Study of a 0.3 THz Double-Staggered Grating Waveguide-Based Band-Edge Oscillator

The design of a novel band-edge oscillator based on double-staggered grating waveguides (DSGWs) is presented in this article. For a traveling wave tube (TWT), the band-edge oscillation is typically expected to be eliminated since it will affect the stable operation of a TWT. However, in this design, such an oscillation is employed to generate a high-power terahertz signal within a small tunable bandwidth (~2.0 GHz) by changing the beam voltage. To suppress the higher-order modes competition, a novel concentrated attenuator with the mode filtering property is proposed. To verify this design, a DSGW circuit made of 88 periods was manufactured and measured. Measured results showed that the transmission coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> was higher than −8.0 dB; meanwhile, the reflection coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> was lower than −10.0 dB over the bandwidth of 2.0 GHz (298.6–300.6 GHz). The DSGW circuits with two different kinds of dielectric attenuators were also processed and tested. The simulated and measured S-parameters and dispersion curves were in agreement, demonstrating the feasibility of our design. PIC simulation results predicted an output power exceeding 101.2 W within the frequency range of 298.6–300.6 GHz (2.0 GHz).