DSBAM Simulation output does not use the input parameters specified

Hi,

Students are using carrier frequencies around 4000Hz and Message frequencies around 100Hz. Most students see expected outcomes. In a small number of cases, the spectrum outputs are showing carriers around 17000Hz and Message frequencies around 500Hz but teh input values are correct. See attached simulink file

Answer 1

[Vinay]

Hi @R Mc Mahon,

The 'Spectrum Analyzer' is detecting different frequencies due to a sample time mismatch between the input and the analyzer itself. To synchronize the sample time,

• Set the 'Sample Rate' parameter in the scope section to 'Inherited.'
• Additionally, in the estimation tab, select 'Frequency Span' as 'Full.'

This configuration ensures that the sampling time is in sync, allowing the Spectrum Analyzer to accurately display the input frequency of both the carrier and the modulated message at the output.

Kindly refer to the below documentation of 'Spectrum analyzer' for more details

https://www.mathworks.com/help/releases/R2023b/dsp/ref/spectrumanalyzerblock.html

I hope this helps!