Muhammad Umer Mian

A monolithic, low-noise, capacitive readout interface circuit for CMOS-MEMS resonator-based gravimetric chemical gas sensors

This paper presents a monolithic, low-noise capacitive readout interface circuit for CMOS-MEMS resonator based gravimetric chemical gas sensors. In these sensor devices, where the sense capacitances are usually very weak, the readout interface circuit plays a crucial role in determining the overall sensor performance. Noise is observed in various active and passive devices affecting circuit performances. Particularly at low frequencies, flicker noise is dominant in degrading the quality of output signals. A dual stage, open-loop continuous time voltage sensing with chopper stabilization technique is proposed in this work to cope with it and improve the total output signal SNR. The proposed circuit is designed based on MIMOS 0.35 μm AMS 3.3V CMOS technology. Cadence Spectre circuit simulator simulation results show, the proposed circuit achieves an input inferred noise of 11.6 n V/√(Hz), total gain of 48.1 dB and consumes a total power of 3.385 mW. The designed circuit is able to detect minute capacitance changes as low as 0.0365 aF with total sensitivity of 67.95 μV/aF.

Optical and capacitive characterization of MEMS magnetic resonator

In this paper a Lorentz force driven Micro ELectro Mechanical Sytems (MEMS) resonator fabricated on PolyMUMP process with optical and capacitive sensing is presented. The resonator is designed by combining the two poly layers which result in an increase in the thickness of the resonator. Lorentz force generates lateral displacements at low driving voltages which are proportional to the magnetic field and the input current. A displacement of more than 9.8 μm was achieved with a magnetic field of 0.12T and a driving current of 27mA. Magnetic sensitivity of 1.41V/T in air was experimentally measured using permanent magnets and capacitive sensing circuitry. Optical results demonstrate the sensitivity values between 0.090μm/mT and 0.074μm/mT.

A 2D mapping spy robot worldwide auto and manually controllable for surveillance features

Todays most challenging thing in the world is security. Due to increasing terrorism activities in the world, countless lives of security persons and civilians including children and women are lost. The biggest problem faced by the security agencies is to track terrorists and trace the shelter of these people involved in these activities. Many security officers have lost their lives during raid on these shelters. The most desired solution of this issue is to have map of suspicious building/target and location of the persons in the building and other dangerous places that can significantly reducing the loss of life. Purpose of this research is to design a spy rover that can be sent to the suspicious place with IP camera and video transmitter, which can help us to build the map of that location using sonar sensors, encoders, gyroscope and compass signaling the map to the remote area through wireless network. Target area can be monitored by using private network. Despite its wide applications for defence purposes this robot can also be used to map any area affected by the disaster where human access is dangerous or impossible. The rover can be controlled wirelessly from the remote area and also it has ability of intelligent decisions due to sensors and internal program instruction. If wireless control is lost with rover then it is switched to the auto mode and performs its predefined task. Gyroscope helps to find the position of rover and to map the environment. Such kind of robot can help security personals to monitor suspected places and to carry out more successful raids at difficult place with the minimum casualty.

MetalMUMPs resonator for acetone vapor sensing

Acetone vapor monitoring is essential in workplace for human health and safety, where exposure to acetone concentration more than 176 parts per million (ppm) can cause damage to eyes, liver, kidneys and central nervous system. In addition, acetone in exhaled breath is known to be good biomarker for non-invasive screening of diabetes. The most common used acetone vapor sensors are based on metal oxide semiconductor sensors, which work at higher temperatures, and hence consume more power. This paper reports MetalMUMPs device for acetone vapor sensing for environmental monitoring. The device is based on electrothermal actuation and capacitive sensing using differential capacitance measurement technique. MS3110 universal capacitive readout circuit was used to readout the small change of the static capacitance when the device is actuated using 0.71 Vrms with a driving frequency range of 0.5 kHz–8 kHz. The output signal of the circuit is given as a voltage and it can be directly related to the capacitance change. The output voltage change was found to increase linearly with increasing the acetone vapor concentration from 100 ppm to 500 ppm with a concentration sensitivity of 0.65 mV/ppm.

CMOS-MEMS resonator parametric variation analysis through equivalent circuit modeling

In this paper, we report a micro electro mechanical system (MEMS) shuttle resonator fabricated on CMOS-MEMS wafer technique. The resonator operates at the resonant frequency when a current flows through the metal layers in the presence of an external magnetic field. We investigate the resonant frequency and amplitude shifts due to parametric variation in beam length, width, and structure thickness in resonator motion. The theoretical formulation of the equivalent circuit model is presented. Simulation of resonator with variations are carried out using equivalent circuit model, these variations are based on fabrication foundry tolerance range. Simulation results show a range of operational frequencies in which the resonator can perform under the fabrication tolerances provided by the foundry.

Characterization of embedded microheater of a CMOS-MEMS gravimetric sensor device

A CMOS-MEMS device for mass detection has been designed using 2008 CoventorWare software and fabricated using 0.35źm CMOS technology. This paper reports the characterization of the microheater and the temperature sensor embedded in the device. The measured resistances of the microheater and the temperature sensor were found to be close to the modeled values within ~4.2% error. The average temperature coefficient of resistance (TCR) of the temperature sensor of five dies was determined by increasing or decreasing the temperature in a range of 25°C-100°C. The resistance of the temperature sensor was found to increase with either an increase in ambient temperature or the voltage applied to the microheater, with a correlation factor of 0.99. The average TCR was found to be 0.0034/°C for the increasing temperature and 0.0036/°C for the decreasing temperature as compared to 0.0037°C reported in the literature, indicating an error of 8.1% and 3.5%, respectively. These differences between the measured and reported values are believed to be due to fabrication tolerances in the design dimensions or the material properties. The humidity was found to have a negligible effect on the resistance of the temperature sensor for increasing humidity levels from 40% to 90%. The repeatability of the measurements has shown low standard errors, which gives confidence in the reliability of the fabricated device.

Design of PolyMUMPS device for diabetes screening via acetone vapor detection in exhaled breath

Diabetes is a chronic disease that occurs due to deficiency or improper use of insulin by body tissues. It is currently diagnosed invasively by measuring blood glucose. This paper reports modelling and simulation of a PolyMUMPS device proposed for a non-invasive screening of diabetes. The device is electromagnetically driven at its resonance frequency using Lorenz force, while the output is detected by capacitive means. The resonance frequency of the first mode was obtained by CoventorWare software and it was found to be 18.552 kHz compared to its modelled value of 17.211 kHz, within an error of 7.2 %. Maximum displacement of 8.35 µm and capacitance of 29.57 fF were obtained when the device was driven by applying 15 mA current and 50 mT magnetic field.

Noise minimization techniques for modulator demodulator circuits used for chopper stabilization in CMOS-MEMS sensor applications

This paper presents design, simulation and study of different noise minimization techniques that should be used in chopper stabilization circuits for CMOS-MEMS sensor readout interface circuit applications. Chopper stabilization technique is widely used in CMOS-MEMS sensors, as it is effective in tackling low frequency noises including the most dominant, flicker noise (1/f). In CMOS-MEMS sensors where noise is one of the main design targets, it is necessary to minimize noise arising from the chopper stabilization circuit itself to boost the overall noise performance. Chopper circuits contribute part of the total input referred noise and appropriate techniques need to be deployed in place to minimize the overall effect. Here in this work, different techniques which should be considered to reduce noise from the chopper circuits are discussed and analyzed. The demonstrated work is designed in MIMOS 0.35 μm AMS CMOS 3.3 V CMOS process technology and Cadence Spectre circuit simulator is used to verify and analyze the circuit performances.

MEMS 3-DoF gyroscope design, modeling and simulation through equivalent circuit lumped parameter model

Pre-fabrication, behavioural and performance analysis with computer aided design (CAD) tools is a common and fabrication cost effective practice. In light of this we present a simulation methodology for a dual-mass oscillator based 3 Degree of Freedom (3-DoF) MEMS gyroscope. 3-DoF Gyroscope is modeled through lumped parameter models using equivalent circuit elements. These equivalent circuits consist of elementary components which are counterpart of their respective mechanical components, used to design and fabricate 3-DoF MEMS gyroscope. Complete designing of equivalent circuit model, mathematical modeling and simulation are being presented in this paper. Behaviors of the equivalent lumped models derived for the proposed device design are simulated in MEMSPRO T-SPICE software. Simulations are carried out with the design specifications following design rules of the MetalMUMPS fabrication process. Drive mass resonant frequencies simulated by this technique are 1.59 kHz and 2.05 kHz respectively, which are ...