Printable Planar Dielectric Antennas

Abstract

Thick film screen-printing technology is employed to introduce planar dielectric antennas. The micron-size-thick film is made from high-permittivity dielectric paste, which is printed on a low-loss low-permittivity microwave substrate to operate as a magnetic wall boundary. A simplified theoretical model is developed to analyze the antenna structure. The accuracy of this model is evaluated by the results of a commercial three-dimensional (3-D) electromagnetic field solver. The model works well with less than 5% deviation from time-consuming simulations, providing the permittivity contrast between the film and substrate is kept high (e.g., > 30). The impact of dielectric loss of the film in antenna performance is significantly less than that of the substrate, allowing medium-loss films (e.g., ε"= 3) results in highly efficient antennas with over 95% radiation efficiency. A prototype was made using screen printing and experimentally characterized at Ku-band. The experimental results confirm the theoretical achievements. The measured -10 dB impedance bandwidth of the printable planar dielectric antenna having dimensions of 0.2 λ0× 0.2 λ0 is over 10% with a measured gain ranging from 4.5 to 5.5 dBi. Broadside radiation patterns with cross polarization levels of lower than -20 dB are achieved. This process is compatible with low-temperature cofired ceramic (LTCC) technology where similar idea can be applied to other passive microwave components.