Millimeter-Wave Short-Focus Thin Lens Employing Disparate Filter Arrays

This letter presents a millimeter-wave thin lens employing disparate filter arrays created by placing both metallic patches and wire mesh on the same plane. This disparate configuration of patches and wire mesh enables the coexistence of two different types of filter response, lowpass and bandpass, on the same plane. It is found that this disparate design can achieve improvement in the tunable range of phase shift of the spatial filter array with a limited number of metal and substrate layers so as to retain the thin feature of the lens. This arrangement enables higher focusing gain than prior thin lenses employing single-type spatial filter arrays for a short focus of f/D = 0.2, where f is the focal length and D is the lateral dimension (aperture) of the lens. The design procedure for the proposed lens employing the disparate filter arrays is discussed. Full-wave simulation results demonstrate that the proposed lens can achieve more than 2 dB in gain enhancement over previous thin lenses made of only lowpass filter arrays. The fabricated lens is confirmed to have less than 0.05 λ0 in total thickness and up to11 dB in gain for f/D = 0.2.