Programmable Filter Circuits Using Discrete-Time Window Functions
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Solution Overview
Problem
Existing programmable filters face challenges in efficiently achieving high attenuation levels and wide bandwidths, particularly in applications requiring changing bandwidths, sample frequencies, and passband/stop band frequencies, making it difficult to design filters that accommodate these specifications using traditional approaches.
Innovation Solution
The implementation of programmable filter circuits using a storage element for digital values representing a discrete time window function, coupled with multiplying digital-to-analog converters, capacitors, and sampling devices, allows for programmable filtering by changing the window function and sampling parameters, enabling strong attenuation at integer multiples of the sample frequency and wider bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional RC or LC filter networks are used, then the filter structure is simple, but the attenuation level is insufficient and bandwidth is limited
Solution Approach 1:
The patent replaces traditional mechanical RC/LC filter networks with a digital signal processing approach using MDACs and discrete-time window functions. This substitution enables programmable filtering with superior attenuation characteristics while maintaining circuit simplicity through digital control mechanisms.
Solution Approach 2:
The patent implements programmable filter characteristics by allowing dynamic changes in the discrete-time window function parameters stored in memory. This enables adjustment of bandwidth, sample frequency, and passband/stop band frequencies without physical component changes, achieving high attenuation with flexible parameter control.
2Adaptability or versatility
If multiple different filters are included for different processing functions, then the filtering performance for different frequencies is improved, but the device complexity increases
Solution Approach 1:
The patent creates a universal programmable filter that can perform multiple filtering functions by changing the discrete-time window function stored in memory. A single filter structure with MDACs can be reprogrammed to handle different frequency ranges, bandwidths, and attenuation requirements, replacing the need for multiple dedicated filters.
Solution Approach 2:
The patent implements dynamic reconfigurability where the filter characteristics can be changed in real-time by updating the digital values in the storage element. This allows the same hardware to adapt to different processing functions dynamically, providing versatility without increasing physical complexity.
3Productivity
If the bandwidth is increased to pass more frequency components, then the signal transmission capability is improved, but the attenuation at higher frequencies is reduced
Solution Approach 1:
The patent uses programmable discrete-time window functions with adjustable parameters to independently control bandwidth and attenuation characteristics. By modifying the digital values stored in memory, the system can widen the passband to transmit more frequency components while simultaneously maintaining or enhancing attenuation at specific higher frequencies through the programmable nature of the window function.
Data Source
AI summary
Embodiments of the present invention include programmable filter circuits and methods. In one embodiment, the present invention includes a programmable filter for filtering an input signal comprising a storage element for storing a plurality of digital values representing a discrete time window function, and a plurality of filter channels, each channel comprising a multiplying digital-to-analog converter having a plurality of digital inputs coupled to the storage element and an analog input for receiving said input signal to be filtered, at least one capacitor having at least one terminal coupled to an output of the multiplying digital-to-analog converter, and a sampling device coupled between the at least one terminal of the at least one capacitor and an output of the filter. In another embodiment, the present invention includes a software defined radio.