When designing an array, it is important to take into account the effect of its radome. The radome cannot only be used to protect the array, but also to improve the functionalities of the array. For example, it has been demonstrated that radomes can be used to reduce grating lobes or increase scanning abilities. Unfortunately, the design of radomes, given their large dimensions in terms of wavelength, can be time-consuming with commercial software of simulation. Here, we propose a physical optics method which is able to simulate arrays combined with lenses/radomes in a few seconds. Our model is extremely accurate, and it has been validated with commercial simulation software.