Chean Hung Lai

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.

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.

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.

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.

Temperature dependent actuation voltage for longer MEMS switch lifetime

A temperature dependent actuation voltage has been proposed to minimize the dielectric charging effect in micro-electromechanical system (MEMS) switch, leading to an improved switch lifetime. Mathematical models have been utilized to model the pull-in voltage variation throughout a range of thermal condition and simulate dielectric charging in the RF MEMS switch, enabling the analysis of charge built-up at the switch dielectric layer and substrate at different ambient temperature condition. The proposed temperature dependent actuation voltage has shown to reduce the dielectric charging effect of the RF MEMS switch as it minimize the applied actuation voltage to the MEMS switch during its long continuous operation.