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This study designs a film monopole antenna for WiBro (wireless broadband internet, 2.3-2.4 GHz) and WLAN (wireless local area network, 2.4-2.48 GHz) bands. A variety of design parameters were used to optimize frequency properties, and radiating and grounding elements were placed on the same plane for maximized radiation efficiency. Cloverleaf-shaped radiating elements were used to induce a phase difference of 180 degrees and thus obtain improved bandwidth. This paper presents the possibility of realizing broadband by using parasitic elements. The antenna created in this study achieves a peak gain of up to 3.18 dBi and satisfies WiBro (2.3-2.4 GHz) and WLAN (2.4-2.48 GHz) bands with a bandwidth of 2.30-2.54 GHz (9.8%) at −10 dB or lower.

To reduce the electromagnetic wave interference caused by cavity resonance or electromagnetic wave leakage, herein, an optical transparent radar absorbing structure (RAS) was designed using transparent conductive oxides (TCOs) with a high optical transmittance and electrical conductivity, and a procedure was proposed for detecting possible defects in the fabrication and operation and for assessing the influence of the defects on the electromagnetic performance. To detect locally occurring defects in planar and three-dimensional absorbing structures, a measurement system based on an open-ended near-field antenna capable of producing small beam spots at a close distance was constructed. Moreover, the reflection characteristics of the transparent RAS were derived from a simplified multiple reflection equation, and the derived results were compared with the analysis results of an equivalent circuit model to predict the surface resistance of the TCO coating layer, based on which the presence of defects could be confirmed. By using the experimental results, the predicted surface resistance results of the coating layer and the results measured using a non-contact sheet resistance meter were compared and were found to correspond, thereby confirming the effectiveness of the proposed defect detection method.

This paper proposes a reconfigurable unit cell for a transmitarray operating at the X band. The unit cell consists of an active patch, a passive patch, and a phase shifter. The active patch has two PIN diodes that change the phase of 180° of the transmitted waves. The passive and active patches both have circular slots to enhance the bandwidth of the transmitted wave. We also propose a new type of experimental characterization technique to measure the performance of the unit cells at the X band without fabricating the entire transmitarray. Instead of a 1 unit cell as described in the literature, we propose 2 × 2 unit cells to measure the performance of unit cells using the X band waveguide. The waveguide consists of a WR-90 section and a rectangular to square waveguide transition section that can be fit to our proposed structure. A good agreement between simulated and measured results was found.

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