Hi,
I am simulating the parametric acoustic array in air using the C++ code. My source is a modulated sinusoid, the code runs well but it does not record any pressure, depending on the modulation I use.
For example, if I use double side band modulation, everything is ok, but if I use quadrature amplitude modulation, no results are found in the pressure array. This is the code for generating quadrature amplitude modulation:
Sc1=A*sin(2*pi*fc*t);%Carrier Signal 1
Sc2=A*cos(2*pi*fc*t); %Carrier signal 2
%% QAM
g1=(1+mi*g); %envelope 1 DSBAM
g2= sqrt(1-(mi.^(2)*g.^(2))); %envelope 2
Sfm=(g1.*Sc1) + (g2.*Sc2);%QAM
For double side band modulation only the first term is used (g1.*Sc1). I tested both sources in a very small grid and it does work, so I don't know what happens in a bigger grid. In both cases the signal Sfm is multiplied by 5.
When I decrease to 1/5 of the amplitude of the source the problem seems to be solved (pressure is found in the array), but as I need to generate some nonlinear effects, the expected harmonics are gone, so it is not useful for me.
Do you have any idea what can be the problem?
Regards
Felipe.