Wide-angle scanning planar phased array antenna

Abstract

The phased array antenna has been widely used in many applications due to the high speed and the accuracy of scanning. Low profile and easily integrating are required under many situations. Wide-angle scanning is expected, especially in low elevation target searching. There are two main conditions in the implementation of the wide-angle scanning. On the one hand, the beam-width of microstrip antenna element is wide enough. On the other hand, the coupling between elements which will affect the impedance matching between the elements and ports should be properly controlled while the phased array antenna is scanning to the wide angles. Many improvements have been done to enlarge the scanning angle. There are four main methods to broaden the scanning coverage. First, enlarging the beam-width by using pattern reconfigurable antenna is widely used. There are usually three working modes, left mode, right mode and broadside mode, which are implemented by changing the working status of the PIN diodes or switches. The phased array which is composed of the pattern reconfigurable antenna can scan from −70 ° to 70 ° approximately [1]. Secondly, the antenna array based on the surface wave has wide-angle scanning characteristic. The surface wave is usually regarded as adverse effect which enlarges the coupling between elements. However, in the planar phased array, the surface wave can be used to enlarge the scanning range. The null radiation will be compensated by controlling the propagation of surface wave. The controlling of surface wave is achieved by leading the subwavelength structure like HIS which is similar with the photonic crystal. This kind of array antenna is able to scan from −85°to 85°[2]. Thirdly, according to the mirror theory, there are two types of antenna which can be used to realize the wide-angle scanning. One is putting the electric current parallel to the magnetic conductor closely (JpM). The magnetic conductor is realized by metamaterial consisting of the sub-wavelength structures. The another one is putting magnetic current parallel to the electric conductor closely (MpE). Based on the equivalent theory, the magnetic current can be obtained by grounding three sides of the microstrip antenna. The phased array antenna which is composed of the JpM or MpE antenna has excellent performance of scanning through the whole upper half space theoretically [3] [4]. Lastly, the algorithm based on the time reversal (TR) can take the coupling into account to optimize the wide-angle scanning array. The aperture distribution can be obtained adaptively [3]. In conclusion, a wide-angle scanning phased array can be obtained by utilizing the methods mentioned above. However, there are still many challenges in this field. More attention will be paid to the wide-band 2D wide-angle scanning phased array research.