Variable Filter Circuit Tuning to Prevent Cutoff Heat Buildup
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Solution Overview
Problem
Variable filters in communication devices face issues with excessive heat generation due to the anti-resonant frequency of the resonance portion falling near the cutoff frequency of the pass band, leading to increased insertion loss and potential malfunction or breakdown.
Innovation Solution
A variable filter circuit design that adjusts the resonant and anti-resonant frequencies of the resonance portion to ensure the anti-resonant frequency does not fall near the cutoff frequency, using a series arm and a parallel arm with a variable reactance portion, where the resonant and anti-resonant frequencies satisfy specific conditional expressions to minimize heat generation and maintain optimal insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the variable filter is designed with a resonance portion having adjustable filter characteristics, then the circuit scale is reduced, but the anti-resonant frequency may fall near the cutoff frequency causing excessive heat generation
Solution Approach 1:
The patent applies parameter changes by carefully designing the resonant frequency fr and anti-resonant frequency fa of the resonance portion to satisfy specific mathematical relationships with the cutoff frequency fn. The conditions 100×(fn−fr)/(fa−fr)≤23.9% and −95.2%≤100×(fn−fr)/(fa−fr)≤10.0% ensure that the anti-resonant frequency does not fall near the cutoff frequency, thereby preventing excessive heat generation while maintaining the compact variable filter structure.
2Adaptability or versatility
If the anti-resonant frequency of the resonance portion falls near the cutoff frequency of the pass band, then the filter characteristics are adjustable, but the insertion loss increases and malfunction or breakdown occurs
Solution Approach 1:
The patent uses parameter changes by establishing specific mathematical relationships between the resonant frequency fr, anti-resonant frequency fa, and cutoff frequency fn. By ensuring that 100×(fn−fr)/(fa−fr)≤23.9% and −95.2%≤100×(fn−fr)/(fa−fr)≤10.0%, the design maintains adjustable filter characteristics while preventing the anti-resonant frequency from falling near the cutoff frequency, thus avoiding increased insertion loss and potential breakdown.
Solution Approach 2:
The patent applies preliminary anti-action by pre-designing the resonance portion with specific frequency characteristics that prevent the anti-resonant frequency from falling near the cutoff frequency. This proactive design approach ensures that excessive heat generation and subsequent malfunction or breakdown are prevented before they can occur during operation.
3Adaptability or versatility
If power of a communication signal at approximately the anti-resonant frequency is inputted, then the filter can handle multiple communication bands, but the amount of heat generated becomes large
Solution Approach 1:
The patent applies parameter changes by designing the resonance portion with specific resonant frequency fr and anti-resonant frequency fa that satisfy the conditions 100×(fn−fr)/(fa−fr)≤23.9% and −95.2%≤100×(fn−fr)/(fa−fr)≤10.0% for all communication bands. This ensures that when power of communication signals is inputted, the anti-resonant frequency does not coincide with the cutoff frequency, thereby preventing excessive heat generation while maintaining the ability to handle multiple communication bands.
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
This design improves the electric power handling capability of the variable filter circuit by preventing excessive heat generation and maintaining desired insertion loss across multiple communication bands, thereby enhancing the reliability and efficiency of the filter.
Implementation Method 1
The resonance portion of such a variable filter has low impedance at a resonant frequency thereof. Thus, the amount of heat generated when power of a communication signal at approximately the resonant frequency is inputted is small. On the other hand, the resonance portion has high impedance at an anti-resonant frequency thereof, and thus the amount of heat generated when power of a communication signal at approximately the anti-resonant frequency is large.
Data Source
AI summary
A variable filter circuit includes: a series arm connected in series between a signal input terminal and a signal output terminal; a parallel arm connected between the series arm and a ground terminal that has a resonator; and a variable reactance portion in the parallel arm, and the resonator of a parallel arm at an initial stage connected to the signal input terminal that has a resonant frequency fr and an anti-resonant frequency fa that satisfy 100×(fn−fr)/(fa−fr)≤23.9(%) for communication bands for each of which a stop band is set so as to be close to a high-frequency side of a pass band, among the plurality of communication bands, where a resonant frequency is fr, an anti-resonant frequency is fa, and a cutoff frequency at a high-frequency side of a pass band of each communication band is fn.