Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Analysis of complex waves
Reexamination Certificate
2000-01-04
2001-11-06
Nguyen, Vinh P. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Analysis of complex waves
C324S601000
Reexamination Certificate
active
06313619
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an arrangement for the measurement of phase noise of a test specimen according to the preamble of the independent claim.
In phase noise measurement of signals of a test specimen using a spectrum analyzer, phase noise of mixing oscillators of the spectrum analyzer is added to phase noise of the test specimen. Test specimens, therefore, can only be correctly measured if their signal-to-noise ratios are at least 5 dB worse than for the spectrum analyzer (Ulrich Rohde, “Microwave and Wireless Synthesizers,” Chapter 2.8.2).
To avoid this disadvantage, it is known to construct two identical test specimens and to mix these in a mixer at 0 Hz (Ulrich Rohde, Chapter 2.8.5). Using this process, the actual carrier of the test specimen disappears and then only noise sidebands are measured, the phase noise of the spectrum analyzer itself not being included. A disadvantage of this known process is that two identical test specimens must be present.
To suppress a carrier it is also known to use specialized so-called notch filters, which however must be of high quality.
It is an object of this invention to provide a structurally uncomplicated arrangement with which phase noise can be measured with a spectrum analyzer even of test specimens which, compared with noise characteristics of the spectrum analyzer, have relatively good noise characteristics.
SUMMARY OF THE INVENTION
This object is met for an arrangement as set forth in the preamble of the principal claim, by the characterizing claimed features thereof. Advantageous enhancements are set forth in the dependent claims.
According to principles of this invention, a carrier of the test specimen is strongly suppressed, up to a predetermined small carrier remainder, by addition of an output signal of the test specimen to an output signal of a compensation generator, which is constructed in the manner of a tracking generator, without hereby affecting sideband noise. In this manner, a good oscillator, with respect to noise, can be precisely measured using a relatively poor spectrum analyzer. Creation of the output signal of the compensation generator is accomplished in a very uncomplicated and economical manner, as is known for so-called tracking generators. An equal-value but oppositely phased compensation signal used for suppression of the carrier does not itself contribute to phase noise; only phase noise of an additional input oscillator of the compensation generator has an effect. However, due to the low frequency, this input oscillator can be constructed with low noise without great expense.
REFERENCES:
patent: 4272719 (1981-06-01), Niki
patent: 4714873 (1987-12-01), McPherson
patent: 4780667 (1988-10-01), Reese
patent: 5059927 (1991-10-01), Cohen
Ulrich Rohde, “Microwave and Wireless Synthesizers,” Chapter 2.8.2 and Chapter 2.8.5, pp. 118-132; 1997.
Nguyen Trung Q.
Nguyen Vinh P.
Rohde & Schwarz GmbH & Co. KG
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