小型化多层双模基片集成波导平衡带通滤波器

针对平衡滤波器小型化和高选择的应用需求，提出两种新型的多层双模基片集成波导平衡带通滤波器。首先详细分析了基于平衡端口馈电的双模基片集成波导谐振器的特性；然后根据谐振模式分布特性，设计了一种输入输出馈线同时在上层双模谐振器上的四阶平衡带通滤波器，下层双模谐振器通过十字交叉槽线结构与上层谐振器耦合，可以实现三个传输零点；又提出一种输入和输出馈线分别在上层和下层双模谐振器上的四阶平衡带通滤波器，上层和下层谐振器通过一个槽线进行耦合，可以实现两个对称的传输零点。基于提出的两种平衡滤波器结构，分别设计了一个中心频率为10 GHz的平衡带通滤波器，并进行加工和测试。测试和仿真结果一致性较好，表明了该结构可以实现小型化和高选择，并且具有很好的共模抑制特性。

Compact balanced bandpass filters based on multilayer dual-mode substrate integrated waveguide cavities

To design size-reduced balanced bandpass filters (BPFs) with high selectivity, two new multilayer dual-mode substrate integrated waveguide (SIW) balanced BPFs are proposed. Firstly, the characteristic of dual-mode SIW cavity is analyzed in detail. Then, a balanced SIW BPF with balanced input/output (IO) ports locating on the upper dual-mode SIW cavity is proposed, and the lower dual-mode SIW cavity is coupled to the upper one using two crossed slots. Three transmission zeros (TZs) can be produced at any locations. A balanced SIW BPF with balanced IO ports locating on the upper and lower dual-mode cavities respectively is also proposed, and the two cavities are coupled by a slot. Two symmetrical TZs can be produced. Based on the proposed structures, two filters with center frequency of 10 GHz are designed, fabricated and measured. The measured results agree well with the simulated ones, which indicates the feasibility of the proposed multilayer dual-mode SIW balanced BPFs with compact size and high selectivity.