The phase center position of a microstrip horn radiating in an infinite parallel-plate waveguide

In this paper the field radiated by a flared microstrip line in an infinite parallel-plate waveguide with separation between plates of less than half a wavelength is studied. The field at any point of the parallel-plate waveguide is expressed as a summation of modal solutions of the Helmholtz equation. The phase center of the microstrip horn is calculated for uniform amplitude distributions along the horn aperture. The theory may be applied to obtain the phase and amplitude distributions along the output ports of microstrip bootlace lenses