Frequency-Shifting Digital Filter for Narrow-Band Signal Suppression
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Solution Overview
Problem
Communication receivers face challenges in achieving good selectivity at low implementation cost for suppressing narrow-band signals, as existing digital filters are either costly or inefficient in filtering out unwanted signals.
Innovation Solution
A digital filter design incorporating frequency shifting mechanisms, signal processors, and decimators/interpolators to efficiently notch unwanted frequency ranges while maintaining low implementation costs, utilizing a combination of frequency shifting, filtering, and signal processing to shift and filter input signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional digital filters are used to suppress narrow-band signals, then selectivity is improved, but implementation cost increases
Solution Approach 1:
The filter is divided into multiple parallel filter banks, each handling a specific frequency range. This segmentation allows each sub-filter to operate independently with reduced complexity, achieving high overall selectivity without requiring a single complex filter structure
Solution Approach 2:
The patent transforms the filtering problem from the time domain to the frequency domain by using FFT-based filter banks. This dimensional transformation enables efficient frequency-selective filtering through simple multiplication in the frequency domain, reducing computational complexity compared to traditional time-domain filtering
2Measurement precision
If complex filtering algorithms are used to achieve good selectivity, then signal suppression performance is improved, but computational effort increases
Solution Approach 1:
The patent replaces complex time-domain filtering operations with frequency-domain multiplication operations using FFT. This substitution transforms computationally intensive convolution operations into simple point-wise multiplications in the frequency domain, dramatically reducing computational effort while maintaining filtering performance
Solution Approach 2:
The patent uses adjustable frequency shift parameters to dynamically reposition the filter banks. By changing the frequency domain parameters rather than redesigning the entire filter structure, the system achieves adaptive signal suppression with minimal computational overhead
Data Source
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AI summary
Digital filter (104), comprising: a first frequency shifting mechanism (106) configured to shift an input spectrum (H(f)) of an input signal (100) by a first frequency distance (F1) to obtain a shifted frequency signal (122) with a shifted spectrum; a filter (108), configured to filter said shifted frequency signal with a predetermined transfer function to obtain a filtered signal (130); and a signal processor (110), said signal processor including: an adder (202), and at least a second frequency shifting mechanism (222), said signal processor (110) being configured to generate an output signal (140), which is a sum of said filtered signal (130) and said shifted frequency signal (122) and said output signal (140) has an output spectrum, which is shifted by a second frequency distance (DF) with respect to said shifted spectrum, wherein said second frequency distance (DF) is independent of said first frequency distance (F1).