Equalizer for radio receive signal

Abstract

In a transversal type equalizer having a series connected delay elements, multipliers are coupled with each output of each delay element and an adder adds outputs of the multipliers to provide an equalized output signal for equalizing a time division radio receive signal for every burst in mobile communication. A receive memory (11) stores the receive signal. A transversal type equalization process circuit (77a) is coupled with the output of the memory (11). A output memory (100) stores on equalized output signal. In training tap coefficients of a transversal filter, a tap or a delay element is precluded when an absolute value of a tap coefficient is less than a predetermined value, so that calculation amount for updating tap coefficients is decreased and tracking characteristics are improved. A multiplier (15) is inserted between an output of the receive memory (11) and an input of the equalization process circuit (77a) so that a signal which is subject to equalization is phase-shifted beforehand so that frequency offset between transmit frequency in a transmitter and local frequency in a receiver is compensated. The phase adjustment by the multiplier (15) depends upon residual phase error at an output of the equalization process circuit (77a). An output memory (100) is used as a training signal to initialize the tap coefficients of the equalization process circuit (77a) during a burst when equalized output signal has an error larger than a predetermined value.