The phase and frequency commands of a rotating radar system, that utilizes the frequency scanning and phase shifters to steer the beam in the azimuth and elevation directions, respectively, are derived in terms of the angles of the ground based coordinate system. The frequency equation derived is approximated to a simple form to reduce the calculation time for real time multi-function radar systems. It is shown that the approximate frequency commands are in good agreement with the exact ones if the range of the azimuth scanning is not too wide.

Macroscopic method for quantization of the evanescent fields brought about by total reflection is presented. Here, a semi-infinite space is assumed to be filled with a transparent dispersive dielectric with dielectric constant ε(ω) to the left of the plane z = 0, and be empty to the right of the plane. The wave is assumed to be incident from the left, and so the whole field is composed of the triplet of incident, reflected, and transmitted waves labeled by a continuous wave vector index. The transmitted wave in free space may be evanescent. The triplet is shown exactly without using slowly varying field approximation in dispersive medium to form orthogonal mode for different wave vectors, which provides the basis for the quantization of the triplet with taken into account of medium dispersion. The exact orthogonal relation reduces to the well known one if the dielectric is nondispersive, ε/ω = 0. By using the field expansion in terms of the orthogonal triplet modes, the total field energy is found to be the sum of the energies of independent harmonic oscillators. A discussion is also made on the wave momentum of evanescent field.

In this paper, a two-dimensional (2-D) binary-valued (BV) lapped transform (LT) is proposed. The proposed LT has basis images which take only BV elements and satisfies the axial-symmetric (AS) property. In one dimension, there is no 2-point LT with the symmetric basis vectors, and the property is achieved only with the non-overlapping basis which the Hadamard transform (HT) has. Hence, in two dimension, there is no 22-point separable ASLT, and only 2-D HT can be the 22-point separable AS orthogonal transform. By taking non-separable BV basis images, this paper shows that a 22-point ASLT can be obtained. Since the proposed LT is similar to HT, it is referred to as the lapped Hadamard transform (LHT). LHT of larger size is shown to be provided with a tree structure. In addition, LHT is shown to be efficiently implemented by a lattice structure.

An efficient algorithm is proposed to identify the active users and extracting their respective timing information in asynchronous direct sequence CDMA (DS-CDMA) communication system over Rayleigh fading channel. The joint identification and timing estimation algorithm is derived by performing discrete Fourier transform (DFT) on the observation vector and exploiting the uniqueness and nullity characteristics of the root-MUSIC test polynomial. The root-MUSIC based algorithm is shown to be asymptotically near-far resistant. Compared to the maximum a posteriori (MAP) or maximum likelihood (ML) based multiuser timing estimator, the complexity is greatly reduced by separating the multi-dimensional optimization problem into several polynomial rooting problems. Moreover, we characterize the dependence of system performance with respect to signature sequence length, number of active users, window size, desired user's signal-to-noise ratio (SNR) and crosscorrelation property of the code structure. The analytical results reveal that under the uncorrelated Rayleigh fading model, the root-MUSIC timing estimator tends to achieve the Cramer-Rao lower bound (CRLB) at interesting signature sequence length and desired user's SNR.

To improve speech coding quality, in particular, the long-term dependency prediction characteristics, we propose a new nonlinear predictor, i. e. , a fully connected recurrent neural network (FCRNN) where the hidden units have feedbacks not only from themselves but also from the output unit. The comparison of the capabilities of the FCRNN with conventional predictors shows that the former has less prediction error than the latter. We apply this FCRNN instead of the previously proposed recurrent neural networks in the code-excited predictive speech coding system (i. e. , CELP) and shows that our system (FCRNN) requires less bit rate/frame and improves the performance for speech coding.

Well-defined wavelength distributed feedback laser diodes (DFB-LDs) are required in WDM network systems. Since the EDFA gain bands have been expanded, even more wavelengths are needed for large-capacity dense-WDM transmission systems. A precisely pitch-controlled Bragg grating fabricated by electron beam (EB) lithography is very attractive for realizing these DFB-LDs. This paper describes this precise pitch- and phase-controlled grating delineated by a novel method called weighted-dose allocation variable-pitch EB-lithography (WAVE). In this method, an EB-dose profile for the grating is precisely controlled by a combination of the allocation and weighting of multiple exposures. This enables us to fabricate a precise fixed-pitch grating as well as a flexible grating with a continuously chirped structure. The stitching error at the exposure field boundary, the grating pitch, and the phase shift were evaluated by using a moire pattern generated by superimposing the microscope raster scan and the grating on a wafer. We also estimated amounts of the stitching errors from fabricated and calculated lasing characteristics, and clarified that the affect of the errors on the single-mode stability of LDs is negligible. Precise wavelength controlled λ/4 phase shifted DFB-LDs were successfully demonstrated as a result of both the WAVE method and the highly uniform MOVPE crystal growth.

In this paper, a novel method is proposed for designing two channel biorthogonal filter banks with general IIR filters, which satisfy both the perfect reconstruction and causal stable conditions. Since the proposed filter banks are structurally perfect reconstruction implementation, the perfect reconstruction property is still preserved even when all filter coefficients are quantized. The proposed design method is based on the formulation of a generalized eigenvalue problem by using Remez multiple exchange algorithm. Then, the filter coefficients can be computed by solving the eigenvalue problem, and the optimal solution is easily obtained through a few iterations. One design example is presented to demonstrate the effectiveness of the proposed method.

In this paper, we propose two new pipelined adaptive digital filter architectures. The architectures are based on an equivalent expression of the least mean square (LMS) algorithm. It is shown that one of the proposed architectures achieves the minimum output latency, or zero without affecting the convergence characteristics. We also show that, by increasing the output latency be one, the other architecture can be obtained which has a shorter critical path.

This paper presents an integrated network configuration of wired and wireless access systems for nomadic computing and discusses the virtual LAN on a wireless access system. Furthermore, different types of ad hoc networks are summarized to delineate nomadic computing styles. In terms of user mobility, the integrated network provides a seamless connection environment, so a user can move between wireless and wired networks without dropping data communication sessions. This function is critical for nomadic computing users. By defining the integrated network and employing a virtual LAN, a nomadic computing environment can be realized. This paper reviews the key issues to realize integrated networks. They are mobile management including mobile IP, virtual IP and Logical Office, a high performance MAC, and security control.

This paper studies a set of lip synchronization mechanisms for heterogeneous network environments. The set consists of four schemes, types 0 through 3, which are classified into the single-stream approach and the multi-stream approach. Types 0 and 1 belong to the single-stream approach, which interleaves voice and video to form a single transport stream for transmission. On the other hand, types 2 and 3, both of which are the multi-stream approach, set up separate transport streams for the individual media streams. Types 0 and 2 do not exert synchronization control at the destination, while types 1 and 3 do. We first discuss the features of each type in terms of networks intended for use, required synchronization quality of each medium, physical locations of media sources and implementation complexity. Then, a synchronization algorithm, which is referred to as the virtual-time rendering (VTR) algorithm, is specified for stored media; MPEG video and voice are considered in this paper. We implemented the four types on an ATM LAN and on an interconnected ATM-wireless LAN under the TCP protocol. The mean square error of synchronization, total pause time, throughput and total output time were measured in each of the two networks. We compare the measured performance among the four types to find out which one is the most suitable for a given condition of the underlying communication network and traffic.

A password authentication method PERM has been developed for application to e-mail forwarding. This method is suitable for communications in insecure network environments such as the Internet. In particular, it can be adapted to Internet appliances and Java applets which have limited performance. The PERM method does not require password resettings and enables high-speed authentication processing with a small-sized program. Moreover, it does not use facilities or mechanisms for generating random numbers and writing them into and reading them out of an IC card or similar storage medium on the user's side.

An important issue in accelerating the introduction of ATM networks is to offer more convenient access to the customer and a more efficient ATM system architecture. Regarding the first point, ATM network customers are currently inconvenienced by the need to declare traffic parameters, such as peak and average cell rates to the network provider before using the network. However, it is difficult for a customer to predict traffic parameters. This paper proposes a new ATM system with a dynamic bandwidth estimation and allocation scheme. This eliminates the need for traffic parameter declaration, and realizes more convenient ATM service. The proposed ATM system is a ring network. Bandwidth estimation is carried out by the "Network Server" located on the ring network. The estimation is achieved by observing the parameters closely related to media access control (MAC) protocols of LAN/MAN systems. Based on an estimation of customer traffic, the "Network Server" effectively allocates the bandwidth to each customer. This realizes a more efficient ATM network.

To expand signal wavelength bandwidth in long-haul, large-capacity WDM transmission systems, we investigated gain-equalizers (GEQs) for Erbium doped fiber amplifiers (EDFAs). We applied GEQs using Mach-Zehnder type filters with two different free-spectral-ranges (FSRs) to accurately compensate for the EDFAs gain-wavelength characteristics. The 1st GEQ with a longer FSR was the main GEQ to compensate for the overall gain-wavelength characteristics, and the 2nd GEQ with a shorter FSR was the secondary GEQ to compensate for the resultant gain undulation after the 1st GEQ. The 2nd GEQ had low maximum loss and long period of equalization-spacing compared to the 1st GEQ. We designed that the FSR for the 1st GEQ was twice the signal wavelength bandwidth, and the FSR for the 2nd GEQ was two thirds of the signal wavelength bandwidth. To compensate for the asymmetry in the EDFAs gain-wavelength characteristics, we designed that the 2nd GEQ minimum-loss wavelength was shorter than the 1st GEQ maximum-loss wavelength. Using a circulating loop with a 21-EDFA chain, we confirmed the signal wavelength bandwidth expanded by the above GEQs. We also investigated the trade-off relationship between the signal wavelength bandwidth and the optical signal-to-noise ratio, as the parameter of the number of the 1st GEQ inserted in the EDFAs chain. The achieved signal wavelength bandwidth after 10,000-km transmission was 12 nm. We successfully transmitted 170 Gbit/s (325. 332 Gbit/s) WDM signals over 9,879 km employing high alumina codoped EDFAs and Mach-Zehnder type filters with long FSRs.

The Multiwavelength Optical Networking (MONET) program consists of a consortium of industrial partners, working together with the intent to demonstrate the key capabilities needed for configurable WDM networks. This involves integrating WDM technologies with optical switching technologies to provide a managed, high capacity, national scale WDM server layer to transport optical signals transparently across multiple interworking subnetworks.

A combined mode-matching and moment method is proposed to calculate the capacitance matrix of wedge-supported cylindrical microstrip lines with an indented ground. Each indent is modeled as a multilayered medium in which the potential distribution is systematically derived by defining reflection matrices. An integral equation is derived in terms of the charge distribution on the strip surfaces. Galerkin's method is then applied to solve the integral equation for the charge distribution. The effects of strip width, strip separation, indent depth, and indent shape are analyzed.

2-pole band-pass filters (BPFs) with tap-excitation are prepared by using high temperature superconductors (HTS). The possibility of realizing superconducting coplanar filters with attenuation poles is revealed.

In this work, we give a true concurrency semantics for FIFO-nets, that are Petri nets in which places behave as queues, tokens take values in a finite alphabet and the firing of a transition depends on sequences on the alphabet. We introduce fn-processes to represent the concurrent behavior of a FIFO-net N during a sequence of transition firings. Fn-processes are modeled by a mapping from a simple FIFO-net without queue sharing and cycles, named FIFO-occurrence net, to N. Moreover, the relation among the firings expressed by the FIFO-occurrence net has been enriched by an ordering relation among the elements of the FIFO-occurrence net representing values entered into a same queue of N. We give a way to build fn-processes step by step in correspondance with a sequence of transition firings and the fn-processes operationally built are all those abstractly defined. The FIFO-occurrence nets of fn-processes have some interesting properties; for example, such nets are always discrete and, consequently, there is at least a transition sequence corresponding to each fn-process.

Video-on-Demand (VOD)servers are becoming feasible. These servers are a building component in a heterogeneous multimedia environment but have voluminous data to store and manage. If only disk-based secondary storage systems are used to store and manage this huge amount of data the system cost would be extensively high. A tape-based tertiary storage system seems to be a reasonable solution to lowering the cost of storage and management of this continuous data. However, the usage of a tertiary storage system to store large continuous data introduces several issues. These are mainly the replacement policy on disks, the decomposition and the placement of continuous data chunks on tapes, and the scheduling of multiple requests for materializing objects from tapes to disks. In this paper we address these issues and we propose solutions based on some heuristics we experimented in a simulator.

An optical communications technology roadmap leading up to the second decade of the 21st century has been investigated to provide a future vision of the optoelectronic technology in 15 to 20 years. The process whereby technology may progress toward the realization of the vision is indicated. A transmission rate of 100 Mbps for homes and a rate of 5 Tbps for the backbone network will be required in the first decade of the 21 century. Two technology roadmaps for public and business communications networks are discussed. It is concluded both WDM and TDM technology will be required to realize such an ultra-high capacity transmission. Technical tasks for various optical devices are investigated in detail.

The results of experiments on the effect of the height and diameter of the cup on cup microstrip antennas are presented. The results show that the optimum height of the cup for the narrowest beamwidth and the highest gain is about 1/3 λ, and that the beamwidth decreases and the gain increases as the diameter of the cup increases.