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Chiral metamaterials comprise a promising platform for advanced optoelectronic and biomedical applications. However, conventional fabrication via lithography is limited by its complexity and high cost. Herein, the lithography‐free fabrication of terahertz chiral metamaterials and their enhancement for sensing the chirality of biocrystal enantiomers is presented. Chiral Au microstrip patterns (CHAMs) in a saw‐tooth shape are fabricated by combining two‐step buckling processes and glancing‐angle deposition. Non‐superimposable geometric chirality is achieved by controlling the tilt angle between the asymmetric and biaxial strain axes and the selective area deposition of the Au layers by using the shadow effect. The manufactured chiral metamaterials show mirror‐shaped terahertz circular dichroism (TCD) signals in the range of 0.2–2.5 THz. Coupling of the induced electric and magnetic dipoles to the chiral‐shaped Au surfaces results in effective optical chirality enhancement. Finite‐difference time‐domain computational simulations reveal the homogeneous distribution of optical chirality with an absolute maximum of 2.24 in the near field. Summing the TCD signals for enantiomeric cystine biocrystals onto the chiral metamaterials shows an ≈7‐fold amplification in magnitude. This enhancement can be attributed to the synergistic effects of superchiral field enhancement and the electromagnetic resonance between the CHAMs and biocrystals. [ABSTRACT FROM AUTHOR]

This article proposes the design of a four‐element array antenna for the accurate direction of arrival (DOA) estimation of Global Positioning System (GPS) interference signals. The proposed array antenna has four individual antenna elements, and each element consists of a radiating patch on the upper layer and a feeding loop on the lower layer. The patch and loop are intentionally designed in a circular shape to obtain the symmetric current distributions on the radiators. The feeding loop is directly connected by two output ports of an external hybrid chip coupler, and the radiating patch is then electromagnetically coupled by near‐fields of the feeding loop. This feeding mechanism in the proposed structure allows for a more uniform current and H‐field distribution for phase characteristics of the radiation that are close to the ideal isotropic radiators in the azimuth angle. In addition, the high‐dielectric ceramic substrate is adopted to minimize the physical height of the antenna for the phase characteristics of the radiation close to the ideal isotropic radiators in elevation angles. To validate that the phase characteristics are similar to those of an ideal radiator, the DOA estimation performances are observed using a dual‐axis interferometry. The results demonstrate that the proposed four‐element array antenna with phase difference characteristics similar to those of an ideal radiator is suitable for the accurate DOA estimation of GPS interference signals. [ABSTRACT FROM AUTHOR]

Since the Gyeongju earthquakes in 2016, there have been increased research interests in the areas of seismic design, building collapse, and rescue radar applications in Korea. Ground penetrating radar (GPR) is a nondestructive electromagnetic method that is used for underground surveys. To properly design ground penetrating radar that detects buried victims precisely, it is important to study electromagnetic wave propagation channel characteristics in advance. This work presents an electromagnetic propagation environment analysis of a trapped victim for GPR applications. In this study, we develop a realistic collapse model composed of layered reinforced concrete and a victim positioned horizontally. In addition, the effects of rebars and the distance between the radar antenna and target are investigated. The numerical analysis presents the electromagnetic wave propagation characteristics, including amplitude loss and phase difference, in the 450‐MHz and 1,500‐MHz frequency band, and it shows the electric field distribution in the environment. [ABSTRACT FROM AUTHOR]

A miniaturized spiral antenna with a broadband balun for a partial discharge (PD) localization system is proposed. The proposed antenna has broadband characteristic from 925 MHz to 1.6 GHz and a unidirectional radiation pattern. The overall dimensions of the fabricated antenna are 80 × 80 × 40 mm3, which is the smallest size among antennas for the PD detection system. The measured −10 dB reflection bandwidth starts at 925 MHz, and the measured directivity of the antenna is about 6 dB in the frequency band. [ABSTRACT FROM AUTHOR]

This letter examines the capacitance of coplanar waveguides (CPWs) in multilayer dielectric substrates.An electrostatic boundary-value problem of CPWs in multilayer dielectric substrates is solved based on the Fourier transform, mode matching technique, and superposition considering the conductor thickness. A series representation for the capacitance is presented. The capacitance is calculated in terms of the CPW geometry to illustrate its behaviors. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1886-1889, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26938 [ABSTRACT FROM AUTHOR]