Voltage controlled oscillator characterizations | Rohde & Schwarz [Video]

The setting accuracy of the frequency is depending on various factors including the linearity of the VCO, the capabilities of the phase detector and the frequency divider. As an analog voltage is controlling the output frequency of the system, a linear translation in the VCO from the input voltage to the output frequency is what designers are aiming for. This is even more important in the case of an open control situation. Frequency versus voltage plots show the principle of the VCO behavior. Additional insight to the provided linearity is provided by tuning slope versus voltage graphs. Obviously a clean, low-noise DC source is required to remove external influences while characterizing the VCO.

The other important characteristic of a VCO is its phase noise level. Classically, phase noise is measured at a certain target frequency for which the VCO needs to be tuned in. When looking across the frequency range, …