Dual-Polarized Wideband Dipole Filtenna Using a CMRC Radiator Structure

This letter proposes a wideband dual-polarized dipole filtering antenna (filtenna) employing a compact microstrip resonating cell (CMRC) radiator structure. The CMRC structure is a special microstrip line structure with a specific pattern etched on it. At resonant frequencies, the cell displays a bandstop performance, forming a lowpass-type filter. Inspired by this, the traditional dipole antenna radiator is first modified as a CMRC structure to obtain low-pass filtering radiation performance. Then, a balun-fed structure is used to realize highpass-type filtering performance with a lower band controllable radiation zero. The operating mechanism of this zero is revealed by analyzing a CDA excited through the perfect differential signal. Thus, bandpass filtering radiation performance is obtained. To enhance the selectivity at the passband edges, four coplanar split loops are coupled to the antenna radiator. For the exhibition, a filtenna prototype is presented, processed and tested. Tested results display that the presented filtenna has a 57.8% (<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> and <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 within 3.2 GHz to 5.8 GHz) impedance bandwidth and a 7.5 dBi average passband gain. Three radiation nulls and 19 dB suppression levels of the out-of-bands are obtained. These advantages make the presented filtenna a great option for 5G base station (cover 5G <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i>78/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i>79 bands) applications.