Phase noise measurement of free-running VCO using spectrum analyzer

This work presents a cost-effective solution to measure the phase noise of a free-running microwave voltage controlled oscillator using a spectrum analyzer with add-on phase noise measurement software utility. To solve the frequency drift problem, the reference source is externally provided and tracked to the signal being tested. The system accepts random frequency drift up to +/-100 ppm. Measurement of the phase noise of a 2.5 GHz free-running voltage controlled oscillator is demonstrated. The result shows the accuracy, effectiveness and repeatability of the proposed method.