Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

IEEE Transactions on Applied Superconductivity

Constant output noise temperature of the superconducting quasiparticle mixer

Qing Ke, M. J. Feldman

Published Mar 1, 1993• 13 citations
Publisher

Abstract

The output noise temperature, rather than the standard input noise temperature, is shown to be the fundamental measure of the shot noise of the superconducting (SIS) quasiparticle mixer. This conclusion is based on extensive numerical computations of the properties of optimized SIS (superconductor-insulator-superconductor) receivers and also on analytic calculations with separate consideration of correlated and uncorrelated noise sources. The quantum theory of mixing is used to derive a simple analytic expression for the mixer output noise which is independent of frequency, and qualitatively explains the dependence of the output temperature on each of the receiver's operating parameters. The derivation leads to a novel understanding of the SIS mixer which, distinguishes between its correlated and uncorrelated noise sources. The authors predict T(receiver)=2*T(mixer) for many SIS receivers. Numerous experiments substantiate the analysis.>

DOI
10.1109/77.233557

Related papers

Frequency dependence of quasiparticle mixers

W. C. Danchi, Edmund C. Sutton

An analysis of the frequency dependence of superconductor-insulator-normal (SIN) and superconductor-insulator-superconductor (SIS) quasiparticle mixers is presented. Power-law expressions for conversion loss and mixer shot-noise temperature for the double-sideband SIN mixer are derived from the Tucker theory for the case of a source conductance which is small compared to the conductance of the junction. For an ideal SIN tunnel junction at T=0 the mixer conversion efficiency is shown to decrease approximately linearly with frequency up to f=Δ/h. From f=Δ/h to 2Δ/h the conversion efficiency remains approximately constant, while above f=2Δ/h it rolls off as the inverse square of the frequency. Expressions for the shot-noise contribution to the mixer noise temperature are also derived. At frequencies up to f=Δ/h the noise temperature rises as the square root of the frequency. From f=Δ/h to f=2Δ/h the noise temperature of the mixer increases linearly with frequency, whereas above f=2Δ/h it rises as the cube of the frequency. Conversion efficiency and noise temperature are also calculated numerically for the SIN mixer. Good agreement is found between the frequency dependencies calculated analytically in the limit of small local oscillator power and the numerical calculations for optimal pumping. The frequency dependence of the nonideal SIS junction is also analyzed, and shown to yield similar results, with the characteristic frequencies Δ/h and 2Δ/h for a SIN mixer transformed into 2Δ/h and 4Δ/h, respectively. Expressions also are derived for the saturation power as a function of frequency.

Journal of Applied Physics•Dec 1, 1986•33 citations

Noise parameters of SIS mixers

Larry R. D’Addario

It has been shown that low-noise receivers can be constructed at millimeter wavelengths by using mixers containing superconducting tunnel junctions as the nonlinear elements. This is possible because of both the low intrinsic noise of these devices and their potential for high conversion gain. Here, the quantum theory of mixing is used to derive the full-noise parameters and small-signal parameters of sinusoidally pumped SIS (superconductor-insulator-superconductor) junctions. These are then put into a form that allows the theory of two-port linear networks to be brought to bear, allowing calculation of such useful parameters as minimum noise temperature, optimum source impedance, available (or exchangeable) gain at minimum noise, and stability factor. These quantities are properties of the pumped junction that do not depend on the source or load impedance, but do depend on the terminations at the image and harmonic sideband frequencies. The harmonic sidebands are taken to be shorted, and the image termination dependence is studied. Numerical results are presented for both ideal (BSC theory) and practical (measured current-voltage characteristic) junctions. The noise parameters of the cascade connection of an SIS mixer and a (noisy) IF amplifier are considered, leading to a specification of the optimum coupling network between the two. It is noted that the SIS mixer is usually not unconditionally stable, but that oscillation can be avoided by careful design of the IF coupling network.< >

IEEE Transactions on Microwave Theory and Techniques•Jul 1, 1988•19 citations

Noise in SIS microwave mixers

Aldert van der Ziel

It is proposed that the noise in an SIS (superconductor-insulator-superconductor) microwave mixer is shot noise, and that it can be treated in a similar manner to the noise in Schottky barrier diodes. A noise temperature is defined, and how it can be optimized is indicated. An extension of the noise temperature concept of the source is used that makes noise temperatures additive at all frequencies.

IEEE Journal of Quantum Electronics•May 1, 1983•2 citations

Optimum source conductance for high frequency superconducting quasiparticle receivers

Qing Ke, M. J. Feldman

The authors have used the quantum theory of mixing for extensive numerical calculations to determine the mixer source conductance G/sub s/ required to optimize a superconductor-insulator-superconductor (SIS) quasiparticle heterodyne receiver. The optimum G/sub s/ matches an empirical formula which can be understood by a simple derivation. Previous work indicated that G/sub s/ should vary inversely with frequency, and this implies that the critical current density of SIS junctions used for mixing should increase as frequency squared, a stringent constraint on the design of submillimeter SIS mixers. On the contrary, it was found that G/sub s/ is more weakly dependent upon frequency, and the implications for the design of submillimeter SIS mixers are discussed.>

IEEE Transactions on Microwave Theory and Techniques•Apr 1, 1993•22 citations

Signal and Image Port Output Power in the Quantum Theory of Mixing

Qing Ke, M. J. Feldman

The quantum theory of mixing is essential for the interpretation of experimental superconducting quasiparticle (SIS) mixers. When the bias and tuning parameters are known, the theory is quite successful at predicting the mixer performance, gain and noise temperature. However, the theory usually predicts much higher conversion gain for some other set of bias and tuning parameters, and this is not seen in experiment. Thus the theory is less useful for engineering design of SIS mixers. We believe we have resolved this longstanding discrepancy. We find there are two distinct optimum operation modes for ideal SIS mixers. The high gain mode predicted by the theory will not be accessible in real experiments. To understand this we present the equations of a DSB SIS mixer in a novel form, in terms of the complex plane phase angle between the amplitude modulation input admittance vector and the local oscillator input admittance vector.

Softwaretechnik-Trends•May 1, 1994•0 citations

Quantum noise in SIS mixers

Alexander B Zorin

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 ΘNintroduced earlier for the parametric amplifiers. 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 ΘNand evaluated it numerically for various quasiparticle current step widths, dc bias voltages, local oscillator powers, signal frequencies ωs, signal source admittances Ysand operation temperatures T. In a reasonable range of these parameters,\Theta_{N}^{DSB}has turned out to be less than the so-called quantum limith\omega_{s}/2. On the contrary, in the single sideband mode of the mixer performance, ΘNis always larger thanh\omega_{s}/2. The difference between the two modes of operation is discussed from the point of view of the quantum theory of measurements.

IEEE Transactions on Magnetics•Mar 1, 1985•19 citations
The output noise temperature, rather than the standard input noise temperature, is shown to be the fundamental measure of the shot noise of the superconducting (SIS) quasiparticle mixer. This conclusion is based on extensive numerical computations of the properties of optimized SIS (superconductor-insulator-superconductor) receivers and also on analytic calculations with separate consideration of correlated and uncorrelated noise sources. The quantum theory of mixing is used to derive a simple analytic expression for the mixer output noise which is independent of frequency, and qualitatively explains the dependence of the output temperature on each of the receiver's operating parameters. The derivation leads to a novel understanding of the SIS mixer which, distinguishes between its correlated and uncorrelated noise sources. The authors predict T(receiver)=2*T(mixer) for many SIS receivers. Numerous experiments substantiate the analysis.>
An analysis of the frequency dependence of superconductor-insulator-normal (SIN) and superconductor-insulator-superconductor (SIS) quasiparticle mixers is presented. Power-law expressions for conversion loss and mixer shot-noise temperature for the double-sideband SIN mixer are derived from the Tucker theory for the case of a source conductance which is small compared to the conductance of the junction. For an ideal SIN tunnel junction at T=0 the mixer conversion efficiency is shown to decrease approximately linearly with frequency up to f=Δ/h. From f=Δ/h to 2Δ/h the conversion efficiency remains approximately constant, while above f=2Δ/h it rolls off as the inverse square of the frequency. Expressions for the shot-noise contribution to the mixer noise temperature are also derived. At frequencies up to f=Δ/h the noise temperature rises as the square root of the frequency. From f=Δ/h to f=2Δ/h the noise temperature of the mixer increases linearly with frequency, whereas above f=2Δ/h it rises as the cube of the frequency. Conversion efficiency and noise temperature are also calculated numerically for the SIN mixer. Good agreement is found between the frequency dependencies calculated analytically in the limit of small local oscillator power and the numerical calculations for optimal pumping. The frequency dependence of the nonideal SIS junction is also analyzed, and shown to yield similar results, with the characteristic frequencies Δ/h and 2Δ/h for a SIN mixer transformed into 2Δ/h and 4Δ/h, respectively. Expressions also are derived for the saturation power as a function of frequency.
It has been shown that low-noise receivers can be constructed at millimeter wavelengths by using mixers containing superconducting tunnel junctions as the nonlinear elements. This is possible because of both the low intrinsic noise of these devices and their potential for high conversion gain. Here, the quantum theory of mixing is used to derive the full-noise parameters and small-signal parameters of sinusoidally pumped SIS (superconductor-insulator-superconductor) junctions. These are then put into a form that allows the theory of two-port linear networks to be brought to bear, allowing calculation of such useful parameters as minimum noise temperature, optimum source impedance, available (or exchangeable) gain at minimum noise, and stability factor. These quantities are properties of the pumped junction that do not depend on the source or load impedance, but do depend on the terminations at the image and harmonic sideband frequencies. The harmonic sidebands are taken to be shorted, and the image termination dependence is studied. Numerical results are presented for both ideal (BSC theory) and practical (measured current-voltage characteristic) junctions. The noise parameters of the cascade connection of an SIS mixer and a (noisy) IF amplifier are considered, leading to a specification of the optimum coupling network between the two. It is noted that the SIS mixer is usually not unconditionally stable, but that oscillation can be avoided by careful design of the IF coupling network.< >
The authors have used the quantum theory of mixing for extensive numerical calculations to determine the mixer source conductance G/sub s/ required to optimize a superconductor-insulator-superconductor (SIS) quasiparticle heterodyne receiver. The optimum G/sub s/ matches an empirical formula which can be understood by a simple derivation. Previous work indicated that G/sub s/ should vary inversely with frequency, and this implies that the critical current density of SIS junctions used for mixing should increase as frequency squared, a stringent constraint on the design of submillimeter SIS mixers. On the contrary, it was found that G/sub s/ is more weakly dependent upon frequency, and the implications for the design of submillimeter SIS mixers are discussed.>
The quantum theory of mixing is essential for the interpretation of experimental superconducting quasiparticle (SIS) mixers. When the bias and tuning parameters are known, the theory is quite successful at predicting the mixer performance, gain and noise temperature. However, the theory usually predicts much higher conversion gain for some other set of bias and tuning parameters, and this is not seen in experiment. Thus the theory is less useful for engineering design of SIS mixers. We believe we have resolved this longstanding discrepancy. We find there are two distinct optimum operation modes for ideal SIS mixers. The high gain mode predicted by the theory will not be accessible in real experiments. To understand this we present the equations of a DSB SIS mixer in a novel form, in terms of the complex plane phase angle between the amplitude modulation input admittance vector and the local oscillator input admittance vector.
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 ΘNintroduced earlier for the parametric amplifiers. 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 ΘNand evaluated it numerically for various quasiparticle current step widths, dc bias voltages, local oscillator powers, signal frequencies ωs, signal source admittances Ysand operation temperatures T. In a reasonable range of these parameters,\Theta_{N}^{DSB}has turned out to be less than the so-called quantum limith\omega_{s}/2. On the contrary, in the single sideband mode of the mixer performance, ΘNis always larger thanh\omega_{s}/2. The difference between the two modes of operation is discussed from the point of view of the quantum theory of measurements.