Research On The Wideband Radar Cross Section Control Methods Of Antenna

With the rapid developments of radio technology and radar detection technology,the lethality and viability of military weapons in modern battlefields are facing serious threats.In order to increase the survival rate of the targets and master the initiative of the war,the researches and applications of stealth technology are particularly important.Generally,the lower the scattering power is,the smaller the radar cross section(RCS)is and the better the stealth performance of the target will be.In various wireless electronic devices,antenna must transmit and receive electromagnetic waves efficiently and stably for the normal communication and operation of the system.However,the antenna also has a strong scattering property,and its stealth performance is crucial for the military platform.And in the pursuit of antenna stealth performance,it is necessary to take into account the electrical performance of the antenna.Therefore,how to achieve the stealth property to the enemy detection system without affecting the normal operation of the antenna is an urgent problem.In this dissertation,starting from the scattering theory of the antenna,the RCS control technology of the antenna is studied.For various antenna types,including Vivaldi antenna,microstrip patch antenna,microstrip array antenna,and slot-coupled patch antenna,reasonable antenna RCS reduction schemes in a wide frequency band are proposed.The main contents include:1.Starting from the analysis of the substrate integrated waveguide(SIW)theory,the SIW with oblique bending structure is loaded on the Vivaldi antenna to control the antenna scattering based on the existing technology.First,half mode substrate integrated waveguide(HMSIW)structure is loaded in a region where the intensity of the antenna radiation current distribution is weak,and the effect on the radiation performance of the antenna is reduced as much as possible.Using the guiding effect of HMSIW on energy,the scattering energy is guided to the forward direction,thereby achieving the reduction of the backward RCS.Then the end of the SIW structure is changed to 45° corner.Scattering energy is directed to the lateral side of antenna plane and the RCS reduction in a specific angular domain is achieved due to the SIW with the oblique bending structure.This method can achieve RCS reduction within the antenna operating frequency range(5-12GHz),and the average reduction in the whole band is more than 10 d B.In addition,the scattered energy is redistributed to the antenna side at a certain frequency point,and the forward RCS and backward RCS are reduced,achieving the control of antenna bistatic scattering.2.By using the metal meandering lines and the vertical metallic via-holes in dielectric board,a 2.5D miniaturized frequency selective surface(FSS)is designed.The final size of FSS unit is 0.042?×0.042?(? is the wavelength in free space at the resonant frequency of FSS).The equivalent circuit method is used to analyze the miniaturized FSS.The transmission characteristic curve of the equivalent circuit is simulated in ADS and compared with the HFSS calculation result.The miniaturized FSS is used to replace the partial metal floor of the microstrip antenna to achieve out-of-band RCS reduction.This method can achieve RCS reduction in a wide frequency range of 1-5GHz(except the antenna operating frequency band),and the RCS reduction has a certain angular stability and polarization stability under incident wave with different polarizations and different angles.3.A broadband absorbing material is proposed.And the working principle and the design method are analyzed in detail using the equivalent circuit method.The absorbing material is loaded onto the slot-coupled patch antenna to achieve out-of-band RCS reduction of the antenna.In order to reduce the in-band RCS,microstrip resonators are loaded on the antenna with a certain distance from the radiation patch.Besides,a broadband absorbing material with transmission characteristic in a specific frequency band is designed.The floor of the traditional absorbing material is a metal plate.By replacing the metal plate with a band-pass FSS,the electromagnetic wave transmission in the FSS operating frequency band is achieved,while the material still has the absorbing characteristic out of the FSS operating frequency band.Then the material is loaded onto a microstrip array antenna as a coating.The operating frequency band of the antenna is the same as the transmission band of the material,and a good RCS reduction can be achieved out of the antenna working frequency band.In addition,microstrip resonators are loaded around the microstrip patch array to reduce the in-band RCS.This method has little effect on the radiation characteristics of the antenna,and achieves a wideband RCS reduction of 1.5-13 GHz.4.Based on the concept of quasi-fractal,two units with a 180° reflection phase difference are proposed.Using the 180° reflection phase difference between two units,the reflection waves in the normal direction cancel each other,thereby achieving RCS reduction.Due to the use of a quasi-fractal structure,the 180° reflection phase difference bandwidth is greatly increased and the cell size is reduced.The chessboard is arranged with the two units and the RCS is compared with the same size metal plate,verifying the RCS reduction effect of the chessboard structure.By changing the iterative unit of the quasi-fractal structure,a second type of artificial magnetic conductor(AMC)structure is designed,further increasing the 180° phase difference bandwidth between the AMC and PEC.The second AMC structure is properly applied to a slot-coupled patch antenna.A good RCS reduction in a wide frequency range of 6-30 GHz is achieved,and the reduction frequency band covers the operating frequency band of the antenna.Besides,the design has no effect on the radiation characteristics of the antenna.