Force feedback linearization for higher-order electromechanical sigma-delta modulators.

Abstract A higher-order electromechanical sigma–delta modulator can greatly improve the signal-to-noise ratio compared with a second-order loop that only uses the sensing element as a loop filter. However, the electrostatic force feedback on the proof mass is inherently nonlinear, which will produce harmonics in the output spectrum and limits the total signal-to-noise and distortion ratio. High performance inertial sensors, which use sigma–delta modulators as a closed-loop control system, have strict requirements on the output signal distortion. In this paper, nonlinear effects from the force feedback and pick-off circuits are analysed and a strategy for force feedback linearization is put forward which can considerably improve the signal-to-noise and distortion ratio. A PCB prototype of a fifth-order electromechanical modulator with a bulk micromachined accelerometer was used to demonstrate the concept

Micromachined vibratory gyroscopes controlled by a high order band-pass sigma delta modulator.

Abstract—This work reports on the design of novel closed-loop control systems for the sense mode of a vibratory-rate gyroscope based on a high-order sigma-delta modulator (SDM). A low-pass and two distinctive bandpass topologies are derived, and their advantages discussed. So far, most closed-loop force-feedback control systems for these sensors were based on low-pass SDM’s. Usually, the sensing element of a vibratory gyroscope is designed with a high quality factor to increase the sensitivity and, hence, can be treated as a mechanical resonator. Furthermore, the output characteristic of vibratory rate gyroscopes is narrowband amplitude- modulated signal. Therefore, a bandpass M is a more appropriate control strategy for a vibratory gyroscope than a low-pass SDM. Using a high-order bandpass SDM, the control system can adopt a much lower sampling frequency compared with a low-pass SDM while achieving a similar noise floor for a given oversampling ratio (OSR). In addition, a control system based on a high-order bandpass SDM is superior as it not only greatly shapes the quantization noise, but also alleviates tonal behavior, as is often seen in low-order SDM control systems, and has good immunities to fabrication tolerances and parameter mismatch. These properties are investigated in this study at system level

Analysis of circuit conditions for optimum intermodulation and gain in bipolar cascomp amplifiers with non-ideal error correction

The cascoded-compensation or ‘Cascomp’ amplifier offers excellent distortion reduction and thermal distortion rejection, but has not seen widespread use because of a limited gain and increased complexity compared with other topologies. The original theory showed that with the addition of an ideal error amplifier the circuit will completely compensate distortion for suitably chosen degeneration and bias values. This research presents a new, rigorous mathematical proof for conditions of compensation. The authors further develop the proof to include the non-idealities of the error amplifier. It is shown that there exists a second bias point, not exposed by the original analysis that offers improved gain while maintaining distortion cancellation. By reducing the error amplifier degeneration resistance, one can increase a Cascomp circuit's overall gain by several dB while maintaining theoretically perfect distortion compensation. A robust bias point is proposed, which takes the advantage of this new theory by optimising circuit values resulting in a comparatively broader and deeper third-order distortion null. The proposed theory is confirmed with simulation and measurement that show agreement within the bounds of process and component error limits

Three-dimensional Finite Elements method simulation of Total Ionizing Dose in 22 nm bulk nFinFETs

Finite Elements Method simulation of Total Ionizing Dose effects on 22 nm bulk Fin Field Effect Transistor (FinFET) devices using the commercial software Synopsys Sentaurus TCAD is presented. The simulation parameters are extracted by calibrating the charge trapping model to experimental results on 400 nm SiO2 capacitors irradiated under zero bias. The FinFET device characteristics are calibrated to the Intel 22 nm bulk technology. Irradiation simulations of the transistor performed with all terminals unbiased reveal increased hardness up to a total dose of 1 MRad(SiO2)

Three-dimensional Finite Elements Method simulation of Total Ionizing Dose in 22nm bulk nFinFETs

AbstractFinite Elements Method simulation of Total Ionizing Dose effects on 22nm bulk Fin Field Effect Transistor (FinFET) devices using the commercial software Synopsys Sentaurus TCAD is presented. The simulation parameters are extracted by calibrating the charge trapping model to experimental results on 400nm SiO2 capacitors irradiated under zero bias. The FinFET device characteristics are calibrated to the Intel 22nm bulk technology. Irradiation simulations of the transistor performed with all terminals unbiased reveal increased hardness up to a total dose of 1MRad(SiO2)

Total dose hardness of TiN/HfOx/TiN resistive random access memory

Resistive random access memory based on TiN/HfOx/TiN has been fabricated, with the stoichiometry of the HfOx layer altered through control of atomic layer deposition (ALD) temperature. Sweep and pulsed electrical characteristics were extracted before and after 60Co gamma irradiation. Monoclinic HfOx deposited at 400°C did not result in resistive switching. Deposition at 300°C and 350°C resulted in cubic HfOx which switched successfully. Both stoichiometric HfO2 and sub-oxides HfO2-x result in similar memory characteristics. All devices are shown to be radiation hard up to 10 Mrad(Si), independent of stoichiometry

Wireless power and network synchronisation for agricultural and industrial remote sensors using low voltage CMOS Harvesting and Data Demodulator IC

This paper presents a wide area medium frequency loosely coupled magnetic energy harvesting system with power delivery and network synchronisation for remote sensors, intended for agricultural and industrial environments. Intended for situations with poor service access, power is supplied from a source via a large area loop. Receiver nodes may use ferrite cored coils for good efficiency with modest volume. Transmission of low bandwidth network synchronisation data permits very low operational duty cycle with the need for real time clocks or wake up receivers and their associated power drain. As a key enabler for the system, a full custom energy harvester and QPSK data demodulator IC has been designed and fabricated in a commercial 180nm CMOS technology. The IC occupies 0.54mm2 and can deliver 10.3µW at 3V to an external battery or capacitor. With standard MOS device thresholds the rectifier can start from cold with only 250mV peak from the antenna loop, and the battery charge output is delivered with 330mV peak input. Results are presented from laboratory evaluation and from preliminary measurements in the field with a 10m x 10m loop driven at 800kHz