Duplexer Receiving Filter Layout for High-Band Attenuation
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Solution Overview
Problem
Conventional duplexers face challenges in improving the isolation and attenuation (ATT) of the receiving filter in high-frequency bands, particularly when the transmission filter operates in this band, making it difficult to enhance the ATT of the receiving filter.
Innovation Solution
A duplexer design with a receiving filter comprising series and parallel resonators, where the second parallel resonator has a higher resonant frequency and smaller capacitance, and its reflector's wavelength is limited to 0.965 times the central position wavelength, allowing selective adjustment of the Q value for anti-resonance to improve ATT in the high-frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transmission filter filters a high-frequency band and the receiving filter filters a low-frequency band, then the duplexer supports multiband communication, but the isolation and attenuation of the receiving filter in the high-frequency band deteriorates
Solution Approach 1:
The patent adjusts the resonant frequency and capacitance parameters of the parallel resonators, specifically setting the second parallel resonator's resonant frequency higher than the first, and controlling the reflector wavelength to be no more than 0.965 times the central position wavelength. This parameter optimization enables the receiving filter to achieve improved attenuation in the high-frequency band while maintaining multiband communication capability
Solution Approach 2:
The patent applies different structural configurations to different parts of the receiving filter. The first parallel resonator has different characteristics than the second parallel resonator, with the second having higher resonant frequency and smaller capacitance. This localized differentiation allows the filter to handle both low-frequency passband signals and high-frequency attenuation requirements effectively
2Reliability
If the second parallel resonator has higher resonant frequency and smaller capacitance, then the Q value for anti-resonance can be selectively adjusted, but the device complexity increases
Solution Approach 1:
The patent optimizes specific parameters including setting the reflector wavelength to no more than 0.965 times the central position wavelength, and configuring the second parallel resonator with higher resonant frequency and smaller capacitance than the first. These parameter changes enable selective adjustment of the Q value for anti-resonance, achieving improved attenuation without requiring fundamentally new structural concepts
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 duplexer achieves improved attenuation levels in the high-frequency band by selectively controlling the Q value, enhancing the receiving filter's performance.
Implementation Method 1
the receiving filter comprises at least two or more series resonators connected in series; and two or more parallel resonators connected in parallel, respectively, to the series resonators
Data Source
AI summary
Provided is a duplexer connected to an antenna to receive and transmit signals in different frequency bands, the duplexer comprising a receiving filter and a transmission filter, wherein the receiving filter filters a low-frequency band of the same band being used and the transmission filter filters a high-frequency band of the same band, wherein the receiving filter comprises at least two or more series resonators connected in series; and two or more parallel resonators connected in parallel, respectively, to the series resonators, a first parallel resonator and a second parallel resonator, which constitute the parallel resonators, are sequentially connected closest to the antenna, and the second parallel resonator has a relatively higher resonant frequency than the first parallel resonator.