In some papers, I found that the Q of resonator, i.e. one-port SAW resonator, can be calculated with the formula 1/f0*(diff(phi(f),f)@f=f0),phi(f) is the phase of impedance, I have tested one one-port saw resonator with the network analyzer agilent4395A under the impedance mode, then process the phase-frequency data and the modulus of impedance with the relation of frequency, the Q value calculated from the formula above is similar with the ratio between working frequency and 3dB band. Then for the two-port SAW resonator, usually can be tested under the network mode, and so I would got two data groups, one is insertion loss data in a frequency band, other one is the phase data in a frequency band, can the Q factor be calculated with the formula that for the one-port resonator? I have calculated the Q value from the two data groups,one is using formula f0/Δf(3dB band),other one is using the formula above, The results does different,but the difference is small. I want an explanation whether it is correct for the phase-frequency formula used for the Q factor calculation for the two-port SAW resonator. help,thank you in advance.