| With the advent of the information age,people have put forward higher requirements on the speed of information transmission.The use of broadband antennas can satisfy people's requirements for rapid information transmission,and moreover,the number of antennas in a wireless communication system can be reduced.Coupling between multiple antennas can be avoided,therefore reduce some cost.An omnidirectional antenna can achieve uniform radiation of energy in an azimuth plane or uniformly receive electromagnetic waves from space.There is a great demand in both civil and military fields.This paper focuses on the development of broadband omnidirectional antennas for research at home and abroad,and closely follows the actual engineering requirements,and proposes two types of broadband omnidirectional antennas.The specific work content is as follows:For the design of a wideband omnidirectional antenna with elliptical polarization,firstly,by carefully analyzing the design index requirements and consulting related literature at home and abroad,it was decided to use a combination of multiple tilted dipole element antenna designs to achieve a wideband omnidirectional elliptical antenna,and discussed in detail.It implements the principle of an elliptical polarized antenna.Second,the simulation of the broadband omnidirectional elliptical antenna simulation,studied the change of the tilt angle of the folded oscillator antenna on the H-plane horizontal polarization gain and vertical polarization gain,by adjusting the antenna The tilt angle makes the horizontal polarization gain of the antenna 4 d Bi greater than the vertical polarization gain.Then,actually debug the antenna.Due to the wide bandwidth of the antenna,when the matched design,the components such as the series and shunt capacitance and inductance are different in the rotation speed on the Smith chart,so that the standing wave of the antenna can be adjusted by the series,parallel capacitance inductance and other components.Finally,place the debugged antenna in the field and measure the gain.The test results show that in the range of 108-156 MHz,the standing wave of the antenna is below 3,the horizontal polarization gain is about-1 d Bi,the vertical polarization gain is about-5 d Bi,and the non-circularity of the antenna in the horizontal plane is below 2 d B.Good 360° uniform radiation characteristics.For the design of a wideband omni-directional 45° polarized antenna,firstly,according to the requirements of the indicators,it is determined that the antenna needs to use a combination of a wideband omnidirectional vertical polarized antenna plus a polarized polarizer.According to engineering experience,the wide-band omnidirectional vertical pole The preliminary selection of the antenna uses a double-cone antenna.Secondly,simulation software is used to simulate the antenna.It is found that the bandwidth of traditional biconical antennas is not enough.Therefore,it is necessary to modify the design of the antenna.Then,a cylindrical body is connected to the end of the traditional double-cone antenna so that the current does not mutate after passing through the tapered gradient structure.This can reduce the influence of the reflected wave caused by the sudden change of the structure of the traditional double-cone antenna,and thus effectively widen the antenna.The bandwidth of the antenna,and then through the simulation,found that the modified biconical antenna has a wider bandwidth than the traditional bicone antenna.Finally,the finished antenna will be fabricated and measured.The test results show that the polarization angle of the antenna is about 43.5°.In the range of 2.5-6.5GHz,the standing wave of this antenna is less than 2.5,which shows a good broadband impedance matching characteristic.The out-of-roundness of the H-plane actually measured by the antenna is larger than the simulation value.In the working frequency range of the antenna,the roundness of the antenna is less than 7 d B,and the omnidirectional radiation requirements are basically achieved. |
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