Kensuke Okubo

Backfire-to-endfire radiation characteristics of CRLH-TL using substrate integrated waveguide and metal-patches

We have proposed a new type of the CRLH-TL consisting of two-layer planar substrates recently. It consists of a base waveguide of a substrate integrated waveguide (SIW), and series capacitances realized by slit apertures and metal patchs arranged on the upper conductor of the SIW. It is expected to become one of the basic CRLH-TL structures over 10 GHz or millimeter-wave. However radiation from the metal-patchs cannot neglect in this structure. Then we proposed a leaky-wave antenna using the SIW metal-patch type CRLH-TL. In this paper, beam scan characteristics as a function of driving frequency are confirmed theoretically and experimentally. A SIW metal-patch type CRLH-TL with transition frequency of 16 GHz is designed for a leaky-wave antenna and fabricated. Measured results agree well with theoretical and numerical results.

Nonlinear behavior of electromagnetic waves in the YIG film microstrip line

The limiter and microwave soliton behavior were experimentally demonstrated in the microstrip line using the 20 /spl mu/m thick yttrium iron garnet film substrate at S band. These nonlinear phenomena were explained by the strong coupling between quasi-TEM and magnetostatic forward volume wave modes at magnetic resonance frequency of /spl gamma//spl mu//sub 0/H/sub 0//2/spl pi/ from an implicit dispersion relation of the stripline.

New composite right/left-handed transmission line using substrate integrated waveguide and metal-patches

A new Composite Right/Left-Handed Transmission Line (CRLH-TL) for millimeter wave frequency is proposed and investigated theoretically and experimentally. It consists of a Substrate Integrated Waveguide (SIW) with slit apertures and a dielectric film with metal patches. A prototype of SIW Metal-patch type CRLH-TL that satisfies the balance condition is designed. Dispersion diagram and S-parameters are derived numerically, and typical field distributions of RH and LH transmission and the zero-order resonance are shown. The experimental results of the proposed SIW Metal-patch type CRLH-TL agree the analytical results well. Because both the layers of the SIW and the metal-patched dielectric film compose simple planar periodic structure, the SIW Metal-patch type CRLH-TL has advantage of simple manufacturing. It is expected to be one of the basic structure of CRLH-TL or components such as leaky wave antenna and LH coupler above 10 GHz or millimeter wave frequency.

Magnetostatic-wave envelope soliton in microstrip line using YIG-film substrate

In this paper, a dispersion relation of the microstrip line on a yttrium-iron-garnet (YIG)-film substrate has been derived under the approximation of a two-dimensional analysis. The dispersion curve shows the mixed state of quasi-TEM mode and magnetostatic forward volume wave (MSFVW) mode, and these two modes are coupled with each other at gyromagnetic frequency where MSFVW solitons are excited efficiently. Based on the numerical parameters of the calculated dispersion curve, simulation of the soliton form has been carried out by numerically solving the nonlinear Schrodinger equation. The results are compared with the experimental results of MSFVW envelope bright soliton in a microstrip line on YIG-film-gadolinium-gallium-garnet substrate.

Broad-band cruciform substrate integrated waveguide couplers

This paper describes a method to broaden the bandwidth of cruciform substrate-integrated waveguide couplers. The design and the analysis of the couplers are performed using the H-plane planar circuit approach, and the frequency characteristics of the couplers designed at 24 GHz are shown. As a result, fractional bandwidths of 30% for a 3dB coupler and 16% for a 1.7dB coupler can be realized. The design results are verified numerically and experimentally.

Left-Handed Characteristics of Ferrite Microstrip Line Magnetized to Wave Propagation

Left-handed characteristics of microstrip line on the longitudinally magnetized ferrite substrate are investigated with both theoretically and experimentally. Transmission characteristics of the line are estimated by using an equivalent circuit model, and the high frequency structure simulator (HFSS) based on the finite element method. Experiments are undertaken using polycrystalline yttrium iron garnet substrate having 30 times 15 mm in thickness of 1 mm. Expected left-handed response within negative permeability region is found and agrees well with theory. Phase shifter tuned by the magnetic field is proposed as an application of the left-handed ferrite line.

Microstrip line on the oppositely magnetized ferrite substrate and its application to the nonreciprocal devices

This paper newly proposes a microstrip line on the oppositely magnetized ferrite substrate. Strong nonreciprocal transmission characteristic was confirmed with both theory and experiments. After discussions of the physical meaning of nonreciprocity of the line, a nonreciprocal four port junction and new design of a ring circulator along singular point of the bias field were demonstrated as applications of the strip line proposed.

On the Left Handed Ferrite Circulator

Left handed (LH) ferrite circulators composed of the nonreciprocal LH microstrip lines using perpendicularly magnetized ferrite substrate and operating at the negative permeability frequency are studied. Following three types of circulators are proposed: a disk shaped circulator having broadband characteristics and high insertion loss, a triangular shaped circulator having small insertion loss and narrowband characteristics, and a ferrite-coupled-line LH circulator having wideband characteristics and high isolation. Although each structure has a advantage of circulator operation, the ferrite-coupled-line LH circulator has a potential for new signal processing functions of signal flow of backward characteristics

Color image modification based on visual saliency for guiding visual attention

In this paper, we propose a modification method of color image, for a given region in the image, to obtain the image in which the region shows the highest saliency. Generally, it is thought that the most important part of an information system that assists human activities is a natural interface with human. In addition, eye-gaze information strongly reflects the human interest or their attention. Therefore, a gaze-based interface is promising for future practical applications. In particular, if we can smoothly guide the users visual attention toward a target without interrupting their current visual attention, the usefulness of the gaze-based interface will be highly enhanced. In order to realize a novel interface based on visual attention, we propose a modification method for color image based on visual saliency map. The proposed method iteratively modifies the intensity and color so that the saliency inside the specified region increases while that outside the region decreases. This iteration is carried out until we obtain the image in which the specified region is most salient over the entire image. With the image obtained in this way, we can smoothly attract the users visual attention to the specified region, without any interruption to the users gaze. We evaluated the proposed method by a gaze measurement system and subjective experiments. As a result, we confirmed that the users visual attention is indeed attracted toward our specified region without uncomfortable feeling.

On the Quasi-Left-Handed Transmission Line with Gyrator Loading

This paper treats transmission characteristics of periodic structure of ferrite gyrator circuit with both theory and experiment, which is loaded into usual distributed constant line with and without lumped capacitor. Following three types of periodic structure of gyrator circuit are proposed: basic structure of periodic gyrator circuit, quasi-LH gyrator circuit with series capacitance loading, and quasi-LH gyrator circuit with parallel capacitance loading. Moreover, replacing the parallel capacitance with a resistance, a periodic structure of isolator circuit is proposed. Scattering parameters of gyrator circuit are derived with help of equivalent circuit model. Left handed transmission behavior of backward wave is discussed from dispersion curves. Experiments were undertaken using periodic structure of dielectric microstrip line and gyrator circuit fabricated on the ferrite substrate. Experimental results having wide band nonreciprocal characteristics are discussed with theory.