Cassegrain Offset Subreflector-Fed X/Ka Dual-Band Reflectarray With Thin Membranes

The development of a 0.75-m Cassegrain offset subreflector-fed X/Ka dual-band reflectarray antenna is presented. The subreflector (SR) is fabricated using combinations of prescribed geometric parameters and two left-hand circularly polarized microstrip patch arrays are designed as feed networks with one covering X-band and the other covering Ka-band. The phase corrections in the reflectarray required to form a planar phase front are realized by rotating microstrip ring elements. Low-dielectric constant foam layers are inserted below both the X- and Ka-band membranes to act as support structures and to minimize the degrading effects of thin substrates. It is believed that this is the first Cassegrain offset-fed reflectarray ever been developed. The measured results show efficiencies around 50% for both frequency bands with room for improvements