Communication system employing spectrum folding

Claim 1

In a communication system including a transmitter, a receiver, and a wavepath connecting said transmitter to said receiver: means for transmitting and receiving an input siGnal having a frequency spectrum f1-f3 which only partially overlaps the passband f2-f4 of said system, and which is less than said passband; said means comprising at said transmitter: a bandsplitter for dividing said signal into two subbands f1f''2 and f''2-f3, where the first of said subbands includes that portion of the signal spectrum that falls outside said passband, and where the second of said subbands falls wholly within said passband; a frequency translator for shifting the frequencies of said first subband to a region f''3-f''4 of said passband not occupied by said second subband; and a multiplexer for combining said second subband f''2-f3 and said frequency-shifted first subband f''3-f''4 for transmission along said wavepath; and where said means comprises at said receiver: a demultiplexer for separating said second subband f''2-f3 and said frequency-shifted first subband f''3-f''4; a second frequency translator for shifting the frequencies of said frequency-shifted subband f''3-f''4 back to f1-f''2; and means for recombining said first and said second subbands f1-f''2 and f''2-f3 to reform said input signal spectrum f1-f3.