3. Search and Detection

Question 1

CPI

Answer 1

Coherent Processing Interval

A CPI is an interval of pulses with the same parameters.

Whereas Dwell Time is the time spent on the same bearing.

Question 2

What is the purpose of a Search Radar

Answer 2

To look for targets when and where there is no knowledge of target existence.

Question 3

What is the Total Search Time?

Answer 3

T_fs = total frame search time
m = # of beam positions required
T_ad = antenna dwell time

Question 4

What are the two approaches to combining seach and track functions?

Answer 4

Track-while-scan (TWS)
Search and Track

Question 5

Track-while-Scan

Answer 5

Typically used with mechanically rotating antennas.

The beam scans the search volume and a track file is established. A new measurement is made every time the beam passes over the target.

Not suitable for tracking threatening targets because it has a low update rate, limited by the scan rate.

Question 6

Search-and-Track

Answer 6

Typically used with ESA’s.

A resource manager establishes an optimal search pattern and assigns varying amounts of dwells to tracking a target.

Question 7

How do we use probability in Threshold Detection?

Answer 7

We can assume the noise is normally distributed. We set the threshold to be some level sufficiently above the mean value of the false alarm voltages. In this way we can automatically eliminate a significant percentage of noise.

We have two PDFs: Noise and Signal Plus Noise. We must choose a threshold somewhere which encompasses as much of the Signal Plus Noise PDF and as little of the Noise PDF as possible.

Question 8

Describe m of n Detection

Answer 8

The probability of detecting n returns will increase as we increase the number of m dwells.

There is an optimal m of n depending on the P_FA and P_D PDF curves.