Parallel Lattice MEM Filter for Wider CMOS-Integrated Bandwidth
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Solution Overview
Problem
Existing microelectromechanical (MEM) filters face limitations in achieving wide bandwidths necessary for high data rate communication systems, particularly in integrating large percent bandwidth filters directly into CMOS chips using SAW, BAW, and FBAR technologies.
Innovation Solution
The development of MEM filters utilizing a plurality of lattice networks formed from contour-mode resonators, which are electrically connected in parallel, allowing for independent setting of series and shunt resonant frequencies to achieve arbitrary percent bandwidths up to 5%, and are compatible with CMOS technology for direct integration into CMOS integrated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If surface acoustic wave (SAW) devices are used to achieve large percent bandwidth filters, then bandwidth is improved, but ease of integration into CMOS chips deteriorates because SAW devices are hybrid devices not easily integrated directly into CMOS chips
Solution Approach 1:
The patent replaces hybrid SAW devices with a fully integrated MEMS-based filter system that uses piezoelectric materials (such as AlN or ZnO) deposited on CMOS circuitry. This substitution eliminates the need for hybrid assembly by directly forming resonators on the CMOS chip, achieving both wide bandwidth and seamless integration.
Solution Approach 2:
The patent employs composite material structures combining piezoelectric layers (AlN, ZnO, or PZT) with CMOS technology. The piezoelectric materials are deposited using atomic layer deposition (ALD) or chemical vapor deposition (CVD) to form resonators that operate at intermediate frequencies, enabling wide bandwidth filters that are fully integrated with CMOS circuitry.
2Ease of manufacture
If bulk acoustic wave (BAW) and film bulk acoustic resonator (FBAR) technologies are used to form filters, then integration into CMOS chips is improved, but bandwidth capability deteriorates for large percent bandwidth filters
Solution Approach 1:
The patent changes the operating parameters by using contour-mode resonators with specific geometric configurations (such as interdigitated electrodes arranged in lattice networks) that enable wide bandwidth operation. The resonators are designed with specific width-to-length ratios and electrode patterns that optimize the bandwidth while maintaining CMOS compatibility, achieving percent bandwidths of 1% or more at intermediate frequencies.
3Device complexity
If a single lattice network is used in the MEMS filter, then device complexity is reduced, but bandwidth flexibility deteriorates because arbitrary percent bandwidth cannot be achieved
Solution Approach 1:
The patent segments the filter into multiple lattice networks (typically two or more) that are electrically connected in parallel. Each lattice network operates at a different resonant frequency, and by combining these segmented networks, the filter achieves arbitrary percent bandwidths while maintaining manageable device complexity through modular design.
Solution Approach 2:
The patent creates a universal filter design where the same basic lattice network structure can be configured for different bandwidth requirements by adjusting the resonant frequencies of individual networks. This multi-functional approach allows a single device architecture to serve various bandwidth needs from narrowband to wideband applications.
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 solution enables MEM filters to provide flexible bandwidth options from 0.25% to 5% and integrates seamlessly with CMOS technology, enhancing the performance of communication systems by allowing for broader bandwidths and improved filter characteristics.
Implementation Method 1
Each lattice network has a series resonant frequency and a shunt resonant frequency and comprises at least one contour-mode resonator to provide the series resonant frequency and the shunt resonant frequency
Data Source
AI summary
A microelectromechanical (MEM) filter is disclosed which has a plurality of lattice networks formed on a substrate and electrically connected together in parallel. Each lattice network has a series resonant frequency and a shunt resonant frequency provided by one or more contour-mode resonators in the lattice network. Different types of contour-mode resonators including single input, single output resonators, differential resonators, balun resonators, and ring resonators can be used in MEM filter. The MEM filter can have a center frequency in the range of 10 MHz-10 GHz, with a filter bandwidth of up to about 1% when all of the lattice networks have the same series resonant frequency and the same shunt resonant frequency. The filter bandwidth can be increased up to about 5% by using unique series and shunt resonant frequencies for the lattice networks.