Quasi-binomial series-fed array for performance improvement of millimeter-wave antenna for 5G MIMO applications

A quad-port MIMO antenna based on a quasi-binomial series-fed array is presented in this paper for n257 and n258 millimeter-wave applications with an investigation of additional loaded patches on performance enhancement of the conventional binomial series-fed array. The single element of the proposed MIMO is a 3 x 3 element planar binomial series-fed array whose width of the radiating elements is tapered to achieve the binomial distribution. From both simulated and tested results, it is observed that a wider bandwidth (S-11 < -10 dB of 21.78 %), high peak gain (12.4 dBi), and high radiation efficiency (92 %) with side lobe level (SLL) reduction of more than 9 dB are achieved by additional loaded patches. This design approach does not only offer wider bandwidth, low SLL, and gain increment, but also ensures the excellent diversity performances of the very closely spaced (0.116 lambda) MIMO antenna, without utilizing any additional decoupling structure. The proposed MIMO antenna system offers impedance bandwidth (S-11 < - 10 dB) from 24.6 GHz to 30.59 GHz, isolation > 27 dB, envelope correlation coefficient < 0.0002, diversity gain > 9.99 dB, and mean effective gain between -4 dB and -8 dB. Owing to its performance attributes, the proposed antenna is an excellent choice for 5G millimeterwave communication devices, including but not limited to enormous IoT, smart cities, and virtual reality.