The Study of a Millimeter to Submillimeter Wave Multiband High-Power Broadband Window

The theory of multilayer microwave window is investigated and applied to design a broadband high-power output window for a Q-band sheet beam traveling wave tube (SBTWT). The multilayer window consists of a c-axis sapphire disc (the geometry axis parallel to optical axis) in the middle and two identical matching quartz discs tightly attached on both sides. It presents a good multiband wideband and high-power performance from millimeter wave to terahertz range. The thermal property is analyzed and shows a more than 60 kW CW operating capability can be reached. The window is manufactured and cold tested shows a −17 dB reflection bandwidth over 15 GHz (34%). The theory analysis, simulation, and cold test present a good consistency.