Muhammed S. Boybay

Electromagnetic Coupling Reduction in High-Profile Monopole Antennas Using Single-Negative Magnetic Metamaterials for MIMO Applications

Single-negative magnetic metamaterials are used in order to reduce mutual coupling between high-profile antennas used in multiple-input multiple-output systems. The magnetic permeability of the developed single-negative inclusions have negative effective response over a specific frequency band. The inclusions considered here are composed of broadside coupled split-ring resonators. The single-negative magnetic inclusions are inserted between closely-spaced high-profile monopole antenna elements. It is shown that mutual coupling between the antenna elements can be reduced significantly by incorporating such magnetic inclusions. Effective response of the constitutive parameters of the developed magnetic inclusions are incorporated within the numerical models. Good agreement is obtained between the experimental and numerical results.

Material Characterization Using Complementary Split-Ring Resonators

A microwave method based on complementary split-ring resonators (CSRRs) is proposed for dielectric characterization of planar materials. The technique presents advantages such as high measurement sensitivity and eliminates the extensive sample preparation procedure needed in resonance-based methods. A sensor in the shape of CSRRs working at a 0.8-1.3 GHz band is demonstrated. The sensor is etched in the ground plane of a microstrip line to effectively create a stopband filter. The frequencies at which minimum transmission and minimum reflection are observed depend on the permittivity of the sample under test. The minimum transmission frequency shifts from 1.3 to 0.8 GHz as the sample permittivity changes from 1 to 10. The structure is fabricated using printed circuit board technology. Numerical findings are experimentally verified.

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.

Complementary Split-Ring Resonator for Crack Detection in Metallic Surfaces

A new sensor based on complementary split-ring resonators is presented to detect sub-millimeter surface cracks. The sensing mechanism is based on perturbing the electromagnetic field around an electrically small resonator, thus initiating a shift in the resonance frequency. The sensor is simple to fabricate and inexpensive as it is etched out in the ground plane of a microstrip-line using printed circuit board technology. The sensor exhibits a frequency shift of more than 240 MHz for a 100 μm crack.

Mutual coupling reduction in MIMO antennas using artificial magnetic materials

In this paper, artificial magnetic resonators are used in order to reduce mutual coupling in Multiple-input Multiple-Output (MIMO) systems. Split-ring resonator (SRR) inclusions are inserted between closely-spaced high-profile monopole antenna elements. It is shown that mutual coupling between the antenna elements can be reduced significantly by incorporating such magnetic inclusions. The magnetic materials work as insulators, and thus can be applied in a variety of antenna applications.

Non-Destructive Thickness Measurement Using Quasi-Static Resonators

A microwave sensor for non-destructive measurement of dielectric thickness is presented. The sensor is a quasi-static resonator and based on complementary split ring resonator (CSRR) structure. When the CSRR structure is backed by a conductive medium covered with a dielectric layer the resonance frequency of the CSRR has a strong dependence on the thickness of the dielectric layer. Effect of the size of CSRR sensor on the sensitivity is analyzed numerically. For experimental verification, a CSRR sensor that operates in the 1.6 to 2.3 GHz band is fabricated and excited by a microstrip line.

Near-Field Probes for Subsurface Detection Using Split-Ring Resonators

Most of the previous microwave near-field probes and imaging techniques focused on surface imaging, providing ultrahigh lateral resolution. Few microwave near-field probes were developed for subsurface detection, offering both high lateral and depth resolution with varying degrees of effectiveness. In this work, a novel microwave near-field probe using a single split-ring resonator is introduced with the primary focus of subsurface detection. The design is simple, compact, inexpensive, and easy to fabricate using printed circuit board technology. Fourier spatial analysis of the field of the new probe reveals a substantial enhancement of the evanescent field, thus making a significant difference in subsurface detection. Experimental results illustrate that a small 3.24-mm aluminum block immersed in 1% sodium chloride (NaCl) solution and positioned 4 mm away from the surface was successfully detected using a probe operating at 1.218 GHz. For this particular experiment, where the size of the object was λ/74 , the detection ability of the new probe was tested using 2% and 3% NaCl solution as well. The phase changes due to the depth of the object demonstrate that the new probe is able to sense the presence of the same object in very lossy medium (3% NaCl whose loss tangent is approximately unity) with depth of 1-2 mm in spite of a standoff distance of 1-mm air and a container thickness of 6.35 mm.

Open-Ended Coaxial Line Probes With Negative Permittivity Materials

This work presents analysis of the behavior of open-ended coaxial near-field probes in the presence of ε-negative material. The effect of using negative material layers on the sensitivity is studied. It is shown that optimal conditions related to the thickness and constitutive parameters of the negative medium give rise to significant enhancement in probe sensitivity which allows the probe to have higher material and detection resolutions. The analytical formulation is validated using three-dimensional full-wave simulations of the coaxial probe in the presence of the negative medium.

Waveguide Probe Loaded With Split-Ring Resonators for Crack Detection in Metallic Surfaces

We present a near-field waveguide probe with an embedded array of split-ring resonators (SRRs) that operate at 16.65 GHz. When the probe scans a metal surface, the magnetic flux generated from the currents on the metallic surface strongly affects the equivalent lumped parameters of the SRRs. This, in turn, affects the reflection coefficient of the feeding port leading to high sensitivity in detecting anomalies such as cracks in the surface. Experimental results indicated the feasibility of detecting cracks, as small as 25 μm in width, in metallic surfaces. Additionally, the probe achieves good resolution in detecting closely spaced cracks.

Characterization of Metamaterials Using a Strip Line Fixture

A method is introduced to measure the effective constitutive parameters of metamaterials having negative permittivity, negative permeability, or negative permeability and negative permittivity simultaneously. The method is based on the strip line topology, thus offering low cost and low setup complexity in comparison to other methods. The method proposed here is validated by numerically simulating the measurement setup while using different types of metamaterials. To validate the method experimentally, a metamaterial having negative permeability over a band of frequencies is characterized. Good agreement is obtained between the experimental and numerical results.