Folded microstrip antenna with isotropic radiation pattern

In contrast to existing antennas with polarization and directional characteristics, we propose a novel isotropic antenna that provides equivalent vertical and horizontal polarization in all directions. The final design was guided by simulations, with the performance characteristics of the fabricated antenna verified experimentally. In the proposed antenna, two lambda/4 folded microstrip antennas were integrated into one antenna in a "+" shape to generate the isotropic radiation pattern, with the input impedance matched to the feeding position. The resonant frequency, horizontal width, radiation pattern, and axis ratio were adjusted by changing the length of the microstrip line. Both simulations and experiments confirmed that the radiation patterns of vertical and horizontal polarization on each plane show the characteristics of an isotropic antenna with nondirectional radiation pattern.