Analysis of a microwave power amplifier using a combiner/divider with circular cavities

Equations based on the discrete Fourier transformation developed for the analysis of a microwave power amplifier consisting of unit amplifiers and a power combiner/divider with circular cavities are presented. Equations of the mode voltages and currents of a power amplifier with some failed unit amplifiers are provided. The equations are obtained by taking into account the spurious-mode excitation to the cavity from the unit amplifiers, and are developed by using an analogous expansion by the discrete Fourier transformation (DFT). Equivalent circuits of the power amplifier for the various mode excitations are discussed, and load admittances for the spurious-mode excitations are applied to the equations for calculating the gain of the amplifier. The load admittance is analytically obtained using variational methods for a combiner with coaxial input/output ports. Numerical results for the power amplifier gain when there is a failed unit amplifier are shown. The effects of gain of the capability of suppressing spurious-mode waves using slits in the combiner are clarified