| 摘要 |
<p>A tuner for receiving satellite broadcasting includes: a filter means composed of a multiple number of variable band-pass filters having different frequency ranges and selecting means for selecting one of the variable band-pass filters in conformity with the frequency of a tuned broadcasting station; a frequency converting circuit composed of a local oscillator circuit and a mixer circuit outputting an intermediate frequency signal; and a demodulating circuit for extracting the original wave signal from the intermediate frequency signal. In this configuration, when the frequency of a tuned broadcasting station is greater than a predetermined frequency, the frequency converting circuit converts the tuned high-frequency signal to the intermediate frequency signal based on the downside heterodyne scheme; and when the frequency of a tuned broadcasting station is lower than the predetermined frequency the frequency converting circuit effects the conversion of the tuned high-frequency signal to the intermediate frequency signal based on the upside heterodyne scheme. <IMAGE></p> |
