Multi-kW 35 GHz TWT power booster development

We describe our progress on the development of a Ka-band TWT driver-booster combination to produce >1kW over a 5 GHz band centered at 35 GHz. The driver is an existing > 500 Watt broadband coupled-cavity TWT1, employing a 2 stage depressed collector. The power booster is a newly designed sever-less folded waveguide TWT designed to provide 3-4 dB of additional gain. The booster also uses a 2 stage depressed collector and a slightly modified version of the same electron gun used in the driver. A photo of the driver and booster under test is shown in Fig. 1. The principal challenges that had to be met in a booster design were: (1) achieving the required output power and bandwidth, (2) ensuring stable booster operation under both small and large signal conditions and (3) presenting a good output match to the driver so that the driver remains stable.