Mobile Transceiver Self-Calibration for DC Offset and I/Q Imbalance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional mobile transceivers face performance degradation due to DC offset and I/Q imbalance, which are difficult to accurately calibrate using existing methods that require separate diodes, registers, and switches, leading to incorrect gain and phase imbalance estimations.
Innovation Solution
A method for self-calibration in a transceiver that uses test signals transmitted from the transmission side and received on the reception side to estimate and calibrate DC offset and imbalance characteristics, employing a Digital Signal Processor (DSP) to generate and process test signals, calculate calibration values, and adjust the transceiver's baseband signals to achieve symmetry between in-phase and quadrature-phase channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate diodes, registers, and switches are used for calibration, then calibration accuracy may improve, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple calibration functions (DC offset calibration and I/Q imbalance calibration) into a single integrated calibration circuit that uses shared components. The calibration circuit uses the same signal path and processing resources for both calibration types, eliminating the need for separate diodes, registers, and switches for each calibration function. This merging approach maintains calibration accuracy while significantly reducing device complexity.
Solution Approach 2:
The calibration circuit is designed with multi-functionality to perform both DC offset calibration and I/Q imbalance calibration using the same hardware resources. The circuit can switch between different calibration modes and uses universal processing elements that handle both calibration tasks, thereby avoiding the proliferation of dedicated components for each calibration type.
2Reliability
If symmetric mixers are designed to reduce I/Q imbalance, then signal quality improves, but volume and current consumption increase
Solution Approach 1:
The patent implements a self-calibration mechanism that automatically detects and corrects I/Q imbalance without requiring manual adjustment or additional power-intensive hardware. The calibration circuit uses the existing signal path and components to perform self-diagnosis and self-correction, thereby maintaining signal quality while avoiding increased current consumption that would result from more complex symmetric mixer designs.
Solution Approach 2:
The patent replaces the mechanical approach of designing physically symmetric mixers with an electronic calibration approach. Instead of relying on precise physical symmetry in the mixer hardware, the system uses digital signal processing and calibration algorithms to compensate for I/Q imbalance, thereby achieving the same signal quality without the increased current consumption associated with symmetric mixer design.
3Measurement precision
If TX calibration is performed before RX calibration, then calibration sequence is established, but calibration time and complexity increase
Solution Approach 1:
The patent performs preliminary calibration of the transmission path before receiving signal calibration, using a predefined calibration sequence. The TX calibration is conducted first with known test signals to establish baseline parameters, which then inform the subsequent RX calibration process. This preliminary action approach ensures accurate calibration while optimizing the sequence to minimize total calibration time.
Solution Approach 2:
The calibration process is designed as a continuous workflow where the output of TX calibration directly feeds into the RX calibration without interruption. The system maintains calibration state information and uses it seamlessly across both calibration phases, avoiding redundant measurements and maintaining continuous useful action throughout the calibration process.
Data Source
AI summary
Disclosed is a method and an apparatus for self-calibrating direct current (DC) offset and imbalance between orthogonal signals, which may occur in a mobile transceiver. In the apparatus, a transmitter of a mobile terminal functions as a signal generator, and a receiver of the mobile terminal functions as a response characteristic detector. Further, a baseband processor applies test signals to the transmitter, receives the test signals returning from the receiver, and compensates the imbalance and DC offset for the transmitter side and the receiver side by using the test signals.