8-35D: Memory Systems

Question 1

8-35D1

In a digitized RADAR, the 360 degree sweep is divided into how
many digitized segments?

A. 16
B. 64
C. 255
D. 4,096

Answer 1

ANSWER D
In a digital RADAR system, return pulse data is collected in a series of spokes. These are narrow regions of space radiating away from the rotation antenna, like the spokes of a wheel. There are 4096 radials or spkes of data for each revolution, a little over 11 spokes per degree. The return data from each of these spokes is colleged in a data bin for further processing.

Since a typical radar beam can be several degrees wide, one might wonder sy one would need so many spokes. For any poisition of the beam you could have perhaps 40 to 50 return spokes of overlapping data. This is a good question with and interesting answer.

The multiple spokes allow various bin processing methods, such as data averaging, to be used to greatly increase the effective signal-to-noise ratio of the system. Alternatively by detecting subtle changes in return time between several spokes within a single beam heading, you can derive Doppler shift (motion) of tagets, even at great distances.

The sample rate of a digital RADAR analog-to-digital converter determines the range resolution of a digital RADAR. A typical RADAR A/D converter takes 50,000 samples per second, which gives a range resolution of about 3.75 statue miles.

After the data is digitized, it’s a simple matter to process it for useful and detailed display on a modern computer video monitor, such a s using color to display return strength. Generally strong returns will be displayed as “hot” colors, while weaker teturns are displayed as “cool” colors.