Ground Plane Filter Module for Carrier Aggregation Isolation
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Solution Overview
Problem
Existing filter modules for multiple carrier aggregation face challenges in reducing size while maintaining sufficient cross isolation between filter bands, as increasing the number of resonators for better band separation leads to increased size and reduced filter capacity.
Innovation Solution
Incorporating a ground plane on the underside of the filter module that substantially surrounds each signal terminal, allowing for improved cross isolation and reduced need for additional resonators, thereby enabling a smaller module with increased filter capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of resonators is increased to improve band separation and cross isolation, then out-of-band rejection is improved, but the filter module size increases and filter capacity decreases
Solution Approach 1:
The patent introduces a ground plane structure on the substrate that extends in the lateral dimension to provide shielding between signal terminals. This dimensional approach to isolation avoids the need to add more resonators in the vertical stacking direction, thereby maintaining compact module size while achieving the required cross isolation between filter bands
Solution Approach 2:
The ground plane acts as an intermediary shielding structure between adjacent signal terminals and filters. By placing this conductive ground plane between the filters, the patent achieves electromagnetic isolation without modifying the resonator structures themselves, thus avoiding the size penalty that would result from adding more resonators
2Manufacturing precision
If the number of resonators is increased to provide sharper rejection for out of band signals, then band pass definition is improved, but filter size increases reducing the number of filters on the module
Solution Approach 1:
The patent segments the isolation function from the filtering function. Instead of using additional resonators within each filter to achieve both filtering and isolation, the design uses a separate ground plane structure dedicated to isolation. This segmentation allows each filter to maintain its compact resonator configuration while the ground plane provides the necessary band pass definition through electromagnetic shielding
Solution Approach 2:
The ground plane extends laterally between filters to provide isolation, creating a spatial barrier that sharpens the effective band pass definition without adding vertical stacking of resonators. This dimensional approach enables multiple filters to coexist on the same module area, increasing overall filter capacity
3Productivity
If filter module size is reduced to increase the number of filters, then filter capacity is improved, but cross isolation between bands deteriorates
Solution Approach 1:
The ground plane is configured to extend beyond the peripheral edges of the filters in the lateral dimension, creating an overlapping shield structure. This dimensional extension provides effective cross isolation between closely-spaced filters, enabling high filter capacity on a compact module while maintaining the required isolation performance through the extended ground plane geometry
Data Source
AI summary
A filter module for multiple carrier aggregation is provided which includes: a substrate having a first side and a second side, a plurality of filters disposed on the first side, a plurality of signal terminals disposed on the second side, each selectively connected to at least one of the plurality of filters and a ground plane disposed on the second side, wherein the ground plane is arranged to substantially surround each signal terminal on the second side and a method of improving cross isolation in a multiple carrier aggregation filter module, where the filter module includes a plurality of filters disposed on a first side of a substrate and a plurality of signal terminals on a second side of a substrate, and where the method includes disposing a ground plane on the second side wherein the ground plane is arranged to substantially surround each signal terminal on the second side.