Mikal Askarian Amiri

Analysis, Design, and Measurements of Circularly Symmetric High-Impedance Surfaces for Loop Antenna Applications

A new wideband circular high-impedance surface (HIS) is proposed. Two models are developed to analyze the reflection characteristics of the proposed HIS. It is also shown through simulations that a circular HIS as a ground plane for loop antennas is superior to a rectangular HIS ground plane. The circular HIS was fabricated and a loop antenna was placed above it. Measurements were then performed and their results were compared with simulations. An excellent agreement was indicated.

Gain and Bandwidth Enhancement of Ferrite-Loaded CBS Antenna Using Material Shaping and Positioning

Loading a cavity-backed slot (CBS) antenna with ferrite material and applying a biasing static magnetic field can be used to control its resonant frequency. Such a mechanism results in a frequency-reconfigurable antenna. However, placing a lossy ferrite material inside the cavity reduces the gain and impacts the impedance bandwidth. This letter develops guidelines, based on a nonuniform applied magnetic field and nonuniform magnetic field internal to the ferrite specimen, for the design of ferrite-loaded CBS that enhance its gain and tunable bandwidth by shaping the ferrite specimen and judiciously locating it within the cavity. To validate the modeling, simulations were performed using ANSYSs Maxwell 3D and HFSS, and they were compared to measurements conducted in the Arizona State University (ASU) anechoic chamber.

Notable gain enhancement of curvilinear elements using a circular HIS ground plane

Two curvilinear radiating elements (loop and spiral) are placed above a circular HIS ground plane. It is shown through simulations and measurements that in addition to the bandwidth enhancement compared to a rectangular HIS ground plane, the gain increases by an additional 3 dB when a circular HIS is used instead of the conventional HISs due to the radial phase profile.

Reflection phase characterization of a circularly symmetric high impedance surface

The reflection characteristics of a circularly symmetric high impedance surface, with a circular substrate in a cartesian coordinate system, is studied and compared with that of the rectangular HIS with straight strips. The operational bandwidth of the circular and rectangular HISs are obtained and compared together.

Reflection phase characterization of spherical high impedance surfaces with circular periodicity

In this paper the reflection phase of a flat HIS with circular periodicity is characterized. A spherical curvature is then introduced to the designed surface and its impact on the reflection phase is investigated. A mathematical analysis is provided to find the limit of the curvature which can be applied to these type of artificial ground planes.

A spiral element above a spherically curved AMC ground plane

A circular HIS with spherical curvature is designed and used as ground plane for spiral antennas. The operational bandwidth, gain pattern and impact of the curvature on the performance of the antenna is studied.

Design, simulation and antenna applications of spherical high impedance surfaces

Design and simulation of a conformai high impedance surface with spherical curvature is reported. A loop antenna is located in the vicinity of this curved surface to investigate if the spherical HIS can be used as an appropriate ground plane. The return loss and gain pattern of the loop is obtained from simulations and compared with those of a flat circularly symmetric HIS. The -10 dB operational bandwidth of the surface is also obtained.

Applications of circularly symmetric high impedance surfaces for spiral antennas

A circularly symmetric high impedance surface is used as ground plane for spiral antennas. It is shown through simulations that a circular high impedance surface exhibits a wider operational bandwidth when used as ground plane for this type of radiators compared to loop antennas.

Reflection phase characterization of wideband semi-periodic circular high impedance surface

A wideband semi-periodic circular high impedance surface for loop antenna applications is designed. The surface is illuminated with a plane wavw whose electric field is of phi component. A loop antenna is placed above the surface afterwards to find the operational bandwidth of the structure.

Gain and bandwidth enhancement of ferrite-loaded circular cross-section CBS antenna

This paper develops design guidelines, based on a nonuniform applied magnetic field and nonuniform magnetic field internal to the ferrite material, for ferrite-loaded circular cross-section CBS antenna that improves the gain and the tunable bandwidth by judiciously shaping and positioning of the ferrite specimen within the cavity.