9.b. Contunious Wave Radars

Question 1

What 3 factors affect BW requirements?

Answer 1

Relative velocity of target
Target fluctuations
Time on target

Question 2

Advantages and Disadvantages of CW?

Answer 2

Good SNR
Simple and cheap

Reduced dynamic range
Can’t turn down power for close targets (high power return)

Question 3

What is the Modulation Bandwidth

Answer 3

Peak to peak frequency deviation

Question 4

What is Modulation Period

Answer 4

Time between reptitions of waveform

Question 5

How does a CW radar make angular measurements?

Answer 5

A rotating radar can collect multiple positions over time and estimate the angular location with more accuracy.

CW uses:

Sequential Lobing
Conical Scanning
Monopulse

Question 6

Sequential Lobing

Answer 6

Uses two consecutive dwells on the target to refine the measurement. The more powerful return indicates the direciton of the target.

For a 3D measurement, you need to use 4 dwells.

Downside is that you spend a lot of dwell time for a single update.

Question 7

Conical Scanning

Answer 7

Very similar to Sequential Lobing but follows a circular pattern.

More resistant to jamming. Also has very high dwell time for a single update.

Question 8

Monopulse

Answer 8

Simultaneous lobing.

Question 9

Track Filtering

Answer 9

Estimating the trajectory of a track from collected measurements. (Alpha-Beta or Kalman)

Question 10

Measurement-to-track Data Association

Answer 10

Assigning a measurement to existing track, a new target, or a false signal. Difficult to determine which target is which.

Compensated with Target Tracking Algorithms.

Question 11

Target Tracking Algorithm steps and describe each.

Answer 11

Detect: Distinguish between real and false returns

Resolve: Distinguish between targets based on range, angle, or doppler

Measurement-to-track Data Association: Assign collected data to the correct track.

Track Filter: Generate estimate on the target’s trajectory.

Question 12

Ideal vs. Real CW Radar?

Answer 12

Ideally you transmit 100% of your power onto the target. In reality the power is not fully focused onto the target due to side lobes and stuff.

Question 13

Modulated vs. non-modulated CW?

Answer 13

By modulating the frequency ofthe Continuous wave, you can determine the position. The waveform pulses act like pulses on a pulsed radar and allow you to measure the return time from pulses.