The use of reactive loading for dual-band circularly polarized characteristics in microstrip antennas

A diagonal-fed rectangular microstrip antenna is reactively loaded to produce a dual-band circularly polarized radiator. The impedance locus demonstrates the dual-band behavior of the radiator. The impedances at the two bands are less than the impedance of the unloaded structure. The axial ratio at broadside for each of the bands is about the same as the variation that resulted from the unloaded radiator (about 2 dB). There is an apparent asymmetry in a radiation pattern. This undesirable effect could be due to the method used to load the radiator, in which case it would be reduced somewhat if true monolithic loads were used.<>