The carrier frequency of received signals and oscillating frequency of local oscillator in the receiver should be compared under AFC in a PSK signal transmission system. The cross-product frequency discriminator is selected for the discrimination of two input signal frequency differences. The analog discriminator does not work well because of phase-lock phenomena. We transformed this analog discriminator circuit into digitalized one for the purpose of obtaining stableness, high gain, and flexibility. The performance of AFC circuit using the digitalized discriminator was designed, measured and analyzed under the carrier frequency of 10.7MHz and symbol rates of 64kb/s. Experimented results show that the excellent frequency repression effect of less than 7 is obtained and the error rates were minimized within 0.6dB in the incoming frequency discrepancy of ±25kHz.
展开▼
