Mm-Wave Beam-Steerable Endfire Array Embedded in a Slotted Metal-Frame LTE Antenna

In this article, a new principle to overcome the blockage of metallic frames in mobile terminals to endfire millimeter-wave (mm-wave) arrays is proposed. The obstruction is solved by etching several slots in the top part of the frame. It is shown that the slots in the handset frame can further enhance the beam-steering gain of a mm-wave bow-tie array. A very small array-frame distance can also be realized without degrading much the array performance. Several considerations in the slot design are assessed first. A prototype of the PCB and frame has been built and the results show that the array is matched in the desired frequency bands of 24.25-27.5 and 27.5-28.35 GHz. The mm-wave array can scan 80° in the endfire direction, and the realized gain obtained is higher than 7 dBi in the operating frequency bands. At the same time, the frame performs as a sub-3 GHz dual-loop antenna. The covered bands are 760-980 and 1240-2870 MHz.