Design Of The Illuminator Of Continuous Wave Radiating Method

With the development of technology,more and more weapons which can cause electromagnetic interferences are applied in battle field,this phenomenon also leads to the deterioration of electromagnetic environment in battle field.For instance,higher demands of immunity of semiconductor components,electrical equipment and system have been made because of the emergence of electromagnetic pulse(EMP)weapon.Based on this reality,by combining the regulations in GJB 8848-2016 “Electromagnetic environment effects test methods for systems”,a continuous wave antenna is developed in this article,this antenna is also named continuous wave illuminator.The horizontally polarized illuminator element and transmission line balanced-unbalanced transformer are two main structures in this illuminator.According to the standard,the operating frequency of this illuminator is 100kHz~500MHz.At the beginning,the theoretical analysis is conducted,existing vertically polarized continuous wave illuminator design theory and antenna loading theory are summarized,a new horizontally polarized continuous wave illuminator design theory is suggested.Mathmatical modeling and optimization are accomplished by MATLAB simulation software,so that the variable field changing with the frequency in specified points at space can be calculated.The focus is on field distribution in low frequency(100kHz~500MHz)at near-field.This article also clearly introduces the parameters which can influence the design objective,such as shape,size and resistive load of illuminator,it also analyzes the influence of parameter variation on field distribution and provides a design example.The ratio of impedance conversion of balun is 1:4 and determined by the calculation result of input impedance of continuous wave illuminator.The introduction of circuit design,magnetic core selection and line length selection are demonstrated in two aspects named balancedunbalanced circuit design and impedance conversion circuit design respectively.The test result shows great performance in the whole frequency band,the stand wave ratios is lower than 3,the insertion loss is smaller than 0.85 dB,the balanced outputs has great symmetry below 30 MHz,balun can meet the requirements of actual use.According to the test results of magnetic cores,a Mn-Zn ferrite is chosen to load the illuminator element.The “worm hole” structure is selected to feed the balun by using the coxial core wire and inner surface of a shielding layer.The test result of CW illuminator shows that the model suggested by this article is closer to the real condition when compared with simulation model in CST,the suggested model can clearly illustrate the field distribution in near-filed test area at low frequency.The design objectives are achieved.