Quadplexer Split Resonator Layout for Passband Ripple Suppression
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Solution Overview
Problem
In multiplexers, such as quadplexers, ripples in the passband of one filter can negatively affect the characteristics of another filter, particularly when the frequency of stopband ripples falls within the passband of the second filter, leading to increased ripples in the second filter's passband.
Innovation Solution
The use of a multiplexer design that includes a series resonator with multiple split resonators, each with different impedance characteristics in a specific frequency range, which cancels out ripples in the passband of the second filter by structuring the series resonator to include first and second split resonators with distinct design parameters, such as varying capacitances and electrode configurations, ensuring that ripples are smoothed and reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multiplexer combines multiple filters with connected paths, then multi-band and multi-mode communication is enabled, but ripples in one filter's stopband can increase ripples in another filter's passband
Solution Approach 1:
The first series resonator is divided into multiple split resonators (first, second, and third split resonators) that are connected in series. Each split resonator has different design parameters, causing their impedance characteristics to include different ripples in the frequency range higher than the anti-resonant frequency. These different ripples cancel each other out, smoothing the overall impedance characteristics and reducing passband ripples in the second filter.
Solution Approach 2:
Each split resonator is designed with specific local characteristics (different design parameters) so that their individual ripple patterns are different. This local differentiation ensures that when combined in series, the ripples from each split resonator interfere destructively in the frequency range that would otherwise affect the second filter's passband, achieving local ripple cancellation in the critical frequency region.
2Device complexity
If a series resonator uses a single resonator design, then the filter structure is simple, but ripples in the impedance characteristics affect another filter's passband
Solution Approach 1:
The single series resonator is segmented into multiple split resonators connected in series. This segmentation increases structural complexity but enables ripple cancellation through the different impedance characteristics of each split resonator, ultimately improving overall filter performance by eliminating harmful ripples in the second filter's passband.
Solution Approach 2:
The split resonators are designed with asymmetric or different design parameters, creating intentional differences in their impedance characteristics. This asymmetry ensures that the ripples generated by each split resonator are different, allowing them to cancel each other out in the frequency range that would otherwise degrade the second filter's passband characteristics.
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 effectively reduces or prevents ripples in the passband of the second filter, improving the power durability and bandpass characteristics of the multiplexer, allowing for better filter performance and reduced ripple generation.
Implementation Method 1
The plurality of split resonators are each an elastic wave resonator including an IDT electrode and a reflector
Implementation Method 2
The plurality of split resonators are each an elastic wave resonator including an IDT electrode and a reflector
Implementation Method 3
The plurality of split resonators are each an elastic wave resonator including an IDT electrode and a reflector, and include first and second split resonators whose impedance characteristics include ripples that are different from each other
Data Source
AI summary
A quadplexer includes a filter of a first duplexer that has a passband with frequencies lower than a filter of a second duplexer. A series resonator closest to a common terminal of the filter includes split resonators that are each an elastic wave resonator including an IDT electrode and a reflector, and include first and second split resonators with impedance characteristics having ripples different from each other in a certain frequency range higher than an anti-resonant frequency of the series resonator closest to the common terminal, that is defined by a pitch of electrode fingers included in the reflector, and that is included in a passband of the filter.