The Transmitter Of Tinderground Electromagnetic Wave Computerized Tomography System Design Based On Pseudo Random Code Spread Spectrum Technology

Electromagnetic wave tomography system is a kind of widely used method in the field of petroleum, coal, metals, transportation, railway, water conservancy hydropower engineering and urban construction.A series of corresponding products has been developed both at home and abroad, such as the EM imaging measurement system XHB2000, underground electromagnetic wave instrument JW-5 and JW-4, and electromagnetic wave tunnel perspective instrument domestic WKT-6 type, etc. Although these instruments widely used, the detection range and the imaging resolution need to improve.Pseudo random code spread spectrum technology is widely used in spread spectrum communication, ranging, scrambler, encryption, etc, especially in the field of spread spectrum communication. With the rapid development of mobile communication technology, pseudo random code spread spectrum technology has been mature.Using spread spectrum technology strong anti-jamming capability, high frequency spectrum utilization, anti-multipath fading characteristics, a feasible method is found in order to solve the bottleneck in electromagnetic wave tomography system technology,which introduced pseudo random code spread spectrum technology into the electromagnetic wave tomography system. This method is very innovative, that still haven’t found the relevant research both at home and abroad.If the method is successful, its contribution to the field of electromagnetic wave tomography will be enormous. Main research content in the paper is as follows:First, this paper introduces the basic theory of PN code spread spectrum transmitters, including underground working principle of the electromagnetic wave tomography system, spread spectrum communication theory, the pseudo random code spread spectrum technology and frequency synthesis technology, providing theory support for the subsequent design.Second, it determines the technical index of the transmitter, and according to the index, put forward the overall design scheme of the transmitter. Transmitter consists of control system, signal source, filter, power adjusting circuit, power amplifier, power supply circuit, several functional modules. In the hardware design part, the paper introduces the design content of each module. Including chip selection, circuit design, circuit parameter settings from several aspects. In software design part, this paper introduces the overall software process system, and the serial communication, signal modulation, power adjustment, focuses on several parts, the timing requirements of the module software design was introduced in detail, and register operation, etc.Finally, according to the design plan, I set the transmitter prototype by testing the transmitter output waveform and the output power of test and verify the feasibility of the scheme.After testing, the system frequency of the transmitter based on the pseudo random code spread spectrum technology of electromagnetic tomography is 1 MHZ to 60 MHZ, which can achieve two digital signal modulation mode such as 2FSK and 2PSK, and modulation waveform is stable, high identification; The power of the transmitter can be up to a maximum of 15 w, within the emission band, the transmitter power can adjustment from 10w to 13w.