Threshold Analysis of Phase-Locked-Loop Demodulators Using Most Likely Noise

A new method for determining the number of spikes per second, and hence the threshold carrier-to-noise ratio (CNR), of the phase-locked-loop demodulator is presented. This technique can also be applied to the frequency demodulator with feedback. This method is applicable when nonwhite noise is present at the input of the demodulator and also when the carrier is frequency modulated. Computer processing is employed so that rapid comparisons of the phase-locked-loop (PLL) systems can be made. The results show the spikes per second and the threshold CNR, without modulation, for the first-, second-, and third-order PLL and FM discriminator. Experimental results are then presented.