A six-port-based frequency discriminator for phase noise measurement is proposed. This circuit makes use of a delay line discriminator configuration, thus not requiring reference oscillator. Furthermore, the use of a six-port network allows an extremely simple and completely passive solution well suited for low power oscillator measurement. A detailed study of the architecture is performed including the system noise sources. Besides, a prototype of the proposed six-port based delay line frequency discriminator is evaluated. Phase noise measurements of a commercial RF VCO are performed and compared with the results obtained with commercial metrology equipment with good agreement.
