This paper presents a systematic parameter study on mesh pattern for optically transparent flexible antenna with feedline. In implementing a transparent flexible antenna using a metal mesh, transparency and performance of antenna and feedline are opposite factors. To understand how both elements are affected by the design parameters of the mesh, we analyze the performance of the feedlines and antennas according to the design parameters of diamond and square meshes. Moreover, the effect of the difference in the shape of diamond mesh and square mesh on performance is analyzed. The measured results of the fabricated samples offer the feasibility of implementing transparent feedlines and antennas with similar performance to nontransparent feedlines and antennas.

This paper presents a fan-beam lens antenna design for IR-UWB through-wall human detection radar applications operating in the 1-8 GHz. The proposed fan-beam lens antenna integrates a dielectric lens, designed by adjusting the lengths of dielectric slabs and air layers, with a Vivaldi antenna to achieve a fan-beam pattern characterized by a narrow beam width in the E-plane while maintaining a wide beam width in the H-plane. The antenna demonstrates excellent time-domain characteristics with a high fidelity factor exceeding 0.93, low reflection signal ringing, and maintained narrow beam width in the E-plane for far-field pulse radiation patterns. Through experimental validation, the antenna achieved SNR improvement due to concentrated signal propagation, enabling stable human detection at distances beyond 5m through walls. The wide H-plane beam width allows effective detection of subjects in various postures, including lying positions. The proposed antenna design shows promising potential for various applications including disaster site search and rescue, building surveillance, fall detection in care facilities, non-contact vital sign monitoring, and smart home occupancy detection systems.

In this paper, we propose an electrically small antenna consisting of a composite right/left-handed (CRLH) transmission line (TL) and a non-Foster matching circuit. An interdigital capacitor (IDC) and spiral inductor are used to fabricate the very high frequency (VHF) band antenna based on CRLH TL. The size of the proposed antenna is as small as 0.025 × 0.014 × 0.0008 λ at 145.5 MHz using the zeroth-order resonant generated by the CRLH TL. The antenna operation bandwidth is extended by the non-Foster circuit (NFC) consisting of a pair of transistors in a cross-coupled manner. An antenna prototype is fabricated and the input impedance, the received power, and gain of the proposed antenna are measured. The results show that the broadband characteristic is maintained while the form factor is extremely small compared to the wavelength. The average received power enhancement and increased bandwidth of antenna are 17.3 dB and 335.5 MHz (from 249.2–268.2 to 145.5–500 MHz), respectively. The calculated gain of the proposed antenna with the non-Foster is about −45 dBi at 155 MHz. The proposed antenna can be considered as a potential candidate of a low-profile antenna for military ground communications at the VHF band.

In this paper, we present the design and fabrication of a dual-band flexible antenna for energy Internet of Things (IoT) applications operating at 380 MHz and 940 MHz. The antenna features a coplanar waveguide (CPW) feed structure and a T-shaped monopole design on a polyimide substrate, with tapered stepped ground plane and square ring-shaped parasitic elements to minimize performance degradation due to bending. The antenna size is 210 × 236 × 0.2 mm³, achieving bandwidths of 25.2% (344~440 MHz) and 15.2% (863~1006 MHz) when flat, with peak gains of 2.52 dBi and 4.90 dBi, respectively. We evaluate the antenna’s performance under various bending conditions using cylindrical styrofoam structures with radii of 25, 35, 45 cm, and the bandwidth degradation is within 4%. To verify the realistic applicability in energy IoT applications, we perform performance analysis considering a transmission tower environment with a cylindrical metal structure having a diameter of 60 cm, ensuring that performance degradation is minimized at a distance of at least 5 cm from the metal structure. Link margin calculations for Korea Electric Power Corporation (KEPCO)'s IoT specifications demonstrate values of 34.08 dB at 380 MHz and 31.94 dB at 940 MHz, confirming the antenna's suitability for KEPCO's energy IoT applications. These results indicate that the proposed antenna meets the requirements for efficient operation in KEPCO's IoT infrastructure.

We propose a hybrid modeling technique for human signal detection through the walls using the distributed radar. The high resolution and excellent penetration performance of the impulse radio ultra-wideband (IR-UWB) radar systems can be used in important applications such as survivor detection in disaster scenarios. The radar channel transfer function between the transmitting and receiving radars obtained from the EM simulator is used for signal processing on MATLAB, followed by coherent synthesis. We perform a hybrid simulation of human detection through the walls using a single radar and verify it through experiments. In addition, we model vital signs behind the walls in various scenarios using the distributed radar and present the coherent synthesis results. The proposed hybrid modeling technique allows us to analyze various distributed radar scenarios in advance. This can reduce the time-consuming and resource-intensive real experiments. It is expected to contribute to radar system design optimization, signal processing algorithm development, and the identification of potential errors before practical implementation. The proposed method is expected to play an important role in various applications of IR-UWB radar technology, including disaster relief operations, non-contact bio signal monitoring, and security and surveillance systems.

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)