Model for the analysis of microstrip cylindrical antennas: efficient calculation of the necessary Green´s functions

Conformal antennas are of great interest, because there are lots of applications which require non-planar surfaces and therefore non-planar substrates, for example circular ones. To analyse such structures corresponding rigorous theoretical approaches should be developed. Because of the more complex geometry conformal antennas are less investigated than planar ones. However in general the lines of reasoning may be very similar. Here we follow an approach that was proposed and successfully realised for planar multilayer antennas. The main idea of this approach is to solve the problem in the spatial domain. This line of strategy is realised for circular microstrip patch antennas. In this paper the problem of a patch microstrip antenna printed on a circular metal-dielectric substrate (circular metal rod coated by a dielectric layer) is discussed. Mixed-potential integral equations for the electric field are constructed. These equations contain spatial Green´s functions for sheet electric currents and they can be solved using the moment method. In order to realise the proposed scheme we should be able to calculate spatial Green´s functions very efficiently. This is really a key point of the problem, which is successfully solved in this paper