Frequency Tunable MEMS-Based Timing Oscillators and Narrowband Filters - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Frequency Tunable MEMS-Based Timing Oscillators and Narrowband Filters write by Henry Galahad Barrow. This book was released on 2015. Frequency Tunable MEMS-Based Timing Oscillators and Narrowband Filters available in PDF, EPUB and Kindle. There is little question that the commercial success of smartphones has substantially increased the volume of products utilizing Micro Electro Mechanical Systems (MEMS) technology, especially accelerometers, gyroscopes, bandpass filters, and microphones. The Internet of Things (IoT), a more recent driver for small, low power microsystems, seems poised to provide an even bigger market for these and other potential products based on MEMS. Given that the IoT will likely depend heavily on massive sensor networks using nodes for which battery replacement might not be practical, cost and power consumption become even more important. As already known for existing sensor networks, sleep/wake cycles will likely be instrumental to maintaining low sensor node power consumption in the IoT, and if so, then the clocks that must continuously run to synchronize sleep/wake events often become the bottlenecks to ultimate power consumption. On the communications side, narrowband RF channel-selecting front-end filters stand to greatly reduce receive power consumption by relaxing transistor circuit dynamic ranges. Both the accuracy of the clocks and ability of filters to achieve bandwidths small enough to select individual channels depend heavily on the accuracy and precision to which the frequency-setting devices they rely on are constructed. Inevitably, fabrication tolerances are finite, which means the ability to attain the highest performance relies on trimming or tuning. This dissertation focuses on methods by which voltage-controlled frequency tuning of capacitively-transduced micromechanical resonators make possible 1) an ultra-compact, low-power 32.768-kHz micromechanical clock oscillator; and 2) a high-order, small percent bandwidth coupled-resonator filter with minimal passband distortion. Currently, quartz crystal-based oscillators at 32.768 kHz dominate the market because they offer the best combination of cost and performance. However, the physical dimensions of these oscillators are presently too large for future small form-factor electronic applications, such as ones that fit within credit cards. While there have been attempts to shrink quartz resonating elements, the increasingly difficult fabrication steps required to produce such devices raises manufacturing costs, thereby preventing widespread adoption (so far). In addition, quartz crystal motional resistance values typically increase as resonator dimensions shrink, which in many oscillator configurations raises power consumption. Unlike common quartz resonators, properly designed MEMS resonators benefit greatly from scaling in that reductions in lateral dimensions lead to a rapid decrease in motional resistance by a square law. The work described herein harnesses these scaling advantages to realize an oscillator much smaller than quartz-based oscillators with potential for much less power consumption. Specifically, this work uses aggressive lithography to achieve a capacitive-comb transduced micromechanical resonator occupying only 0.0154 mm2 of die area. Wire bonding this resonator to a custom sustaining amplifier and a supply voltage of only 1.65V then realizes 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. The use of voltage-controlled tuning Oscillations sustains with only 2.1 [mu]W of power consumption. On the filter front, whether realized using quartz, FBAR, or capacitive-gap transduced MEMS resonator, mechanical filter responses are only as flat as the accuracy of their constituent resonator center frequencies. While narrowband micromechanical filters comprised of up to three mechanically coupled resonators have been demonstrated in the past, there exists a demand for bandpass filters with even sharper roll-offs and larger stopband rejections, and this requires higher order filters utilizing more than three coupled resonators. The work herein demonstrates filters comprised of four coupled resonators with bandwidths narrow enough to select individual channels. Before correction, filter passbands fresh out of the fab look nothing like their intended responses. Application of the automated passband correction protocol of this work, based on voltage-controlled frequency tuning, permits measurement of a 4-resonator micromechanical filter with a 0.1% bandwidth commensurate with the needs of channel-selection (albeit at a low frequency) and an impressive 20-dB shape factor of 1.59, all with less than 3dB of additional passband ripple (beyond the design ripple).
MEMS-based Phase-locked-loop Clock Conditioner
MEMS-based Phase-locked-loop Clock Conditioner - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook MEMS-based Phase-locked-loop Clock Conditioner write by Mauricio Pardo Gonzalez. This book was released on 2012. MEMS-based Phase-locked-loop Clock Conditioner available in PDF, EPUB and Kindle. Ultra narrow-band filters and the use of two loops in a cascade configuration dominate current clock conditioners based on phase-locked-loop (PLL) schemes. Since a PLL exhibits a low-pass transfer function with respect to the reference clock, the noise performance at very close-to-carrier offset frequencies is still determined by the input signal. Although better cleaning can be achieved with extremely narrow loops, an ultra low cut-off frequency could not be selected since the stability of the configuration deteriorates as the filter bandwidth is reduced. This fact suggests that a full-spectrum clock conditioning is not possible using traditional PLL architectures, and an alternative scheme is necessary to attenuate the very-close-to-carrier phase noise (PN). In addition, ultra-narrow loop filters can compromise on-chip integration because of the large size capacitors needed when chosen as passive. Input signal attenuation with relaxed bandwidth requirements becomes the main aspect that a comprehensive clock cleaner must address to effectively regenerate a reference signal. This dissertation describes the Band-Reject Nested-PLL (BRN-PLL) scheme, a modified PLL-based architecture that provides an effective signal cleaning procedure by introducing a notch in the input transfer function through inner and outer loops and a high-pass filter (HPF). This modified response attenuates the reference-signal PN and reduces the size of the loop-filter capacitors substantially. Ultra narrow loops are no longer required because the notch size is related to the system bandwidth. The associated transfer function for the constitutive blocks (phase detectors and local oscillators) show that the output close-to-carrier and far-from-carrier PN sections are mainly dominated by the noise from the inner-PLL phase detector (PD) and local oscillator (LO) located in the outer loop, respectively. The inner-PLL PD transfer function maintains a low-pass characteristic with a passband gain inversely proportional to the PD gain becoming the main contribution around the carrier signal. On the other hand, the PN around the transition frequency is determined mainly by the reference and the inner-PLL LO. Their noise contributions to the output will depend on the associated passband local maxima, which is located at the BRN-PLL transition frequency. Hence, in this region, the inner-PLL LO is selected so that its effect can be held below that of the outer-PLL PD. The BRN-PLL can use a high-Q MEMS-based VCO to further improve the transition region of the output PN profile and an LC-VCO as outer-PLL LO to reduce the noise floor of the output signal. In particular, two tuning mechanisms are explored for the MEMS-VCO: series tuning using varactors and phase shifting of a resonator operating in nonlinear regime. Both schemes are implemented to generate a tunable oscillator with no PN-performance degradation.
Frequency Stability of MEMS Timing References with Nonlinearities
Frequency Stability of MEMS Timing References with Nonlinearities - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Frequency Stability of MEMS Timing References with Nonlinearities write by Hyung Kyu Lee. This book was released on 2011. Frequency Stability of MEMS Timing References with Nonlinearities available in PDF, EPUB and Kindle. The increasing demand for miniaturized electronic devices has heightened the need for tiny oscillators suitable to provide an accurate reference signal to electronics. In this sense, MEMS (microelectromechanical systems) resonator and oscillator have drawn a great deal of attention because they can be integrated onto silicon chips in a small form factor. This work describes the design, theory, and demonstration of MEMS resonator and oscillator with improved mid-term and short-term stability, especially when a resonator has nonlinearities. In the temperature stability study, electrostatic tuning was applied to Si-SiO2 composite resonators, which were made of single- crystal silicon with a silicon dioxide coating. The hybrid of these two temperature compensation methods achieved less than ± 2.5 parts per million frequency variation over a 90°C-wide temperature range, which is comparable with commercial quartz oscillators. In addition, the effect of nonlinearities of resonators on temperature sta- bility was analyzed: the temperature-dependent nonlinear effect model was theorized and verified with single-crystal silicon and Si-SiO2 composite resonator-based oscil- lators; a new feedback circuit architecture that improves temperature stability was then developed based on the model. In the phase-noise performance study, oscillator stability far above the critical vibration amplitude in the nonlinear regime was first demonstrated by using a novel variable-phase closed-loop setup. After that, more than twentyfold improvement in the power-handling and far-from-carrier phase-noise performances were achieved by operating an oscillator in the nonlinear regime. In addition, the nonlinear phase-noise model was verified by using the same closed-loop setup. In conjunction with the recently developed nonlinear motional impedance model, this phase-noise model enables further improvement in the phase-noise per- formance of MEMS resonator-based oscillators.
RF and Microwave Applications and Systems
RF and Microwave Applications and Systems - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook RF and Microwave Applications and Systems write by Mike Golio. This book was released on 2018-10-03. RF and Microwave Applications and Systems available in PDF, EPUB and Kindle. This volume, RF and Microwave Applications and Systems, includes a wide range of articles that discuss RF and microwave systems used for communication and radar and heating applications. Commercial, avionics, medical, and military applications are addressed. An overview of commercial communications systems is provided. Past, current, and emerging cellular systems, navigation systems, and satellite-based systems are discussed. Specific voice and data commercial systems are investigated more thoroughly in individual chapters that follow. Detailed discussions of military electronics, avionics, and radar (both military and automotive) are provided in separate chapters. A chapter focusing on FR/microwave energy used for therapeutic medicine is also provided. Systems considerations including thermal, mechanical, reliability, power management, and safety are discussed in separate chapters. Engineering processes are also explored in articles about corporate initiatives, cost modeling, and design reviews. The book closes with a discussion of the underlying physics of electromagnetic propagation and interference. In addition to new chapters on WiMAX and broadband cable, nearly every existing chapter features extensive updates and several were completely rewritten to reflect the massive changes areas such as radio navigation and electronic warfare.
The Engineering Handbook
The Engineering Handbook - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook The Engineering Handbook write by Richard C. Dorf. This book was released on 2018-10-03. The Engineering Handbook available in PDF, EPUB and Kindle. First published in 1995, The Engineering Handbook quickly became the definitive engineering reference. Although it remains a bestseller, the many advances realized in traditional engineering fields along with the emergence and rapid growth of fields such as biomedical engineering, computer engineering, and nanotechnology mean that the time has come to bring this standard-setting reference up to date. New in the Second Edition 19 completely new chapters addressing important topics in bioinstrumentation, control systems, nanotechnology, image and signal processing, electronics, environmental systems, structural systems 131 chapters fully revised and updated Expanded lists of engineering associations and societies The Engineering Handbook, Second Edition is designed to enlighten experts in areas outside their own specialties, to refresh the knowledge of mature practitioners, and to educate engineering novices. Whether you work in industry, government, or academia, this is simply the best, most useful engineering reference you can have in your personal, office, or institutional library.
