Research On RCS Reduction Methods Of Vivaldi Antenna

Nowadays,the development of radar detection technology has led to an increasing threat to combat systems.In order to reduce the possibility that the combat systems are detected by radar,it is important to improve the stealth performance of combat systems.In fact,it means lower radar cross section(RCS).Vivaldi antenna is widely used in airborne fire control radar of aircraft due to wide bandwidth and high gain.Vivaldi antenna is an important scattering source for aircraft,so it is important to reduce the RCS of Vivaldi antenna.On the premise of minimizing the negative impact on the radiation performance of Vivaldi antenna,RCS reduction of Vivaldi antenna is achieved by shape modification and passive cancellation in this thesis.The work in this thesis are listed as follows:1.A low-RCS Vivaldi antenna based on shape modification is designed.Firstly,the radiation current and scattering current distributions of Vivaldi antenna are analyzed.The RCS reduction is achieved from 8 GHz to 11.5 GHz by removing the substrate with larger scattering current and smaller radiation current.Secondly,in order to reduce the RCS in Xband which is working frequency band of radar,the resistors are further loaded on the edge of the antenna and rectangular slots are etched on the patch.The resistors can absorb the scattering energy to further reduce the RCS of the antenna.Rectangular slots can reduce the RCS of Vivaldi antenna on one hand,on the other hand can improve the gain of Vivaldi antenna because rectangular slots can suppress the current at the edge of the Vivaldi antenna and make the current distribute in the exponential tapered lines.Finally,a low-RCS Vivaldi antenna with good radiation performance is obtained.Compared with reference Vivaldi antenna,the RCS reduction of designed Vivaldi antenna is achieved from 8 GHz to 12 GHz under y-polarized incident wave,with a maximum reduction value of 17.8 dB.The average reduction is 8.8 dB.Besides,the realized gain of the designed Vivaldi antenna is improved,with a maximum improvement of 1.1 dB.2.Two low-RCS Vivaldi arrays based on passive cancellation are designed.Firstly,the antenna elements with different feed structures can have different reflection phases.Besides,the reflection phase of antenna can be further adjusted by loading substrates of different dielectric constants.Based on above narration,two Vivaldi antenna elements are designed which have different feed structures and different substrates of different dielectric constants loaded on the top of the antennas.The two antenna elements have similar reflection magnitudes and different reflection phases from 6.4 GHz to 11.8 GHz.The RCS of Vivaldi array composed of above two antenna elements is reduced from 6.4 GHz to 12.4 GHz.And the Vivaldi antenna array shows good radiation performance.Secondly,by loading metal strips of different lengths,the reflection phase of antenna element can be further adjusted.Based on above narration,two Vivaldi antenna elements with different feed structures and different metal strips of different lengths on the top of the antenna are designed.The reflection phase difference between the two antenna elements is between 143° and 217° in 5.1-11.9 GHz.The RCS of Vivaldi array composed of above two antenna elements is reduced from 4.8 GHz to 12.6 GHz.The Vivaldi antenna array shows good radiation performance.3.A low-RCS Vivaldi array is designed based on shape modification and passive cancellation.Firstly,the different antenna elements with different feed structures and different metal strips are respectively fed with power dividers to form different subarrays.The two different subarrays have similar reflection magnitudes and different reflection phases from 5.2 GHz to 11 GHz.Secondly,the different subarrays are arranged into the array,and RCS reduction of the array is achieved from 5.2 GHz to 11.4 GHz.Thirdly,in order to reduce the RCS in X-band which is working frequency band of radar,the shape of the above array is further modified.The final proposed Vivaldi array is obtained by removing the part with larger scattering current and smaller radiation current.The RCS of the proposed array is reduced from 5.2 GHz to 12 GHz.The RCS reduction bandwidth is 79%.The Vivaldi array shows good radiation performance.