| 摘要 |
In a phase locked loop, a voltage controlled oscillator VCO is formed in a way known as such from a current controlled oscillator CCO (21), the actual control current (ICNTRL) of which is formed by a voltage-to-current amplifier (22). The input voltage of this amplifier is the loop filter's output voltage and it converts the output voltage into the oscillator's control current. When setting the oscillator at a desired medium frequency, the procedure according to the invention is such that a separate setting circuit is used for generating a basic current (IDA), which is led as control current to the oscillator (21) input. The magnitude of the basic current may be controlled in steps. When the desired oscillator frequency has been formed, the current supplied by the setting circuit is frozen at this value and the loop filter voltage is connected to affect the voltage-to-current amplifier, whereby the phase-locked loop will close. |
