A Nonreciprocal CRLH Full-Duplex Metamaterial Leaky Wave Antenna Based on Distributed Mixing Principle

A new type of nonreciprocal composite right/left-handed leaky wave antenna (CRLH LWA) is introduced, which incorporates a distributed mixer (DM) for simultaneous transmit and receive. In this proposed design, the drain line of the DM is formed by the CRLH LWA, while the gate line consists of a conventional microstrip line. GaAs-based field-effect transistors (FETs) are used as mixing elements within the microstrip line. The local oscillator (LO) signal is injected through the input port of the microstrip line, connected to the FET gates. In the receive mode, the RF signal captured by the CRLH LWA on the drain side propagates in the same direction as the LO signal. Conversely, during the transmit mode, the RF signal is injected from the composite right/left-handed (CRLH) drain line port in the opposite direction to the LO signal. By leveraging the principles of the DM, it is demonstrated both theoretically and through measurements that the proposed CRLH DM exhibits a directional dependency in its mixing behavior. This characteristic allows for good isolation between the transmit and receive modes for the intermediate frequency (IF) signal by selecting an appropriate IF signal extracted from the other port of the CRLH drain line. This directional dependency in RF-to-IF conversion, which exhibits nonreciprocal property, provided by the CRLH DM enables simultaneous transmission and reception of the RF signal. The received information can be extracted from the downconverted IF signal.