A new algorithm for solving Maxwell's equations in high-power microwave device simulations

Using the Coulomb gauge, an algorithm for solving Maxwell's equations that is capable of isolating the solenoidal current component from the total current has been developed. The electromagnetic field arising from the solenoidal current is expanded in terms of Bessel's functions. It is sufficient to retain only a few dominant global electromagnetic modes to simulate most microwave devices. Electrostatic modes that are localized within the beam region are followed by utilizing B-splines. The new code was used to investigate the plasma effect on ripple wall backward-wave oscillators and the self-field effect on gyro backward-wave oscillators. Simulation results show that the plasma response to the excited wave is in phase if the plasma frequency is less than the wave frequency. It is also demonstrated by simulations that the presence of a virtual cathode tends to increase the device output frequency and to reduce the interaction efficiency.