Experimental investigation of broadband vaned helix traveling-wave tube

A broadband helical traveling-wave-tube (TWT) amplifier for microwave power module (MPM) applications is designed using high frequency structure simulation (HFSS) and LMsuite code. The LMsuite, which is a one-dimensional nonlinear code, was utilized to predict the nonlinear, large-signal performance of the helical TWT. Simulations predict that an output power of 22.6W is produced when an input power of 63.1 mW is injected at 10GHz, corresponding to a saturated gain of 25.5 dB. The saturated bandwidth is predicted to be 6-17 GHz. Experiments on a fabricated TWT show that an output power of 18.7 W is produced when an input power of 42.6 mW is injected at 10 GHz, corresponding to a saturated gain of 26.4 dB. The saturated bandwidth is measured to be 6-16GHz. AM/PM distortion is up to 6 degrees/dB at a drive level 6dB below the saturation input power. The third-order intermodulation distortion (IMD) ratio is - 19 dBc at a 10 dB backoff from the PI dB point when two-tone signals of 12 and 12.005 GHz are injected at equal amplitude.