A Study On The Key Techniques To Passive Components In Wireless Communication Systems

The key technologies of passive components in wireless communication systems are studied in this thesis. Based on the optimization algorithms, a method of determining the filter order and the transmission zero locations is proposed. Besides, several novel types of dual-mode band pass filter, multi-mode band pass filter, filtering Wilkinson power divider, multilayer substrate integrated waveguide(SIW) power divider, SIW filtering power divider, and microstrip-to-waveguide transition are presented in this thesis. The main contents of this thesis are detailed as follows:Firstly, a new method of determining the filter order and the locations of transmission zeros is proposed based on the optimization algorithms. And the method is applied to the self-equalization filter by improving the objective functions. Several example applications are given to validate the effectivity of this method. The results of the proposed method are better than those of the references.Secondly, the equivalent circuits of the short stubs loaded and open stubs loaded are analyzed, respectively. The distributions of transmission zeros of this classic of filters are summarized. A four-mode band-pass filter and a dual-mode dual-band filter are designed based on the short stubs loaded resonator. The out of band transmission characteristics are improved by the transmission zero which is generated by the coupling between source and load. Moreover, a new type of open stub loaded dual-mode resonator is proposed, and the resonator has the advantages of varied resonant frequency without increasing the external dimensions of the resonator. Thus, a dual-mode bandpass filter is designed using the proposed resonator. By improving the loading method of open stub loading, two types of triple-mode resonator are obtained. Eventually, two types of tri-mode band-pass filter are designed based on the triple-mode resonator. All the designed filters have the advantages of compact size, wide band, and better out-of-band rejection.Thirdly, by replacing the quarter wavelength impedance transformers of Wilkinson power dividers with band-pass filters, a filtering Wilkinson power divider can be achieved. Based on the presented theory, a dual-mode filtering power divder and tri-mode filtering power divider are designed. Hence, the correctness of the proposed designing method is verified. The filtering power dividers have the characteristics of power dividers and filters. The size of wireless system can be reduced effectively by employing the filtering power divider.Fourthly, a novel multilayer four-way out-of-phase power divider based on substrate integrated waveguide technology is presented in this thesis. The proposed power divider has the advantages of small size and simple designing method. Two of the outputs are in phase, while the other two are out of phase. The proposed power divder can be applied to power combiner or antenna feed network designing. And it also can be fabricated using the LTCC technology.Fifthly, filtering SIW power is studied. The filtering SIW power divider is binding of the high-pass characteristic of SIW and the low-pass characteristic of DGS. The lower stop-band frequency can be adjusted by changing equivalent width of SIW, while the upper stop-band frequency can be adjusted by changing the size of DGS. So the filtering bandwidth can be easily adjusted according to the need of project. The proposed filtering power divider has the advantages of small size and easy to be integrated with planar circuit.Finally, based on the coaxial probe coupling, a Ka band microstrip-to-waveguide transition structure is proposed and the equivalent circuit of the transition structure is extracted. Results of the circuit simulation and the field simulation are given to verify the validity of the equivalent circuit. Two types of microstrip-to-waveguide transition, in which the waveguide and the microstrip are parellel or vertical, are designed and fabricated. The proposed structure has the advantages of compact size, wide band, good sealing, rotable of the waveguide output port around the coaxial probes, different polarization directions which meets the need of engineering application.