  The set of frequencies and angular properties of radiation emitted from a
solid-state crystalline undulator based on the channeling effect are
considered. High-frequency and low-frequency branches of the undulator
radiation and the angular distribution of the emitted radiation are analyzed.
The ranges of frequencies and angles of radiation emitted from the solid-state
crystalline undulator based on the channeling effect are found. The frequency
splitting and the energy threshold in the production of undulator radiation are
shown and discussed.
