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Dzardanov, A., Ekstrom, H., Gershenzon, E., Gol'tsman, G., Jacobsson, S., Karasik, B., et al. (1994). Hot-electron superconducting mixers for 20-500 GHz operation. In Proc. Int. Conf. on Millimeter and Submillimeter Waves and Appl. (Vol. 2250, pp. 276–278).
Abstract: Bolometdcmucers based on Nb and NbN superconducting thin films in the resistive state have been prepared for 20, 100 GHz and 350-500 GHz operation. The mixing mechanism is presumably of electron heating origin. Our measurements indicate that a conversion loss of about 6-8 dB can rather easily be achieved, and that the noise is reasonably low. The requirements on the operation mode and on the film parameters in order to obtain small conversion losses or even gain are discussed. For NbN films the availability of nearly 1 GHz IF bandwidth is experimentally demonstrated. NbN hot-electron mucers combined with slot-line tapered antenna on Si membrane or with double-dipole antenna on SiO^ substrate have been fabricated. The devices we study are considered to be very promising for use in heterodyne receivers from microwaves to terahertz frequencies.
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Cherednichenko, S., Khosropanah, P., Berg, T., Merkel, H., Kollberg, E., Drakinskiy, V., et al. (2004). Optimization of HEB mixer for the Herschel Space Observatory. In Proc. 15th Int. Symp. Space Terahertz Technol. (16).
Abstract: A mixer development for the HIFI instrument of the Herschel Space Observatory has come to the final stage. In our paper and conference presentation we will describe the most important details of the Band 6 Low and High Mixer Unit design. Special attention will be given to the optimization of the hot- electron bolometer mixer chip, which is based on 3.5nm NbN superconducting film on silicon. As the HEB’s local oscillator power requirements depend on the bolometer size, we have compared mixer noise temperature for different bolometer width- to- length ratio. A trade- off between mixer performance and local oscillator power requirements results in the mixer units equipped with optimized mixer chips, providing the largest coverage of the Band6 RF band with the lowest possible receiver noise. A short account of the beam pattern measurements of Band6 mixers will be given as well.
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Cherednichenko, S., Khosropanah, P., Adam, A., Merkel, H. F., Kollberg, E. L., Loudkov, D., et al. (2003). 1.4- to 1.7-THz NbN hot-electron bolometer mixer for the Herschel space observatory. In T. G. Phillips, & J. Zmuidzinas (Eds.), Proc. SPIE (Vol. 4855, pp. 361–370). SPIE.
Abstract: NbN hot- electron bolometer mixers have reached the level of 10hv/k in terms of the input noise temperature with the noise bandwidth of 4-6 GHz from subMM band up to 2.5 THz. In this paper we discuss the major characteristics of this kind of receiver, i.e. the gain and the noise bandwidth, the noise temperature in a wide RF band, bias regimes and optimisation of RF coupling to the quasioptical mixer. We present the status of the development of the mixer for Band 6 Low for Herschel Telescope.
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Cherednichenko, S., Kroug, M., Merkel, H., Khosropanah, P., Adam, A., Kollberg, E., et al. (2002). 1.6 THz heterodyne receiver for the far infrared space telescope. Phys. C: Supercond., 372-376, 427–431.
Abstract: A low noise heterodyne receiver is being developed for the terahertz range using a phonon-cooled hot-electron bolometric mixer based on 3.5 nm thick superconducting NbN film. In the 1–2 GHz intermediate frequency band the double-sideband receiver noise temperature was 450 K at 0.6 THz, 700 K at 1.6 THz and 1100 K at 2.5 THz. In the 3–8 GHz IF band the lowest receiver noise temperature was 700 K at 0.6 THz, 1500 K at 1.6 THz and 3000 K at 2.5 THz while it increased by a factor of 3 towards 8 GHz.
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Loudkov, D., Khosropanah, P., Cherednichenko, S., Adam, A., MerkeI, H., Kollberg, E., et al. (2002). Broadband fourier transform spectrometer (FTS) measurements of spiral and double-slot planar antennas at THz frequencies. In Proc. 13th Int. Symp. Space Terahertz Technol. (pp. 373–369).
Abstract: The direct responses of NbN phonon-cooled hot electron bolometer (HEB) mixers, integrated with different planar antennas, are measured, using Fourier Transform Spectrometer (F1S). One spiral antenna and several double slot antennas, designed for 0.6, 1.4, 1.6, 1.8 and 2.5 THz central frequencies, are investigated. The Optimization of the measurement set-up is discussed in terms of the beam splitter and the F11S-to-HEB coupling. The result shows that the spiral antenna is circular polarized and has a bandwidth of about 2 THz. The frequency bands of double slot antennas show some shift from the design values and their relative bandwidth increases by increasing the design frequency. The antenna responses do not depend on the HEB bias point and temperature, as long as the device is in the resistive state.
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