Demonstration of a 270-W G-Band Prototype TWT With −3 dB Bandwidth Over 18 GHz

To pursue the ultimate power-bandwidth product (PBP) and efficiency-bandwidth product (EBP) performance of G-band traveling wave tubes (TWTs), in-depth theoretical and simulation-based designs of both the high-frequency and electron optical systems were conducted utilizing a novel rhombic grating slotted sine waveguide (RGS-SWG) and a double-period magnetic focusing system. Theoretical analyses of high-frequency properties and electron beam transmission characteristics demonstrate that the RGS-SWG exhibits low insertion and reflection losses, a broad −3 dB power bandwidth exceeding 19 GHz, and a high maximum output power surpassing 276 W. Furthermore, the high-current electron beam (126 mA) can be stably transmitted over a distance of 73 mm within the high-frequency system without interception. Subsequently, a prototype RGS-SWG TWT was fabricated, and the experimental validation was completed. Hot test results indicate a peak output power of 276 W, a −3 dB power bandwidth greater than 18 GHz, and PBP and EBP values of 4968 W$\cdot $GHz and 153.3%$\cdot $GHz, respectively. The measured PBP and EBP of this broadband high-power TWT reach approximately$5.5\times $and$2\times $those of state-of-the-art existing devices.