4.1 CODE-TRACKING LOOPS
Theoretically switching from code acquisition to code tracking in this chapter means switching from open loop maximization of likelihood function (equation 3.3) to the closed-loop tracker deﬁned by equation (3.8) of Chapter 3. A variety of practical implementation options are shown in the sequel. The baseband implementation of equation (3.8) of Chapter 3 is shown in Figure 4.1. The input signal is correlated with two locally generated, mutually delayed, replicas of the pseudonoise (PN) code. After ﬁltering, the useful component of the control signal e(t) will be proportional to DD (δ) = Rc (δ − /2) −...