Realization of a Tapered Slot Array as Both Decoupling and Radiating Structure for 4G/5G Wireless Devices

As a combination of microwave Multiple-Input Multiple-Output (MIMO) antenna system and mm-wave antenna array, an integrated design is proposed to provide multi-band, high port isolation, and high gain antenna solution for 4G/5G wireless devices. In this work, an array of tapered slots is used as a decoupling structure at microwave frequency and as an antenna array at mm-wave frequency. The proposed geometry consists of a dual-band monopole MIMO antenna system operating at 4G (2.6 GHz) and 5G (3.5 GHz) sub-6 GHz bands. The wideband port isolation of more than 25 dB is achieved by introducing a tapered slot array structure. One of the key design features is the utilization of these slots as an antenna array with a peak realized gain of 15 dBi at 28 GHz, making this array dual-functional, thus more feasible for compact 4G/5G handheld devices. The proposed design is printed on an RO-5880 substrate with an overall size of 70 mm $\times $ 50 mm $\times $ 0.51 mm. The measured 10-dB impedance matching bandwidth covers two sub-6 GHz bands (from 2.45 GHz to 2.85 GHz and from 3.18 GHz to 3.68 GHz), and the wide mm-wave band from 25 GHz to 30 GHz.