Recently most of the singularities of the equivalent edge currents for flat plates were eliminated by the authors using the paths of most rapid phase variation. A unique direction on the plate was determined for given incidence and observer. This paper extends this method for arbitrary angle wedges and presents the new expressions of the equivalent edge currents. The resultant expressions are valid for any incidence and observation aspects and have no false singularities. Diffraction patterns and radar cross sections of 3-D objects composed of wedges are calculated by using these currents. They show good agreements with experimental data or the results by the other methods.

It often occurs in the acoustic environment that a specific signal is contaminated by the additional noise of non-Gaussian distribution type. In order to extract exactly the various statistical information of only specific signal from the observed noisy data, a stochastic signal processing by use of digital computer is essential. In this study, a stochastic method for estimating the probability function of the specific signal embedded in the additional noise is first theoretically proposed in a suitable form for the quantized level observation. Then, the effectiveness of the proposed method is experimentally confirmed by applying it to the observed data in the acoustic environment.

In power line SS communication system, since available frequency range is limited from 10 kHz to 450 kHz by the law, we can't transmit any components of lower and higher frequency regions. In this paper, we propose a method for improving bit error rate by using the PN sequence coded by the new channel code, FM-V5 code, instead of PE code to have correlation property in the coded PN sequence. Correlation property in the coded PN sequence makes us effectively use Viterbi decoding technique on the receiving side. To enhance correlation property more, we also examine to apply additionally partial response (PR) system, so called PRML system, on the receiving side. The results of computer simulation show the improvement of about 4.5 dB on SNR at bit error rate 10-5 by using FM-V5 code without PR system compared with PE code. In the case of FM-V5 code with PR(1, -1) system, we get the further improvement of about 11 dB on SNR at the same bit error rate 10-5 compared with PE code. As a result, our method can attain SNR improvement about 20 dB compared with conventional simple PN sequence, that is the conventional Direct Sequence/Spread Spectrum (DS/SS), method.

In this paper, a type hybrid ARQ scheme with Adaptive Forward Error Correction (ARQ/AFEC) using BCH codes is proposed and analyzed. The basic idea in the proposed type hybrid ARQ/AFEC scheme is to increase the error-correcting capability of BCH code according to channel state using incremental redundancy. The incremental redundancy is the remainder ai(x) of an information frame f(x) of length n divided by a minimum polynomial mi(x) of α2i-1, where α is a primitive element of finite field GF(2l). Let gi(x) be the product of mj(x) (j=1, 2, , i) and let ci(x) be the remainder of f(x) divided by gi(x). The polynomial ci(x) is obtained from the remainders ai(x) and ci-1(x) since mi(x)and gi-1 (x) are relatively prime. Since f(x) + ci(x) is divided by gi(x), f(x) + ci(x) is the codeword of an i-error-correcting BCH code when n2l-1. So, the errors less than or equal to i bits in f(x) can be corrected if ci(x) has no error.

The purpose of our research is to get further improvement in the performance of order statistic filters. The basic idea found in our research is the use of a robust median estimator to obtain median differential order information which the classes of order statistic filter required in order to sort the input signal in the filter window. In order to give the motivation for using a median estimator in the classes of order statistic filters, we derive theorems characterizing the median filters and prove them theoretically using the characteristic that the order statistic filter has the performance for a monotonic signal equivalent with the FIR linear filter. As an application of median operation, we propose and investigate the Median Differential Order Statistic Filter to reduce impulsive noise as well as Gaussian noise and regard it as a subclass of the Order Statistic Filter. Moreover, we introduce the piecewise linear function in the Median Differential Order Statistic Filter to improve performance in terms of edge preservation. We call it the Piecewise Linear Median Differential Order Statistic Filter. The effectiveness of proposed filters is verified theoretically by computing the output Mean Square Error of the filters in parts of edge signals, impulsive noise, small amplitude noise and their combination. Computer simulations also show that the proposed filter can improve the performance in both noise (small-amplitude Gaussian noise and impulsive noise) reduction and edge preservation for one-dimensional signals.

The effect of mesage-class dependent threshold-type scheduling on queueing delay and resequencing delay for the M/M/n queueing system is analyzed. We first derive the expressions for the state transition equations, mean queueing delay, resequencing delay and total delay for the M/M/n queueing system shared by C different message classes under a threshold-type scheduling in which the threshold values depend on the message class at the head of queue and the number of messages in the buffer. Next, the numerical calculation and the computer simulation are carried out for the queueing system with two servers. It is found that the message-class dependent threshold-type scheduling is effective to reduce the resequencing delay of some specific message class, which can not be attained under the conventional threshold-type scheduling, and thus, the proposed scheduling can satisfy the different requirements of the different message classes, such as minimizing only queueing delay or total delay including resequencing delay.

Subscriber network opticalization is the key issue for the next generation network. Fiber-optic systems have been limited to mainly big business applications, so far. Massive opticalization including home and small business customers remains the ultimate goal. Opticalization of the subscriber network needs an enormous investment and a long construction period. In order to achieve smooth evolution towards B-ISDN, the subscriber network must be effectively opticalized well in advance of full B-ISDN deployment. This paper presents the development concept of optical subscriber network. It also describes the design concept and configuration of fiber-optic subscriber systems. Deployment strategies and the developing technologies for the future subscriber network are also addressed.

This letter proposes an improvement of the equivalent source method in order to give an accurate solution for the scattering of an electromagnetic plane wave by a conducting cylinder with edges.

This paper first discusses the software reusability-based development process in a lifecycle and reusable objects modification process called differentiation. Next, the supporting environment is described. Both the method and the environment allow developers to carry out requirement definitions, specification and implementation in a reusable way. Some quantitative evaluations are given about how productivity and quality have been improved by using this method and environment, based on a number of case studies made on development projects. Reusability has been largely improved by differential specification, and adjustment method and a direct transformation capability.

A novel harmonic retrieval algorithm is proposed in this paper based on Hopfield's neural network. Frequencies can be retrieved with high accuracy and high resolution under low signal to noise ratio (SNR). Amplitudes and phases in harmonic signals can also be estimated roughly by an energy constrained linear projection approach as proposed in the algorithm. Only no less than 2q neurons are necessary in order to detect harmonic siglnals with q different frequencies, where q denotes the number of different frequencies in harmonic signals. Experimental simulations show fast convergence and stable solution in spite of low signal to noise ratio can be obtained using the proposed algorithm.

In this letter, it is clarified that the quantum noise properties of the linear amplification and locking amplification in the injection locked laser process are different. The noise property of the locking amplification is newly given.

In this paper, we analyze a photodetection process of new kind theoretically, which transforms a coherent state of light so as to lead to nonstandard property, namely, sub-Poissonian distribution of its output photoelectron during its photodetection process. The properties of the photoelectron distribution are studied used as preamplifiers of both direct-detection and homodyne detection cases.

A 1/2 frequency divider using resonant-tunneling hot electron transistors (RHETs) has been proposed and demonstrated. The circuit make the best use of negative differential conductance, a feature of RHETs, and contains one half transistors than used in conventional circuits. The RHETs were fabricated using self-aligned InGaAs RHETs and WSiN thin-film resistors on a single chip. The RHETs have an i-InGaAlAs/i-InGaAs collector barrier that improves the current gain at low collector-base voltages. Circuit operation was confirmed at 77 K.

Experimental results on the superconducting three-terminal devices Using Bi-system High-Tc Superconductors were reported. The VCJJ (Variabel critical-current-type Josephson junction devices) using the thermal effect (VCJJ) and a dual gate Josephson device of a new current-injection type are described. The basic technology and problems for high-Tc three-terminal devices are briefly discussed.

This study is concerned with modeling and analyzing a nonlinear elastomer impact phenomenon when a mass experiences a collision with the contact pad mounted on the underlying linear dynamic structure. The contact pad which consists of the viscoelastic elastomer is modeled here by a nonlinear contact stiffness and nonlinear contact damper. The underlying dynamic structure is measured by a Fourier spectral analyzer and its analytical form is utilized in modeling and analyzing the whole dynamic impact problem. The impact force profiles are predicted and analyzed in terms of pulse duration, time-to-peak force, and peak force. Finally, the damping mechanism and its hysteresis phenomena are also discussed.

In this letter, a generalized syndrome polynomial is proposed from which several decoding key-equations for Reed-Solomon codes can be derived systematically. These equations are always solved by the extended Euclidean algorithm.

This paper proposes a high resolution and fast frequency settling PLL synthesizer for frequency hopping radio communication equipment. The proposed synthesizer enables the carrier frequency to be changed within the duration of a burst signal and yields higher frequency resolution than the reference signal frequency. To reduce frequency settling time without degradation of frequency resolution and phase noise, this paper proposes a new phase and frequency preset (PEP) PLL synthesizer which employs a digital phase accumulator to generate high resolution reference signal. Experimental results show that the settling time of a prototype synthesizer is less than 300µs while spurious signals are suppressed by more than 55 dB. In comparison with conventional PLL synthesizers, the frequency settling time is reduced by 80%. Furthermore, the higher frequency resolution than the reference signal is successfully demonstrated. Therefore, the proposed PFP PLL synthesizer with the digital reference signal can achieve the output signal with high frequency resolution less than 1Hz.

Telecommunication services are accomplished by cooperative networks of widely distributed communication processes and service users. Those specifications are often modeled by a set of possible message sequences among cooperating processes and users. The distributed and cooperative nature of telecommunication services results in a wide variety of message sequences and makes it more difficult for service designers to design such telecommunication services. To mitigate the difficulty, we propose a design support system with MSRs (message sequence rules) as design knowledge. The system supports the following two design activities: (1) specification of a typical message sequence that corresponds to a service behavior in a successful case, and (2) specification of incidentally possible message sequences that involve service behaviors in successful and unsuccessful cases. For the former activity, the system interacts with designers and identifies the messages they give with MSRs to understand the context of the message sequence and suggest possible subsequent messages. For the latter activity, the system applies MSRs to the typical message sequence and reasons possible messages from/to relevant processes and users under every state to suggest incidentally possible message sequences. Accordingly, designers may be relieved of investigating a wide variety of service behaviors in successful and unsuccessful cases. The system capability is based on MSRs equivalent to reusable message sequence components. MSRs can be obtained through abstraction of implementation-dependent messages and decomposition of those sequences into temporal relations among messages. The rule acquisition method provides MSRs with the potential to generate a wide variety of message sequences. In order to verify rule applicability, we have experimentally designed three kinds of services and conducted an experimental rule application to those specifications. The experimental evaluation results indicate that applicability is fairly high.

Generalized telegraphist's equations for waveguides are frequently used for analyzing fields in tapered rectangular waveguides. However, the telegraphist's equations do not give exact fields in E-plane tapers of the rectangular waveguides. In this letter, the new telegraphist's equations are shown, and the equations give the fields which exactly satisfy Maxwell's equations and the boundary conditions for the E-plane taper of the waveguide.

This letter proposes an active reflector for calibrating a synthetic aperture radar (SAR), in which the frequency of a received SAR signal is shifted by a certain amount and then it is retransmitted to the SAR. The frequency shift causes a shift of the reflector SAR image in an azimuth direction relative to its background. This function would allow to enhance a signal-to-clutter ratio of the reflector image by moving it onto a radiometrically dark background, and hence it would be of value for SAR calibration even in a narrow test site. The theory, design and development are described briefly.