Scan blindnesses in infinite arrays of microstrip dipole antennas with coplanar strip feedlines

A spectral periodic Green´s function technique was previously used to analyze infinite, planar, phased arrays of microstrip dipoles with idealized feeds (Yeo and Parfitt, 1995, 1996). The results of the numerical models using this technique were shown to agree well with those obtained with other models found in the literature (Yeo and Parfitt, 1996), including the prediction of a substrate induced scan blindness effect. The same technique of analysis is now extended to model microstrip dipole and microstrip folded dipole arrays with coplanar strip feedlines. In the case of dipole arrays without substrates, the effect of feedline-induced scan blindness has long ago been observed (Schuman et al., 1984). However, for a phased array of microstrip dipoles with feedlines, both the feedline and substrate effects can potentially cause a blindness condition to occur in its scanning performance. The aim of this paper is to describe the feedline-induced and substrate-induced scan blindness effects in microstrip dipole and folded dipole arrays with feedlines, and the effect of each type of scan blindness for different substrate electrical thicknesses.