Design And Application Of The Improved Two-Stage Colpitts Circuit

With the development of the times,the detection of leakage signals in underground pipelines has become more and more important,making the requirements for signal sources more and more diverse.Since chaotic signals are easy to generate,they are relatively simple to control.Chaotic signals have strong anti-interference and are very difficult to be intercepted.Therefore,they have been widely studied.Because the Colpitts circuit generates chaotic signals based on the non-linear effects of the triode itself,and the chaotic signals it can generate have a relatively high fundamental frequency and a relatively flat spectrogram,and the circuit structure is simple and easy to implement compared to other forms.It has been a hot topic of research.The main task of this paper is to design the chaotic signal source in ground penetrating radar based on the Colpitts chaotic circuit and carry out the following research:(1)Briefly introduced the principle of ground penetrating radar,various models,development status at home and abroad,and application prospects.(2)Researched several different generation methods and principles of chaotic signals.For example,a chaotic signal is generated using a circuit,anonlinear optical Kerr effect is used to generate a chaotic signal from a fiber laser,and a chaotic signal is generated by using a map.And focus on the chaotic Colpitts circuit signal were studied.(3)Aiming at the phenomenon that the standard two-stage Colpitts chaotic circuit is easily affected by the parasitic capacitance at high frequency and the circuit oscillation state is destroyed,an improved method is proposed to obtain the improved two-stage Colpitts chaotic circuit.The basic information of bifurcation diagram,maximum Lyapunov exponent spectrum,phase space,and time-domain diagram of the circuit is analyzed by numerical simulation.The circuit can work in multiple forms such as single-cycle,multi-cycle and chaotic states.And using the PC method to design a synchronous system,simulation to verify the effectiveness of the system.(4)Through radio frequency circuit simulation,the frequency spectrum and autocorrelation spectrum information of the improved two-stage Colpitts chaotic circuit signal are obtained.Comparing with the standard two-stage Colpitts chaotic circuit,it is found that by improving the circuit structure,the fundamental frequency energy of the chaotic signal generated by it reaches5 GHz,which is about 2GHz higher than that before the improvement.And at the same fundamental frequency,the improved chaotic signal has a flatter spectrum,and its autocorrelation spectrum has a narrower full width at half maximum.(5)The generated chaotic signals are used in the detection of underground pipeline leakage to obtain a two-dimensional map of the detectionof underground targets.The background clutter is removed by mean processing to obtain the initial underground target result map.Then four intrinsic modal functions(IMF)of the image after simple processing are decomposed by empirical mode decomposition(EMD)method.Studies have shown that second-order IMF components remove a large amount of boundary noise and are more suitable for further accurate target location analysis.