Novel zero-voltage and zero-current-switching (ZVZCS) full-bridge PWM converter using coupled output inductor

A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge pulse-width-modulated (PWM) converter is proposed to improve the previously proposed ZVZCS full-bridge PWM converters. By employing a simple auxiliary circuit with neither lossy components nor active switches, soft-switching of the primary switches is achieved. The proposed converter has many advantages such as simple auxiliary circuit, high efficiency, low voltage stress of the rectifier diode and self-adjustment of the circulating current, which make the proposed converter attractive for the high voltage and high power applications. The principles of operation and design considerations are presented and verified on the 4 kW experimental converter operating at 80 kHz.     

Parallel feed travelling wave distributed pin photodetectors withintegrated MMI couplers

The fabrication and performance of a parallel feed travelling wave photodetector with pin diodes operating at 1550 nm is presented. A parallel optical feed using an integrated multimode interference (MMI) power splitter helps increase the maximum linear photocurrent through a more uniform distribution of photocurrent. The maximum DC linear current measured is 52.2 mA. Maximum linear RF power at 10 GHz was 9 dBm     

A novel droop method for converter parallel operation

For the converter parallel operation, the current sharing between modules is important for the reliability of the system. Among several current sharing schemes, the droop method needs no interconnection between modules, which implies true redundancy. But the droop method has poor voltage regulation and poor current sharing characteristics. In this paper, a novel droop method is proposed for the converter parallel operation, which adaptively controls the reference voltage of each module. This greatly improves the output voltage regulation and the current sharing of the conventional droop method. The analysis of the proposed method and design procedure are provided and experimental results verify the excellent performance of the proposed method     

A novel spectrum sensing scheme with sensing time optimization for energy-efficient CRSNs

Wireless Networks - The cognitive radio technology enables secondary users (SUs) to occupy licensed bands when primary users (PUs) are not occupy them. Spectrum sensing is a key technology for SUs...     

Estimation of anomaly location and size using electrical impedance tomography

We developed a new algorithm that estimates locations and sizes of anomalies in electrically conducting medium based on electrical impedance tomography (EIT) technique. When only the boundary current and voltage measurements are available, it is not practically feasible to reconstruct accurate high-resolution cross-sectional conductivity or resistivity images of a subject. In this paper, we focus our attention on the estimation of locations and sizes of anomalies with different conductivity values compared with the background tissues. We showed the performance of the algorithm from experimental results using a 32-channel EIT system and saline phantom. With about 1.73% measurement error in boundary current-voltage data, we found that the minimal size (area) of the detectable anomaly is about 0.72% of the size (area) of the phantom. Potential applications include the monitoring of impedance related physiological events and bubble detection in two-phase flow. Since this new algorithm requires neither any forward solver nor time-consuming minimization process, it is fast enough for various real-time applications in medicine and nondestructive testing.     

Adaptive random access and resource allocation scheme based on traffic load in HiperLAN type2 system

The MAC protocol of HiperLAN type2 is based on TDMA/TDD and provides access control and resource allocation schemes. We propose a scheme that provides adaptive random access and efficient resource allocation according to the traffic load for HiperLAN type2, by using access probability. The analysis and simulation results show that the proposed scheme performs better than the conventional scheme and supports priority services easily.     

Numerical accuracy of multipole expansion for 2D MLFMA

A numerical study of the multipole expansion for the multilevel fast multipole algorithm (MLFMA) is presented. In the numerical implementation of MLFMA, the error comes from three sources: the truncation of the addition theorem; the approximation of the integration; the aggregation and disaggregation process. These errors are due to the factorization of the Green's function which is the mathematical core of the algorithm. Among the three error sources, we focus on the truncation error and a new approach of selecting truncation numbers for the addition theorem is proposed. Using this approach, the error prediction and control can be improved for the small buffer sizes and high accuracy requirements.     

A new a-Si:H thin-film transistor pixel circuit for active-matrix organic light-emitting diodes

We propose a new pixel circuit using hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs), composed of three switching and one driving TFT, for active-matrix organic light-emitting diodes (AMOLEDs) with a voltage source method. The circuit simulation results based on the measured threshold voltage shift of a-Si:H TFTs by gate-bias stress indicate that this circuit compensates for the threshold voltage shifts over 10000 h of operation.     

Performance Analysis on Coexistence of EDCA and Legacy DCF Stations in IEEE 802.11 Wireless LANs

The distributed coordination function (DCF) scheme of IEEE 802.11 MAC protocol does not support any concepts of quality of service (QoS) but the enhanced distributed channel access (EDCA) scheme in IEEE 802.11e standard provides QoS according to access categories using different access parameters. However, the legacy DCF stations may be used together with EDCA stations. In this letter, we investigate and analyze the performance discrimination when EDCA and DCF stations operate simultaneously