Minimization of detection of symbol-rate spectral lines by delay and multiply receivers

The detectability of the symbol rate of a digitally modulated signal by a delay and multiply receiver is investigated. Two signal pulse types are considered: Nyquist pulses and rectangular pulses. Since many digital transmission systems use rectangular pulse shapes, symbol rate-line detectability is considered for receivers optimized for rectangular pulses. For a receiver configuration that is reasonable for rectangular pulses, it is found that with a Nyquist pulse parameter alpha =0.25, the rate-line signal-to-noise ratio is down about 20 dB from that for a rectangular pulse signal.>