A 42 element microstrip parasitic patch antenna is developed in the millimeter-wave band for 5th Generation (5G) mobile communication base stations. A metalized elliptical stripline to embedded microstrip transition with adaptive via hole arrangement as well as a 20dB Chebyshev tapered 6 way power divider is proposed to have an insertion loss of 0.045 dB. To confirm the feasibility of the antenna, the antenna has been measured to provide a 6.2 % impedance bandwidth from 26.83 GHz to 28.56 GHz at VSWR of less than 1.96 dB. The array antenna gains of more than 21.4 dBi has been realized with side lobe levels (SLLs) of less than -19.4 dB operating within 27.5 GHz to 28.5 GHz in both the azimuth and elevation directions.

A dual-polarized Vivaldi antenna pair has been designed for use in a vehicle-to-anything (V2X) measurement facility. The operating bandwidth is from 560 MHz to 7.7 GHz (173% fractional bandwidth), covering all the existing V2X communication frequencies. The ultrawideband (UWB) property was achieved by integrating quarter-wave baluns at the feeding point of two orthogonally crossed Vivaldi antennas. The measured port isolation between the two antennas is better than -28 dB. The cross-polarization discrimination of better than 17.2 dB and antenna gain of up to 9.2 dB have also been realized across the whole bandwidth. Three of the designed antennas were mounted on a vehicle testing facility and were used to measure the radiation patterns of a roof-top shark antenna under four different V2X scenarios. That is, vehicle-to-pedestrian, vehicle-to-vehicle, and vehicle-to-infrastructure and vehicle-to-network. The results have also been presented in this communication.

In this paper, a dual-band conductive textile-based wearable antenna operating at LoRa-868 MHz and BLE-2.4 GHz is presented. The proposed antenna is intended for accurate geolocation, tracking and communication applications in the military, industrial and telemedicine industries. The low-profile patch antenna is suitable for integrating into clothing. It is composed of three textile layers: top and bottom silver-ink-printed polystyrene fabrics, and a neoprene substrate. To utilize the flexible and restorable properties of these textile materials, the proposed antenna is directly fed by a flexible cable using an aperture-coupled feeding technique. This method not only eliminates the use of the conventional, bulky, and metallic SMA connector but also introduces a secondary resonance at 2.4 GHz, enabling the dual-band property. Using a thin coaxial cable fixed on the aperture slot for proximity coupling, a compact antenna size of 150 mm² is obtained that can easily be attached and detached on existing cloths. The proposed structure has been fabricated and measured in an anechoic chamber to verify the performance. Measured gain of 3.28 dBi and 3.25 dBi was realized for LoRa and BLE at an antenna size of 0.61 λ_g × 0.61 λ_g × 0.012 λ_g (where λ_g is guided wavelength at 868 MHz) with a front-to-back ratio (FBR) of greater than 10 dBi.

Screen-printed and inkjet-printed conductive fabric antennas have been investigated in this manuscript. The former showed optimal radiation performance after fabrication and measurement, which was the basis for developing a new fabric antenna feeding technique. The aperture-fed technique is achieved with a single coaxial cable overlayed on a cut-out slot on the ground layer of the patch antenna. The cable is connected with conductive silver-based epoxy paste with high resilience to mechanical stress. Two antenna models for Bluetooth low energy (BLE) and long-range (LoRa) wireless applications were designed, fabricated, and measured at 2.44 GHz and 868 MHz, respectively, with good impedance and radiation performance. The measured antennas operated from 2.4 to 2.48 GHz (BLE) and 853 to 886 MHz (LoRa) at −10 dB S11. Measured results also showed a 56% radiation efficiency at BLE and 44.9% at LoRa. The screen-printing procedure and feeding technique have been presented in this manuscript.

An ultra-wideband antenna with a conical ground and trident inset feeding structure is presented. The antenna consists of a U-shaped monopole designed on a printed circuit board and a three-dimensional conical aluminium mold, serving as the ground. Low frequency ( $ < {1}$ GHz) matching is achieved with the trident feed branches by inserting them into the monopole. Simulation studies show that the proposed 3-D conical ground outperforms horizontal or flat-lying ground models in terms of impedance matching bandwidth and radiation pattern omni-directivity. The 3-D ground also helps to stably mount the antenna in a measurement facility. Simulation and measured results presented in this paper demonstrate that the proposed antenna is suitable as a testing antenna with omnidirectional radiation patterns over a broad bandwidth. A 14.6:1 bandwidth ratio (0.56 - 8.2 GHz) has been realized at a voltage standing wave ratio below 2:1 with antenna gain above 2 dBi.

A choke ring horn antenna has been designed for use as an RF applicator in a compact range in vitro 28 GHz bioelectromagnetic exposure system. The 30 mm × 50 mm horn antenna was fabricated and measured to operate from 27.75 GHz to 34.5 GHz with a −20 dB measured S11 and a measured antenna gain of more than 10 dBi. A wide sectoral (flat top) and symmetric E- and H-plane pattern with a half-power beamwidth of more than 60 degrees was achieved with a cross-polarization discrimination of better than 28 dB. Electromagnetic slots were introduced in the antenna to suppress excess cavity mode radiation which inherently impacts the cross-polarization levels of choke ring antennas. The proposed antenna was successfully integrated into the compact measurement chamber in partnership with the Korea Telecommunication Research Institute (ETRI) and is currently in use for real-time 5G millimeter-wave dosimetry studies.