Phased array technology has attracted attention in the weather radar community. This lead to the recent development of the nation's first phased-array weather radar, called the National Weather Radar Testbed (NWRT). The NWRT is an 10-cm wavelength Doppler radar managed by the National Weather Center (NWC). It provides opportunities/potentials to study and better utilize radar resources for weather surveillance, aviation control, and target detection/tracking. Its pulse-to-pulse beam steering capability allows accurate measurements in a shorter dwell-time, yielding faster data updates than obtained with a mechanically rotating dish. The NWRT has sum and difference channels that allow the study of spaced antenna interferometry for crossbeam wind measurement and sub-volume inhomogeneity/object detection.

One unique feature of the NWRT is its dual-scan (mechanical and electrical) capability. This capability has not been explored yet. Sidelobes of the NWRT's radiation pattern, with the main lobe electronically pointed +/- 45 degree from broadside, is different from that when the beam is steered to broadside. That is, the sidelobe amplitude and phase change as the beam is electronically steered. Therefore, the interference from echoes received through sidelobes will be not as coherent as the echoes received through the mainlobe (after calibration for the different electronic steering directions relative to the broadside). In another words, echoes received through sidelobes will be noise-like when the antenna steers at different electronic directions. Thus, by jointly processing the data recorded for different electronic directions (corresponding to different antenna patterns), we should be able to distinguish the echoes received through the mainlobe and sidelobes.

In this study, we propose and describe a multi-pattern technique to reduce the effects of sidelobes, and thus to improve radar data quality. The multi-pattern technique is to electronically point to several directions (corresponding to different patterns) while mechanically scanning the antenna. Hence, several sets of radar data are collected with a one mechanical scan, and then jointly processed for a set of data with reduced sidelobes. We use the measured and calculated patterns to find the optimal combination of electronic beam positions. Preliminary results show that sidelobe effects can be reduced by 5dB. Potential application of the multi-pattern technique includes removing ghost images and reducing ground clutter contamination.