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Noise in lossless microwave multiports
Author(s) -
GarcíaGarcía Q.
Publication year - 2004
Publication title -
international journal of rf and microwave computer‐aided engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.335
H-Index - 39
eISSN - 1099-047X
pISSN - 1096-4290
DOI - 10.1002/mmce.10122
Subject(s) - lossless compression , noise temperature , y factor , effective input noise temperature , noise figure , noise (video) , circulator , electronic engineering , noise generator , microwave , electrical engineering , computer science , electronic circuit , antenna noise temperature , attenuator (electronics) , acoustics , antenna (radio) , telecommunications , physics , engineering , bandwidth (computing) , optics , attenuation , amplifier , algorithm , dipole antenna , artificial intelligence , image (mathematics) , antenna aperture , data compression
This article addresses the noise behaviour (noise temperature and noise figure) of some passive microwave multiport circuits. The analysis method is based on the noise‐wave formulation. With the exception of the attenuator case, which is used as a reference, the circuit elements considered are lossless devices, in the sense that neither conductive nor dielectric losses are accounted for. The analysis shows that, when connected to matched loads in some of their ports, these multiports circuits lose their lossless nature and their scattering matrix is not unitary; therefore, they generate thermal noise. The article addresses and formalizes mathematically the noise properties of a number of lossless microwave devices such as N ‐port power splitters, circulators, and hybrid couplers. While the noise‐wave mathematical formulation may be cumbersome in some cases, all the devices and configurations analyzed in this work have been characterized in terms of noise figure and noise temperature, which is a much more practical approach in most situations. Some implications of the use of these devices and configurations in antenna arrays for antenna noise temperature evaluations have been also addressed. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 99–110, 2004.