Demystifying Fourier analysis
A funky thing is that you can replace the 'N' sin/cos functions used in Fourier analysis with any set of 'N' orthogonal functions (aka basis functions).  In this context, a Fourier transform is just a bunch of correlations of the function to be analysed with each basis function.  Two functions are orthogonal if their correlation is zero.<p>PCM is "Fourier analysis" with impulse functions in place of sin/cos.  CDMA replaces sin/cos with a set of (almost) orthogonal functions with a wide bandwidth.<p>From an information perspective, orthogonality of the basis functions means each component/coefficient is giving you new information about the signal.  In real life you can only compute a finite number of coefficients, meaning you must have a finite amount of information, so there is an inherent uncertainty in the relationship between the signal being analysed and the output of Fourier analysis.  (Physical quantities that have an uncertainty principle, such as position and momentum, are related to each other by a Fourier transform.)