Research And Design Of Ultra Wideband Log-periodic Antenna

Generally speaking,Antenna is used as a device which plays a role for transmitting electromagnetic wave,which has related to frequency,the ability The ability to transmit or receive energy is related to the structure and the size of the shape.Any antenna can not be used in the infinite frequency domain However,as long as the functional parameters of the antenna are concerned,such as Radiation pattern,gain?Polarization,Input impedance,phase center an so on.It is considered that the antenna has the characteristic of ultra wide band(UWB)which Maintain a constant or change within a range of acceptable range in a certain frequency range.Due to the rapid development of electronic information technology,ultra wideband antenna has more and more demand for the use.By the ultra wideband antenna as the support of UWB communication system is widely popular,the system with large capacity,wide bandwidth,good anti-interference ability,increasingly in the crowded spectrum business showing great advantage and the important position of the ultra wideband antenna has been present.So the research on ultra wideband antenna,its internal control rules,better design of ultra wideband antenna of different types is very necessary.In different forms of ultra wideband antenna,log periodic antenna with its unique structure,good broadband characteristics,and stable performance of the antenna,as many applications preferred.Usually in practical engineering applications,log periodic antenna by a series of parallel dipoles linear form,the dipole length,interval parameters and frequency change log cycle.The feeding of the dipole is accomplished by two parallel metal lines.The two parallel metal lines are called the set lines.The assembly line crosses the dipole which is attached to the antenna,so that the adjacent two sets of dipole antennas have inverse relations.In the aspect of electrical characteristics,the gain of log periodic antenna,Bobbi,input impedance and other parameters with the change of frequency can maintain a very small range of fluctuations,almost can be considered to have frequency independent.Theoretically,it is assumed that the length of the log periodic antenna can be extended indefinitely,and the antenna can be stabilized in any frequency band.But in practical design,the frequency range of the antenna is usually determined by the structure size of the antenna,that is,the high end and low end frequency 1/2 wavelength determines the maximum and minimum dipole length.Log periodic antenna has been widely used in UHF and VHF band,in recent years,with the improvement of manufacturing technique,in the higher frequency range of log periodic antenna can be applied.To approach a step to improve and improve radiation performance of a log periodic antenna,in the structure form of the traditional log periodic antenna,through changing the shape of the dipole antenna,or to the radiation oscillator is used for bending processing,thus changing the surface current distribution,in order to improve the electrical performance.Through analysis and optimization design,phase,compared to the traditional form of a log periodic antenna,optimization of log periodic antenna can not only overcome the previous axial size is too big problem,and improves the contour characteristic,and in a wide frequency band still in a certain extent,maintain the characteristics of log periodic day line directional well,high gain,has a good prospect in application.The current log periodic antenna of these forms has been in actual engineering use,and achieved good results.