Wireless communication unit and method for filtering using an adaptive root raised cosine filter

摘要

A method of designing a phase-compensated digital root raised cosine filter for a receiver comprises generating (62) a baseband signal; filtering (64) the baseband signal to model an ideal transmit pulse shaped signal and splitting the ideal transmit pulse shaped signal into a first and second path. The signal on the first path is filtered with a root raised cosine filter 72 having pre-determined coefficients such that a desired filtered signal is produced. A model 70 of an analogue low pass filter is generated using a scattered parameter (s-parameter) model of the output of the analogue low pass filter with respect to its input. The signal on the second path is filtered using the generated model of the analogue low pass filter and an adaptive root raised cosine filter 74 to generate an actual filtered signal and coefficients of the adaptive root raised cosine filter are iteratively modified such that the actual filtered signal correlates closely with the desired filtered signal, to generate the phase-compensated filter coefficients.