In this paper, a new frequency tunable filtering-antenna (so-called filtenna) is inspired by a Defected Ground Structure (DGS) band-pass filter for the fifth generation picocell base stations. It is intended for use in Cognitive Radio (CR) communications within the European Union Sub-6 GHz spectrum, which ranges between 3.4 and 3.8 GHz. Firstly, a Wideband (WB) monopole antenna is proposed where the operational frequencies cover 3.15-4.19 GHz, taking the 10-dB return loss level as a threshold. A band-pass filter of a Semi-Square Semi-Circle shape is integrated into the WB antenna ground to obtain the communicating filtenna. The narrowband frequency tunability is achieved by changing two varactor diode capacitances located in the filter slots. The antenna is prototyped occupying a total space of 60 × 80 × 0.77 mm 3 , then tested to verify the simulated results. Three operating frequencies 3.4, 3.6, and 3.8 GHz of the filtenna are studied in terms of return loss, realized gain, and radiation patterns which verify that the frequency shift has almost no effect on the antenna performance. The filtenna has a maximum gain of 4.5 dBi in measurements and 3.47 dBi in simulations. The obtained results have proved their efficiency for CR communications.
The present paper describes a novel planar antenna based on the fractal structure designed for Ultra-Wide Band (UWB) applications. The antenna exceeds the UWB band by covering the frequency range between 7.36 and 19.57 GHz with S11 < -10 dB (the fractional bandwidth is 90.68 %) which involves four applications, the C-band (4-8 GHz), the X-band (8-12 GHz), the Ku-band (12-18 GHz) and the K-band (18-26.5 GHz). The low-cost Rogers RO4003C substrate is employed to print the proposed antenna in a small dimension of 12 x 16.9 x 0.81 mm3. This antenna is invented from the shape of a flower with three elliptical leaves. The antenna simulated radiation efficiency is greater than 97 % with an omnidirectional radiation pattern in the E-plane and a bidirectional radiation pattern in the H-plane, across the entire bandwidth. The maximum realized gain of the proposed antenna is about 5.25 dBi. Therefore, the obtained results demonstrated that the flower-shaped antenna is a good candidate for practical UWB 5G applications.
In this study, a novel Switched Beam Antenna (SBA) system is proposed and experimentally validated for C-band applications. The system is made up of a 4 × 4 Butler matrix, whose outputs are connected to four square-looped radiator antenna elements. The originality of the proposed work depends on the construction of a miniaturized beamforming network with minimal complexity, low loss, and low expense. Moreover, designing a system with a broad frequency range enables its use in a variety of applications. Miniaturization is achieved by eliminating the crossover and integrating the 45 • shifter into the 90 • hybrid coupler, as well as tilting the antenna array (i.e., making the Butler matrix output and the feed line of the antenna element orthogonal). The simulated results of the phase difference between the suggested Butler matrix outputs closely match the −45 • -135 • theoretical calculations. The SBA measured results show a wide bandwidth and low insertion loss of 63.64% (4.21-8.14 GHz) and −4.89 dB, respectively. Four orthogonal beams are produced by the proposed structure's input ports 1-4 when they are excited. These beams are aligned at angles of −10 • , 60 • , −60 • , and 10 • at 5.7 GHz.
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