In this research, Airborne broadband (maximum 400 MHz bandwidth) C band circularly polarized synthetic aperture radar (SAR) is proposed and developed for further study on airborne compact polarized synthetic aperture radar (CP SAR) system using circular polarization. This paper explains the scattering characteristic of circular polarization as the concept of Circularly Polarized SAR, system configuration, RF system and antenna, ground test, and flight test of Circularly Polarized SAR in Hinotori-C2 (Firebird-C2) mission onboard CN235MPA aircraft on 14-15 March 2018 at South Celebes, Indonesia. The result of the flight test depicts multipath full polarimetric circularly polarized images that show good performance of Circularly Polarized SAR and matched well to the result of the ground test of a multi polarized single pulse. The Circularly Polarized scattering clarification using trihedral, cylindrical, and Omni corner reflectors (TCR, CCR, and OCR), assessment of Circularly Polarized image analysis, and image classification using the conventional axial ratio (AR), ellipticity (ε), and polarization ratio (ρ) is discussed. The proposed Circularly Polarized SAR will enrich the existing CP SAR systems and could be employed in further study of CP SAR calibration technique, also applications development for the environment and disaster monitoring using CP SAR.

The need for antennas with small dimensions with high performance has prompted various research to conduct experiments in terms of the structure and shape of the antenna and terms of material. This study proposes utilizing both artificially and engineered magneto-dielectric (MD) materials’ characteristics to miniaturize antenna dimension and improve antenna performance. The MD characteristics are realized through the SRR array structure as an antenna performance enhancer; and material synthesis as an antenna dimension reducer. MD material has been successfully synthesized, extracted, and characterized from a mixture of magnetite powder (Fe ₃ O ₄ ), PDMS elastic polymer material (polydimethylsiloxane), and BaFe ₁₂ O ₁₉ . The parametric study results show that the antenna designed on MD material Sample C (PDMS: Fe ₃ O ₄ =1: 0.6) with a 3 $\times $ 3 SRR configuration gives the most optimal response. Simulations, optimizations, and measurements have been carried out to obtain an MD antenna that works at a frequency of 3.5 GHz, with a fractional bandwidth of 10% (360 MHz), radiation efficiency of 58.54%, and a maximum gain of up to 4.33 dBi. This antenna measures 30 $\times30$ mm or 64% smaller than conventional antennas. The proposed stacked MD antenna is compatible with 5G technology in the mid-band frequency range.

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.

The field of terahertz (THz) science and technology research area have been exponentially growing recently, motivated by the increasing demand for safer security imaging, better quality control within manufacturing industries, space and astronomical investigation, biomedical diagnostics, and larger communication bandwidth. The THz waves detection mechanism is one of the critical components in developing a high efficiency and high sensitivity THz communication system. This paper reviews the principle and instrumentation of THz optical metrology for the precise and accurate characterization of THz detectors in the range of 0.1 THz to several THz. In this context, we individually discuss the determination of radiation input power and effective area followed by a survey of THz optical measurement methodology used in the state-of-the-art THz detectors. In addition, challenging issues remaining in the THz detector measurements are provided. This paper sets out a guideline to address the main concept behind the THz detector measurement as well as their challenges and opportunities. Additionally, useful insight is given through a summary of available power meter instrumentation for THz input power calibration.

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.