An Improved Rainfall Detection of Rain Radar Using High-Precision Circuit and Speckle Filtering

Two rain scanner radars modified from a marine radar have been operated to observe precipitation over Bandung city. The recorded observation data revealed instability in the clutter removal products. One of the main factors contributing to the instability is the precision of the pulse signal conversion results before analog-to-digital converter (ADC) sampling. This factor contributes to the increase of speckle numbers in the radar image. In this research, a high-precision circuit and speckle filtering algorithm are proposed to improve rainfall detection. The proposed high-speed and precision circuit consist of a voltage divider and a unity gain circuit utilizing a high-speed and low-noise operational amplifier. The measurement results reveal that the rise and fall times performed by the operational amplifier show a significant improvement closer to the input signal (original radar signal). It also does not produce an overshoot and presents a high percentage of settling time (steeper). The results of rain detection using radar with a high-precision circuit has higher reflectivity values until 40 dBZ. It has a higher sensitivity, indicated by the more significant amount of detected rain with higher intensity. The device also contributes to minimizing the speckle occurrence, thus easing the work of the speckle filtering. The filtering has been tested and successfully removed the speckles below 5 × 5 pixel width.