I'm seeking a novel and new means for encoding information within a wave medium; perhaps something exploiting pulse modulation or polarization. Comments? Thoughts?
AM and FM are time and frequency-modulated respectively, of radio signsls. If you look at any other form of energy, such as optics, copper, even just rolling marbles down a hill, you'll see the same separation.<p>Are you wanting something that might be done by today's spies, today's clever children or clever children in 10-20 years?
There is a lot of other modulation techniques... start by understanding them. You can start with Wikipedia, follow the links in the sidebar. <a href="http://en.wikipedia.org/wiki/Amplitude_modulation" rel="nofollow">http://en.wikipedia.org/wiki/Amplitude_modulation</a><p>Analog modulation:
AM /
FM /
PM /
QAM /
SM /
SSB<p>Digital modulation:
ASK /
APSK /
CPM /
FSK /
MFSK /
MSK /
OOK /
PPM /
PSK /
QAM /
SC-FDE /
TCM<p>Spread spectrum:
CSS
DSSS
FHSS
THSS<p>See also:
Capacity-approaching codes /
Demodulation /
Line coding /
Modem /
PAM /
PCM /
PWM<p>There are limits to how much information can be transmitted on a channel with a given signal/noise ratio. <a href="http://en.wikipedia.org/wiki/Shannon_limit" rel="nofollow">http://en.wikipedia.org/wiki/Shannon_limit</a>