Half-Ladder Resonator Filter Cross-Coupling for Stopband Rejection
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Solution Overview
Problem
Current duplexers in portable communication devices face challenges in reducing size, weight, fabrication costs, and improving performance characteristics such as insertion loss and out-of-band attenuation, while operating at higher frequencies and complying with various communication standards like UMTS.
Innovation Solution
The design incorporates resonator filters with half-ladder topology, utilizing thin film bulk acoustic resonators (FBARs) and cross-coupling elements like common ground inductors and cross-coupling capacitors to shift transmission zeros into the stopbands, achieving near-ideal elliptic filter performance and reducing the need for large external inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If resonator filters with half-ladder topology and cross-coupling elements are used, then out-of-band attenuation is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the resonator filter structure itself. The half-ladder topology integrates series and shunt resonators in a compact configuration, while cross-coupling elements (inductors and capacitors) are embedded within the filter to simultaneously achieve out-of-band attenuation and transmission zero shifting without requiring separate external components.
Solution Approach 2:
The patent introduces cross-coupling paths that create additional signal transmission paths through the filter structure. By adding these dimensional connections between non-adjacent resonators, the filter achieves elliptic response characteristics and improved stopband attenuation without significantly increasing the physical footprint.
2Object-affected harmful factors
If cross-coupling elements are added to shift transmission zeros, then out-of-band rejection is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses variable reactance elements (inductors and capacitors) with adjustable parameters to optimize filter performance. By carefully selecting and tuning the L and C values in the cross-coupling elements, the design achieves desired transmission zero positions and out-of-band rejection characteristics while accommodating standard manufacturing tolerances.
3Loss of energy
If more cross-coupling elements are used, then insertion loss is reduced, but device size increases
Solution Approach 1:
The patent merges the cross-coupling elements with the existing resonator structure, using shared components and integrated layouts. The inductors and capacitors are positioned to utilize available space efficiently, and the half-ladder topology allows for compact arrangement that minimizes the overall filter footprint while maintaining multiple coupling paths.
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 results in smaller device size, improved out-of-band rejection, reduced insertion loss, and increased product yields, while maintaining performance across different frequency bands.
Implementation Method 1
utilizing thin film bulk acoustic resonators (FBARs)
Implementation Method 2
cross-coupling elements like common ground inductors and cross-coupling capacitors to shift transmission zeros into the stopbands
Data Source
AI summary
A filter device is provided for filtering signals. The filter device includes multiple series resonators, multiple shunt resonators and multiple cross-coupling circuits. The series resonators are connected in series between an antenna and one of a transmitter or a receiver. The shunt resonators are respectively connected between at least one of the series resonators and a ground voltage. The cross-coupling circuits are configured to bypass at least two series resonators of the multiple series resonators and at least one shunt resonator of the multiple shunt resonators.