Method and arrangement for synchronizing a receiver in digital transmission systems

In a circuit arrangement for synchronizing a receiver in a digital transmission system with transmission of a special preamble selected in such a manner that the received signal has a cosine shape with a pattern frequency fp from which an associated clock pulse frequency results, which arrangement includes means for estimating at least one of the frequency and phase of the carrier and clock pulse signal components, the improvement comprising, at the receiver:

• two conjugated, complex bandpass filters (hp, hn) which are fed by the received signal rd(i) and which furnish complex output signals gp(i) and gn(i) corresponding to the respective positive and negative spectral lines of the received signal;
• a circuit connected to said filters for forming sequences of the phase values .phi.p(i) and .phi.n(i) from said output signals, where i is the position of each phase value in the sequence;
• a respective delay member and difference forming member connected to said circuit for forming the differences between every pair of successive phase values .phi.p(i) - .phi.p(i-1) or .phi.n(i) - .phi.n(i-1);
• means connected for subtracting the constant component 2.pi.fp0.multidot.T or -2.pi.fp0.multidot.T, respectively, from each difference, with the sampling rate being 1/T, to form difference values .phi.pd(i), .phi.nd(i);
• means connected for reducing the difference values to a range from -.pi. to +.pi.;
• and
• weighting and sum and difference forming means connected for producing signal parameter values according to the following equations:
• ##EQU13## where i=the running number of the N sampling moments at a spacing T,
• I=(N-1)/2, and
• fp0=a known pattern frequency.

In a method for synchronizing a receiver in a digital transmission system which transmits to the receiver a signal containing a base band signal component, a clock pulse signal component and a special preamble selected in such a manner that the received signal has a cosine shape with a pattern frequency fp from which an associated clock pulse frequency results, which method includes estimating at least one of the frequency and phase of the clock pulse signal component, the improvement comprising, at the receiver:

• obtaining representations of the individual positive (gp) and negative (gn) spectral lines of the received signal by filtering;
• determining the respective frequencies fgp and fgn associated with these spectral lines and the respective phases gp and gn associated with these spectral lines by linear regression;
• and subjecting the determined frequency and phase values to subsequent difference and the sum formation, to obtain the following estimated values:
• ##EQU14##