Abstract: The baud rate of a digital signal is estimated using a method based on a mean squared error determination. The disclosed method fits a sine wave curve to the digital signal and varies its frequency until the mean squared error is a minimum, wherein the error is defined as the distance of the sine wave curve from its center line at each transition of the digital signal. The disclosure includes an apparatus for carrying out the method of the invention. In addition, the method is suitable for execution as a stored program within a high-speed signal processor.

Abstract: A receiver for burst transmission of MSK-modulated binary signals includes in-phase (I) and quadrature (Q) demodulation under the control of reference sine and cosine signals. Initially, the reference signals are near the nominal carrier frequency of the received signal, but at arbitrary phase, so that noncoherent detection takes place. A control circuit is provided to slew the reference signals to the same phase as the MSK carrier for low-noise coherent detection. Because of the burst nature of the communications, data throughput is significantly reduced if reference phase acquisition time is large. In order to reduce the phase acquisition slew time, each burst of data is preceded by a predetermined preamble. In the receiver, the noncoherently detected preamble is applied to a set of four preamble-matched correlators which respond to the I and Q portions of the preamble, and to the cross-coupled Q and I portions contaminating the I and Q portions respectively.