Patent ID: 7027505

Claim:
A method for communicating information on a frequency modulated carrier frequency via a communication channel connecting a transmitter on a transmitting side and a receiver on a receiving side, involving frequency modulation with a modulation index M that is not greater than 0.2 to thus compress a bandwidth of the frequency-modulated carrier signal to have a small or very small frequency deviation and two sidebands at the output of the modulator of the transmitter, the method comprising: frequency modulating a carrier frequency with a modulation index M that is not greater than 0.2 to compress a bandwidth of the frequency-modulated signal to form a narrow band or very narrow band frequency-modulated carrier signal having a small or very small carrier frequency deviation at the transmitting side of a narrow or very narrow band communication channel and in said communication channel; filtering the narrow band or very narrow band frequency-modulated carrier signal to remove upper and lower sidebands of the narrow band or very narrow band frequency-modulated information carrier signal; transmitting, via the communication channel, said narrow band or very narrow band frequency-modulated carrier signal without the upper and lower sidebands such that the transmitted frequency-modulated carrier signal obtains a total power of said transmitter and includes only the instantaneous frequency varied about the carrier frequency; receiving the narrow band or very narrow band frequency-modulated carrier signal without any upper and lower sidebands from the communication channel at the receiving side of the communication channel; and expanding the frequency deviation of the received narrow band or very narrow band frequency-modulated carrier signal, without any upper and lower sidebands at the receiving side and outside of said communication channel so as to form an expanded-wideband-frequency deviation signal, the step of expanding for improving a signal-to-noise ratio and performed such that a bandwidth of said narrow band or very narrow band communication channel is never expanded.