Real-Time FIR Filter Coefficient Generation for High-Order Hardware
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Solution Overview
Problem
In ultrasound imaging systems, existing methods for generating filter coefficients either require large storage capacity for pre-stored coefficients or involve complex and resource-intensive adaptive generation, making them unsuitable for high-order filters with limited programmable device resources.
Innovation Solution
The method calculates filter coefficients in real time based on the varying cut-off angular frequency, using a converted window function table and a sine table, with a look-up table address generated from the current coefficient index, filter order, and cut-off angular frequency, allowing for efficient storage and computation of coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If filter coefficients are pre-stored in on-chip or off-chip storage apparatus, then filtering can be performed, but storage capacity requirements become intolerably high for high-order filters
Solution Approach 1:
The patent extracts only the essential parameters (cut-off angular frequency values) from the complete filter coefficient sets, storing merely these frequency parameters instead of all coefficient data. This extraction reduces storage requirements from storing hundreds of coefficients to storing only the frequency control parameters that generate the coefficients on-demand.
Solution Approach 2:
Instead of storing actual filter coefficients, the patent stores simplified copies in the form of cut-off angular frequency values in a read-only memory. These frequency values serve as compact representations that can regenerate the full coefficient sets when needed, dramatically reducing storage capacity requirements.
2Quantity of substance
If adaptive filter coefficient generation is performed using statistical characteristics of echo data, then storage requirements are reduced, but algorithm complexity and computational time increase significantly
Solution Approach 1:
The patent pre-calculates and stores the cut-off angular frequency values in a read-only memory during system initialization or manufacturing, rather than computing them adaptively during real-time operation. This preliminary action eliminates complex statistical signal processing during runtime, reducing algorithmic complexity while maintaining low storage requirements.
Solution Approach 2:
The patent changes the approach from adaptive parameter generation based on statistical characteristics to using pre-determined frequency parameters stored in read-only memory. This parameter change simplifies the computational algorithm while achieving the same goal of reducing storage requirements for filter coefficients.
3Productivity
If filter coefficients are fetched from storage apparatus in real-time, then filtering can be performed, but the filtering process becomes slower due to memory access delays
Solution Approach 1:
The cut-off angular frequency values are pre-loaded into a read-only memory during system initialization, making them immediately available for rapid coefficient generation during real-time filtering operations. This eliminates the need for complex adaptive calculations or large coefficient sets during runtime, improving filtering speed.
Solution Approach 2:
The patent uses a compact copy of frequency parameters stored in read-only memory that can be rapidly accessed and used to generate filter coefficients in real-time. This compact representation enables fast memory access compared to storing and accessing large sets of pre-computed coefficients.
Data Source
AI summary
The present invention provides a method and device for generating a filter coefficient in real time. The method includes: looking up a converted window function value in a converted window function table based on a current coefficient index; generating a current cut-off angular frequency; generating a look-up table address based on the current coefficient index, the filter order and the current cut-off angular frequency and looking up a sine value in a sine table based on the look-up table address; and multiplying the converted window function value by the sine value to obtain the filter coefficient. The device includes a first memory, a second memory, a look-up table address generation module and a first multiplier. The present invention is easily implemented with low hardware resource consumption and high flexibility, and is particularly applicable for the hardware implementation of high-order finite impulse response filters.