I want to simulate multi-path fading channels in Matlab with doppler. But to my surprise, I found that Doppler introduces an AM modulation in the signal.
I used the rayleighchan and ricianchan for mimicing the multi-path effects but both give the same AM modulation of the signal with the sinusoid of the frequency fd which is parameter in the ricianchan and rayleighchan.
Kindly let me know that
i) Does Doppler effect change the amplitude?
ii) If yes how to cope with that.
Mathematically, Doppler's Effect is independent of Amplitude.
As amplitude represent intensity, so in some cases Doppler's shift may effect Amplitude.
Hoping this explanation to be useful to some extent
Basic doppler effect involves a time-variant phase shift and no amplitude variation.
But the said fading generator (I don't know the specific MATLAB implementation) superimposes multiple channels.
When I simulate the channel with zero Doppler I do not get a Sinusoidal component in the waveform but as I insert some Doppler then I get significant sinusoidal component in the waveform.
So Doppler is changing the amplitude in this case.
To me it is due to change in channel and different multipath components when arrive with different and time varying phase, we get a change in amplitude.