Add noise to multi-signals

I want to simulate a received signal which has three sins-wave signals at different frequencies with difference amplitudes and phases, say: (f(i), a(i), p(i)), i=1,2,3. The receiver has certain noise. The Rx noise compares with the received signal powers, we have SNR(i).

How do I model this signal in time-domain?

[KALYAN ACHARJYA]

%Here Sine signals, what you are expecting next?

Answer 1

[KALYAN ACHARJYA]

%Change the paramerts as per requirements

    t=0:.01:13;
    noiseAmplitude=randi(5);
    noise=noiseAmplitude* rand(1, length(t));
    w1=3;w2=4;w3=5;
    amp=6;
    phase=30;
    y1=amp*sin(w1*t+phase)+ noise;
    plot(y1,'r','linewidth',1.5);
    hold on;
    y2=1.3*amp*sin(w2*t+phase+10)+noise;
    plot(y2,'linewidth',1.5);
    y3=1.5*amp*sin(w3*t+phase+20)+noise;
    plot(y3,'g','linewidth',1.5);
    hold off;

[Chen]

Many thanks Kalyan for your example, can you let me know how can add the noise to each signal with specific SNRs, for example, in your example, we assume SNR for three signal are 10, -5, -15 dB, respectively. Cheers chen

[KALYAN ACHARJYA]

For that you have to use some fixed value, I have used the random value

rand(1, length(t))

• Just assign data (Not random)
• find the SNR of the signal
• Do the back calculation, how much data assign required to find the required SNR

I have answered it as per question at the heading.