| 摘要 |
<p>Adaptive antennas are used to counter dispersion due to multipath propagation and interference from other stations using the same frequency. Each of the antennas in the array has a respective tapped delay line in which the tap output signals are weighted and summed. In a known theoretical proposal, the weights W are determined as follows: <MATH> where Rxx is the autocorrelation matrix of the input to the system and rxd is the crosscorrelation vector of the input signal and the known sequence. In practice estimates of Rxx and rxd may be obtained by averaging the instantaneous matrices and vectors over the training sequence. A method to provide an improved estimate of Rxx is disclosed in which the estimate of Rxx is refined by calculating a new estimate <MATH> where beta is a scalar value and I is the identity matrix, and wherein successive iterations are evaluated by: comparing the real part of the summed tap output signals with a set level; ascribing a symbol value of logical zero to those summed tap output signals which fall to one side of the set level and ascribing a symbol value of logical one to those summed tap output signals which fall to the other side of the set level; calculating the mean of the levels of those signals ascribed the value logical zero and the mean of the levels of those signals ascribed the value logical one; calculating the distance between the level of each signal ascribed the value logical zero and the respective mean, and the level of each signal ascribed the value logical one and the respective mean; calculating the sum of the distances from the means; calculating the distances of the levels of all signals from the set level; calculating the sum of the distances of the levels of all signals from the set level; calculating the ratio of the sum of the distances from the means to the sum of the distances of the levels of all symbols from the set level. <IMAGE> <IMAGE></p> |
