A modal current correlation approach for designing dual-frequency slotted cavity antennas

Slotted metallic waveguide and cavity antennas are widely used for microwave and higher frequencies, mainly due to their simple construction and low loss nature. These antennas provide good radiation characteristics for communications and radar applications, but their single, narrow bandwidth is a restriction. A few dual-band antennas utilizing metal waveguide structures can be found in the literature, but they sacrifice the structural simplicity of the single mode configuration. We present a new design method to arrive at a dual-frequency design which can preserve the simple construction of single band cavities. The method is based on the correlation between the modal surface currents in the metallic cavity. Numerical results show promising outcomes for an example of a rectangular cavity structure. This method could be applied to other common waveguide structures for circular or cylindrical antennas.