Error analysis of the unloaded Q-factors of a transmission-type resonator measured by the insertion loss method and the return loss method

Two types of measurement methods of the unloaded Q-factor of a microwave resonator, the insertion loss method and the return loss method, are reexamined theoretically and compared experimentally. An error formula is derived to estimate the errors between the unloaded Q-factors measured by the two different methods. Measured results of a stripline resonator verified the derived formula well, and proved that the return loss method is more accurate and reliable than the traditional insertion loss method.