| With the continuous development of modern communication systems in recent years, compact microwave components are required. Antenna is a very important part in a wireless communication system. However, in some wireless devices, especially in some portable ends, the space left for engineers to design an antenna is very limited, and even getting smaller and smaller.Metamaterial is a composite or structured material that exhibits properties not found in naturally occurring materials or compounds, and can be realized by applying metal cell units with certain structures into conventional mediums. After many years of study and research, it is found that the application of metamaterials can efficiently reduce the size of microstrip patch antennas.Firstly, on the basis of theoretical analysis, an ideal metamaterial whose permeability follows dispersion law is loaded in the substrate of a patch antenna. After simulation, it is found that the antenna could resonate at a very low frequency and its electrical properties were observed. Secondly, since the effective permeability of a substrate loaded with SR or MSRR inclusions conforms to the Drude dispersion law when a magnetic field goes through the inclusions, and their resonant frequencies are low because of their multiple-ring-structures. Patch antennas with these kinds of substrates were simulated and the effects of different values of the geometry parameters were analysed. The parallel MSRR structure is proposed because its structure and properties are very similar to MSRR. Antenna with this inclusions was also simulated and analysed. Comparison between these three strutures was conducted and it is found that the PMSRR has the lowest resonant frequency. Finally, a 433MHz patch antenna loaded with SR inclusions and a 800MHz RFID patch antenna loaded with Parallel MSRR were realized . The research shows that the sizes of these two patches are almost equal to 0.019λ0 and 0.037λ0 respectively, whereλ0 is the wavelength in free space. |
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