DIGITAL RECEIVER DEVICE HAVING NORIABLE INTER-FREQUENCY FILTER

摘要

The center frequency of a channel filter is varied according to Doppler frequency variation to minimize the distortion occurred in roll-off region. The receiver includes a first mixer(202) for generating intermediate signal by mixing output signals of a duplex filter and an oscillator, a channel filter(204) for adjusting center frequency, a lowpass filter(205) for filtering output signal of the channel filter(204), a bit timer(208) for sampling output signal of the lowpass filter, and center frequency adjuster(206) for providing center frequency adjusting voltage to the channel filter(204).