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In this paper we did a study of logic gates obtained in the operation of a three-core non linear directional coupler (TNLDC) and an asymmetric two-core coupler (DNLDC) operating in the CW regime (the laser signals have the same wavelength). The symmetric three-core coupler (TNLDC), with their cores identical, in a planar arrangement, was studied using a control pulse applied to the first core. The second structure is an asymmetric twocore coupler (DNLDC). Looking at the transmission characteristics of the device, through the direct and cross channel, we did a study of the extinction ratio (Xratio) of these devices. For both devices we did a numerical investigation with the objective to implement logic gates. The DNLDC supplied AND, OR and XOR gates while the TNLDC supplied AND, NAND, OR, XOR and NOT gates. In comparing the performance of both switches operating as logic gates (DNLDC and TNLDC) we define, for the first time, a figure-of-merit of the logic gates (FOMELG). In this criteria the FOMELG is defined as a function of the extinction ratio of the gate outputs. Comparing the same gates of the three and two-core NLDC we observe that the logical gates of the three-core TNLDC present a better performance than the one of the two-core DNLDC considering the figure of merit FOMELG, besides the fact that is simpler to fabricate a symmetrical coupler (with identical cores) comparing with an asymmetric coupler. We believe that the use of this figure of merit will be useful in the study of the performance of logic gates to be used in communication systems.

The authors report a study on microwave properties of a ferrimagnetic ceramic composite (Gd 3 Fe 5 O 12 )GdIG X -(Y 3 Fe 5 O 12 )YIG 12X . The magnetic and dielectric measurements at microwave frequency were made through the Hakki -Coleman's procedure and through the excitation of a cylindrical ferrite resonator antenna (FRA). The hysteresis loops of the GdIG X YIG 12X ferrimagnetic composite were obtained. The numerical simulation study was performed using Ansoft's High Frequency Structure Simulator (HFSS TM ) software. The agreement between the experimental data and the simulated results is very good. These results demonstrated that, by varying the material composition of the resonator, ferrimagnetic composite GdIG X YIG 12X could operate as a magneto-dielectric antenna with bandwidth in the range of 7.5 -11% and in the frequency range of 4.4 -5.3 GHz. Additionally, all FRAs presented a low negative value of t f , which indicates suitability for microwave applications such as mobile communication systems or satellite broadcast systems.

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