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2 October 2008 Modelling THz antennas for cooled superconducting and uncooled semiconducting bolometric pixels
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There is a strong need for wideband and sensitive THz receivers for radio astronomy and remote sensing applications, for which superconducting Hot Electron Bolometer (HEB) mixers are very competitive. Besides, many new THz applications have arisen because of interesting interaction with various media. For practical and economical issues, room temperature detectors are highly attractive for these latter. We have used YBaCuO oxides to fabricate bolometric pixels, either of high-Tc superconducting HEB type (high oxygen content) or semiconducting type (low oxygen content). In the THz range, such materials without any antenna would be totally reflective to the electromagnetic radiation. Moreover, integrated planar antenna structures are recommended for optimal coupling to the small detection area. The aim of this work was to investigate broadband THz antennas coupled to YBaCuO pixels, and address the specific problems arising for each family. For HEBs, self-complementary log-periodic wideband antennas, exhibiting quasi-constant impedance, were chosen. After designing / simulating the THz antenna, we scaled it down to the microwave region for experimental validation purposes. A key issue arose because a thick (10 cm) and MgO electrically equivalent substrate (epsr = 10) was needed to fabricate the large-scale model. For room temperature semiconducting pixels, the main objective was to maintain a large bandwidth despite the difficult matching of the antenna impedance to the large bolometer resistance, namely in the kΩ range. Starting from a high-impedance single dipole-like structure, multi-dipole solutions were investigated to increase the bandwidth. Radiation pattern and polarization issues have also been considered.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ibrahim Turer, Alexander Scheuring, Xabier Gaztelu, Nicolas Ribière-Tharaud, Annick F. Dégardin, and Alain J. Kreisler "Modelling THz antennas for cooled superconducting and uncooled semiconducting bolometric pixels", Proc. SPIE 7117, Millimetre Wave and Terahertz Sensors and Technology, 71170Q (2 October 2008);

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