Active integrated antennas are a maturing topic. Many novel configurations have been described and system designers are how investigating how the advantages of compactness and increased functionality can be exploited in applications. In this paper, the various types of integrated antennas are discussed together with possible ways of exploiting the technology. New configurations of direct conversion integrated antennas are then described in detail, which illustrate some of the possibilities inherent in the technology.

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.