Studies On Optical Phase Shift Of Phased Array Radar

As an important access to information, radar is an essential weapon for modern warfare. As a result of phased-array antennas in radar offer great potential for observing stealth targets, small and low-attitude targets under the condition of strong noise interference, its development gets widespread attention at home and abroad. In order to provide an accurate monitoring and target tracking, radars usually require precise pointing. The key of precise pointing is the control of phase difference between adjacent units in phased-array antennas. So the phase shifter is of great research value. Because the optics have a lot of advantages such as anti-electromagnetic interference, low. loss, small volumes and light weight, the technology of photonic RF phase shifter using optical and optoelectronic devices has become a research focus in recent years.In this dissertation, the theoretical principles and technical characteristics of the phased-array antennas are analyzed, including the relationship between the phase difference within adjacent array elements and the antenna beam pointing angle. The dissertation studies the technology of photonic RF phase shifter based on optical true time delay (OTTD), vector sum, heterodyne mixing, including their working principle, advantages and disadvantages and technical solutions. The first option can solve the problem of squint phenomenon in broadband beamforming networks while the latter two can accurately control the narrowband operations with a relatively simple system structure and adjustment method.A photonic RF phase shifter based on SSB using dual-drive MZM is proposed according to the requirements of phase shift and change of amplitude. It can be seen from the theoretical derivation that this structure can change the phase shift of RF signals linearly by adjusting the bias voltage of PM. The result of VPI system simulation shows that this structure can realize a range of phase shift greater than360degree and little amplitude fluctuation using convenient adjustment.A photonic RF phase shifter with optical power control which combines the technology of optical phase shift and the technology of power control is also proposed. The result of MATLAB simulation shows that this structure can offer accurate phase shift with low sidelobe level. As an important parameter of phased array radar system, the sidelobe performance determines the ability of anti-interference. So the proposed phase shifter with power control can improve the performance of phased array radar effectively.