A Reconfigurable Filtering Circulator/Isolator With Continuously Controllable Center Frequency and Insertion Phase

A reconfigurable filtering circulator/isolator (RFCI) with tunable frequency and insertion phase based on the spatiotemporal modulation (STM) method is presented. The proposed RFCI mainly consists of three parallel resonator LC tanks cascaded in a delta topology. With one LC tank located at each port, both the receiver (Rx) and transmitter (Tx) channels exhibit a second-order filtering response. By adding STM signals in the delta topology, a filtering circulator is obtained. Meanwhile, two phase control networks (PCNs) are added at Rx and Tx ports, respectively. By adjusting the PCN, the insertion phase of the path from the antenna (Ant) to Rx and the one from Tx to Ant can be independently controlled while keeping all amplitude responses unchanged. Furthermore, either Rx or Tx can be turned off, thus transforming the proposed circuit into a filtering isolator with a controllable insertion phase based on signal cancellation. It integrates a bandpass filter (BPF), circulator, isolator, and phase shifter (PS) into a single, compact device. A prototype circuit is fabricated and measured for the proof-of-concept demonstration purposes.