A Shared-Radiator Copolarized Antenna for Full- Duplex Communication in 5G <i>n</i> 78 Band

In this letter, a colinearly polarized in-band full-duplex antenna for the partial 5G <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i>78 band is presented that employs a shared-radiator for its transmitter and receiver. To meet the desired wide impedance bandwidth, two half modes of rectangular microstrip patch antenna (MPA), namely TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,0</sub> and TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,1</sub>, are stimulated in a close proximity. The excitation of these half modes of an MPA ensures the compactness of the proposed design. Further, to achieve good inter-port isolation over the desired wideband, two symmetrically placed circular stubs along with two long strips are employed. The measured result of a fabricated prototype shows that the proposed full-duplex antenna provides an inter-port isolation better than 22 dB over the entire impedance bandwidth (|<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub>|, |<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sub>| ≤ −10 dB) of 3.33 GHz to 3.69 GHz. Moreover, this antenna not only covers the partial range of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i>78 band but also successfully suppresses the higher-order modes present in the sub-6 GHz bands of the 5G spectrum.