Improved empirical model for the Jerusalem cross

The frequency transmission characteristics of Jerusalem cross grids at oblique angles of incidence are investigated experimentally, and an improved equivalent circuit model for the cross is proposed. Particular attention is given to the properties of the upper resonant frequency band and its application to dichroic reflector antennas. This upper resonance is essentially dipole in nature, changing in frequency as the angle of incidence is varied. It occurs at a higher frequency than expected and is influenced not only by the length of the end caps but also by the mutual reactance between the end caps and the main arm of the cross. An equivalent circuit model for the cross is presented, which more closely matches the observed responses than previous models. Experimental results for a complementary Jerusalem cross grid are also discussed.