| 摘要 |
<p>A tuner for receiving a broadcasting signal whose frequency band is divided into high and low channels is disclosed. In this case, the tuner has first and second filters whose pass bands are fixed, a switch changeably connected to one of output terminals of said first and second filters, said switch being so changed that upon receiving a low channel said switch is changed to one state to deliver only a signal belonging to the low channel in said broadcasting signal from said first filter while upon receiving a high channel said switch is changed to the other state to deliver only a signal belonging to the high channel in said broadcasting signal from said second filter, a third filter, a local oscillator, a mixer which is supplied with a local oscillation signal from said local oscillator and a signal from one of said first and second filters through said third filter to be multiplied with each other, and means for deliving a signal from said mixer which belongs to a predetermined band as an intermediate frequency signal, and if it is assumed that the lowest frequency in the lowest band of said low channels of said broadcasting signal is taken as f1L; the highest frequency of the highest band of the low channels as f3H; the lowest frequency in the lowest band of said high channels as f4L; the highest frequency in the channel occupying the highest band of said high channels as f12H; the band width of one channel of said broadcasting signal as fB; and the lowest frequency of the intermediate frequency signal as fL, respectively, the local oscillation frequency of said local oscillator is selected higher than the frequency of the broadcasting signal at a channel when the channel is received so as to satisfy the following conditions (1) to (3): ..........(1) ..........(2) or ....... (3)</p> |
