RADS system deployed on Coast Guard C-130.

Radar Acquisition and Display System Summary

The Radar Acquisition and Display System (RADS) is a moveable system designed to record and display data from a research Doppler radar with polarization diversity. Physically, the unit consists of a 6U VME chassis as well as an external color monitor, keyboard and mouse. Connection to the radar is made at four levels: radar timing signals (trigger, polarization control and range gates), receiver (in-phase and quadrature video, log output from both horizontally and vertically polarized receivers), synchro for monitoring azimuth and elevation, and ethernet for communicating with a resident radar computer that controls the antenna.

RADS contains the following VME cards: Radar Timing Generator (RTG), SPARC-based CPU, DSP (Digital Signal Processing) card containing four TMS320C40 DSP chips, a four-channel 20 MHz A/D card with 1 MB buffer memory, and a synchro-digital card. The chassis also contains a hard disk drive, a CD-ROM drive, and two 8mm cartridge tape drives. Solaris 2.5, a version of UNIX, is run on the CPU; no operating system is used on the DSP card.

The operator controls RADS through a GUI (Graphical User Interface) window on the color monitor. All radar parameters may be viewed, and certain subsets of parameters may be selected to be shown simultaneously on the screen. Thus if one is in Pulse-Pair mode, only those parameters that are pertinent to that mode, and that change frequently in that mode, will be displayed. In addition, because of the large number of parameters (> 80), they are grouped by primary function (timing, calibration, scanning, transmitter, receiver, data processing and housekeeping), and may be displayed in groups this way as well. The operator may select functions through "buttons" on the GUI, and in this way controls processing and recording.

Plots, such as Doppler spectrum or delta-k spectrum, as well as areal displays, such as PPI, RHI or B-scan are shown on the color monitor. Numerous fields may be selected for display in the areal formats, depending on the processing mode that has been selected. Since all processing modes are programmed, it is relatively easy to add additional modes. The following modes have been implemented: time-series, power spectrum, pulse-pair, and pulse-pair with differential phase and HV correlation. There are four variations on this last mode, depending on the algorithm used to calculate HV correlation, and the fields desired.

The RTG generates all timing parameters under program control and can generate pairs of pulses for use with the pulse-pair algorithm. Therefore all timing parameters, such as intra- and inter-pair spacing and range gate delay, spacing and number are completely programmable within the confines of the radar being driven and the processing and recording speed of RADS. The speed limitations of RADS depends on the mode that is being used. In general, modes such as time-series and power spectrum that have little or no data compression, are limited by recording speed. Modes such as pulse-pair that have much data compression are limited by processing speed.

Specifications

References

Campbell, W. Carroll and J. Gibson, 1997: A Programmable Real-time Data Processing and Display System for the NOAA/ETL Doppler Radars, Proceedings of the 28th Conference on Radar Meteorology, Austin TX, American Meteorology Society.