Singly curved phased reflector for RCS reduction

다국어 초록 (Multilingual Abstract)

This thesis discusses the singly curved phased reflector for reduced RCS pattern, which has minimized RCS level at boresight with a null by phase cancelation and the lowered RCS level of main beam by splitting the main beam into multi directions. Considering the reduced level of boresight and main beam compared to the same sized reference PEC, this proposed multi-beam reflector can be adopted in the bi-static radar environment.
The proposed reflector is designed on singly curved surface, which is a cylindrical arc shaped. Using circular array theory, it is possible to synthesize a desired RCS pattern. The reflection phases are calculated to synthesize steered beam pattern by considering parameters that are composed of element position, element width, and curvature (or curvature radius). In this methodology, it is needed to compensate the reflection phase due to different path lengths between wave front of normally incident plane wave and each element by adjusting the square patch which has optimal reflection phase on the position of each cell.
The proposed reflector is multi-beam reflector, which have different phase distributions at each row for different steering angle. It is designed through an intermediate stage of a single and dual-beam reflector. The behaviors of the designed reflectors are verified through full-wave simulation and experiment. The reflectors are designed in the frequency of 10 GHz and it has a size 240×180 mm2 (8×6 λ2) with the curvature k=3.3, 6.67 and 10. From the measured results, the proposed reflectors reduce the reflected power by 17, 12 and 11 dB at boresight with respect to the same size of PEC with curvature k=3.3, 6.67 and 10, respectively. Simulated bandwidth is 4.75%, 3.8% and 6.8% with the same order as above, respectively. It will be a future work due to the narrow bandwidth.
Although the conventional reflectors for the RCS reduction cannot control the reflection angle, the proposed reflector can change the reflected angle to control the RCS pattern by adjusting the phase and distance between neighboring elements. The proposed reflectors are cylindrical arc shape. So, it is expected that the proposed reflectors can be applied to singly curved surfaces which are components of military platform for RCS reduction and the conformal reflector antenna system as a representative with small mass, low manufacturing cost, and ease of fabrication.