A new carrier recovery method for 16-QAM signal

We propose a new carrier recovery method for the 16-level quadrature amplitude modulation (16-QAM) signal, which reduces the phase jitter of the recovered carrier. In this method, the received 16-QAM signal is processed in two paths; one path transforms the received signal into a 12-PSK signal, and the other detects the envelope of the received signal. Using an envelope detector and a window detector, we extract the time period that the 16-QAM signal causing phase jitter exists. We recover the carrier phase from the 12-PSK signal using a digital phase locked loop (PLL) which is controlled by the window detector output. By this method, the data pattern-related noise of the conventional times-four carrier recovery method is entirely eliminated. We implement an experimental model to examine the proposed method.