Floquet Modulation Optimizing the Tunable Isolators Based on PT-Symmetric LCR Resonators

Isolators on antennas, the typical non-reciprocal devices, are used to protect high-power wireless transmitters from signal reflections. Currently, the widely used isolators are based on ferrite and other magnetic materials, which can’t meet the requirements of future communication technology for miniaturization as well as the compatibility with integrated circuit processes. This work introduces a Parity-Time ( PT) symmetric LCR circuit to realize an integrated isolator. A pair of LCR resonators with gain and loss respectively are coupled by a varied capacitor to achieve tunable frequency. Floquet modulation is introduced to the loss resonator to generate multiple resonant modes that can be filtered in forward transmission while excited in backward transmission. The proposed isolator based on modulated PT-symmetric resonators is implemented on a printed circuit board in this work, the isolator designed achieves an insertion loss of -5.26dB with the isolation of 24.54dB at the center frequency of 12MHz. The non-reciprocal ratio is achieved as high as 29.8dB, which is much higher than the typical static counterpart. Besides, the nonreciprocal ratio still remains 25dB even with a 10% asymmetric design of the system, which breaks the limitations of PT-symmetric requirements. This work provides a potential solution for the future minimized isolators and asymmetric fabrication of PT-symmetric circuits.