According to the equation (1) of the characteristic impedance of a bow tie antenna, a greater flare angle ( α) can indirectly reduce the capacitance, thereby increasing the input impedance.
However, this will also increase the input impedance of the radiation plate, and we found that the angle of the radiation plate is large. This is conducive to electromagnetic radiation moving outward to avoid the energy that is bounded in the antenna. Due to the structure of antenna, because there is no reflector on the back of the radiator plate, the radiation plate capacitance is small. When the S 11 parameter <-9 dB for the passband, the relative bandwidth can reach more than 90%, while the general antenna broadband is only up to 10%. The structure of a double bow tie antenna.įig. By adjusting the above parameters, the antenna's bandwidth is maximized, and a standard 50 Ω SMA coaxial connector is used for connection. The first section of the impedance transformer has a length of 10 mm and a width of 2.6 mm, the second section has a length of 36 mm and a width of 3.5 mm, and the third section has a length of 36 mm and a width of 4.1 mm. The feeder is symmetrical with a three-section impedance transformer. As shown in Figure 1, the size of the radiation film is 148 mm x 64 mm x 94 mm. The radiation film and feeder are both 0.03 mm thick copper. We designed the antenna's radiation plate and feeder on both sides of the substrate. The FR-4 substrate ( ε r = 4, tan δ = 0.025) has a length of 220 mm, a width of 168 mm, and a thickness of 1.6 mm. The design of the double bow tie antenna is shown in Fig. Single-negative material with an operating frequency of approximately 1 GHz is loaded into the antennas to improve their directivity and gain. These ultra-wideband antennas have an operating frequency of 0.5 GHz-1.2 GHz. This paper assesses the application of electromagnetic metamaterials in the new GPR antennas. But issues remain, as the antenna gain is not high and the directionality is inaccurate and affects the GPR performance. These solve the problem of antenna practicality of the traditional ground-penetrating radar (GPR), which is low because of its excessive size, expensive cost, and insufficient bandwidth. These promote the miniaturization of the antenna size, reduce the surface wave interference, and improve the radiation characteristics.īow tie antennas have many advantages, including light weight, easy design and fabrication, better symmetry in radiation, planar structure, and compact size among other factors. Loaded hyper-surface antennas include electromagnetic band gap structured (EBG) and reactive impedance surface (RIS) antennas. Meta-resonator antennas include those based on split-ring resonators (SRRs) and complementary split-ring resonator antennas (CSRRs). Micro-antennas based on metamaterial loading include negative permeability metamaterials, high-permeability shells, magnetic photonic crystals (MPC), and Ziolkowski's proposed near-field resonant parasitic antennas.
Resonant antennas based on a composite right/left-handed (CRLH) or decentralized design include negative- and zero-order resonant antennas. The current small antennas based on metamaterials have been extensively studied. The metamaterials loading on the antenna can result in antenna miniaturization, wide passband, high gain, and other functions. Metamaterials have been widely used in various fields such as various special antenna designs, optical imaging, electromagnetic wave stealth, subwavelength waveguide devices, leaky wave elements, and many others. These artificial materials are not present in nature.
These include left-handed materials, zero-refraction materials, single-negative materials, right/left-hand transmission lines, and photonic crystals, among others. Metamaterials are a type of new artificial electromagnetic material.
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