Transceiver Calibration Using Digital Signal Processing
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Solution Overview
Problem
Existing transceiver designs face challenges in efficiently generating and capturing RF signals for calibration, leading to increased circuit cost and complexity, particularly in addressing non-idealities like quadrature imbalance, carrier feedthrough, and dc-offset, which degrade system performance.
Innovation Solution
A method that characterizes and compensates transceiver non-idealities by generating a signal with a known training symbol, up-converting and down-converting it between transmitter and receiver using different but linked frequencies, allowing for characterization and compensation without additional analog circuitry, enabling simultaneous operation and maintaining system operationality during calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior art calibration methods are used to characterize transceiver non-idealities, then calibration accuracy is improved, but circuit cost and complexity increase due to additional analog circuitry and iterative optimization loops
Solution Approach 1:
The patent replaces analog calibration circuitry with digital signal processing. Instead of using additional analog components to generate and measure calibration signals, the system uses digital baseband signals that are up-converted by the transmitter and down-converted by the receiver. The calibration measurements are performed digitally by processing the received baseband signals, eliminating the need for complex analog calibration circuits while maintaining calibration accuracy.
Solution Approach 2:
The transceiver uses its own operational signals for calibration. The transmitter generates a baseband calibration signal that is up-converted and transmitted, then the receiver down-converts and processes this same signal to extract calibration information. This self-contained approach eliminates the need for external calibration equipment or additional dedicated calibration paths, allowing the system to calibrate itself using its normal signal flow.
2Measurement precision
If dedicated calibration signals and iterative optimization loops are used, then non-ideality characterization is improved, but calibration time and system operationality are worsened
Solution Approach 1:
The patent performs calibration using the existing baseband signal that is already being generated for normal operation. Instead of switching to a dedicated calibration mode with specialized signals, the system extracts calibration information from the regular baseband signal before it undergoes up-conversion and transmission. This preliminary extraction of calibration data from operational signals eliminates the need for separate calibration time slots.
Solution Approach 2:
The calibration process occurs continuously during normal transceiver operation without interrupting the signal flow or requiring mode switching. The baseband calibration signal is generated alongside normal data signals, up-converted by the transmitter, transmitted through the RF path, down-converted by the receiver, and processed for calibration extraction all in one continuous operational sequence, maintaining system functionality throughout calibration.
3Reliability
If amplified connection between transmission and reception paths is used for signal transfer, then signal capture is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent uses the RF transmission path itself as the intermediary for transferring the calibration signal from transmitter to receiver. Instead of creating a separate amplified connection or test signal path, the system injects the baseband calibration signal into the normal up-conversion and transmission chain, allowing it to traverse the entire RF path including amplifiers, mixers, and antennas, then be captured by the receiver through normal down-conversion. This uses the existing RF path as the mediator for calibration signal transfer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces design complexity, allows for efficient calibration of transceiver non-idealities, and maintains system performance by minimizing unwanted spectral tones, enabling operational calibration without dedicated calibration signals and iterative optimization loops.
Implementation Method 1
This signal is being up-converted with a first frequency to a first signal in the transmitter
Implementation Method 2
The transferred first signal is being down-converted with a second frequency to a second signal in the receiver
Data Source
AI summary
A method of determining non-ideality characteristics introduced on a signal by a transceiver is disclosed. The transceiver has an up-conversion transmitter and a down-conversion receiver. In one aspect, the method includes: a) generating a signal comprising at least one known training symbol, b) up-converting this signal with a first frequency to a first signal in the transmitter, c) transferring the first signal from the transmitter to the receiver, d) down-converting with a second frequency this transferred first signal to a second signal in the receiver, the second frequency being different from but linked to the first frequency, e) detecting at least one of the training symbols in the second signal; and f) separating, in the frequency domain, at least one of the components of at least one of the detected training symbols for determining the non-ideality characteristics.