  This Perspective examines the emerging applications of photonic topological
insulators (PTIs) in the microwave domain. The introduction of topological
protection of light has revolutionized the traditional perspective of wave
propagation through the demonstration of backscatter-free waveguides in the
presence of sharp bending and strong structural defects. The pseudospin degree
of freedom of light enables the invention of unprecedented topological photonic
devices with useful functionalities. Our aim is to present a brief introduction
of recent developments in microwave PTI demonstrations. We give a clear
comparison of different PTI realizations, summarize the key features giving
rise to topological protection, and present a discussion of advantages and
disadvantages of PTI technology compared to existing microwave device
technology. We conclude with forward-looking perspectives of how the advantages
of this technology can best be exploited.
