AlN MEMS filters with extremely high bandwidth widening capability

Area of Science:

• Electrical Engineering
• Materials Science
• Physics

Background:

• Radio frequency (RF) microelectromechanical system (MEMS) filters are essential components in modern wireless communication systems.
• Existing filter designs often struggle to meet the increasing bandwidth (BW) requirements for advanced applications like 5G New Radio (NR).
• Achieving wide bandwidth and high out-of-band rejection simultaneously remains a significant technological challenge.

Purpose of the Study:

• To present novel hybrid RF MEMS filter topologies capable of significantly widening bandwidth.
• To investigate the performance of filters utilizing Aluminum nitride (AlN) S0 Lamb wave resonators combined with lumped elements.
• To demonstrate an experimentally validated RF MEMS filter that meets stringent 5G NR bandwidth demands.

Main Methods:

• Proposed hybrid filter topologies integrating piezoelectric MEMS resonators with surface-mounted lumped elements.
• Utilized Aluminum nitride (AlN) S0 Lamb wave resonators for center frequency setting and electromechanical coupling.
• Employed lumped-element-based matching networks to enhance bandwidth and out-of-band rejection.
• Experimental implementation and characterization of a first-order wideband filter.

Main Results:

• Demonstrated a first-order wideband RF MEMS filter with a fractional bandwidth (FBW) of 5.6% and insertion loss (IL) of 1.84 dB.
• Achieved a bandwidth widening factor (BWF) of 6, significantly outperforming existing ladder or lattice filter topologies.
• The hybrid design effectively widened bandwidth while maintaining low insertion loss.

Conclusions:

• The proposed hybrid RF MEMS filter topology offers an unprecedented bandwidth widening capability.
• These filters show great potential for meeting the demanding bandwidth requirements of 5G NR bands n77, n78, and n79.
• This technology advancement can overcome critical hurdles in the commercial deployment of 5G NR.