Application of Hybrid Radiation Modes of Microstrip Line in Rectangular Patch Antennas Design

The radiation from microwave integrated circuits (MIC) and millimeter microwave integrated circuits (MMIC) is the object of interests from theoretical and practical points of views. The results of such investigations permit to anticipate the properties of open structures when they are optimized for maximum of radiation (the antenna case) or to minimize of radiation effects (in the most of circuits radiation is parasitic effect). The radiation from microstrip-like waveguiding structure can be represented by means of continuum of so-called hybrid radiation (HR) modes. We showed in the paper that properly chosen single HR mode can be applied to the design of rectangular patch antenna. As an introduction we presented modal analysis of the open dielectric slab waveguide since its modes "built" the em field of microstrip line. For the better understanding of the modes properties of the open slab we started from shielding structure analysis and then a transition to the open structure was made by receding the upper enclosure to infinity. Similar approach was next presented for microstrip-like line using spectral domain representation, however field nonhomogeneity in the strip interface led to hybrid nature of HR modes. We have proposed an additional condition for HR modes and an iterative procedure to find the solution of the problem, which consisted of perturbed EH^(y) and HE^(y) HR modes in this case. We showed in the next part of the paper that single EH^(y) HR mode of microstrip line with the phase constant beta ap 0 could approximate the field of the fundamental mode of the rectangular patch antenna. The approximation was used to determine the resonant frequencies and resistances as well as the radiation pattern of antennas. Our results were compared with data obtained from different models and from professional full-wave simulators. It was found that the proposed model permitted to design antenna basic parameters with reasonable accuracy - in reasonable time.