ABSTRACT
This
paper, presents a 4×4 BM based on four direction switch BM antenna
array. The proposed design operated at 3.5 GHz. The use of multi-beam
antennas or switched-beam antenna arrays (SAAs) promised users of
high-gain and large coverage areas for 5G technologies. The BM was
implemented by combining 3-dB BLC, two crossovers, and
45o phase shifters fabricated on the RT5880LZ
substrate, with using a triangular slot and T-shape based on the BM
design. The proposed design focused on the miniaturization and
enhancement of the bandwidth. The return loss and isolation were better
than -15 dB at all the ports, according to the simulated and measured
result showed that with excellent insertion loss -6.1 ± 2 dB. A
fractional bandwidth of 49.7% and the overall dimension were reduced to
56% as compared to the conventional BLC and crossover. Hence, the
proposed design of BM performed an excellent size reduction of 80% and
improvement bandwidth up to 836 MHz compared to the traditional BM. The
switched beam directions were measured at -34o,
-40o, +32o and
+35o at 3.5 GHz for each input port of 1-4 excitation.
The proposed design BM is suitable of 5G application.
Keyword:Beamforing,
Butler matrix, antenna array, 5G, triangular slot, T-shape, branch line
coupler (BLC), microstrip antenna, antenna array.
IntroductionThe demand for wireless technology is substantially increasing because
of the rapid growth of wireless technological innovations. Currently,
several billion wireless-electronic devices are linked to the internet
network, and these figures are expected to rise in the coming years.
So, researchers have started to put tremendous effort in the area of
5G technology[1][2][3]. The deployment of 5G wireless, as
well as the current and upcoming Beyond 5G (B5G) communication system,
point towards a revolutionary change in modern-day telecommunications,
leading to a complete paradigm shift in the way end-users will
communicate in the coming years [4][5]. Meanwhile, the number
of co-channel interference users will increase and improve the
inferior quality of service [6][7]. In the development of 5G
systems, it is envisaged that switched-beam antenna arrays (SAAs)
would play a vital role in obtaining the desired performance at the
transceivers. This is the main objective sought by many researchers in
the area of beam-forming network. Their focuses have always been on
the problem and quality enhancement of the communication link [8].
Hence, the application of switch beam-forming networks (SBFNs) has
always been the area of interest among researchers[9]. This
technology significantly contributes to wider bandwidth and
directional antenna array that can transfer and focus radiated power
in the desired direction. It is widely applied in wireless
communications [4]. The SBFNs are categorised into several types,
such as Nolen matrix [10], Blass matrix [11], Rotman lens
[12], and Butler matrix [13]. Butler matrix or BM is a popular
technique due to its low cost, simple configuration, and low power
dissipation. This technique is widely used in the filed beam-forming
of antenna array [14]. BM is a passive device with multiple input
and output ports. BM 4×4 consists of four 3-dB directional coupler,
two phase shifters, and a crossover [15]. The beam-forming and
beam-steering procedures are controlled by the BM design employing an
antenna array. The signal-to-noise and clutter ratio is improved by
the BM design’s usage of frequency reuse [16]. In the last years,
the BM 4×4 has been studied and improved in different ways, such as in
[17] and for low loss [18]. The problem with conventional BM
large size and narrow-band characteristics [19][20] is that
these requirements are unable to meet the fifth generation (5G)
application. However, to solve this issue, researchers have started to
introduce a new design using many techniques to improve the Butler
matrix[21]. The reported literature [22][23][24]
has
highlighted microstrip
artificial
transmission lines (ATLs) triangular slot, BM without crossover and
phase shifter, and forward wave present in [25]. A reduced BM
network has also been implemented at stub loaded TL, as well as
presented and the multibeam antenna array has been validate. The size
achieved for the Butler matrix was approximately 55% as compared to
the traditional BM design [26]. Another way of using
miniaturisation butler matrix design is through meandered line and
dumbbell-shaped cross-slot technique based on the branch line coupler.
The fractional BW was enhanced up to 37.5% and size miniaturised of
17% [27]. The coupler, crossover, and phase shifter sizes were
reduced by BLC using artificial transmission lines, as in [28].
Recently,
a triangular slot type artificial transmission line (ATL) has also
been proposed. The artificial transmission
line
is, an easy-to-design, compact structure and easy to adjust electrical
parameters, which is also helpful to build block for different
microwave passive components [29]. The proposed 4 × 4 Butler
matrix was design by using software Computer Simulation Technology
(CST). This design utilised modified BLC, respectively. The BM
Implementation was on the
Rogers
RT5880LZ
with 0.25 mm thickness, relative permittivity εr=2, and
loss tangent tan\(\delta\)=0.002. Several BM designs that have been
reported in previous work improved the bandwidth and size reduction.
However, none of them attained bandwidth improvement and size
reduction, together with an excellent performance for 5G beamforming
network. Table 1 displays the specification design of the proposed
designs. The novelty of this paper includes design of the BLC,
crossover and BM by using triangular slot and T-shape structure, and
antenna array based zig-zag shape.Table 1. Specification of proposes designs.