Agilent Technologies E5503A Guide de l'utilisateur télécharger pdf (Page 37)

100

101

4-4

Agilent Technologies E5500 Phase Noise Measurement System

Phase Noise Basics

What is Phase Noise?

L(f) is an indirect measurement of noise energy easily related to the RF

power spectrum observed on an RF analyzer. Figure 4-3 shows that the

National Institute Science and Technology (NIST) defines L(f) as the ratio

of the power (at an offset (

f) Hertz away from the carrier) The phase

modulation sideband is based on a per Hertz of bandwidth spectral density

and or offset frequency in one phase modulation sideband, on a per Hertz of

bandwidth spectral density and

(f) equals the Fourier frequency or offset

frequency.

= single sideband (SSB) phase noise to carrier ration (per Hertz)

Figure 4-3 Deriving

L(f) from a RF Analyzer Display

is usually presented logarithmically as a spectral density plot of the

phase modulation sidebands in the frequency domain, expressed in dB

relative to the carrier per Hz (dBc/Hz) as shown in Figure 4-4. This chapter,

except where noted otherwise, will use the logarithmic form of as

follows: .

L f

()

power density in one phase modulation sideband

()

total signal power

----------------------------------------------------------------------------------------------------------------------------------------

ssb

------------

Lf()

L f()

∆

f() 2f

L f()=

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 464 465

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Agilent Technologies E5503A Guide de l'utilisateur Page 37

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