Phase Modulation of Retro-Reflected Radar Echo Signal Using a Microstrip Van-Atta Array

Van-atta array is able to retro-reflect the incident signal back to the income direction and, thus, it can maintain a relatively larger radar cross-section (RCS) in a large range of incidence angles. The previous researches about van-atta array focus mainly on satellite communication and radio frequency identification (RFID). In this paper, this retro-reflective characteristic of the van-atta array is further extended to radar signal processing in a large angle range. To accomplish this, a microstrip van-atta array with adjustable transmission line is designed to add phase modulation to the retro-reflected signal. The phase modulation is achieved through the incorporation of the microwave single-pole double-throw (SPDT) switches into the array structure, which provides the retro-reflected signal ability to switch between two transmission lines separating half a wavelength. As a result, the phase modulation of retro-reflected signal can be precisely realized in a large range angle. The advantage of the designed van-atta array is that it can realize phase modulation in a large range angle of the incident signal. The simulations and experimental results are utilized to verify the effectiveness of phase modulation produced by designed van-atta array.