Modulation Frequency – fm of Spectrum Analyzer

Chapter Modulation Frequency – fm

Guide to Spectrum and Signal Analysis
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Guide to Spectrum and Signal Analysis

  • 22 | Guide to Spectrum and Signal AnalysisIf m = 0.05 (%M = 5%), then for the same conditions the sideband level will be 0.165 mV for a carrier level of 6.6 mV. Clearly for low modulation factors the logarithmic display is better suited (Figure 25).Modulation Frequency fmAs stated earlier, for amplitude modulation the upper and lower sidebands displayed on a spectrum analyzer will be separated from the carrier by a frequency equal to the modulation frequency (Figure 26). This frequency domain display assumes that the IF bandwidth is narrow enough to resolve the spectral components of the modulated carrier. However, a common modulation test tone of 400 Hz will be difficult to measure if the analyzer has a minimum 1 kHz resolution bandwidth. More difficulties arise if the phase noise of the carrier masks low frequency modulation sidebands with small modulation factors.Figure 25Figure 26