Back in the old days, the really good radios used mechanical filters. Now, according to this item, we could see a whole new type of mechanical filter, this time built with a microelectromechanical (MEMS) device.
Tiny ‘MEMS’ Devices to Filter, Amplify Electronic Signals
Purdue University News (08/10/09) Venere, Emil
Purdue University researchers are developing a new class of microelectromechanical (MEMS) devices called resonators that contain vibrating, hair-thin structures and could be used to filter electronic signals. Resonators vibrate in specific patterns, so they can cancel out signals that contain certain frequencies while allowing others to pass, making these devices useful for applications such as refining cell phone signals. The devices have led to a new type of band-pass filter, which is used in electronics to allow some signals to pass while blocking others, says Purdue professor Jeffrey Rhoads. This new class of resonators represents a potential way to further the miniaturization of band-pass filters while improving their performance and power efficiency. Incoming signals generate voltage that creates an electrostatic force, causing the MEMS filters to vibrate. In addition to their potential use as cell phone filters, resonators also could be used for advanced chemical and biological sensors for medical and homeland security applications, and possibly as a new type of mechanical memory element that uses vibration patterns to store data. “The potential computer-memory application is the most long term and challenging,” Rhoads says. He says the band-pass filter design promises to create better performance than previous MEMS technology because it more strictly defines which frequencies can pass and which are blocked.