| 摘要 |
PURPOSE:To simplify the circuit constitution by changing over an antenna to other antenna being at a higher level when a reception signal level of the former antenna is a set value or below and performing no changeover when the signal level is the setting value or over. CONSTITUTION:A comparison circuit 10 compares a reception level signal A with each voltage level of a reference voltage signal G, generates an output signal B in response to the level and outputs the signal to a changeover pulse control circuit 14 for antenna changeover. When the reception level is lower than the reference voltage VS1, the control circuit 14 outputs an antenna changeover signal E and when the level is the voltage VS1 or over, the circuit 14 gives no changeover signal. When the reception level of antennas F1, F2 is both lower than the reference voltage VS1, the antennas are changed over with a prescribed interval to select an antenna with a higher reception level. A voltage reduction circuit 16 attenuates the reference voltage G for a prescribed period when the control circuit 14 outputs the 1st changeover pulse and when the reception level of the changed-over antenna is lower than the level before the changeover, the control circuit 14 changes over again the changed-over antenna to the original antenna.
|
