Detector Feedback Calibration for Digital Filter Transfer Matching
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Solution Overview
Problem
Deriving the transfer function of a signal processing device in a time-efficient manner to program a digital filter is challenging.
Innovation Solution
An apparatus comprising a detector with a signal modification block, comparison block, decimation block, and feedback loop to determine the transfer function, using discrete Fourier transforms and interpolation to derive calibration information for programming the digital filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to derive the transfer function, then measurement accuracy can be maintained, but the process is time-consuming and inefficient
Solution Approach 1:
The patent implements a feedback loop where the measured transfer function is continuously compared with the desired transfer function, and the digital filter coefficients are adjusted based on the error signal. This iterative feedback process enables rapid convergence to the optimal filter configuration, significantly reducing calibration time while maintaining accuracy.
Solution Approach 2:
The system dynamically adjusts digital filter parameters (coefficients) based on the measured transfer function characteristics. By changing these parameters iteratively through the feedback process, the system rapidly adapts the digital filter to match the desired response, achieving fast recalibration without sacrificing measurement precision.
2Measurement precision
If the digital filter is programmed to replicate the transfer function, then signal processing accuracy is improved, but the complexity of the apparatus increases
Solution Approach 1:
The patent creates a digital copy of the analog transfer function characteristics by programming the digital filter with coefficients derived from the measured transfer function. This digital replica accurately reproduces the desired signal processing behavior without requiring complex analog circuitry, thereby improving precision while managing complexity through software-based implementation.
Solution Approach 2:
The system replaces complex analog signal processing hardware with a digital filter implemented in software or firmware. By measuring the transfer function and programming digital filter coefficients to replicate it, the patent substitutes physical analog components with digital processing, reducing hardware complexity while maintaining or improving signal processing accuracy.
3Measurement precision
If multiple frequency points are measured to determine the transfer function, then measurement accuracy is improved, but the time required for calibration increases
Solution Approach 1:
The system performs preliminary measurements at multiple frequency points to fully characterize the transfer function before programming the digital filter. By completing all necessary measurements in advance and then using interpolation to determine intermediate values, the system achieves high accuracy without requiring time-consuming iterative adjustments during operation.
Solution Approach 2:
The calibration process uses periodic frequency sweeping to measure the transfer function at multiple discrete frequency points. This structured periodic measurement approach efficiently captures the complete transfer function characteristics, which are then used to program the digital filter in a single operation, balancing thorough measurement with calibration speed.
Data Source
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AI summary
An apparatus for calibrating a digital filter to replicate a transfer function of a signal processing device comprising a detector with a first input to receive a first signal; a second input to receive a response signal of the signal processing device to the first signal; a signal modification block; a comparison block and a decimation block; wherein the comparison-block compares a phase and amplitude of the first signal after a correction has been applied by the signal modification block and decimation has been applied by the decimation block; and a feedback loop; wherein detector is configured to determine at least a feedback control signal at a first frequency and a second frequency, different to the first frequency and determine calibration information for programming of the transfer function of said digital filter.