A strategy of fast computer analysis of a magnetron‐type cavity is developed based on combination of rigorous mode‐matching formulation and its simplified versions. Numerical examples are given when varying the aperture opening of the grooves and the radius of the noncorrugated inner conductor, for TE‐modes corresponding to the first and second natural frequencies which are of most practical interest. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 202–212, 2000