TUNER

摘要

PROBLEM TO BE SOLVED: To provide a tuner with a filter which meets strict characteristics requirements to receive digital terrestrial broadcasting waves. SOLUTION: The tuner comprises single frequency converters (4 and 7) provided with a mixer 4 and a local oscillator 7, and a variable low path filter 3 provided between the mixer 4 and the tuner's input part. The frequency converter converts a selected channel to an intermediate frequency other than 0 for demodulation. The mixer is an image suppression mixer. The local oscillator supplies a local oscillation signal to the mixer. The local oscillation frequency is substantially equal to a sum of the frequency of the selected channel and the output intermediate frequency. The low path filter is arranged so as to track the local oscillating frequency without adjustment. The turnover frequency of the filter is set to be larger than the selected channel frequency and not larger than a sum of the selected channel frequency and twice the output intermediate frequency. COPYRIGHT: (C)2004,JPO