Makoto Tsutsumi

Harmonic control by photonic bandgap on microstrip patch antenna

In this work, the single microstrip patch antenna having two-dimensional photonic bandgap (PBG) in the ground has been demonstrated experimentally, and the effectiveness of the PBG structure is discussed for the suppression of the resonance at the harmonic frequencies of the antenna. Experimental results indicate that the radiation patterns at the harmonic frequencies can be drastically diminished comparing with the normal microstrip patch antenna without the PBG structure. For instance, the radiation to the forward of the PBG antenna is suppressed at more than 15 dB at the third harmonic frequency.

Nonreciprocal Phase-Shift Composite Right/Left Handed Transmission Lines and Their Application to Leaky Wave Antennas

A new type of nonreciprocal phase-shift transmission line is proposed; it realizes the dominant right-handed mode in one direction of the power flow along the line, and the dominant left-handed mode in the opposite power direction. These right and left handed modes can have the same wave number vector at a specific frequency but there is no significant coupling effect. An equivalent circuit model is provided to explain its nonreciprocal transmission characteristics. A nonreciprocal phase-shift composite right/left handed transmission line is designed to satisfy specific performance parameters and fabricated as a ferrite microstrip line. The leaky wave radiation characteristics of the fabricated nonreciprocal line are investigated. An experiment and analyses confirm obliquely unidirectional leaky wave radiation from the line for the two different directions of the transmitted power.

Superconducting microstrip resonator with yttrium iron garnet single crystals

A magnetically tunable microstrip superconducting resonator using an yttrium-iron-garnet (YIG) single crystal was demonstrated experimentally. Tunability of 200 MHz at a center frequency of 5.3 GHz was observed, and a quality factor of 965 with minimum insertion loss of 19.5 dB was measured for a half-wavelength microstrip line consisting of a YIG-YBCO-MgO composite structure. The dispersion relation of the resonator was analyzed using the spectral-domain method and discussed with experimental results on the mixed states of TEM and magnetostatic-wave modes. Power dependence of the characteristics is also discussed.

Left-handed transmission characteristics of ferrite microstrip lines without series capacitive loading

A nonreciprocal left-handed transmission line is proposed and investigated, which is composed of a normally magnetized ferrite microstrip line periodically loaded with inductive stubs but without capacitive loading. The circuit configuration becomes simpler than that of a nonreciprocal left-handed transmission line with both shunt inductive and series capacitive loadings. In the proposed structure, ferrite medium is employed as the substrate not only for the nonreciprocal characteristics but also for negative effective permeability that is essential to establish the left-handedness. After calculations of dispersion curves using equivalent circuit model, scattering parameters along with field patterns are estimated numerically with the help of electromagnetic simulation, and the experiments are also carried out. It is found that the band width of the proposed left-handed transmission line is relatively narrow but the structure still has the high isolation ratio of more than 30 dB.

A new magnetostatic wave delay line using YIG film

We have proposed a delay line of microstrip type consisting of a microstrip line fabricated on a composite substrate of two yttrium iron garnet films separated by a gadolinium gallium garnet layer. The dispersion relations are derived assuming magnetic walls at the edges of the strip. Experiments are carried out at S band with nonuniform magnetic field. Insertion loss less than 25 dB with large delay time more than 800 ns is observed experimentally. The experimental results on delay line characteristics are briefly discussed with theory.

Microstrip line filters using yttrium iron garnet film

The yttrium iron garnet (YIG) film microstrip line was fabricated by using 40- mu m-thick film with a width of 20 mm and a length of 10 mm along with a 0.7-mm-wide microstrip and was magnetized in a transverse direction to the wave propagation. Sharp notch characteristics of more than 30 dB with few dB insertion loss were observed experimentally with a variable center frequency from 9 GHz to 11 GHz. Results are explained phenomenologically with the coupled mode theory. >

Magnetically tunable superconductor filters using yttrium iron garnet films

Magnetically tunable superconducting single-resonator filters using YIG films have been demonstrated experimentally. Tunability of 400 MHz at a center frequency of 6 GHz was achieved for a half wavelength microstrip comprising a YIG-YBCO-MgO composite structure. The reason why the quality factor of the filter is relatively low is possibly due to an increase of the magnetic linewidth /spl Delta/H at liquid nitrogen temperature. The theory on dispersion relation of the filter is also presented.

Scattering of millimeter waves by metallic strip gratings on an optically plasma-induced semiconductor slab

This paper presents the scattering characteristics of a TE electromagnetic plane wave by metallic strip gratings on an optically induced plasma slab in silicon at millimeter-wave frequencies. The characteristics were analyzed by using the spectral domain Galerkin method and estimated numerically. We examined how to control the resonance anomaly by changing the optically induced plasma density for metallic strip grating structures fabricated on highly resistive silicon. The optical control characteristics of the reflection and the forward scattering pattern of the grating structures were measured at Q band and are discussed briefly with theory.

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.

Propagation characteristics of the magnetostatic surface wave in the YBCO-YIG film-layered structure

Propagation characteristics of the magnetostatic surface wave (MSSW) in a YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO)-yttrium iron garnet (YIG) multilayered structure are investigated. Effects of the superconductor on the MSSW are discussed with regard to the dispersion characteristics of both the phase and attenuation constants as a function of the air gap, between YIG and YBCO, taking into consideration the magnetic line-width of the YIG film. It was found that the nonreciprocity of MSSW is enhanced significantly by the superconductivity and depends on the magnetic line-width of the YIG film. To examine the effect of a YBCO on the MSSW propagation, experiments are carried out using a commercially available YIG film. Magnetic losses at low temperature are briefly discussed with experimentally observed nonreciprocity.