Signal processing schemes for Doppler global velocimetry

Two schemes for processing signals obtained from the Doppler global velocimeter are described. The analog approach is a simple, real-time method for obtaining an RS-170 video signal containing the normalized intensity image. Pseudocolors are added using a monochromatic frame grabber producing a standard NTSC video signal that can be monitored and/or recorded. The digital approach is more complicated, but maintains the full resolution of the acquisition cameras with the ability to correct the signal image for pixel sensitivity variations and to remove background light. Prototype circuits for each scheme are described, and example results from the investigation of the vortical flow field above a 75-deg delta wing are presented.