Broadband Electromagnetic-Transparent Antenna and Its Application to Aperture-Shared Dual-Band Base Station Array

In this article, a broadband electromagnetic (EM)-transparent element is proposed for aperture-shared dual-band base station array application. The array consists of the proposed low-band (LB) transparent element and a $4\times $ 4 broadband antenna array operating at high-band (HB). The LB radiator is a dual-polarized dipole, loaded with dielectric blocks both on the top and bottom sides. The LB element is placed right above the center of HB array. Since the dielectric-loaded radiator achieves broadband transparent characteristics in HB, the HB array can radiate with almost no blockage from the LB element. The mechanism of the characteristics is studied by using an equivalent circuit. Experimental results show that the blockage effect of the LB radiator on the broadband HB element is reduced by loading dielectric blocks. For verification, a dual-band antenna array operating at 0.76–1.03 GHz and 3.4–5 GHz bands is fabricated and measured. Compared with the isolated HB array, the peak gain deterioration of the aperture-shared array is below 0.8 dB. On the directions within the half-power beamwidth (HPBW), variation of the gain is under 1.8 dB. The results demonstrate that the dielectric-loaded radiator can be used in a multi-band base station array to restore the pattern of a broadband HB array.