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.

Metamaterials are typically made of an ensemble of electrically small resonators such as metallic loops. The fact that such particles resonate individually to generate a bulk material behavior having enhanced constitutive parameters is essentially indicative of these particles' ability to collect energy. We show that such particles act as energy collectors when a resistive load is inserted within the particle's gap. A proof of concept is provided using a 5.8 GHz field and a split-ring resonator (SRR) as the electromagnetic energy collecting cell. Numerical simulation for a 9 × 9 SRR array shows the effectiveness of an SRR array as an energy collector plate.

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.

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.

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.

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.