frequency modulation by bessel

Can somebody help me this question?

[Walter Roberson]

Given a signal how do you find the side signals and the amplitudes of those?

Answer 1

[Saarthak Gupta]

Hi Huijia,

I understand that you want to calculate the amplitude of the first two side frequencies of a signal, given its modulation index (beta).

For a sinusoidal baseband signal with frequency fm, the transmitted signal, y(t), can be represented as:

The modulation index is defined as:

The resulting frequency spectrum is a set of cosines weighted by Bessel functions of β.

where k is the sideband number.

The first two sidebands will occur at k = 1 and -1, and the amplitude of both sidebands will be J1(β).

You can use the “besselj” function in MATLAB to calculate the same:

besselj(1,modIdx)

Please refer to the following MATLAB documentation for further reference:

• https://www.mathworks.com/help/matlab/ref/besselj.html

Hope this helps!

Best regards,

Saarthak