Electrical Filter Coupling Ring Resonator Based

This paper is mainly about research and design of multifunctional electric coupled resonator bandpass filter. Based on the analysis of the ring resonator, different functions of bandpass filters using open-loop coupled resonators are designed, including microwave balun filters and differential filters.Firstly, the ring resonator theory is analyzed and its applications in the microstrip filters are introduced. Begin with the most simple open-loop coupled resonator filter,0°feed structure and non-0°feed structure are analyzed by using transmission matrices.On the basis of previous analysis a three-port balun filter is designed, the balun filter only consists of two open-loop resonators. This filter is electrically coupled and it has simple structure which is very easy to design and fabricated. At the same time, it has good balanced amplitude and phase outputs. To optimize the filter characteristics, another capacitive load balun filter is designed.0°feed structure and the coupling end load capacitance produced two extra transmission zeros, which improve the filter’s performance greatly. Combined above theoretical analysis and physical verification, a fourth-order filter balun is designed. Compared to the previous two second-order balun filters, its structure realizes simultaneous size reduction and superior response suppression performance in bandpass filtering meanwhile with good differential performance of the balun. Balun filters designed in this paper are applicable to the Bluetooth frequency filters and other communication systems.Differential bandpass filters (BPFs) have been one of the most essential components in the high speed wireless communication systems due to their high immunity to the environmental noise and low electromagnetic interference (EMI) to meet the prompt need in the development of balanced radio frequency (RF) front-end. In this paper, a differential BPF is proposed with common-mode suppression. It consists of two open-loop resonators which are coupled at their ends. It has good differential response and common-mode suppression. Moreover, by etching DGS on the ground or loading loaded T-shaped resonators, improved common-mode suppression is achieved. Theory analysis, simulation, and measurement show good agreement with each other.