Novel method for calculating the noise figure of microwave MESFET mixers
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Abstract:
A new computer analysis method is presented by which the noise contributions of the various noise sources within a MESFET mixer can be determined and its overall single sideband and double sideband noise figure and noise temperature calculated. The method extends Kerr's work on diode type mixers and utilises a frequency conversion matrix of a MESFET mixer which was described previously. The simulation program was run for a mixer circuit based on an NEC720 transistor, and the results for the noise sources and noise figure behaviour as functions of the LO power are presented and compared to measured values with good agreement. An optimal operating point from the standpoint of minimum noise figure can thus be determined for transistor biasing conditions and the LO input power.Keywords:
MESFET
Noise temperature
Noise generator
Flicker noise
Noise-figure meter
The accuracy of microwave-amplifier noise measurements is affected by 1) the uncertainty of the temperatures of the reference noise sources as seen at the amplifier input terminals, 2) the error in reading the output noise power from the amplifier, 3) mismatches between reference noise sources and the amplifier, and 4) the uncertainty of amplifier gain, aside from short-time gain drift. The influence of all these errors is evaluated which leads to the conclusion that the accuracy of measuring effective input noise temperatures below 60° K is greatly improved by employing a refrigerated microwave noise source, preferably at liquid helium-temperature. Finally, such a refrigerated noise source that uses WR-137 waveguide is described with all relevant details for its construction and calibration. The measurements were performed at 5.8 Gc/s. In the Appendix a "universal" error plot is discussed which enables one to predict the best possible accuracy of noise measurements for any combination of reference and noise temperatures.
Y-factor
Noise temperature
Noise generator
Noise-figure meter
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When measuring the phase fluctuation between a pair of low-power microwave signals, the signals must be amplified before detection. In such cases, the phase noise of the amplifier pair is the main cause of 1/f background noise of the instrument. This article proposes a scheme that makes amplification possible while rejecting the close-in 1/f (flicker) noise of the two amplifiers. The noise rejection, which relies upon an understanding of the amplifier noise mechanism, does not require averaging. Therefore, our scheme can also be the detector of a closed-loop noise reduction system. The first prototype, compared to a traditional saturated mixer system under the same conditions, shows a 24 dB noise reduction in the 1/f region.
Flicker noise
Noise generator
Noise temperature
Burst noise
Noise spectral density
Y-factor
Noise power
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A complete analysis and measurement of the noise figure of Raman amplifiers is reported. The standard noise figure definition derived from the amplified spontaneous emission approach is discussed. A new approach, based on the field fluctuations, is proposed. It takes into account the vacuum fluctuation as a minimum noise level fit the amplifier input and as a contribution to the noise generation. As a result, the noise of a phase-insensitive amplifier is shown to be generated by the input noise amplification, the intrinsic amplification and attenuation mechanisms. This model enables to exactly define the noise figure as the degradation of the optical signal-to-noise ratio, which is in complete agreement with the practice of the IEEE standard.
Noise temperature
Noise generator
Noise-figure meter
Y-factor
Noise spectral density
Burst noise
Flicker noise
Raman amplification
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The effective noise temperature of the output impedance of a Iossy passive network at an arbitrary noise temperature connected to one or more resistive loads at arbitrary noise temperature lies between the highest and the lowest of these noise temperatures, as determined by the losses between the output terminals and the loads. The determination of the effective noise temperature of a gas-discharge noise generator over a wide frequency range is simplified by the substitution of a loss measurement for the more difficult noise temperature measurement. For minimum-noise radar applications care must be used in considering the excess noise of crystal mixers and gas-discharge duplexers. The influeuce of galactic radiation on a receiving system is such that there is an optimum frequency in the region of 200 to 600 mc for minimum "operating noise figure." Typical examples of radio-astronomy measurements are amenable to analysis of the type given. Finally, several corrections to measured noise figure are analyzed.
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Noise spectral density
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Formulas for the noise figure, and the minimum noise figure of a multi-link distributed amplifier have been developed. In addition, a relatively simple approximation formula has been devised that predicts the minimum noise figure of a practical amplifier design with good accuracy up to frequencies of 9 GHz. Finally, after the dependence of the noise characteristics on the circuit parameters is discussed, the noise figures of a 2--18-GHz three-link module are computed and compared with those measured on an actual amplifier. The measured data across the 2--18-GHz band compare favorably with the computed results. Measurements and theory agree that only small improvements in noise figure may he achieved, when noise matching the module's input impedance.
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Noise-figure meter
Noise temperature
Noise generator
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Abstract The sections in this article are Thermal Noise Noise Resistance and Conductance Noise Temperature Shot Noise Flicker Noise Excess Noise Burst Noise Noise Bandwidth Measuring Noise Addition of Noise Signals v n – i n AMPLIFIER NOISE MODEL Signal‐to‐Noise Ratio Noise Factor and Noise Figure Noise in Multistage Amplifiers Noise Reduction with Parallel Devices Noise Reduction with an Input Transformer Junction Diode Noise Model Noise in Bipolar Junction Transistors Noise in Feedback Amplifiers Noise in Field Effect Transistors Comparison of the Bipolar Junction Transistor and the Field Effect Transistor Operational Amplifier Noise
Flicker noise
Noise temperature
Noise generator
Noise spectral density
Burst noise
Y-factor
Noise-figure meter
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Flicker noise
Noise generator
Burst noise
Y-factor
Noise temperature
Noise spectral density
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The FM noise spectrum of a Gunn diode operated in any microwave circuit may be calculated from three noise parameters and the results of simple microwave measurements. These three noise parameters, one describing thermal noise properties and two describing flicker noise properties are assigned to each diode as a result of noise measurements made in a standard test circuit.
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Noise generator
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Noise-figure meter
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Oscillator phase noise
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Flicker noise
Noise generator
Burst noise
Noise temperature
Y-factor
Noise spectral density
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Resistance noise is an expression of the coupling of thermal and electrical fluctuations. The saturated vacuum diode can be used as a noise source for measurement purposes. The derivation of the Nyquist formula for the thermal noise of resistors from the RC circuit is a simple plausibility consideration, not a physically strict procedure. The question of frequency limitation is clarified by the connection with Planck's radiation formula. In non-metallic conductors, there is additional noise caused by the current flow. The current noise is related to another noise source, which is extremely important in active electronic components. It is the shot noise. Closely related to the physics of thermal noise of resistors is the noise of the positive column of a gas discharge plasma. Inadequate contacts of semiconductor laser diodes are detected by the noise of the operating current.
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Noise generator
Johnson–Nyquist noise
Noise temperature
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Noise spectral density
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