Antenna Miniaturization and Bandwidth Enhancement Using a Reactive Impedance Substrate

Abstract

Abstract-The concept of a novel reactive impedance surface (RIS) as a substrate for planar antennas, that can miniaturize the size and significantly enhance both the bandwidth and the radiation characteristics of an antenna is introduced. Using the exact image formulation for the fields of elementary sources above impedance surfaces, it is shown that a purely reactive impedance plane with a specific surface reactance can minimize the interaction between the elementary source and its image in the RIS substrate. An RIS can be tuned anywhere between perfectly electric and magnetic conductor (PEC and PMC) surfaces offering a property to achieve the optimal bandwidth and miniaturization factor. It is demonstrated that RIS can provide performance superior to PMC when used as substrate for antennas. The RIS substrate is designed utilizing two-dimensional periodic printed metallic patches on a metal-backed high dielectric material. A simplified circuit model describing the physical phenomenon of the periodic surface is developed for simple analysis and design of the RIS substrate. Also a finite-difference time-domain (FDTD) full-wave analysis in conjunction with periodic boundary conditions and perfectly matched layer walls is applied to provide comprehensive study and analysis of complex antennas on such substrates. Examples of different planar antennas including dipole and patch antennas on RIS are considered, and their characteristics are compared with those obtained from the same antennas over PEC and PMC. The simulations compare very well with measured results obtained from a prototype 10 miniaturized patch antenna fabricated on an RIS substrate. This antenna shows measured relative bandwidth, gain, and radiation efficiency of = 6 7%, = 4 5 dBi, and = 90%, respectively, which constitutes the highest bandwidth, gain, and efficiency for such a small size thin planar antenna.

A Novel Design of Patch Antenna Loaded with Complementary Split-Ring Resonator and L- Shape Slot for (WiMAX/WLAN) Applications

“…There are many antenna configurations and techniques proposed to achieve dual-band or multi-band characteristics for (WLAN/WiMAX) applications such as the ring patch antenna [4][5], the monopole antennas [6], the slot antennas [7]. Recently, researchers have focused on using metamaterial concept in performance enhancement as well as miniaturization of the microstrip antennas [8][9]. Complementary split ring resonators (CSRRs) are metamaterials that can achieve negative dielectric constant (ɛ) [10].…”

A low profile folded dipole antenna on a reactive high impedance substrate

“…The equivalent circuit developed above can be applied to the design of a low profile antenna consisting of a dipole located on top of a reactive high impedance substrate [8]. The high impedance exhibited by the artificial substrate permits to locate the metallic dipole very close to the surface itself without inhibition of the dipole radiation.…”

A Circularly-Polarized Compact Wideband Patch Antenna Loaded by Metamaterial Structures

“…Various techniques have been introduced for size reduction of MPAs such as using shorting pins and shorting plates, utilizing fractal antennas, cutting slots in the radiating element [3][4][5][6]. In addition to these methods, loading the antenna by metamaterial structures, including split ring resonator (SRR) and CSRR, provides new ways to achieve higher level of size reduction [7][8][9][10]. Dimensions of metaresonators, such as CSRR, are much smaller than the operating wavelength of the antenna which makes it a good candidate for miniaturization [11].…”