Wyss, R. A., Karasik, B. S., McGrath, W. R., Bamble, B., & LeDuc, H. (1999). Noise and bandwidth measurements of diffusion–cooled Nb hot–electron bolometer mixers at frequencies above the superconductive energy gap. In _Proc. 10th Int. Symp. Space Terahertz Technol._ (pp. 215–229). Charlottesville, Virginia.