In this paper, different techniques for the generation of additional transmission zeros (TZs) in planar waveguide filters are investigated. In the classical theory, TZs are generated only by destructive interference of non-adjacent cavities, limiting the available number of TZs to the filter order itself. However, more approaches for the generation of TZs are known, including bypass-coupling in oversized cavities, frequency-dependent coupling apertures as well as dispersive/resonant TZs which can be realized by the direct source to load cross-coupling. The aim of this paper is to combine several of the strategies in one physical filter set-up to increase the maximal number of TZs beyond the filter order. Different Ku-band fourth-order filter set-ups are presented, showing in total between six and eight real as well as complex TZs. Three filters are manufactured as a proof of concept and compared with the simulation, showing very good agreement.

中文翻译：

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在 H 平面波导滤波器中生成多个附加传输零点的技术

在本文中，研究了在平面波导滤波器中生成附加传输零点 (TZ) 的不同技术。在经典理论中，TZ 仅由非相邻腔体的相消干涉产生，将可用的 TZ 数量限制为滤波器阶数本身。然而，已知更多用于产生 TZ 的方法，包括在超大腔中的旁路耦合、与频率相关的耦合孔径以及可以通过直接源实现负载交叉耦合的色散/谐振 TZ。本文的目的是在一个物理过滤器设置中结合几种策略，以增加过滤器阶数之外的最大 TZ 数量。展示了不同的 Ku 波段四阶滤波器设置，总共显示了 6 到 8 个实数和复数 TZ。