A Four-Port Separated Transceiver Antenna with Ultra-Small Frequency Ratio Based on Collocation of Magnetic and Electric Dipoles  

In this communication, a novel four-port separated transceiver antenna with ultra-small frequency ratio for base stations is proposed. The antenna is realized by collocating two orthogonally crossed slots and two dipole arrays. We first discuss the operating mechanism of the collocated antenna, i.e., a collocated couple of an electric dipole and a magnetic dipole has inherent property of isolation. Then, a prototype with an ultra-small frequency ratio is designed to verify this concept and illustrate the design method. Artificial magnetic conductors (AMC) reflector and electromagnetic band gap (EBG) structure is combined with crossed slots to realize the magnetic dipoles with broadside radiation patterns and suppression of surface wave. AMC reflector is also integrated with the electric dipole arrays to reduce the profile and enhance the broadside gains. The proposed antenna operates in 1.71-1.78 GHz frequency band by the crossed slots and in 2.11-2.18 GHz frequency band by the dipoles, representing AWS (Advanced Wireless Service) band. The frequency ratio is only 1.23, and the couplings are lower than -15 dB in the operating band without any decoupling network. The proposed design concept and method give a competitive design solution for separated transceiver antennas in base stations.