Applied To The Butler Matrix Of The Multi-beam Array Antenna

With the rapid development of modern communication, the technology of multi-beam antennas is widely used in this area. As an analog beam-forming network, Butler matrix has advantages such as lossless gain and simple structure. Therefore, it is of great value in multi-beam antennas. In recent years, the research of Butler matrix mainly focus on miniaturization, broadband and low transmission loss, and in this thesis wideband Butler matrix is mainly discussed.Firstly, the theory of Butler matrix is briefly described in this thesis, and a simple overview on the domestic and international research about the realization of wideband Butler matrix is made followed by, simultaneously a theoretical analysis about the components of a Butler matrix is briefly given.Secondly, a microstrip wideband Butler matrix with a center frequency of 5 GHz and relative bandwidth of 20% is proposed. Three-branch line couplers with lumped and distributed elements are adopted to reduce the size and multi-U-shaped coupled-line Schiffman phase shifters are designed to get good transmission and phase performances.Thirdly, a suspended strip-line Butler matrix with a center frequency of 2 GHz and relative bandwidth of 50% is designed. Broadside-coupled 3dB directional couplers use compensating shunt capacitances to get high isolation and good direction. The cross occurs when the two lines are on the opposite sides of the suspended substrate and some appropriate methods are adopted to reduce the coupling. The wideband phase shifters with simple structure and good performances are based on the basic theory of Schiffman phase shifter.The Butler matrices are fabricated and measured, and good agreements are found between the simulated and measured results, which validate the feasibility of these structures. At the end, the total work of this paper is summarized, and some questions which need improvement and further study is also proposed.