Frequency-Domain Digital Filter Coefficient Simplification
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Solution Overview
Problem
The existing digital filter circuit requires complex and time-consuming processes for changing filter coefficients, leading to increased circuit size and power consumption due to the correlation between complex-number coefficients.
Innovation Solution
A digital filter circuit that separates complex-number signals into real and imaginary parts in the frequency domain, generates independent frequency-domain filter coefficients, and performs filtering processes on each part separately, allowing for easy coefficient adjustments and reduced circuit size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filtering is performed in the time domain using FIR or IIR filters, then filtering functionality is achieved, but circuit size and power consumption become enormous when large number of taps are required
Solution Approach 1:
The patent replaces time-domain filtering operations with frequency-domain operations. By transforming the filtering process from time domain to frequency domain using FFT, the complex convolution operations are converted to simple multiplications, dramatically reducing the computational complexity and circuit size required for implementing filters with large numbers of taps.
Solution Approach 2:
The patent changes the domain parameter from time domain to frequency domain. This fundamental parameter change allows the same filtering functionality to be achieved with significantly reduced computational resources by exploiting the properties of frequency-domain operations, where convolution becomes multiplication.
2Reliability
If complex-number FFT is used to transform complex-number signals, then complete signal transformation is achieved, but the process of changing filter coefficients becomes complicated and time-consuming
Solution Approach 1:
The patent segments the complex-number signal processing into separate real part and imaginary part processing. By separating the complex signal into its real and imaginary components and processing them independently in the frequency domain, the patent simplifies the coefficient changing process and reduces the computational overhead associated with complex-number operations.
Solution Approach 2:
The patent uses the property that the imaginary part of the FFT output can be obtained by copying and processing the real part with modified coefficients. This approach reduces the computational burden by reusing processing paths and results, thereby reducing the time required for coefficient changes.
3Measurement precision
If complex-number calculation is performed for filter calculation in frequency domain, then accurate filtering is achieved, but power consumption increases
Solution Approach 1:
The patent segments complex-number calculations into separate real and imaginary part calculations. By processing the real and imaginary parts independently and only performing necessary complex multiplications, the patent reduces the total number of computational operations required, thereby reducing power consumption while maintaining filtering accuracy.
Solution Approach 2:
The patent performs only the necessary complex-number calculations required for accurate filtering rather than full complex-number processing. By optimizing the calculation to perform only essential operations and exploiting symmetries in the frequency domain, the patent achieves accurate filtering with reduced computational effort and lower power consumption.
Data Source
AI summary
Provided is a digital filter circuit in which a filter coefficient can be easily changed, for which circuit scale and power consumption can be reduced, and which carries out digital filter processing in a frequency domain. This digital filter circuit includes: a separating circuit for separating a first complex number signal, of a frequency domain that was subjected to Fourier transform, into a real number portion and an imaginary number portion; a filter coefficient generating circuit for generating a first frequency domain filter coefficient from a first input filter coefficient and a third input filter coefficient, and for generating a second frequency domain filter coefficient from a second input filter coefficient and the third input filter coefficient; a first filter that filters the separated real number portion using the first frequency domain filter coefficient; a second filter that filters the separated imaginary number portion using the second frequency domain filter coefficient; and a combining circuit for combining the output from the two filters.