We propose a novel wavefront sensor for radio telescopes with a point diffraction interferometer. A point-like object is set at a pupil plane and the electric field at the focal plane is measured. A receiver dedicated to the novel sensor is prepared which has delay lines to make interferograms. A procedure to estimate the electric field at the pupil is shown analytically. Numerical simulation reveals that the proposed system allows us to measure the phase of the electric field at the pupil with a precision of about λ/28.