Proximity Coupled Microstrip Patch Antenna With Reduced Harmonic Radiation

The purpose of this work is to propose a new method to suppress the harmonic radiation from a microstrip patch antenna with proximity coupled feeding line implemented in a multilayer substrate. The goal of the design is the suppression of the resonances at the 2nd and 3rd harmonic frequencies to reduce spurious radiation due to the corresponding patch modes to avoid the radiation of harmonic signals generated by non-linear devices at the amplifying stage. The study shows the possibility of controlling the second harmonic resonance matching by varying the length of the feeding line. On the other hand, the suppression of the third harmonic is achieved by using a compact resonator. This resonator consists of a printed metallization with a via connected to the ground plane (mushroom type) in a multilayer configuration. Comparing with conventional electromagnetically coupled patch antenna, the radiated power of the proposed antenna at the 2nd and 3rd harmonic frequencies is reduced by 14 dB and 8 dB, respectively.