Annular slot antennas have many practical applications because they are low-profile, lightweight, and easy to integrate with printed circuits. This kind of antenna systems may be used quite efficiently as a radiating element for mobile communication systems especially where the volume and size of radiator are crucial parameters. Annular slot antennas are therefore attractive for military applications such as radar systems and satellite communications.
Boundary-value problems of scattering from an annular slot array on a radial waveguide or circular cylindrical cavity are solved rigorously by using the approach of Hankel transform and mode-matching method. Excitation sources are modeled by either a delta electric point source or a coaxial probe located in the center of the radial waveguide or cavity. The Green``s function is used to evaluate electromagnetic wave scattering from delta electric point sources. The scattered fields are expanded in terms of eigenfunctions based on the Fourier series and Hankel transform. Boundary conditions are enforced to constitute a set of simultaneous equations for discrete modal coefficients. A fast convergent series solution is obtained by using residue calculus.
Scattering from a conducting circular cylindrical cavity fed by a coaxial probe of any arbitrary length situated at the center of the cavity is also analyzed. A fast convergent series solution is obtained by utilizing the Fourier transform in conjunction with eigenfucntion expansions, mode-matching, and residue calculus.
Computations and experiments are performed to investigate scattering properties of an annular slot array on a radial waveguide or circular cylindrical cavity in terms of geometrical parameters and frequency. Our theoretical models for scattering from an annular slot array are useful for the analysis and design of annular slot array antennas or bandpass filters.