Modeling Broadband Antennas for Hot Electron Bolometers at Terahertz Frequencies

There is a strong need for wideband and sensitive receivers for radio astronomy and remote sensing applications in the terahertz (THz) region. Superconducting hot electron bolometer (HEB) mixers are a competitive alternative to conventional mixer technologies in the THz range. The aim of this chapter is to model antennas coupled to HEBs belonging to an array working in the 1–7 THz range, typically. Several broadband antenna types were investigated before selecting the log-periodic structure. In order to perform experiments in microwave-devoted anechoic chambers, the antenna working frequency band has been scaled down to the 2.25–17.5 GHz range. We have so measured a front-to-side gain ratio of 18 dB at center frequency, which is quite satisfactory for HEB THz imaging arrays. Experimental results performed with scaled models, as compared with simulations performed with a commercially available finite element software, exhibited on the whole good matching within a 2–3 octave bandwidth.