Broadband RCS Reduction Study Of Planar Antenna

In the modern electronic war, the stealth performance of the weaponry directly determines its battlefield survival capacity and penetration ability. Therefore, the development and study of stealth technology has got worldwide attention. The stealth performance of the weapon or aircraft mainly depends on its radar cross section(RCS), therefore how to realize the effective control of its RCS becomes a focus in the study of stealth technology. For low-observable platform, it is the antennas on the platform that restrict the stealth performance of the whole system, which makes antenna RCS reduction becomes an important problem.With the advantages of small size, low profile, easy machining and processing, the planar microstrip antenna is widely used in many fields, especially in the application of aircraft. On the other hand, the planar spiral antenna which is widely used in electronic countermeasures equipment has many advantages, such as broadband, circular polarization, low profile, simple in structure and so on. Based on the theoretical analysis, several methods of broadband RCS reduction of planar microstrip antenna and spiral antenna are proposed in this paper. Main contributions are summarized as follows:1. Based on the analysis of the induced currents on the surface of the patch antenna, a new method for patch antenna RCS reduction is proposed in this paper. This new method combines the slotting technology, short circuit probe loading technology and fractal technology. A novel microstrip patch antenna with low RCS is designed by using this new method to the reference antenna. Compared with the reference antenna, the proposed antenna can not only guarantee the radiation characteristics, but also improve its scattering performance. The designed antenna can reduce the RCS significantly in the ultra wide band of 4~16GHz and in the wide angle of iφ =-45°~ 45°.2. On the basis of the low RCS patch antenna unit mentioned above, a low RCS 2 by 2 planar microstrip antenna array is designed, which demonstrates the validity of the proposed RCS reduction method in low RCS array design. In addition, the influence factors of array antenna RCS are studied and discussed in this paper, such as the element spacing, the array configuration and the size of the floor.3. Based on the research and the understanding of the Frequency Selective Surface(FSS), two novel ultra-wideband bandstop FSS are proposed, which are called FSS1 and FSS2, respectively. Both of the FSS structures designed in this paper have ultra-wideband bandstop characteristics. The proposed FSS2 structure also has the property of bilateral steep fall. The reflection board, based on ultra-wideband bandstop FSS, can realize electromagnetic wave reflection in its working band, and electromagnetic wave transmission in the other band, which makes it possible for antenna RCS reduction design.4. An ultra-wideband circularly polarized complex spiral antenna is designed as a reference antenna, the working band of which is 2-6.5GHz. By using the proposed bandstop FSS to replace the metal reflection board of the reference antenna, the low RCS spiral antenna can be obtained. Simulation results demonstrate that the RCS of the proposed antenna is significantly reduced from 4GHz to 15 GHz, while the in-band radiation performance is preserved.