Probe and line-fed cylindrical microstrip antennas with complex-shaped patches

Cylindrical microstrip antennas (CMAs) with complex-shaped patches are analyzed by the moment method in the spectral domain. The structures are fed by a probe as well as by a cylindrical microstrip line. The asymptote extraction technique for the spectral Green´s function is applied to increase the calculation efficiency not only for elements of the impedance coupling matrix but also for the elements of the voltage vector produced by the probe. Different shapes of parches are discussed: in particular U-shaped patches, patches with slots and notches, and coupled looped patches. The return loss for the probe and line fed CMA are presented. The shift of the resonant frequency of the CMA is analyzed with respect to the resonant frequency of the CMA having a traditional cylindrical rectangular patch. For the line-fed CMA with two pairs of coupled loop patches an H-polarized omnidirectional radiation pattern in the azimuthal plane has been reached.