TY  - CONF
AU  - Ekström, H.
AU  - Karasik, B.
AU  - Kollberg, E.
AU  - Gol'tsman, G.
AU  - Gershenzon, E.
PY  - 1995
DA  - 1995//
TI  - 350 GHz NbN hot electron bolometer mixer
T2  - Proc. 6[super:th] Int. Symp. Space Terahertz Technol.
BT  - Proc. 6[super:th] Int. Symp. Space Terahertz Technol.
SP  - 269
EP  - 283
KW  - NbN HEB mixers
AB  - Superconducting NbN hot-electron bolometer (HEB) mixer devices have been fabricated and measured at 350 GHz. The HEB is integrated with a double dipole antenna on an extended crystalline quartz hyper hemispherical substrate lens. Heterodyne measurement gave a -3 dB bandwidth, mainly determined by the electron- phonon interaction time, of about 680 and 1000 MHz for two different films with Tc = 8.5 and 11 K respectively. The measured DSB receiver noise temperature is around 3000 K at 800 MHz IF frequency. The main contribution to the output noise from the device is due to electron temperature fluctuations with the equivalent output noise temperature TFL-100 K. TH, has the same frequency dependence as the IF response. The contribution from Johnson noise is of the order of T. The RF coupling loss is estimated to be = 6 dB. The film with lower Tc, had an estimated intrinsic low-frequency conversion loss = 7 dB, while the other film had a conversion loss as high as 14 dB. The difference in intrinsic conversion loss is explained by less uniform absorption of radiation. Measurements of the small signal impedance shows a transition of the output impedance from the DC differential resistance Rd=dV/dI in the low frequency limit to the DC resistance R 0 =Uoff 0 in the bias point for frequencies above 3 GHz. We judge that the optimum shape of the IV-characteristic is more easily obtained at THz frequencies where the main restriction in performance should come from problems with the RF coupling.
UR  - https://www.nrao.edu/meetings/isstt/1995.shtml
N1  - exported from refbase (https://db.rplab.ru/refbase/show.php?record=1628), last updated on Thu, 15 Jul 2021 00:29:58 -0500
ID  - Ekstroem_etal1995
ER  -