Integrated MicroPhotonic Beamformer for Broadband Adaptive Nulling in Smart Antennas

Summary form only given. The enormous growth of the number of broadband wireless subscribers has driven the need for increasing the capacity of wireless networks to accommodate larger volumes of broadband subscribers. Digital signal processing is currently thwarted by the limited bandwidth of analog-to-digital converters and conventional radio frequency (RF) signal processing is also limited by the loss of metallic media at RF frequencies. Photonic RF signal processing is a promising approach which allows wideband RF signals to be delayed in the optical domain with negligible loss. This paper presents an integrated microphotonic beamformer that processes RF-modulated optical signals to adaptively synthesise multiple broadband nulls in smart phased-array antennas. In this system, the incoming antenna RF signals are split and converted into modulated optical beams via a vertical cavity surface emitting laser (VCSEL) array and routed into a multi-cavity optical substrate, which generates different true-time delayed versions of the input RF signals. A photoreceiver array, operating in ON-OFF mode, integrated onto the optical substrate converts the modulated light beams into RF signals and combines them to produce the output RF signal. By selecting and combining appropriate delayed signals arbitrary broadband spatial nulls can be synthesised. The beamformer is designed to operate at 5.6 GHz with 1 GHz bandwidth. Results showing the design and performance of the different photonic and RF components were presented.