Signal Generation with Fixed Frequency and Frequency Deviation

Hi Experts. I want to generate a signal with fixed frequency but with delta_f < 0.25% or delta_f < 8MHz. I can generate simple signal but have no idea about frequency deviation.

Code so far.

Fs = 13 * 1.6e9; %13 for real time sampling
T = 1e-3;
F = 2e9;
t=0:1/(Fs):T-1/(Fs);
s1=sin(2*pi*F*t);

after this i will down sample it to Fs = 1.6e9. Also if T is more then 1ms it will make the MATLAB unresponsive because of too much samples.

Please guide or share a code related to the frequency deviation in fixed frequency. Thank you.