Stable local oscillators with low phase noise are extremely important elements in high performance military
communication and navigation systems. We present the development of compact UHF-band frequency sources capable
of maintaining low phase noise under high accelerations or vibrations and over a wide temperature range for handheld
portable systems. We also explored nonlinearity in MEMS resonators and attempted to use nonlinear dynamics to
enhance phase noise performance. Using the quartz MEMS technology, we have thus far demonstrated a 645 MHz
Pierce oscillator with -113 dBc/Hz phase noise at 1 kHz offset with acceleration sensitivity of 5x10-10/g. The controlled
oscillation of a nonlinear Duffing resonator in a closed-loop system with improved phase noise is described.
We have developed high dynamic range (105-106 g's) tunneling accelerometers1,2 that may be ideal for smart munitions applications by employing both surface and bulk micromachining processing techniques. The highly miniaturized surface-micromachined devices can be manufactured at very low cost and integrated on chip with the control electronics. Bulk-micromachined devices with Si as the cantilever material should have reduced long-term bias drift as well as better stability at higher temperatures. Fully integrated sensors may provide advantages in minimizing microphonics for high-g applications. Previously, we described initial test results using electrostatic forces generated by a self-test electrode located under a Au cantilever3. In this paper, we describe more recent testing of Ni and Au cantilever devices on a shaker table using a novel, low input voltage (5 V) servo controller on both printed wiring board and surface-mount control circuitry. In addition, we report our initial test results for devices packaged using a low-temperature wafer-level vacuum packaging technique for low-cost manufacturing.
Hughes Electronics has developed a novel surface micromachining process for fabricating extremely low cost integrated tunneling sensors for a wide variety of military and commercial applications. Previously fabricated bulk micromachined tunneling devices have demonstrated the high displacement sensitivity (approximately 4.0 X 10-5 nm/(root)Hz at 500 Hz) obtainable with tunneling transduction. However, these early devices were fabricated with processes that yielded fairly large multi- wafer sensors which are difficult to integrate with the control electronics and package, thus limiting commercial development. This paper describes our surface micromachining techniques, their compatibility with large volume production, accelerometer device performance, and the system applications for this new technology.