Instrumentation used in the diagnostic of signals in fusion experiment needs protection against surges in signal power, which emerges from the electron cyclotron resonance heating (ECRH). In this article, a design methodology for the development of selective single notch waveguide is presented. The design of the notch filter is a circular corrugated waveguide that has been modeled based on the second-order Bragg-resonance condition. The device operation is between 75 and 105 GHz (i.e., $W$ -band), and a single stopband frequency is achieved. The magnitude of stopband transmission is further improved by modifying the corrugation geometry, where selected corrugations are combined periodically inside the waveguide. The proposed design allows the propagation of HE₁₁ mode. Due to the Bragg condition, the LP₁₂ mode is observed at the frequency of stopband resonance, i.e., 94 GHz. The proposed device was fabricated, and the measured transmission coefficient ( $S_{21}$ ) was observed in coherence with the simulated $S_{21}$ profile. The notch filter finds an important application in wideband signal diagnostics of electron cyclotron emission (ECE) and reflectometry in the fusion plasma experiments.

中文翻译：

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改进的基于波纹的 W 波段波导，具有用于聚变等离子体诊断的选择性缺口操作

聚变实验中用于诊断信号的仪器需要防止信号功率浪涌，这种浪涌来自电子回旋共振加热 (ECRH)。在本文中，介绍了一种用于开发选择性单凹口波导的设计方法。陷波滤波器的设计是基于二阶布拉格谐振条件建模的圆形波纹波导。设备运行在 75 到 105 GHz 之间（即， $W$ -band），并且实现了单个阻带频率。通过修改波纹几何形状进一步提高阻带传输的幅度，其中选定的波纹在波导内周期性地组合。建议的设计允许 HE ₁₁模式的传播。由于布拉格条件，LP ₁₂模式在阻带谐振频率，即94 GHz 处观察到。制造了所提出的装置，并测量了透射系数（ $S_{21}$ ) 观察到与模拟 $S_{21}$ 轮廓。陷波滤波器在电子回旋发射 (ECE) 的宽带信号诊断和聚变等离子体实验中的反射测量中具有重要应用。