Abstract
A multibeam array antenna employing a Butler matrix is a promising solution for fifth generation (5G) base stations. Due to inaccurate phase differences between output ports in the Butler matrix, the radiation characteristics could show incorrect main beam directions. In addition, the literature has also reported the issue of high amplitude imbalance in the Butler matrix. This paper presents a single-layer multibeam array antenna fed by an 8×8 Butler matrix operating at 28 GHz for 5G base station applications-a more cost-effective solution for large-scale production. The Butler matrix consists of twelve quadrature hybrids, sixteen crossovers, and eight phase shifters. This circuit was integrated with eight antenna elements at the output ports of the Butler matrix. The proposed multibeam array antenna was fabricated using a low dielectric constant and a low loss tangent substrate. The dimensions of the multibeam array antenna were 88×106×0.254 mm3 . The Butler matrix achieved low insertion losses and low phase error with average values of 2.5 dB and less than ±10 ° at 28 GHz, respectively. The measured return losses were less than -10 dB at 28 GHz. The measured radiation patterns were obtained and eight main beams were pointed at ±6 ° , ±18 ° , ±30 ° , and ±44 ° with measured gains between 9 dBi and 14 dBi.
Highlights
Research on fifth-generation (5G) mobile communication systems has attracted much interest from researchers and design engineers that wish to cater to the increasing demand for higher data rates and data traffic [1,2,3]
To validate the simulation results, the reflection coefficients of the fabricated multibeam array antenna were measured using a vector network analyzer (Keysight N5224A) and the radiation characteristics were studied in an anechoic chamber
The design of a multibeam array antenna fed by an 8 ×8 Butler matrix based on a single-layer structure operating at 28 GHz was proposed
Summary
Research on fifth-generation (5G) mobile communication systems has attracted much interest from researchers and design engineers that wish to cater to the increasing demand for higher data rates and data traffic [1,2,3]. These efforts have been accelerated to meet the standardization of the International Telecommunications Union Radiocommunication by 2020 [4]. Multibeam array antennas play an important role in enhancing system capacity. This antenna improves network coverage and reduces co-channel interference [5, 8]. To achieve the multibeam characteristic, beamforming circuits such as the Butler matrix, the Rotman lens, and the Blass matrix can be fed to the array
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