Signal transmission system and signal transmission method

The embodiment of the invention provides a signal transmission system and method, and relates to the field of communication. The signal transmission system comprises a main unit device, a far-end frequency conversion device and a coaxial network. The main unit device is used for carrying out up-conversion processing on each channel signal in the multi-channel digital baseband signals and carryingout combination processing on the processed multi-channel intermediate frequency signals with different frequencies to obtain a first combined intermediate frequency signal. The coaxial network is used for transmitting the first combined intermediate frequency signal to far-end frequency conversion equipment. The far-end frequency conversion device is used for carrying out branching processing onthe received first combined intermediate frequency signals, carrying out up-conversion processing on each path of branched intermediate frequency signals to obtain radio frequency signals with carrierfrequency specified by an