It is shown that use of a photonic crystal enables to construct several types of hybrid systems with virtual cathode, which could radiate due to different radiation mechanisms (bremsstrahlung and diffraction (transition) radiation) with different frequencies. Also mentioned that photonic crystal makes possible to create phase-locked array of generators.
@article{arxiv.0903.0300,
title = {Hybrid systems with virtual cathode for high power microwaves generation},
author = {V. G. Baryshevsky and A. A. Gurinovich},
journal= {arXiv preprint arXiv:0903.0300},
year = {2009}
}