Say I have a QPSK signal transmitted at a carrier frequency of 5 MHz. The message rate is 100 kHz. If I use a Tektronix scope or data acquisition box to digitize and capture the signal (not a direct conversion to baseband) I get a "real" time series correct?
Now if I want to use this time series in Matlab to demodulate and learn about quadrature modulation and demodulation, do I need to convert each of the samples to I and Q? How do I do that? Multiply by sin and cos? I like to learn through examples, so if you an provide that, it would be much appreciated.