Variable-Capacitance Filter Circuit for Switchable Frequency Response
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Solution Overview
Problem
Existing filter circuits are inflexible, as they cannot switch between low-pass and high-pass filtering without reconfiguring the circuit, and they cannot continuously adjust signal gain or phase.
Innovation Solution
A filter circuit design incorporating a first and second resistor, first and second capacitor in series, and a variable capacitance element that allows continuous switching of the pass frequency band by controlling the capacitance of the variable capacitance part between the capacitors and a reference potential node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed filter circuit configuration is used, then the circuit design is simple, but the frequency band cannot be switched freely and multiple filter circuits are required for different filter properties
Solution Approach 1:
The patent applies dynamics by making the capacitor configuration changeable through a switch element. The capacitor can be dynamically connected or disconnected based on control signals, enabling the filter to switch between low-pass and high-pass modes without changing the physical circuit topology. This dynamic reconfiguration resolves the contradiction by providing adaptability while maintaining a single fixed circuit structure.
Solution Approach 2:
The patent implements universality by designing a single filter circuit that can perform multiple filter functions (low-pass and high-pass) through the controlled connection/disconnection of the capacitor. Instead of requiring separate dedicated circuits for each filter type, one universal circuit structure handles both functions, reducing the overall number of components and improving versatility.
2Adaptability or versatility
If a traditional filter circuit is used, then the circuit structure is simple, but the gain and phase of the signal cannot be changed continuously
Solution Approach 1:
The patent applies dynamics by introducing a switchable capacitor that can be dynamically connected or disconnected based on control signals. This dynamic element enables continuous adjustment of the filter's gain and phase characteristics without requiring complex variable component circuits. The simple binary switching mechanism provides adaptable signal processing while maintaining circuit structural simplicity.
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 flexible switching between low-pass and high-pass filtering, allowing continuous adjustment of signal frequency and phase, reducing circuit complexity and size by enabling the same circuit to function as multiple filter types.
Implementation Method 1
a variable capacitance part (8) that switches a capacitance in response to a control signal
Data Source
AI summary
A filter circuit has a first resistor which is connected between an input node and an output node, a second resistor which is connected between the output node and a reference potential node, a first capacitor and a second capacitor which are connected in series between the input node and the output node, and a variable capacity part which is connected between a connection node of the first capacitor and the second capacitor and the reference potential node.