Abstract: The present invention relates to the field of communications, and more particularly to methods and a system for providing high-speed communications on a high-speed railway. The technical result is a better quality communication channel provided by train-to-ground radio relay links The claimed system for providing high-speed communications on a high-speed railway comprises an internal and an external data exchange network. The internal network unites tail-end radio frequency modules mounted in the rear part of a train and equipped with narrow-band antennae, head-end radio frequency modules mounted in the front part of the train and equipped with narrow-band antennae, and switching equipment capable of processing signals from said modules and of providing network devices connected to said equipment with access to the external data exchange network.

Abstract: The invention can be used for telecommunications, measuring and other devices in order to produce stable superhigh frequency signals. An IMPATT diode (4) operating in the cascade break-down mode and having a sharp nonlinearity transforms an input signal in such a way that ultraharmonics which multiple in respect to the frequency of an input signal ?0 occur in a frequency spectrum. An output stage of a multiplier is used in order to separate an output n?0 frequency and to suppress adjacent frequencies. In order to tune the output stage to the n?0 frequency, a tuning plug (8) and short-circuiting pistons (13) are used. The tuning plug (8) is arranged above an upper electrod of the IMPATT diode (4) (inside the axis of the diode). The tuning plugs (13) make it possible to tune resonance capacitance to the n?0 frequency and remove energy towards the output part of a T-bend in which a wave guide pass-band filter (15) is disposed.