Agilent Spectrum Analysis Basics - Agilent Technologies

RF designers are often concerned with the noise figure of their devices,
as this directly affects the sensitivity of receivers and other systems. Some
spectrum analyzers, such as the PSA Series and ESA-E Series models, have
optional noise figure measurement capabilities available. This option provides
control for the noise source needed to drive the input of the device under
test (DUT), as well as firmware to automate the measurement process and
display the results. Figure 8-2 shows a typical measurement result, showing
DUT noise figure (upper trace) and gain (lower trace) as a function of
frequency. For more information on noise figure measurements using a
spectrum analyzer, see Agilent Application Note 1439, Measuring Noise
Figure with a Spectrum Analyzer, literature number 5988-8571EN.
Figure 8-2. Noise figure measurement
Similarly, phase noise is a common measure of oscillator performance.
In digitally modulated communication systems, phase noise can negatively
impact bit error rates. Phase noise can also degrade the ability of Doppler
radar systems to capture the return pulses from targets. Many Agilent
spectrum analyzers, including the ESA, PSA, and 8560 Series offer optional
phase noise measurement capabilities. These options provide firmware
to control the measurement and display the phase noise as a function of
frequency offset from the carrier, as shown in Figure 8-3.
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Figure 8-3. Phase Noise measurement