**6. Conclusion**

In this chapter, we discussed the reconfigurable phase holograms for the realization of microwave & RF filters, true-time delays, and beamformers, for the first time ever, to overcome the previous disadvantages of poor tunability, inflexibility, and low-resolution of conventional photonic microwave signal processors. By uploading appropriate phase holograms onto an Opto-VLSI processor, (i) full control for tap weights and tap spacings has been achieved to realize a reconfigurable RF filter; (ii) arbitrary single or multiple true-time delays could be synthesized; and (iii) a beamformer for 4-element phased-array antennas has been demonstrated. These work shows that holography is a promising technology to flexibly process microwave & RF signals with high resolution and wide waveband.
