Time delay digital tanlock loop with acquisition-aided circuit

This paper proposes two circuit topologies for acquisition enhancement in a time delay digital tanlock loop (TDTL). They are based on feedforward (FF) and feedback (FB) control schemes. Both schemes are used to improve the acquisition speed of the conventional TDTL by employing an auxiliary circuit. The ultimate objective of the FB and FF techniques is to control the damping ratio so as to prevent overshoot which may cause oscillations. However, the FF topology, with an adaptive threshold as opposed to a fixed threshold in the FB scheme, provides better control and improved response. The performance of the proposed FF and FB mechanisms have been investigated, under noise free conditions, by analysis and computer simulation and the results are presented. The results indicate that it is possible to bring the system into the steady state preventing continuous oscillations whenever the system is thrown outside the locking range.