Method of digital signal's spectrum coding in the analog channels

On the basis of summarizing the superiority and inferiority of the current digital communication systems, this paper provides a spectrum-coding method adaptive to narrow-band radio communication to transmit digital signal. This method codes the spectrum with the binary digital signal to be transmitted, then convert the spectrum to an ordinary analog signal by the IFFT and transmits it. At the receiving end, the received analog signal is sampled and transformed to the original coded spectrum by the FFT, so that the digital signal of the transmission end is distinguished. Three basic linear-phase spectrum-coding methods are presented, and their performance-comparison are discussed in detail.