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This article presents a new design of a wideband, compact, and low-cost symmetric five-port reflectometer (5PR). The proposed 5PR features a wide operational bandwidth of 3240 MHz (about 162% centered at 2 GHz). Five-symmetric branch-lines consist of SCURVE, STEE, SLIN, and Term were designed and optimized to achieve an equivalent value of 78 dB for S 11 , S 22 , S 33 , S 44 , and S 55 at center frequency of 2 GHz. Such consistent value between those S-parameters proven a perfect matching impedance are successfully obtained by proposed symmetric 5PR even own a bandwidth as high as 162%. Moreover, the simulated and measured results show the proposed 5PR has realized magnitude of % 0 dB (S 11 ), 0.5 (S 12 , S 13 , S 14 , S 15 , S 21 , S 23 . . . S 54 ) as well as phase relative error of 1208 which in parallel to theoretical values. With all capabilities mentioned, the proposed 5PR is a promising candidate to be installed in a microwave imaging system for biomedical applications in the future.

Abstract-Several forms of vibration-driven MEMS microgenerator are possible and are reported in the literature, with potential application areas including distributed sensing and ubiquitous computing. This paper sets out an analytical basis for their design and comparison, verified against full time-domain simulations. Most reported microgenerators are classified as either velocity-damped resonant generators (VDRGs) or Coulomb-damped resonant generators (CDRGs) and a unified analytical structure is provided for these generator types. Reported generators are shown to have operated at well below achievable power densities and design guides are given for optimising future devices. The paper also describes a new class-the Coulomb-force parametric generator (CFPG)-which does not operate in a resonant manner. For all three generators, expressions and graphs are provided showing the dependence of output power on key operating parameters. The optimization also considers physical generator constraints such as voltage limitation or maximum or minimum damping ratios. The sensitivity of each generator architecture to the source vibration frequency is analyzed and this shows that the CFPG can be better suited than the resonant generators to applications where the source frequency is likely to vary. It is demonstrated that mechanical resonance is particularly useful when the vibration source amplitude is small compared to the allowable mass-to-frame displacement. The CDRG and the VDRG generate the same power at resonance but give better performance below and above resonance respectively. Both resonant generator types are unable to operate when the allowable mass frame displacement is small compared to the vibration source amplitude, as is likely to be the case in some MEMS applications. The CFPG is, therefore, required for such applications.[944]

This paper describes the analysis, simulation and testing of a microengineered motion-driven power generator, suitable for application in sensors within or worn on the human body. Micro-generators capable of powering sensors have previously been reported, but these have required high frequency mechanical vibrations to excite a resonant structure. However, bodydriven movements are slow and irregular, with large displacements, and hence do not effectively couple energy into such generators. The device presented here uses an alternative, non-resonant operating mode. Analysis of this generator shows its potential for the application considered, and shows the possibility to optimise the design for particular conditions. An experimental prototype based on a variable parallel-plate capacitor operating in constant charge mode is described which confirms the analysis and simulation models. This prototype, when precharged to 30 V, develops an output voltage of 250 V, corresponding to 0.3 µJ per cycle. The experimental test procedure and the instrumentation are also described.

21.1.14 KB. Ok to add accepted version to spiral, IEEE polic

Abstract-Inductive Power Transfer (IPT) systems for transmitting tens to hundreds of watts have been reported for almost a decade. Most of the work has concentrated on the optimization of the link efficiency and have not taken into account the efficiency of the driver. Class-E amplifiers have been identified as ideal drivers for IPT applications, but their power handling capability at tens of MHz has been a crucial limiting factor, since the load and inductor characteristics are set by the requirements of the resonant inductive system. The frequency limitation of the driver restricts the unloaded Q factor of the coils and thus the link efficiency. With a suitable driver, copper coil unloaded Q factors of over 1,000 can be achieved in the low MHz region, enabling a cost-effective high Q coil assembly. The system presented in this paper alleviates the use of heavy and expensive field-shaping techniques by presenting an efficient IPT system capable of transmitting energy with a dc-to-load efficiency above 77% at 6 MHz across a distance of 30 cm. To the authors knowledge this is the highest dc-to-load efficiency achieved for an IPT system without introducing restrictive coupling factor enhancement techniques.

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Voltage-Source Converters have brought numerous advantages to HVDC transmission. However, they suffer from high losses and are usually weak against faults on the DC-side. In this paper, a new topology which brings together some concepts from traditional Current Source Converters and multi-level converters, is presented. Two stacks of Hbridge cells alternate to construct the converter voltage using director switches made of IGBTs in series. The resulting converter generates AC current with low harmonic content and with low loss. Furthermore, the converter is still very responsive in case of a fault. This paper first explains the composition and the working of this converter, then detailed simulations at 20 MW illustrate the performances and low losses of this converter under normal conditions. The ability of this topology to deal with abnormal conditions is also demonstrated, especially its ability to keep control of the current despite the collapse of the DC bus voltage, e.g. a DCside fault.