Microwave photonic concepts and functionalities

In this chapter, we introduce the principal concepts and functionalities that photonics can bring in the microwave systems. The discussion will focus in particular on the application of photonics to radars and to electronic warfare (EW) systems. The analysis will compare the performance of several standard microwave subsystems with the latest results obtained by using photonics, either coming from the research labs or, where available, from the pioneering microwave photonics industry. The potentials of photonics in improving the performance with respect to the standard approaches are stated. Moreover, several novel peculiar possibilities that photonics can enable are highlighted. In order to be fruitful to the largest technical audience, the analysis will avoid discussing the photonic solutions in deep details, which would require the experience of a photonic specialist to be fully understood. Nevertheless, the descriptions will let the reader getting the main concepts, and the reported numbers will allow a direct comparison with the standard microwave system counterparts. For those who will be willing to reach a deeper insight, several references are provided. After an introductory paragraph on the general benefits brought about by photonics, this chapter takes into account the basic functionalities of microwave systems: the generation and detection of the microwave signal, its transmission and distribution, the signal conditioning for the beamforming function in phased array antennas (PAAs), and the signal filtering. The potentials coming from the integration of photonics are also discussed in a dedicated paragraph. Finally, the main points raised in this analysis are summarized.