Transceiver IQ and DC Offset Calibration Using Returned Test Signals
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Solution Overview
Problem
Existing transmission/reception circuits for digital communication, particularly those using the direct mixer principle, suffer from nonlinearities such as IQ mismatch and DC offset, which impair signal quality and are not effectively compensated for by existing methods, especially during changes due to aging or temperature fluctuations.
Innovation Solution
A transmission/reception arrangement with switchable connections and compensation devices that use a test signal to calibrate both the transmission and reception paths, allowing for real-time compensation of nonlinearities and DC components by predistorting signals and adjusting local oscillator frequencies to identify and correct amplitude, phase, and DC errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fixed preset calibration is performed during production, then initial IQ mismatch and DC component errors are corrected, but fluctuations in errors during product lifecycle due to aging and temperature changes are not compensated
Solution Approach 1:
The patent implements dynamic calibration by periodically injecting test signals through the transmission path and using a measuring apparatus to detect errors in real-time. The calibration apparatus continuously adjusts compensation parameters based on measured IQ mismatch and DC component values, allowing the system to adapt to aging and temperature variations rather than relying on fixed production-time presets
Solution Approach 2:
The patent establishes a feedback loop where the measuring apparatus continuously monitors the transmission path for IQ mismatch and DC components, feeds this information back to the calibration apparatus, which then adjusts the compensation parameters. This closed-loop feedback mechanism ensures long-term error stability by continuously correcting drift caused by aging and temperature changes
2Ease of manufacture
If separate calibration methods are used for transmission path and reception path, then each path can be calibrated independently, but the overall system requires multiple external auxiliary means and complex calibration procedures
Solution Approach 1:
The patent merges the calibration functions for both transmission and reception paths into a single integrated calibration apparatus that uses one shared measuring apparatus. The test signal generator injects signals that traverse both paths, and the measuring apparatus detects errors in both paths simultaneously, eliminating the need for separate external calibration equipment for each path
Solution Approach 2:
The calibration apparatus is designed with multi-functionality to handle both transmission path and reception path calibration using the same hardware components. The measuring apparatus can measure errors in both paths, and the control unit processes both types of measurements, reducing the need for dedicated external auxiliary means while maintaining independent calibration capability
3Manufacturing precision
If predistortion compensation is applied to correct amplitude and phase errors, then IQ mismatch is reduced, but additional DC components and other nonlinearities remain uncorrected
Solution Approach 1:
The patent segments the compensation process into distinct functional blocks within the calibration apparatus: one dedicated to correcting IQ mismatch through predistortion of amplitude and phase, and another dedicated to eliminating DC components through separate measurement and compensation. This segmentation allows each compensation mechanism to address specific error types without interfering with the other, achieving comprehensive error correction
Data Source
AI summary
The invention proposes a transmission/reception arrangement (1) which contains a respective distortion unit (5, 6) for the transmission and reception paths (2, 3) and also a calibration apparatus (7). By sending a test signal in an operating mode for calibration and returning the test signal processed in the transmission path (2) to the reception path, it is possible to evaluate the error signals in the transmission and reception paths. In line with the principle proposed, this is done by evaluating the spectral components of the returned received signal which each represent single sources of error in the transmission or reception path. This allows calculation of calibration parameters for suppressing these errors both in the transmission path and in the reception path.