Chirp-baseband vs passband

The MATLAB built-in function chirp generates a swept-frequency cosine signal, where the frequency sweep is based on the type of sweep ordered in the chirp command (linear, quadratic, logarithmic, etc). The output is essentially a passband modulated signal. What if I want to see the chirp in baseband? How do I demodulate the output of the chirp command and see the time domain baseband representation?

If I could know what is the carrier frequency being used in the MTATLAB built-in function which is being swept as a chirp between f0 and f1, I could demodulate the output and view the time domain chirp as a baseband signal?