Modelling and performance of Nb SIS mixers in the 1.3 mm and 0.8 mm bands

We describe the modeling and subsequent improvements of SIS waveguide mixers for the 200-270 and 330-370 GHz bands (Blundell, Carter, and Gundlach 1988, Carter et al 1991). These mixers are constructed for use in receivers on IRAM radiotelescopes on Pico Veleta (Spain, Sierra Nevada) and Plateau de Bure (French Alps), and must meet specific requirements. The standard reduced height waveguide structure with suspended stripline is first analyzed and a model is validated through comparison with scale model and working scale measurements. In the first step, the intrinsic limitations of the standard mixer structure are identified, and the parameters are optimized bearing in mind the radioastronomical applications. In the second step, inductive tuning of the junctions is introduced and optimized for minimum noise and maximum bandwidth. In the 1.3 mm band, a DSB receiver temperature of less than 110 K (minimum 80 K) is measured from 180 through 260 GHz. In the 0.8 mm band, a DSB receiver temperature of less than 250 K (minimum 175 K) is obtained between 325 and 355 GHz. All these results are obtained with room-temperature optics and a 4 GHz IF chain having a 500 MHz bandwidth and a noise temperature of 14 K

Design and characterization of 225-370 GHz DSB and 247-360 GHz SSB full height waveguide SIS mixers

We report on the design and characterization of two full height waveguide SIS mixers for astronomical applications: a Double Side Band (DSB) fixed-tuned mixer covering the 225-370 GHz band ($\approx$ 50% of relative bandwidth), and a tunable Single Side Band (SSB) mixer covering the 247-360 GHz frequency range. The DSB receiver noise temperature we have measured is below 50 K over a bandwidth larger than 100 GHz for the DSB mixer and has a minimum of 27 K (uncorrected) at 336 GHz; to our knowledge this is the lowest noise ever reported at this frequency. A receiver noise temperature below 80 K and an image band rejection around -14 dB were measured over most of the band of the SSB mixer. Both mixers use similar chips that integrate a parallel tuning inductor with a radial microstrip stub to compensate for the junction capacitance of 75 fF (junction size 1 $\mu$m$^2$). A stability criterion for intrinsically DSB and SSB mixers under typical operating conditions has been derived. The receiver designs have been optimised in order to guarantee a low mixer noise temperature while maintaining adequate gain and stable operation over the whole frequency bands of interest

The NIKA2 Instrument at 30-m IRAM Telescope: Performance and Results

The New IRAM KID Arrays 2 (NIKA2) consortium has just finished installing and commissioning a millimetre camera on the IRAM 30-m telescope. It is a dual-band camera operating with three frequency-multiplexed kilo-pixels arrays of lumped element kinetic inductance detectors (LEKID) cooled at 150 mK, designed to observe the intensity and polarisation of the sky at 260 and 150 GHz (1.15 and 2 mm). NIKA2 is today an IRAM resident instrument for millimetre astronomy, such as intracluster medium from intermediate to distant clusters and so for the follow-up of Planck satellite detected clusters, high redshift sources and quasars, early stages of star formation and nearby galaxies emission. We present an overview of the instrument performance as it has been evaluated at the end of the commissioning phase