Borehole radar stepping frequency-controllable gain receiver leading end

The invention belongs to a hardware composition unit of a borehole radar logging system and particularly relates to a borehole radar stepping frequency-controllable gain receiver leading end. According to the borehole radar stepping frequency-controllable gain receiver leading end, real-time adjustment control on a gain stepping value is realized through a single-chip microcomputer control circuit according to an output signal value, and an opening-closing-loop-controllable gain control function is further provided. At least twice of down conversion processing on an input signal is carried out through a mixer and a filter, frequency bandwidth of a finally-outputted intermediate frequency signal is made to be quite narrow, instantaneous bandwidth corresponding to a receiver is made to be quite small, noise interference is effectively inhibited, and system sensitivity is improved. For a gain control unit, a gain balance device is utilized to realize high gain flatness, -13dB-95dB linear gain control is finally provided, and 0.5dB-16dB gain stepping is realized. The borehole radar stepping frequency-controllable gain receiver leading end is advantaged in that unsynchronized transceiving modes are realized, gain flatness is high, gain control is convenient, and the borehole radar stepping frequency-controllable gain receiver leading end is suitable for a receiver system with a quite great reception signal scope.