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What are the limitation of conventional tubes at microwave frequencies?

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Conventional tubes have limitations at microwave frequencies due to excessive interelectrode capacitance and electron transit times greater than the period of the microwave signal . These limitations prevent conventional tubes from effectively operating at higher frequencies. The interelectrode capacitance becomes critical at microwave frequencies, and the transit time of electrons in the tube is too long for microwave signals . As a result, conventional tubes are not suitable for generating microwaves and are limited to frequencies below 1 GHz . However, alternative microwave tube designs, such as plasma-filled tubes and velocity-modulated tubes, have been developed to overcome these limitations and enable microwave generation at higher frequencies .

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Book Chapter•DOI Microwave Sources, Sensors, and Devices N. Ida 01 Jan 1992	The limitations of conventional tubes at microwave frequencies include interelement capacitance and the transit time of electrons.
Patent Microwave device, high-frequency device, and high-frequency equipment Kiyoharu Seino, Masahiko Hunada - Show less +1 more 30 Jan 2008 2 Citations	The provided paper does not mention anything about conventional tubes at microwave frequencies.
Proceedings Article•DOI Stabilizing plasma-filled microwave tubes Igor Alexeff 05 Jun 1995 1 Citations	The paper does not mention the limitations of conventional tubes at microwave frequencies.
Proceedings Article•DOI Generation of 1 Megawatt RF Peak Power in S-Band Using Klystron T Sarala, S R Ashwini, Bhaskar Chatterjee, Priyanka Sharma, K Pravallika, Saddam Ali - Show less +5 more 01 May 2019 2 Citations	The limitations of conventional tubes at microwave frequencies are that they are limited to frequencies below 1GHz.
Book Chapter•DOI Introduction to Microwaves Joesph J. Carr 01 Jan 1996 1 Citations	The paper does not provide information about the limitations of conventional tubes at microwave frequencies.

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