Research Of X-band Butler Matrix

With the rapid development of communication technology, multi-beam antenna which achieved relatively simple and pointed accurately plays an increasingly impor-tant role in radar and communication systems. The core of multi-beam antenna is beam forming network. As one of the two multi-beam antenna feed network circuit, Butler matrix is lossless gain in the ideal case. Because of its lossless structure, making flex-ible and wide bandwidth, Butler matrix has great application prospects. The radar and communication systems of X-band are widely used, but the research on the X-band But-ler matrix is rare. This article based on X-band radar communication systems describes two aspects, which are broadband X-band Butler matrix and miniaturized X-band Butler matrix.Butler matrix is composed of3dB directional coupler and45°phase shifter. The bandwidth of butler matrix is determined by the characteristics of directional couplers and phase shifters. In the implementation of broadband butler matrix, we use multi-section rectangular slot-coupled structure to achieve broadband3dB directional cou-pler. This structure consists of two vertical parallel transmission lines and slot structure in the intermediate ground. This structure can obtain broadside coupling and the strong coupling. Based on this structure, multi-section can expand the bandwidth of directional coupler. A rectangular slot replaces the traditional oval to make the process simpler. Rectangular slot structure is also used in broadband45°phase shifter. Like Schiff man phase shifter, this45°phase shifter requires a reference transmission line for compari-son. In the single-layer structure, the crossover design complicated. Due to multi-layer of the structure, different metal layer greatly simplifies this problem without additional device.In the X-band Butler matrix miniaturization, based on IPD (Integrated Passive De-vice) technology, lumped parameter is used to achieve the miniaturization matrix. IPD technology is copper process which based on high resistance silicon. First, Butler ma-trix schematic consists of lumped elements, arms of conventional branch line coupler are equivalent to the different network, which constituting the3dB directional coupler lumped. Phase shifters also use the network to achieve a45°phase shift. Since of the multi-layered structure of IPD technology, a different metal layers can solve crossover. Because of mutual inductance between the lumped elements and parasitic effects of lumped element in the layout, the series inductance and shunt capacitance are added to debug to get the final layout.During the study, HFSS and ADS are used to simulate the Butler matrix. Demon- strate the effectiveness of those design methods through simulation and measurement.