A Digital Multibeam Array With Wide Scanning Angle and Enhanced Beam Gain for Millimeter-Wave Massive MIMO Applications

A novel full-digital multibeam array with wide scanning angle and enhanced beam gain is proposed for millimeter-wave massive multiple-input multiple-output applications. The array consists of 16 dual exponentially tapered slot antenna (DETSA) elements. Each element is integrated with a radio frequency receiver, an intermediate frequency chain, and an analog-to-digital converter (ADC). The H-plane radiation pattern of the proposed DETSA is very wide to enable the beam scanning in the azimuth plane. The beam gain is further enhanced by employing a 1-D multilayered planar lens that transforms the spherical wave into a plane wave in the E-plane for increasing the beam gain and keeping the phase compensation unaltered in the H-plane. Meanwhile, the planar lens is optimized to guarantee the wide scanning angle. In addition, all the signals received by the 16 independent channels are converted to a digital signal via ADC simultaneously and then used for synthesizing the multibeam patterns in the digital domain. Furthermore, the calibration and the verification of the synthesizing weights are discussed in detail. The measured results show that a scanning coverage of ±40° in the H-plane (or in horizontal plane) and an estimated maximum gain of 24.8 dBi with a gain tolerance of 3 dB can be achieved by the proposed 16-element array with a 1-D lens.