Research On The Key Technology Of Ultra-Wideband Radar Sensor

Ultra-wideband signals have strong penetrating power for leaf clusters and earth surface,and can detect hidden targets in complex environments,such as behind walls and under dense leaf clusters.In addition,ultra-wideband signals have the advantage of high transmission rate,large information capacity,anti-multipath interference ability and so on during communication.Therefore,Ultra-wideband(UWB)technology has attracted extensive attention and in-depth research in the field of target detection and communication.Based on the extension of the external application environment of wireless sensor network(WSN),this paper designed an ultra-wideband radar sensor with distance measurement through the wall as its main function.In the actual application process,the sensor can be used as a node of the WSN to improve the WSN's ability of detecting the hidden target.In view of the ultra-wideband radar sensor proposed in this paper,to achieve the function of distance measurement through the wall,this paper firstly discussed the basic structure and working principle of the sensor,and standardized the main performance indicators.Subsequently,the core technology of the ultra-wideband radar sensor-Generation,transmission and reception technology of ultra-wideband pulse signal had been deeply researched,and an ultra-wideband pulse signal generator and Vivaldi antenna with excellent performance were designed.The design method was simulated and experimentally verified.The main contents of this paper are as follows:1.Based on the functional background of distance measurement through the wall,the UWB radar equation was derived.The effects of the gain of the transmitting and receiving antenna,the reflection coefficient of the target surface and the transmission coefficient of the wall on the radar detection range were clarified;the system structure of the radar sensor and the principle of distance measurement was discussed.The two main performance indicators of distance resolution and maximum detection distance were standardized.The relationship between the detection range of radar sensors and the power of pulse signal transmission was also discussed.2.The advantages and disadvantages of several different types of pulse signal generators were analyzed and compared.From the perspective of increasing the amplitude of the pulse signal and shortening the duration of the pulse signal,a pulse signal generator with a fast step characteristic of the step recovery diode and an avalanche characteristic of the RF triode was designed.The pulse signal generator was simulated.The simulation results showed that the pulse signal generator could output a periodic pulse with a duration of 600 ps and a peak-to-peak value of 4 V,and the symmetry of the pulse waveform was good.Under the practical test conditions,the pulse duration was about 3.2 ns,the peak-to-peak value was about 3.4 V,and the symmetry of the waveform was slightly good.There was a certain deviation between the experimental results and the simulation results.3.The development history of Vivaldi antenna was discussed,and several different methods for expanding the antenna bandwidth were analyzed.Aiming at transmitting and receiving the pulse signal generated by this design,a traditional ultra-wideband Vivaldi antenna was designed,and the micro strip line of the antenna-slot line conversion balun was improved.The influences of different exponential gradation rates on the radiation performance of the antenna was discussed.The simulation test showed that the low-frequency cutoff frequency of the antenna is 0.25 GHz,the high-frequency cutoff frequency is above 3GHz,also the characteristics of polarization and radiation were good,which met the demand of transmitting and receiving pulse signals.4.Aiming at meet the demand of the ultra-wideband radar sensor for the control system proposed in this paper,a control system composed of ARM and time delay chip was designed.Combined with the function of the radar sensor,the circuit schematic of ARM and time delay chip was designed.The program flow chart of the control system's software layer was demonstrated.Combined with the radar sensor's ranging principle,the time and logic sequence of the flow chart was verified.