Transmission system for the transmission of binary data symbols

Claim 1

In a communication system for transmitting a bi-phase modulated signal between a transmitter and a receiver, such bi-phase signal being derived from a binary data signal having a symbol interval of T seconds which modulates first and second carrier waves each of a frequency 1/T, the first and second carrier waves being phase shifted 180° with respect to each other; the improvement characterized in that the receiver of such communication system comprises apparatus for improving the signal-to-noise ratio of the received bi-phase signals with respect to noise having a power spectrum density N(w) which increases with increasing frequency, such apparatus comprising: means for filtering the bi-phase signals received at said receiver, such filtering means having a sinusoidal frequency transfer function H(w) which approximates zero in response to bi-phase signal frequencies exceeding 1/T and which produces a predominantly three-level output signal in response to bi-phase signal frequencies which do not exceed 1/T; and means connected to said filtering means for converting the three-level output signal produced thereby into a binary data signal corresponding to said modulating binary data signal.