A 0.35-THz Extended Interaction Oscillator Based on Overmoded and Bi-Periodic Structure

Abstract

An improved topology of Extended interaction oscillators (EIO) is presented with enhanced efficiency at 0.35 THz. A bi-periodic ladder-type structure is used for optimizing the performance of the TM31-2π mode operation. The proposed topology is based on bi-periodic interaction gaps composed by staggered short and long slots. The bi-periodic interaction mechanism permits to operate the circuit with a standing-wave field between the π and 2π modes, thus providing the potential to combine the advantages of both π and 2π modes in terms both of coupling and output performance. The resulting transverse TM31 operating mechanism exhibits a good agreement with bi-periodic structure in terms of coupling performance, with the short slot length positively correlated with the value of effective characteristic impedance M 2 R/Q. The optimization of M 2 R/Q and Qe, the circuit demonstrates attractive coupling and output characteristics. A state-of-the-art value M 2 R/Q of 59.69 Ω and a moderate Qe of 2523.52 are achieved for the proposed ladder-type EIO. A RF power of 540 W is obtained with a 42.5 kV, 0.6A sheet beam, with 2.1% electronic efficiency at 0.35 THz.

High-efficiency terahertz-wave generation based on extended interaction oscillator with strongly-coupled 2π mode operation

“…For instance, a 0.22 THz π-mode bi-periodic EIA, with a cavity M 2 R/Q of 44 Ω, exhibits a Pf 2 value of 0.032, 660 W average power, and 2% efficiency 14 ; a 94 GHz π-mode bi-periodic EIO, operating at an R/Q of 346 Ω, achieves a Pf 2 value of 0.0052 (592 W average power), with an efficiency of 6.6% 12 . However, problems are encountered in practical studies where the π-mode has difficulty extracting power longitudinally in the over-dimensional TM n1 -mode state, thus limiting the saturation output power 15 (primarily due to its excessive external quality factor Q e ). In contrast, the 2π mode offers reliable output power, leveraging its advantage of smaller Q e .…”

“…For example, a periodic cusp magnet equipped, 94.9 GHz mono-periodic EIO has demonstrated a Pf 2 value of 0.092 and a peak power of 10.2 kW 16 ; a 94 GHz mono-periodic EIA with a lower loaded-quality-factor Q l of 210 achieves a peak power of 7.7 kW, with an efficiency of 8.6% and a Pf 2 value of 0.068 4 . Alternatively, if the much-proven optional 2π mode is reconsidered it faces the restriction of M 2 R/Q than π mode 15 , 17 . The evolution and development of THz-EID technology have been full of trade-offs and compromises due to the respective advantages for the 2π and π modes.…”