Resonant free-spectral-range (FSR) RF-optic modulators using dual-disc resonators with a 2:1 ratio of the radii of the discs have been proposed and theoretically analyzed to increase the sensitivity-bandwidth product compared with that of a single resonator modulator. The transmission of the coupled resonator structure is analyzed for various coupling parameters. The phase of the larger resonator is electro-optically modulated, and the output fields at the input laser frequency and the generated sideband frequencies are calculated. The detected RF power is then calculated. The modulator sensitivity, 3-dBe modulation bandwidth, and their product have been analyzed. The sensitivity and modulation bandwidth can be increased by factors of 1.9 and 6.4, respectively, for the different cases. The sensitivity-bandwidth product can be increased up to a factor of 3.3 in one design. For ??5% error of the ratio of the radius of each disc, errors of the sensitivity and modulation bandwidth were acceptable.