Millimeter-Wave Transceiver Loopback Calibration for I/Q Imbalance
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Solution Overview
Problem
5G communication systems face significant performance degradation due to frequency-dependent I/Q imbalance, which is not effectively addressed by existing calibration techniques, especially in ultra-wideband transceivers using millimeter waves, leading to mirror-frequency interference and error vector magnitude issues.
Innovation Solution
A loopback hardware structure with specifically designed training signals and compensation filters is used to jointly estimate and compensate for frequency-dependent I/Q imbalance in both transmitter and receiver, employing a method that involves determining loopback gain and phase to calculate frequency domain compensation filters and finite impulse response filters, effectively removing image components from transmission and reception signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing calibration techniques are used in ultra-wideband transceivers, then device complexity is reduced, but manufacturing precision deteriorates due to frequency-dependent I/Q imbalance
Solution Approach 1:
The calibration process is segmented into distinct phases: training signal transmission through separate loopback routes (first and second routes), independent gain and phase estimation for each route, and subsequent application of compensation filters. This segmentation allows precise measurement of frequency-dependent I/Q imbalance characteristics without requiring a monolithic complex calibration structure.
Solution Approach 2:
Training signals serve as intermediaries to facilitate the calibration process. These signals are transmitted through the loopback routes and used to estimate loopback gain and phase, which then enable the determination of compensation filters. The training signals mediate between the physical hardware and the calibration algorithm, enabling precise measurement without direct access to internal mixer characteristics.
2Reliability
If frequency-dependent I/Q imbalance is not compensated, then device complexity remains low, but reliability deteriorates due to mirror-frequency interference
Solution Approach 1:
The calibration system implements feedback by transmitting training signals through loopback routes that return the signals to the receiver. The received training signals are used to estimate loopback gain and phase, which then inform the design of compensation filters applied to subsequent communication signals. This closed-loop feedback mechanism ensures reliable compensation of frequency-dependent I/Q imbalance while maintaining systematic control over the calibration process.
Solution Approach 2:
The calibration process is performed preliminarily before normal communication operations. Training signals are transmitted and processed to determine loopback characteristics and compensation filters in advance. These pre-determined compensation filters are then applied to communication signals, eliminating mirror-frequency interference before it affects system reliability. This preliminary calibration action ensures reliable operation without requiring complex real-time compensation during data transmission.
3Manufacturing precision
If loopback calibration is implemented, then image rejection ratio improves, but loss of time increases due to calibration signaling overhead
Solution Approach 1:
The calibration process uses periodic training signals transmitted through the loopback routes at specific intervals. These periodic training sequences enable the system to estimate loopback gain and phase characteristics efficiently. By confining calibration activities to periodic intervals rather than continuous operation, the system achieves high image rejection ratios while minimizing the time lost to calibration overhead during normal communication periods.
Data Source
AI summary
The disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). A method of operating an electronic device in a wireless communication system is provided. The method includes inputting training signals into a first loopback route and a second loopback route, determining a loopback gain and a loopback phase, based on a first training signal passing through the first loopback route and a second training signal passing through the second loopback route, determining a frequency domain compensation filter, based on the loopback gain and the loopback phase, determining an FIR filter and a DC offset, based on the frequency domain compensation filter, and compensating for a transmission signal and a reception signal, based on the FIR filter and the DC offset.