Eikichi Yamashita

Characterization of A Folded Stepped Impedance Resonator for Miniature Microstrip Bandpass Filter Applications

In this paper we propose a Folded Stepped Impedance Resonator(FSIR) which is effective in realizing extremely compact microstrip bandpass filters. To characterize this new structure we use an FDTD algorithm where all discontinuity effects have been considered. For identical resonant frequencies, the proposed FSIR is found to be approximately 43 percent shorter in total length than conventional half-wavelength microstrip resonators. The accuracy of our FDTD analysis is verified through comparison with results in the open literature, and the effectiveness of the FSIR is also confirmed by experiments with two test resonators we have fabricated.

Performance of the modified Berenger PML absorbing boundary condition for evanescent waves in three-dimensional structures

The recently proposed modified PML (MPML) absorbing boundary condition is extended to three dimensions. The performance of the MPML is investigated by implementing FDTD simulation of a typical microstrip line. The dominant mode and the first higher order mode of the microstrip line are excited separately. In both cases of excitation, the reflection properties of the MPML boundaries are examined, respectively. Numerical results reveal that by choosing appropriate values of the introduced permittivity and permeability, efficient absorption of both evanescent waves and propagating waves can be realized over a wide frequency band.

Structural Control Of Microstrip Dispersion For Shaping Giga-Hertz-Bandwidth Pulses

Recent optical switching devices are using combinations of very short laser pulses, photoconductors, and strip lines. Since laser pulses have giga-hertz-bandwidth, signal transmission properties of such strip lines in a wide range of frequencies are decisively important. This paper describes the structural control of the dispersion characteristics of microstrip lines by adding ground conductors on both sides of the strip conductor. Some numerical data are shown.

Fiber-optic transceiver for optical time-domain reflectometers using an active fiber ring

A fiber-optic transceiver which is particularly suitable for long range optical time-domain reflectometers is proposed. An active fiber ring employed in the proposed configuration has both transmitter and receiver functions. The active fiber ring acts as a Q-switched pulse laser source in the transmitter whereas it acts as an optical preamplifier in the receiver. Experimental results on the reflection detection of several lengths of optical fibers have confirmed the operation principle of the proposed scheme.

Comparative studies of three types of coplanar waveguide structures for millimeter-wave applications

Three types of coplanar waveguide (CPW) structures with shielding grooves for suppressing surface wave leakage are characterized by using a full-wave mode-matching analysis. Influence of the geometrical dimensions of the groove on their phase constants, characteristic impedances, and single mode frequency bands are investigated. The results reveal that the inverted microshield CPW is particularly attractive for realizing wide band and low dispersion millimeter wave transmission lines and circuits.

Analysis Method for Single and Coupled Striplines Loaded with Dielectric Ridge

In this paper, a new analysis method, that is, the partial-boundary integral equation method (PBIEM) is proposed for the analysis of single and coupled striplines loaded with a dielectric ridge. The latter structure could be used for matching the velocity of the even and odd mode. The numerical results show the usefulness of this analysis method.

Application of Microwaves to the Safety System of Railroad Crossings

A new system to prevent collision accidents between cars and trains on railroad crossings is described in which microwave radiation from Gunn-diode oscillators are used to recognize obstacles. Experimental results are reported.