The energy conservation law and the optical theorem in the grating theory are discussed: the energy conservation law states that the incident energy is equal to the sum of diffracted energies and the optical theorem means that the diffraction takes place at the loss of the specularly reflection amplitude. A mathematical relation between the optical theorem and the energy conservation law is given. Some numerical examples are given for a TM plane wave diffraction by a sinusoidal surface.

This paper deals with the wave scattering from a periodic surface with finite extent. Modifying a spectral formalism, we find that the spectral amplitude of the scattered wave can be determined by the surface field on only the corrugated part of the surface. The surface field on such a corrugated part is then expanded into Fourier series with unknown Fourier coefficients. A matrix equation for the Fourier coefficients is obtained and is solved numerically for a sinusoidally corrugated surface. Then, the angular distribution of the scattering, the relative power of each diffraction beam and the optical theorem are calculated and illustrated in figures. Also, the relative powers of diffraction are calculated against the angle of incidence for a periodic surface with infinite extent. By comparing a finite periodic case with an infinite periodic case, it is pointed out that relative powers of diffraction beam are much similar in these of diffraction for the infinite periodic case.

This paper presents design of spreading codes for asynchronous DS-CDMA systems. We generate maximal-period sequences with negative auto-correlations based on one-dimensional maps with finite bits whose shapes are similar to piecewise linear chaotic maps. We propose an efficient search algorithm to find such maximal-period sequences. This algorithm makes it possible to find many kinds of maximal-period sequences with sufficiently long period for practical CDMA applications. We also report that maximal-period sequences can outperform conventional Gold sequences in terms of bit error rate (BER) in asynchronous DS-CDMA systems.

In transient analyzing of a crosstalk, the crosstalk waveform can be obtained with a commercial simulator such as SPICE simulation or FDTD (Finite Difference Time Domain) simulation. In case of using a simple model, a CMOS-IC load is considered as a constant capacitance load in crosstalk simulation. However, the semiconductor devices, such as CMOS-IC, have a characteristic of nonlinear impedance depending on the input voltage. We measured the far-end crosstalk of two parallel microstrip lines for a CMOS inverter (74HC04) load by changing the magnitude of the input step voltage. As the result, we found that the far-end crosstalk for the CMOS inverter load dose not necessarily depend on the input capacitance of the CMOS inverter.

The power dissipation tolerances for InP/ InGaAs uni-travelling-carrier photodiodes (UTC-PDs) and pin-PDs under high power optical inputs are compared. Catastrophic failures occur at constant power dissipations of 240 and 160mW for the UTC-PDs and pin-PDs, respectively. Scanning electron microscope observations confirm that the areas of destruction are located in the high electric-field region in the depletion layer.

We will present a novel core mode blocker fabricated with hydrogen loaded Ge-B co-doped fiber exposed to the electric arc discharge using local heat exposure. Tunable bandpass filter based on cascaded LPFGs with a core mode blocker inserted between the LPFGs will be also described. The characteristics are: 6.5-nm bandwidth, 30-nm tuning range, and 15-dB dynamic range, respectively. It can be very useful for application to wavelength stabilization and physical sensors.

A blind source separation problem in a solicitations context is addressed. The mixture stems from several telecommunication signals, the symbol periods of which are unknown and possibly different. Cost functions are introduced, the optimization of which achieves the equalization for a user, i.e. estimation of the symbol period and the associated sequence of symbols. The method is iterated by implementing a deflation. The theoretical results are validated by simulations.

Two types of p-i-n diode devices, namely an amplitude shift keying switch and a phase shift keying switch, were developed by using an NRD guide at 77 GHz. In order to apply these devices to radar systems, an SPDT switch with a low insertion loss of less than 2.5 dB and a high isolation of more than 25 dB was fabricated by using the former switch. Moreover, a BPSK modulator, composed of the latter switch together with a circulator and a ceramic resonator loaded band-pass filter, was designed and evaluated for use in spread spectrum radar systems in this frequency range.

We propose a new multiple access communication system based on finite field wavelet spread signature (FFWSS). In addition to the function of frequency diversity and multiple access, which are typically provided by traditional spreading codes, the FFWSS spreads data symbols in time, resulting in robustness against frequency selective slow fading. Using the FFWSS to spread a data symbol so that it is overlapped with neighboring symbols, a FFWSS-CDMA system is developed. It is observed that the ratio of the maximum nontrivial value of periodic correlation function to the code length of FFWSS is the same as that of a Sidelnikov sequence. Using RAKE-based receivers, simulation results show that the proposed FFWSS-CDMA system yields lower bit error rate (BER) than conventional DS-CDMA and MT-CDMA systems in multipath fading channels.

Harmonic distortions of a recently developed lightweight film-type ESPAR (Electronically Steerable Passive Array Radiator) antenna are investigated experimentally. These distortions arise from the nonlinearity of the varactor diodes that are directly integrated with the parasitic radiator elements to control the antenna's radiation pattern. A reactive-near-field measurement technique that employs low-interference probes in an ultra-small anechoic box is used to reduce experimental time and cost. An anti-series varactor pair is introduced and compared with the conventional single varactor. Consequently, an ESPAR antenna equipped with the anti-series varactor pair exhibits remarkable suppression of nonlinear distortion. In particular, the second- and the third-order harmonic is reduced by approximately 20 dB and 12 dB from the level of a single varactor type ESPAR antenna, respectively.

The UCHT (Unified Complex Hadamard Transform) has been proposed as a new family of spreading sequences for DS-SSMA systems recently. In this Letter, the periodic autocorrelation (PAC) properties of the Unified Complex Hadamard Transform (UCHT) sequences are analyzed. Upper bounds for the out-of-phase PAC are derived for two groups of the UCHT sequences, namely the HSP-UCHT and the NHSP-UCHT sequences (the later is a more general representation of the well-known Walsh-Hadamard (WH) sequences). A comparison of the two bounds is performed. It turns out that the HSP-UCHT sequences have a lower upper bound for the out-of-phase PAC. This makes the HSP-UCHT sequences more effective than the WH sequences in combating multipath effect for DS-SSMA systems.

This paper deals with a mathematical formulation of the scattering from a periodic surface with finite extent. In a previous paper the scattered wave was shown to be represented by an extended Floquet form by use of the periodic nature of the surface. This paper gives a new interpretation of the extended Floquet form, which is understood as a sum of diffraction beams with diffraction orders. Then, the power flow of each diffraction beam and the relative power of diffraction are introduced. Next, on the basis of a physical assumption such that the wave scattering takes place only from the corrugated part of the surface, the amplitude functions are represented by the sampling theorem with unknown sample sequence. From the Dirichlet boundary condition, an equation for the sample sequence is derived and solved numerically to calculate the scattering cross section and optical theorem. Discussions are given on a hypothesis such that the relative power of diffracted beam becomes almost independent of the width of surface corrugation.

A debug system for heterogeneous multiple processors in a single chip has been developed. The system consists of the debug interface circuit integrated on the chip, the interface circuit board between the chip and PC, and the debug software implemented on a PC. This debug system has been designed for a multimedia communication processor, which includes an original video processor core, a RISC processor, and a DSP. The RISC processor controls the Video Processing Unit that includes an original video processor and other hardware functions. While in debug mode, the external debugger can control the Video Processing Unit in the same manner as the RISC processor. The JTAG based interface circuit contains registers for bus transaction for command, address, and data to be written, etc. and a bus transaction sequencer. In fact, this system can realize the same bus transaction control as the RISC processor's. By applying proposed debug system, simultaneous debug of the RISC Processing Unit and the Video Processing Unit can be realized. This allows problems to be investigated more quickly and the total time required for debugging is efficiently reduced. Without this technology an estimated 19 weeks is required to debug the chip, whereas use of this technology allowed debugging to be completed in 9 weeks.

Carrying IP traffic over connection-oriented networks requires the use of bandwidth on demand schemes at gateways or network interfaces. A new virtual queue occupancy, which is more accurate than the classical one, is being proposed for IP/SONET bandwidth on demand. Based on the virtual queue occupancy, two enhanced periodic approaches for lossless services, LAVQ and LAVQL, are simulated and evaluated. Simulations show that LAVQ outperforms its counterpart LAQ in terms of bandwidth utilization. By curbing the queue occupancy fluctuation, LAVQL further promotes bandwidth utilization and conceals the influence of the system latency on delay jitter as well.

A quasi-periodic signal is a periodic signal with period and amplitude variations. Several physiological signals, including the electrocardiogram (ECG), can be treated as quasi-periodic. Vector quantization (VQ) is a valuable and universal tool for signal compression. However, compressing quasi-periodic signals using VQ presents several problems. First, a pre-trained codebook has little adaptation to signal variations, resulting in no quality control of reconstructed signals. Secondly, the periodicity of the signal causes data redundancy in the codebook, where many codevectors are highly correlated. These two problems are solved by the proposed codebook replenishment VQ (CRVQ) scheme based on a bar-shaped (BS) codebook structure. In the CRVQ, codevectors can be updated online according to signal variations, and the quality of reconstructed signals can be specified. With the BS codebook structure, the codebook redundancy is reduced significantly and great codebook storage space is saved; moreover variable-dimension (VD) codevectors can be used to minimize the coding bit rate subject to a distortion constraint. The theoretic rationale and implementation scheme of the VD-CRVQ is given. The ECG data from the MIT/BIH arrhythmic database are tested, and the result is substantially better than that of using other VQ compression methods.

We proposed the conduction mechanism of organic light-emitting diode (OLED) using a one-dimensional discontinuous model. We assumed that each emitting molecule corresponds to a hopping site according to the actual charge transfer between adjacent molecules. Both carrier mobility of Alq3 and barrier heights for each carrier were derived from experimental data. We calculate transient behavior of carrier, field, and exciton distribution. Both carrier injections assumed the Schottky injection. In the previous results, when we assumed that calculated current density fit the experimental one in the current density field curve, calculated light-emission intensity did not fit the experimental one in the light-emission field curve. Furthermore, the slope of the calculated light emission-field curve is too small to fit the experimental one. In the previous study, hopping distance was assumed to be 1 nm. In this study, it is assumed to be 1.7 nm. We consider that field dependence of electron injection is too weak to explain only the Schottky emission. When the electron injection is assumed to be both Schottky emission and Fowler-Nordheim emission calculated light-emission field as well as the current-density field curves were fit to the curve of each experimental characteristics.

Organic light emitting diodes (OLEDs) containing nanostructured cathode buffer layers were fabricated, and their electrical and emitting properties were investigated. The OLEDs have an ITO anode/CuPc/TPD/Alq3/buffer layer/Al cathode structure with the buffer layers made from nanostructured alternating layers Alq3 and Al. The driving voltage and the efficiency of the devices were improved by insertion of the buffer layer. It was estimated that some modulations of the Schottky barrier at the Alq3 and the Al cathode interface were induced due to the insertion of the buffer layer and it caused an enhancement of electron injection from the Al cathode.

Nonlinear feedback shift registers (NFSRs), which can generate maximal-period sequences called de Bruijn sequences, are regarded as one-dimensional maps with finite bits by observing states of the registers at each time. Such one-dimensional maps are similar to the Bernoulli map which is a famous chaotic map. This implies that an NFSR is one of finite-word-length approximations to the Bernoulli map. Inversely, constructing such one-dimensional maps with finite bits based on other chaotic maps, we can design new types of NFSRs, called extended NFSRs, which can generate new maximal-period sequences. We design such extended NFSRs based on some well-known chaotic maps, which gives a new concept in sequence design. Some properties of maximal-period sequences generated by such NFSRs are investigated and discussed.

Optical disk systems have been used in a wide range of applications and the performance of these systems has been improving rapidly. The optical integration is one of the important technologies of the progress of the optical pickup head in the system. It can make the optical pickup head miniature, light sized, ease to assemble, cost reduced and reliable during long time operation. In this paper, at first, merits and features of the optical integration for optical disk systems are briefly reviewed. Then, our activities on the development of the various hybrid-integrated optical devices, "Laser Couplers" are reported. Especially, the most recent results on the "Two-wavelength-beam Laser Coupler," are described in detail. It has two-wavelength laser emission/detection functions and easily realizes an ultimate solution of the optical pickup head for the DVD/CD system, now being used in "PlayStaion2. " To simplify the structure and the fabrication of this device, a new monolithic-integrated two-wavelength laser diode, called a visible and infrared laser diode, has been developed, which can be easily fabricated using only two steps of metal organic chemical vapor deposition. The structures and characteristics of this device are reported. Lastly, other recent technologies of the optical integration, including monolithically integration, near field optics and so on, are reviewed.

We investigate a method to suppress the polarization-dependent loss (PDL) of long-period fiber gratings (LPFGs). We study the origins of the PDL and propose an azimuthally isotropic UV exposure to suppress the UV-induced birefringence and to realize low-PDL LPFGs. By using this technique and a low birefringent fiber together, the PDL of LPFGs can be reduced to a sufficiently low level required in high performance communication systems. Moreover, the validity of our theoretical modeling is confirmed by the experimental results.