Full duplex frequency division multiplex communication system

A duplex frequency division multiplex communication system comprising:

• a plurality of user stations intercoupled by a common communication channel, a first frequency converting means coupled to said common channel for shifting the carrier frequencies of the signals introduced to the common channel by all of the user stations by a particular frequency differential for reception by the user stations, each of said stations comprising a transceiver and each transceiver comprising:
• a source of information signals;
• modulating means coupled to said source for modulating said information signals on a first carrier of a particular frequency;
• second frequency converting means;
• first means for applying the first modulated carrier from said modulating means to said second frequency converting means to shift the first carrier to a selected channel frequency;
• second means coupled to said second frequency converting means for introducing the output from said second frequency converting means to said common channel;
• third frequency converting means;
• third means for introducing signals from said common channel modulated on a second carrier of a particular channel frequency to said third frequency converting means, said second carrier having a frequency displaced from the frequency of said first carrier by said particular frequency differential;
• demodulating means;
• fourth means for applying output signals from said third frequency converting means to said demodulating means to recover the signals modulated on the second carrier;
• and information reproducing means coupled to said demodulator means.