Lecture_9

# Lecture_9 - Range Tracking TWS NS212 LT Adam Sheppard y...

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Range Tracking & TWS NS212 LT Adam Sheppard

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Additional tracking dimension: So far, we have discussed tracking a target in azimuth and elevation (2D) Because we are interested in 3D tracking, we must also track the target in range When we use the word range in terms of radar, we really mean “ slant range
Range tracking method: 1. When the first echo is received, the radar calculates range via the normal method: 2. Radar attempts to “guess” the range where the second echo will occur. How? Calculating Doppler shift of the return 3. Receiver creates two “range gates” (early & late) which adjoin one another and whose range or time dimension is a little less than PW

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Range tracking method: 1. When 2. D 3. D 4. Receiver overlays its predicted range gate positions with the second echo and computes error via integration (which gate has more echo) Early gate Late gate New echo
Range Gate Area of return in each gate is computed Compares difference in areas of both gates Locations of the range gate and that of the actual target are examined Amount and direction of error between center of gate and target is determined Error voltages are generated, and the system responds by moving the gate to center it on the target Carried out by a closed-loop system similar to the servo system

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Range tracking method: Using the “gate” method allows the radar system to achieve a higher level of range “precision” than what is obtained through its normal range resolution
Last on servo systems: How many targets can a servo type tracking system (conical scan, monopulse) track at a given time? 1 2 3 more than 3 This is a major limitation and leads to a totally different tracking method for a traditional scanning radar known as “track- while-scan”

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Track-while-scan: To avoid having dozens of radars to keep
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• Spring '14
• Gate, future target position, range gate

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