摘要 :
A -band waveguide noise measurement system has been developed for noise temperature (NT) standards. The system consists of two standard noise sources and a waveguide radiometer. A horn-type cryogenic noise source operating at the ...
展开
A -band waveguide noise measurement system has been developed for noise temperature (NT) standards. The system consists of two standard noise sources and a waveguide radiometer. A horn-type cryogenic noise source operating at the liquid nitrogen temperature and an ambient temperature termination have been employed as standard noise sources. To measure noise power radiated from the noise sources including a device under test, a total-power waveguide radiometer has been constructed and its performance has been evaluated. Measured NT of a commercial waveguide noise source is presented with the measurement uncertainty of 0.10–0.13 dB () in -band.
收起
摘要 :
Measurements of the natural background levels of 50- and 60-Hz radio noise by ELF/VLF (extremely low frequency/very low frequency) radiometers located at various sites around the world are reported. The measurements are made on th...
展开
Measurements of the natural background levels of 50- and 60-Hz radio noise by ELF/VLF (extremely low frequency/very low frequency) radiometers located at various sites around the world are reported. The measurements are made on the magnetic fields of the noise using loop antennas, and they cover the first three harmonics of the power line frequencies (frequencies in the range 50-180 Hz). Due to the likelihood of contamination from local electrical power systems, or even from nonlocal systems, the measurements at each power line frequency were made at adjacent frequencies and the desired noise amplitudes obtained by interpolation. It is shown that the magnetic spectral densities of the natural noise typically lie in the range 20-600 fT/ square root Hz or, taking the 50/60-Hz frequencies specifically, in the range 150-600 fT/ square root Hz. These ranges should be typical for most locations on the Earth's surface and for most seasons.
收起
摘要 :
Two methods are presented for calibrating broadband highly mismatched noise sources. The first is a reformulation and an extension of the procedure used for very accurately calibrating matched noise sources. It uses isolators and ...
展开
Two methods are presented for calibrating broadband highly mismatched noise sources. The first is a reformulation and an extension of the procedure used for very accurately calibrating matched noise sources. It uses isolators and works whatever the source reflection factor. With the second method, the excess noise ratio of the noise source is numerically optimized until the measured reverse noise wave of an attenuator is equal to the theoretical value derived from its S-parameters. It can be applied to sources with reflection factors of about 0.45 to 0.90. Both methods appear to give very consistent results.
收起
摘要 :
A system to measure the noise temperature (NT) of noise sources is implemented in the frequency range of 18–26.5 GHz for the case where noise sources commercially available have only one nominal NT, e.g., 9500 K being equivalent ...
展开
A system to measure the noise temperature (NT) of noise sources is implemented in the frequency range of 18–26.5 GHz for the case where noise sources commercially available have only one nominal NT, e.g., 9500 K being equivalent to 15-dB excess noise ratio. For the Y-factor method, two noise sources, i.e., a noise source and another with a radio-frequency attenuator, serve as the standard noise sources. The noise power output of the noise sources are measured using a commercial noise figure measurement instrument. Measurement results are presented, and its uncertainty has been evaluated to be 0.23–0.25 dB $(k = 2)$ .
收起
摘要 :
This paper presents a novel AC/DC noise measurement system. This system simultaneously uses a high DC current to generate 1/f/sup 2/ noise (electromigration noise) in thin films and a low AC current to detect that noise. This new ...
展开
This paper presents a novel AC/DC noise measurement system. This system simultaneously uses a high DC current to generate 1/f/sup 2/ noise (electromigration noise) in thin films and a low AC current to detect that noise. This new system allows us to separate the noise components of metal thin films and is more stable and sensitive than its predecessors.
收起
摘要 :
This paper reports the formulation and results of a Monte Carlo study of uncertainties in noise-parameter measurements. The simulator permits the computation of the dependence of the uncertainty in the noise parameters on uncertai...
展开
This paper reports the formulation and results of a Monte Carlo study of uncertainties in noise-parameter measurements. The simulator permits the computation of the dependence of the uncertainty in the noise parameters on uncertainties in the underlying quantities. Results are obtained for the effect due to uncertainties in the reflection coefficients of the input terminations, the noise temperature of the hot noise source, connector variability, the ambient temperature, and the measurement of the output noise. Representative results are presented for both uncorrelated and correlated uncertainties in the underlying quantities. The simulation program is also used to evaluate two possible enhancements of noise-parameter measurements: the use of a cold noise source as one of the input terminations and the inclusion of a measurement of the "reverse configuration," in which the noise from the amplifier input is measured directly.
收起
摘要 :
The estimation of long-term noise indicators using a small sample involves type A measurement uncertainty which is dependent upon the size of the sample and its probability distribution. If the distribution function of the data is...
展开
The estimation of long-term noise indicators using a small sample involves type A measurement uncertainty which is dependent upon the size of the sample and its probability distribution. If the distribution function of the data is different from normal, alternative methods of uncertainty assessment must be applied rather than the classical law of uncertainty propagation. This paper presents an analysis of the probability distributions of one-day noise indicators calculated from data provided by noise monitoring of the city of Gdansk. The measurement data under analysis was comprehensive and diverse the data included a four-year period and sixty-nine measurement stations: noise of different origins was recorded: traffic noise, railway noise, industrial noise and aircraft noise. The data set was analysed in terms of determining the forms of probability distributions. Only for 3% of the analysed one-day noise indicators, were the distribution functions confirmed to be normal. In this case, using the classical method (the law of uncertainty propagation) for determining type A measurement uncertainty may lead to the erroneous determination of the uncertainty interval. Following analysis of the data set, the possibility of modelling the distributions of one-day noise indicators with a mixture of two normal distributions was verified. Such an approach would significantly simplify uncertainty determination using the non-classical method based on probability distribution propagation. It was indicated that 94% of the analysed samples are characterised by a distribution that is a mixture of two normal distributions. (C) 2019 Elsevier Ltd. All rights reserved.
收起
摘要 :
In this paper, we discuss a few techniques that allow an effective reduction of the background noise and/or the reduction of the measurement time when performing voltage noise measurements by employing a number of nominally identi...
展开
In this paper, we discuss a few techniques that allow an effective reduction of the background noise and/or the reduction of the measurement time when performing voltage noise measurements by employing a number of nominally identical voltage amplifiers with negligible equivalent input current noise. It is demonstrated in particular that, if $N (N > 2)$ voltage amplifiers are connected to the device under test and if the properties of cross-correlation among all $N$ acquisition channels connected to the output of each amplifier are exploited, the time required for obtaining a given accuracy is reduced by a factor $N(N - 1)/2$ with respect to the conventional setup for cross-correlation that employs only two channels. From another point of view, the effective background noise is reduced for constant measurement time. Such a factor can be further increased if amplifier paralleling is also employed for reducing the equivalent input voltage noise for each channel. Measurements on two different setups employing up to four channels and up to eight channels are presented that confirm the expected reduction factors in measurement times.
收起
摘要 :
The variation of the radio noise level in indoor locations has been analyzed in this communication. Three measurements campaigns have been carried out in 2008, 2010, and 2012, in the medium wave band below 2 MHz. The trials are lo...
展开
The variation of the radio noise level in indoor locations has been analyzed in this communication. Three measurements campaigns have been carried out in 2008, 2010, and 2012, in the medium wave band below 2 MHz. The trials are long-term measurements at three frequency channels centered at 1359 kHz, 1720 kHz and 1910 kHz. Five locations sited in buildings in the area of Bilbao, in the north of Spain have been studied. The noise level variations over a five year period are analyzed and compared with the ones predicted by ITU-R P.372, for outdoor locations in city environments. As a result, updated indoor noise levels are given for planning radio systems in MW band.
收起
摘要 :
A new method for determining the single-sideband noise figure of a device from double-sideband measurements is proposed which eliminates the need for tunable filters and hence greatly reduces the complexity and cost of performing ...
展开
A new method for determining the single-sideband noise figure of a device from double-sideband measurements is proposed which eliminates the need for tunable filters and hence greatly reduces the complexity and cost of performing accurate noise figure measurements. This paper compares results obtained to those obtained using a traditional single-sideband measurement system with a tuneable filter and provides a full error analysis of the new technique. The method also offers considerable possibilities for future use at higher (microwave) frequencies where YIG filters and image reject mixers are not readily available.
收起
原文获取