Uncovered leakage phenomenon in H-guide slot antenna

The moment method is applied to analyze the characteristics of a transverse slot in the upper plate of an H-guide operating in the dominant mode. Entire basis functions and testing functions are used with the wall thickness taken into consideration. Unlike the closed rectangular waveguide-fed slot, however, a fundamental radiation phenomenon due to the open property of the guiding structure, which has not been noticed before, is observed theoretically. The propagation direction of the new radiation mode is found to cover the whole angular spectrum in the plane parallel to the electric conductor. An explanation to the physical existence of the new radiation phenomenon is given clearly. Also an efficient method is developed to determine its angular power density in detail. Numerical computation shows that the energy carried by the new radiation mode is significant when the slot is near resonance.