Advanced microwave passive components design for antenna feeding network applications

Abstract

With the development of modern wireless communication and radar system, microstrip antenna arrays are widely used and developed. As two key components for antenna feeding network, couplers and phase shifters draw much attention in the past decades. In this thesis, the design for multi-section coupler, patch-based coupler and multi-section phase shifter are thoroughly studied and validated experimentally.

Since different input impedances and powers are always required for the antenna arrays, the couplers with different power outputs and impedance transforming are in great demand. As the first contribution of this thesis, a multi-section coupler with arbitrary power ratio and impedance transformation is proposed and thoroughly analyzed so that a wider bandwidth can be achieved. The method of replacing the connecting branches with a “uni-box” largely reduces the complexity of the analysis and provides the generalized equations for the multi-section coupler. Meanwhile, in order to avoid the mutual coupling of the branches, a patch based coupler with the same properties is also designed and discussed. A guideline for designing the generalized patch based structure is introduced as well.

For the second contribution of the thesis, a multi-section π-based phase shifter is designed and analyzed. In order to avoid the phase oscillation around the center frequency, the relation of the impedances for the short-ended stubs and the phase shift is fully analyzed. The proposed structure can then be extended to a higher order one to achieve a higher phase difference and a wider bandwidth.

The research presented in this thesis proposes an efficient method of analysing the multi-section coupler and phase shifter, and provides a guideline for designing the asymmetric patch based structure, which can be applied in the wideband and high frequency antenna feeding network design.