Study On Novel Printed Log Periodic Antennas

Log periodic antenna(LPDA)has excellent broadband characteristics and simple structure.It has been widely used in short-wave,ultra-short wave and microwave band communication.Nowadays,the printing structure of LPDA has become the mainstream,this paper will study the printed LPDA.Since the length of the printed LPDA radiation unit is determined by the wavelength of its working frequency,the lower the frequency means the greater the length.Therefore,the antenna has a large size problem,which greatly limits the application of traditional printed LPDA,so miniaturization is the first research direction of this paper.In addition,although the printed LPDA has a good directivity and stable medium gain,the gain space is limited,which limits its application in high-gain applications.In view of the above problems,this paper explores how to improve the gain of printed LPDA and provides some solutions.Major tasks include:(1)A miniaturized LPDA based on unit bending is designed.First design a traditional printing LPDA,based on the traditional printing of LPDA the longest length of the radiating element 3/4,1/8,1/16 according to the proportion of three times 90 degrees bend,according to the scale factor and half-angle of radiating elements,in order to calculate other radiation unit of length and width.Through the simulation analysis contrast after found that the performance under the condition of little change,this design compared with traditional printing LPDA,antenna got deep cuts in physical size,achieved the effect of miniaturization.(2)Designed a high-gain printed LPDA with exponential profile,the antenna radiating element of traditional printing LPDA linear contour substitute exponential profile,which changes the current distribution situation of antenna,and thus improving the antenna's radiation,has resulted in a high frequency within the working frequency band of the antenna gain has the obvious improvement.It can be found by comparing with the traditional printed LPDA,an index profile of LPDA in keeping the reflection coefficient and direction throughout the whole frequency band figure almost the same,the high frequency part of the gain can increase 2-3 dBi.