Tunable RF Filter Circuit with Coupled Resonant Circuits
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Solution Overview
Problem
Existing RF filter circuits optimized for constant impedance elements suffer performance degradation when made tunable, limiting their effectiveness in a wide tuning range and requiring complex circuitry for multiple frequency bands.
Innovation Solution
A tunable RF filter circuit with a signal path comprising parallel resonant circuits, each connected to ground and electrically or magnetically coupled, using tunable impedance elements to adjust bandwidth and center frequency, with a control logic to simplify impedance value control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If known filter topologies are extended with tunable impedance elements, then filter tunability is achieved, but performance is detrimentally affected
Solution Approach 1:
The patent changes the fundamental parameter of impedance elements from constant to variable/tunable. By using tunable impedance elements with continuously adjustable values, the filter can adapt its characteristics (center frequency, bandwidth) while maintaining optimal performance through controlled parameter variation rather than discrete switching.
Solution Approach 2:
The patent transforms the static filter topology into a dynamic system where impedance elements can continuously adjust their values. This dynamic capability allows the filter to maintain optimal performance across different tuning states by adapting its electrical characteristics in real-time rather than relying on fixed configurations.
2Adaptability or versatility
If multiple filters are interconnected for different frequency bands, then frequency band coverage is increased, but circuit complexity increases
Solution Approach 1:
The patent creates a universal filter topology that can operate across multiple frequency bands through a single circuit configuration. By using tunable impedance elements, one filter circuit can replace multiple fixed-frequency filters, achieving multi-band functionality without requiring separate filter circuits for each frequency band.
Solution Approach 2:
The patent merges the functionality of multiple frequency-specific filters into a single tunable filter circuit. By combining constant impedance elements with tunable impedance elements in a unified topology, the circuit achieves multi-band operation while reducing the total component count and interconnection complexity compared to using separate filters for each band.
3Adaptability or versatility
If switches are used to reconfigure filters, then reconfigurability is achieved, but continuous tuning capability is lost
Solution Approach 1:
The patent replaces the mechanical/discrete switching system with an electronic/continuous control system. Instead of using switches that abruptly change circuit configurations, the patent uses tunable impedance elements that can be controlled electronically to provide continuous adjustment of filter characteristics, enabling smooth tuning without discrete steps.
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
The solution provides high edge steepness and adjustability of passband edges with low circuit complexity and minimal driving requirements, enabling efficient operation across multiple frequency bands with reduced component count.
Implementation Method 1
N≥3—that is to say three or more—resonant circuits are arranged one after another in the second signal route and in each case interconnect the second signal route with ground. The resonant circuits are electrically or magnetically coupled to one another
Implementation Method 2
Each resonant circuit comprises at least one tunable impedance element. The resonant circuits are electrically or magnetically coupled to one another and each comprise at least one tunable impedance element
Data Source
AI summary
A tunable RF filter circuit (AHF) is specified which enables good electrical properties, good tunability and simple driving despite low complexity. In this case, the filter circuit comprises a first and a second signal route (SW1, SW2) in a signal path (E, A). At least three resonant circuits (RK1, RK2, RK3) are arranged one after another in the second signal route and interconnect the second signal route with ground. The resonant circuits are electrically and/or magnetically coupled (K) and each comprise a tunable impedance element. The second signal route contains an impedance element (IMP).