Three-dimensional printed horn antennas with dielectric lens for free-space constitutive parameters measurement

Over the last two decades, there has been significant development in mm-wave and terahertz (THz) technologies, driven by their appealing properties in various applications, including automotive paint materials, metamaterial structures, radio astronomy, military, and medical field. Additionally, the use of dielectric properties for material identification has proven valuable in mm-wave imaging systems. As a result of the increased demand for mm-wave components and systems, there is a greater need for cost-effective measurement solutions in this frequency range and beyond. The free-space measurement technique is widely used methods for determining the electrical characteristics of materials. This doctoral research aims to focus on the development of a free space material measurement system capable of accurately determining materials' permeability and permittivity. A software program through modified NRW algorithm which could determine the materials’ permeability and permittivity with high accuracy was developed rather than expensive commercial software. Also, the permeability and permittivity of MUTs were determined with high accuracy through the software with and without lens for the commercial horn antenna and 3-D printed horn antennas. High gain K-band and Ka-band horn antennas from 18 GHz to 39 GHz using 3D printing technology were designed in order to overcome the need for costly commercial measurement systems. To mitigate the measurement inaccuracies, 3-D printed dielectric lens was designed and fabricated through 3-D printing technology in which beam focus of antenna optimized. 3-D printed horn antennas showed a good agreement with the commercial horn antenna in terms of S11, VSWR, gain and 3- dB beamwidth. As for the gain, with the use of lens the gain increased with a maximum gain of 25.7 dBi at 26 GHz when compared to the gain without the use of lens with a maximum gain of 15.6 dBi at 26 GHz for the K-band horn antenna. Also, for the gain, with the use of lens the gain increased with a maximum gain of 26.5 dBi at 32 GHz when compared to the gain without the use of lens with a maximum gain of 15.5 dBi at 32 GHz for the Ka-band horn antenna. Without the use of lens, 3- dB beamwidth is in the range of 33º to 41.5º while with the use of lens, the 3- dB beamwidth is in the range of 8.9º to 9.7º for the K-band horn antenna. Use of lens allows narrowed beamwidth which focus signals in particular direction throughout the K-band frequency range. As for the Ka-band horn antenna without the use of lens, 3- dB beamwidth is in the range of 28º to 50º while with the use of lens, the 3- dB beamwidth is in the range of 7º to 9º. As for the E-field distribution for the dielectric lens, it increased as the frequency increased which is from 549 V/m at 18 GHz to 855 V/m at 26 GHz for the K-band horn antenna. As for the Ka-band horn antenna, the E-field distribution for the dielectric lens increased from 855 V/m at 26 GHz to 941 V/m at 39 GHz.