ABSTRACT Present article exhibits the design of a third-order compact parallel-coupled line bandpass filter at 5.25 GHz having asymmetric perturbations to suppress the second harmonic. Initially, the effects of compactness on filter characteristics have been studied by synthesising the distributed filter network into its equivalent circuit model. The design has been initiated by computing the unit cell model, which leads to the first-order and third-order design instances with an improvement in compactness over the traditional parallel-coupled line filter. In contrary, compactness in the filter characteristics degrades the second harmonic level subject to enhanced imbalances among the odd- and even-mode velocities at the coupled lines. Subsequently, the improvement in the harmonic suppression of 53 dB and 58 dB has been achieved by incorporating different non-uniform perturbations to the outer and coupled edges of the compact filters. Accordingly, compactness of 58% and 71% have been obtained subject to the folded and in-line designs over the conventional layout.

中文翻译：

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具有非对称扰动的紧凑型耦合线带通滤波器中的杂散谐波抑制

摘要 本文展示了具有非对称扰动以抑制二次谐波的 5.25 GHz 三阶紧凑型平行耦合线路带通滤波器的设计。最初，通过将分布式滤波器网络合成为其等效电路模型来研究紧凑性对滤波器特性的影响。该设计是通过计算晶胞模型开始的，这导致一阶和三阶设计实例与传统的并行耦合线路滤波器相比在紧凑性方面有所改进。相反，滤波器特性的紧凑性会降低二次谐波电平，这会导致耦合线上奇数和偶数模式速度之间的不平衡加剧。随后，通过将不同的非均匀扰动结合到紧凑型滤波器的外边缘和耦合边缘，已经实现了 53 dB 和 58 dB 谐波抑制的改进。因此，折叠和直列式设计比传统布局获得了 58% 和 71% 的紧凑性。