High Gain Antipodal Vivaldi Antenna With Novel V-Shaped Air-Slot

By introducing a V-shaped air slot in antenna substrate, the peak gain can be improved significantly for traditional Vivaldi antennas without size enlargement and additional components. The air slot is conformal to the radiating conductors of the target Vivaldi antenna, and can force the electromagnetic wave to propagate within the central dielectric part between the antenna's opening slot, by decreasing the effective dielectric permittivity of the regions along the radiating conductors. As a result, the wave distributes more evenly within the radiating aperture comparing with the traditional designs, especially at high frequencies, hence the peak gain can be enhanced. In addition, the removal of antenna back substrate is evaluated on radiation characteristics, which can further improve antenna gain and front-to-back ratio. For verification, three antennas within operating frequency band from 0.8 to 6.0 GHz are designed with the same dimensions (220 mm x 256 mm) but different configurations. The simulations show that the peak gain increases from 2.0 to 12.0 dBi gradually for the air slot loaded antenna. The gain increment is about 4-6 dB from 4.0 to 6.0 GHz comparing with the one without air slot. A sample antenna with both air slot and removal of back substrate is fabricated and measured. The measured reflection is better than -10 dB from 0.8 to 6.0 GHz, and the measured gains at (0 degrees,0 degrees) direction are from 2.3 to 11.0 dBi. The antenna patterns at high-band shows that the main lobe in E-Plane is narrowed successfully after introducing the V-shaped air slot. The experimental data agree well with the prediction with in-band radiation efficiency better than 65%.