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A novel integrated leaky-wave antenna-duplexer/diplexer, based on the CRLH uniform ferrite-loaded open radiating waveguide is introduced, demonstrated and characterized both numerically and experimentally. The duplexing operation, characterized by equal Tx and Rx frequencies, is performed directly within the antenna thanks to the non-reciprocity of the ferrite, thereby suppressing the need for a circulator external to the antenna. The diplexing function, where the Tx and Rx frequencies are different, is achieved by inclining the plane of the antenna structure with respect to the normal of the radiation direction. The duplexer may be seen as the particular case of the diplexer with an inclination angle of zero. Virtually unlimited Tx → Rx isolation is provided by the leaky-wave nature of the device, which avoids typical problems of demodulation and detection/ranging errors and possible destruction of the receiver. Another advantage of this duplexer/diplexer is the possibility to tune the operation frequency by the applied magnetic bias field, whereas such tuning is prevented both by the antenna and by the circulator in conventional designs. The fabricated prototype exhibits a gain of 2.3 dBi with isolation of more than 15 dB at all ports. The diplexing frequency range reaches 400 MHz.