Research On Microwave And Millimeter Wave Integrated Passive Circuits

With the development of the wireless communication system, the requirements for miniaturization and high performance of the passive circuits have attracted more and more attention. This thesis focuses on the study of planar passive circuits in microwave front-end. The advent of semi-conductor technology benefits the miniaturization of active devices. However, the chanllenge of the miniaturization and high performance of the passive circuits still exists.As one of the most important passive components in the wireless communication system, filter is also required to be miniaturized while maintaining high performance. This dissertation proposes several bandpass filters including dual-band bandpass filter, wide-stopband bandpass filter, and differential filter.Firstly a specific U shape coupled-line resonator based bandpass filter is analyzed to demonstrate its mechanism of the generation of transmission characteristics and transmission zeros. On this basis, combined with the stepped impedance resonator, a dual-band bandpass filter is implemented.Based on the same basic coupled-line resonator but with different feeding position, a bandpass filter with wide upper stopband is designed. The I/O port is placed at the position which divides the coupled-line with the ratio of 1:2, then with theoretical and simulation analysis, it’s found that the first spurious passband appears at 5 times the fundamental frequency, therefore the upper stopband is expanded. Based on the above approach, bandpass filters with compact size and improved upper-stopband are proposed.Finally, a common-mode suppression differential bandpass filter with wide upper-stopband is realized based on the same method. The related work has been published in IET Electronics Letters.Secondly the dissertation researches on the miniaturization and harmonic suppression of the branch-line coupler. With the quarter-wavelength transmission line in the traditional branch-line coupler replaced by the stub-loaded transmission line, the miniaturization is achieved, additionally with the transmission zero introduced by the open circuited stub, the harmonic is suppressed. Next with quarter-wavelength open-circuited parallel coupled-line adopted at each port, wideband impedance matching is realized and then a compact wideband branch-line coupler with harmonic suppression is presented.The chapter four proposes rat race coupler and wilkinson power divider with miniaturization and harmonic suppression. With the transmission line units in the traditional rat race coupler and wilkinson power divider replaced by the corresponding stub-loaded transmission line, the miniaturization and harmonic suppression have been realized. The related work has been published in IEEE Microwave and Wireless Components Letters.Analysis approaches for a class of passive circuits are proposed in the dissertation, and based on these approaches, a series of passive components with high performances and miniaturization are demonstrated to verify the analysis. The passive components presented in this dissertation is very promising for engineering application to elevate the performance of the whole wireless communication system.