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Semenov AD, Hübers H–W, Schubert J, Gol'tsman GN, Elantiev AI, Voronov BM, et al. Frequency dependent noise temperature of the lattice cooled hot-electron terahertz mixer. In: Proc. 11th Int. Symp. Space Terahertz Technol.; 2000. p. 39–48.
Abstract: We present the measurements and the theoretical model on the frequency dependent noise temperature of a lattice cooled hot electron bolometer (HEB) mixer in the terahertz frequency range. The experimentally observed increase of the noise temperature with frequency is a cumulative effect of the non-uniform distribution of the high frequency current in the bolometer and the charge imbalance, which occurs near the edges of the normal domain and contacts with normal metal. In addition, we present experimental results which show that the noise temperature of a HEB mixer can be reduced by about 30% due to a Parylene antireflection coating on the Silicon hyperhemispheric lens.
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Cherednichenko S, Kroug M, Yagoubov P, Merkel H, Kollberg E, Yngvesson KS, et al. IF bandwidth of phonon cooled HEB mixers made from NbN films on MgO substrates. In: Proc. 11th Int. Symp. Space Terahertz Technol.; 2000. p. 219–27.
Abstract: An investigation of gain and noise bandwidth of phonon-cooled hot-electron bolometric (HEB) mixers is presented. The radiation coupling to the mixers is quasioptical through either a spiral or twin-slot antenna. A maximum gain bandwidth of 4.8 GHz is obtained for mixers based on a 3.5 nm thin NbN film with Tc= 10 K. The noise bandwidth is 5.6 GHz, at the moment limited by parasitic elements in the, device mount fixture. At 0.65 THz the DSB receiver noise temperature is 700-800 К in the IF band 1-2 GHz, and 1150-2700 К in the band 3.5-7 GHz.
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Schubert J, Semenov A, Gol'tsman G, Hübers H-W, Schwaab G, Voronov B, et al. Noise temperature and sensitivity of a NbN hot-electron mixer at frequencies from 0.7 THz to 5.2 THz. In: Proc. 10th Int. Symp. Space Terahertz Technol.; 1999. p. 190–9.
Abstract: We report on noise temperature measurements of a NbN phonon-cooled hot-electron bolometric mixer at different bias regimes. The device was a 3 nm thick bridge with in-plane dimensions of 1.7 x 0.2 gm 2 integrated in a complementary logarithmic spiral antenna. Measurements were performed at frequencies ranging from 0.7 THz up to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 2600 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz) 5600 K (4.3 THz) and 8800 K (5.2 THz). Two bias regimes are possible in order to achieve low noise temperatures. But only one of them yields sensitivity fluctuations close to the theoretical limit.
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Gerecht E, Musante CF, Jian H, Zhuang Y, Yngvesson KS, Dickinson J, et al. Improved characteristics of NbN HEB mixers integrated with log-periodic antennas. In: Proc. 10th Int. Symp. Space Terahertz Technol.; 1999. p. 200–7.
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Yagoubov P, Kroug M, Merkel H, Kollberg E, Hübers H-W, Schubert J, et al. NbN hot electron bolometric mixers at frequencies between 0.7 and 3.1 THz. In: Proc. 10th Int. Symp. Space Terahertz Technol.; 1999. p. 238–46.
Abstract: The performance of NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixers is investigated in the 0.7-3.1 THz frequency range. The devices are made from a 3.5-4 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The length of the bolometer microbridge is 0.1- 0.2 gm, the width is 1-2 gm. The best results of the DSB receiver noise temperature measured at 1.5 GHz intermediate frequency are: 800 K at 0.7 THz, 1100 K at 1.6 THz, 2000 K at 2.5 THz and 4200 K at 3.1 THz. The measurements were performed with a far infrared laser as the local oscillator (LO) source. The estimated LO power required is less than 500 nW at the receiver input. First results on the spiral antenna polarization measurements are reported.
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