Novel Coupling Mechanism And Resonators (Transmission Lines)for RF Passive Circuits:Research And Application

With the development of modern wireless communication technology, the performance and size of the mobile base station and terminal products are becoming more demanding. Under this situation, high performance, miniaturization and low cost are a trend for RF device design. Al-though mush research has been conducted, it is still challenging to achieve this characteristics in some applications. In this paper, we focus on the key technologies of the RF passive devices design, such as coupling mechanism, novel resonator/transimission line structure and so on. Meanwhile, some samples are designed to verify the design methodology. The contents are as follows:1. Base on the voltage-wave function theory, the coupling mechanism for RF planar microstrip bandpass filter design is investigated. Upon the coupling analysis between resonator and resonator, the coupling mechanism between resonator and feeding line is also derived. With this analysis results, a class of novel microstrip bandpass filters are designed with improved rejection band.2. Furthermore, a novel capacitor-based coupling mechanism is studied. with the benefit of capacitor-based coupling mechanism, the length of conventional coupling structure is shorted to a point, and the freedom of filter design is greatly increased. Based on this novel coupling mechanism, the functions of miniaturization and harmonic-suppression of microstrip bandpass filters can be easily achieved. Besides, in dual-band filter design, the coupling coefficients of the two passbands can be controlled independently due to the capacitor-based coupling mechanism.3. In addition to the coupling mechanism, a new center-coupled resonator is proposed. Espe-cially for the capacitor-loaded center-coupled resonator, the analysis results show that the perfor-mance of the two passbands can be adjusted independently for dual-band filter applications. Also, some prototypes are designed to verify the design theory.4. Combined with the DSPSL inserted a common conducted plane, a novel through ground via (TGV) is studied. With the odd-and even-mode analysis method, the characteristic of TGV is researched. Furthermore, some RF passive devices such as power dividers and filters are designed with the TGV structure. 5. The integrated design of power divider and filter is investigated. A effective solution is proposed to improve the passband isolation of high-order filtering power divider. Meanwhile, a new filtering power divider with external isolation resistors is designed for high-power capacity application.6. Finally, a circularly-polarized phased-array antenna with large angle and wide beam charac-teristics is designed. A wider circular polarization beam is obtained compared with the traditional circularly-polarized phased-array antenna. At the same time, a good results of beamforming and shaping is achieved. The proposed antenna is a good choice for the circularly-polarized phased-array antenna applications.