No abstract

No abstract

No abstract

Folded spherical helix (FSH) antennas using thin and wide copper strips instead of thick wires as a means of reducing the electrical size of ka is designed. It is found that FSH antennas made of copper strips show comparable radiation properties to FSH antennas made of thick wires. Furthermore, such designs can achieve even smaller size down to ka of 0.11 while keeping the radiation quality factors approaching the lower physical bound. An FSH antenna made of copper strips with ka of 0.21 is fabricated as a prototype using 3D printing technology. The measured resonance occurs at 307 MHz with the radiation efficiency of about 90%, verifying the simulated results and the proposed method of utilising copper strips in designing extremely small yet highly efficient volumetric folded helix antennas.

A 3D printed, low-profile, electrically small antenna with a quasi-isotropic radiation pattern is presented herein. It is composed of an electric meandered dipole antenna, and the extended arcs from the meander line mimicking the current flow of the loop antenna. A quasi-isotropic radiation pattern is achieved from the total current flow over the proposed structure. Modern stereolithographic 3D printing and nano-polycrystalline copper coating technologies are used to build a prototype. The measured antenna exhibits a good uniformity in terms of the radiation pattern with a maximum gain deviation of 4.5 dB at 959 MHz and a radiation efficiency of 81 %, close to the computed expectations. The electrical size of the antenna ka is 0.48, and its height is λ 0 /82.32.INDEX TERMS 3D printing, isotropic radiation pattern, electrically small antennas, radiation pattern synthesis.