Transmission timing control device, digital roll-off filter and mobile radio terminal for digital radio communication

摘要

In a mobile radio terminal at transmission timing control device, transmit data spread-modulated is delayed by a timing control portion (103) with a timing of reception as a reference by a predetermined period of time having based on a unit time corresponding to a chip clock and it is then provided to a filtering portion (109). The filtering portion (109) limits the transmit data in band and a timing control portion (110) times transmission with a slight adjustment with an oversampling clock, a quadruple in frequency of the chip clock, serving as a unit time. In a mobile radio terminal at a digital roll-off filter, input digital data is held in accordance with a data period by a shift register (11) successively. A counter (13) counts in accordance with an oversampling period of <1>/m and it is reset in accordance with a data period. A coefficient select circuit (12) is driven by the counter's output to select and output repetitively, sequentially tap coefficients corresponding to m sampling points included in the data period for each tap output of the shift register (11). A multiplication circuit (14) multiplies tap outputs by corresponding output tap coefficients and an addition circuit (5) sums up such multiplications and provides the sum as a filter output. <IMAGE>