Analysis and Design of Broadband MSA with Hybrid Coupled and Parasitic Patches

Broadband microstrip antennas are realized using multi resonator techniques such as gap coupled techniques in which fed patch is coupled to parasitic patches, or slot cut inside the same. Here wider bandwidth is achieved by reducing the frequency of higher order modes by increasing the surface current path length and bringing the higher order mode frequency closer to the frequency of fundamental mode of the antenna. The design of a RMSA with a directly coupled and two parasitic patches is reported that yields a bandwidth which is six times of that of the rectangular MSA. This paper presents detailed analysis to highlight upon functioning of broadband microstrip antenna with respect to patch resonant modes. The wider bandwidth is achieved due to the coupling between TM
₀₂
mode of directly coupled patch, TM
₀₁
mode of two parasitic patches and a composite TM
₂₁
mode of fed patch. Design procedure at other frequencies is presented which yields a bandwidth more than 6% with broadside pattern.