Noise temperature, gain bandwidth and local oscillator power of NbN phonon-cooled HEB mixer at terahertz frequencies

We present the performances of HEB mixers based on 3.5 nm thick NbN film integrated with log-periodic spiral antenna. The double side-band receiver noise temperature values are 1300 K and 3100 K at 2.5 THz and at 3.8 THz, respectively. The gain bandwidth of the mixer is 4.2 GHz and the noise bandwidth is 5 GHz. The local oscillator power is 1-3 /spl mu/W for mixers with different active area.

Introduction

Currently, many terahertz radio astronomy projects and research efforts are aimed at studying the atmosphere of the Earth. Generally, if such a project is directed to the measurements at frequencies over 1.2 THz then HEB mixers that have no competitive analogues for this frequency range are used As a rule, astronomical and atmospheric missions require a receiver of linearly polarized radiation in a relatively narrow frequency band which matches the LO frequency. In this case the optimal solution is to use a mixer with a well-studied plane polarized twin slot antenna for which the band is centered to a given frequency. This is the direction of the research efforts of diverse scientific groups. In particular, such projects as TELIS [1] and HERSCHEL [2] in the terahertz frequency range are oriented to building a heterodyne receiver which has a 1.8 THz channel and a heterodyne spectrometer which has two channels at 1.41–1.91 THz, respectively.