| 摘要 |
PURPOSE:To increase the range of receivable frequency, by dividing the receivable frequency range into almost two equal parts and setting the local oscillation frequency to a lower side wave at the high received frequency band and to un upper side wave at the low frequency band, respectively. CONSTITUTION:The local oscillation frequency is set to an upper side at the low frequency bands fRL1-fRH1 among two equally divided ranges of the receivable frequency range and at a lower part at the high frequency bands fRL2-fRH2, respectively. Thus the local oscillation frequency ranges fLL-fLH are set within the frequency ranges fRL1-fRH2. Accordingly, for the input signal supplied through an antenna 1 and the local oscillation frequency sent from an oscillator 6, the spurious signals are eliminated through band pass filters 2, 4 and 8 to be converted into an output signal f1F. In such receiving action, the variable ranges of the filters 2, 4 and 8 are set within the same frequency range. As a result, both frequency ranges can be put under the above-mentioned relation. |
