Antennas with high gain that can operate in Super Wide Band (SWB) frequencies can be employed for a variety of wireless applications that serve different telecommunications infrastructure and radar applications. However, wide-bandwidth antennas suffer from interference from other wireless technology networks, necessitating the deployment of strategies to block some undesired signal frequencies. A new method for increasing bandwidth by shortening the taper slot length of the Vivaldi antenna and increasing the antenna radiation pattern by using a wavy structure and adding a Square-Complimentary Split Ring Resonator (S-CSRR) structure that can notched-band several frequencies has been investigated on the Coplanar Vivaldi Antenna (CVA). In this study, we investigated seven different types of antennas: Conventional CVA (C-CVA), CVA-Short Slot and Long-Slot (CVA-SS and CVA-LS) with antenna lengths of 10 and 15 cm, wave CVA (WCVA), and WCVA with CSRR. In all frequency bands ranging from 2.3 to more than 30 GHz, the S ₁₁ of the CVA-SS antenna is less than -15 dB with minimum S ₁₁ of-62.21 dB. When compared to the CVA-LS without a corrugated construction, the WCVA-SS antenna has 5.77 dBi improvement of directivity at 15 GHz. By incorporating the S-CSRR structure into WCVA, four notched frequency bands are formed: 3.335 - 3.72 GHz (WiMAX spectrum), 4.72 - 5.354 GHz (WLAN), 6.07 - 6.743 GHz (Wifi 6E usage), and 7.408 - 8.293 GHz (X- satellite bands). S-CSRR also potentially result in circular polarization at 4.6 - 5.3 GHz with the minimum AR of 0.438 (at 5 GHz), at 7.8 -8.2 GHz with the minimum AR of 0.732 (at 8GHz) and at 27 GHz with AR of 2.1 by constructing a U shape with four SCRRs. There was also good agreement between simulation and measurement results. As a result, the WCVA-SS antenna with a Square-CSRR structure may be recommended for the usage of SWB antennas, where a single antenna can serve numerous telecommunications and radar system applications.

Polarization diversity is an antenna feature that has been widely researched to increase the capacity of a wireless communication system. The conceptual theory of polarization states that all polarization vectors can be decomposed into two orthogonal electric field vector modes. This study proposes a novel framework to bridge the gap between circular polarization (CP) technique and filtering antenna design using two orthogonal resonators with the ability to represent any polarization. The proposed method combines the techniques of antenna–filter and CP design into a single integrated step. To achieve the second-order antenna–filter integration and generate CP, the two orthogonal resonators modeled as a rectangular radiator and a $\uplambda $ /4 resonator combined. The CP filtering antenna operates at a frequency of 4.65 GHz, with an impedance bandwidth of 4.7%, an axial ratio (AR) bandwidth of 3.2%, and a gain of 6.2-dBi. To validate the CP filtering antenna, simulations and measurements were performed, and the results were found to be in good agreement.

Super-wideband (SWB) antennas have emerged as a promising technology for next-generation wireless communication systems due to their ability to transmit and receive signals across a wide frequency spectrum. A half-elliptical-shaped patch antenna for a super-wideband antenna is proposed in this paper. The proposed antenna was composed of a half-elliptical-shaped patch with a microstrip feedline and a partial ground plane with a triangular inset and a bent edge ground plane. This proposed antenna was designed using Taconic TLY-5 with a dielectric permittivity of 2.2 and a total dimension of 200 × 220 × 1.57 mm³. The proposed antenna demonstrates a bandwidth of 23 GHz (from 0.5 GHz to 23.5 GHz) with a bandwidth ratio of 47:1.

This study presents a novel design of two filtering antennas with a +45° and -45° slant polarization, using the co-design of a third-order filter and a rectangular patch antenna. Slant polarization is obtained by directing the surface current that flows to the radiator by applying two parallel inverted resonators in the transmission line. The resonators consist of two parallel strips with alternate open and short circuits at each end and the 45° and -45° polarization is determined from these short circuit positions. The rectangular patch antenna is fed using proximity coupling, and it is parallel to the resonators. The filtering antennas provide not only 45° slant polarization, a flat gain response but also a controllable bandwidth. Operating at 4.65 GHz for 5G application, the antennas have a controllable bandwidth range from 5.9% to 8.4% without affecting the polarization and center frequency. The gain responses are filter like and attain the maximum value of 6.82 and 6.69 dBi at 4.7 GHz. This design needs no extra component or rotation of the radiator and transmission line because the inverted resonators can switch the polarization to be +45° and -45°. The results of the 45° and -45° polarization filtering antenna simulation and experiments are consistent with each other.

A substrate-integrated waveguide (SIW) antenna is an implementation of a waveguide antenna in a microstrip antenna. The microstrip antenna, as a low-profile antenna, suffers from narrow impedance bandwidth. This paper proposes a novel bandwidth enhancement method for solving a narrow impedance bandwidth. Bandwidth enhancement was achieved by using quad-resonant frequencies. The quad-resonant frequencies are resulted from the hybrid half-mode substrate-integrated waveguide (HMSIW) cavities between the inner and outer cavities. The inner HMSIW cavity has a half-pentagon ring slot that disturbs the TE $_{\mathrm {101-inner}}$ , TE $_{\mathrm {102-inner}}$ , TE $_{\mathrm {202-inner}}$ , and TE $_{\mathrm {103-inner}}$ modes, whereas the outer HMSIW cavity consists of two outer quarter-mode substrate-integrated waveguide (QMSIW) cavities. The outer HMSIW cavity generated the TE $_{\mathrm {102-outer}}$ and TE $_{\mathrm {202-outer}}$ modes. The hybrid cavities were fed simultaneously using a port with a quarter-wavelength feed transmission line. The hybrid HMSIW cavities generated resonant frequencies that were close to each other. Additionally, this method was applied to the X-band frequency with a low-profile substrate. The simulated impedance bandwidth and peak realized gain was 33.86% ( $8.98-12.64$ GHz) and 7.97 dBi, while the measured impedance bandwidth and peak gain were 31.83% (9.14 – 12.6 GHz) and 7.62 dBi, respectively. Strong agreement was observed between the measurement and simulation results.

Flights are projected to reach eight billion globally by 2037, demanding airport operators manage operations effectively, including safety on the runway due to the high number of aircraft movements. One crucial issue is any foreign object, commonly known as foreign object debris (FOD), that must be detected and cleaned immediately to ensure aircraft safety when taking off, landing, and taxing. The International Civil Aircraft Organization (ICAO) reported that FOD causes 10.08% of aviation accidents. Most airports manually monitor and detect FOD, which could be more effective and dangerous. Therefore, it is important to provide FOD detection systems with proper technologies. Radar technologies are potential FOD detection techniques that offer robustness to weather fluctuation. However, some factors must be considered properly to provide an effective FOD system. This paper reviews radar technologies for FOD detection on airport runways by considering factors, including types of debris, detection coverage, mode of radars, frequencies, and attenuation. It was found that all critical factors considered contribute to the quality of detection. This paper will provide guidelines for developing FOD detection based on radar technologies regarding airport necessities and its specific environment.