A Wideband, Single-Layer Reflectarray Exploiting a Polarization Rotating Unit Cell

We present a new technique for designing wideband, single-layer reflectarray antennas. The proposed reflectarray exploits a wideband, polarization rotating unit cell that rotates the polarization of the reflected wave with respect to that of the incident wave by 900. This unit cell and its mirror image were used as 1 bit spatial phase shifters capable of providing a 00/1800 phase shift over a wide bandwidth of 5.4-12.7 GHz. Using this, a reflectarray antenna with 1 bit phase quantization was designed to operate at X-band with aperture dimensions of 28.8 cm x 28.8 cm and a focal length of 30 cm. A prototype of the proposed reflectarray was fabricated and characterized using a spherical near-field measurement system. We determined the antenna's 3 dB gain bandwidth to be approximately 37.4% with a maximum realized gain of 24.2 dBi. Over its entire band of operation, the polarization purity of the antenna remains better than 13 dB and sidelobe levels of better than 12 dB were achieved.