Research On Miniaturized Antenna Based On Time Domain UWB Positioning System

With the development of ultra-wideband positioning systems in the direction of miniaturization and broadband,the miniaturization,low coupling,and broadband design of the ultra-wideband antenna,the key component of the UWB positioning system,has also received increasing attention from scholars at home and abroad.This paper is also an in-depth study of UWB antennas from these three aspects.This paper mainly includes the following:1.The composition and working principle of UWB positioning system and the principle of AOA and TDOA algorithms often used in UWB positioning are studied.The role of UWB antenna in positioning system is more clear.2.A miniaturized Vivaldi antenna with curved branches is designed.Firstly,the characteristics of the current distribution of the antenna at various frequencies are studied.For the further miniaturization design of the antenna,the effect of digging away the area with almost no current distribution at each frequency point on the radiation performance of the antenna is investigated.As a result,it is found that the impedance bandwidth of the antenna is hardly affected,but the gain of the low frequency band is increased.By adding curved branches,an additional resonant frequency point is added at the low frequency band,so that the low frequency bandwidth edge extends from 3.15 GHz to 2.45 GHz.It is found that the currents on adjacent curved branches are opposite to each other.If they are too close together,the currents will cancel each other out,which will not extend the edge of the low-bandwidth band.The gain of the antenna is higher than 4dBi,and cross polarization is low.Stable directional radiation can be achieved,and time domain characteristics are good.3.Miniaturized ultra-wideband antennas with complementary galvanic-magnetic dipole loading are designed.A loop antenna composed of a loaded curved branch and original antenna structure radiates energy at low frequencies,equivalent to a magnetic dipole,and adds an additional resonant frequency at low frequencies.A pair of "wingshaped" structures radiate energy at high frequencies and are equivalent to electric dipoles.The reflection coefficient is reduced by absorbing the energy to the feed through the loading resistor.The influence of the size and position of the loading resistor on the radiation performance of the antenna is also studied.The low-bandwidth edge of the antenna extends from 3.15 GHz to 2.63 GHz,and the gain of the low-band is also improved.The antenna can achieve stable directional radiation with low cross polarization and good time domain characteristics.This loading idea is also applied to the monopole antenna.In order to avoid signal reflections,the floor is rounded off.After loading,the low frequency band edge extends from 3.28 GHz to 2.41 GHz.The antenna can achieve stable omnidirectional radiation,low cross-polarization,good time-domain characteristics.And the radiation efficiency can reach 65%-89%.4.An ultra-wideband bowtie array antenna with parallel feeds is designed.Firstly,the influence of the size of the different structures of the bowtie antenna on the bandwidth is studied.Then the differences in the characteristic impedance and the linewidth calculation method of the two kinds of microstrip lines with limited width and infinite width of the ground plate are studied,and two kinds of calculations for balanced microstrip lines are obtained,and based on this,the feed network is designed.Finally,the antenna unit and the feed network are combined and simulated to analyze the influence of the coupling between the antenna structures on the bandwidth,and then adjust their spacing.The measured bandwidth is 2.6GHz-4.63 GHz,and can shield the signal of WLAN frequency band.The measured gain of this antenna is 6dBi-10.6d Bi.The gain of the antenna in the low elevation angle is obviously higher than that in the high elevation angle,so it is more suitable for the low elevation angle and long distance positioning.The radiation efficiency of this antenna is about 80%,cross polarization is low,and its time domain characteristics are good.