RF Filter Switching Circuit for Passband Edge Loss Control
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Solution Overview
Problem
Tunable radio-frequency filters face challenges in maintaining low loss and attenuation across the pass band edges due to the formation of new attenuation poles, leading to increased insertion loss and attenuation deterioration at specific frequency edges.
Innovation Solution
A radio-frequency filter design incorporating a series arm circuit with a variable frequency circuit and a parallel arm circuit, where the resonant frequencies and anti-resonant frequencies are adjusted by switching a switch, allowing for the creation of new attenuation poles on either side of the pass band to minimize loss and improve attenuation, particularly at the lower and higher edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a switch is connected in parallel with a parallel arm resonator to enable frequency tuning, then the filter can switch between different frequency bands, but a new attenuation pole appears between the pass band and the higher side, causing deterioration of attenuation on the lower side of the pass band
Solution Approach 1:
A third resonator is introduced as an intermediary element between the first parallel arm resonator and the switch. This third resonator acts as a mediator that shapes the attenuation pole characteristics, ensuring that when the switch transitions between on and off states, the resulting attenuation poles are positioned appropriately to maintain filter performance while enabling frequency band switching.
Solution Approach 2:
The invention changes the parameters of the resonant circuit by introducing a third resonator with specific resonant frequency characteristics. By carefully selecting the resonant frequency of the third resonator relative to the first parallel arm resonator, the system achieves frequency band switching while controlling the position and characteristics of attenuation poles to prevent performance deterioration.
2Adaptability or versatility
If the first attenuation pole frequency is switched toward the pass band by changing switch state, then frequency tuning is achieved, but the difference between the second attenuation pole and the new third attenuation pole becomes too large, causing loss deterioration at pass band edges
Solution Approach 1:
The third resonator serves as an intermediary that fills the frequency gap between existing attenuation poles. When the switch state changes and creates a new attenuation pole, the third resonator ensures that the frequency spacing between adjacent attenuation poles remains appropriate, preventing excessive insertion loss at pass band edges while maintaining frequency tuning capability.
Solution Approach 2:
The system dynamically adjusts the attenuation pole positions by changing switch states, and the third resonator is designed to work with this dynamic behavior. The resonant frequency of the third resonator is specifically chosen to compensate for the dynamic shifts in attenuation pole positions, ensuring that loss characteristics are maintained across different operating states.
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 configuration effectively reduces loss at the higher edge of the pass band and improves attenuation on the lower side, and vice versa, by strategically placing new attenuation poles within the pass band, thereby optimizing filter performance.
Implementation Method 1
a first series arm resonator provided in the path, and a first variable frequency circuit connected in parallel with the first series arm resonator... an anti-resonant frequency that provides an attenuation pole of the radio-frequency filter
Data Source
AI summary
A radio-frequency filter (10) includes a series arm circuit (11) and a parallel arm circuit (12). The series arm circuit (11) includes a series arm resonator (s1a) and a variable frequency circuit (11b) connected in parallel with the series arm resonator (s1a). The variable frequency circuit (11b) includes a series arm resonator (s1b) and a switch (SWb) connected in series with the series arm resonator (s1b). The variable frequency circuit (11b) is configured to change at least one of a resonant frequency that provides a pass band of the radio-frequency filter (10) and an anti-resonant frequency that provides an attenuation pole of the radio-frequency filter (10). A resonant frequency of the series arm resonator (s1b) is different from a resonant frequency of the series arm resonator (s1a).