Stacked Passive-on-Glass Acoustic Filter for Low-Loss RF Roll-Off
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Solution Overview
Problem
Conventional technologies face challenges in fabricating high-performance filters with low insertion loss while achieving sharp filter roll off and increased bandwidth, which is crucial for carrier aggregation applications in wireless communications.
Innovation Solution
An integrated radio frequency circuit is designed by stacking and coupling multiple dies, including a substrate with passive devices and acoustic filters, such as bulk acoustic wave or surface acoustic wave filters, to reduce insertion loss and enhance filter performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional technologies (e.g., low temperature co-fired ceramic devices) are used to fabricate filters, then manufacturing is relatively simple, but insertion loss is high and filter performance is poor
Solution Approach 1:
The filter is divided into multiple functional layers including acoustic wave resonators, capacitive elements, and inductive elements fabricated on separate substrates that are then stacked and interconnected. This segmentation allows each layer to be optimized independently for low loss while maintaining manufacturing feasibility through modular assembly processes
Solution Approach 2:
The invention employs composite structures combining piezoelectric materials for acoustic wave resonators, conductive materials for inductive elements, and dielectric materials for capacitive elements. This composite approach enables simultaneous achievement of low insertion loss through material optimization and manageable fabrication through specialized processing techniques
2Loss of energy
If filter design is optimized for low insertion loss, then signal propagation efficiency improves, but achieving sharp filter roll off and increased bandwidth becomes more difficult
Solution Approach 1:
Different regions of the filter structure are designed with locally optimized properties: acoustic wave resonators provide sharp frequency selectivity in specific bands, while distributed capacitive and inductive elements provide broadband matching. This local quality differentiation enables simultaneous achievement of low insertion loss across the bandwidth and sharp roll-off at filter edges
Solution Approach 2:
The filter design transitions from planar two-dimensional layouts to three-dimensional stacked architectures. By utilizing the vertical dimension with multiple layers of resonators and interconnects, the filter achieves enhanced frequency selectivity and sharper roll-off characteristics while maintaining low insertion loss through optimized signal paths in three dimensions
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 integrated circuit achieves low insertion loss of less than 0.2 dB, enabling efficient signal propagation and sharp filter roll off, thereby improving carrier aggregation capabilities and reducing signal power loss.
Implementation Method 1
a second die including a first acoustic filter. The second die is stacked and coupled to a first surface of the first die
Implementation Method 2
The second die is stacked and coupled to a first surface of the first die
Data Source
AI summary
An integrated radio frequency (RF) circuit combines complementary features of passive devices and acoustic filters and includes a first die, a second die, and a third die. The first die includes a substrate having one or more passive devices. The second die includes a first acoustic filter. The second die is stacked and coupled to a first surface of the first die. The third die includes a second acoustic filter. The third die is stacked and coupled to a second surface opposite the first surface of the first die.