Among several optical devices in integrated optics, the fundamental characteristics of collinear optical switching devices have been studied about optical dielectric waveguides. Conventional waveguide-type acousto-optic (A-O) devices use collinear and longitudinal interactions with mode coupling based on the Bragg condition between optical waves and surface acoustic waves (SAW). Collinear A-O devices of the waveguide-type show sufficient performance for wavelength-selective switching with narrow bandwidths. However, in these collinear A-O devices, interaction time is several microseconds for 10 mm waveguide device length. In A-O devices of optical waveguides using transverse A-O interaction, where SAW propagates transversely to optical wave propagation direction, SAW propagation lengths needed for complete A-O interaction may become 10 µm and interaction time may be several nanoseconds. In this paper, fundamental characteristics of the transverse A-O interaction are studied as an electromagnetic boundary value problem. Refractive indices in optical waveguides induced by A-O effects with SAW are shown by sine functions. Wave field characteristics in periodic structures for transverse directions are analyzed by analytic method of Hill's equations for transverse spectral functions. Electromagnetic fields in regions with periodic structures are discussed by the Mathieu functions and the perturbation method. Dispersion characteristics of A-O eigen modes are studied for wavelengths of optical waves and SAW, with A-O coefficients.

A high frequency approximation method is proposed to obtain the scattering from rectangular dielectric cuboids. Our formulation is based on a Kirchhoff type aperture integration of the equivalent current sources over the surface of the scattering bodies. The derived formulae have been used to get the radar cross section of cuboids, and the results are compared with those by other methods, such as physical optics, geometrical theory of diffraction, the HFSS simulation and measurements. Good agreement has been observed to confirm the validity of our method.

A frequency-domain (FD) uniform asymptotic solution (FD-UAS) which is useful for engineering applications is newly derived for the two-dimensional scattered magnetic field by a coated conducting cylinder covered with a thin lossy medium. The FD-UAS is uniform in the sense that it remains valid within the transition region adjacent to the shadow boundary, and it smoothly connects a geometric optical ray (GO) solution and a geometrical theory of diffraction (GTD) solution exterior to the transition region, respectively. We assume that the thickness of a coating medium is thin as compared with one wavelength of a cylindrical wave radiated from a magnetic line source. This uniform asymptotic solution is represented by a combination of scattered field component solutions, namely, the GO solution composed of a direct GO (DGO) and a reflected GO, the extended uniform GTD (extended UTD) solution made up of a DGO and a pseudo surface diffracted ray (pseudo SD), the modified UTD solution representing SD series, and the GTD solution for a lowest order SD. The FD-UAS is valid for a source point and/or an observation point located either near the coating surface or in the far-zone. The effectiveness and usefulness of the FD-UAS presented here are confirmed by comparing with both the exact solution and the conventional UTD shadow region solution.

The characteristic basis function method using improved primary characteristic basis functions (IP-CBFM) has been proposed as a technique for high-precision analysis of monostatic radar cross section (RCS) of a scattering field in a specific coordinate plane. IP-CBFM is a method which reduces the number of CBF necessary to express a current distribution by combining secondary CBF calculated for each block of the scatterer with the primary CBF to form a single improved primary CBF (IP-CBF). When the proposed technique was evaluated by calculating the monostatic RCS of a perfect electric conductor plate and cylinder, it was found that solutions corresponding well with analysis results from conventional CBFM can be obtained from small-scale matrix equations.

In the development of inter-vehicle communication systems for the prevention of car crashes, it is important to know radio propagation characteristics at blind intersections. In field experiments and numerical simulations to investigate radio propagation characteristics, a half wavelength dipole antenna is assumed to be the wave source in many cases. However, a directivity of car antenna is changed by the effect of both car body and antenna position on car. In this paper, path loss characteristics considering antenna positions on car body at a blind intersection in urban area for inter-vehicle communications using 700MHz band are investigated. Additionally, simplified car models are proposed for the efficient analysis of radio propagation. Here, the hybrid method using both FDTD and ray-tracing methods is used for the radio propagation analysis.

We propose an effective technique for estimation of targets by ground penetrating radar (GPR) using model-based compressive sensing (CS). We demonstrate the technique's performance by applying it to detection of buried landmines. The conventional CS algorithm enables the reconstruction of sparse subsurface images using much reduced measurement by exploiting its sparsity. However, for landmine detection purposes, CS faces some challenges because the landmine is not exactly a point target and also faces high level clutter from the propagation in the medium. By exploiting the physical characteristics of the landmine using model-based CS, the probability of landmine detection can be increased. Using a small pixel size, the landmine reflection in the image is represented by several pixels grouped in a three dimensional plane. This block structure can be used in the model based CS processing for imaging the buried landmine. The evaluation using laboratory data and datasets obtained from an actual mine field in Cambodia shows that the model-based CS gives better reconstruction of landmine images than conventional CS.

We propose a new swept-frequency measurement method for the electromagnetic characterization of materials. The material is a multilayer cylinder that pierces a rectangular waveguide through two holes in the narrow waveguide walls. The complex permittivity and permeability of the material are calculated from measured S-parameters as an inverse problem. To this aim, the paper develops a complete electromagnetic formulation of the problem, where the effects of material insertion holes are taken into consideration. The formulation is validated through the measurement of ferrite and water samples in the S-band.

It has been reported that a left-handed waveguide can be constituted using cutoff TE₁₀ mode of rectangular waveguide. Because the cutoff TE₁₀ mode shows effectively negative permittivity, the left-handed mode propagates by adding series capacitance in the form of short- or open-stubs. This paper suggests a constitution method of left-handed waveguides using cutoff TM mode. In this case, the cutoff TM mode shows effectively negative permeability. Therefore, a left-handed waveguide can be constituted by adding parallel inductance. In this paper, two types of the left-handed waveguides are designed using circular TM₀₁ mode and rectangular TM₁₁ mode, and the dispersion characteristics are numerically investigated. The validity of the constituting principle is confirmed by an experiment.

We deal with the scattering of a plane wave by the end-face of a waveguide system by the numerical method based on the sinc function and calculate the electric field on the end-face. It is shown that the results obtained analytically by the perturbation method are in relatively good agreement with the numerical results.

In this paper, an electromagnetic plane wave diffraction by finite number of loaded thick slits on infinitely long perfectly electric conductor (PEC) screen is analyzed. Here we formulate the problem by utilizing the Kobayashi Potential (KP) method, which is a kind of eigenfunction expansion method in terns of Weber-Schafheitlin discontinuous integrals. The multiple scattering contributions between the slits are analytically included in the formulation. The solution derived here may provide us with precise numerical result, so it may be considered as a reference solution to other numerical and approximate analyses.

We propose an algorithm for the scattering analyses of gratings with various local defects based on the difference-field boundary-element method (DFBEM). In the algorithm, the defect in the grating is partitioned, and the DFBEM is sequentially applied for each defect section. We validate the proposed algorithm by demonstrating its flexibility for various defect topologies for a locally deformed grating.

An efficient sharply bent waveguide with a microcavity constructed by an air-bridge type two-dimensional photonic crystal slab is analyzed. The method of solution is the three-dimensional finite difference time domain (FD-TD) method. The bent waveguide has a microcavity structure that connects to an input and an output waveguide ports. The radius and position of air-holes surrounding the microcavity are modified to adjust the resonant frequency to the single-mode regime of the waveguides. It is confirmed that input optical power is transmitted efficiently to the output waveguide due to resonant tunneling caused by the microcavity.

A novel directional coupler loaded with feedback capacitances on the coupled lines is presented. Its effect of enhancing the coupling is qualitatively shown by deriving an equation for the coupling. Besides, a method to compensate for the phase difference between the even and odd modes of the coupler is presented. To demonstrate, a novel tandem 3-dB coupler consisting of the proposed coupled lines is designed and described. In addition, a waveguide (rectangular coaxial line) 8×8 HYB matrix using planar double-layer structure that is composed of the proposed tandem 3-dB couplers and branch-line couplers, which is operated in S-band, is designed and fabricated showing excellent performance.

Because redox sensors can detect multi-ions and the concentration within a single sensing area using current and potential signals, they have been studied for chemical analysis applications. A small sensing area and a low concentration measurement typically reduce the output current of a redox sensor. Therefore, we previously fabricated the Amplified Redox Sensor, which has a working electrode combined with a bipolar transistor to amplify a small current signal. However, the current gain of the bipolar transistor had been changed by the redox current because the redox current flows in the base terminal of the bipolar transistor. In this study, we propose a new measurement method in which an offset current is inserted along with the redox current in the base terminal. The proposed measurement method can detect potassium ferricyanide (K₃[Fe (CN)₆]) concentrations as low as 1μM using the Square Wave Voltammetry method.

This paper presents new Binary Converters (or current-mode compressors) by the usage of carbon nanotube field effect transistors. The new designs are made of three parts: 1) the input currents which are converted to voltage; 2) threshold detectors; and 3) the output current flow paths. In addition, an 8×8-bit multiplier is considered as a bench mark to estimate their efficiency degrees. The first approach is based on high-order Binary Converters, and the second one is only composed of 4BCs and Half Adders.

This paper proposes an analytical, closed-form AC-DC voltage multiplier model and investigates the dependency of output current and input power on circuit and device parameters. The model uses no fitting parameters and a frequency term applicable to both multipliers using diodes and metal-oxide semiconductor field effect transistors (MOSFETs). Analysis enables circuit designers to estimate circuit parameters, such as the number of stages and capacitance per stages, and device parameters such as saturation current (in the case of diodes) or transconductance (in the case of MOSFETs). Comparisons of the proposed model with SPICE simulation results as well as other models are also provided for validation. In addition, design optimizations and the impact of AC power source impedance on output power are also investigated.

A simplified circuit has been utilized for fast computation of the current flowing in the cross-point memory array. However, the circuit has a constraint in that the selected cell is located farthest from current drivers so as to estimate the current degraded by metal wire resistance. This is because the length of the current path along the metal wire varies with the selected address in the cross-point memory array. In this paper, a new simplified circuit is proposed for calculating the current at every address in order to take account of the metal wire resistance. By employing the Monte Carlo simulation to solve the proposed simplified circuit, the current distribution across the array is obtained, so that failure rates of read disturbance and write error are estimated precisely. By comparing the conventional and the proposed simplified circuits, it was found that the conventional simplified circuit estimated optimistic failure rates for read disturbance and for write error when the wire resistance was prominent enough as a parasitic resistance.

The Lyapunov stability theory-based adaptive filter (LST-AF) is a robust filtering algorithm which the tracking error quickly converges to zero asymptotically. Recently, the software module of the LST-AF algorithm is effectively used in engineering applications such as tracking, prediction, noise cancellation and system identification problems. Therefore, hardware implementation becomes necessary in many cases where real time procedure is needed. In this paper, an implementation of the LST-AF algorithm on Field Programmable Gate Arrays (FPGA) is realized for the first time to our knowledge. The proposed hardware implementation on FPGA is performed for two main benchmark problems; i) tracking of an artificial signal and a Henon chaotic signal, ii) estimation of filter parameters using a system identification model. Experimental results are comparatively presented to test accuracy, performance and logic occupation. The results show that our proposed hardware implementation not only conserves the capabilities of software versions of the LST-AF algorithm but also achieves a better performance than them.

Ultra-wideband radar exhibits high range resolution, and excellent capability for penetrating dielectric media, especially when using lower frequency microwaves. Thus, it has a great potential for innovative non-destructive testing of aging roads or bridges or for non-invasive medical imaging applications. In this context, we have already proposed an accurate dielectric constant estimation method for a homogeneous dielectric medium, based on a geometrical optics (GO) approximation, where the dielectric boundary points and their normal vectors are directly reproduced using the range point migration (RPM) method. In addition, to compensate for the estimation error incurred by the GO approximation, a waveform compensation scheme employing the finite-difference time domain (FDTD) method was incorporated. This paper shows the experimental validation of this method, where a new approach for suppressing the creeping wave along the dielectric boundary is also introduced. The results from real observation data validate the effectiveness of the proposed method in terms of highly accurate dielectric constant estimation and embedded object boundary reconstruction.

A regulated charge pump (CP) with an extended range of load current is presented. A power-efficient adaptive feedback controller is adopted. Verified by a 0.18µm CMOS technology with a power supply of 3.3V, the measured output voltage of the CP is regulated above 5V when the load current is varied from 2.5mA to 50mA. The measured power efficiency spans from 81.7% at lighter load to 75.2% when load current is 50mA. The measured output ripples are small and below 24mV.