Surface Resistance Measurement Using Cavity Resonator: x <3-dB Bandwidth Method

In conventional surface resistance $R_{s}$ measurement using cavity resonator, the 3-dB bandwidth method is frequently used for quality factor (Q-factor) extraction, in which the swept frequency bandwidth should be multiple of 3-dB bandwidth. However, sometimes, it is unable to measure resonator whose measurable bandwidth is smaller than 3 dB. Here, an x-dB bandwidth method is studied for Q-factor extraction and its feasibility is demonstrated by $R_{s}$ measurements with a TE011 mode cylindrical cavity resonator and a quasi-optical cavity.