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WiFi Test Tips Seventeen: Spectrogram

  • Categories:WIFI Test knowledge
  • Author:itest
  • Origin:itest
  • Time of issue:2018-12-12 00:00
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WiFi Test Tips Seventeen: Spectrogram

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Figure 3 Adjacent channel interference view

Out-of-band interference: The interference caused by harmonics or spurious radiation outside the passband of receiving useful signals is called out-of-band interference.

Figure 4 Out-of-band interference view

Non-linear distortion: It is caused by the characteristics of electronic components and the nonlinearity of the curve, which causes new harmonic components in the output signal and changes the original signal spectrum


Figure 5 Non-linear distortion view

2. SpectrumMask Margins

As shown in the Spectrum Mask Margins view in Figure 6 below, F1 in the figure: F stands for Frequency, and the number 1 stands for Signal number. M1: M stands for Margin, and the number 1 stands for Signal serial number. From the center frequency to the left, the order is Lower1, Lower2...Upper1, Upper2... to the right. Different spectrum masks have different numbers of corresponding spectrum mask segments (AB, BC, CD, etc. in the figure below), so the number of Lower/Upper ranges from 2 to 4.

M1 represents the minimum value of the difference between each frequency point in each template segment of AB, BC, CD, DE, FG, GH, HI, and IJ and the actual signal spectrum in each segment. If the difference is negative, the actual signal exceeds the template (as shown in Figure 2, Figure 3, and Figure 4 above). F1 represents the frequency of the relative center frequency point in the template corresponding to the M1 point in each segment of the spectrum template.


Figure 6 Spectrum Mask Margins view

Note: RBW uses 100KHz specified in the 802.11 standard. Currently, WT20X series SPAN uses 120MHz by default
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