Octave-tunable miniature RF resonators

The development and testing of a miniaturized, high-Q, broadly tunable resonator is described. An exemplary device, with a center frequency that is continuously tunable from 1.2 to 2.6 GHz, was tested in detail. Experimental results demonstrated a resonator Q of up to 380, and typical insertion loss of -1.9 dB for a 25 MHz 3-dB bandwidth. These resonators have been used to stabilize a broadly-tunable oscillator with phase noise of -132 dBc/Hz at 100-kHz offset, with a center frequency tunable from 1.2-2.6 GHz, and a tuning speed of 1 GHz/ms

A sigma-delta interface built-in self-test and calibration for microelectromechanical system accelerometer's utilizing interpolation method

This work presents the capacitive micromechanical accelerometer with a completely differential high-order switched capacitor sigma-delta modulator interface. Such modulation interface circuit generates one-bit output data using a third sigma-delta modulator low-noise front-end, doing away with the requirement for a second enhanced converter of resolution to encode the feedback route analog signal. A capacitive micromechanical sensor unit with just a greater quality factor has been specifically employed to give greater resolution. The closed-loop and electrical correction control are used to dampen the high-Q values to get the system's stability with high-order. This microelectromechanical system (MEMS) capacitive accelerometer was calibrated using a lookup table and Akima interpolation to find manufacturing flaws by recalculating voltage levels for the test electrodes. To determine the proper electrode voltages for fault compensation, COMSOL software simulates a number of defects upon that spring as well as the fingers of the sensor system. When it comes time for the feedback phase of a proof mass displacement correction, these values are subsequently placed in the lookup table

A Capacitance-To-Digital Converter for MEMS Sensors for Smart Applications

The use of MEMS sensors has been increasing in recent years. To cover all the applications, many different readout circuits are needed. To reduce the cost and time to market, a generic capacitance-to-digital converter (CDC) seems to be the logical next step. This work presents a configurable CDC designed for capacitive MEMS sensors. The sensor is built with a bridge of MEMS, where some of them function with pressure. Then, the capacitive to digital conversion is realized using two steps. First, a switched-capacitor (SC) preamplifier is used to make the capacitive to voltage (C-V) conversion. Second, a self-oscillated noise-shaping integrating dual-slope (DS) converter is used to digitize this magnitude. The proposed converter uses time instead of amplitude resolution to generate a multibit digital output stream. In addition it performs noise shaping of the quantization error to reduce measurement time. This article shows the effectiveness of this method by measurements performed on a prototype, designed and fabricated using standard 0.13 mu m CMOS technology. Experimental measurements show that the CDC achieves a resolution of 17 bits, with an effective area of 0.317 mm(2), which means a pressure resolution of 1 Pa, while consuming 146 mu A from a 1.5 V power supply.This work has been funded by Marie Curie project SIMIC, Grant Agreement No. 610484, funded by grants from the European Union (Research Executive Agency) and TEC2014-56879-R of CICYT, Spain.Publicad

A Self-repairable MEMS Comb Accelerometer

The final publication is available at www.springerlink.comIn this paper, a built-in self-repair technique for the MEMS comb accelerometer device is proposed. The main device of the comb accelerometer consists of n identical modules, and m modules are introduced as the redundancy. If any of the working module in the main device is found faulty during a built-in self-test (BIST), the control circuit will replace it with a good redundant module. In this way, the faulty device can be self-repaired through redundancy. The implementation of dualmode BIST on the BISR module is discussed. The sensitivity loss due to device modularization can be well compensated by different design alternatives. The yield model for MEMS redundancy repair is developed. The simulation results show that the BISR (built-in self-repair) design leads to effective yield increase compared to non-BISR design, especially for a moderate non-BISR yield. The yield as well as the reliability of the accelerometer can be improved due to the redundancy repair.http://link.springer.com/chapter/10.1007%2F1-4020-5261-8_1

DC and radio-frequency transmission characteristics of double-walled carbon nanotubes-based ink

In this paper, double-walled carbon nanotubes (DWNTs) network layers were patterned using inkjet transfer printing. The remarkable conductive characteristics of carbon nanotubes (CNTs) are considered as promising candidates for transmission line as well as microelectronic interconnects of an arbitrary pattern. In this work, the DWNTs were prepared by the catalytic chemical vapor deposition process, oxidized and dispersed in ethylene glycol solution. The DWNTs networks were deposited between electrodes contact and then characterized at DC through current-voltage measurements, low frequency, and high frequency by scattering parameters measurements from 40 MHz up to 40 GHz through a vector network analyzer. By varying the number of inkjet overwrites, the results confirm that the DC resistance of DWNTs networks can be varied according to their number and that furthermore the networks preserve ohmic characteristics up to 100 MHz. The microwave transmission parameters were obtained from the measured S-parameter data. An algorithm is developed to calculate the propagation constant "γ", attenuation constant "α" in order to show the frequency dependence of the equivalent resistance of DWNTs networks, which decreases with increasing frequency

MEMS Accelerometers

Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc

Built-In Self-Test Solution for CMOS MEMS Sensors

This thesis presents a new readout circuit with integrated Built-in Self-Test (BIST) structure for capacitive Micro-Electro-Mechanical Systems (MEMS). In the proposed solution instead of commonly used voltage control signals to test the device, charge control stimuli are employed to cover a wider range of structural defects. The proposed test solution eliminates the risk of MEMS structural collapse in the test phase. Measurement results using a prototype fabricated in TSMC 65nm CMOS technology indicate that the proposed BIST scheme can successfully detect minor structural defects altering MEMS nominal capacitance