Optical transfer function (OTF) of a Rotman lens antenna for imaging applications

This paper presents a new approach to analyzing a Rotman lens for imaging applications. The optical transfer function (OTF) is used to analyze the imaging capability of a Rotman lens. The variations in optical transfer function and the image pattern were calculated with variations in the design parameters due to beam-port spacing, antenna spacing, array size, and so on. As a result, it was found that the cutoff frequency corresponds to the array size in λ , and the resolution is the inverse of the cutoff frequency. The beam-port spacing should be narrow enough to avoid aliasing. For a typical design in which the antenna spacing is λ/2 and the scanning angle is from -45° to 45°, the number of beam ports should be π/2 times greater than the number of array ports to avoid aliasing, and the antenna spacing should be less than 0.707λ to avoid grating lobes. For the first time, a Rotman lens has been analyzed in terms of the optical transfer function. As a result, important criteria for designing a Rotman lens are presented for imaging applications. This analysis will provide guidance to the design and estimation of a focal-plane antenna array, as well as a Rotman lens for imaging and sensing applications.