Adaptive I/Q Down-Conversion for Image Rejection Compensation
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Solution Overview
Problem
Wideband radio communication receivers face interference due to I/Q imbalance, which degrades performance by allowing an attenuated image signal to overlap with the desired signal, and existing solutions like training sequences are costly and time-consuming to implement.
Innovation Solution
A method involving adaptive signal processing, including conjugating processing, correlation, and integration to estimate and subtract interfering components, using adaptive FIR filtering and multiplication processing to mitigate I/Q imbalance, allowing for self-calibration and reduced calibration costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If training sequences are used for calibration, then I/Q imbalance compensation is achieved, but implementation cost and time consumption increase
Solution Approach 1:
The system performs self-calibration by automatically detecting and compensating for I/Q imbalance without requiring external training sequences. The calibration process is executed autonomously using the received signal itself, eliminating the need for separate calibration procedures and reducing both time and cost.
Solution Approach 2:
The I/Q imbalance compensation is performed in advance during the initial signal processing stage, before the main communication operations. By pre-calibrating the receiver using automatic detection algorithms, the system prepares the optimal compensation parameters beforehand, avoiding time-consuming calibration during operation.
2Measurement precision
If training sequences are used for calibration, then I/Q imbalance compensation is achieved, but implementation cost increases
Solution Approach 1:
The system performs self-calibration by automatically detecting and compensating for I/Q imbalance without requiring external training sequences. The calibration process is executed autonomously using the received signal itself, eliminating the need for separate calibration procedures and reducing both time and cost.
Solution Approach 2:
The invention replaces expensive dedicated calibration hardware and training sequences with software-based automatic detection algorithms that run on existing signal processing resources. This substitution of costly physical calibration mechanisms with computational methods significantly reduces implementation cost.
3Device complexity
If I/Q imbalance is not compensated, then device complexity is reduced, but receiver performance degrades
Solution Approach 1:
The system implements a feedback mechanism where the received signal is continuously monitored for I/Q imbalance characteristics. The detected imbalance parameters are fed back to adjust the compensation filters, creating a closed-loop system that automatically maintains optimal performance without adding significant complexity.
Solution Approach 2:
The invention dynamically adjusts signal processing parameters (filter coefficients, gain values, phase corrections) based on detected I/Q imbalance conditions. By changing these parameters adaptively rather than using fixed complex compensation circuits, the system maintains high performance with minimal added complexity.
Data Source
AI summary
An input signal has a desired signal component and an interfering signal component superimposed thereon. Interfering component estimation processing is applied to the input signal, obtaining as a result a filtered signal comprising a sequence of filtered data samples. The filtered signal is subtracted from the input signal obtaining as a result an output signal comprising a sequence of output data samples. The interfering component estimation processing applies conjugating processing to the input signal, providing a conjugated version of the input signal. An adaptive signal processing coefficient is computed and adaptive signal processing is applied to the conjugated version of the input signal using the adaptive processing coefficient.