Performance of the flight model HIFI band 3 and 4 mixer units

Abstract

We describe the performance of the Band 3 and Band 4 Flight Model mixer units for Herschel/HIFI Instrument. These units are part of the Focal Plane Unit of HIFI. The band 3 and 4 mixer units cover the 800-960 GHz and 960-1120 GHz frequency range and have a 4-8 GHz IF frequency band. The sensitivities of the mixers within the HIFI setting are excellent and are the best reported to date. The DSB receiver noise performance in the HIFI FPU environment ranges from 150 K at 800 GHz to 350 K at 1120 GHz. This sensitivity and the absence of atmospheric attenuation will reduce the necessary observation time for astronomical observations in this frequency range by at least two orders of magnitude compared to ground based facilities.

A field-deployed 810 GHz receiver incorporating a superconducting mixer developed for herschel space telescope and a SiGe low noise amplifier

“…A Y-factor of 1.7 was recorded, which translates into a receiver system noise temperature of 235 K (Rayleigh-Jeans temperature), averaged over the entire IF pass-band. This sensitivity compares favorably to the lab measurements reported by the HIFI Band-3 development team [9] given that our bath temperature is at 4.2 K and the entire optics train is included in our measurement.…”

“…The details of the design and construction of the mixer is described in [9]. We have installed the mixer block in a liquid helium cooled cryostat equipped with an anti-reflection coated quartz vacuum window and infra-red blocking filters.…”

SIS Mixer Fabrication for ALMA Band10

“…With minimum noise temperatures comparable to those of state of the art receivers [5], [6], we conclude that high coupling efficiency can be achieved, indicating that the quality of materials in the embedding circuit probably is sufficient. At the same time it is obvious that these mixers can not meet the ALMA specifications over the full band.…”

“…For and a waveguide coupling scheme, the best results have been obtained using standard junctions and a tuning circuit. Examples are instruments like CHAMP+ and Herrschel Band3 [5], [6]. With their rf bands being almost identical to that of ALMA Band10, 790 GHz-950 GHz, our choices for mixer design and fabrication technology are similar to those already being tested during the development of above mentioned instruments.…”

High-Gap Nb-AlN-NbN SIS Junctions for Frequency Band 790–950 GHz

“…For the high band mixers, on the other hand, a one-off design was made, without further modifications and iterations. Because of this, the performance of the high-band mixers was not optimized as far as the low band mixers, and can not be considered state of the art as compared with similar devices [3], [4].…”