This letter reports on high-order coaxial-resonator-based bandpass filters (BPFs) with multiple levels of transfer function tunability, namely center frequency ( $f_{\mathrm {cen}}$ ), bandwidth (BW), and intrinsic switching off. They are based on cascaded multi-resonant cells, each exhibiting one pole and two transmission zeros (TZs), and in-line resonators. The proposed concept allows for high-order quasi-elliptic responses without cross couplings that can be reconfigured by only tuning the resonators’ $f_{\mathrm {cen}}$ . Low-cost integration using 3-D printed cavities and varactor-based PCB tuners is also shown. For proof-of-concept validation purposes, a five-pole/four-TZ BPF with $f_{\mathrm {cen}}$ tuning 1.3–1.77 GHz (1.4:1), BW tuning: 62–217 MHz (3.5:1), and an intrinsic switching-off state with >35 dB of isolation was manufactured and measured.

中文翻译：

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具有多级传递函数可调性的高阶同轴带通滤波器

这封信报告了基于高阶同轴谐振器的带通滤波器 (BPF)，其具有多级传递函数可调性，即中心频率（ $f_{\mathrm {cen}}$ )、带宽 (BW) 和固有关断。它们基于级联多谐振单元，每个单元具有一个极点和两个传输零点 (TZ)，以及串联谐振器。所提出的概念允许在没有交叉耦合的情况下实现高阶准椭圆响应，只需调整谐振器的 $f_{\mathrm {cen}}$ . 还展示了使用 3-D 打印腔和基于变容二极管的 PCB 调谐器的低成本集成。出于概念验证的目的，五极/四 TZ BPF 具有 $f_{\mathrm {cen}}$ 调谐 1.3–1.77 GHz (1.4:1)，BW 调谐：62–217 MHz (3.5:1)，制造并测量了具有 >35 dB 隔离度的固有关断状态。