Wide-Band Design for Multi-port Microwave Power Dividers/Combiners

• Main Authors: Chen, Yung-Jinn, 陳永進
• Other Authors: Ruey-Beei Wu
• Format: Others
• Language: en_US
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/37318928754817381603

博士 === 國立臺灣大學 === 電機工程學系 === 86 === This dissertation proposes a new N-way radial power divider/combiner design by radially combining matched sectorial components. For an efficient full wave analysis, a simplified mixed potential integral equation (MPIE) method is presented to deal with planar circuits with N-fold rotational symmetry and lumped elements. The N- way combining structure sums the power of N devices directly in one step without having to proceed through several combining stages. This opens the possibility of such structure having high combining efficiencies. The design idea originates from exploiting the symmetry of radial geometry to eliminate any amplitude and phase imbalance and in the mean time employing the sectorial component to serve as the impedance transformer. The requirement on wide bandwidth is achieved by incorporating sectorial component with input and output matching networks. A systematic design procedure has been summarized. It includes the selection of the most appropriate radius and angle of the sectorial component by applying radial transmission line theory and the optimal design of the transmission lines in the matching networks by commercial software. The new topology is employed to design 4-way and 14-way power dividers on the microstrip medium and the achievable bandwidth is 30 % and 15 %, respectively, for the criterion of VSWR<1.5. In order to extract precisely the scattering parameters of the proposed structures, the full wave analysis which can take into account the effects due to fringing field, radiation, and surface wave leakage should be resorted to. A numerically efficient technique for computing the multiport network scattering matrix of planar structures with N-fold rotational symmetry is presented. The technique is based on the solution of mixed potential integral equation (MPIE) by applying method of moments (MoM) solution in conjunction with both the triangular and rectangular basis functions. The ideal of discrete Fourier transform (DFT) is also incorporated to reduce the vast computer memory and CPU time required in the normal MPIE solution. Numerical results demonstrate the numerical efficiency and accuracy of the present technique. The hybrid DFT-MPIE is also extended to solve other structures which are nearly, but not exactly, of N-fold rotational symmetry such as disked type power divider, five-port circuit, and circular patch antenna. Finally, the performance degradation of N-way radial power divider/combiner due to the port failures is evaluated by DFT and transmission line theory. Combining turning-off method, the formula of degradation for N-way radial power divider/combiner with isolation resistors is exactly derived. Simulated results depict that a power divider/combiner with optimum isolation resistors is quite robust to the port failures.