How to generate FM signal in Orcad capture

FM signal generation is required in many circuit design analysis. Instead of creating circuit level FM generator for example using BJT or FET transistor, one often requires just the FM signal to fed into the desired designed system. FM signal in orcad capture can be generated in many ways. One of the simple way is the use the VSFFM part which can be found under the source library.

 The circuit for FM wave using the VSFFM FM generator is shown below:

 In this VSFMM source, we can specify the modulating signal amplitude, the frequency of the modulating signal, the frequency of the carrier signal and the frequency modulation index. In this simple example the magnitude of modulating signal is VAMP=1V, modulating signal frequency, FM=1.5kHz, carrier signal frequency, FC=10kHz.

To check the Frequency modulated wave, we simulate and get the output as shown in the figure below:

To view the FM signal spectrum, we just click the FFT ion on the probe display in the Orcad capture. This gives us the following FM signal spectrum:

The spectrum clearly shows the absence of carrier part at the 10kHz.

Finally, the power developed on the resistor due to the FM signal is shown below:

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