This paper presents a new method and structure to suppress unwanted interference in conventional Global Positioning System (GPS) applications. In contrast to traditional antennas that usually utilize high-impedance structures with limited enhancement or the arrays that employ null-steering techniques at the expense of increasing complexity and cost, here, a single-element circularly polarized truncated microstrip patch antenna is loaded by a magneto-dielectric metamaterial (MTM). The antenna constitutes a simple microstrip patch radially loaded by a magneto-dielectric MTM cover. The simulations show that thanks to the magnetic behavior of the capacitively-loaded loop (CLL), the CLL is an effective structure to suppress the unwanted incident plane wave up to 30 dB. The proposed antenna has a cylindrical shape with a radius and height of 0.29λ0, while the gain and efficiency of 6.8 dBi and 89% are obtained.