Development of MU radar real-time processing system with adaptive clutter rejection

摘要

Strong clutter echoes from a hard target such as a mountain or building sometimes cause problems of observations with atmospheric radars (Figure 1). In order to reject or suppress clutter echoes, it is effective to use NC-DCMP (Norm Constrained-Directionally Constrained Minimum Power) method, which makes null toward the direction of the clutter, if we can receive signals independently from plural antennas. The MU (Middle and Upper atmosphere) radar which located in Shigaraki, Shiga Prefecture, Japanis one of the most powerful VHF-band atmospheric radars, which can observe atmospheric motion and circulation between the troposphere and the upper atmosphere and which has contributed to a wide variety of research areas. Its operational frequency, occupied frequency bandwidth, and peak output power are 46.5 MHz, 3.5 MHz and 1 MW, respectively. The MU radar has an active phased array system. Its antenna consists of 475 elements of crossed Yagi antennas and is divided into 25 groups. Each group has 19 antenna elements. After installing the ultra multi-channel digital receiving system in 2004, we can receive signals from each 25 group, independently. It has been demonstrated that the NC-DCMP method is effective to real observation data with the MU radar, but it was processed in off-line [1].