Technique allowing rapid frequency sweeping in aided-acquisition phase-locked loops

Phase-locked loops employing analogue phase detectors have a capture range limited to several times the loop natural frequency. In many applications this is insufficient to accommodate the likely frequency variation of the signal to which the loop is locked, and so a sweeping technique is used to aid the acquisition process. However, the rate at which the loop may be swept is also dependent on the loop natural frequency and can be very low in practice. This paper considers a method allowing particularly rapid sweeping and involves a detailed analysis of the proposed technique along with theoretical and experimental results showing the improvement in performance that is possible