An Aperture-Coupled-Cross-Resonator FSS Based Spatial Filtering Patch Antenna Array

The employment of Massive MIMO technology in 5G communication results in a large number of RF channels in the base station. Therefore, the base station will suffer from the huge burden of equipping discrete bandpass filters under the traditional filtering strategy. An alternative filtering strategy called spatial filtering characterizes direct covering frequency selective surface (FSS) on multi-channel antenna array of base station and is expected to greatly relax the need for discrete bandpass filters. An aperture-coupled-cross-resonator (ACCR) FSS based spatial filtering scheme is investigated in this study. A low-profile spatial filtering patch array (LPSFPA) with thickness of
$0.07\lambda _{0}$
and operating around 3.6GHz is constructed by placing an asymmetrical ACCR FSS tightly upon a patch antenna array with a half-period lateral shift. A good out-of-band suppression at both band-edges and enhanced in-band impedance bandwidth are achieved when the main beam is scanned with an elevation angle range of 0° to 30° and arbitrary azimuth angle. To verify the design, a finite LPSFPA sample whose main beam can be directed to
$\theta _{\mathrm {b}}= 0^{\mathrm {\circ }}$
,
$15^{\mathrm {\circ }}$
and
$30^{\mathrm {\circ }}$
in E plane by different phasing and power-dividing networks is fabricated and tested. The measured results show that the fabricated LPSFPA sample is superior to the ordinary radiation patch array without the ACCR FSS in terms of both the impedance bandwidth and out-of-band suppression for various main beam directions. For the normal-beam case, the measured −10dB impedance bandwidth is from 3.6-3.8 GHz; the measured out-of-band suppression level of peak realized gain is more than 19 dB in the lower band-edge from 3.2-3.5 GHz and 17 dB in the upper band-edge from 3.9-4.2 GHz. The proposed spatial filtering scheme has no negative influence on the radiation performance of the radiation patch array.