Stator Windings Fault Diagnostics of Induction Machines Operated From Inverters and Soft-Starters Using High-Frequency Negative-Sequence Currents

This paper studies the application of high-frequency voltage excitation-based stator winding diagnostic methods to three-phase ac machines operated from power converters that create the necessary high-frequency excitation as part of their normal operation. This paper focuses on two specific operating modes: 1) machines operated from inverters in the overmodulation region and 2) machines operated from soft-starters during startup. In both cases, high-frequency (in the range of the hundred hertz) voltage components at well-defined frequencies are created. The negative-sequence currents induced from these high-frequency voltages are shown to contain accurate information on the level of asymmetry (fault) in the machine. This information is significantly richer than exists in other modes of operation, i.e., inverters working in the linear modulation region or soft-starters in the steady state, and provides interesting opportunities to complement other diagnostic methods.     

High power-added efficiency MMIC amplifier for 2.4 GHz wirelesscommunications

This work describes the design and the measured performance of a high-efficiency monolithic microwave integrated circuit (MMIC) amplifier for wireless communications in the 2.4 GHz band. The monolithic technology employed in the circuit integration is based on standard 0.5-μm-gate-length MESFET. The design procedure is based on load-cycle graphic optimization of the transistor performance. On-wafer experimental characterization shows output power up to 24 dBm and excellent results of power-added efficiency up to 79% with 19.5 dBm output power at low drain bias voltage. The amplifier performance achieved and the circuit size, which is 1 mm², are suitable for use in the transmitter chains of wireless communication systems in the 2.4 GHz band     

Compact 2.5 Gb/s Burst‐Mode Receiver with Optimum APD Gain for XG‐PON1 and GPON Applications

This letter presents a compact 2.5 Gb/s burst‐mode receiver using the first reported monolithic amplifier IC developed with 0.25 …m SiGe BiCMOS technology. With optimum avalanche photodiode gain, the receiver module can obtain a fast response, high sensitivity and wide dynamic range, satisfying the overhead timing and various power specifications for a 2.5 Gb/s next‐generation passive optical network (PON), as well as a legacy 1.25 Gb/s PON in the upstream.     

3D crank-nicolson finite difference time domain method for dispersive media

The unconditionally stable Crank-Nicolson finite difference time domain (CN-FDTD) method is extended to incorporate frequency-dependent media in three dimensions. A Gaussian-elimination-based direct sparse solver is used to deal with the large sparse matrix system arising from the formulation. Numerical results validate and confirm that the scheme is unconditionally stable for time steps over the Courant-Friedrich-Lewy limit of classical FDTD.     

Angular MST‐Based Topology Control for Multi‐hop Wireless Ad Hoc Networks

This letter presents an angular minimum spanning tree (AMST) algorithm for topology control in multi‐hop wireless ad hoc networks. The AMST algorithm builds up an MST for every angular sector of a given degree around each node to determine optimal transmission power for connecting to its neighbors. We demonstrate that AMST preserves both local and network‐wide connectivity. It also improves robustness to link failure and mitigates transmission power waste.