Method of Varying Resonant Frequency in Capacitance Type Radio Frequency (RF) Micro-electro-mechanical System (MEMS) Switches

Technology: RF MEMS Switch;

Industry & Application: RF MEMS Switch, Electronic System & Design Manufacturing;

Market: The global RF MEMS Switch market is projected to grow at a CAGR of 11.1% during 2024-2030.

In the conventional RF MEMS switches, said switch is suspended above the bottom electrode and the movable membrane (beam) is anchored on the ground planes, bridging them across the signal line.
One of the issue disclosed that the interface at the contact of the beam & the bottom electrode is not always perfect which can reduce the down-state capacitance from the expected value. Due to this, it increases the value of resonant frequency.
Hence, there is a need to address the issues.
Present invention provides the solution of the problem arising in RF MEMS switches related to variation in resonant frequency.

Present invention describes a method for varying the resonant frequency (fo) in a capacitance type radio frequency (RF) Micro-Electro-Mechanical Sysytem (MEMS) switch.
Further, the present invention explains also about a capacitance type radio frequency Micro electric mechanical system. (Refer Fig.2)
The claimed method comprising following few steps illustrated in the smart chart:

Further the process is illustrated using a graph showing the variation of a down state capacitance with a length of the floating Matel (LFM).
Furthermore, the claimed invention deals with a capacitance type RF MEMS which is depicted in Fig. 2.
Said RF MEMS comprising a substrate, a lower electrode formed on said substrate; a dielectric layer formed on said lower electrode; a floating metal encapsulated on said dielectric layer; a beam connected to a ground.
Further, the length of the floating metal is varied to vary said resonant frequency by computing a down-state capacitance (Cd) between said beam & said floating metal.

Technical Perspective:

The RF MEMS capacitive switches can be used to make tunability easier to achieve any frequency of operation.
The lengths of the floating metal chosen for simulation may be 140μm, 180μm & 240μm irrespective of each beam. (Refer Fig.2)
Accordingly, with the variation in the length of the floating metal, the resonant frequency is shifting, (Exemplary, the f0 changes a range from 8.223GHz to 7.226GHz respectively for different lengths of floating metal aforementioned)
Claimed invention can be for multi- frequency applications with single set of beams. (wherein the beam is among said plurality of beam either in down state and as well as up-state.)
The isolation at resonance is >30dB in magnitude which is appreciable for claimed RF MEMS capacitive switch.
The insertion loss is <1dB in magnitude until 25GHz for which said MF switch is configured. (Refer Fig)

Industry Perspective:

Claimed invention is advantageous for multi-frequency applications with single set of beams.
Further claimed system can be used in coplanar waveguide (CPW) signal transmission & in CPW to toggle the state of a transmission line.
Moreover, facilitates efficient solutions in cost-effective manner.

Prof. Amitava Das Gupta

Prof. Deleep R Nair

Department of Electrical Engineering

TRL-4

Proof of Concept ready, tested in lab.

Technology Transfer