Real-Time Signal Processing Data Acquisition Subsystem

Abstract

A digital signal processing sub-system has been developed for a coherent carbon dioxide laser radar system at Lincoln Laboratory's Firepond Research Facility. This high-resolution radar is capable of operating with a variety of waveforms; hence, the signal processing requirements of the sub-system vary from one application to the next, and require a sub-system with a high degree of flexibility. The primary function of the Data Acquisition sub-system is to provide range-Doppler images in real-time. Based on this objective, the sub-system must have the ability to route large amounts of digitized data at high rates between specialized processors performing the functions of data acquisition, digital signal processing, archiving, and image processing. A distributed processing design approach was used and the hardware design implemented was configured using all off-the-shelf commercially available products. The sub-system uses a high speed 24 MB/sec central bus and associated processor acting as the hub of the system. Attached to the bus is a large RAM memory buffer. Also attached to the central bus are individual processors which interface to specialized peripherals, performing the tasks of digitizing, vector processing, imaging, and archiving. The software for the complete Data Acquisition and Signal Processing sub-system was developed on a Digital Equipment MicroVAX II^TM computer. Software developed for the completed system is coded mostly in a high level language to promote flexibility, modularity, and reducing development time. Some microcode had to be used where speed is essential. All Software design, development, and testing was done under VMS^TM.