Log-Sampled Multi-Rate Filter for Real-Time Frequency Tuning
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Solution Overview
Problem
High sample rates in FIR filters required for wide-band signals result in excessive complexity and difficulty in real-time adjustments to frequency responses, particularly for non-linearly sampled inputs, due to the need for numerous filter coefficients and complex optimization processes.
Innovation Solution
A multi-rate filter system with a structure that allows for real-time adjustment of frequency response using gain elements associated with the real and imaginary portions of the frequency spectrum, implemented with fewer hardware and software resources, enabling direct specification of the frequency response through downsampling, filtering, and upsampling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high sample rates are used in FIR filters for wide-band signals, then signal quality and frequency coverage are improved, but filter complexity and processing resources increase excessively
Solution Approach 1:
The filter is divided into multiple parallel FIR filter channels, each processing a specific frequency band. Each channel operates at a lower sample rate appropriate for its band, reducing individual channel complexity while maintaining overall high-frequency coverage through parallel processing
Solution Approach 2:
The patent transitions from single-rate linear sampling to multi-rate log sampling in the frequency domain. This dimensional change allows frequency resolution to be optimized independently for different bands, providing high resolution where needed without uniformly increasing complexity across all frequencies
2Manufacturing precision
If numerous filter coefficients are used to specify impulse response for high sample rates, then frequency response accuracy is improved, but real-time adjustment capability deteriorates
Solution Approach 1:
The system enables dynamic real-time adjustment of frequency response by allowing selective modification of coefficients in individual filter channels. This dynamic capability allows the filter to adapt to changing frequency response requirements without requiring complete reconfiguration of all coefficients
Solution Approach 2:
The patent changes the sampling parameter from linear to logarithmic in the frequency domain, allowing frequency response to be specified more efficiently. This parameter change enables accurate frequency response specification with fewer coefficients while maintaining real-time adjustability through gain elements
3Manufacturing precision
If optimization software is used to select filter coefficients, then desired frequency response is achieved, but processing resources and implementation time increase
Solution Approach 1:
The filter is segmented into parallel channels that can be independently configured and optimized. This segmentation allows coefficient selection to be performed separately for each channel, reducing the overall computational burden and enabling more efficient implementation compared to optimizing a single large filter
Data Source
AI summary
This invention provides a filter system which may be implemented with less hardware and software resources than traditional filters. In addition, the filter system structure reduces the complexities typically associated with filter design by permitting direct specification of the filter frequency response. Thus, the filter system may adaptively change the filter frequency response on the fly without incurring excessive time or computational costs. The filter system may provide a filtered signal output to any subsequent processing system, such as a voice recognition system or audio reproduction system.