The Power Spectrum Measurement - HP 3563A Operating Manual

Using The Linear Resolution Mode
Selecting a Measurement and Display

The Power Spectrum Measurement

The power spectrum measurement shows tbe input signal in the frequency domain. It is computed
by multiplying the FFT of tbe signal by its complex conjugate:
Gxx= FxFx*
where:
Fx Is the channel's linear spectrum
Fx. is its complex conjugate
This measurement is provided in addition to the frequency response measurement because the
single-channel power spectrum is faster than the dual-channel frequency response measurement.
Single-channel measurements also provide greater maximum real-time bandwidth (with fast
averaging activated: 10 kHz for single-channel; 5 kHz for dual-channel). The power spectrum
provides no phase information.
To select tbe power spectrum measurement, press S E LECT MEAS, followed by the
POWER SPEC softkey (see figure 3-7).
To select a measurement display for tbe power spectrum measurement, press MEAS DISP (see
figure 3-8). Notice that a number of different measurement displays are available for this
measurement, such as:
POWER
SPECl
POWER
SPEC2
AUTO
MATH
FILTRD
INPUT
3-42
Displays the power spectrum measured on Channel 1 . This softkey
appears only when Channel 1 is active.
Displays the power spectrum measured on Channel 2. This softkey
appears only when Channel 2 is active.
Displays the trace calculated with the auto math table; see "Math &
Auto Math" in chapter 15. Note that this softkey label might be
replaced by a user-defined label.
Displays the filtered input menu, which provides time record and linear
spectrum displays for each active input channel; see "Filtered-Input
Displays" later in this chapter.