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Microwave tubes are used for generation and amplification of high power (up to MW of pulsed/CW output power) and high frequency (0.3GHz to 1000GHz) electromagnetic waves. These tubes are in great demands for defense, communication, remote sensing, and for numerous industrial, scientific, and medical (ISM) applications. Input and output RF couplings in microwave tubes are very significant for efficient and reliable operation of these devices. Any coupler for a tube basically consists of four constituents: (i) probe, loop or slot for coupling e.m. waves from or into the RF structure, (ii) coaxial or waveguide impedance transformation section, (iii) glass or ceramic window to provide vacuum barrier and lossless transmission of rf power, and (iv) standard coaxial or waveguide output. Antenna probe is used to excite the waveguide output in case of coaxial transition. 3-dimensional e.m. field simulators like Ansoft HFSS and MWS-CST codes are used to achieve well matched and broadband design of the input and output couplers with the antenna probe. Standard mechanical codes like ANSYS, COSMOS are used to achieve thermal efficient and mechanically rugged design of the antenna coupling. Antenna couplings for some of the microwave tubes are presented in this paper.