Digital Filter Cascade Switching IIR Bandwidth for Settling Time
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Solution Overview
Problem
The settling time of digital filter cascades is disadvantageously reduced due to the significantly poorer settling time of IIR filters compared to FIR filters, leading to inefficient transient response.
Innovation Solution
A digital filter cascade that switches between a first-order IIR filter during stationary operation and a modified IIR filter during the transient process with increased bandwidth, combining good interference dynamics of IIR filters with improved control dynamics of modified IIR filters, achieved by not feeding back the sampled output of the IIR filter into the modified IIR filter and using control signal generation units to determine the valid transient state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an IIR filter is used in the digital filter cascade, then good interference dynamics are achieved with quick attenuation of interference signal components, but the settling time is significantly prolonged due to poor control dynamics
Solution Approach 1:
The patent applies dynamics by making the filter structure switchable between two modes: a first filter structure (IIR filter) for stationary operation with good interference dynamics, and a second filter structure (modified IIR filter with increased bandwidth) for transient processes with improved control dynamics. This dynamic switching resolves the contradiction by adapting the filter characteristics to the operational phase.
Solution Approach 2:
The patent changes the bandwidth parameter of the IIR filter during transient processes by switching to a modified IIR filter structure with increased bandwidth. This parameter change allows the filter to respond faster during transient phases while maintaining the original narrow bandwidth for interference suppression during stationary operation.
2Loss of time
If the bandwidth of the IIR filter is increased during transient process, then the settling time is reduced and control dynamics are improved, but the interference attenuation capability is reduced
Solution Approach 1:
The patent uses dynamic switching between filter structures to resolve this contradiction. During transient processes, the second filter structure with increased bandwidth is activated to reduce settling time. During stationary operation, the first filter structure with original bandwidth is used to maintain good interference attenuation capability.
Solution Approach 2:
The patent implements periodic switching between filter structures based on the operational phase (transient vs. stationary). The switching is triggered by detecting the transient state, creating a periodic pattern of filter structure changes that optimizes performance for each phase.
Data Source
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AI summary
The digital filter cascade has a filter (F IIR) following at least one preceding filter (F DEZ,F M) and with a reduced bandwidth compared to the preceding filter(s) outside the settling process of the filter cascade and a higher bandwidth during the settling period of the filter cascade. The higher bandwidth is achieved by switching from one filter structure to another. An independent claim is also included for a digital filter.