Abstract: An improved Nyquist filter can be used as a matched filter in a digital communications system. This filter is characterized in that the frequency domain response meets the Nyquist criteria and that the square root of the frequency domain response has a first derivative that is continuous at all points. In other embodiments, the square root of the frequency domain response continuous over all points for all higher order derivatives.

Abstract: A system and method for information content-independent synchronization with a received signal. A variable of the signal (e.g., average energy or magnitude) which is related to the energy distribution, is measured over a period of time. The signal's information bearing point is found at the point within the information period of the signal with the highest averaged energy. The point may be found, for example, by detecting the sample point with highest average energy, or by correlating multiple sample points to a stored template. Interpolation may be performed to locate an information bearing point that is between sample points. Because the relative energy content of the signal is effectively independent of the specific information content, synchronization with the information bearing point is accomplished without requiring the insertion of any special information content or fixed content patterns into the signal.