Taro Miura

Low-Temperature-Fireable Dielectric Material Pb(Fe2/3W1/3)O3-(Pb, Ca)(Fe1/2Nb1/2)O3 for Microwave Use

A ferroelectric Pb(Fe2/3W1/3)O3-Pb (Fe1/2Nb1/2)O3 (PFW-PFN) system has a low sintering temperature. A partial substitution of Ca for Pb in PFN shift the transition temperature sufficiently low, transforming this material into a paraelectric at room temperature. When paraelectric PFW-PCFN formed a single-phase (Pb, Ca)(W, Fe, Nb)O3 (PCWFN), this material was confirmed to have a high dielectric constant with temperature stability and low dissipation loss. There was a certain amount of difficulty associated with the synthesis of single-phased PCWFN. A process to overcome this difficulty is reported. Up to now, the sintering temperature of the best characterized material was 1000°C. This temperature is very low for the sintering of a glass-free dielectric material used as a microwave resonator.

Optimization of a lumped element circulator based on eigenvalue evaluation and structural improvement

An optimization technique for a lumped element circulator has been established from the point of view of theoretical characteristic design and structural improvement. A theoretical design based on the evaluation of the eigenvalues of an inductance matrix made it possible to optimize the isolation bandwidth characteristic of a structurally improved circulator. Structural optimization was achieved by the application of multilayer ceramic technology and novel conductor formation methods to increase the isolation bandwidth of the circulator and to decrease its insertion loss. The 20 dB isolation bandwidth of 5.8% obtained by this circulator exceeded the characteristics of a conventional circulator of the same size by 29%, while an insertion loss of 0.35 dB was maintained. In view of the present status of ceramic technology, it is believed that this circulator has been ultimately close to the preferred structure for lumped element circulators.

Measurement of temperature dependence of relative permittivity by the cavity perturbation method

A new cavity perturbation method has been proposed as a technique for evaluating the temperature dependence of relative permittivity, /spl tau//spl epsi/, in the pseudo-microwave range. In order to increase the accuracy of this method, an automatic measuring apparatus, satisfying the perturbation principle, was constructed and improvements in data processing were employed, such as the periodic least square method. Results for some microwave dielectrics demonstrated that measured /spl tau//spl epsi/ values for this method conform to those of the dielectric rod resonator method.

New lumped element circulator by ceramic integrated circuit technology

A broadband and a compact lumped element circulator was developed by a co-firing method of a ferrite and inner conductor. A circulator fabricated by this method with the dimensions of 6/spl times/6/spl times/3 (mm) showed a 20 dB isolation bandwidth of 7% and an insertion loss of 0.7 dB at 800 MHz. The gyromagnetic inductance of this circulator was compared to that of a conventional circulator. The former always showed a higher inductance than the latter. This measurement and additional measurement of the inductance for non-magnetized ferrite disks with and without a gap have shown that a great portion of permeability increase came from the elimination of the demagnetizing field in the element. Although a broadbanding was obtained, the insertion loss of 0.7 dB could be improved by using a more conductive material. To optimize the isolation bandwidth, a refinement of the design method based on the gyromagnetic inductance measurement should also be established. In spite of these problems, the magnetically closed circuit circulator, mC/sup 3/, seems to be the ultimate lumped element circulator from its broadband characteristics, compact size and simplified structure, to reduce production costs. Furthermore, the broadband characteristics decrease the loaded Q-factor causing an increase in the handling power of the circulator which is a useful feature in broadcasting equipment. >

Determination of the frequency dependence of complex permittivity in the pseudo-microwave range by an advanced perturbation method

The authors proposed a suitable technique for the evaluation of complex permittivity in the pseudo-microwave range. Considerable improvements have been made in the accuracy of Q evaluation by the cavity perturbation method. The advanced method employed was five times as accurate as the conventional cursor function method, installed in network analyzers. The frequency dependence of complex permittivity for microwave dielectrics and low-temperature-fireable materials was also discussed. The results of frequency dependence measurements demonstrated that some characteristics of microwave dielectrics could not simply be determined by the Qf-constant rule. Therefore, development of an evaluation technique within the confines of the pseudo-microwave range was significant.

Influence of sample insertion hole on resonant cavity perturbation measuring method

Influence of sample insertion holes in resonant cavity for a measuring fixture was investigated experimentally and numerically. Shift of the resonant frequency caused by loaded sample decreased when the cavity height decreased or dielectric constant of a sample increased. Employing tall cavity improved measurement error. Using commercial simulators, it was found that disturbance of electric field near the sample insertion hole caused deviation of resonant frequency from the ideally closed cavity. The simulation result was inspected from the viewpoint of physical rationality.

Temperature stabilization of a lumped element circulator without an apparent compensating element

An experiment has shown that a thermostable circulator can be fabricated by inserting a small capacitor between the ground and the ferrite. The analysis and the characteristics estimated using the element eigenvalues have confirmed the experimental result. A circulator based on the above thermostabilization has shown that the bandwidth was expanded more than twofold in the temperature range from -25/spl deg/C to 85/spl deg/C.

Spectrum management of pulse transmission by high-cut filter using magnetic loss

Operation problems of a 200 MHz clock computer bus were analyzed by the time domain transmission of pulse in the bus. An absorptive high-cut filter was fabricated and installed to solve the problems. In the process of determining the operating conditions, we came upon a new concept for spectrum management.

MEASUREMENT OF COMPLEX DIELECTRIC CONSTANT ABOVE ROOM TEMPERATURE AND ITS APPLICATION TO DETERMINATION OF INTRINSIC DIELECTRIC LOSS

Measurements of the complex permittivity on single crystal dielectric materials with different crystal symmetry have been carried out at high temperatures. The theory of intrinsic dielectric loss proposed by Gurevich et al.. was confirmed for Oh7 and D3d6 symmetries. X-ray topography images showed that crystal disorientation caused a deleterious influence on dielectric loss.

Optimization of a lumped element circulator based on eigen inductance evaluation and structural improvement

An optimization technique for a lumped element circulators has been established from the point of view of structure and characteristic design. Structural optimization was achieved by the application of multilayer ceramic technology and a novel conductor formation method to decrease the insertion loss of the circulator. A theoretical design based on an evaluation of eigen inductance made it possible to broaden the isolation bandwidth of a structurally improved circulator. The 20 dB isolation bandwidth of 5.8% and the insertion loss of 0.55 dB at 800 MHz obtained by this circulator have significantly exceeded the characteristics of conventional circulators of the same size.