ABSTRACT
THE phase-locked loop (PLL) is widely used in communications receiver systems. Since even the fundamental theory of phase-locked loops has been the topic of dozens of textbooks, we will only briefly discuss, then implement, a single PLL design: a discretized, second-order Costas loop [87,88]. The simplified block diagram of such a system is shown in Figure 17.1. In this figure, s[n] is the sampled input signal, m[n] is an estimate of the message signal, T is the sample period, and ω c is the carrier frequency.
