A methodology for tunable bandpass filters (tBPFs) with one switchable transmission zero (TZ) is presented, wherein the frequency tuning and TZ switching can be simultaneously achieved by merely tuning the resonant frequencies of resonators. Theoretically interpreted by coupling matrices with arbitrary filtering orders (n ≥ 2), the TZ can be symmetrically switched between lower and upper sides of the passband while retaining the same return loss level. As a demonstration, a fourth-order waveguide tBPF is synthesized, designed, fabricated, and measured for experimental verification. Two responses, namely TZ on lower and upper sides, are showing the tunable frequency range from 9.5 to 10.8 GHz with insertion loss (IL) from 0.34 to 1.40 and 3-dB bandwidth from 230 to 370 MHz, respectively, which verifies the proposed methodology very well.

中文翻译：

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具有一个可切换传输调零功能的可调谐带通滤波器，仅通过调谐谐振


提出了一种具有可切换传输零（TZ）的可调谐带通滤波器（tBPF）的方法，其中仅通过调谐谐振器的谐振频率即可同时实现频率调谐和TZ切换。从理论上讲，通过具有任意滤波阶数 (n ≥ 2) 的耦合矩阵来解释，TZ 可以在通带的下侧和上侧之间对称切换，同时保持相同的回波损耗水平。作为演示，合成、设计、制造和测量了四阶波导 tBPF，以进行实验验证。两个响应（即下侧和上侧的 TZ）分别显示了 9.5 至 10.8 GHz 的可调频率范围、0.34 至 1.40 的插入损耗 (IL) 以及 230 至 370 MHz 的 3 dB 带宽，这验证了所提出的方法很好。