hello
yes this is the general scientific definition of a chirp signal
In signal processing applications, most of the time you only need the real part of the signal , so it would become
y(t) = a(t)*cos(phi(t) + phi0) , phi is the angle at time t , and a the amplitude vs t (can also vary), phi0 the initial angle value.
matlab chirp function simply allows you to use some typical frequency profiles (linear, quadratic, log, etc...) - read the doc !
but you can also built your own function, simply create phi vs t and you are done
see home made examples attached !
