Electronically Reconfigurable Reflectarray Antennas for Mobile Troposcatter Communications

Conventional tropospheric scattering (troposcatter) communications primarily use electrically large reflector antennas for point-to-point communications, which suffer from bulky volumes and difficulties in maintaining beam-pointing accuracy. Beam pointing and tracking problems in troposcatter communications applications may be alleviated by the aid of phased-array antennas at the transmit and receive locations. In this paper, we present an electronically reconfigurable reflectarray designed to perform accurate beam steering and tracking in trposcatter communications systems. This reflectarraty uses an electronically reconfigurable unit cell providing 2-bit reflection phase shift quantization. The unit cell consists of an E-shaped patch placed above a ground plane. The patch is connected to a reflecting circuit electronically controlled by three PIN diodes below the ground plane to provide 2-bit phase shift. The proposed unit cells can provide less than 0.55 dB/bit loss and less than 15° phase error at the target frequency range (5.8-6 GHz). Full-wave simulations of a 208-element reflectarray incorporating the proposed unit cell have demonstrated the performance feasibility of the design concept.