Large Frequency Ratio Vivaldi Antenna System With Low-Frequency Gain Enhancement Utilizing Dual-Function Taper Slot

A single-layered dual-frequency Vivaldi antenna system with a large frequency ratio covering microwave and millimeter-wave bands is presented in this communication. The system consists of a Vivaldi antenna with enhanced gain and two four-element Vivaldi antenna arrays, which cover the frequency ranges of 3.5–7 GHz and 26.5–40 GHz, respectively. The antenna is designed with dual-function tapered slots etched on the microwave-band Vivaldi aperture, which acts as a radiator for the millimeter-waveband, and as a parasitic structure for gain enhancement in the microwave band. Each array element is excited by the corresponding port separately, so that the beam steering can be achieved in the $E$ -plane. For verification, a prototype of the proposed antenna is fabricated, and relevant measurements are obtained. Its impedance matching and radiation performance are tested in both bands, and the measured results are in reasonable agreement with the simulated ones. The measured isolation between antennas operating in different bands all exceeds 15 dB without any decoupling structures, demonstrating good characteristics.