Wideband chirp generation techniques in digital phase-locked loops

In this paper in-depth analysis and comparison of two popular FM techniques, namely, two-point modulation and pre-emphasis of the modulation signal are presented. Both modulation enhancement techniques were implemented in the time domain model of an all-digital phase-locked loop (ADPLL). Their performance is evaluated based on Matlab simulations for different type of chirps. Obtained results show that chirps with the period of 0.1ms and peak-to-peak bandwidth of 1GHz can be generated with linearity better than 1% by employing either of these techniques. Additionally, advantages of two-point modulation with respect to ADPLL building block requirements are demonstrated.