In this study, almost monochromatic tuning of absorption strength, i.e. tuning the absorption peak level at almost same frequency, is presented by using angle dependent closed ring resonator (AD-CRR) type narrow band absorber structure in S-band. On this aim, firstly an ordinary planar closed ring resonator (CRR) structure having ground plane is designed and then the structure is folded by a rotation angle α from α = 0° (i.e. planar CRR) to α = 90° (i.e. completely folded CRR) along the center line which is parallel to the incident electric field. Both simulation and experimental results agree that the rotation angle α provides the freedom of tuning the absorption strength of the absorber structure almost monochromatically.

Split-ring resonator is a popular research topic in literature. As known, it may be used in the design of electromagnetic metamaterials. Additionally, these structures can be preferred in microwave filter devices. In this study, a band-stop filter was designed for GSM-900 and 2.4 GHz ISM band by using split-ring resonators. Two split-ring arrays (sizes of one of these arrays were larger than the other) were loaded on the transmission line and each array consisted of four identical rings. Thus, a dual-band pass filter was obtained and this filter covered the frequency of 0.91 (GSM) and 2.43 (ISM) GHz. Then, this proposed design was fabricated and measured. According to the measurement results, the fabricated structure operated at 0.93 GHz and 2.47. The experimental results were consistent with the simulation results. As a result, thanks to the proposed structure, two frequencies can be stopped at the same time. There is no need to design a different filter structure for each frequency.

In this study the effects of using defected ground structures (DGS) composed of a complementary split ring resonator (CSRR) and CSRR with dumbbell (CSRR-D) for rectangular microstrip antennas are investigated. On this aim, two different antennas, which are Antenna B having CSRR etched DGS and Antenna C having CSRR-D etched DGS are designed and fabricated in comparison with the ordinary rectangular patch antenna, which is Antenna A. In both Antennas B and C, CSRR structures are etched in the same position of the ground planes. On the other hand, another ordinary microstrip antenna, called Antenna D, is designed at resonance frequency of Antenna C. For the characterization; resonance frequencies, voltage standing wave ratios, percentage bandwidths, gains, ka values and gain radiation patterns are investigated both in simulations and experiments. The numerical analyses show that 29.39% and 44.49% electrical size reduction (ESR) ratios are obtained for Antenna B and Antenna C, respectively in comparison to Antenna A. The experimental results verify the ESR ratios with 29.15% and 44.94%. Supporting, Antenna C promises 68.12% physical size reduction (PSR) as it is compared with Antenna D. These results reveal that Antenna C is a good alternative for DGS based microstrip electrically small antennas.

This study presents a compact absorber design with an X-shaped resonator (XSR) in the S-band region. The proposed design offers single or dual-band absorption peaks, depending on whether the arm lengths of the resonator are symmetrical or asymmetrical. Prototype fabrications of the absorber, whose numerical design was carried out using CST Microwave Studio, were also measured for verification. Based on the simulated and measured results, the proposed absorber exhibited over 93% absorption spectra with relatively narrow bandwidth characteristics desired, especially for sensor applications. It also provided cross-polarized reflections of less than 0.08 at the frequencies of interest. In addition, the absorption frequency changes depending on the dielectric constant and thickness variations of the sensing layer placed on the absorber were obtained numerically and experimentally to investigate the sensing performance of a dual-band configuration of the absorber. In addition, the same analyzes and measurements were carried out again for two separate single-band split-ring resonator (SRR)-based absorbers designed in this study, and their sensing performances were compared with the dual-band X-shaped absorber's performance. As a result, it was found that the proposed X-shape absorber was more sensitive than the SRR-based absorber, considering the comparison results.