Automatic frequency control circuit - has phase discriminator only active during leading or trailing edge of VCO output

摘要

The automatic frequency control circuit synchronises an oscillator's frequency to a reference frequency using a discriminator to detect the phase difference between the two signals being synchronised. The discriminator is controlled by a logic circuit supplied with a reference frequency and the oscillator's frequency. The logic circuit is controlled so that the discriminator is only active either during the leading or the trailing edge of the oscillator's output.