A High Precision Analog Frequency-Ramp Generator Using a Phase-Locked-Loop Structure

A high precision analog frequency-ramp-generator has been developed. The highly linear frequency-ramp is generated using a Phase-Locked-Loop (PLL) circuit design. It features a smooth analog ramp without any step behaviour normally expected of a PLL-system. In order to obtain such an analog ramp exact timing conditions have to be ensured when programming the variable divider. A synchronizing circuit is used to obtain this precise timing. As the ramp generator works well only if all parts are designed carefully, simulations are required. The ramp linearity was determined indirectly using a modified FMCW-system (Frequency Modulated Continuous Wave) especially built for these measurements and additionally by examining the synchronism of two PLL-linearization circuits with different VCOs which have significantly different tuning curves.