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Analysis of aperture coupled microstrip transmission lines and antennas
The main subject of this work is the modular design of multilayer printed arrays. The need for a multilayer feeding network is evident in large arrays with a large number of power dividers or phase shifters. Due to space considerations the spurious coupling between the network and the radiating elements, or between different parts of the network itself, can be significant enough to degrade performance. In addition, corporate feed network radiation can affect the sidelobe and cross-polarization characteristics of the array. The use of a multilayer feed network located in a different plane than the radiating elements can alleviate these problems.^ The transfer of power between two adjacent layers in a multilayer structure can be done using either a pin which makes an electrical contact, or via coupling apertures in the ground plane separating the layers. Beyond the advantages of fabrication, aperture coupling leads to inherently symmetric feed network layouts which further simplify the design. The Green's functions for multilayer dielectric substrates can be used to compute the characteristic impedance of any printed planar transmission line and the full-wave analysis of an entire multilayer network can be obtained. In the past, full-wave solutions were derived for different configurations involving the coupling from one layer to another by means of a rectangular slot. The number of possible configurations is quite limited, since in a typical planar multi layer structure there may be only two microstrip layers (the outermost layers), while the inner layers are typically stripline. This leaves two types of aperture coupling transitions: microstrip to stripline and stripline to stripline. Assuming that the coupling between separate apertures and the coupling between patches is negligible, having a model for each of these two transitions is enough to analyze and design the whole multilayer structure. The radiating elements can also be fed by aperture coupling, and a separate analysis has to be performed for each configuration. Furthermore, the radiating element layer can be placed in a plane perpendicular to the feeding network.^ The theory used in the modeling of different transitions will be presented first. The reciprocity technique first developed in (9) and further extended in (10) proves to be computationally efficient and gives good results for these cases. The models for individual transitions are validated by measurements and subsequently used in the design of a number of prototype multilayer planar arrays. ^
Herscovici, Naftali I, "Analysis of aperture coupled microstrip transmission lines and antennas" (1992). Doctoral Dissertations Available from Proquest. AAI9305839.