Development of the ALMA-North America sideband-separating SIS mixers

Abstract

Fig. 1. Phasing type of sideband-separating mixer as used in the ALMA Band-3 and -6 SIS receivers. Fig. 2. For a typical Band-6 SIS receiver, contours of (a) mixer gain dB (solid orange lines) and (b) receiver noise temperature (solid blue lines), plotted on a Smith chart of the RF source impedance normalized to the optimum source impedance R opt . The gray contours are the IF output resistance of the mixer normalized to R opt : solid gray lines indicate positive output resistance and dashed gray lines indicate negative output resistance. The squiggly gray line indicates the transition from positive to negative output resistance. The dashed gray circle at |ȡ| = 0.4 indicates the desirable operating region.Abstract -As ALMA nears completion, 73 dual-polarization receivers have been delivered for each of Bands 3 (84-116 GHz) and 6 (211-275 GHz). The receivers use sideband-separating superconducting tunnel-junction (SIS) mixers, developed for ALMA to suppress atmospheric noise in the image band. The mixers were designed taking into account input return loss, dynamic range and signal-to-image conversion (which can degrade the image rejection). Results are given for typical production receivers.

The 1.3mm Full-Stokes Polarization System at CARMA

“…Although at ALMA these devices are used in SB-separating mixers (Kerr et al, 2013), the CARMA mixers are a simple double sideband (DSB) design. An advantage of this design is that the LO can be coupled into the mixer via a beamsplitter mounted outside the dewar.…”

Efficiency of the Image Band Suppression in Sideband Separating SIS Receivers for Radio Astronomy

“…They were mainly trying to optimize the balance of individual receiver components: RF and IF hybrids and mixers gain, and the imbalance of each part was reduced to a level below 0.5 dB. Still, a total imbalance of 1.5 dB would give IRR better than 20 dB in the entire band, but in reality it was only 10 dB in the worst points [2], [3]. In our work we focused on study of the SRR pattern of the 2SB receiver by analysis of the entire receiver RF and IF structures.…”

The ALMA North American receivers

“…Low-noise performance for both bands is obtained using Superconducting-Insulating-Superconducting (SIS) mixers [6] operating at physical temperatures near 4 K. Both Band 3 and Band 6 mixers employ Nb/Al-oxide/Nb junction designs fabricated by the University of Virginia Microelectronics Laboratory. Single-sideband operation is obtained by routing signals in quadrature through two component mixer chips and extracting separately both upper (USB) and lower (LSB) sidebands using an IF quadrature hybrid, as shown in the top of Fig.…”