A microstrip delay line with periodically-loaded shunt inductors for waveguide-fed array antennas

A low-profile planar delay line is proposed for waveguide-fed array antennas. It consists of a compact microstrip line with periodically-loaded inductors, and can realize the same frequency-dispersion characteristics as those of waveguides, resulting in a miniaturization of a waveguide feeding network. The delay line has a similar structure to a composite right/left-handed transmission line, which is one of the latest and hottest topics in RF communities. In our case, though, it is used just as a frequency-dispersive right-handed transmission line.