Wallace S. H. Wong

Longer MEMS Switch Lifetime Using Novel Dual-Pulse Actuation Voltage

A novel dual-pulse (NDP) actuation voltage has been proposed to reduce dielectric charging in microelectromechanical system (MEMS) switches, leading to a longer switch lifetime. Mathematical and transient circuit models have been utilized to simulate dielectric charging in the radio-frequency (RF) MEMS switch, enabling the analysis of the charge built up at the switch dielectric and the substrate brought about by the actuation-voltage curve used. The proposed DP actuation signal has shown to improve the lifetime of the RF MEMS switch as it minimizes the charge built up during its long continuous operation. Practical experiment on the commercial TeraVicta TT712-68CSP MEMS switch shows that the proposed actuation voltage can reduce the pull-in/pull-out voltage shift and therefore prolong the switch lifetime. The technique has also shown to reduce switching bounces.

Realization of a wideband bandpass filter using cascaded lowpass to highpass filter

This paper presents a wideband bandpass filter design, achieved by cascading a lowpass filter and a highpass filter. The lowpass filter is designed using L-C-ladder network, where relatively high impedance line is used to realize series inductor and low impedance line is used to realize shunt capacitor. For highpass filter, high impedance inductor line is grounded using metallic via and series capacitor is realized using inter-digital fingers structure. The lowpass and highpass filters are designed separately. These filters are then cascaded to obtain a wideband bandpass response with the passband ranges from 2.12 GHz to 4.06 GHz and a center frequency of 2.94 GHz. The filter has a pass-bandwidth of 66%. The simulated results show passband insertion loss of less than 1.6 dB. The measured results show good agreement with theoretical results.

Accurate Indoor Positioning Technique Using RSSI Assisted Inertial Measurement

An indoor positioning technique based on the inertial measurement of the object and the received signal strength indicator (RSSI) measured from an active RFID tag placed on the object is presented. The inertial measurement complements the inaccuracy of the RSSI measurements, especially when the object is far away from RFID reader. Correspondingly, a strong RSSI reading when the object is near a RFID reader provides accurate information about the location of the object. This information could then be used to amend the position estimated from the inertial measurement. Experiment has shown that the proposed technique provides better positioning accuracy.

Design and Modeling of an Electromagnetic Levitated and Actuated Micromotor

The design of an electromagnetic levitated and actuated micromotor is presented. The micromotor is consists of a counter-circular tracks that provide stable levitation force and radial parallel tracks that produce motoring rotational torque. Using simple filamentary representation of different features of the micromotor design, analytical expressions of the electromagnetic force produced by the features are derived and are used as foundation for the micromotor design. Finite element modeling is then used to analyze the actual micromotor design layout. From both the analytical and modeling results, the effects of different design features are presented. Finally, a macro-scale demonstrator is constructed to corroborate the micromotor design.

Smart hybrid energy storage for stand-alone PV microgrid: Optimization of battery lifespan through dynamic power allocation

In islanded microgrid system, the battery tends to be the most vulnerable element in terms of durability. Poorly managed battery charge/discharge process is one of the main life-limiting factors. To improve the battery life, a novel energy storage system topology and a power allocation strategy are proposed in this paper. A standalone 6kW Photovoltaic (PV) microgrid system with hybrid energy storage that combines battery and supercapacitor (SC) is considered. The performance of the proposed system is evaluated via model simulation using Matlab/Simulink. The system is simulated under a typical 24-hours residential load profile and the results demonstrated that the proposed system can provide sufficient power to regulate the fluctuations in supply and load whilst maintaining optimal batteries charged / discharged rate. The batteries were also operated under a low depth-of-discharge which prolongs the battery lifetime.

A comparison between voltage waveforms to enhance the lifetime of MEMS switch

Dielectric charging and mechanical bouncing are two vital lifetime limiting factors of RF MEMS switches. Among the numerous approaches to improve the reliability of RF MEMS switch, tailoring the applied actuation voltage waveform is an approach that does not require physical changes to the MEMS switch design. This paper compares the performance of different actuation voltage waveforms in terms of their capability of reducing dielectric charging and contact bouncing, sensitivity to MEMS switch variations, the resulting switching speed and the complexity in their implementation.

Performance degradation of defective MEMS tunable RF filter

The common defects that could occur during the fabrication and long term operation of a tunable bandpass filter using RF MEMS switches are simulated with SONNET. The faulty responses of the defective filter are then analyzed and linked to the defects that cause them. The work carried out aims at being able to narrow down and possibly identify the defects quickly in future by measuring the faulty filter responses, thus enabling defects to be screened quickly or for the development of built-in self-testable filter.

Smart Hybrid Energy Storage for Stand-Alone PV Microgrid: Optimization of Battery Lifespan through Dynamic Power Allocation

Battery as the key component in stand-alone PV microgrid system tends to be the most vulnerable element in terms of durability. Poorly managed battery charge/discharge process turns out to be one of the main life-limiting factors. To improve the longevity of battery storage system, a novel energy storage system topology and its smart power management strategy is presented in this paper. This paper proposes a stand-alone 6 kW PV microgrid system with hybrid energy storage system that combines supercapacitors and batteries. Smart power allocation strategy among the SC and the battery modules is designed to dynamically allocate the power to optimally charge/discharge the batteries while fulfilling the variations in supply and load. The performance of the proposed system is evaluated via model simulation using Matlab/Simulink. The system is simulated under a typical 24-hours residential load profile and the results proved that the proposed system can provide sufficient power to regulate the fluctuations in supply and load. During the process, the batteries are charged / discharged with ideal charge rate and operated under a low depth-of-discharge that have proven to prolong the battery lifetime.

Indoor positioning method based on inertial data, RSSI and compass from handheld smart-device

A novel indoor positioning method based on users inertial measurements, measured radio signal strength indicator (RSSI), and compass readings is presented. Based on distance travelled derived from inertial measurements and heading direction from compass readings, the users position is initially computed using Dead-Reckoning (DR) method. Then the estimated position, under certain condition, will be further corrected based on the RSSI and compass reading. Experiment results are presented to show the feasibility of the proposed method.

Fault Analysis of a MEMS Tuneable Bandpass Filter

The availability of Micro-Electro-Mechanical Systems (MEMS) switches has enabled the design of a high Q-factor but low insertion loss tuneable bandpass filter. This paper investigates the potential faults that could occur during fabrication and long term operation of a tuneable bandpass filter using MEMS switches. The causes of the filter defects and the resulting filter response will be identified, simulated and co- related, with the final aim of being able to identify the defects by measuring the faulty responses in the future. The different defects are simulated using SONNET to obtain the response of the faulty filter. Parameters such as insertion loss and return loss of the tuneable filter vary for different faults. In the future study, the defects will be recreated and tested experimentally to corroborate simulation findings. Eventually, a relationship between defects and the filter response will be developed.