Accurate Measurement Of VHF Antenna Gain

Nowadays,with the rapid development of wireless electronic communication technology,the antenna industry has played an increasingly important role in the production and life of our nationals.Nowadays,with the continuous development of the times,the requirements for antenna accuracy in industrial production continue to increase,and antenna measurement is an indispensable part of antenna design.Therefore,high-precision antenna measurement has become an important part of antenna design and production.However,in the VHF frequency band,there are still a series of problems in the design and measurement of antennas.Due to the relatively large volume of the VHF antenna itself and the location where it is often erected in the field,it is difficult for the conventional antenna measurement system to accurately measure the VHF antenna.Therefore,the precise measurement of VHF antennas has become an important topic in this field.Generally speaking,the gain,directivity pattern,standing wave ratio,input impedance and working bandwidth are the data of the VHF antenna we need to obtain.The gain is one of the most important parameters that determine the performance of the antenna.Therefore,accurate measurement of the gain of the VHF antenna that has very important practical significance is worthy of discussion by scholars.This thesis first introduces the theoretical knowledge of antenna measurement and related measurement techniques,combining the three parts of pattern measurement,gain measurement,and antenna impedance measurement to introduce the relevant theories of antenna far-field measurement.Among them,it focuses on the related methods of antenna gain measurement in the far field,analyzing the theories of comparison method,the two same antenna method,three-line method and image method one by one,and mainly introduces the characteristics of different gain measurement methods in practical application.After that,this thesis combines actual simulation and measurement to study the method of accurately measuring the gain of the VHF antenna.This thesis first uses HFSS to simulate the ultra-short wave antenna(log-period dipole antenna).The simulated antenna frequency range is 30MHz?2GHz,and the gain result of the log-period antenna in the ultra-short wave frequency band is obtained.Then we can use the two same antenna method to actually measure the antenna,analyze the factors that cause the error from the antenna impedance mismatch,antenna polarization mismatch,cable insertion loss,ground reflection wave,background electromagnetic noise,etc.,and quantify it.Finally,for the background electromagnetic noise,this thesis uses wavelet transform to filter out the noise,in order to achieve the purpose of narrowing the error and accurately measuring.This thesis combines theoretical analysis with actual measurement.After multiple gain measurements are made and the results are obtained,they are compared and analyzed with the simulated gain value.We should verify the feasibility of the method proposed in this thesis.Finally,this series of analysis methods are applied to real-world measurement to achieve accurate measurement of VHF antennas.