Low-Profile Two-Port MIMO Terminal Antenna for Low LTE Bands with Wideband Multimodal Excitation

2020-04-02T15:29:06Z (GMT) by Hanieh Aliakbari Buon Kiong Lau
It is challenging to design multiple-input multiple-output (MIMO) terminal antennas for LTE bands below 1 GHz, due to the conventional chassis offering only one resonant characteristic mode. Recently, it was shown that minor structural changes can yield additional resonant mode(s), which were used to design two-port MIMO antennas. However, the resulting bandwidth for the second port does not cover the low LTE bands. Herein, a new approach to structural changes and feed design is proposed for the design of a low profile (4 mm) two-port MIMO antenna that covers all common low LTE bands (0.75-0.96 GHz) with total efficiency of above 67%. The large symmetric bandwidth (25%) is achieved using three additional resonant modes obtained by structural changes as well as two simple probe-feed ports jointly exciting weighted combinations of the four modes over frequency. The envelope correlation coefficient of below 0.15 is facilitated by the different phase shifts of the characteristic electric fields at the port locations. Moreover, the design requires no ground clearance, no decoupling structure and the two ports are separated by only 0.2 wavelength. Finally, to show design flexibility, a third antenna is added to the top of the chassis to create a three-port MIMO antenna