Design Of Broadband Electrically Small High Frequency Antenna

High frequency communication has been widely used for a long time in military and civil fields. Along with the development of related technologies and the changes in application environments, the miniaturization of high frequency antennas has been an urgent requirement at the present time. This paper focuses on how to reduce the high frequency antennas’ size while ensure the bandwidth meets requirement. Due to the small size high frequency antennas are often characterized by electrically small antennas, so this paper mainly discusses the broadband technology of electrically small high frequency antennas.This paper introduces the basic concepts and theories of electrically small antennas in the second chapter. Then in the third chapter, this paper discusses the common broadband technologies of electrically small antennas. Here emphasizes three methods, including the non-foster impedance matching, antenna loaded and broadband matching network. The combination of non-foster impedance matching and broadband matching network forms an active matching method. The combination of antenna loaded and broadband matching network forms a passive matching method. In the following fourth and fifth chapters, this paper presents design cases based on the active matching method and passive matching method respectively.The monopole antenna and normal mode helical antenna are two basic types of high frequency antennas, which have the advantages of simple structure, wide applications and easy analysis. In order to reduce the difficulty of design and outstand the design process, this paper chooses the two basic antennas as design objects. The active matching method is used to match a monopole antenna, which height is 2m. And the passive matching method is used to match three normal mode helical antennas, which height are respectively 2m,3m,3m. Finally, the matched antennas all work at the frequency-band of 5-15 MHz. For the monopole antenna, its VSWR is whole smaller than 2 and its horizontal gain is greater than-3d Bi. For the mode helical antennas, their VSWR is whole smaller than 3 and horizontal gain is not less than-17 d Bi. This paper gives some complete design process, summarizes the design steps, and discusses a number of problems about design.