| 摘要 |
The present invention provides a mechanism for reducing a frequency transient (Fig. 7) appearing at the output of a voltage controlled oscillator (VCO) (60) in a frequency synthesizer (Fig. 6) when a load (72) is connected to the VCO (60). In accordance with the present invention (Figs. 9-11), the magnitude and direction of (a) the frequency transient and (b) the frequency deviation of the VCO signal in response to a reference input voltage may be measured, and those measurements used to generate a frequency correction voltage (V2) which would cause the VCO signal to deviate in an equal amplitude but in an opposite direction to the frequency transient. The frequency correction voltage (V2) then can be applied to the VCO when it is connected to the load so as to substantially cancel the frequency transient. The frequency synthesizer may be used in a mobile station comprising a transmitter which constitutes a load for the VCO (60). Alternatively, the mobile station may comprise an IQ modulator (46) for modulating the VCO signal with an in-phase signal (I) and a quadrature signal (Q), the transmitter transmitting the modulated signal from the IQ modulator. In this case the frequency correction voltage (V2) can be applied to the IQ modulator (46) to cancel the frequency transient appearing at the VCO output when the transmitter is turned on. |
