Opto-electronic free-space processor for UMTS signal filtering

The availability of optoelectronic components operating in the multi-gigahertz domain (up to 20 GHz) is very attractive for implementing basic optical processing functions of microwave signals such as spectrum analysis, adaptive filtering, and correlation suitable in radar and electronic communication systems. We present an optoelectronic free-space processor for filtering up-link and down-link signals in UMTS base stations. The system uses a liquid-crystal spatial light modulator to set programmable filtering functions. We have demonstrated signal rejections higher than -40 dB at 2.3 GHz (from 2.1 GHz) and low insertion losses of -18 dB. Moreover, tunability of the filters implemented in the free-space demonstrator has also been successfully addressed