| 摘要 |
PURPOSE: A tuner for receiving a digital satellite broadcast is provided to convert a tuning voltage of an RF tracking filter and to vary a pass band width, thereby minimizing an interference between channels in a low symbol rate. CONSTITUTION: In a tuner for receiving a digital satellite broadcast, a PLL IC(40) applies a desired voltage to a loop filter(5) depending on a channel data and controls a tuning voltage to be output from the loop filter. An RF tracking filter(30) includes the PLL IC, a HPF and an LPF. The HPF and LPF allow to output a desired high-frequency signal among high-frequency signals input depending on the tuning voltage input in the loop filter. The tuning voltage is varied by applying the signal output from the output port of the PLL IC to the HPF and LPF depending on the amplitude of the signal, thereby changing a cut-off frequency of the HPF and LPF.
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