| 摘要 |
PURPOSE:To decrease bit errors of transmission signals by switching the time constant of an oscillator at a zero-cross point of an oscillated waveform in response to the arrival of a switch signal and eliminating a higher harmonic component caused by a switching action to avoid the malfunction at the reception side. CONSTITUTION:A switch signal D sent from a switch circuit 22 is converted into a switch control signal E synchronous with the zero-cross point of a waveform A produced by a voltage control oscillator 2 through a switch control circuit 24. The signal E is applied to a switch circuit 4. Therefore the circuit 4 is switched in a transmission mode at the zero-cross point of the waveform A which is closest to the front edge of the signal D. Then a resistance 6A or 6B is selected and a prescribed time constant is set. As a result, the oscillation frequency is switched at the zero-cross point of the waveform A. Then a continuous oscillated waveform C of a different frequency is obtained. Then a switch signal F is applied to a gate circuit 14 from a switch circuit 18 in response to a switch input. The circuit 14 is kept in a transmission mode while the signal F is kept at an H level. Then a transmission waveform G is delivered through an output terminal 20. |
