An Electromagnetic-Transparent Cascade Comb Dipole Antenna for Multi-Band Shared-Aperture Base Station Antenna Array

In multi-band shared-aperture base station antennas, cross-band mutual couplings always lead to unwanted radiation characteristics. In this article, the influence of the cross-band mutual coupling is investigated from the point of view of induced currents and their secondary radiation fields. A low-band (L-band, 0.76–0.88 GHz) cascade comb dipole antenna is proposed to passively cancel the induced current and therefore suppress the secondary radiation field. Owing to the passive current cancellation capability, the proposed L-band cascade comb antenna does not affect the radiation performance of the middle-band (M-band, 1.9–2.7 GHz) and high-band (H-band, 3.3–3.9 GHz) antennas in stacked multi-band shared-aperture antenna arrays. The proposed L-band antennas are thus electromagnetic-transparent to the M- and H-band antennas. Based on the novel electromagnetic-transparent cascade comb dipole antenna, a triple-band shared-aperture antenna array that consists of the L-, M-, and H-band antennas are developed, manufactured, and measured. Both simulated and measured results validate the attractive features of the cascade comb dipole antenna in multi-band shared-aperture massive MIMO base station antenna array developments.