This paper presents a dual-microelectromechanical system (MEMS) resonator-based temperature sensor. In this sensor, the readout circuit estimates the temperature by measuring the frequency ratio of the two clocks generated by separate resonators with different temperature coefficients. The circuit is realized in a 0.18-μm CMOS process and achieves a resolution of 20 μK over a bandwidth of 100 Hz while consuming 19 mW of power, leading to a resolution FOM of 0.04 pJK 2 . It enables us to implement a MEMS-based programmable oscillator with an Allan deviation of <;1e -10 over 1 s averaging time, and a frequency stability of <;±0.1 parts per million in the temperature range from -45 °C to 105 °C. Such oscillators are key building blocks in telecom, datacom, and precision timekeeping applications.

Oscillators are key components in automotive electronics systems. For example, a typical automotive camera module may have three or more oscillators, providing the clocks for microcontrollers, Ethernet controllers, and video chipsets. These oscillators have historically been built around a quartz crystal resonator connected to an analog sustaining circuit driving the crystal to vibrate at its resonant frequency. However, quartz-based devices suffer from poor performance and reliability in harsh automotive environments. SiTime has developed timing solutions based on silicon micro-electromechanical systems (MEMS) technology that exhibit better electromagnetic noise rejection and better performance under shock and vibration. In this paper, we first discuss the design and manufacturing of the MEMS-based device, with emphasis on the specific design aspects that improve reliability and resilience in harsh automotive environments. These aspects include the SOI-based MEMS fabrication process, the oscillator and state-of-the-art temperature compensation architecture, and the manufacturing and packaging process. We then describe the test methods used to evaluate the resilience of the device, including electromagnetic susceptibility ( EMS), and performance during shock and vibration. The results show that the MEMS-based oscillator performs better than all quartz oscillators that were tested, with up to 50x better EMS, up to 24x better performance during shock, and up to 100x and 20x better performance during sinusoidal and random vibration, respectively.

Real-time clocking for space-constrained mobile and wearable applications require low-power 32.768 kHz references with small form-factor and tight frequency stability, at a competitive price built in an ultra-high volume capable manufacturing process. Legacy 32 kHz quartz-based technology has reached the limits of miniaturization, performance and cost. In this work, a temperature compensated 32 kHz MEMS-based oscillator (TCXO), in a 1.55 mm × 0.85 mm × 0.55 mm form factor, with ±5 ppm frequency stability over -40°C to 85°C, will be presented. The combination of wafer-level chip scale packaging (WL-CSP) and silicon MEMS technology has enabled the smallest and best-in-class 32 kHz clocking solution for very high volume applications. The underlying MEMS system packaging and test technologies will be presented along with the electrical and reliability results.

MEMS-based oscillators offer a silicon-based alternative to quartz-based frequency references. Here, a MEMS-based programmable oscillator is presented which achieves better than ±0.5-ppm frequency stability from -40 ° C to 85 ° C and less than 1-ps (rms) integrated phase noise (12 kHz to 20 MHz). A key component of this system is a thermistor-based temperature-to-digital converter (TDC) which enables accurate and low noise compensation of temperature-induced variation of the MEMS resonant frequency. The TDC utilizes several circuit techniques including a high-resolution tunable reference resistor based on a switched-capacitor network and fractional-N frequency division, a switched resistor measurement approach which allows a pulsed bias technique for reduced noise, and a VCO-based quantizer for digitization of the temperature signal. The TDC achieves 0.1-mK (rms) resolution within a 5-Hz bandwidth while consuming only 3.97 mA for all analog and digital circuits at 3.3-V supply in 180-nm CMOS.

An integrated MEMS thermistor and resonator are at the core of SiTime's new high performance oscillator platform.These MEMS-based oscillators are designed to achieve the performance requirements of high-end communication applications.The resonator, which has an f-Q product of 6.9×10 12 , enables the oscillator to achieve sub-picosecond integrated phase jitter in the 12 kHz to 20 MHz frequency range.The MEMS thermistor, with a resistance-temperature sensitivity of 0.33 %/C, is used to compensate for the temperature-induced frequency variations of the silicon resonator.The thermistor is key to achieving sub-ppm frequency stability in a -40 C to 85 C temperature range and a sub-5 ppb Allan deviation in 0.1 second to 10 second strides.The demonstrated system performance opens high-volume data communication markets previously unavailable to MEMS-based oscillators.

Polysiloxane and conductive polymers were integrated onto a side-polished optical fiber to implement a variable optical attenuator. A conductive polymer thermo-optically altered the refractive index of an elastomer placed in close proximity to a fiber core.

A method is presented that incorporates thin, lossy layers into a finite-difference frequency-domain algorithm designed for structures with circular geometry. The method allows the grid spacing to be much larger than the thickness of the thin layers. This greatly reduces the computational effort required when simulating circular structures such as optical fibers that incorporate thin layers. The method is validated by a comparison with the analytical solutions. (c) 2006 Wiley Periodicals, Inc.

One of the most widely utilized absorbing boundaries for the finite difference frequency domain (FDFD) method is the perfectly matched layer (PML); however, this boundary is not ideal, as it significantly increases the computational complexity of a simulation. We compare three alternatives to the PML for modal solution using the FDFD method: the Higdon absorbing boundary condition, the complementary operators method, and the transparent absorbing boundary. These methods are integrated into an FDFD algorithm and applied to a well-known ridge waveguide test structure. The errors introduced by the absorbing boundaries are quantified in terms of propagation constant error and modal distortion, and compared to reported results using the PML.

A method is presented to incorporate thin, lossy layers into a finite‐difference frequency‐domain model while retaining a coarse grid‐spacing. This approach significantly reduces computational effort. The new method is validated by a comparison with analytical solutions. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 40–44, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20369

Electrooptic modulators that consist of an optical fiber waveguide coupled to an electrooptic waveguide are reviewed. Desirable attributes of these devices are that the optical fiber is uninterrupted and the interaction with the electrooptic region occurs only where the optical properties are modulated. In this paper we review in-line fiber evanescent field modulators that we have implemented with electrooptic polymers and compound semiconductor quantum wells. We show that the beam propagation method can accurately simulate the behavior measured in these devices.

In this paper we describe a novel switch architecture for single-mode optical fibers based on micromirror arrays. This architecture allows scaling to a large number of fiber ports and can be integrated directly with free-space wavelength multiplexers (gratings). Using tilt-up surface micromachined polysilicon micromirrors, a W switch configuration was demonstrated. The measured insertion loss was -4.2 dB and the cross-talk was -50 dB. The mirrors used in the switch design have a maximum optical deflection of 24 degrees and a resonant frequency of 1.9 kHz, leading to a switching time (including settling) of 2 ms. The micromirrors have sufficient resolution to support scaling to 19 channels while maintaining the same low cross-talk.