A Dual-Band, Polarization-Rotating Reflectarray With Independent Phase Control at Each Band

We present the design and proof-of-concept demonstration of a dual-band reflectarray antenna capable of generating two beams at X- and Ku-bands, whose directions of maximum radiation can be set independently of each other. The reflectarray uses dual-band polarization-rotating (PR) unit cells with 1 bit phase quantization. The proposed unit cell provides independent phase shifts at two frequency bands by controlling a cluster of two orthogonal dipoles to operate as either +90 degrees or -90 degrees reflective polarization rotators. Two dipole clusters are interleaved in a unit cell and used to achieve dual-band operation. Simulation results of a unit cell designed to operate at X- and Ku-bands demonstrate independently controlled, dual-band PR operation over 16.1% and 20% bandwidths for the lower and higher bands, respectively. The dual-band unit cells were used to construct three different static reflectarray prototypes demonstrating the different ways where such independent phase control at the two bands of a dual-band reflectarray antenna may be advantageous. The three static reflectarray prototypes were simulated, fabricated, and experimentally characterized. Simulation and measurement results of these prototypes agree well and demonstrate independent phase shift control at the X- and Ku-bands over a relatively wide field of view without exciting grating lobes.