A step-frequency controllable gain receiver front-end for well radar

Abstract

The invention belongs to a hardware component unit of a well radar logging system, in particular to a front end of a well radar step frequency controllable gain receiver. The invention realizes the real-time adjustment and control of the gain step value through the single-chip microcomputer control circuit according to the magnitude of the final output signal, and provides a controllable gain control function of open and closed loops. The mixer and filter circuit have down-converted the input signal at least twice, so that the frequency bandwidth of the final output intermediate frequency signal is very narrow, and the instantaneous bandwidth corresponding to the receiver is very small, which effectively suppresses the noise interference and improves the system sensitivity. In the gain control unit, the use of the gain equalizer achieves high gain flatness, and finally provides a linear gain control of -13dB ~ 95dB, and a gain step of 0.5dB ~ 16dB. The invention realizes the asynchronous mode of sending and receiving, high gain flatness and convenient gain control; it is suitable for a receiver system with a large variation range of received signals.

Description

technical field [0001] The invention belongs to the hardware component unit of the radar well logging system in the well, and is mainly used to process the signal at the back end of the receiving antenna, and output the dual-channel radio frequency signal for the subsequent data acquisition unit, and specifically relates to a stepping frequency controllable gain receiver of the radar in the well front end. Background technique [0002] With the increasing demand of human beings for underground resources such as oil and gas, people's research on underground detection technology is increasing day by day. This requires in-depth research on resource distribution and geological structure, and the high cost of experiments urgently requires a high-precision, high-efficiency logging method. The borehole radar logging system is the product of applying borehole radar to petroleum logging. Its working mechanism is to detect geological anomalies with discontinuous electromagnetic chara...

AI Technical Summary

Problems solved by technology

[0003] At present, the vast majority of drilling radars belong to the shock pulse system, but it is difficult for this radar to meet the requirements of high resolution and long detection distance, and the corresponding frequency domain step frequency pulse radar can achieve high resolution High rate and high detection distance requirements, the system radar transmits high-power ultra-wideband small-step frequency signals, when encountering an underground medium with discontinuous electromagnetic properties, its reflection characteristics or transmission characteristics change, and finally from the reflected wave or Extract target information through pulse pressure technology in transmission waveform

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