A 0.5 THz Sideband Separation SIS Mixer for APEX Telescope

Raquel Monje; Victor Belitsky; Vessen Vassilev; Alexey Pavolotskiy; Igor Lapkin; Vincent Desmaris; Denis Meledin; Doug Henke; Dimitar Milkov Dochev

A 0.5 THz Sideband Separation SIS Mixer for APEX Telescope
Paper i proceeding, 2008

We present the design and the experimental results of a fixed-tuned sideband-separating superconductor-insulator-superconductor (SIS) mixer for 385 - 500 GHz. The sideband separation is achieved using a quadrature scheme, where two separate DSB mixer blocks are combined with an intermediate waveguide component containing the LO waveguide distribution circuitry and RF waveguide hybrid. The intermediate waveguide piece is fabricated by using copper micromachining, which gives dimensions’ accuracy better than 1 μm. The RF signal coming from the waveguide hybrid is coupled to the SIS junctions through an E-probe with integrated bias-T. We implemented an on-chip LO injection solution, where the LO coupler is integrated onto the mixer chip and fabricated together with the SIS junction and the tuning circuitry. The on-chip LO coupler is made as a combination of superconducting microstrip lines and slot-lines (branches), which gives almost a lossless solution. With the fabrication accuracy better than 0.5 μm by using optical lithography, the circuitry is proven to give a good performance following the simulations expectations.