ISSTT Proceedings

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Design of Sideband Separation SIS Mixer for 3 mm Band

Authors:
V. Vassilev, V. Belitsky
Abstract:
As a part of Onsala development of a single sideband mixer for ALMA band 7 (275-370 GHz), we present the design of a prototype sideband separation mixer for 85-115 GHz. The mixer is designed using a quadrature scheme with two identical DSB SIS mixers pumped by a local oscillator (LO) with 90° phase difference. The mixer employs a new device, a double-probe coupler, which splits the input RF signal and provides transition from a waveguide to a microstrip line, allowing the integration of all mixer components on the same compact substrate and thus ensure a high degree of similarity in the SIS junction performance and the geometry of all the mixer elements including integrated tuning circuitry. The RF and the LO power are coupled on the substrate by using microstrip directional coupler; the remaining LO power at the idle port of the coupler is terminated by unbiased (or weakly biased) SIS junction acting as a lumped load. To obtain feasible dimensions of the LO directional coupler and the SIS tuning circuitry the mixer is designed using two types of dielectric: 150 µm thick crystal quartz substrate and two layers (400 nm and 200 nm) of sputtered SiO2. The presence of the two dielectrics (quartz and SiO2) requires step in the ground plane, which is achieved by using a choke structure as a virtual ground.
Categories:
SIS Mixers
Year:
2001
Session:
8
Full-text:
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Page Number(s):
373-382