Design of a 2-bit Unit-Cell for Electronically Reconfigurable Transmitarrays at Ka-band

International audience; This paper presents in detail the design of a linearly polarized electronically reconfigurable unit-cell for transmitarray antennas with a 2-bit phase resolution in Ka-band. The size of the proposed unit-cell is 5.1x5.1x1.3 mm(3). It is implemented on a dielectric stack-up composed of six metal layers, three dielectric substrates and two bonding films. The radiating elements are printed on both external metallic layers and are loaded by two PIN diodes controlling the transmission phase. This unit-cell is used to design a 196-element transmitarray with 784 PIN diodes. The performance of this 2-bit transmitarray has been evaluated numerically using our in-house simulation tool and compared to a transmitarray with a 1-bit phase quantization. A maximum gain of 22.9 dBi, an aperture efficiency of 32.3%, and a side-lobe level equal to -18.1 dB at broadside have been obtained at 29 GHz.