Nonreciprocal Antennas based on Time-Modulation: Challenges and opportunities

We explore nonreciprocal antennas based on combining time-modulated resonators with high-Q structures. Upon an adequate low-frequency modulation scheme, such configuration enables very efficient frequency conversion between only two frequencies (one related to guided signals and another to waves in free-space) and empowers nonreciprocal phase control of the generated waves through the photonic Aharonov-Bohm effect. This approach is applied to demonstrate nonreciprocal and reconfigurable antenna configurations, including reflectarray antennas and phased arrays able to independently control transmission and reception radiation patterns at the same operation frequency. Measured results confirmed losses below 4dB and isolation levels over 40dB between transmission and reception at desired, tunable directions in space. We discuss the exciting functionalities and benefits enabled by this technology and provide a critical assessment of challenges that remain to be addressed in real-life applications. We envision that this paradigm will pave the way to a magnetic-free, fully integrated, and CMOS-compatible technology with profound implications in communication and wireless systems, sensing, imaging, and on-chip networks.