FDTD analysis and measurement of aperture antennas based on the triplate transmission-line structure

First, two aperture antennas designated as P-type and C-type antennas are a nalyzed using the finite-difference time-domain (FDTD) method. Each antenna is made of a triplate transmission line (TTL), A square aperture is cut ou t of the top plate of the TTL for both antennas to allow radiation, The bot tom of the TTL is a planar plate for the P-type antenna and a plate with a hollow cavity for the C-type antenna. The power how is expressed using Poyn ting vectors. It is revealed that parallel-plate mode power in the TTL is l ower in the C-type antenna, compared with that in the P-type antenna. Secon d, an array antenna composed of two C-type elements is analyzed, The Poynti ng vector distribution in the aperture is found to remain almost unchanged when the element spacing is varied. The input impedance of the array antenn a converges at an element spacing of approximately 0.9 wavelength, The theo retical radiation patterns are in good agreement with measured data.