Research On Key Technology Of Impulse Positioning

Recently,impulse positioning technology is a popular topic in wireless location by transmitting narrow pulse signal directly.This technology is widely used in short-distance communication systems and radars.For example,it can transmit signals at a high rate in indoor communication systems and significantly improve radar resolution in radar applications.Pulse is a kind of non-time-harmonic electromagnetic wave,so it is more effective to study the propagation,radiation and scattering of pulse in the time domain.The frequency band width of the pulse system is at the gigahertz level,and the impulse pulse width is at the nanosecond or even picosecond level.As a key component of the impulse positioning system,the time domain antenna is the hub of the wireless communication system.here are various kinds of time domain antennas for transmitting pulse,such as single cone antennas or double cone antennas with stereoscopic structure and bow antennas with planar structure.In order to improve the precision of signal processing and better positioning effect,from the perspective of antenna,the main line of research is to broaden the bandwidth of antenna and reduce pulse distortion.Therefore,this paper focuses on the time-domain antenna for positioning,which is analyzed and demonstrated from the time-domain and frequency-domain perspectives respectively.The main contents are as follows: Firstly,several key technologies of the pulse positioning system are analyzed,including the positioning principle,pulse signal waveform and time-domain pulse generator.Then the basic theory and analysis method of time-domain antenna is introduced which is different from the traditional frequency-domain antenna research.The parameter index to measure the performance of the time-domain antenna should be considered in combination with its application requirements in positioning.Not only the directivity,gain and impedance bandwidth should be analyzed,but also the time-domain characteristics such as waveform fidelity should be combined.Secondly,the characteristics of several UWB antennas in frequency-domain and time-domain are simulated,and the antennas that can be used as pulse positioning system are screened out.Then,an exponential tapered slot antenna,also known as Vivaldi antenna,is proposed.This design is different from the traditional vivaldi antenna,using all-metal materials,through wire cutting technology finishing,and feeding place does not need to be welded,directly through the SMA RF adapter feeding.The antenna has simple structure,high physical strength and low cost.The results show that the antenna has good directivity and VSWR in wide frequency range.From the point of view of time domain,the waveform fidelity of the antenna is better,which can be used as the antenna of impulse positioning system.Then,the antenna element is optimized to compare the effects of different curvature and structure size on the impedance bandwidth and time-domain characteristics of the antenna.So the all-metal vivaldi antenna is formed into a linear array antenna.In order to broaden the antenna bandwidth and improve the low-frequency characteristics,a method of non-uniform linear array is proposed.The antenna unit is tested in a microwave anechoic chamber,and the test results are basically consistent with the simulation results,confirming its good radiation performance.The time-domain characteristic test system is constructed,and a gaussian pulse signal is used as the excitation of the vivaldi antenna.The pulse waveform of the echo is observed at the receiving end,and the waveform fidelity performance of the antenna is analyzed.Finally,based on the basic non-uniform array antenna,this paper designs a kind of cross-structure antenna array.The antenna array has compact structure,dual polarization and wide coverage,which can well satisfy the needs of impulse positioning system.