Breaking arcs are generated between a pair of Cu electrical contacts in a DC 42 V/10.5 A circuit, and the arc voltage, the arc current and the time-resolved arc spectral intensities near contact surfaces are simultaneously measured. The arc temperature is calculated from some spectral intensities emitted from Cu neutral atoms using the Boltzmann plot method. The arc temperatures near the cathode and anode surfaces are measured, and the following experimental results were obtained. (1) Time evolutions of the spectral intensities and the calculated arc temperature have similar characteristics. (2) The arc temperature near the anode surface is higher than that near the cathode surface, and the temperature fluctuation near the anode surface is larger than that near the cathode. (3) Just before arc extinction, the arc temperature near the cathode surface is almost constant for many breaking operations but the arc temperature near the anode surface varies.

Efficient real-time contents distribution services on the Internet are only possible by suppressing the influence of packet losses. One solution for UDP transmission is the use of Forward Error Correction (FEC) based on Reed-Solomon codes. However, a more efficient method is required since this causes the increase of network traffic and includes the weakness to burst packet losses. In this paper, we propose a data recovery method that generates redundant data with the combination of Reed-Solomon codes and convolution of neighboring blocks. We realize the small amount of redundancy and the high reliability in data transmission compared with using only Reed-Solomon codes in the environment that burst packet losses are occurred frequently. We implement proposal method into the network bridge and confirm its efficiency from the viewpoint of data reconstruction from burst packet losses.

In this paper, the separation of heat generation and heat transfer related to temperature rise of silver palladium contact was investigated experimentally in order to predict the temperature rise of contact by the use conditions such as voltage range between 25 to 40 V, current range between 3.2 to 5.0 A and silver palladium alloy (AgPd) materials. Firstly, relationship between temperature rise of contact and supply power was discussed. The effects of heat generation and heat transfer on temperature rise were separated and quantified by least squares method. Secondly, effects of durations and integral powers of bridge and arc on temperature rise were also discussed by changing supply power. Results show that the integral power of the bridge increases when supply power increases. As the supply power increases, integral power of arc also increases. The temperature rise is dominated by integral power of bridge. Remarkable difference of bridge duration can not be seen in the five materials (AgPd30, AgPd40, AgPd50, AgPd70 and Pd). The supply power is increased, arc duration gets longer. As weight percent of Pd content increases, the effect of supply power on arc duration becomes larger. Consequently, the integral power of arc increases. This study is a basic consideration to realize methods predicting temperature rise of contact.

This investigation proposes a modified equivalent circuit of single complementary split-ring resonator (CSRR) in planar transmission media and a dual-mode ring bandpass filter (BPF) that uses periodic CSRRs to suppress the spurious response. The proposed modified equivalent circuit consists of lumped elements that can be easily extracted from the measured S parameters. The proposed dual-mode ring BPF has exhibits a wide stopband characteristic owing to the bandgap resonant characteristic of CSRRs in the harmonic frequency of the dual-mode ring BPF. Good agreement with EM simulation and measurement is demonstrated.

Field assembly of optical connectors is demanded because of the wide use of optical fiber in telecommunications systems. We propose a new assembling techniques that enable us to assemble connectors anywhere quickly and cost effectively. The key points are an adhesive technique and a polishing technique. In this report, we focus mainly on our a new polishing machine, which is suitable for optical connector ends machining on-site. The machine which is small and light weight can finish optical connector ends easily in a short time with enough low cost.

A method which uses the moving time and the over travel time of contact to discover the characteristics of contact and the reliability of aerospace relay is proposed. The Gauss-Newton method and its improved form (Macalto method) are used to identify the nonlinear mathematical model of the parameter during armature initial moving period, which is from the coil is energized at a rated voltage to the moment the armature begins to move. The validity of the method is verified by results of actual experiments and analysis.

We propose an adaptive beamforming scheme for the combination of orthogonal frequency division multiplexing (OFDM) and adaptive antenna array. The combinational scheme is characterized by the sample matrix inverse (SMI) algorithm, frequency-to-time pilot transform and pre-FFT combination. For every OFDM block containing both data and pilot symbols, we transform the frequency-domain pilot symbols to the corresponding time-domain components. One of the obvious advantages of this transform is that the time interval of the antenna weight vector update can be reduced to only one OFDM sample interval, from one OFDM block interval of the conventional beamforming scheme in which the transform is not applied. This feature can greatly accelerate the convergence of SMI beamforming. The simulation results verify that the proposed beamforming scheme is capable of improving the convergence behavior significantly.

An active integrated antenna (AIA) oscillator consisting of an active circuit and planar antenna on the same substrate can be used as a high-performance, low-cost, small component for millimeter-to-sub-millimeter wave applications. We describe a highly extended, finite-difference-time-domain full-wave analysis method for designing AIA circuits precisely. It treats active devices as distributed elements. Using this method and 0.1-µm-gate InP-based HEMTs, we fabricated W-band AIA oscillators with an oscillation frequency of 111 GHz.

Experimental result and theoretical analysis are reported for bias-voltage dependence of oscillation frequency in resonant tunneling diodes (RTDs) integrated with slot antennas. Frequency change of 18 GHz is obtained experimentally for a device with the central oscillation frequency of 470 GHz. The observed frequency change is attributed to the bias-voltage dependence of the transit time of electrons across the RTD layers, which results in a voltage-dependent capacitance added to RTD. Theoretical analysis taking into account this transit time is in reasonable agreement with the observed results. Voltage-controlled RTD oscillators in the terahertz range are expected from the theoretical results. A structure suitable for large frequency change is also discussed briefly.

This letter proposes a peak power reduction method that optimizes sub-carrier phases of an OFDM signal. The proposed method doesn't require side information transmission and original signal regeneration, which are required in conventional peak power reduction methods with phase optimization, since the optimized phases are distributed as jitter around the original phases before optimization. The iterative PTS (partial transmit sequences) algorithm with a restricted phase control range is used for the jitter injection: the phase optimization process is repeated with widening the control range. A computer simulation is carried out to estimate the proposed method performance. The results show that the proposed method can reduce the peak power by 4 dB when the power penalty caused by phase jitter is only 0.2 dB.

For hybrid Multimedia-on-Demand (MoD) systems which support broadcast, batch and interactive services, the charging scheme employed plays an important role in the delivery of good service quality to users, while also determining the revenue generated for the service provider. In this letter a new charging scheme is proposed. This scheme provides the same quality of service to the users as previous charging schemes while providing higher revenue. Numerical results are presented to evaluate the performance of the new charging scheme in comparison with previous schemes.

Expressions are presented for the probability of target detection and the measurement accuracy of the detection, taking into account the effects of antenna beam-pointing error. Evaluation of these expressions requires numerical integration, which is computationally expensive. Approximate but analytic and efficient expressions are also presented. Numerical examples are given to present the relative accuracy of our analytic approximations.

To obtain large capacity, high quality mobile satellite communication systems in the future, we must use a multi-beam that can cope with extremely high levels of frequency reuse. This paper describes a novel resource allocation algorithm for multi-beam satellite communication systems that can dynamically adapt to maximum communication capacity without compromising quality. The algorithm combines two resource allocation schemes that enable it to contend with the ever-changing user distribution and inter-beam interference conditions. The first scheme optimizes the resources amongst beams. To minimize interference, the optimal constraint conditions are clarified when all clusters share and occupy the same bandwidth completely. These constraints are used in the optimization algorithm. The second scheme manages the various required resources and adapts them to the beam gain and interference levels at various user locations within a single beam. We propose a fixed power adaptive modulation scheme to obtain stable communications. This two-layered scheme can satisfactorily allocate multi-beam satellite resources to contend with the increasing communication capacity and still improve the quality.

A novel dual band transmitter module for 2.4 GHz and 5.8 GHz wireless LAN applications with adaptive digital predistortion linearization is presented. The module operates either as a power amplifier for 2.4 GHz or frequency doubler for 5.8 GHz band. Amplification gain is 12.9 dB at 2.4 GHz and multiplication gain is 3.3 dB at 5.8 GHz. At 2.4 GHz band, the second harmonic is about 36.5 dB lower than the fundamental, and the 2.9 GHz fundamental signal is 20.3 dB lower than the second harmonic output at 5.8 GHz operation. An adaptive digital predistortion scheme is proposed to linearize the 2.4 GHz amplifier, and to get the proper 5.8 GHz band wireless LAN signal. The 2.4 GHz amplifier with predistortion satisfies the ACPR mask requirement for the input 1 dB compression power of 5 dBm and the linearized frequency doubler shows 26 dB ACPR improvement at 11 MHz offset from center frequency by using the proposed predistortion linearization. The frequency doubler output spectrum with predistortion does meet the IEEE standard Tx mask.

In this letter, we present a simple way of estimating the integer frequency offset of orthogonal frequency division multiplexing (OFDM) system over a rapidly time-varying channel. By utilizing the channel responses of neighboring subcarriers within one pilot symbol, the frequency offset estimator is derived. We show by simulation that the proposed estimator can accurately estimate the integer frequency offset with reduced computational burden.

In an effort to reduce switch cost, we present the optimum numbers of tunable wavelength converters (TWCs) and internal wavelengths required for contention resolution of asynchronous and variable length packets, in the optical packet switch (OPS) with the shared fiber delay line (FDL) buffer. To optimize TWCs and internal wavelengths related to OPS design cost, we proposed a scheduling algorithm for the limited TWCs and internal wavelengths. For three TWC alternatives (not shared, partially shared, and fully shared cases), the optimum numbers of TWCs and internal wavelengths to guarantee minimum packet loss are evaluated to prevent resource waste. Under a given load, TWCs and internal wavelengths could be significantly reduced, guaranteeing the same packet loss as the performance of an OPS with full TWCs and internal wavelengths.

In this letter, a method estimating the intercell carrier frequency-offset (CFO) in orthogonal frequency division multiplexing (OFDM)-based cellular systems is proposed for the user's equipment (UE), especially at the cell boundary, in downlink channels. After describing a new method of deriving the intercell CFO from the signals received by adjacent base stations (BSs), we propose a cell-searching method using the estimated CFOs. It is shown by computer simulation that the proposed methods can uniquely estimate the intercell CFOs and identify the target BS with a high detection probability at the UE.

Natural, continuous tone images have a very important property of high correlation of adjacent pixels. Images which we wish to compress are usually non-stationary and can be reasonably modeled as smooth and textured areas separated by edges. This property has been successfully exploited in LOCO-I and CALIC by applying gradient based predictive coding as a major de-correlation tool. However, they only examine the horizontal and vertical gradients, and assume the local edge can only occur in these two directions. Their over-simplified assumptions hurt the robustness of the prediction in higher complex areas. In this paper, we propose an accurate gradient selective prediction (AGSP) algorithm which is designed to perform robustly around any type of image texture. Our method measures local texture information by comparison and selection of normalized scalar representation of the gradients in four directions. An adaptive predictor is formed based on the local gradient information and immediate causal pixels. Local texture properties are also exploited in the context modeling of the prediction error. The results we obtained on a test set of several standard images are encouraging. On the average, our method achieves a compression ratio significantly better than CALIC without noticeably increasing of computational complexity.

From the viewpoint of a low-power pipeline ADC design, a comparison between two conventional power reduction techniques is discussed. The comparison shows that the amplifier sharing technique has an advantage in terms of the power reduction effect. To confirm the advantage, a test chip of 10-bit 80-MSPS ADC using the amplifier sharing technique is fabricated. The test chip dissipates 55 mW at 80 MSPS (Mega Sample Per Second).

Switching characteristics such as wavelength dependency and phase dependency are investigated for our proposed switch which consists of waveguide-type Raman amplifiers and 3-dB couplers. As a result, the available range of wavelength and phase shift due to nonlinear effect are estimated about 20 nm around 1.55 µm and about 10 degrees, respectively.