This article presents a magneto-dielectric material implementation in substrates for microstrip rectangular patch antennas. The GdIGxYIG1-x compounds originated from ferrite garnets are used. The antennas are designed for 1.8 GHz applications and are simulated using Computer Simulation Technology (CST) software. The results are compared with simulations of FR-4 substrate antennas. The substrates used present different dielectric properties, which yield different antenna design sizes and |S11| parameters. All antennas resonate near the desired frequency with |S11| below –10 dB, presenting variations in bandwidth between them. The FR-4 antenna presented |S11| of -12.85 dB, while the antennas with GdIGxYIG1-x substrate presented values between -30.8 dB and -41.17 dB.