MEMS Tunable Bandpass Filter for Low-Loss Millimeter-Wave Tuning
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Solution Overview
Problem
5G RFFE products face challenges in maintaining low insertion loss, wide stopband suppression, and compact circuit size while handling high power signals and requiring multi-band filtering capabilities in millimeter-wave frequency bands, with MEMS-based solutions experiencing reliability issues and limited functionality over numerous operations.
Innovation Solution
A tunable bandpass filter design incorporating a signal input and output port with a high-pass section using tunable MEMS switch arrays and a low-pass section with tunable MEMS bridge arrays, configured for mirror symmetry and impedance matching, allowing for frequency tuning between 27 GHz and 29 GHz with stable performance over one billion cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional RLC filters are used to filter RF signals, then filtering function is achieved, but insertion loss increases and stopband suppression becomes limited
Solution Approach 1:
The patent replaces conventional RLC circuit elements with MEMS-based mechanical switches and resonators. The MEMS switches use movable capacitive plates to control signal paths mechanically, while MEMS resonators provide frequency-selective filtering through mechanical resonance. This substitution achieves lower insertion loss and better stopband suppression compared to traditional RLC filters.
Solution Approach 2:
The patent employs tunable MEMS switches that can dynamically adjust capacitance values by changing the position of movable plates. This allows the filter to tune its center frequency and bandwidth by varying electrical parameters (capacitance) in response to control voltages, enabling adaptive filtering performance while maintaining low insertion loss.
2Adaptability or versatility
If multi-band filtering is implemented to support different millimeter-wave bands, then adaptability improves, but device complexity increases
Solution Approach 1:
The patent designs a universal MEMS-based filter architecture that can operate across multiple millimeter-wave bands by tuning the MEMS switch capacitances. The same physical filter structure serves multiple frequency bands (e.g., 28 GHz, 38 GHz, 60 GHz) through dynamic parameter adjustment, eliminating the need for separate fixed filters for each band and reducing overall system complexity.
Solution Approach 2:
The patent implements dynamically tunable filtering by using MEMS switches whose capacitance can be adjusted in real-time through applied voltages. This dynamic capability allows a single filter to adapt its center frequency and bandwidth to match different millimeter-wave bands, providing multi-band support without requiring multiple static filter structures.
3Adaptability or versatility
If MEMS switches are used for frequency tuning, then adaptability improves, but reliability decreases over numerous operations
Solution Approach 1:
The patent designs the MEMS switches with pre-engineered mechanical structures including optimized beam thickness, support configurations, and electrostatic actuation parameters. These design features provide mechanical cushioning and stress distribution that prevent fatigue failure during repeated switching operations, ensuring reliable frequency tuning over billions of cycles.
Solution Approach 2:
The patent employs different structural designs for different parts of the MEMS device. The movable capacitive plates use localized thickening at critical stress points, while the support beams have optimized cross-sections for mechanical strength. This local quality enhancement ensures that high-stress regions have sufficient mechanical resilience to withstand frequent actuation while maintaining electrical performance.
4Power
If high power signals are handled to meet 5G requirements, then power handling capability improves, but performance degradation increases
Solution Approach 1:
The patent replaces conventional RLC components with MEMS-based mechanical structures that have higher power handling capabilities. The MEMS switches use air gaps and mechanical contact designs that can withstand high RF power levels without breakdown, while MEMS resonators provide high-Q filtering that maintains signal integrity even under high power conditions, preventing performance degradation.
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 low insertion loss, high isolation, and reliable operation across the specified frequency range with minimal center frequency shift, supporting efficient 5G communication by maintaining performance and reducing circuit size while handling high power signals.
Implementation Method 1
a first bias voltage applied to a plurality of microelectromechanical system (MEMS) switches of a first tunable MEMS switch array and a second plurality of MEMS switches of a second tunable MEMS switch array having a mirror symmetry with the first tunable MEMS switch array, wherein the first bias voltage tunes the first and second tunable MEMS switch array to a common high-pass roll-off frequency
Implementation Method 2
Waveguide and cavity filters store signals in the form of electromagnetic resonance at their transmission lines or in the cavity
Data Source
AI summary
A tunable passband filter including a signal input port for receiving an input radio frequency (RF) signal, a signal output port for transmitting a filtered output RF signal, a first high-pass section having a first tunable microelectromechanical system (MEMS) switch array to receive the input RF signal from the signal input port, a second high-pass section having a second tunable MEMS switch array to transmit the output RF signal to the signal output port, and a low pass section operatively coupled between the first high-pass section and the second high-pass section, and having each of a first tunable MEMS bridge array, a second tunable MEMS bridge array, and a high impedance line. The tunable passband filter is configured to filter the input RF signal to yield the filtered output RF signal.