SSB Receiver Phase Calibration for Image Signal Cancellation
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Solution Overview
Problem
Current SSB receiver calibration methods suffer from high residual image signals and high complexity, leading to distorted received SSB signals and increased costs.
Innovation Solution
A method for calibrating an SSB receiver by adjusting the phase shift to minimize phase errors calculated from phase differences between test signals, allowing for efficient image signal cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current calibration methods are used to cancel image signals, then image signal cancellation is achieved, but residual image signals remain too high distorting the received SSB signal
Solution Approach 1:
The calibration method uses feedback by measuring the phase differences of test signals with known phase offsets, calculating phase errors, and adjusting the phase shifter to minimize these errors. This closed-loop feedback mechanism ensures that the phase alignment between I and Q paths is optimized, thereby minimizing residual image signals and improving both cancellation reliability and measurement precision.
Solution Approach 2:
The method changes the phase shift parameter in the phase shifter based on calculated phase errors from test signal measurements. By adjusting this parameter to minimize phase errors, the system optimizes the cancellation of image signals while maintaining accurate phase measurement of the desired SSB signal.
2Reliability
If complex calibration methods are used to reduce residual image signals, then image cancellation efficiency improves, but hardware complexity and cost increase
Solution Approach 1:
The calibration method is self-performing, using the SSB receiver itself to generate and measure test signals. The system automatically calculates phase errors and adjusts its own phase shifter without requiring external calibration equipment, thereby achieving high image cancellation efficiency while keeping hardware complexity low.
Solution Approach 2:
The phase shifter and combiner are used for both signal processing during normal operation and for calibration during setup. The test signal generator and phase measurement capabilities are integrated into the existing receiver structure, making the calibration function universal and eliminating the need for separate dedicated calibration hardware.
Data Source
AI summary
A method for calibrating a single sideband (SSB) receiver, comprising: a) adjusting a mutual phase shift of I- and Q-signals to a first phase shift value; b) feeding a first, a second and a third test signal having a predetermined phase offset to an input to obtain respective SSB signals, and measuring a first and a second phase difference therefrom; c) calculating a first phase error on the basis of the first and second phase differences; d) repeating steps a)-c) with a second phase shift value to obtain a second phase error; and e) calibrating the SSB receiver by using that one of the first and second phase shift values that has yielded the smaller one of the first and second phase errors.