Youhei Ishikawa

Microwave Bandpass Filters Containing Dielectric Resonators with Improved Temperature Stability and Spurious Response

The development of dielectric resonator superior to invar cavity on temperature stability as the result of our research made the usage of the miniature bandpass filter practical, and the method to set up temperature coefficient was established well.

A dry phantom material composed of ceramic and graphite powder

Details of an artificially synthesized dry phantom material developed for experimental studies of microwave exposure to the human body are shown. The material is solid and can simulate electrical characteristics of high water content biological tissues such as muscles and the brain. The material is composed of high-/spl epsiv//sub r/ ceramic powder, graphite powder, and bonding resin. Any shape of phantom models can be constructed to simulate different parts of the body, as well as the head. The paper reports the synthesis technique to obtain the desired complex permittivity and the fabrication technique of the phantom models for usage of specific absorption rate (SAR) estimation at 900 MHz.

Miniaturization technologies of dielectric resonator filters for mobile communications

The unloaded Q of a fixed frequency cavity resonator which is filled with low-loss dielectric material is proportional to the cubic root of its volume due to the intensified current loss in the cavity wall. Utilization of such materials to reduce resonator size must be evaluated by taking this volume dependency into account. This paper describes several resonator miniaturization techniques, including the multimode reuse of space, the use of supplementary energy resonators (so called active resonator) with a enhanced apparent Q value, the low-stored-energy filter technique using transversal filters, and the reduced size resonators using mirror image technique. >

800 MHz high-power duplexer using TM dual mode dielectric resonators

A small-size, high-power duplexer in the 800-MHz band has been developed by using whole monoblock TM/sub 110/ dual-mode dielectric resonators. Insertion loss is less than 0.35 dB over a 20-MHz bandwidth in a TX filter and less than 0.47 dB over a 40-MHz bandwidth in a RX filter. Volume is less than 3000 cm/sup 3/, which corresponds to about 20% of the reentrant cavity resonator filter. This duplexer is useful for current and future cellular base stations.<<ETX>>

Quarter Wave Dielectric Transmission Line Diplexer for Land Mobile Communications

Small sized Diplexer with high selectivity and low insertion loss for 800 MHz band land mobile communication systems has been developed using two port quarter wave coaxial dielectric resonators. A couple of resonators including inductive film electrode construct a compact resonance unit of the Diplexer and it is coupled by capacitive air gap spacings which operates as a part of J-inverter.

Mechanically tunable MSW bandpass filter with combined magnetic units

An MSW (magnetostatic wave) bandpass filter with combined magnetic units composed of main and submagnetic units has been developed. Its volume is reduced to one fifth that of conventional yttrium-iron-garnet (YIG)-sphere filters. The filter can be tuned mechanically and keep the same shape of transmission response at 2.5 approximately 2.75 GHz. The insertion loss can be kept less than 3 dB within 20-MHz bandwidth by adjusting the magnetic field distribution.<<ETX>>

Miniaturized 90 degree hybrid coupler using high dielectric substrate for QPSK modulator

This paper describes miniaturized 90 degree hybrid coupler using edge-coupled microstriplines. A high dielectric constant substrate (K=38) and high-density coupled-line configuration are adopted to realize small chip size. A conventional meandered coupled-line type and a new spiral coupled-line type were discussed for a high-density configuration. A bandwidth from 1.8 GHz to 3.6 GHz with /spl plusmn/0.5 dB power dividing balance and 90/spl plusmn/3 degrees phase difference were achieved with a chip size of 1.5/spl times/1.5 mm.

800 MHz High Power Bandpass Filter using TM Dual Mode Dielectric Resonators

A novel high power bandpass filter using TM110 dual mode dielectric resonators was developed. TM110 dual mode is achieved with dielectric resonators physically coupled in an asymmetrically orthogonal manner and these arrayed resonators are constructed in monoblock and have high unloaded Q. By assembling these resonators, an 800 MHz high power bandpass filter was realized. Specific features achieved with this new filter are, center frequency of 840 MHz, band width of 40 MHz, and insertion loss of 0.4 dB. Physical size is 80×90×180 mm. Volume is less than 30% of conventional type high power bandpass filter using cavity resonators. This filter is useful as an antenna filter for cellular base stations.

Miniaturized Diplexer for Land Mobile Communication Using High Dielectric Ceramics

Miniaturized Diplexer for 800 MHz land mobile communication system has been developed using dielectric quarter wavelength resonator having high permittivity of 37 and 90. The physical volume of diplexer is about 48 cc. The Spurious responses of quarter wavelength resonator were shifted to the higher frequencies by stepping the effective permittivity of the resonator material.

Dielectric receiving filter with sharp stopband using an active feedback resonator method for cellular base stations

The development of an 800-MHz-band dielectric receiving filter with a sharp stopband is presented. The filter is composed of a conventional dielectric antenna filter and thee active band-stop filters, each sharply eliminating one band in the passband. In the active band-stop filters, small dielectric resonators, in which the unloaded Q is raised to about 50000 by means of an active feedback resonator method, are used. These filters are designed to obtain optimum stability and an optimum noise figure. One of them has a center frequency of 845.75 MHz, a stopband width of 1.0 MHz, and an attenuation of 30 dB. Deviation of the resonant frequency is held without +or-30 kHz, and the noise figure at passband is adequately small. The size of the dielectric receiving filter is 480*250*44 mm/sup 3/, and the volume is less than 1/20 that of a conventional filter using cavity resonators. >