Simultaneous multi-beam SAR imaging mode using phased array radar

Phased array radar based simultaneous multi-beams can be used in many fields for activities for change detection and platform location. This paper proposes a method for multi-beam antenna pattern design based on the phased array radar principle. In the proposed method, the relationships between the array structure, the direction and the width of the beams are deduced. Based on analysis of echo characters, the limiting conditions in various applications are obtained to ensure that the spectrums from different beams are not aliasing. Using the designed antenna pattern and parameters, echoes from different beams are received and separated by filtering the signal using a bank of filters corresponding to each beam. After separation, an azimuth nonlinear chirp scaling method is applied to the echoes of each beam for imaging and the imaging performance is analyzed. Simulation results show that the mode is efficient. The results also demonstrate that (1) when the platform velocity is perpendicular to the array normal line and the squint angle is not sufficiently large, the azimuth resolution is kept constant; (2) when the platform velocity is parallel to the normal line, the azimuth resolution declines sharply if the beam direction gets close to the normal line. However, if the beam direction deviates from the line, the effects of the antenna fill time becomes serious; therefore, an appropriate beam direction should be chosen.