Research On Receiver Of Downhole Positioning System Based On UWB Technology

Based on the practical significance of the UWB downhole positioning system,combined with the UWB wireless communication system,the generation of the pulse signal,the estimation of the transmission channel and the reception of the pulse signal,which affect the performance of the receiver,are studied.Considering the influence of the signal-to-noise ratio of the receiving end on the receiving performance,the first-stage active circuit low-noise amplifier of the receiver is designed and simulated.The positioning algorithm based on TDOA model is improved.The UWB pulse signal model is designed with Gaussian pulse and the weighted coefficient obtained by the minimum mean square error criterion.The performance of the PSD approximation of the linear fitting waveform is better than that of the random iterative operation.Adjust the size of the pulse formation factor of each derivative to achieve standard radiation masking in the full frequency range.The transmit link model of PPM-TH-UWB and PAM-DS-UWB is established,and the system performance under two modulation modes is simulated and compared.The impulse response of the ultra-wideband multipath channel model was simulated.The results show that whether it is LOS or NLOS multipath channel impulse response,the single-pulse IR-UWB signal transmitted by the transmitter passes through the propagation channel,and the receiving end energy is a cluster of multipath components scattered in a period of time frame.The modulated signal is convolved with the multipath channel impulse response convolution to add Gaussian white noise as an input to the Rake receiver.The receiving principle of the Rake receiver is analyzed.A simple model of the equivalent Rake receiver is designed.The performance of the receivers with different multipath numbers is compared,and the compromise between the receiving performance and the system complexity is analyzed.The AVG-38143 transistor of PHEMT device with high dynamic range and low noise characteristics produced by Avago is used.A self-contained bias common source and negative feedback structure is used to complete a two-stage cascaded broadband low noise amplifier based on ADS simulation design.The simulation results show that the input and output return loss of the LNA is less than-10 d B in the frequency range of 1.0~3.0GHz;the system stability factor is K>1;the noise figure is 1.6±0.4d B;the maximum gain is 26.5d B,and the gain flatness is reduced.It is±0.5d B.Based on the TDOA positioning scheme based on ultra-wideband technology,a CHAN-UKF positioning algorithm is proposed.The position estimate obtained by the CHAN algorithm is used as the initial value of the UKF algorithm,and the initial estimate of the position is estimated twice.The simulation results show that the CHAN-UKF positioning algorithm has good stability and the accuracy of the positioning system is improved by nearly 50%.Figure 50;Table 3;Reference 52.