Thura Lin Naing

A 1-GS/s 6-bit 6.7-mW ADC in 65-nm CMOS

An asynchronous 6bit 1GS/s ADC is achieved by time interleaving two ADCs based on binary successive approximation algorithm (SA) using a capacitive ladder. The semi-close loop asynchronous technique eliminates the high internal clocks and significantly speeds up the SA algorithm. One bit redundancy is implemented to compensate the process variation of parasitic and the MOM capacitance. Fabricated in 65nm CMOS with an active area of 0.11mm2, it achieves a peak SNDR of 31.5dB at 1 GS/s sampling rate and has a power consumption of 6.7mW for the analog and digital processing.

A 78-microwatt GSM phase noise-compliant pierce oscillator referenced to a 61-MHz wine-glass disk resonator

A 61-MHz Pierce oscillator referenced to a single polysilicon surface-micromachined wine-glass disk resonator has achieved phase noise marks of -119dBc/Hz at a 1-kHz offset and -139dBc/Hz at far-from-carrier offsets. When divided down to GSMs 13MHz, this corresponds to -132dBc/Hz at 1-kHz and -152dBc/Hz at far-from-carrier offsets, both of which satisfy GSM reference oscillator phase noise requirements. This Pierce oscillator achieves such performance using a single disk, not an array, while only consuming 78 microwatts of power, a reduction by a factor of ~4.5 compared with previous work. When power consumption is considered, this performance marks the best figure of merit at 1-kHz carrier offset among published on-chip oscillators to date. Such low phase noise and power consumption posted by a tiny MEMS device may soon become key enablers for low power “set-and-forget” autonomous sensor networks with substantial communication capability.

2.97-GHz CVD diamond ring resonator with Q >40,000

A capacitive-gap transduced micromechanical ring resonator based on a radial contour vibration mode and constructed from hot filament CVD boron-doped microcrystalline diamond has achieved a Q of 42,900 at 2.9685GHz that represents the highest series-resonant Q yet measured at this frequency for any on-chip room temperature resonator, as well as the highest f·Q of 1.27×1014 for acoustic resonators, besting even macroscopic bulk-mode devices. Values like these in a device occupying only 870μm2 may soon make possible on-chip realizations of RF channelizers and ultra-low phase-noise GHz oscillators for secure communications.

Acoustic whispering gallery mode resonator with Q > 109,000 at 515MHz

A capacitive-gap transduced micromechanical resonator design based on an acoustic whispering gallery mode (WGM) constructed in micro-crystalline diamond has achieved a Q >;109,000 at 515MHz, posting an f·Q product of >;5.6×1013. The key to this performance is anchor-loss nulling by the WGM, as evidenced by comparison of Q values between radial-contour modes and WGM ones on the same disk device, where a 2-3× enhancement of Q is observed. Qs exceeding 100,000 should enable unprecedented RF front-end frequency selectivity and low phase noise oscillators for future communications.

A real-time 32.768-kHz clock oscillator using a 0.0154-mm 2 micromechanical resonator frequency-setting element

A capacitive-comb transduced micromechanical resonator using aggressive lithography to occupy only 0.0154-mm2 of die area has been combined via bond-wiring with a custom ASIC sustaining amplifier and a supply voltage of only 1.65V to realize a 32.768-kHz real-time clock oscillator more than 100× smaller by area than miniaturized quartz crystal implementations and at least 4× smaller than other MEMS-based approaches, including those using piezoelectric material. The key to achieving such large reductions in size is the enormous rate at which scaling improves the performance of capacitive-comb transduced folded-beam micromechanical resonators, for which scaling of lateral dimensions by a factor S provides an S2× reduction in both motional resistance and footprint for a given resonance frequency. This is a very strong dependency that raises eyebrows, since the size of the frequency-setting tank element may soon become the most important attribute governing cost in a potential MEMS-based or otherwise batch-fabricated 32.768-kHz timing oscillator market. In addition, unlike quartz counterparts, the size reduction demonstrated here actually reduces power consumption, allowing this oscillator to operate with only 2.1μW of DC power.

Long-term stability of a hermetically packaged MEMS disk oscillator

A low phase noise oscillator referenced to a wineglass disk MEMS resonator, hermetically vacuum packaged in a purpose-built packaging system, and measured in a double-oven, has provided a first long-term measurement of a MEMS disk oscillator over 10 months. After an initial burn-in period, the frequency can be seen to stabilize to within the short-term measurement variation of 300 ppb over a period of months, a significant improvement from previous studies on other MEMS resonator types, where frequency fluctuations were between 3.1 ppm and 1.2 ppm over similar time scales. Including burn-in, the total observed aging of 10 ppm is now on par with many consumer-grade quartz oscillators designed for timing applications and sufficient for target wireless sensor network applications.

Vibration-insensitive 61-MHz micromechanical disk reference oscillator

A low phase noise oscillator referenced to a 61-MHz vibrating wine-glass disk resonator with anchor-isolating supports designed to suppress microphonics has posted (without any compensation) a measured acceleration sensitivity at least as good as Γ ~0.2ppb/g for vibration frequencies up to 2kHz and in all directions, yielding a vector magnitude Γ less than 0.5ppb/g. Remarkably, this result is at least 30 times better than previous work using a similar wine-glass disk resonator and is the best mark among MEMS-based oscillators to date, including those aided by feedback compensation circuits. It is also more than an order of magnitude better than an off-the-shelf crystal oscillator and is now comparable with low sensitivity oven-controlled crystal oscillators (OCXOs). Such low sensitivity to environmental vibration by a tiny uncompensated MEMS-based oscillator is expected to enable harsh environment and military applications that require stable and compact reference oscillators.

High-

A vibrating micromechanical spoke-supported ring resonator employing a central peg-anchor, balanced non-intrusive quarter-wavelength extensional support beams, and notched support attachments attains high

Q

Q

UHF Spoke-Supported Ring Resonators

-factor in vacuum, posting 10 000 at 441 MHz when made of polysilicon structural material and 42 900 at 2.97 GHz when made of microcrystalline diamond. The latter marks the highest