| 摘要 |
PURPOSE:To reduce the number of antenna changeovers to suppress the deterioration of the reception quality, by changing the threshold or the phase characteristic in an antenna switching detecting circuit by a signal corresponding to the field intensity of a receiving signal and a signal which detects distortion components generated by a multipath or the like. CONSTITUTION:The antenna changeover detecting circuit is provided with a comparator 17 to which a signal (a) obtained by superimposing AC components generated by a multipath or the like upon a DC current corresponding to the field intensity detected by an AM detector 6 is inputted, a phase shifter having a transistor TR14, and a selective discriminating circuit 25. The signal (a) and a signal (b) obtained by delaying the signal (a) in the phase shifter are compared with each other by the comparator 17, and DC components of the output are applied to a TR24 and the circuit 25. The electric charge charged to a capacitor in accordance with the state of the signal (a) is controlled by the output of the TR24. The receiving signal corresponding to the field intensity and distortion components generated by the multipath or the like are detected to change the threshold or the phase characteristic in the circuit, thereby reducing the frequency of switching of antennas 1a and 1b. |
