Mohd Haris Md Khir

WI-FI ENERGY HARVESTER FOR LOW POWER RFID APPLICATION

In recent years, active Radio Frequency Identiflcation (RFID) tags have crossed into ultra low power domain. With obvious advantages over passive tags, a setback for active tag growth is the need for battery replacement and limited operational life. Battery life could be extended by scavenging surrounding Wi-Fi signals using rectenna architecture which consists of a receiving antenna attached to a rectifying circuit. A seven stage Cockroft-Walton voltage multiplier optimized for low input power (below 0dBm) is proposed. Prototype was fabricated on RT/Duroid 5880 (RO5880) printed circuit board (PCB) substrate with dielectric constant and loss tangent of 2.2 and 0.0009 respectively. Experimental results show that 2V output voltage can be harvested from an operating frequency of 2.48GHz with i9dBm (0.13mW) sensitivity with 1.57mm board thickness.

Design and modeling of MEMS resonator for magnetic field sensing using hybrid actuation technique

A novel design of 0.751MHz MEMS resonant magnetic field sensor of mass 0.775pg based on hybrid actuation technique (Lorentz force and Electrostatic force) is presented and simulated using Coventor Ware and CADENCE simulators. The sensor consists of Aluminum paddle resonator, two supporting beams, driving electrodes, sensing electrode and silicon substrate with a capacitive CMOS readout amplifier. Working in a resonant condition, the sensors vibration amplitude is converted into the sensing capacitance change, which reflects the outside magnetic flux-density. Based on the simulation, the key structure parameters are optimized and the resonant frequency is estimated. The results of the device are in accordance with the theoretical results of the designed model. The resolution of the sensor is 1 nT. The results indicate its sensitivity more than 0.01 nV/nT, when operating at a normal atmosphere. The sensitivity and resolution can be enhanced through vacuum packaging.

Fabrication and Characterization of a CMOS-MEMS Humidity Sensor

This paper reports on the fabrication and characterization of a Complementary Metal Oxide Semiconductor-Microelectromechanical System (CMOS-MEMS) device with embedded microheater operated at relatively elevated temperatures (40 °C to 80 °C) for the purpose of relative humidity measurement. The sensing principle is based on the change in amplitude of the device due to adsorption or desorption of humidity on the active material layer of titanium dioxide (TiO2) nanoparticles deposited on the moving plate, which results in changes in the mass of the device. The sensor has been designed and fabricated through a standard 0.35 µm CMOS process technology and post-CMOS micromachining technique has been successfully implemented to release the MEMS structures. The sensor is operated in the dynamic mode using electrothermal actuation and the output signal measured using a piezoresistive (PZR) sensor connected in a Wheatstone bridge circuit. The output voltage of the humidity sensor increases from 0.585 mV to 30.580 mV as the humidity increases from 35% RH to 95% RH. The output voltage is found to be linear from 0.585 mV to 3.250 mV as the humidity increased from 35% RH to 60% RH, with sensitivity of 0.107 mV/% RH; and again linear from 3.250 mV to 30.580 mV as the humidity level increases from 60% RH to 95% RH, with higher sensitivity of 0.781 mV/% RH. On the other hand, the sensitivity of the humidity sensor increases linearly from 0.102 mV/% RH to 0.501 mV/% RH with increase in the temperature from 40 °C to 80 °C and a maximum hysteresis of 0.87% RH is found at a relative humidity of 80%. The sensitivity is also frequency dependent, increasing from 0.500 mV/% RH at 2 Hz to reach a maximum value of 1.634 mV/% RH at a frequency of 12 Hz, then decreasing to 1.110 mV/% RH at a frequency of 20 Hz. Finally, the CMOS-MEMS humidity sensor showed comparable response, recovery, and repeatability of measurements in three cycles as compared to a standard sensor that directly measures humidity in % RH.

Aperture and Mutual Coupled Cylindrical Dielectric Resonator Antenna Array

A 1 £ 3 element linear array using cylindrical dielectric resonator antennas (CDRAs) is designed and presented for 802.11a WLAN system applications. The top and bottom elements of CDRA array are excited through the rectangular coupling slots etched on the ground plane, while the slots themselves are excited through the microstrip transmission line. The third element (i.e., central CDRA) is excited through the mutual coupling of two radiating elements by its sides. This mechanism enhances the bandwidth (96.1%) and gain (14.3%) as compared to aperture coupled technique. It is also observed that the side lobe levels are reduced over the designed frequency band. Using CST microwave studio, directivity of 10.5dBi has been achieved for operating frequency of 5.6GHz. Designed antenna array is fabricated and tested. Simulated and measured results are in good agreement. The equivalent lumped element circuit is also designed and presented using Advanced design system (ADS) for this proposed array.

Analysis of frequency up-conversion based vibration energy harvesting

Mechanical frequency up-conversion has been suggested by many researchers in order to increase power density of kinetic energy harvesters. In this paper analytical analysis of frequency up-conversion mechanism has been carried out in some detail. It has been shown that sources of actuation for a frequency increased generator can be categorized as force limited and displacement limited sources. Maximum energy transferring conditions have been investigated for both types. The settling time of the transient motion of the high frequency oscillator has been shown to be dependent on the seismic mass. Effects of premature excitation and natural frequency of high frequency resonator on average power have also been investigated. A relationship has been developed between frequency of ambient vibration and optimal natural frequency of frequency increased generator.

A CMOS-MEMS cantilever sensor for capnometric applications

Capnometers monitor the concentration of CO2 in exhaled breath, which can be a life saving modality. High cost, big size and high power consumption of the conventional capnometers limit their scope and adaption. To overcome these issues, a CMOS MEMS microcantilever based CO2 sensor is proposed for capnometric applications. The microcantilever is manufactured using CMOSMEMS technology and its critical parameters are analytically investigated. The optimized microcantilever has a quality factor, sensitivity and resolution of 3116, 16 mHz/ppm and 0.31 ppb, respectively.

A CMOS MEMS Resonant Magnetic Field Sensor with Differential Electrostatic Actuation and Capacitive Sensing

This paper is about CMOS MEMS resonant magnetic field sensor in which differential electrostatic actuation, capacitive sensing, resonant frequency, quality factor and sensitivity of interdigitated comb resonator is investigated. Information is embedded in the output signal frequency because it is robust against the interference from other sources during transmission. At damping ratio of 0.0001, resonant frequency of the comb resonator is 4.35 kHz with quality factor 5000 and amplitude 18.45 μm. Sensitivity of the device towards external magnetic field is 9.455 mHz/nT which is 10,000 times improved than recently published data.

Implementation of wireless sensor network in oil and gas specifically for personnel positioning application

The invention of WSN-based indoor positioning is to design effective personnel positioning system, monitor the personnel movement in oil and gas platform and alert the personnel if they entered a restricted area. Personnel tracking system in hazardous working environment such as in oil gas platform is very crucial due to GPS incapability inside a concrete building structure. Real-time monitoring of personnel health and condition is a top priority for immediate response in emergency situation. Communication device limitation in oil and gas platform will be hard for the supervisor to inform the personnel for an emergency evacuation. Personnel position application using WSN is determined based on RSSI values of multiple XBee multipoint RF modules consist of personnel node, fixed nodes and server node. A positioning algorithm will be used for the estimation of personnel location in the oil and gas platform. Sectioning method using XBee IEEE 802.15.4 as a WSN is proposed for personnel positioning application.

RF MEMS Based Half Mode Bowtie Shaped Substrate Integrated Waveguide Tunable Bandpass Filter

A tunable planar bandpass filter based on a technique that utilizes a half mode substrate integrated waveguide (HMSIW) and novel inter-resonator coupling is presented. The tunable HMSIW based bandpass filter is implemented using two half triangle shaped cavities coupled together through inter-resonator coupling forming half mode bowtie shaped structure. The bowtie-shaped filter exhibits similar performance as found in rectangle- and circle-shaped SIW based bandpass filters. This concept reduces the circuit foot print, and miniaturization high quality factor is maintained by the structure. The tunable filter utilizes packaged RF MEMS switches; switching between different configurations of switches achieves four distinctive frequency states between 4.8-5.3 GHz. The filter maintains a constant absolute 1 dB bandwidth of 100 ± 10 MHz for all frequency states.

Design, modeling and simulation of CMOS MEMS cantilever for carbon dioxide gas sensing

Carbon dioxide sensors have potential applications in medical diagnoses, health care, environmental monitoring, food and medicine industry. In recent years, many novel biological, physical and chemical sensors have employed microcantilevers due to their simplicity, ease of fabrication and integration with electronics. This paper presents design, modeling and simulation of a microcantilever working in dynamic mode for CO2 gas sensing with electromagnetic actuation and capacitive sensing using comb fingers. The sensor is based upon 0.35 micron CMOS technology. CoventorWare and MATLAB have been used as simulation software. According to the developed model and simulation results the resonator has a quality factor of 3333 in air and mass sensitivity of 3.2 Hz/ng.