This article discusses the synthesis of a new class of cross-coupled blocks incorporating frequency-variant couplings, that is, the frequency-variant blocks (FVBs), and their planar implementations based on an analytical approach. The proposed FVBs require fewer coupling elements with regard to traditional blocks, while can realize a quasi-canonical characteristic (i.e., realizing $k$ -1 transmission zeros for a block of $k$ th order). Derivation of the FVBs relies on a uniform synthesis process, where each transformation is mathematically simplified as a non-reciprocal matrix. An $N$ th-order quasi-canonical filter (possessing either symmetric or asymmetric TZs) can thereafter be synthesized by properly cascading the FVBs. Moreover, a unique planar technique is introduced to construct the quasi-canonical filters (with TZs above passband) using parallel-coupled microstrips, where a complete design procedure from synthesis to circuit parameters will be given. Validity of this work is eventually demonstrated by three illustrative examples, whose synthesis, simulation, and test results perform desired responses and are well-matched with each other.

中文翻译：

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包含级联变频块的准规范平面滤波器的合成与设计

本文讨论了一类包含变频耦合的新型交叉耦合模块的综合，即变频模块 (FVB) 及其基于分析方法的平面实现。与传统块相比，所提出的 FVB 需要更少的耦合元件，同时可以实现准规范 特征（即，实现 $千$ -1 块传输零 $千$ 次）。FVB 的推导依赖于统一的合成过程，其中每个变换在数学上都被简化为非互易矩阵。一个 $N$ 之后可以通过正确级联 FVB 来合成三阶准规范滤波器（具有对称或非对称 TZ）。此外，引入了一种独特的平面技术来构建使用平行耦合微带线的准规范滤波器（具有高于通带的 TZ），其中将给出从合成到电路参数的完整设计过程。这项工作的有效性最终通过三个说明性的例子来证明，它们的合成、模拟和测试结果执行了所需的响应，并且相互匹配。