Monolithic 3-D Printing of an Integrated Marchand Balun With a Dipole Antenna

We present a fast 3-D printing prototyping method for integrated antennas having internal features. Commercially available printers with soluble supports and airbrushing are utilized for fabrication and metal coating of antenna structures. This method includes modifications of the antenna geometry while preserving its integrity and performance. To get access to the interior of the design, windows are cut out of the antenna walls where the power flow shows local minima. These windows facilitate airbrushing the internal features of the antenna. As a proof of concept, we adopt a short-circuit variation of the Marchand balun whose attachment to the antenna wall facilitates its 3-D printing fabrication and rejects the common-mode resonance. The ground plane, balun, and dipole were monolithically fabricated in a single run. We then used copper deposition by airbrushing, which forms a sufficiently thick layer on the whole structure. The fabricated antenna shows a very good match to simulation results. A wideband resonance from 2.12 to 3.95 GHz is measured. The radiation pattern of the antenna remains stable across the frequency range with cross-polarization isolation higher than 30 dB. The measured gain of the antenna is 5.9 dB at 3 GHz. The fabrication techniques, discussed in this study, show promise for the future fabrication of 3-D printed integrated antennas with limited access to their interior features.