Beam Characteristics Analysis on Phased Array Weather Radar

The current NEXRAD system completes a volume coverage pattern in a minimum of approximately 5 minutes for 14 elevation steps. Phased array radar, with easily designed multi beams and processing of signals, offer the prospect of routinely sampling the atmosphere with volume scan rates an order of magnitude faster than the fastest(5 minutes)operational scan mode of the Doppler radars. Therefore, phased array weather radar is to form a wider transmitted lobe and receive backward radar signal using multiple narrower beams in order to save radar scanning time. The directional diagrams of the phased array antenna are derived respectively under the uniform and the non uniform circumstances, then their characteristics are analyzed and discussed. Changes of beam width and antenna gain will bring observation errors, therefore, a method of using non uniform partitioning subspace to correct the beam width and antenna gain is derived to overcome the shortcoming of phased array radar. An antenna scheme of phased array weather radar is designed using 144 array element numbers based on one dimensional linear array, meanwhile, a wider transmitted beam and multi narrow beams patterns are derived. Results show that, under the circumstances of uniform antenna caliber, side lobe level of antenna is higher. The methods of Hamming weighting can decrease the electrical level of side lobes to-25 dB, which can fundamentally meet the requirements of weather observation. The designed antenna scheme can not only save the scanning time of antenna, but also sufficiently utilize the radar resource.