BAW Bridge Filter With 3D Inductors for 400 MHz Passbands
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Solution Overview
Problem
Existing bandpass filters, particularly bulk acoustic wave (BAW) filters, have limited passband widths, typically less than 100 MHz, which are insufficient for wideband applications such as 5G wireless communication systems that require passbands up to 400 MHz.
Innovation Solution
A wideband filter design incorporating bulk acoustic wave resonators and 3-dimensional inductors is implemented using a combination of through-mold-via and through-glass-via processes on a low-loss substrate like a glass wafer, forming high-Q inductors through metal plating, and integrating these with BAW resonators to achieve a wide passband and sharp rolloff.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional BAW filter designs are used, then the filter structure is simple and easy to manufacture, but the passband width is limited to less than 100 MHz
Solution Approach 1:
The filter is divided into multiple resonators (first, second, third, and fourth resonators) with different resonant frequencies arranged in a bridge configuration. This segmentation allows each resonator to handle specific frequency ranges, collectively achieving a wide passband width exceeding 400 MHz while maintaining manageable structural complexity through modular design
Solution Approach 2:
The patent transitions from planar 2D layouts to 3D vertical structures by stacking resonators and routing signals through multiple layers with via connections. This dimensional change enables complex signal paths and coupling arrangements that achieve wideband performance without excessive lateral space requirements, resolving the contradiction between passband width and structural complexity
2Adaptability or versatility
If the passband width is increased to meet 5G requirements, then the filter meets wideband application needs, but the rolloff becomes less sharp
Solution Approach 1:
Different resonators are assigned specific resonant frequencies (first resonator at lower frequency, second at higher frequency, etc.) with tailored coupling coefficients to adjacent resonators. This local optimization of resonator characteristics enables the overall filter to achieve both wide passband width and sharp rolloff by having each component contribute its specific frequency-selective properties
Solution Approach 2:
The bridge configuration allows dynamic signal paths where signals can travel through multiple routes (direct path, path through first and third resonators, path through second and fourth resonators). This dynamic routing with adjustable coupling enables the filter to maintain sharp transition characteristics across a wide passband by constructively interfering desired frequencies and destructively interfering adjacent frequencies
3Adaptability or versatility
If multiple resonators are integrated on a single IC, then the filter achieves wideband performance, but the manufacturing process becomes more complex
Solution Approach 1:
Multiple resonators and associated interconnection structures are merged onto a single integrated circuit substrate, eliminating the need for separate discrete components and complex interconnect assemblies. This consolidation achieves wideband performance through integrated multi-resonator designs while simplifying manufacturing by reducing assembly steps and improving production consistency
Solution Approach 2:
The IC substrate serves multiple functions simultaneously: it provides the mechanical support structure, the electrical interconnection network through via holes and conductive layers, the mounting platform for resonators, and the routing infrastructure for signal paths. This multi-functionality reduces manufacturing complexity by eliminating separate components for each function
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 design achieves a passband width greater than 400 MHz with a sharp rolloff, addressing the limitations of narrowband BAW filters and meeting the requirements of 5G wireless communication systems.
Implementation Method 1
bulk acoustic wave (BAW) filters
Implementation Method 2
bulk acoustic wave resonators
Implementation Method 3
3-dimensional inductors
Data Source
AI summary
Aspects of the disclosure are directed to a bandpass filter including a first, second, third and fourth resonators, wherein the second and third resonators are in parallel, wherein the first resonator includes a first and second terminals, wherein the second resonator includes a second resonator top terminal and a second resonator bottom terminal, wherein the third resonator includes a third resonator top terminal and a third resonator bottom terminal, wherein the fourth resonator includes a third terminal and a fourth terminal; wherein the first terminal is coupled to the second resonator top terminal, wherein the second terminal is coupled to the third resonator top terminal, wherein the third terminal is coupled to the third resonator bottom terminal, wherein the fourth terminal is coupled to the second resonator bottom terminal; a first inductor coupled to the first and third terminals; and a second inductor coupled to the second and fourth terminals.