Muhammad Kamran Khattak

Thin AMC-backed printed loop antenna for ISM band with improved antenna performance and lower SAR

In this paper, a novel and thin artificial magnetic conductor (AMC) backed loop antenna is presented. The proposed low-profile loop antenna is printed on a thin FR-4 substrate with thickness of approximately 0.008 λg (1 mm) backed by the metallic structure to achieve the characteristics of AMC for improving the antenna performance. The structure resonates at 2.4 GHz. The properties of AMC such as the magnitude and phase of the reflection coefficient are investigated. The designed AMC is then used as back-plane for the printed loop antenna. The improved performance of the antenna by the introduction of AMC is observed. Compared to the PEC-backed design, the proposed AMC-backed design not only enhances the antenna performance but also lowers the specific absorption rate (SAR) of the antenna. The method is validated by the simulation and measurement.

A novel dipole antenna backed by a thin and small-area AMC for good impedance match and low SAR on human tissue

Abstract This paper presents a new dipole antenna that has robust input impedance matching and electromagnetic radiation, and low SAR for human body contact. It is made possible by backing the main radiator with a thin and small-area artificial magnetic conductor (AMC). Different from the conventional AMC which occupies a multi-layered large area based on the full PEC ground for a high antenna directivity, the proposed structure works for 2.4-GHz-ISM band, and has a 1-mm thickness and a 50 mm-by-50 mm footprint with good impedance matching and radiation performances even near human tissue, and a low SAR below 1.6 W/kg is obtained. This design method is validated by full-wave simulations and physical implementation.

A small-sized automobile LTE multi-band MIMO antenna

This paper deals with an effective method to maximize the characteristics of a MIMO antenna system for cars. This stems from the improvement of isolation between the two radiators. A metamaterial kind of decoupling device which is a modified SRR curbs the unwanted interaction between the MIMO elements. New flat dual-band monopoles with the interference-reduction device for the MIMO system are suggested and the numerically experimented results of the cases without and with the proposed structure are compared. These show how good isolation level is obtained. It is certain that the entire structure is adoptable to the placement on the car surface.

A planar 8-way radial power-splitter combined flat ap-antenna with increased h-plane gain

A method to make the access-point(AP) antenna flat and create multiple beams with good gains in the horizontal plane is proposed to overcome the drawbacks of the monopole antenna. The monopole antenna has a relatively high profile and low H-plane gain due to the imbalance in elevation. Considering 8 beams around the circle, the input power is divided by a thin 8-way radial power-splitter which requires technical treatment on very high impedance as large as 400 Ω. This is connected to 8 quasi-Yagi antennas. The experiment shows the desired power-splitting and the improvement of the horizontal-plane gain as a flat antenna structure.

Metamaterial-embedded beamforming phased-array antennas for degradable GPS links

This paper presents an approach to enable a typical GPS receiver to be much less susceptible to intentional disruption such as jamming and change in link environment. Beamforming GPS receivers comprising 4×4 elements or 8×8 ones are designed using metamaterials, for the placement on the body of an aircraft as an airborne vehicle, to cope with the varying angle of incidence with good antenna gain and the low inter-element interference to make the system more robust and adaptive. The design results show the antenna gain much higher than 5 dBi, and the movable circularly polarized beam with the excellent axial ratio at the resonance frequency and low mutual coupling between the elements.

Investigating electromagnetic power transfer ratio of circular polarizing planar metasurface lens

We designed an antenna structure with the circular polarization metamaterial superstrate which increases the directivity of the primary antenna as a lens. The metamaterial superstrate removes the necessity of the array antenna and complicated feed. Plus, it provides the Fabry-perot cavity with the circular polarization. With regard to the primary antenna, a CRLH antenna is adopted to have the size-reduction from the conventional half-wavelength patch antenna.

Electromagnetics computational modelling of magnetic metamaterials for wireless power transfe

We design a compact metamaterial structure enabling the wireless power transfer(WPT) system to enhance its function and model it for electromagnetic characterization. To couple the transmitting and receiving loops of the system compliant with the A4WP requirements, the metamaterial should resonate at a very low frequency as an effectively magnetic device. Additionally, they must be substantially small for the low frequency far below 10 MHz, taking into account the integration to practical handheld devices. The miniaturized structure is simulated through a full-wave method, and its magnetic properties are investigated through the so-called retrieval algorithm to extract its effective permeability. The analysis results present the relationship between the WPT coupling device and metamaterial constitutive parameters.

Nature-Inspired High-Directivity Microstrip Antennas: Fractals and Genetics

High directivity single element patch antennas with broadside directivity are preferred to array antennas since it avoids the need for a complex feeding network. Two examples of high-directive microstrip antennas synthesized by fractals and genetic algorithm optimization are compared in this paper. Both simulated and measured results show the potential of fractals and genetic algorithms to design non-intuitive antennas having broadside and high-directivity performance with a single microstrip element. Said elements are useful for hot-spots.

Low-SAR metasurface-based dipole and its beamforming array

This paper suggests a new planar metamaterial-based dipole with a low SAR. The artificial magnetic conductor(AMC) lies below the dipole through a thin AMC to prevent a high SAR as well as secure a good impedance match, which will become poor near the human tissue by the conventional techniques. The design is conducted for 2.4 GHz WBAN frequency, and shows the strengths at volume miniaturization, return loss and SAR. Also, this method is extended to the beamforming characteristics in an array configuration aiming to build adaptive wearable equipment

Flat Rotman lens for 5G beamforming antenna

In this paper, a planar Rotman lens featured as beamforming and multiple beams is presented, aimed at the potential use for 5G communication. The feeding network and the radiating patches are made as a single layer Taconic-microstrip structure for a 24-GHz area operation for low cost and practicality. The beamforming characteristics are verified by the full-wave simulation which is validated by the fabrication and measurement.