looks like a square wave modulated by an decaying exponential envelope
fine tune the parameters to your own needs :
tau = 0.1; % exp decay rate
freq = 0.25; % square wave frequency
amp = 2000; % amplitude
Fs = 1e2; % sampling rate (>> at least 2*freq)
samples = 3000;
dt = 1/Fs;
t = (0:samples-1)*dt;
x = -amp*exp(-tau*t).*sign(cos(2*pi*freq*t)); % or use square function instead of sign(cos) if you have the signal processing tbx
plot(t,x)
