Design of X-band Doppler Weather Radar Servo System

Abstract

This paper presents a weather radar servo system based on DSP chip. In this system, a set of high-precision shaft angle digital coding modular circuit is designed with a resolver, a monolithic resolver-to-digital converter and an excitation signal driver, and meets the requirements of precise angular-position information measurement of the DC motor shaft. The shaft encoder information mapped on DSP’s external data memory space can be directly accessed by its parallel interface. With comparing technical characteristics of unipolar and bipolar PWM, the unipolar PWM technique is chosen and applied in this design, and its pulse width and direction signal are generated by the DSP chip. In order to overcome the limitations of the existing half-bridge driver in applications, a special unipolar PWM logic distribution and inverter circuit is designed, which has ultimately solved the problem of shoot-through in an H-bridge configuration. For scan types of a weather radar servo system, especially antenna angular positioning, the digital PI regulator with saturation algorithm is employed in the design, which meets the accuracy requirements of angular positioning and uniform rotation. At present, the servo system has been successfully applied to X-band Doppler weather radar named WXR-MD-10, which is designed by Radar System Lab of Chengdu University of Information Technology. And it had been installed at the Meteorological Bureau of Weining County, Guizhou Province in July 2011, and put into operation.