Advanced understanding of the physics makes phase change materials (PCM) and metal-insulator transition (MIT) materials great candidates for direct current (DC) and radio frequency (RF) switching applications. In the literature, germanium telluride (GeTe), a PCM, and vanadium dioxide (VO 2), an MIT material have been widely investigated for DC and RF switching applications due to their remarkable contrast in their OFF/ON state resistivity values. In this review, innovations in design, fabrication, and characterization associated with these PCM and MIT material-based RF switches, have been highlighted and critically reviewed from the early stage to the most recent works. We initially report on the growth of PCM and MIT materials and then discuss their DC characteristics. Afterwards, novel design approaches and notable fabrication processes; utilized to improve switching performance; are discussed and reviewed. Finally, a brief vis-á-vis comparison of resistivity, insertion loss, isolation loss, power consumption, RF power handling capability, switching speed, and reliability is provided to compare their performance to radio frequency microelectromechanical systems (RF MEMS) switches; which helps to demonstrate the current state-of-the-art, as well as insight into their potential in future applications.

Today's advanced high‐speed technology requires building behavioral models of systems, from measured/simulated data, with increasingly higher operating frequencies. Different research efforts have come to light in literature for macromodeling, based on such types of data. Ensuring passivity is one of the most fundamental issues affecting system macromodeling, because system‐level performance can be unstable if even a single component of the system becomes nonpassive. Thus, from the computer‐aided design perspective, generation and provision of macromodels, while preserving passivity, is a significant challenge. In this paper, we carefully review novel techniques of passive macromodeling as well as their passivity verification and enforcement, from the early days to the present. We critically review the prominent methods in literature developed for macromodeling, and for verification and enforcement of passivity, and emphasize on their strengths and shortcomings.

Due to the variation of solar irradiance, temperature and shading conditions, the power generated by a photovoltaic (PV) module and hence the power delivered to the load changes drastically, which imposes the need for analysis of a complete PV system to get the maximum power under these natural variable conditions. In this paper, a complete off-grid PV module based power generation system has been designed and simulated using MATLAB/Simulink and performance has been scrutinized using the value of standard solar irradiance about 1 KW/m-2 for Bangladesh. The simulation model includes solar PV module, the converter power stage with MPPT control and charge controlling functions and here performance of each block has been examined conspicuously. Eventually, it has been found that the model is quite competent to simulate both the I-V and P-V characteristics of a PV module and based on the result it has been predicted that the performance of several modules or even PV array connected in series and/or in parallel with the delivery of maximum power can be tested under different solar irradiance and temperature conditions. DOI: http://dx.doi.org/10.3329/dujs.v62i2.21977 Dhaka Univ. J. Sci. 62(2): 127-132, 2014 (July)

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In microelectromechanical systems (MEMS) switches, the microcontact is crucial in determining reliability and performance. In the past, actual MEMS devices and atomic force microscopes (AFM)/scanning probe microscopes (SPM)/nanoindentation-based test fixtures have been used to collect relevant microcontact data. In this work, we designed a unique microcontact support structure for improved post-mortem analysis. The effects of contact closure timing on various switching conditions (e.g., cold-switching and hot-switching) was investigated with respect to the test signal. Mechanical contact closing time was found to be approximately 1 us for the contact force ranging from 10–900 μN. On the other hand, for the 1 V and 10 mA circuit condition, electrical contact closing time was about 0.2 ms. The test fixture will be used to characterize contact resistance and force performance and reliability associated with wide range of contact materials and geometries that will facilitate reliable, robust microswitch designs for future direct current (DC) and radio frequency (RF) applications.