Reconfigurable IIR Filter Network for Faster Transient Settling
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Solution Overview
Problem
Digital filters face a trade-off between performance and cost, with sharp transitions requiring longer filters or more complex designs, leading to longer settling times during transients, which negatively impact dynamic performance.
Innovation Solution
A reconfigurable filter network with a first and third infinite impulse response (IIR) filter, and a second IIR filter that operates in acquisition mode when a transient is detected, bypassing the second stage to reduce settling time, allowing quick convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a sharp transition from passband to stopband is implemented to reject out-of-band noise efficiently, then out-of-band rejection performance is improved, but filter length and complexity increase, leading to longer settling time
Solution Approach 1:
The filter dynamically switches between two operational modes: a first mode with sharp transition characteristics for excellent out-of-band rejection, and a second mode with reduced order for fast settling. The monitor circuit detects transients and triggers mode switching, allowing the filter to adapt its characteristics in real-time based on signal conditions.
Solution Approach 2:
The filter changes its transfer function parameters by switching between different operational modes. In the first mode, the filter has parameters optimized for sharp transition and noise rejection. In the second mode, parameters are adjusted to reduce filter order and accelerate settling, achieving parameter optimization for different operational requirements.
2Object-affected harmful factors
If a longer filter or more complex filter design is used to achieve sharp transition, then out-of-band rejection is improved, but device complexity and hardware requirements increase
Solution Approach 1:
The filter structure dynamically reconfigures between a complex high-order configuration for sharp transition and a simpler reduced-order configuration. The monitor circuit controls the switching between these configurations, allowing the system to use complex hardware only when needed for noise rejection, while using simpler hardware for normal operation.
Solution Approach 2:
The same filter hardware performs multiple functions by switching between operational modes: it provides sharp transition and out-of-band rejection when in the first mode, and provides fast settling with reduced complexity when in the second mode. This multi-functionality eliminates the need for separate filters for different requirements.
3Object-affected harmful factors
If a longer filter is used to achieve sharp transition, then out-of-band rejection is improved, but settling time increases, negatively impacting dynamic performance
Solution Approach 1:
The filter dynamically adapts its length and complexity based on operational conditions. During transient events, the monitor circuit triggers a switch to a shorter filter configuration that provides fast settling and maintains dynamic performance. During steady-state operation, the filter switches to a longer configuration for optimal noise rejection, thus maintaining reliability across different operational phases.
Solution Approach 2:
The filter parameters including order, coefficients, and transfer function are changed based on operational mode. In the first mode, parameters are set for sharp transition and noise rejection. In the second mode, parameters are adjusted to reduce filter length and accelerate settling, ensuring dynamic performance is maintained during transients while achieving noise rejection during steady-state.
Data Source
AI summary
A filter circuit includes a first stage comprising a first infinite impulse response (IIR) filter; a third stage comprising a third IIR filter; and a second stage interposed between the first stage and the third stage, the second stage comprising a second IIR filter, where an output terminal of the first IIR filter is coupled to an input terminal of the second IIR filter, and an output terminal of the second IIR filter is coupled to an input terminal of the third IIR filter, where the second stage of the filter circuit is configured to operate in an acquisition mode when a transient is detected in an input signal to the first IIR filter, where during the acquisition mode, the second stage of the filter circuit is bypassed.