AbstractAn antenna array is designed for ion cyclotron resonance heating (ICRH) for JT-60U. The coupling properties of the antenna are calculated by using the variational method for obtaining a consistent current profile on the current strap. The antenna consists of a 2 × 2 poloidal and toroidal phased loop array with two solid septa between each two antennas. The spectrum of the radiated parallel refractive index is optimized for out-of-phasing in order to obtain a high heating efficiency and a high loading resistance, and to suppress the impurity production. The predicted loading resistance is sufficient for ICRH experiments as long as the distance between the Faraday shield and plasma surface is smaller than 6 cm in the H-mode and 8 cm in the L-mode. The scattering parameters of the JT-60U antenna are measured in a low power test. The maximum with-standing RF voltage in the test stand is 38 kV which is limited by generator power and circuit losses.