| 摘要 |
PROBLEM TO BE SOLVED: To detect a pulse noise in an AM signal with a simple circuit constitution. SOLUTION: In an AM radio receiving circuit in a double conversion system, a first IF signal is amplified by an amplifier circuit 11. The amplifier circuit 11 is constituted of a plurality of multi-stage connected amplifiers, and the added signal of the output of each amplifier is applied to a level detector circuit 12. Only level-detected noise components in the signal are allowed to pass through an HPF 13, and compared with a reference level by a comparator circuit 14. Then, a gate signal with a prescribed width is generated according to the output signal of the comparator circuit 14, and the output signal of a second mixing circuit 6 is held according to the gate signal.
|
