An Offset Linear-Array-Fed Ku/Ka Dual-Band Reflectarray for Planet Cloud/Precipitation Radar

A Ku/Ka band dual-frequency offset array-fed microstrip reflectarray antenna using thin membranes has been developed. This antenna is a demonstration model for the next generation titan cloud precipitation radar and altimeter (TCPRA) and is intended to enhance the capability of the future cloud and precipitation remote sensing system for Earth and other planets. The reflectarray has a dimension of 0.5-m square and a flat aperture that emulates a cylindrical reflector antenna. Two sets of linear arrays with linearly polarized microstrip elements and having low cross polarization and low sidelobe levels (SLL) are placed along the focal line to illuminate the reflectarray. One set is for Ku-band, while the other is for Ka-band. Within each set, the wide-swath scanning capability of the antenna is provided by the two fixed-beam feed arrays with one for broadside beam and the other one for a 20deg tilted beam. The unique feature of this paper is that this is the first offset-fed reflectarray that has ever been practically developed to emulate a cylindrical/parabolic type of reflector antenna. In addition, new dual-concentric-ring elements and ring-patch elements are uniquely applied here to achieve the desirable wide phase variation characteristics. Tests of feed arrays and the reflectarray in the anechoic chamber of Texas A&M University result in good pattern performance and the successful demonstration of beam scanning at both frequency bands.