Multi-beam Base Station Research Articles

Multibeam Array Antenna with Compact Size Butler Matrix for Millimeter-Wave Application

New radio wave technologies of millimeter-wave (mmWave), compact cell size, and multi beam base station are introduced with the recent development of the 5G mobile system. The Butler Matrix (BM) feed circuit is the most preferable candidate for the 5G mobile system since it can achieve multi beam radiationpatterns at the array antenna, provide structural compactness and produce good multi beams.The BM circuit is typically built on a single dielectric substrate. However, in this single-substrate structure, the micro strip line connecting several circuit elements in the BM spans over a large area, resulting in significant feeding loss in the millimeter frequency band.In this study, a compact size circuit configuration of BM is proposed, where the original single-substrate structure is modified into a two-substrate stacking structure. The via-hole is designed to connect the two substrates with minimal path loss. The BM is built for the 28 GHz band with four inputs and four outputs.The phase delay is optimized using via-hole to produce the phase difference of ±45º and ±135º. The coupling for the hybrid is -3 dB, while the transmission coefficient of -6 ± 3 is achieved from the BM structure and, the return loss (Sii) for both input and output ports are less than -10 dB. The two-substrate BM is combined with the rectangular patch antenna and the via-hole patch antenna in a planar configuration of 0.5 λ0spacing to obtain the radiation patterns. When the Port 1 through Port 4 of the BM are fed, four beams are created, with peak gains of 11.2 dBi, 9.87 dBi, 10.2 dBi, and 11.7 dBi, respectively, towards +16°, -35°, +39°, and -12°. The analysis includes the radiation performance from the ideal value and from the BM input. Three-dimensional representations of good multibeam radiation patterns are obtained after each input signal of the BM is fed

Cylindrical Dielectric Lens Antenna for 5G Mobile Base Station

Abstract A wide range new technologies such as millimetre wave, massive MIMO technology, multi beam base station antenna are required in the fifth-generation (5G) mobile system. For multi beam base station application, a dielectric lens antenna is selected due to capabilities of achieving excellent radiation patterns in a wide angular range by applying the lens shaping method. A cylindrical structure is suitable for a lens antenna installation on the base station pole. In this paper, a cylindrical dielectric lens antenna is proposed and multi beam radiation patterns are investigated through the calculations by an electromagnetic simulator (FEKO) at the operating frequency of 28 GHz. As a result, good multi beam radiation patterns are achieved in the scanning angle from 0°to 30° with total gain reduction around 5dBi and antenna efficiency of about 95.9%.

Compact Wideband Wide-Angle Polarization-Free Metasurface Lens Antenna Array for Multibeam Base Stations

A compact wideband wide-angle polarization-free metasurface lens (MSL) antenna array is proposed for a multibeam base station operating over the band of 1.71–2.2 GHz. The MSL element comprises of a planar wideband wide-angle polarization-free reflectionless MSL and three feeding sources of ±45° polarized cross-dipole antennas. With the shared lens aperture, the antenna achieves the three beams in the directions of 0° and ±30° in a horizontal plane. A five-layer patch-based metasurface loaded with metal poles are introduced to achieve consistent performance for wide-angle response. To reduce spillover loss, the feeding antennas are loaded with a metasurface and four directors for narrow beamwidth and low profile. With the optimized feeding antennas and MSL, a section of array with $1\,\,\times \,\,4$ MSL elements is prototyped for validation. The measured results show that an impedance bandwidth for return loss ≥ 10 dB is 1.63–2.24 GHz with the isolation larger than 22.3 dB. The measured gain ranges for 0° and 30° beams are 11.8–13.5 and 10–12.2 dBi with the sidelobe levels less than −22.6 and −13.6 dB, respectively.

Performance Analysis of Joint Base-Station Multiantenna Multibeam and Channel Assignment Scheme for Hierarchical Cellular System

Different from the traditional configuration of hierarchical cellular, we introduce the joint base-station multi-antenna multi-beam and channel assignment scheme for hierarchical cellular in this paper. The proposed scheme is based on multi-beam base-station antenna splitting in the elevation-radiating plane, and a dynamic channel allocation scheme by combining the adaptive antenna technologies. Simulation results show that the proposed configuration of the hierarchical cellular can enhance the spectral efficiency remarkably.

Precise Incident Power Density Pattern Measurement through Antenna Pattern Deconvolution

Future cellular and fixed wireless loops (FWL) systems employing highly directive base stations antennas (5 to 8 degrees beamwidth) and moderately directive subscribers' antennas (15 to 25 degrees beamwidth) offer very large capacity due to reduced interference. An important property of the environment of such systems is the interference caused by scattering of the signal from a subscriber transmitter into directions other than the direct line of sight between the subscriber and the base station. In particular, for multibeam base station applications scattering could arrive at the base station in the direction being used by a different beam, resulting in interference that is difficult to reduce by normal nulling techniques. Thus interference can be highly dependent on the incident power density pattern (IPDP) caused by scattering of the signal radiated from the subscriber. We discuss herein the use of a uniformly illuminated array accompanied by electric field deconvolution to measure the crucial IPDP with the same performance as a low sidelobe array of the same size. The mathematical correction technique uses deconvolution of the measured complex electric field pattern with that of the antenna in free space by means of the Fourier Series and limiting the range of Fourier coefficients to those that are not negligible in the free space pattern. Application of the technique to an experimental uniform array with a 2.5 degree azimuthal beamwidth shows the practicality of the deconvolution with real antennas in real environments. The improved resolution and accuracy provided by Taylor weighting versus unweighted deconvolution when trying to measure weak scattered components in the presence of a nearby strong specular component is demonstrated. The IPDP was measured from many sites surrounding a suburban base station. A plot of the cumulative distribution of the ratio of the widely scattered power to that within a prescribed beamwidth summarizes the result of using the deconvolution technique on this experimental data.