Quantum noise in SIS mixers
Conference
·
· IEEE Trans. Magn.; (United States)
OSTI ID:6389144
A quantum-statistical analysis of the signal and noise performance of the quasiparticle (SIS) heterodyne mixers is presented. In contrast with the earlier theories, the quantum properties of the signal source have been taken into consistent consideration. In the quantum range of sensitivity the noise properties of the mixer can be characterized by the noise parameter theta /SUB N/ introduced earlier for the parametric amplifiers/sup 1/. Using the conventional 3-port model of the mixer circuit and the microscopic theory of the superconducting tunnel junctions we have obtained a general expression for theta /SUB N/ and evaluated it numerically for various quasiparticle current step widths, dc bias voltages, local oscillator powers, signal frequencies ..omega.. /SUB s/ , signal source admittances Y /SUB s/ and operation temperatures T. In a reasonable range of these parameters, theta /SUB N/ DSB has turned out to be less than the so-called quantum limit KAPPA..omega.. /SUB s/ /2. On the contrary, in the single sideband mode of the mixer performance, theta /SUB N/ is always larger than KAPPA..omega.. /SUB s/ /2. The difference between the two modes of operation is discussed from the point of view of the quantum theory of measurements.
- Research Organization:
- Department of Physics, Moscow State University, Moscow
- OSTI ID:
- 6389144
- Report Number(s):
- CONF-840937-
- Conference Information:
- Journal Name: IEEE Trans. Magn.; (United States) Journal Volume: MAG-21:2
- Country of Publication:
- United States
- Language:
- English
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