Westig, Marc Peter ORCID: 0000-0002-2227-3240, Justen, Matthias, Jacobs, Karl, Stutzki, Juergen, Schultz, Michael, Schomacker, Florian and Honingh, Netty (2012). A 490GHz planar circuit balanced Nb-Al2O3-Nb quasiparticle mixer for radio astronomy: Application to quantitative local oscillator noise determination. J. Appl. Phys., 112 (9). MELVILLE: AMER INST PHYSICS. ISSN 0021-8979

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This article presents a heterodyne experiment which uses a 380-520 GHz planar circuit balanced Nb-Al2O3-Nb superconductor-insulator-superconductor (SIS) quasiparticle mixer with 4-8 GHz instantaneous intermediate frequency (IF) bandwidth to quantitatively determine local oscillator (LO) noise. A balanced mixer is a unique tool to separate noise at the mixer's LO port from other noise sources. This is not possible in single-ended mixers. The antisymmetric IV characteristic of a SIS mixer further helps to simplify the measurements. The double-sideband receiver sensitivity of the balanced mixer is 2-4 times the quantum noise limit h nu = k(B) over the measured frequencies with a maximum LO noise rejection of 15 dB. This work presents independent measurements with three different LO sources that produce the reference frequency but also an amount of near-carrier noise power which is quantified in the experiment as a function of the LO and IF frequency in terms of an equivalent noise temperature T-LO. Two types of LO sources are used: a synthesizer driven amplifier/multiplier chain and a Gunn oscillator driven multiplier chain. With the first type of LO we find different near-carrier noise contributions using two different power pre-amplifiers of the LO system. For one of the two power pre-amplifiers we measure T-LO = 30 +/- 4K at the LO frequency 380GHz and T-LO = 38 +/- 10K at 420GHz. At the frequency band center 465 GHz of the Gunn driven LO we measure a comparable value of T-LO 32 +/- 6K. For the second power pre-amplifier, a significant higher T-LO value of the synthesizer driven LO is found which is up to six times larger compared with the best values found for the Gunn driven LO. In a second experiment, we use only one of two SIS mixers of the balanced mixer chip in order to verify the influence of near-carrier LO noise power on a single-ended heterodyne mixer measurement. We find an IF frequency dependence of near-carrier LO noise power. The frequency-resolved IF noise temperature slope is flat or slightly negative for the single-ended mixer. This is in contrast to the IF slope of the balanced mixer itself which is positive due to the expected IF roll-off of the mixer. This indicates a higher noise level closer to the LO's carrier frequency. Our findings imply that near-carrier LO noise has the largest impact on the sensitivity of a receiver system which uses mixers with a low IF band, for example, superconducting hot-electron bolometer HEB mixers. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764324]

Item Type: Journal Article
CreatorsEmailORCIDORCID Put Code
Westig, Marc PeterUNSPECIFIEDorcid.org/0000-0002-2227-3240UNSPECIFIED
URN: urn:nbn:de:hbz:38-479440
DOI: 10.1063/1.4764324
Journal or Publication Title: J. Appl. Phys.
Volume: 112
Number: 9
Date: 2012
Place of Publication: MELVILLE
ISSN: 0021-8979
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
MILLIMETERMultiple languages
Physics, AppliedMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/47944


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