Receiving Circuit I/Q Mismatch Calibration via External Oscillator
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Solution Overview
Problem
Receiving circuits in wireless communication devices often suffer from I/Q mismatch, leading to mirror frequency interference and reduced signal-to-noise ratio (SNR), which degrades system throughput.
Innovation Solution
A receiving circuit capable of performing I/Q mismatch calibration using an external oscillating signal, comprising a low-noise amplifier, in-phase and quadrature signal processing circuits, and a calibration circuit that controls switch elements to adjust for gain and phase mismatches based on detection signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If I/Q mismatch calibration is performed using traditional methods requiring dedicated oscillators and signal transmission circuits, then calibration accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing local oscillator serve dual purposes: generating signals for normal receiving operations and providing calibration signals for I/Q mismatch correction. The receiving circuit processes both communication signals and calibration signals through the same signal path, eliminating the need for dedicated calibration oscillators and reducing circuit complexity while maintaining calibration accuracy
Solution Approach 2:
The system uses its own internal local oscillator to generate calibration signals, making the receiving circuit self-sufficient for calibration purposes. By utilizing internally available resources rather than external dedicated components, the system achieves I/Q mismatch calibration without adding complexity from external calibration equipment
2Measurement precision
If I/Q mismatch calibration is performed using traditional methods with dedicated oscillators, then calibration capability is improved, but loss of time during calibration increases
Solution Approach 1:
The patent performs I/Q mismatch calibration in advance during manufacturing or initialization, storing the calculated compensation coefficients in memory. This preliminary calibration eliminates the need for repeated real-time calibration operations, saving time during actual receiving operations while maintaining high calibration accuracy through the stored correction parameters
3Device complexity
If I/Q mismatch calibration is not performed, then device complexity is reduced, but signal-to-noise ratio deteriorates due to mirror frequency interference
Solution Approach 1:
The patent dynamically adjusts the gain and phase parameters of the I/Q signal paths using compensation coefficients obtained through calibration. By changing these parameters to correct mismatches, the system eliminates mirror frequency interference and improves signal-to-noise ratio without requiring complex additional hardware, achieving high reliability through parameter optimization rather than structural complexity
Data Source
AI summary
A receiving circuit includes: a first receiving terminal for receiving a RF signal; a second receiving terminal for receiving an external oscillating signal generated by an external oscillator; a low-noise amplifier coupled with the first receiving terminal and the second receiving terminal and utilized for generating an output signal; a first switch element positioned between the second receiving terminal and the low-noise amplifier; an in-phase signal processing circuit for generating an in-phase detection signal based on the output signal; an quadrature signal processing circuit for generating an quadrature detection signal based on the output signal; and a calibration circuit for controlling the first switch element and capable of performing an I/Q mismatch calibration operation according to the in-phase detection signal and the quadrature detection signal when the first switch element is turned on.