Cost effective FPGA implementation of high bandwidth communication through slip ring using circular waveguide

Usage of high resolution and high frame rate cameras in multi-sensor imaging systems has led to increased need for high computational power demanding video signal processing. One very strict requirement is to minimize payload weight on pan-tilt platforms (PT), that prevents installation of high power computers on rotation part of PT. Instead, raw video signal from multiple cameras should be transmitted via PT slip ring to the processing board which is installed as a stationary equipment. The required capacity of this communication link can easily reach values of multiple Gbps which would yield to use of very expensive slip rings with strictly impedance controlled copper contacts or even fiber optics. Additionally, the lifetime of such slip ring is much shorted than low capacity slip rings. In this paper we propose the solution that uses slip ring central opening as a circular waveguide for radio transmission of video signal. This concept originates from radars' rotary joints circuitry which additionally should transmit wideband signal. The main focus is in this paper is on simple and cost effective implementation based on FPGA serializer and deserializer as signal processing components. The coupling between FPGA and circular waveguide is provided by passive circuits and amplifiers. We have chosen coding and modulation suitable for this implementation that enables efficient digital video signal transmission over circular-waveguide based slip ring with bandpass characteristic. We have presented measurement results of 3Gbps transmission system that uses waveguide designed for cut off frequency of 10.7 GHz. The remarks about scaling this solution to different central frequencies and different bandwidths are given.