| 摘要 |
PROBLEM TO BE SOLVED: To provide a radio receiver which is shared by two different systems by connecting a 1st A/D converter and a QAM synchrodyne circuit after a 1st intermediate frequency amplifier chain, connecting a 2nd A/D converter and a VSB synchrodyne circuit after a 2nd intermediate frequency amplifier chain, and setting the selectivity of the latter chain at a level higher than that of the former chain. SOLUTION: The TV signals received through an antenna are supplied to the 1st and 2nd intermediate frequency amplifier chains connected in parallel to each other via a high frequency amplifier 2. The 1st intermediate frequency amplifier chain consists of a 1st mixer 11, a high IF band buffer amplifier 12, a QAM DTV SAW filter 13, a 2nd mixer 14, a low IF band buffer amplifier 15, an inverse AGC type low IF band amplifier 17 and a 3rd mixer 18. The output is digitized so as to be applied to a QAM DTV synchrodyne circuit 4. So is with the 2nd intermediate frequency amplifier chain. Both chains differ from each other in terms of their bands. |
