We propose new electro-optic modulators using a double antenna-coupled electrode structure for radio-over-fiber systems. The proposed modulators are composed of a pair of patch antennas and a standing-wave resonant electrode. By utilizing a pair of patch antennas on SiO₂ substrates and a coupled-microstrip line resonant electrode on a LiNbO₃ substrate with a symmetric configuration, high-efficiency optical modulation is obtainable for 2 ∼ 4 optical waveguides at the same time. The proposed modulators were designed at 58GHz and their basic operations were demonstrated successfully with an improvement of 9dB compared to a single antenna-coupled electrode device on a LiNbO₃ substrate in our previous work.