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Antennae
Published in Le Nguyen Binh, Wireless And Guided Wave Electromagnetics, 2017
In practice the antennae need to be installed in a place that is sufficiently high for telecommunications and broadcasting, commonly known as antennae towers. There are a number of basic antenna structures, such as the dipole antenna, which is a simple structure constructed by two straight wires in opposite phase end-toend, directional antennae. Alternatively, a beam antenna radiates greater energy/ power directed toward some specific directions. A horn antenna is a type of directional antenna whose shape follows that of a horn. A meta-material antenna is a class of antenna incorporating meta-materials to enhance the performance of miniature antenna systems. An omnidirectional antenna is an antenna system radiating EM waves uniformly in all directions in one plane. A parabolic antenna has a radiating or reception area that follows the shape of a parabola in one or both planes. A typical parabolic antenna disk is shown in Figure 3.1. It is located in a remote area of Western Australia in order to avoid interference from human mobile communication signals so it can detect weak EM radiation from deep space or the outer boundary of the universe. All communications and data transfer works are implemented via fiber optical communication lines and systems.
Alternatives to Metamaterial Based Antennas for Gain and Bandwidth Enhancement
Published in IETE Journal of Research, 2023
Ankit Nimbolkar, Hemant Kumar, Girish Kumar
The use of wireless devices is significantly increasing. Recent technologies in the form of cellular telephony and wireless local area network (WLAN) especially influence the area of RF wireless communications. Antenna is essential in the form of transmitter and receiver. There is an increase in the demand for high gain and broadband antennas, which can be accommodated in a small space. In the literature, several metamaterial antennas have been reported to achieve high gain and broad bandwidth. In many of these configurations, a metamaterial superstrate is kept above a microstrip antenna (MSA) to obtain either high gain or broad bandwidth or both [1–6]. In [1], a three-layer metamaterial structure is used as the superstrate for gain enhancement. In [2], a single layer structure with near zero refractive index is designed, which enhances both the gain and bandwidth. In [3,4], partially reflecting surface, which is a doubly periodic array of complementary cross elements, is proposed for gain enhancement. In [5], a frequency selective surface is used as a superstrate, which consists of a 3 × 3 array, and provides a gain of 14 dBi. In [6], a single layer superstrate consisting of 5 × 5 array of double annular slot resonators is used to achieve the peak measured gain of 16.35 dBi with an impedance bandwidth of approximately 3% for |S11| ≤ −10 dB. However, the design and fabrication of these antennas are complex. Also, in these papers, the high gain is achieved at the cost of either less impedance bandwidth or larger size as compared to conventional antennas. Another challenge is to obtain a good low loss homogeneous metamaterial, which is difficult to physically realize [7]. Therefore, it is difficult to use these metamaterial antennas in commercial applications like cellular phones, Wi-Fi routers, etc.
A new wideband CP antenna with a single-layer metasurface
Published in Electromagnetics, 2022
In past years, metasurface (MT) antennas, as a new kind of metamaterial-antenna, are becoming very attractive due to their outstanding features of broad bandwidth and low-profile (Caloz and Itoh 2005; Engheta and Ziolkowski 2006; Holloway et al. 2012, 2012). In general, an MT is arranged at above a linearly polarized (LP) radiator to convert the LP wave into a circularly polarized (CP) wave. Recently, various of MTs were introduced into the broadband CP antennas (Agarwal and Alphones 2013; Agarwal et al. 2013; Bernard, Chertier, and Sauleau 2011; Huang et al. 2016; Kandasamy et al. 2015; Li et al. 2015; Nakamura and Fukusako 2011; Nasimuddin, Ning Chen, and Qing 2016; Ta and Park 2015, 2016; Yuan et al. 2019; Zhao et al. 2016; Zhu et al. 2013, 2014), for instance a square ring with a diagonal (Zhu et al. 2013), a rectangular patch (Zhao et al. 2016), a slotted patch (Li et al. 2015), or a cross-slotted patch (Kandasamy et al. 2015), and a cut-corner square patch (Huang et al. 2016; Ta and Park 2015, 2016; Zhu et al. 2014). Aside from changing the shapes of MTs, different LP radiators are often used to enhance the bandwidth of the CP antennas (Agarwal and Alphones 2013; Agarwal et al. 2013; Bernard, Chertier, and Sauleau 2011; Nakamura and Fukusako 2011; Nasimuddin, Ning Chen, and Qing 2016). In (Bernard, Chertier, and Sauleau 2011), a diagonal-slot square patch was used to drive the optimized metamaterial-inspired reactive impedance substrate to obtain a wide 15% of circularly polarized bandwidth (CPBW). Similarly, a truncated-corner square patch (Nakamura and Fukusako 2011) and a slotted patch (Nasimuddin, Ning Chen, and Qing 2016) are used to drive the artificial ground structure and 7 × 7 rectangular-ring units, which can realize wide 3-dB axial ratio bandwidth (ARBW) of 20.4% and 28.3%, respectively. In addition, aperture antennas backed by MT reflectors (Agarwal and Alphones 2013; Agarwal et al. 2013) were also developed to achieve wide CPBW greater than 20%.