Research And Design Of Microstrip Multifunction Filter

Recently, with the rapid development of wireless communication system, low cost, high performance, and miniaturization have become more and more important in the design of RF front-end circuit. In order to realize these characteristics simultaneously, many new types of microwave passive components which have multi-function performance, such as multi-function filter, have been attracted more and more attention at present.Based on the background above, in this paper, we mainly focus on the microwave passive component in the RF front-end. Firstly, we proposed various high performance and miniaturization design methods for multi-function microwave passive components. Then, many novel multi-function microwave filters are designed based on the proposed design methods. Specifically, the main contributions of this paper can be summarized as follows.(1) Theory and background. The background, current status, and latest development of the miniaturized microwave passive component in the RF front-end are firstly reviewed in this paper. Besides, some related concepts are introduced, including microwave transmission theory, microstrip line theory, and microwave resonator theory.(2) Design of balun bandpass filter (BPF). In this paper, three balun BPFs have been designed based on the resonant properties of the multi-mode resonator and the electric distribution of the open-circuited transmission line. Comparing with the related works, we can conclude that the designed balun BPFs possess small size, high performance, low insertion loss, and simple structure, which means they can be widely used in the modern wireless communication system.(3) Design of filtering power divider. In this paper, by utilizing the design concept of microwave power divider and the resonant property of the multi-mode resonator, a high selectivity dual-mode dual-band filtering power divider is proposed. Specifically, the odd-and even-mode analysis method is firstly used to characterize the employed multi-mode resonator. Then, by employing four multi-mode resonators and proper coupling topology, a high performance dual-mode dual-band filtering power divider is designed. Both the simulated and measured results indicate that the proposed filtering power divider has both properties of high selectivity and good isolation.(4) Design of tunable lowpass filter. In order to meet the latest requirements in the RF front-end, a microstrip miniaturized tunable lowpass filter with ultra-wide stopband and large tuning range is presented in this paper. Comparing with the related works in the open public, we can conclude that the proposed tunable LPF will have a wide application prospect due to its good performance.