Bandwidth of a hot-electron bolometer mixer according to the hotspot model

Abstract

The hotspot model has been used to simulate the intermediate frequency bandwidth of a lattice cooled NbN hot-electron bolometer mixer. The results of simulation suggest that with the increase of the bias current, the bandwidth decreases, passes the minimum, and recovers again. The appearance of the bandwidth minimum correlates with experimentally observed noise maximum at the mixer output that drastically reduces the sensitivity of a relevant receiver. At large bias currents the bandwidth exceeds the reciprocal electron cooling time. Since the noise temperature also increases with the bias current, a compromise between the desirable bandwidth and acceptable noise temperature can be reached by varying the bias current.