| 摘要 |
PURPOSE:To reduce the number of parts by using a passing band width adjusting filter provided to a receiving circuit as the filter of a transmitting circuit. CONSTITUTION:A reception system circuit consists of a high frequency amplifier 2, mixer 3, and a filter 4 for transmission and reception, and a width function filter part A is used as the filter of a transmission system circuit in common. The width function filter part A consists of mixers 5 and 7, a filter 6 for width, a voltage-controlled oscillator 10 for width, and a control voltage switch 18. The switch 18 switches control voltages for transmission and reception and switched to the side of a variable resistor 11 during the reception to control overall passing band width as well as the characteristics of the filter 4. On the other hand, the switch is changed over to the side of a fixed voltage circuit 21 during the transmission and a speed signal modulated by a modulator 13 is band-limited and supplied to a limiter 15. |
