Radiation characteristics of various microstrip MIC passive elements are investigated in detail on the basis of accurate numerical analysis. For this purpose, the FD-TD method combined with the radiation mode theory is used. Summarized results are presented mainly from the viewpoint of making clear how radiation characteristics differ depending upon typical features of element structures and operating frequencies. Particularly important features of this paper are that not only radiation into the space region but also that in the substrate region is studied in detail for the first time. Suggestive remarks are given on positioning of active devices in MIC for avoiding interference from nearby elements.

An analysis method based on the FD-TD and radiation mode expansion methods and its simulation tool are developed for calculating circuit characteristics and parameter values of passive MMIC (Monolithic Microwave Integrated Circuits) elements having multilayer structure. For straight multilayer microstrip lines and coplanar waveguides, it is possible to calculate characteristic impedance, effective permittivity, transverse field distribution of guided modes, etc. For various multilayer microstrip and coplanar waveguide elements, it is possible to calculate scattering parameters, radiated power, radiation patterns, etc. As an example of application of the present technique, effects of inclusion of lower permittivity layer in the substrate on transmission and radiation characteristics are investigated for right-angled microstrip bends.

A simulation tool for analyzing circuit characteristics of microstrip-type MIC (Microwave Integrated Circuit) passive elements is presented. The major part of this tool is the electromagnetic wave analysis based on the FD-TD (Finite-Difference Time-Domain) method combined with the mode expansion theory. Although the element structures which can be treated in this tool are limited to only less than ten fundamental structures in the present stage, its extension to the more versatile tool applicable to other various element types is rather straightforward and simple in principle. When using this tool, we first choose the element configuration to be calculated and give, on a panel, necessary parameter values related to calculation range and mesh division scheme. Given these values, the first step calculation starts to obtain the characteristic impedance, cross sectional field distribution of the propagating mode, etc. of the basic microstrip line. Field distributions around the element configulation are calculated next with the mode field oscillation being given. Through this process the field distributions on a closed rectangular parallelepiped surface enclosing the element configuration are stored in files, from which S parameter and radiated fields are calculated by invoking the reaction integral with propagation modes and radiation modes, respectively. The results obtained in these three steps can be expressed, at our discretion, as line drawings or two-dimensional density plots.

In this paper, a realization of an imaginary resistor using an ideal transformer is proposed. In the same fashion as the conventional method, a signal path is divided into a real signal path and an imaginary path. We name circuits which constitute a real signal path and an imaginary signal path, a real circuit and an imaginary circuit, respectively. An imaginary resistor is converted into an ideal transformer embedded between the imaginary circuit and the real circuit. The imaginary circuit becomes a dual circuit of the real circuit. This filter consists of terminating resistors, inductors, capacitors and ideal transformers. This prototype circuit is simulated by using operational amplifiers. A 3rd-order complex Chebyshev bandpass filter is designed and its frequency response is measured. Finally, the sensitivity property of the proposed filter is evaluated by a computer simulation.

Solder joint reliability was studied for hybrid ICs, in which chip components such as FETs, resistors and capacitors were mounted with Sn-Sb solder on an insulated Al substrate and transfer-molded with epoxy resin. Suitable resin selection for molding was also studied. The structure was estimated to have a lifetime of more than ten thousand cycles in the thermal cycling test under the condition of -55/150, for FETs and passive elements. Equivalent plastic strains generated in the soldering layer for the non-molded structure were 4. 6% for the FETs and 3.5% for the passive elements. But, these strains were approximately 1/3 to 1/2 and 1/10 for the molded structure, respectively. This was the main reason for high reliability of the molded structure. Resins with a wide range of thermal expansion coefficient(8-26 ppm/)could be put to practical use, because of the higher reliability of the molded structure. However, a thermal expansion coefficient of about 15 ppm/ was prefered to decrease stress at the interface between the substrate and the molding resin.

Novel three-dimensional structures for passive elements--inductors, capacitors, transmission lines, and airbridges--have been developed to reduce the area they consume in GaAs MMICs. These structures can be formed with a simple technology by electroplating along the sidewalls of a photoresist. Adopting the new structures, most passive elements in MMICs have been shrunk to less than 1/4 the size of conventional ones.