| Various reflector antennas consisting of an air-lifted monopole, a reflector, and a director have been demonstrated on a ground plane for 2.4 GHz in-plane wireless communication. A monopole with a height of 30 mm and a pole diameter of 0.5 mm is fed by conductor backed coplanar waveguide (CBCPW) for easy connectivity with other on-board components and simple implementation not requiring via connection through the substrate. The coplanar waveguide has been patterned using a prototyping milling machine and/or photolithography followed by copper etching. A single pillar reflector, a flat wall reflector, a parabolic wall reflector, and a pillar array-type parabolic wall reflector have been successfully designed, fabricated, and characterized. Reflector antennas show better directivity performance compared to an omnidirectional monopole antenna. Among the reflector antennas, both the solid parabolic wall reflector and the 5 pillar array reflector antennas with a director show a same directivity of 7.7 dBi in simulation while the solid and the 5 pillar array ones show a measured antenna gain of 4.8 and 3.5 dB respectively. While their overall performance is comparable, the pillar array type reflector has a less reflector weight compared to the solid one by approximately 70%. With an additional pillar for a director in the opposite side of the apex 0.2 wavelength from the monopole, an enhanced directivity and reduced backlobe have been obtained. The implemented air-lifted antennas show a broad 10dB bandwidth of 9∼18% at a center frequency of 2.4 GHz. This air-lifted reflector architecture would be scaled up to much higher frequency such as millimeter wave applications requiring much smaller profile and footprint. |
