Hussein Attia

Enhanced-Gain Microstrip Antenna Using Engineered Magnetic Superstrates

This letter presents a novel engineered magnetic superstrate designed to enhance the gain and efficiency of a microstrip patch antenna without any substantial increase in the profile of the whole structure (the antenna with the superstrate). The modified split ring resonator (MSRR) inclusions are used in the design of the engineered magnetic superstrate. Numerical full-wave simulations as well as analytical models are used to analyze the entire radiating system. Considering as an example a microstrip antenna operating within the UMTS band, the broadside gain of the antenna was improved by 3.4 dB and the efficiency was improved by 17% when using the engineered superstrate. The total height of the proposed structure, antenna with superstrate, is lambda0/7, where lambda0 is the free-space wavelength at the resonance frequency of the antenna.

Analytical Model for Calculating the Radiation Field of Microstrip Antennas With Artificial Magnetic Superstrates: Theory and Experiment

A fast analytical solution for the radiation field of a microstrip antenna loaded with a generalized superstrate is proposed using the cavity model of microstrip antennas in conjunction with the reciprocity theorem and the transmission line analogy. The proposed analytical formulation for the antennas far-field is much faster when compared to full-wave numerical methods. It only needs 2% of the time acquired by full-wave analysis. Therefore the proposed method can be used for design and optimization purposes. The method is verified using both numerical and experimental results. This verification is done for both conventional dielectric superstrates, and also for artificial superstrates. The analytical formulation introduced here can be extended for the case of a patch antenna embedded in a multilayered artificial dielectric structure. Arguably, the proposed analytical technique is applied for the first time for the case of a practical microstrip patch antenna working in the Universal Mobile Telecommunications System (UMTS) band and covered with a superstrate made of an artificial periodic metamaterial with dispersive permeability and permittivity.

BROADBAND EXPERIMENTAL CHARACTERIZATION OF ARTIFICIAL MAGNETIC MATERIALS BASED ON A MICROSTRIP LINE METHOD

A broadband method is introduced to measure the effective constitutive parameters of artificial magnetic materials. The method is based on the microstrip line topology, thus making it easy to retrieve the constitutive parameters over a wide band of frequencies. To demonstrate the effectiveness of this method, artificial magnetic materials with Fractal Hilbert inclusions are fabricated and characterized. Good agreement between the experimental and numerical simulation results verifies the accuracy of the proposed method.

EBG superstrate for gain and bandwidth enhancement of microstrip array antennas

Two different designs have been studied for the application of EBG as a superstrate for 2 X 2 microstrip array antenna. It was shown that the cross-stacked EBG superstrate improves the input impedance bandwidth and reduces the overall size of the antenna in comparison to previous designs.

Metamaterial for gain enhancement of printed antennas: Theory, measurements and optimization

Metamaterials have been shown to enhance specific performance parameters of low profile and high-profile antennas. Our focus in this paper on specifically increasing the gain of low-profile antennas and in particular the microstrip patch antenna. By placing a metamaterial slab above a microstrip patch antenna (as a superstrate), we show that the gain of the antenna can be enhanced appreciably. The key advantage of using the superstrate is to maintain the low-profile advantage of microstrip patch antennas. In previous works, different types of superstrates were proposed to enhance the gain of microstrip antennas, however, to the best of our knowledge, no theory was developed to understand the mechanism behind the enhancement in the gain. In this paper, we present a simple analytical formulation that provides a very accurate prediction of the gain when a superstrate is used. In fact, our analytical technique is capable of predicting the gain when a multilayer superstrate structures is used. To validate the theory of gain enhancement, antennas and superstrates using metamaterials were fabricated and tested in an echoic chamber. The metamaterials developed were based on split-ring resonators. Strong agreement was found between the measurements and full-wave simulation using commercial tools. Finally, we present optimization results to demonstrate the maximum gain enhancement potential that can be achieved when superstrates are used.

High-Gain Patch Antennas Loaded With High Characteristic Impedance Superstrates

It is shown that, under some resonance conditions, a microstrip patch antenna can be designed to achieve the highest possible gain when covered with a superstrate at the proper distance in free space. The transmission line analogy and the cavity model are used to deduce the resonance conditions required to achieve the highest gain. The resonance conditions include the condition on spacing between the antennas substrate and the superstrate and the thickness of the superstrate. The permeability and permittivity of the superstrate are determined based on these resonant lengths and the appropriate characteristic impedance of each layer in this multilayered structure. The results are verified using both analytical and numerical methods. The effect of anisotropy of the superstrate is numerically investigated. The design criteria proposed here will reduce the total profile of the radiating system by 50% when compared to previous trends.

Enhanced Gain Planar Inverted-F Antenna with Metamaterial Superstrate for UMTS Applications

Planar inverted-F antennas (PIFA) are widely used in wireless hand-held devices due to their small-size, moderate bandwidth and radiation patterns. However, the radiation patterns of such antennas degrade when placed very close to a conductive flnite ground plane. In this paper, an engineered magnetic superstrate is introduced to enhance the gain of PIFA antennas. The engineered magnetic superstrate is based on the broad-side coupled split ring resonator (SRR) inclusions which have high real permeability value at the resonance frequency of the antenna. Numerical full-wave simulations are performed to analyze the entire radiating system (antenna with superstrate). By using the magnetic superstrate, a 3.2dB improvement in the gain of the PIFA antenna working in the UMTS band was achieved. The total height of the proposed superstrate over the antenna is only ‚0=14 where ‚0 is the free-space wavelength at antennas resonance frequency. Thus, the antenna structure remains low proflle, and is advantageous in cell-phone applications.

Theoretical and experimental demonstration of beam steering of patch antenna with superstrate

This paper provides a novel method to steer the main beam of a patch antenna by partially covering it with a high-refractive index superstrate. The beam steering of a single patch is possible because of the dual-slot radiation mechanism of the microstrip antenna. Full-wave simulations have been employed to show beam deflections up to 37° in the presence of high-refractive index superstrates. Experimentally, a beam deflection of 25° is achieved when a microstrip patch is partially covered with a superstrate having a dielectric constant of 10.

Main beam deflection and gain enhancement in superstrate-based antenna systems

The beam of an antenna can be controlled by placing high refractive index superstrates. In this paper, a plane-wave model of a microstrip antenna covered with a high refractive index is introduced. The antenna-superstrate system is analyzed by calculating its transmission response. When the patch is fully covered with the superstrate, the transmission response is truncated along the end-fire angles resulting in gain enhancement. On the other hand, when the superstrate partially covers the patch, a phase imbalance between the electromagnetic radiations emitted from the two radiating slots is produced. This imbalance causes the main beam to deflect from the broadside direction. Full-wave and plane-wave simulations show beam deflections close to 40 degrees. Tunable superstrates can thus be applied to steer the beam of a patch. Hence a novel method is introduced which has been traditionally done using multiple antenna elements with phase shifters.

Artificial Magneto-superstrates for Gain and Efficiency Improvement of Microstrip Antenna Arrays

This paper presents an engineered magneto-dielectric superstrates designed to en- hance the gain and e-ciency of a microstrip antenna array without any substantial increase in the antenna proflle. The broadside coupled split ring resonator (SRR) inclusions are used in the design of the superstrate. Numerical full-wave simulations of a 4 £ 1 linear microstrip antenna array working at the resonance frequency of 2.18GHz and covered by the superstrate show a gain enhancement of about 3.5dB and an e-ciency improvement of 10%. The total height of the proposed structure, is ‚0=7 where ‚0 is the free-space operating wavelength.