Method and apparatus for frequency tracking in a space time transmit diversity receiver

An apparatus having a frequency discriminator for obtaining a frequency error estimate of the difference between a reference frequency and the frequency of a space time transmit diversity signal from first and second received sequences transmitted respectively by first and second antennae, and received by a receiving antenna, where each sequence has two sets of first and second intervals, of equal length, such that the contents of the second interval of the second received sequence are the additive inverse of the contents of the first interval of the second received sequence, the frequency discriminator comprising:

• a memory, operatively attached to the receiving antenna for storing the contents of the first and second sequences;
• interval defining means, operatively attached to the memory to receive the first and second sequences of symbols, for dividing the received sequences into sets of first and second intervals;
• partial sum adding means, operatively attached to the interval defining means to receive the contents of first and second sequences during the two sets of first and second intervals, for calculating two sets of first and second partial sums as the sum of the contents of the first and second intervals respectively for each set;
• total sum adding means, operatively attached to the partial sum adding means to receive the two sets of first and second partial sums, the total sum adding means for calculating total sum functions for the first and second sets representing the sum of the first and second partial sums for each set;
• conjugation means, operatively attached to the total sum adding means to receive the total sum of the second set of partial sums, for calculating the conjugate of the total sum;
• multiplier means, operatively attached to the conjugation means and total sum adding means to receive the total sum functions and the conjugate of the received total sum for multiplying the received total sum functions and the conjugate of the received total sum thereby providing a correlation function;
• and
• a frequency error estimator, operatively attached to the multiplier means to receive the correlation function, for extracting the frequency error from the correlation function.