Broadband Proximity-Fed Modified Rectangular Microstrip Antennas

The bandwidth of a microstrip antenna is increased by using a thicker and lower-dielectric-constant substrate, or by using multi-resonator gap-coupled and stacked configurations, or by cutting a resonant slot inside the patch. However, with all of these methods, the bandwidth of the antenna is limited by the probe´s inductance for substrate thicknesses greater than 0.06λ₀ to 0.07λ₀. For substrate thicknesses larger than 0.07λ₀, the bandwidth of the antenna can be increased by using a proximity-feeding method. In this paper, by using a combination of the proximity feeding technique and a thicker substrate, various broadband configurations of gap-coupled rectangular microstrip antennas, E-shaped and half-E-shaped microstrip antennas, and gap-coupled half-E-shaped microstrip antennas are proposed. All of these configurations give bandwidths in excess of 350 MHz (>;35% ), with gains of more than 7 dBi, in the 800 to 1200 MHz frequency band, with a broadside radiation pattern.