MEMS cantilever beam and electrostic actuation

One of the very basic MEMS structures is the cantilever beam. This structure can be used in a variety of applications including RF switching, varactors, switches, capacitors, springs etc. Among the many ways to actuate the operation of a cantilever is electrostatics. In this case a voltage is applied across the movable arm of the beam and a baseplate or reference terminal that resides directly below the beam. To bend the beam and to make contact with the baseplate a pull in voltage is necessary. Once the applied voltage reaches the pull in voltage the beam bends and makes contact with the base plate. When the pull in voltage is removed the spring force of the beam restores it to its original state, as long the elastic limits of the beam are not exceeded. A brief whitepaper on this operation is available to interested parties in the engineering pages of Signal Processing Group Inc's website located at http://www.signalpro.biz.

A simple planar inductor

In Integrated Circuit design and MMIC design, integrated planar inductors are used frequently. These inductors have typically lower quality factors. However, in a variety of applications planar inductors can be used effectively. The simplest planar inductor is a length of high characteristic impedance microstrip line. A brief paper published by Signal Processing Group Inc.,provides design equations for this type of structure. Interested readers can view the paper at SPG's website, http://www.signalpro.biz on the engineering pages web page.

MEMS design tools

Its interesting how the MEMS design development is paralleling the IC design methodology of yesteryear. The process appears to be very similar,only the parameters seem to change. We also see UC Berkeley developing methodology and CAD tools. MIT is also an early entrant into the CAD Tool fray. Commercially available tools from Coventor are available ( for a significant cost) but may be the best deal for the design engineer interested in end results rather than the process. It remains to be seen how this whole industry pans out. However, already there are large numbers of MEMS devices working in commercial systems so the MEMS approach is beginning to make sense. Contact SPG at http://www.signalpro.biz for our experince with MEMS related issues.