RF MEMS  The solution to power hungry smart phones

What are MEMS? Micro(small) Electro(electric components/functionality) Mechanical(mechanical components/functionality) Systems(integrated, system-like functionality) http://eed.gsfc.nasa.gov/562/SA_MEMs.htm http://www.memx.com/ http://www.memx.com/ http://www.forbes.com/2008/04/22/mems-apple-nintendo_leadership_clayton_in_jw_0421claytonchristensen_inl_slide.html

Where do you find MEMs? Printers Projectors Cell Phones *High DPI inkjets Projectors *Micro-Mirrors from Texas Instruments Cell Phones *Knowles Microphones used in most new cell phones Automobiles

LIMITATIONS OF EXISTING :  Photovoltaic cells and wind power harvesting have several technical barriers.  In solar cells, the inherent physical limits, the black body energy conversion loss, optical loss, and internal resistance prevent their efficiency from reaching >20%

Why MEMS…? Low cost, High yield Small *Typically .1-100um feature size http://singularityhub.com/wp-content/uploads/2008/08/red-blood-cells.bmp Red Blood Cells ~ 10um Human Hair thickness ~ 50um http://www.vendian.org/envelope/dir2/scaling_construct.html Low cost, High yield *Use existing IC fabrication technology *Made primarily on Silicon Wafers

Why MEMS…? Favorable scaling for a lot of applications *Flow-rate sensors *Electrostatics *Magnetism *Many others Not all applications *Solar Power *Turbulent Boundary Energy Harvesting

Where it Began…? 1979 - First recorded use of MEMs in automobiles Federal emission standards required monitoring the air-to-fuel ratio of the engine Density of air value was needed Many different sensor technologies were introduced to solve this problem MAP (manifold absolute pressure) and MAT (manifold air temperature) sensors were developed using MEMS Silicon based MEMS sensors became the device of choice due to low cost and high yield MAP Sensor

Who Developed It…? *Delco Electronics Group(General Motors) Two groups *Delco Electronics Group(General Motors) *Used piezo resistive sensing Ford *Used capacitive sensing

Typical Applications * Accelerometers * Microphones * RF-MEMS Switches * Bridge to Nanotechnology * Mobile Communications

RF-MEMS Switches Types :- * Capacitive shunt switch: 1.OFF state with capacitive coupling 2.Isolation dependent on capacitive ratio between ON and OFF state 3.Longer contact lifetime

Direct Contact Series Switch: 1 * Direct Contact Series Switch: 1.ON state with metal-to-metal ohmic contact 2. Insertion loss dependent on the contact resistance 3. Broad frequency coverage

Mobile Communications Fully Integrated Tunable RF * If you put your finger on an RF MEMS antenna it can automatically re-tune itself so that no calls are dropped. *Furthermore, RF MEMS can react to atmospheric conditions and re-tune your phone’s radio to improve 3G and LTE data throughout. * Most importantly, though, RF MEMS paves the way towards devices with just a single antenna and transceiver.

Number of radios in smart phones: *GSM *3G *CDMA, W-CDMA *Bluetooth, Wi-Fi

SPECIFICATIONS * New approach to ohmic switching. * It can be integrated with capacitors using wafer- level thin-film packaging. * Multiband (800-to-2200-MHz), low-loss (0.3-dB) chips measure just 3.5 x 4.2 x 1.1 mm.

STATISTICS….

Advantages & Limitations : Advantages : *cost  about 2 to 2.5 cents/switch throw—in SPST and SPDT configurations *High precision, High reliability, Linearity *Simplicity of principle *Compatible with conventional IC’s *Low weight *60% reduction in board space. Limitations: *Slower switching speed *Potential lifetime limitations *Packaging

CONCLUSION  MEMS technology provides powerful tools to the RF technology. Replace conventional solid state circuit devices on size.  Overall MEMS field is not much more than 10 years old, and the RF MEMS field has really been shaped within the past 5-6 years. The future should be bright and unlimited

By Sai Chand Surya

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