This paper presents two microstrip reflectarray designs based on variable size unit cells for 10 GHz. One design uses a 3-layer unit cell with polygon shaped patch and the other uses a unit cell with 1-layer square loop patch. Both arrays have a size of 10λ × 10λ at 10 GHz, can reflect the incoming wave as a high gain pencil beam in the desired direction of θ = 30°. Gains at 10 GHz are 23.6 dB and 26.1 dB for the 3-layer and one-layer structures, respectively. The multi-layer structure resulted in a wider gain banwdith. Simulation results show that the 3-dB gain bandwdith is about 22% for the 3-layer structure reflectarray, as compared to 12% for the one-layer structure.

This paper presents microstrip reflectarray design using variable size unit cell approach for 26 GHz, and investigates the effect of feed antenna distance to the surface. The unit cell structure is made up of a 1.5 mm foam layer (εr=1.37) and a 0.787 mm substrate layer (εr=2.2) between the ground and reflective layers. Two arrays of 14λx14λ in size were designed to reflect the incoming wave in the θ=25º direction; the distance to the feed was 160 mm in one design and 320 mm in the other design. Simulation results show gain of 30.2 dBi for the former and 29.8 dBi for the latter. 3-dB gain bandwidths were 11 % and 14 %, respectively

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