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<p>This work presents an upgraded U-shaped beam tunnel sawtooth waveguide (USTW) slow-wave structure (SWS), a novel low-voltage high-phase delay SWS operating scheme, and a microfabrication strategy for high-efficiency microscale high-frequency circuits for 1.03 THz traveling-wave tubes (TWTs). Compared with the base STW, the USTW provides stronger electric field focusing and achieves a better match between the electric field distribution and the pencil beam (PB), resulting in a 15.2% increase in average interaction impedance and a 16.1% improvement in saturated output power. The proposed operating scheme effectively addresses the high insertion loss, low output power, and low efficiency in conventional high-voltage low-phase delay design, enhancing saturated output power by 17.1% and electronic efficiency by 44.2% at the same conditions. PIC simulations predict that the 17.84&#xa0;mm 14.5&#xa0;kV‑505° USTW circuit, driven by a 14.5&#xa0;kV, 5&#xa0;mA&#xa0;PB, delivers 375.66 mW saturated output power, 0.52% electronic efficiency, and a 54&#xa0;GHz 3-dB bandwidth spanning 0.996–1.049 THz. Utilizing nano-computer numerical control (CNC) machining on dispersed oxygen-free high-conductivity (DOFHC) copper, a circuit with a 34&#xa0;μm feature size and 15&#xa0;μm vane thickness was successfully fabricated with high precision, with dimensional tolerance within 2&#xa0;μm and surface roughness below 75&#xa0;nm, far finer than the conventional 50&#xa0;μm feature size commonly achieved at comparable frequencies. Cold-tests of the 5.88&#xa0;mm sample circuit demonstrate a reflection coefficient below − 10&#xa0;dB and insertion loss of − 15.58&#xa0;dB at 1.03 THz. These results provide valuable references for developing high-performance high-frequency circuits for THz TWTs.</p>

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Design and Microfabrication of a High-Efficiency High-Frequency Circuit for 1.03-THz TWT

  • 期刊论文

  • 发表日期：

    2026年6月23日

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  • Yinyu Zhang,
  • Yuan Zheng,
  • Jin Zhang,
  • Yubin Gong

摘要

This work presents an upgraded U-shaped beam tunnel sawtooth waveguide (USTW) slow-wave structure (SWS), a novel low-voltage high-phase delay SWS operating scheme, and a microfabrication strategy for high-efficiency microscale high-frequency circuits for 1.03 THz traveling-wave tubes (TWTs). Compared with the base STW, the USTW provides stronger electric field focusing and achieves a better match between the electric field distribution and the pencil beam (PB), resulting in a 15.2% increase in average interaction impedance and a 16.1% improvement in saturated output power. The proposed operating scheme effectively addresses the high insertion loss, low output power, and low efficiency in conventional high-voltage low-phase delay design, enhancing saturated output power by 17.1% and electronic efficiency by 44.2% at the same conditions. PIC simulations predict that the 17.84 mm 14.5 kV‑505° USTW circuit, driven by a 14.5 kV, 5 mA PB, delivers 375.66 mW saturated output power, 0.52% electronic efficiency, and a 54 GHz 3-dB bandwidth spanning 0.996–1.049 THz. Utilizing nano-computer numerical control (CNC) machining on dispersed oxygen-free high-conductivity (DOFHC) copper, a circuit with a 34 μm feature size and 15 μm vane thickness was successfully fabricated with high precision, with dimensional tolerance within 2 μm and surface roughness below 75 nm, far finer than the conventional 50 μm feature size commonly achieved at comparable frequencies. Cold-tests of the 5.88 mm sample circuit demonstrate a reflection coefficient below − 10 dB and insertion loss of − 15.58 dB at 1.03 THz. These results provide valuable references for developing high-performance high-frequency circuits for THz TWTs.