RF-MEMS switchable inductors for tunable bandwidth BAW filters

Abstract

This paper presents a method for reconfiguring the bandwidth of Bulk Acoustic Wave (BAW) ladder filters by adding switchable inductors to their shunt resonators. Inductance values are controlled by selecting the number of turn in spiral inductor using micro-electro-mechanical (MEMS) switches. For this purpose, a MEMS inductor has been designed, fabricated and characterized in terms of inductance value, quality factor, and resonance frequency. A measurement-based model of this inductor has been implemented in a circuit simulator to build a reconfigurable RF Ladder BAW filter intended for handset applications. The simulation results show that, using this switchable inductor, it is possible to increase the filter bandwidth by up to 25% with an improved out-of-band rejection and without degrading its selectivity.

A Review of Tunable Inductors for Power Electronics: Techniques and Applications

“…The major drawbacks of that method are: 1) Referring to (1), the magnetic flux intensity is proportional to the number of turns, which means that increasing the number of turns will result in a higher magnetic flux intensity for the same current value; thus, the core will saturate at lower currents, which will effectively lower the current-carrying capability of the power inductor; 2) increasing the number of turns can significantly increase the copper losses as the length of the conductor increases [26]. Although power electronic converters do not currently utilize discrete inductance control except in very rare applications, such as in [34], since it does not provide the complete control range needed to properly optimize these converters, the technology is available and has been presented in [34], [35], and [36]. The switches used can be either solid-state-based such as in [34], or mechanical based such as in [35] and [36].…”

“…Although power electronic converters do not currently utilize discrete inductance control except in very rare applications, such as in [34], since it does not provide the complete control range needed to properly optimize these converters, the technology is available and has been presented in [34], [35], and [36]. The switches used can be either solid-state-based such as in [34], or mechanical based such as in [35] and [36].…”

A novel analytical technique to omit the spurious passband in inductively coupled bandpass filter structures

“…Nowadays, in modern wireless systems, new tunable filters with low insertion loss and excellent power handling capabilities have replaced the old mechanical tunable filters due to existing limitations such as their very large size and highly slow tuning speed [7]. The recently developed microelectromechanical systems commonly known as MEMS have enabled the design and development of a new generation of electronic devices, particularly RF switches.…”

A novel wideband multi‐mode coupled resonator filter based on bulk acoustic wave technology

“…One is adding auxiliary inductors in series/parallel with the shunt/series resonators. 8,9 By utilizing this method, a full band 41 ladder type BAW filter with 7.6% FBW 10 and a modified lattice type filter with 12% FBW 11 were realized. The external inductors improve the k 2 eff by making the resonance frequency f s and the anti-resonance frequency f p of the BAW resonators further apart.…”