FD-TD analysis of a strip dipole with window fed by stripline

Many types of circularly polarized printed antennas have been studied and developed. CP-PASS is a type of series-fed arrays, and the feed loss is smaller than that of corporate-fed arrays. The basic element for circular polarization consists of a strip dipole and a slot. They are fed in series by a microstrip line, and can produce circular polarization in the broadside direction. The advantages of this antenna are the simplicity of the element and feed line, the compatibility with integrated circuit, etc. However, the structural simplicity makes the design difficult, and the design parameters were determined experimentally. The authors show a strip dipole fed by the stripline, as a part of CP-PASS. A window is cut behind to increase the bandwidth, and a probe, a small strip, couples to both the feed line and the strip dipole to reduce the spurious radiation from the window. But it is very difficult to determine the optimum length of the probe by the experiments. It also makes the design difficult as a parallel plate mode is generated when fed by the stripline. The present authors calculate the parallel plate mode generated from the strip dipole with the window by using the FD-TD method, and examine the effect of the parameters of the probe on the parallel plate mode.<>