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Applying Free Space Path Loss to a Signal

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Jan Wlodarczyk
Jan Wlodarczyk on 11 Jan 2021
I apologise if this question is trivial.
I am trying to apply free space path loss to my modulated signal "signal_tx_in". I am using the communications toolbox for this, and decided to use the fspl function.
Now I am confused as to how to correctly apply this loss to the signal. I am aware that fspl returns a positive value in dB and that the signal is a vector containing complex numbers, however is there any way to perform this operation without writing a function that scales these numbers? I can imagine either scaling the complex numbers by the loss or using the RicianChannel in the communications toolbox to apply this loss in the "average path gains" field. Any help will be much appreciated!
% FREE SPACE PATH LOSS
global FREQ;
lambda = physconst('LightSpeed')/FREQ;
signal_loss_fsp = signal_tx_in 'WHAT SHOULD I PUT HERE?' fspl(L,lambda);

Answers (1)

Chaitanya Mallela
Chaitanya Mallela on 2 Feb 2021
If signal_loss_fsp is a voltage signal you can use
signal_loss_fsp = signal_tx_in * 10^(-fspl(L,lambda)/20);
as signal loss is always a negative of path loss in dB scale.

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