Table of Contents
Advertisement
Figure 14 RF sideband spectrum
Phase terms
There are two types of fluctuating phase terms:
• spurious signals
• phase noise
Spurious signals
The first are discrete signals appearing as distinct components in the spectral
density plot. These signals, commonly called spurious, can be related to known
phenomena in the signal source such as power line frequency, vibration
frequencies, or mixer products.
Phase noise
The second type of phase instability is random in nature, and is commonly
called phase noise. The sources of random sideband noise in an oscillator
include thermal noise, shot noise, and flicker noise.
Many terms exist to quantify the characteristic randomness of phase noise.
Essentially, all methods measure the frequency or phase deviation of the
source under test in the frequency or time domain. Since frequency and phase
are related to each other, all of these terms are also related.
Spectral density One fundamental description of phase instability or phase
noise is spectral density of phase fluctuations on a per-Hertz basis. The term
spectral density describes the energy distribution as a continuous function,
expressed in units of variance per unit bandwidth. Thus
page 50) may be considered as:
Agilent E5505A User's Guide
e5505a_user_RF_sideband.ai
rev2 10/20/03
3
Phase Noise Basics
S φ f ( )
(Figure 15
on
49
Advertisement
Table of Contents
