Seungbae Lee

A 10-MHz Micromechanical Resonator Pierce Reference Oscillator for Communications

A modified Pierce circuit topology has been used to first demonstrate a 9.75 MHz μmechanical resonator reference oscillator, then to assess the ultimate frequency stability of such an oscillator via accurate measurement of its close-to-carrier phase noise, which seems to exhibit an unexpected 1/f 3 dependence that limits the phase noise to −80 dBc at a 1 kHz offset from the carrier—a value that must be improved before use in most communications applications. Through theoretical analysis, this 1/f 3 dependence seems to derive from aliasing of active circuit 1/f noise onto the carrier caused by nonlinearity in the capacitive transducer of the μmechanical resonator.

60-MHz wine-glass micromechanical-disk reference oscillator

A reference oscillator utilizing a 60MHz, MEMS-based, wine glass disk vibrating micromechanical resonator with a Q of 48,000 and sufficient power handling capability to achieve a far-from-carrier phase noise of -130dBc/Hz is demonstrated. When divided down to 10MHz, this corresponds to an effective level of -145dBc/Hz.

Mechanically-coupled micromechanical resonator arrays for improved phase noise

Reductions in phase noise by more than 26 dB have been obtained over previous micromechanical resonator oscillators by replacing the single resonator normally used in such oscillators with a mechanically coupled array of them to effectively raise the power handling ability of the frequency selective tank by a factor equal to the number of resonators used in the array, and all with virtually no increase in volume or cost, given that all resonators are integrated onto a single die using batch processed MEMS technology. Specifically, a mechanically coupled array of ten 15.4-MHz 40/spl mu/m/spl times/10/spl mu/m/spl times/2/spl mu/m free-free beams embedded in a positive feedback loop with a single-ended to differential transimpedance sustaining amplifier achieves phase noise of -109 and -133 dBc/Hz at 1 kHz and far-from-carrier offset frequencies, respectively. When divided down to 10 MHz, these effectively correspond to -112 and -136 dBc/Hz, respectively, which represent more than 17 and 26 dB improvements over recently published work with clamped-clamped beam resonator oscillators.

Series-resonant micromechanical resonator oscillator

A 10-MHz series resonant micromechanical resonator oscillator has been demonstrated using a custom-designed, single-stage, zero-phase-shift sustaining amplifier together with a clamped-clamped beam micromechanical resonator, designed with a relatively large width of 40 /spl mu/m to achieve substantially lower series motional resistance R/sub x/ and higher power handling than previous such devices. Using automatic level control (ALC) circuitry to remove an unexpected 1/f/sup 3/ close-to-carrier phase noise component, this oscillator achieves a phase noise density of -95 dBc/Hz at 1 kHz offset from the carrier, while consuming only 820 /spl mu/W of power.

Two-dimensional position deteciton system with MEMS accelerometer for MOUSE applications

A hybrid two-dimensional position sensing system is designed for mouse applications. The system measures the acceleration of hand-movements which are converted into two-dimensional location coor-dinates. The system consists of four major components: 1) MEMS accelerometers, 2) CMOS analog read-out circuitry, 3) an accelera-tion magnitude extraction module, and 4) a 16-bit RISC micropro-cessor. Mechanical and analog circuit simulation shows that the designed padless mouse system can detect accelerations as small as 5.3 mg and operate up to 18MHz.

MEMS vibrating structure using a single-crystal piezoelectric thin film layer

The present invention relates to a micro-electro-mechanical systems (MEMS) vibrating structure having dominant lateral vibrations supported by a MEMS anchor system, and includes a single-crystal piezoelectric thin-film layer that has been grown with a specific crystal orientation. Since the MEMS vibrating structure has dominant lateral vibrations, its resonant frequency may be controlled by its size and shape, rather than layer thickness, which provides high accuracy and enables multiple resonators having different resonant frequencies on a single substrate.

Two-dimensional position detection system with MEMS accelerometers, readout circuitry, and microprocessor for padless mouse applications

A hybrid two-dimensional position sensing system is designed with microelectromechanical systems (MEMS) for padless mouse applications. The X/Y-axis acceleration of the users hand movements is measured by two MEMS accelerometer devices. These acceleration values are pulsewidth modulated and converted into (X, Y) coordinates on the screen by integral operations on a microprocessor. The overall system consists of four major components: 1) MEMS accelerometers; 2) CMOS analog readout circuitry; 3) an acceleration magnitude extraction module; and 4) a 16-b RISC microprocessor. Mechanical and analog simulation shows that the designed mouse system can detect acceleration as small as 5.3 mg (g=9.8 m/s/sup 2/) with 100-kHz sampling frequency for low power consumption.