Negative frequency communication
Spectrum is the most valuable resource in communication system, but unfortunately, so far, a half of the spectrum has been wasted. In this paper, we will see that the negative frequency not only has a physical meaning but also can be used in communication. In fact, the complete description of a frequency signal is a rotating complex-frequency signal, in a complete description, positive and negative frequency signals are two distinguishable and independent frequency signals, they can carry different information. But the current carrier modulation and demodulation do not distinguish positive and negative frequencies, so half of the spectrum resources and signal energy are wasted. The complex-carrier modulation and demodulation, proposed by this paper, use the complex-frequency signal as a carrier signal, the negative and positive frequency can carry different information, so the spectrum resources are fully used, the signal energy carried by complex-carrier modulation is focused on a certain band, so the signal energy will not be lost by the complex-carrier demodulation.