
Implementation Method 2
the RC-CR circuit has a first output node outputting a first output signal over a first output path, and the RC-CR circuit has a second output node outputting a second output signal over a second output path
Data Source
AI summary
A circuit includes a RC-CR circuit and a second circuit. The RC-CR circuit outputs a first signal at a first output node over a RC path, and a second signal at a second output node over a CR path. The second circuit is coupled to the RC-CR circuit at the first output node over the RC path. The second circuit includes an array of capacitors coupled in parallel and a plurality of switches, and each of the array of capacitors is connected, in series, to a corresponding switch in the plurality of switches. Each of the array of capacitors and its corresponding switch are coupled between the first output node and a ground. The plurality of switches is switched on or off such that the first signal and the second signal have a phase difference that falls within a predetermined phase range.