Study Of The Key Technology About Six-port Receiver

Six-port circuit, which consists of one power divider and three quadrature hybrid bridges, is an important passive network. It was initially applied to the systems of microwave measurement and network analysis. Six-port circuit which can be achieved only by microstrip line is composed by passive components, thus its structure is greatly simple and its cost is very low. These advantages make it be the focus and its application is expanded to the fields of radar and communication.This thesis aims to design one direct conversion direction-finding receiver front-end. The application in phase measurement is studied, and the works include:First of all, the principle and the recent development of six-port circuit and the direct conversion receiver front-end are presented in this thesis. Study on the structure of six-port circuit is done, and three wideband power dividers, two wideband quadrature couplers and one six-port circuit are designed in this thesis. Besides, advantages and disadvantages of the three power dividers and the two couplers are summarized.Secondly, wideband LNA(low noise amplifier) is researched according to the requirement of six-port direct conversion receiver front-end. And one LNA for S band is designed in this thesis.Thirdly, the influence of non-ideal factors on phase detection is analyzed. one direct conversion direction-finding receiver front-end based on six-port circuit is designed according to the requirement of project. Structure diagram of the receiver front-end is exhibited in the content. In consideration of the boundary dimension and the EMC, the idea of layered structure is employed in the design of six-port direct conversion receiver front-end. According to the actual circuit structure, this receiver system mainly include: matrix switch, limiting amplifier, attenuator-filter circuit, filter-splitter circuit, power-detecting circuit, six-port phase-detecting circuit, as well as differential operational amplifier circuit.Finally, the issues such as gain being not flat, self-excitation are analyzed, and the solutions are proposed in this thesis. In addition, the data about the designing receiver is also analyzed and concluded. The experimental results show that the proposed direct conversion receiver front-end meets the user’s design requirements.