Phase Noise Measurement in Crystal Oscillators - Q-Tech Corporation

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Phase Noise Measurement in Crystal Oscillators APPLICATION NOTES QTAN‐107

AGILENT E5052A Signal Source Analyzer Application Notes The E5052A employs a proprietary cross-correlation measurement method, using measurement channels with independent reference sources and performing analysis on the two-channel signals. If the two signals are correlated and vector summed, the vector (amplitude and phase) of the two signals will be emphasized. Crosscorrelation can remove the limitation imposed by the noise floor of a reference source, allowing measurements of extremely low noise levels. The E5052A performs from 1 to 10,000 correlations to lower the noise floor. The phase noise sensitivity improves with the number of correlations. For example 10 correlations yield a 5-dB improvement in the noise floor improvement, while 10,000 correlations provide a 20-dB improvement in the noise floor. However, the larger the number of correlations required longer test time. Currently, Q-Tech used 16 correlations in test. The best noise sensitivity the E5052A can provide is -178dBc/Hz. This “Golden unit OCXO 10MHz measured on E5052A was used in set-up verifications. ERC 10MHz OCVXO in Agilent E5052

Date tested: 7/25/2007

-6.00E+01

-7.00E+01

-8.00E+01

-9.00E+01

L(f), dBc

-1.00E+02

-1.10E+02

-1.20E+02

-1.30E+02

-1.40E+02

-1.50E+02

-1.60E+02

-1.70E+02 1

10

Phase Noise (dBc/Hz) S/N 71

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100

Frequency Offset, HZ

1000

10000

Phase Noise (dBc/Hz) S/N 70 VCXO at Vc=3.8v

100000

QT625LDM-128MHz Phase Noise

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QT625LEE-40MHz Phase Noise

QT625LAE-16MHz Phase Noise

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QT625CE2E-12MHz Phase Noise    

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