Multi- and Wideband Circularly Polarized Gap-Coupled Stack Modified Triangular Microstrip Antennas

Modified design of triangular microstrip antenna and its electromagnetically coupled stacked variation are discussed which yields circularly polarized response with axial ratio bandwidth of larger than 5%. Further, its stacked and gap-coupled designs for realizing multiband and wideband circularly polarized response are proposed. Optimum performance in terms of axial ratio bandwidth and gain is obtained for x-gap-coupled parasitic patches. For equal dimensions of the parasitic gap-coupled patches, dual-band response with axial ratio bandwidth of 148 MHz (11.71%) and 45 MHz (2.84%) is obtained. Similar design with smaller dimensions of the gap-coupled patches gives broadband circularly polarized response with AR BW of 256 MHz (19%). Gap-coupled design with patches along x- and y-axis of the stacked patch gives dual-band or triple-band or four-band frequency response by appropriately choosing the angular displacement between gap-coupled stacked patches. In the entire design, antenna shows broadside gain of more than 5 dBi across impedance bandwidth. Simulated and measured results have been matched in all the proposed multiband circularly polarized designs.