Differentially Fed Frequency Swept Antenna

With the development and application of radar,communications and 5G technologies,electronic beam-scanning antennas have been widely used in different industry areas and have been developed rapidly.Frequency beam-scanning antenna(FBSA)is a widely used electronic beam-scanning antenna,which can adjust the beam pointing angle by changing its working frequency.This kind of antenna is characterized by low cost,small size,high mobility,reliability and maintainability.Most of the traditional FBSAs are single-ended antennas.When they are connected with a differential circuit,an additional balun is required.This procedure will increase the loss of the system and reduce the radiating efficiency.In order to directly connect the FBSA to a differential circuit,two kinds of differential-fed FBSAs are designed in this paper.The main contents of this paper are listed below:Firstly,the research background and significance of the research on differential-fed FBSAs are introduced.In this section,development and basic principles of FBSAs and differential-fed antennas are presented respectively.Then,an evaluation on the loss of different slow-wave transmission structures is discussed.The transmission loss of microstrip lines,spoof surface plasmon polaritons(SSPPs)and striplines with a length of 30λ_gis simulated and compared.The results reveal that the stripline has the smallest transmission loss among these three slow-wave lines,whereas its structure is complicated and expensive.The transmission loss of SSPPs is between that of the microstrip line and stripline.Their single-level structure results in a low-cost and uncomplicated fabrication procedure.The differential-fed FBSAs based on the SSPPs slow-wave line is designed in this section.The structure of SSPPs transmission line is optimized to achieve a low transmission loss.A quasi-Yagi antenna is chosen as the radiating element,which is coupling fed.Following this procedure,a FBSA with 10 radiating elements is finally designed.The scanning angle is estimated to be around 64 degrees with a gain of 14.33-15.01d Bi.The efficiency of the overall array is about 52%.Finally,the differential-fed FBSAs based on the strip slow-wave line is desgined in this section.The structure of strip line is optimized to achieve a low transmission loss.A quasi-Yagi antenna is chosen as the radiating element,which is coupling fed.Following this procedure,a FBSA with 16 radiating elements is finally designed.The scanning angle is estimated to be around 68 degrees with a gain of 14.8-15.9d Bi.The efficiency of the overall array is about 67%.The two differential-fed FBSAs can be directly connected to a differential circuit.The proposed method can reduce the system-level loss and improve the overall efficiency of the antenna array.Moreover,this structure is more compact than traditional differential-fed FBSAs.