Effect of Vivaldi element pattern on The Uniform Linear Array Pattern

Abstract

This paper presents about the effect of Vivaldi element pattern on the Uniform Linear Array pattern. Vivaldi antenna can operate over wide bandwidth. Geometry of the radiating element influences element radiation pattern especially for frequency far from the center frequency. In this paper, we reported coplanar Vivaldi antenna with dimension 60×60 mm on FR4 substrate with permittivity 4.7. The antenna has differents element pattern at 2 GHz, 3 GHz and 4 GHz. It is shown that bad radiation pattern in certain frequency in broadband antenna can effects on the total array pattern. Differents element pattern, spacing and number of elements resulted different array pattern. We simulated variation 5 mm and 15 mm spacing between adjacent sides of Vivaldi elements and variation 3 and 10 number of elements in each frequency. From simulated resulted shows that the total array pattern has higher back lobe level than main lobe level for N=5, d=0.433λ at 2 GHz due to its elements pattern performance. Gain of the main lobe level is obtained as 10.81 dB at 3 GHz, N=5, d= 0.65λ. Gain of the array pattern increased and HPBW decreased with increasing number of elements. From simulated result, it reveals that good performance of element pattern and total array pattern is achieved at 3 GHz, 4 GHz and 2 GHz respectively. Increasing operating frequency will affect its sidelobe performance due to different spacing between elements relative to certain wavelength. Although broadband antenna has return loss below −10 dB in all band frequency, it must be better to know element pattern in each operating frequency. It can avoid bad performance of total array pattern in certain frequency. Simulation by using multiplication element pattern with array factor can reduce computation time compared with full wave simulation. But it does not consider mutual coupling effect.