Electrically small, copper strip made folded spherical helix antennas realized by 3D printing technology

The radiation characteristics of electrically small, copper strip made folded spherical helix antennas are studied. It is found that the electrical size of a volumetric wire helix antenna can be further miniaturized when thin and wide copper strips replace the thick wires. It is shown that the proposed antenna designs can approach the lower physical bound for a radiation quality factor Q with electrical size ka less than 0.2. A prototype of the copper strip made folded spherical helix antenna with ka of 0.21 is fabricated using 3D printing and silver painting processes and verified experimentally.