Research On Advanced Synthesis And Design Methods For The Wideband Microwave Filters And Power Dividers

As the modern wireless communication system is developing towards the high capacity,high date rate,compact size and high integration,higher performance is required for the microwave passive components in the systems.As one of the key components in the wireless communication systems,filters are faced with new challenges and applications.In order to realize the intelligent and automatic circuit design and tuning,a more advanced synthesis method for filters should be proposed.As the mathematical model between the topology and parameters,filters synthesis method can not only be a guide for the filters design,but also be applied to other component design.Therefore,it is necessary to study the synthesis theory of filters.In order to meet the rapid need of wideband application,the synthesis and design of the wideband components with high performance are a hot research topic,which has attracted much attention.Under the background of the modern wireless communication system,focus on the filter,filtering power divider,phase shifter and crossover,the synthesis and design method are systematically studied and discussed in this dissertation.The main contents of this dissertation can be summarized as follows:1.The filter synthesis method based on the numerical iterative technique has been studied.Compared with the traditional method based on the general Chebyshev filtering function,the numerical iterative method has higher degree of freedom.The normalized passband and the ripple level of each return lobe can be user-defined.Moreover,the method can be extended to multiband applications.Based on the numerical iterative technique,the synthesis of dual-band and multi-band filters is proposed,of which the ripple level can be controlled.The proposed method avoids the use of the traditional complex frequency mapping functions and breaks the limitations of the same order in each passband and the symmetric distribution of transmission zeros.By utilizing the numerical iteration technique,the general directly synthesis method and coupling matrix modification method for the filters with complex impedances is further proposed based on the power wave renormalization theory.In addition,this method is extended to the dual-band applications.Furthermore,according to the coupling of the input or output stage of the filter terminated with complex impedances,four typical equivalent circuit structures are proposed and every elements can be calculated by the given equations.Finally,the lumped circuit for the filter with complex impedances can be constructed.2.The synthesis of wideband bandpass filter has been studied.Based on the numerical iterative technique under the bandpass domain,the synthesis and design method for the wideband bandpass filter are proposed.Based on the proposed method,the frequency dependent network matrice for the pure electrical coupling,magnetic coupling and hybrid electrical and magnetic coupling are extracted under the canonical transversal topology,which solve the problem that the traditional coupling matrix is frequency-independent and only applied to narrowband applications.For the network matrix with cross coupling,the mixed electrical and magnetic coupling is introduced in the main coupling path to eliminate the cross-couplings by using the matrix transformation,which reduce the complexity of the topology.Based on the lumped circuit of the wideband filters,the distributed circuit can be built by using the proposed circuit transformation.In order to validate the method,a wideband filter with transmission zeros is successfully synthesized and designed.3.The synthesis and design method for the filtering power divider has been studied.For the narrowband application,the multi-port coupling matrix of the filtering power divider is constructed according to the coupling matrix of the filter.Based on the multi-port coupling matrix,the filtering power divider with alternative J/K inverters and ?/4 resonators has been proposed to validate the synthesis method.For the wideband application,the wideband filtering power divider has been proposed by embedding the coupled line into the Wilkinson topology.By loading the open stub at the input port,the circuit size is reduced and the transmission zeros at upper stopband is produced to suppress the harmonic signal.In order to achieve a more compact structure,a three-line coupled structure is utilized to replace the traditional T junction in the Wilkinson topology and a novel wideband filtering power divider with embedded three-line coupled structure is proposed.The three-port network is proposed to directly analyze the three-line coupled structure for the first time,which solve the problem that the traditional virtual open/short wall at the symmetry plane cannot be directly applied to fully analyze and model this structure.In addition,the filtering characteristic function is introduced into the filtering power divider synthesis based on the proposed three-port network.Finally,a wideband filtering power divider has been successfully synthesized and designed.4.The wideband phase shifter using multiple quarter-wavelength short-ended stub has bee studided.The relationships between the phase difference and the impedance parameter have been derived for the two and three order phase shifter.The influence of the different parameters on phase difference is discussed.A generalized design equation for N order phase shifter has been proposed,which indicates the relationships between the phase difference and the impedance of the shorted stubs.Based on the proposed design equations,the user can accurately and fast design this type of phase shifter.The proposed phase shifter can achieve a wideband phase difference and a wide range of phase shift.5.The wideband planar lumped crossover has been studied.The wideband lumped crossover based on the window shape structure is proposed.By utilizing the even-odd mode theory,the four-port crossover is well analyzed and each element can be obtained.In order to expand the matching bandwidth and isolation bandwidth,four shunt resonators are loaded at each port.The control of the transmission zeros between adjacent ports and the influence of circuit parameters on the performance have been discussed.The wideband lumped crossover is finally designed to verify the theory.Compared with the distributed ones,the proposed crossover has extremely compact circuit size.The operating bandwidth is enhanced more than 132% compared with the other lumped ones.