Proposta de uma antena Vivaldi antipodal para operação em faixa larga

Abstract

This paper presents a study on printed Vivaldi antennas. It started from the study of two models of this antenna, where it chooses the most appropriate for the job. Through computer simulations verified the operation of behavior due to the reflection coefficient for this antenna. The results of the first simulation showed an operation at multiple resonant frequencies, narrow band around a center value. To extend the operating range, were make change at the geometry of this antenna, where they were inserted rectangular cuts in the outer parts of the electrodes to form resonant cavities and beveled at the ends of external exponential curves. These changes were intended to improve the distribution of current in the electrodes and perform the antenna impedance matching with the transmission line within a wide frequency range. The results were significant in relation to the antenna in its original form, but have not yet had achieved the expected behavior of the reflection coefficient within the frequency range for analysis. So it was remodeling some sharp corners present on the antenna structure to eliminate the accumulation of charges and currents that generated one parasitic reactance in the antenna input. In such remodeling was made circular shapes to these points where it was tested several radius values until to find satisfactory values for the reflection coefficient curve. Finally, was created a prototype of the best antenna resulting from simulations for to make the measurements. The antenna measurements resulted in reflection coefficient good for operate enter 2.3GHZ to 20GHZ. The project was developed in a polytetrafluoroethylene substrate (PTFE), Diclad 880 model, Arlon. The results were consistent with the demands of different radio systems in the microwave range.