| The reflectarray antenna takes advantages of both the reflector antenna and the array antenna, by spatially illuminating an array of phased antenna elements distributed on a planar surface. In this dissertation, a general reflectarray system model is characterized by a group of configuration parameters, whose relationship with the aperture efficiency is established. This leads to rules of thumb for reflectarray antenna designs. Reflectarray antenna elements are analyzed by the infinite array theory, whereas a model based on the Equivalence Principle is applied to calculate the far-field pattern of a reflectarray system. A general procedure is proposed for reflectarray antenna designs. The phase control over individual elements is realized by the element rotation technique and the variable element size technique. The examples of an X-band, a Ka-band, a C-band, and a single-layer tri-band circularly polarized reflectarray prototype have been designed, fabricated, and measured. The X-band prototype has a gain of 30.4 dB and an aperture efficiency of 53%. The axial ratio bandwidth (AR<3dB) is 6.4%, while the -1 dB and -3 dB gain bandwidths are 2.6% and 6%, respectively. The Ka-band prototype has a gain of 29.7 dB and an aperture efficiency of 43.4%. The -1 dB gain bandwidth is larger than 10%. Moreover, the bandwidth is investigated based on the Ka-band design, mainly considering the effect of the substrate thickness. The C-band prototype may operate in both linear and circular polarization modes. The linear mode achieves a peak gain of 25.2 dB at 7.1 GHz as well as an aperture efficiency 16 %. The single-layer tri-band prototype is a combination of all the above designs. Its gains within Ka-band, X-band, and C-band are 38.7 dB, 29.1 dB, and 28.4 dB, respectively. Their corresponding -I dB bandwidths are 6.3%, 2.0%, and 1.8%.;Key Words: reflectarray; multi-band; circular polarization; aperture efficiency; bandwidth. |
