Carrier recovery scheme for a SSB-SC signal

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.degree., 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.sup.2 (t) sin .phi., where f(t) is the low-pass filtered waveform of the baseband data signal and .phi. is the difference in phase between said carrier of said received signal and the carrier generated by said local carrier generating means.