View Type
There are seven types of views in the Spectrum Analyzer:
- Amplitude Spectrum (AMS)
- Phase Spectrum (PHS)
- Auto-Correlation Function (ACF)
- Cross-Correlation Function (CCF)
- Coherence Function (CHF)
- Gain and Phase (G&P)
- Impulse Response (IPR)
For Gain and Phase (also called frequency response, or bode plot) and Impulse Response measurement, Channel B must be fed with the stimulus sent to the Device Under Test (DUT) and Channel A must be fed with the response from the DUT. To achieve good measurement accuracy, significant stimulus energy must be present in the frequency range of interest. Two common signals used are the chirp signal (swept sine) and the white noise signal.
The following figure illustrates the amplitude spectrum of a 1 kHz square wave with X axis in logarithmic scale and Y axis in dBV scale.
The following figure illustrates the 1/6 octave amplitude spectrum in dBV of a 10-ms pop song captured via a laptop microphone.
The following figure illustrates the phase spectrum of two 1 kHz square waves with a phase difference of 90 degrees. The cursor reader in the phase spectrum indicates a 90-degreee difference around 1 kHz.
The following figure illustrates the auto correlation function of a 1 kHz sine wave. It shows that the time interval between correlation function peaks is 1 ms, which is equal to the period of the signal.
The following figure illustrates the cross correlation function of two 1 kHz sine wave signals, with the one in Channel A being 90 degrees ahead of the one in Channel B in phase. It shows that the cross correlation function peak is at 0.25 ms, which means that the signal in Channel A is 0.25 ms (i.e. 1/4 period) ahead of the signal in Channel B.
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