Programmable Filter With Switched Variable Inductance
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Solution Overview
Problem
Conventional filters do not provide perfect linear cutoffs at their pass bands and stop bands, and their rolloff rates are limited, requiring additional stages to achieve higher-order filters with improved rolloff rates.
Innovation Solution
A programmable filter design using variable capacitors and inductors with switchable configurations, allowing for selectable passbands and cutoff frequencies by controlling the capacitance and inductance values, implemented in an integrated circuit with discrete stages and solid-state switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional stages are added to increase rolloff rate, then filtering performance is improved, but device complexity increases
Solution Approach 1:
The patent implements a fifth-order filter using a dynamic switching network that can reconfigure capacitor connections through control signals. This allows the filter to achieve high-order filtering performance (−100 dB/decade rolloff) through dynamic switching rather than static multi-stage configurations, reducing device complexity while maintaining filtering performance.
Solution Approach 2:
The patent changes the electrical parameters of the filter by switching between different capacitor configurations. By dynamically altering capacitance values through the switching network, the filter achieves variable cutoff frequencies and maintains fifth-order performance without requiring multiple fixed stages, thereby reducing overall device complexity.
2Adaptability or versatility
If variable capacitors and inductors are used to create programmable filters, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent creates a universal filter structure where a single fifth-order filter circuit can be programmed to achieve different cutoff frequencies and filtering characteristics through control signals. The switching network allows one circuit to perform multiple filtering functions, eliminating the need for separate circuits for each filtering requirement and thereby reducing overall device complexity.
Solution Approach 2:
The patent uses dynamic switching networks controlled by digital signals to reconfigure capacitor connections in real-time. This dynamic reconfiguration enables programmable filtering characteristics without requiring physical changes to the circuit structure, achieving adaptability while maintaining a compact single-circuit design rather than multiple fixed circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables programmable filters with selectable passbands and cutoff frequencies, achieving a rolloff rate of approximately −100 dB/decade in a fifth-order low-pass filter, suitable for various signal bandwidths in communications and other applications.
Implementation Method 1
the reactive impedance of inductors and capacitors are used to form filters
Implementation Method 2
the reactive impedance of inductors and capacitors are used to form filters
Data Source
AI summary
In one example embodiment, a programmable filter is provided, including a plurality of variable-inductance networks and a plurality of variable-capacitance networks. The programmable filter may be implemented in a classical filter topology, with variable-capacitance networks replacing discrete capacitors and variable-inductance networks replacing discrete inductors. An example variable-inductance network comprises a primary inductor with an intermediate tap, and secondary inductor connected at the intermediate tap, with switches for selecting an inductance.