Design of a patch array feed for the dielectric lens antenna achieving wide angle beam scanning

In the recent ITS (Intelligent Transportation Systems) services using millimeter wave frequency bands, dielectric lens antennas were studied for a radar system of adaptive cruise control (ACC) of automobiles. Authors developed a shaped dielectric lens antenna which was suitable for wide angle beam scanning and beam scanning abilities were ensured. Moreover, by introducing an array feed of rectangular horns, more improvement of the scanned beam gains and radiation patterns were numerically shown. Here, replacement of a horn antenna by a patch antenna is requested in order to reduce a feed volume and weight. In this paper, a patch array feed composed of feed element patches having equivalent radiation patterns to the horn array feed is developed. Study frequency of 20 GHz is selected for the ease of fabrication. First of all, suitable configuration of the feed element patch is found out. The configuration of three rectangular patches connected with thin coupling lines is shown to have equivalent radiation patterns to the horn. Next, patch array feeds for on-focus and off-focus uses are developed. As for the on-focus feed, three feed element patches are employed. Sufficient axi-symmetrical radiation and constant phase patterns are ensured. As for the off-focus feed, eight feed element patches are employed. By applying designed excitation coefficients to the patch array feed, sufficient axi-symmetrical radiation amplitude pattern is achieved. Moreover, the expected radiation phase pattern is also achieved. Through this study, usefulness of the developed feed element patches is ensured.