Novel logarithmically periodic planar antennas for broadband polarization diversity reception

To support the steady increase of standardized frequency bands in mobile transmission systems, the telecommunications industry is being required to develop more compact and wideband air interfaces. In order to suppress the multipath conditioned polarization fading in typical applications of portable radios, primarily antenna modules with polarization-invariant transmission behavior are to be used. Self-complementary, logarithmically periodic antennas serve as suitable representatives for the realization of broadband antenna structures and can be favorably used in polarization diverse transmission systems provided they adhere to a specific geometric structure. Based upon the definition of certain basis geometry functions, log.-per. antennas can be realized with almost arbitrary polarization characteristics over a wide frequency band. In this paper, the trapezoid antenna is introduced as a novel type of log.-per. planar antenna that offers the highest degree of cross-polarization decoupling and the lowest cut off frequency as of all reported log.-per. antennas in the literature.