Full Duplex Filtering Antenna with Nonreciprocal Transmission Characteristic Using SIW and Spatiotemporal Modulation

In this paper, a full duplex (FD) filtering antenna with nonreciprocal transmission characteristic, implemented by substrate integrated waveguide (SIW) integrated with the spatiotemporal modulation (STM) method, is proposed. The design features three input/output ports: transmitting (Tx), receiving (Rx), and antenna (Ant). It consists of three 120° fan-shaped SIW cavities that are coupled in a delta topology through electric-magnetic coupling (EMC) structures, thereby forming a stable second-order filtering response for each transmission channel created by two adjacent SIW cavities. Three STM signals of the same amplitude and frequency, but with a progressive 120° phase difference, are applied to the non-linear capacitors placed on the EMC structures, resulting in the formation of a filtering circulator. Additionally, a radiation slot antenna is etched on the top layer of the SIW cavity of the Ant port, enabling the radiation function. This design seamlessly integrates the functions of a bandpass filter (BPF), a circulator, and an antenna into a single, integrated device. To validate the concept, a prototype is designed, fabricated, and measured.