Universität zu Köln

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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Abstract

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
Creators:	Creators Email ORCID ORCID Put Code Westig, Marc Peter UNSPECIFIED orcid.org/0000-0002-2227-3240 UNSPECIFIED Justen, Matthias UNSPECIFIED UNSPECIFIED UNSPECIFIED Jacobs, Karl UNSPECIFIED UNSPECIFIED UNSPECIFIED Stutzki, Juergen UNSPECIFIED UNSPECIFIED UNSPECIFIED Schultz, Michael UNSPECIFIED UNSPECIFIED UNSPECIFIED Schomacker, Florian UNSPECIFIED UNSPECIFIED UNSPECIFIED Honingh, Netty UNSPECIFIED UNSPECIFIED UNSPECIFIED
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
Publisher:	AMER INST PHYSICS
Place of Publication:	MELVILLE
ISSN:	0021-8979
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MILLIMETER Multiple languages Physics, Applied Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/47944