Design Considerations in State-of-the-Art Signal Processing and Phase Noise Measurement Systems

Walls, F.L.; Stein, S. R.; Gray, James E.; Glaze, D. J.

doi:10.1109/freq.1976.201325

Cited by 62 publications

(16 citation statements)

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“…where, the Fourier transforms of (5) we see that the source noise is present equally and in same phase at the output ports 2 and 3 in contrast to the thermal noise of the resistor R 23 which appears 180 0 out of phase between outputs 2 and 3. The same effect occurs for the 100  isolation resistor used in the CWPS.…”

Section: A Theorymentioning

confidence: 87%

Cross-spectrum measurement of thermal-noise limited oscillators

Hati

Nelson

Howe

2016

Review of Scientific Instruments

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Abstract:Cross-spectrum analysis is a commonly-used technique for the detection of phase and amplitude noise of a signal in the presence of interfering noise. It extracts the desired correlated noise from two time series in the presence of uncorrelated interfering noise. Recently, we demonstrated that the phase-inversion (anti-correlation) effect due to AM noise leakage can cause complete or partial collapse of the cross-spectral function [1], [2]. In this paper, we discuss the newly discovered effect of anti-correlated thermal noise that originates from the common-mode power divider (splitter), an essential component in a cross-spectrum noise measurement system. We studied this effect for different power splitters and discuss its influence on the measurement of thermal-noise limited oscillators. An oscillator whose thermal noise is primarily set by the 50  source resistance is referred to as a thermally-limited oscillator. We provide theory, simulation and experimental results. In addition, we expand this study to reveal how the presence of ferrite-isolators and amplifiers at the output ports of the power splitters can affect the oscillator noise measurements. Finally, we discuss a possible solution to overcome this problem.

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Section: A Theorymentioning

confidence: 87%

Cross-spectrum measurement of thermal-noise limited oscillators

Hati

Nelson

Howe

2016

Review of Scientific Instruments

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“…A theoretical explanation for the above result is still under development. Anyway, our results should be compared to those reported in [11], where another correlation-based NMS is described, showing an exceptionally low noise floor, of the order of 200 dB rad /Hz at MHz. That scheme is different from ours, mainly because of the absence of the carrier suppression mechanism and because the mixers are used as phase-to-voltage converters, saturated at both inputs.…”

Section: Discussion Of the Results And Conclusionmentioning

confidence: 99%

“…That scheme is different from ours, mainly because of the absence of the carrier suppression mechanism and because the mixers are used as phase-to-voltage converters, saturated at both inputs. Although only a brief system description is given in [11], and the presence of thermal noise sources common to the two arms due to the power splitter internal resistors is not mentioned, the reported noise floor is some 10 dB lower than . To conclude, the double interferometer allows noise measurements with a lower instrument noise floor as compared to single interferometer systems.…”

Section: Discussion Of the Results And Conclusionmentioning

confidence: 99%

“…In fact, it has been demonstrated that for the X-band a PM noise measurement system (NMS), based on this method, shows a sensitivity close to 190 dB rad /Hz (white noise) if a power level as high as 20 dBm can be tolerated [2]. Besides, it is known that the sensitivity of the saturated-mixer NMS can be improved by some 15 dB by means of correlation of the output of two equal NMS's that measure the same device [3], [11]. So, in search of the most sensitive instrument we combined the two techniques, correlating the output of two interferometers measuring the same DUT (device under test).…”

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confidence: 99%

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Improved interferometric method to measure near-carrier AM and PM noise

Rubiola

Giordano²,

Groslambert³

1999

IEEE Trans. Instrum. Meas.

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Abstract-An improved version of the interferometric method to measure near-carrier AM and PM noise is being presented. The main feature of this scheme is the capability to reduce the instrument noise by correlating the output of two equal interferometers built around the same device to be tested, thus enhancing the sensitivity. Two double interferometers are described, operating in the microwave and VHF bands. The latter shows a noise floor of 0194 dB rad 2 /Hz when the signal power is +8 dBm. The sensitivity of both the instruments turns out to be significantly higher than the ratio of the thermal noise divided by the carrier power.

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“…The DUT noise is extracted after rejecting the background noise of the instrument, assuming that the two channels are statistically independent. After the seminal paper [1], and the early application shown in [2], this choice is adopted by virtually all manufacturers ( Table 1). The dual channel scheme comes in two flavors, with one or two reference oscillators.…”

Section: Introductionmentioning

confidence: 99%

Artifacts and errors in cross-spectrum phase noise measurements

Gruson

Rus²,

Rohde

et al. 2020

Metrologia

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This article is intended to give a warning about: (i) the internal processing inside the phase-noise analyzers, (ii) the oscillators whose white phase noise floor seems too low, chiefly the 100-MHz OCXOs, and (iii) the need to introduce in the domain of phase-noise measurements the basic concepts of uncertainty found in the International Vocabulary of Metrology (VIM).The measurement of low-noise quartz oscillators, or of other lownoise oscillators exhibiting a noise floor of the order of −180 dBc/Hz or less, relies on the cross-spectrum method. The measurement may take long time, from hours to 1-2 days, for the number of averaged cross spectra to be sufficient to reject the background of the noise analyzer. That said, something anomalous is often seen in a region approximately one decade wide, located where higher-slope noise joins the white floor or the 1/f noise. The plot may be quite thick and irregular, and a dip may appear, where the phase noise looks lower than the white noise floor. Such anomalies reveal something worse. The white region of the PM noise spectrum may be affected by gross errors and, in the not-so-rare worst case, is a total nonsense. We address the problem trough a simple experiment, where we insert a dissipative attenuator between the oscillator and the PN analyzer. Surprisingly, in some cases the attenuation results in a lower noise floor. Such erratic behavior is reproducible, having been observed separately in three labs with instruments from the two major brands. We provide the experimental evidence, the full theory, and suggestions to mitigate the problem.

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Design Considerations in State-of-the-Art Signal Processing and Phase Noise Measurement Systems

Cited by 62 publications

References 0 publications

Cross-spectrum measurement of thermal-noise limited oscillators

Cross-spectrum measurement of thermal-noise limited oscillators

Improved interferometric method to measure near-carrier AM and PM noise

Artifacts and errors in cross-spectrum phase noise measurements

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