The Design Of Frequency-scanning Circuit In Underground Wireless Short Transmission System

In the underground formation test,it is necessary to use the sensor to collect the downhole pressure and temperature data,and transmit the data to the ground for readback processing,and analyze the data to design the subsequent mining plan.The underground environment is complex.Under different ground conditions,the passband of signal transmission will also be different.Therefore,in the process of wireless transmission of underground data,it is very important to be able to quickly and accurately determine the communication frequency band of wireless communication.Based on the research of underground data transmission technology at home and abroad,this paper analyzes the current working principle and finally designs a frequencyscanning signal generation circuit based on DDS technology.This design is mainly composed of four sub-modules,which are frequency-scanning signal generation circuit,gain control circuit and main control processing module.Among them,the frequencyscanning signal generation circuit mainly adopts DDS technology,which has short frequency conversion time,high frequency resolution,programmable control and superior performance.Together with the gain control circuit,the overall circuit can adapt to the test requirements.The single chip microcomputer STC15L2K60S2 is used as a control and processing unit.The ground host computer sends a control command to the single-chip microcomputer,and the process of each sub-module is controlled by the single-chip microcomputer,and finally the frequency-scanning signal is output.In order to verify the function of the frequency-scanning circuit to measure the passband,the ground simulation experiment of the wireless short-transmission system scanning circuit was carried out,and the amplitude-frequency characteristic curve was drawn by using the collected experimental data.In order to store the sweep signal transmitted by the receiving coil,a high-speed digital-to-analog conversion circuit based on the AD9246 chip and a data storage circuit matched by the STM32F103RBT6 minimum system microcontroller and the flash chip W25Q128 FVSIG are designed.The frequency-scanning signal output of the frequency-scanning circuit designed in this paper is stable.It is verified by wireless transmission ground simulation experiments that the frequency-scanning circuit can determine the passband of the wireless channel and meet the design requirements.