A W-Band Low-Profile Dual-Polarized Reflectarray With Integrated Feed for In-Band Full-Duplex Application

A W-band low-profile dual-polarized Cassegrain reflectarray with an integrated feed is designed in this work. High isolation, which is necessary for the in-band full-duplex (IBFD) applications, is realized between two feeding ports corresponding to the orthogonal polarizations. The antenna is composed of two parts, i.e., the dual-polarized planar-array feed and the Cassegrain reflectarray with a small focal-length to diameter ratio (
$F/D)$
. The dual-polarized planar array feed is appressed behind the main-reflectarray, and the
$F/D$
is reduced to 0.2 to realize the integration and the low-profile property. For the array feed, high isolation is achieved through the orthogonal-mode isolation and the differential signal cancellation. Its radiation pattern is also manipulated to fit the reflectarray considering the taper and spillover efficiency. For the reflectarray, the rotational symmetry configuration and the dual-layer-patch cell are applied to suit the dual-polarization operation and the large incident angle, respectively. The measured operation band, where the gain variation is within 1 dB, is 93.4–95.6 GHz. At the center frequency, the gains of the Cassegrain reflectarray for the two ports are 31.86 and 30.88 dBi, and the corresponding aperture efficiencies are 31.4% and 25.1%, respectively. The isolation between the two ports is higher than 55 dB within the operation band. This work is a low-profile candidate for W-band point-to-point IBFD communication.