A fast digital phase locked loop based on model predictive controller

This paper presents a new approach for design of a digital phase locked loop. By employing a digitally controlled oscillator (DCO) and a time-to-digital converter (TDC), the loop filter of a DPLL becomes all-digital. Instead of designing the loop filter by digitizing a continuous-time loop response as has been commonly done, more sophisticated control schemes can be employed. In this paper, we proposed to design feedback loop filter by first modeling the DCO and TDC as appropriate model in transfer function form. Then by employing model predictive control (MPC) approach for design of loop filter instead of existing conventional loop filter generate optimal signal that accurately account for the transport delay in the digital feedback system. Using the proposed approach loop filter can overcome latency problem that digital feedback loops suffer and imposes limitation on loop bandwidth and even can make instability on loop. Simulation results by MATLAB confirm ability of the proposed design and shows it is suitable for digital phase locked loop.