| 摘要 |
PURPOSE:To quicken the frequency pull-in speed of an automatic frequency control circuit by employing a frequency discriminator which inputs frequency information of an in-phase channel and an orthogonal channel, and generates and outputs a tangent frequency control signal corresponding to the result of inputting. CONSTITUTION:A signal of an in-phase channel I and a signal of an orthogonal channel Q are respectively referred to as I(t)=Acos(2piDELTAft+theta) and Q(t)=Acos(2piDELTAft+theta), where A is an amplitude, theta is a phase, and DELTAf is frequency information. When the signals I(t),Q(t) are inputted to a frequency discriminator, in which they are added, resulting that an output (d) of the frequency discriminator is expressed as d=tan(piDELTAftau), where tau is a delay time, then a tangent frequency control signal is obtained. The gradient of the output signal (d) of the frequency discriminator is expressed as sec<2>(piDELTAftau) and larger than the gradient in the frequency discrimination characteristic of a conventional control circuit. Thus, the frequency pull-in speed is much more increased. |
