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Spectrum analyzer based measurement can show the phase-noise power over many decades of frequency; e.g., 1 Hz to 10 MHz. The slope with offset frequency in various offset frequency regions can provide clues as to the source of the noise; e.g., low frequency flicker noise decreasing at 30 dB per decade (= 9 dB per octave).
Signal analyzers can perform the operations of both spectrum analyzers and vector signal analyzers.A signal analyzer can be viewed as a measurement platform, with operations such as spectrum analysis (including phase noise, power, and distortion) and vector signal analysis (including demodulation or modulation quality analysis) performed as measurement applications.
Spectrum analyzers are widely used to measure the frequency response, noise and distortion characteristics of all kinds of radio-frequency (RF) circuitry, by comparing the input and output spectra. For example, in RF mixers, spectrum analyzer is used to find the levels of third order inter-modulation products and conversion loss.
The noise current is set by the filament temperature. The current is an exponential function of filament temperature. At low frequencies, there is 1/f noise. At high frequencies, the transit time of the electron becomes an issue. Ott (1976, pp. 218–219) describes using a noise diode to measure noise factor.
For perfect reconstruction, the spectrum analyzer must preserve both the amplitude and phase of each frequency component. These two pieces of information can be represented as a 2-dimensional vector, as a complex number , or as magnitude (amplitude) and phase in polar coordinates (i.e., as a phasor ).
Although pink noise is a traditional choice for test signal, [3] Smaart is a source-independent analyzer, which means that it does not rely on a specific test signal to produce measurement data. Pink noise is still in common usage because its energy distribution allows for quick measurement acquisition, but music or another broadband test ...
S v is directly observable on a spectrum analyzer, whereas S φ is only observable if the signal is first passed through a phase detector. Another measure of oscillator noise is L, which is simply S v normalized to the power in the fundamental. As t → ∞ the phase of the oscillator drifts without bound, and so S φ (Δf) → ∞ as Δf → 0 ...
In the simplest case of white noise, even if the root mean square of noise is 10 3 times as large as the signal to be recovered, if the bandwidth of the measurement instrument can be reduced by a factor much greater than 10 6 around the signal frequency, then the equipment can be relatively insensitive to the noise. In a typical 100 MHz ...