Dielectric Resonator Antennas by Low Cost 3D Printing: Characterisitic Mode Approach

3D printing is very flexible and economic for fabricating dielectric resonant antennas (DRAs). In this paper, characteristic mode approach is presented for analyzing DRAs. It can handle different shapes and materials for DRAs owing to its full-wave nature. Spherical shell DRAs are analyzed as an example. It is shown that the DRAs made of low permittivity PLA material do not achieve the resonance when its diameter equals to a half wavelength. Usage of higher permittivity material like BaTiO3/ABS polymer composites can reduce the resonant frequency as expected. Therefore, it is not efficient to excite those modes as traditional DRA design. Instead, we need to co-design the DRA and its feeding structures. A conformal feed is used to excite a thin spherical shell DRA with PLA material, and it is seen that the antenna is resonant at 480 MHz with a bandwidth of 50 MHz. Total length of the feed is only 0.2176 times of the wavelength at 480 MHz, thus it can be considered as a DRA instead of a dielectric loaded antenna.