The linear theory of electromagnetic radiation from a plasma-loaded sinusoidally corrugated backward wave oscillator driven by intense relativistic electron beam has been developed and analyzed numerically as well as analytically. A beam-plasma waveguide model has been proposed and studied analytically with an aim to give a guideline to achieve an optimally designed backward wave oscillator in the X-band frequency range. First, the dispersion relation for TM01 mode in absence of electron beam has been analyzed numerically for different structure-size parameters and plasma density. Then,...