In multi-band base station antennas, interference toward neighboring cells at low operating frequency in-creases since tilting angle is frequency-independent and beamwidth in the vertical plane increases as de-creasing the operating frequency. In this paper, the realization of the different phase shifts at each frequency is proposed by using the dispersion relation of the composite right/left-handed transmission line. The feasi-bility of the phase shift is clarified by using equivalent circuit model of the unit cell. Next, the dispersion and Bloch impedance of the actual configuration of the unit cell are designed. The inverse phase shift at each frequency is verified experimentally.
Design of composite right/left-handed transmission line for phase shifter of multi-band base station antenna