Impedance and polarization characteristics of "H" and "IHI" slot antennas

We have seen an increase in interest in end loaded slot antennas for the purpose of reducing size of the slot antenna without changing the resonant frequency. Such antennas allow lower back radiation in slot coupled patch applications. They also are suitable for large scanning angle phased arrays in which the inter-element spacing must be smaller than is permissible with conventional slots. Loading sections can also be used to tune slot antennas as shown, or to modify the resonant frequency without changing the length. Due to symmetry, these antennas have no cross-polarization in the E-plane or H-plane. Hence, they have been considered for dual-polarized operation. However, it is important to recognize that there will be some cross-polarization in the D-plane (/spl phi/=45/spl deg/) of slot antennas due to the end loading sections. This paper analyzes the cross-polarization and impedance of the so-called "H" antenna for various end load slot lengths and introduces the "I-HI" antenna. Theoretical and experimental data are also shown.