| 摘要 |
PROBLEM TO BE SOLVED: To provide a radio reception circuit effective for a digital TV receiver by allocating a channel to the amplitude modulation transmission of a radio carrier in accordance with a digital signal showing TV information and permitting a frequency to covert the selected channel into a secondary intermediate frequency signal in a secondary intermediate frequency band. SOLUTION: A digital TV signal received by the radio frequency through an antenna 1 is amplified by a radio frequency amplifier 2 and is heterodyned with local oscillation generated by a local oscillator 4 in a mixer 3. The mixer 3 converts the frequency of the selected digital TV signal into a first intermediate frequency band and transmits it to a surface acoustic wave(SAW) filter 6 designed to select the signal which is converted into the intermediate frequency band through a UHF band intermediate frequency amplifier 5. The SAW filter 6 is driven with optimum power impedance. Thus, SAW filtering for deciding the band width of the receiver can more easily be executed in the UHF band of 917-923 MHz. |
