LiNbO3 optical modulators for band-operation with a resonant modulating electrode are investigated in this paper. We propose an asymmetric resonant structure consisting of two arms of modulating electrodes, where one arm is open-ended and the other arm is short-ended. The voltage standingwave was enhanced by the resonance of the electrodes, so that effective optical modulation was achieved, while the length of the modulating electrode was much shorter than the conventional travelingwave-type electrodes. The optical response at 6.2 GHz of a resonant modulator designed by maximizing the normalized induced phase was 4.94 of the response at dc with a non-resonant modulator.

In this study, synchronization phenomena in chaotic oscillators coupled by a transmission line are investigated. In particular investigation using real circuits is done for the first time. It is confirmed that the chaotic subsystems synchronize, although signals propagating along the transmission line are affected by the time delay. Further the period-doubling bifurcation with varying the time delay and anti-phase synchronization phenomena are observed in our circuit model. Also the voltage distribution of transmission line is simulated in order to investigate whether the current flowing through the transmission line is constant or not. It is found that the subsystems synchronize although the current through the transmission line keeps on varying.

The boundary integral equation (BIE) on interior walls with surface impedance conditions is implemented to the iterative physical optics method and how to treat the singularities involved in the BIE of an impedance cavity is described. Singular integrals over a rectangular region can be represented by simple elementary functions.

The efficiency-fractional bandwidth product (EB), which is expressed as a ratio of the radiation resistance to the absolute value of the input reactance of an antenna, is used as a performance criterion for small dielectric loaded monopole antennas (DLMAs). The dependence of the EB on the permittivity of the dielectric loading (i.e., the electrical volume) is experimentally and numerically investigated for the first time in antenna research. As a result, it is found that the EBs of the some DLMAs are enhanced over a bare monopole antenna and an EB characteristic curve has a maximum point. This result suggests the presence of the optimum electrical volume for the dielectric loading in order to obtain the best EB performance. A general reason for the existence of the peak value is also explained using a mathematical deduction. Finally the system EB, which is an efficiency-fractional bandwidth product of the DLMA with a practical matching circuit, is defined and its dependence on the relative permittivity is illustrated. Consequently, the existence of the peak value is also confirmed for the system EBs. In addition, it is demonstrated that the enhancement of the system EB is mainly due to the enhancement in the efficiency of the antenna system.

The diffraction of a plane electromagnetic wave by an impedance wedge whose boundary is described in terms of the skew coordinate systems is treated by using the Wiener-Hopf technique. The problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are then solved by using a factorization and decomposition procedure and introducing appropriate functions to satisfy the edge condition. The exact solution is expressed through the Maliuzhinets functions. By deforming the integration path of the Fourier inverse transform, which expresses the scattered field, the expressions of the reflected field, diffracted field and the surface wave are obtained. The numerical examples for these fields are given and the characteristics of the surface wave are discussed.

This report describes an acceleration technique to synthesize time-domain macromodels of interconnects using FDTD method. In FDTD calculation, the characteristic impedance of the interconnect is inserted into every terminal in order to damp quickly the transient waveforms. Additionally, an efficient technique for analyzing the macromodels is proposed. We demonstrate the efficiency of this method with examples.

Recently, antenna selection diversity has been widely used for hand-held phones to overcome a fading problem. A monopole antenna (MPA) and an inverted-F antenna (IFA) are the typical antennas used for this purpose. However, strong mutual coupling generally appears between these two antennas and often makes the diversity antenna design difficult. In particular, in the case that the MPA is unselected antenna the mutual coupling can be minimized using the open terminating impedance. On the other hand, in the case that the IFA is unselected antenna the terminating impedance, which can minimize the mutual coupling, has not been clarified. This paper presents a novel analytical method for optimizing the terminating impedance of the IFA. The method exploits the Z-matrix, and the final expression of the terminating impedance is expressed by self- and mutual-impedance. The numerical and experimental results confirm that the proposed optimization method is effective for minimizing the mutual coupling.

An electromagnetic wave scattering by a material loaded rectangular trough on a ground plane is approximately analyzed by using standard impedance boundary condition (SIBC). The validity of the derived approximate solution is examined by comparing with the rigorous one not only for the oblique incidence but also for the variation of both the filled material's parameters and the trough dimension. An applicability condition has been derived here for this trough structure.

We present here a study on the propagation characteristics of two-dimensional periodic structures. The method of mode matching is employed to formulate the boundary-value problem in an exact fashion, and a perturbation analysis is carried out to explain the wave phenomena associated with photonic band gap structures. The dispersion curves of 2D periodic medium and 2D periodic impedance surface are investigated in detail.

A simple method for diagnosing noise immunity of printed circuit boards (PCBs) by the bulk current injection (BCI) test was proposed, which can contribute to the PCB trace designs for common-mode noise. A grading index, which is defined as the ratio of the stray capacitances with and without critical IC of malfunction, was introduced to distinguish the PCB susceptible to the common-mode noise. This proposed method was validated experimentally using four PCBs with the same circuit but different trace design. It was observed that the noise immunity of PCBs had a good correlation with the values of these grading indices.

In this paper, the suppression of induced voltage on a printed wiring board through impedance loading by inserting impedance devices such as ferrite beads is focused on. How the suppression effect changes according to the insertion position of such devices is also investigated. Electromagnetic-field simulations were used to determine the distribution of voltage and current induced in wiring when a printed wiring board is exposed to an external electromagnetic field. Then, on the basis of these distributions, electromagnetic-field simulations were performed, and experiments were conducted to investigate the relationship between the insertion position of impedance devices and their suppression effect. It was verified that induced voltage can be large when a mismatch occurs between the impedance at the two ends of printed wiring, and that the suppression effect can differ significantly according to where an impedance device is inserted. A large effect was obtained by inserting an impedance device at a point 1/4 wavelength in distance from the end of a wire where voltage is being induced. In addition, comparing the use of resistors with the use of chip ferrite beads as impedance devices revealed similar tendencies in both. The above behavior was confirmed by numerical analysis.

This study is to clear how the impedance and the current of a simple printed line model involve to the near field electromagnetic noise radiation, by computer simulation and experiment. Frequency characteristics of the impedance and the current of the printed line and the near field noise are considered, from low to high frequency components. The model size 225 60 0.51 mm3, length of the line is 185 5 mm2 and 1 kΩ termination resistance is connected as non-matching load. FDTD method is used to calculate the impedance, the current waveform and the near field noise. Measurements of the line impedance and the near field noise spectrum by clock pulse are compared with simulations. It is cleared that using FDTD method, the characteristic of impedance of the printed line model, the current waveform, and the near field noise can be calculated at the same simulator. As results, from calculation and measurement, the near field noise has a relationship with impedance of printed line model. Emission at frequency less than 200 MHz, which is near the wavelength of λ/4, is observed at significant intensity. So, it is suggested that near field noise emission should be discussed from low to high frequency and analysis of the characteristics of the printed line and magnetic near field noise using FDTD method and measurement is useful to basic examination of complex PCB models.

It is not rare case that a floated metal plate exists nearby high speed circuit traces. Heatsink placed on a IC chip nearby circuit traces, metal enclosure or circuit traces in a compact designed product may be a good example. It may be also seen such structure for a shield box and circuit traces confined. It is generally known that such metal plate as placing nearby circuit trace may change circuit trace parameters and then resonance frequency associated with the circuit trace. In this study, we clarified resonance frequency variation with comprehensive observation of input impedance of microstrip line that is an essential model of circuit traces on a printed circuit board. Since such structure is created in various cases in product designs, we believe that the results shown in this study may be useful for EMC design as well as signal integrity. For computation, method of moment was used.

A tail current source is often employed for many analog building blocks. It can limit the increase of excess power. It can also improve CMRR and PSRR. In this paper, we propose a very high output impedance tail current source for low voltage applications. The proposed tail current source has almost the same output impedance as the conventional cascode type tail current source in theory. Simulation results show that the output impedance of the proposed circuit becomes 1.28 GW at low frequencies. Applying the proposed circuit to a differential amplifier, the CMRR is enhanced by 66.7 dB, compared to the conventional differential amplifier. Moreover, the proposed circuit has the other excellent merit. The output stage of the proposed tail current source can operate at VDS(sat) and a quarter of VDS(sat) of the simple current source in theory and simulation, respectively. For example, in the simulation, when the reference current IREF is set to 100µA, the minimum voltage of the simple current source approximates 0.4 V, whereas that of the proposed current source approximates 0.1 V. Thus, the dynamic range can be enlarged by 0.3 V in this case. The value is still enough large value for low voltage applications. Hence, the proposed tail current source is suitable for low voltage applications.

A lower impedance terminal is necessary for an input terminal of current-mode circuits and an output terminal of voltage-mode circuits to reduce an error and distortion in analog signal processing. Thus, the CMOS circuit with a very low impedance terminal (VLIT circuit) is a useful analog building block to achieve the above purpose. The very low impedance terminal in the VLIT circuit is performed by a shunt-series feedback configuration. However, the feedback generates a problem of instability and/or oscillation at the same time. The problem can be removed by a phase compensation capacitor as known well, but the capacitor is not desirable for integrated circuits due to its large area. This paper proposes a new phase compensation technique for the VLIT circuit. The proposed technique does not need any capacitors to obtain a sufficient phase margin, and instead gives us the appropriate transistor sizes (Width and length of the gate). As a result, the VLIT circuit has an enough phase margin and operates stably.

Simple approximate formulas are obtained for the mutual impedance and admittance by using a product of radiation patterns of antennas. The formulas come from a stationary expression of the reaction integral between two antennas where far-field approximations are employed. The theory deals with antennas in free space as well as under the presence of a wedge. Two applications are given for microstrip antennas with experimental verifications.

Effective wavelets to solve electromagnetic integral equations are proposed. It is based on the same construction procedure as Daubechies wavelets but with mix-phase to obtain maximum sparsity of moment matrix. These new wavelets are proved to have excellent performance in non-zero elements reduction in comparison with minimum-phase wavelet transform (WT). If further sparsity is concerned, wavelet packet (WP) transform can be applied but increases the computational complexity. In some cases, the capability of non-zero elements reduction by this new wavelets even better than WP with minimum-phase wavelets and with less computational efforts. Numerical experiments demonstrate the validity and effectiveness of the new wavelets.

This paper describes the expanded generalized method of characteristics (GMC) in order to handle large linear interconnect networks. The conventional GMC is applied to modeling each of transmission lines. Therefore, this method is not suitable to deal with large linear networks containing many transmission lines. Here, we propose the expanded GMC method to overcome this problem. This method computes a characteristic impedance and a new propagation function of the large linear networks containing many transmission lines. Furthermore the wave propagation delay is removed from the new wave propagation function using delay evaluation technique. Finally, it is shown that the present method enables the efficient and accurate simulation of the transmission line networks.

A correction of the physical optics approximation by accounting for the presence of specific currents concentrated near shadow boundaries on the surface of a convex non-metallic scatterer is analysed by considering a canonical problem of diffraction of a plane electromagnetic wave incident normally to the axis of an infinite circular cylinder with impedance boundary conditions. The analysis focuses on the development of Fock-type asymptotic representations for magnetic field tangent components on the surface of the scatterer. The Fock-type representation of the surface field is uniformly valid within the penumbra region, providing a continuous transition from the geometrical optics formulas on the lit portion of the surface to the creeping waves approximation in the deep shadow region. A new numerical procedure for evaluating Fock-type integrals is proposed that extracts rapidly varying factors and approximates the rest, slowly varying coefficients via interpolation. This allows us to obtain accurate and simple representations for the shadow boundary currents that can be directly inserted into the radiation integral and effectively integrated. We show that accounting for the shadow boundary currents considerably improves the traditional PO analysis of the high-frequency electromagnetic fields scattered from smooth and convex non-metallic obstacles, particularly near the forward scattering direction.

In this paper some new results for analog hardware realization of secure communication system using chaos synchronization have been presented. In particular the effect of the use of transmission line as channel has been considered assuming practical implementation. The influence of the loss of transmission line and mismatching on synchronization has been investigated in chaotic systems based on the Pecora-Carroll concept. It has been shown that desynchronization due to loss can be checked by using an amplifier with appropriate gain. Moreover the bit error rate (BER) has been evaluated in a digital communication system based on the principle of chaotic masking.