Transmission Characteristics of Hybrid Modes in Corrugated Waveguides Above the Bragg Frequency

We studied the transmission characteristics of hybrid modes in a corrugated circular waveguide above the Bragg frequency to develop a broad-band transmission line for millimeter waves. Millimeter waves at 294 GHz were transmitted into a straight waveguide. From observed power profiles in waveguide cross-sections, a high attenuation rate of 0.13 dB/m was obtained. To match a theoretical attenuation constant with the experimental one, we introduced an ad hoc coefficient of conventional surface reactance in the waveguide wall. This was necessary because the wall began to look like the surface with a decreasing anisotropic reactance owing to the frequency above the Bragg frequency. Using nonlinear optimization for mode content analysis, the observed power profiles in the waveguide cross-section were matched with theoretical profiles. There was good agreement between the calculated and observed centers of power profiles and attenuation rate along the waveguide. The theoretical analysis showed that the magnetic field at the waveguide wall increases and the substantial attenuation takes place. Above the Bragg frequency coupling to backwards propagating modes is a point of consideration. A combination of the backwards propagating EH_1,26 and the forward propagating HE₁₁ modes satisfied the Bragg condition at 294.7 GHz which was the nearest frequency of operating frequency. A strong attenuation of the incoming HE₁₁ mode by Bragg resonance was not expected due to large difference of 0.7 GHz. It becomes clear that the observed high transmission loss outside of the Bragg resonance can be explained by a decrease in anisotropic surface reactance at the wall.     

Propagation characteristics in open-groove waveguides surrounded by rough sidewalls

The radio propagation characteristics in groove-shaped roads surrounded by rough surface sidewalls are presented. Typical sidewalls are snowpack in heavy snow regions or buildings in urban areas. In this analysis, such roads are modeled by a straight groove waveguide with statistically rough sidewalls. A simple geometrical optical approach is applied to calculate the field strength along the longitudinal direction of the road as well as transversely across the road. The theoretical results are compared with previously presented experimental results. The theoretical results show that the surface roughness causes an additional propagation loss in regions far from the transmitting point and that the field strength in the cross section exhibits a cosine distribution with a slightly changing magnitude. These theoretical characteristics agree with the experimental results.<>     

A highly integrated 40-MIPS (peak) 64-b RISC microprocessor

A 1-million transistor 64-b microprocessor has been fabricated using 0.8-μm double-metal CMOS technology. A 40-MIPS (million instructions per second) and 20-MFLOPS (million floating-point operations per second) peak performance at 40 MHz is realized by a self-clocked register file and two translation lookaside buffers (TLBs) with word-line transition detection circuits. The processor contains an integer unit based on the SPARC (scalable processor architecture) RISC (reduced instruction set computer) architecture, a floating-point unit (FPU) which executes IEEE-754 single- and double-precision floating-point operations a 6-KB three-way set-associative physical instruction cache, a 2-KB two-way set-associative physical data cache, a memory management unit that has two TLBs, and a bus control unit with an ECC (error-correcting code) circuit     

Study of Superconducting Fault Current Limiter Using Vacuum Interrupter Driven by Electromagnetic Repulsion Force for Commutating Switch

Using a high-temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor and the vacuum interrupter as the commutation switch were connected in parallel using a bypass coil. When the fault current flows in this equipment, the superconductor is quenched and the current is transferred to the parallel coil because of the voltage drop in the superconductor. This large current in the parallel coil actuates the magnetic repulsion mechanism of the vacuum interrupter. Due to the opening of the vacuum interrupter, the current in the superconductor is broken. By using this equipment, the current flow time in the superconductor can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of the parallel coil     

A dynamic multicast routing satisfying multiple QoS constraints

In this paper we propose a QoS‐based routing algorithm for dynamic multicasting. The complexity of the problem can be reduced to a simple shortest path problem by applying a Weighted Fair Queuing (WFQ) service discipline. Using a modified Bellman–Ford algorithm, the proposed routing builds a multicast tree, where a node is added to the existing multicast tree without re‐routing and satisfying QoS constraints. With user defined life‐time of connection this heuristic algorthm builds multicast tree which is near optimum over the whole duration of session. Simulation results show that tree costs are nearly as good as other dynamic multicast routings that does not consider QoS. Copyright © 2003 John Wiley & Sons, Ltd.     

Solid: High-voltage,high-gain 300 nm channel-length MOSFETs—I. Simulation

A simple, novel structure for MOSFETs with channels 300–500 nm long is proposed and evaluated by means of two-dimensional numerical analysis. The new device is constructed of a silicide-on-lightly-doped-drain (SOLID) structure. In this structure, the silicide layers assure lower parasitic source/drain resistances. Moreover, distinct segregation phenomena, i.e., formation of a highly concentrated, thin (10 nm) layer at the source/drain-silicide interface, perform an important role in achieving good ohmic contact. With the SOLID structure, most of the N⁺ drain region, which occupies a large portion of the conventional profile-drain structure and is superfluous for lowering high drain field, canbe replaced by an N^? region. This results is improved breakdown voltage characteristics with significant mitigation of current gain reduction. The features of the SOLID structure are also compared with those of conventional profile-drain structures, i.e. double diffused drain (DDD) and lightly doped drain (LDD) structures.     

Optical polarisation control utilising an optical heterodyne detection scheme

An optical polarisation control scheme utilising optical heterodyne detection for coherent transmission is proposed and demonstrated at a wavelength of 1.5 ?m. It converts an arbitrary polarisation state to a linear state at a received optical power level of less than ?70 dBm.     

Low-threshold and high temperature single-longitudinal-mode operation of 1.55 ?m-band DFB-DC-PBH LDs

1.55 ?m-band distributed-feedback laser diodes with double-channel planar buried heterostructure (DFB-DC-PBH LDs) have been developed. As well as low threshold current, 19 mA at room temperature, stable CW single-longitudinal-mode operation up to the high power level of 23 mW and the high temperature of 108°C has been obtained.     

Some new binary codes correcting asymmetric/unidirectional errors

The authors give a tabulation of the numbers of codewords in new binary codes with the asymmetric/unidirectional error-correcting capabilities of 3, 4, 5, 6 for lengths 14, 15, . . . , 23. The new codes have greater sizes than the known codes for 14⩽n⩽23 and 3⩽t⩽6     

Long-span optical FSK heterodyne single-filter detection transmission experiment using a phase-tunable DFB laser diode

High receiver sensitivity (?51.9 dBm) and long span (243 km) transmission expriments have been achieved with a 140 Mbit/s optical FSK heterodyne single-filter detection system, using a phase-tunable DFB laser diode as a transmitter. This has enabled direct FSK modulation without waveform distortion. Also, a 280 Mbit/s 204 km transmission experiment has been carried out successfully.