I. Introduction
As the automobile industry moves forward to meet the high demand for self-driving vehicles, it has become evident that sensors for obstacle detection and identification must be highly accurate and capable of detecting both stationary and moving objects over a wide dynamic range. Despite the initial success of semi-autonomous vehicles in the market, a plethora of accidents involving autonomous vehicles demands for sensors with much higher accuracy, longer range, and finer resolution both in range and cross-range. One critical component of the sensor suite for autonomous vehicles is radar. To enable target identification, fully polarimetric radars with high spatial resolution and Doppler resolution are needed. An instrumentation radar with very high bandwidth (>5GHz) and high Tx-Rx isolation capable of detecting targets as small as -30 dBsm at a range of 30 m has been developed and used for phenomenological studies [1]. The antenna for this radar consists of a single aperture for transmit and receive enabled by a dual-polarized spatial power divider [2]. The sensitivity of this frequency-modulated continuous-wave (FMCW) radar is limited by the isolation between the transmitter and receiver ports which is about 40 dB. This isolation level is limited by the reflection of the transmitter signal from the common lens, which is large due to the lens’ high dielectric constant. While there are several lens designs which can provide lower reflection than conventional lenses [3], because of their large size their implementation for the application at hand is prohibitive. An alternative solution is to use the proposed planar lens that makes use of reflection-less miniaturized element frequency selective surface (MEFSS) structures. In this paper, we present the design of such a lens, designated to operate at a center frequency of 79 GHz.