Finding schemes to promote the efficiency of phase gating nowadays is a main concern. We address this issue by devising a feasible and innovative scheme that enables us to obtain a gain-phase grating. It is shown that a linearly polarized probe field traveling through a double V-type closed-loop atomic system, which is driven by a standing wave and a microwave field, can be efficiently diffracted in higher orders. As a significant result, we find that intensity of the diffracted field is highly amplified in every single order direction compared with the intensity of the input probe field. The responsible mechanism is induced gain accompanied by the large dispersion arising due to the applying microwave field. It is shown that in the presence of a microwave field, among various parameters, the relative phase of the applied fields has the most appreciable effect on enhancing the intensity of diffraction orders. It is also demonstrated that quantum interference between decay channels of the quantum system can be used as a tool to manipulate the intensity of diffraction orders.