Analysis and Design of Dual-Modal Filtenna for Dismountable Aperture-Shared Array
Rong Chao Dai, Sun Shuai, Huafeng Su, Xiu Yin Zhang
Abstract
In multi-band aperture-shared base station arrays, low-band (LB) antennas block the radiation of high-band (HB) antennas, causing cross-band scattering effect and thus degrading HB radiation patterns. Meanwhile, the cross-band mutual coupling between LB and HB antennas deteriorates the port-to-port isolation. In this paper, a LB antenna is proposed to simultaneously suppress cross-band scattering and coupling at HB, which is called a dual-modal filtenna. The LB filtenna comprises slot-etched dipole and capacitive surfaces. It is studied through equivalent circuits operating in two modals, namely spatial modal and self-excited one. In the spatial modal, the LB radiator is illuminated by HB radiated wave and realizes a bandpass filtering response to pass the HB electromagnetic wave. Moreover, in the self-excited modal, the radiator is excited by the fed network and generates a radiation null at HB to improve the out-of-band rejection. On the LB radiator, slots forming parallel resonances are etched to suppress scattering and coupling. However, the suppression frequencies of scattering and coupling can’t simultaneously operate at HB. Then, capacitive surfaces are designed to manipulate the two suppression frequencies to HB. For validation, a dismountable dual-band array is designed. The array consists of the proposed LB (1.7-2.3 GHz) element, a 2×2 HB (2.5-2.7 GHz) array. A frequency-selective surface is placed between them to make the array dismountable. The simulated and measured results show that the HB radiation pattern is rarely affected. Besides, the performance of LB element is maintained. The cross-band isolations are better than 27 dB.