Carrier recovery scheme for a SSB-SC signal

Claim 1

In a single sideband suppressed carrier system, a receiver for recovering the proper carrier phase from a received single sideband suppressed carrier signal transmitted at a predetermined baud rate, said receiver comprising: a local carrier generating means for generating an inphase estimated carrier signal having a control input, the phase of said in-phase estimated carrier signal varying with the signal level at said control input; means for shifting said in-phase estimated carrier signal 90°, so as to form a quadrature estimated carrier signal which is in phase quadrature with said in-phase estimated carrier signal; first demodulator means for modulating the signal received by the receiver with said in-phase estimated carrier signal so as to produce a first demodulated signal; second demodulator means for modulating the signal received by the receiver with said quadrature estimated carrier signal so as to produce a second demodulated signal; first and second low-pass filters connected to the outputs of said first and second demodulator means for filtering said first and second demodulator signals, respectively; estimator means, connected to the output of said first low-pass filter, for comparing said first demodulated signal with predetermined reference levels, for sampling the output of said comparison at the baud rate and for generating a sequence of estimated data symbols; and error signal generating means, connected to said control input of said local carrier generating means, for generating, responsive to said estimated data symbols, an error signal proportional to f 2 (t) sin φ, where f(t) is the low-pass filtered waveform of the baseband data signal and φ is the difference in phase between said carrier of said received signal and the carrier generated by said local carrier generating means.