Radartutorial .euDwell Time and Hits per Scan
Most processes in pulsed radar are time dependent. Thus, some terms have been established to describe this time-dependence.
Figure 1: the target on the screen is a result of hits
Figure 1: the target on the screen is a result of hits
Figure 1: the target on the screen is a result of hits
Dwell Time
The time that an antenna beam spends on a target is called dwell time TD. The dwell time of a 2D–search radar depends predominantly on
- the antennas horizontally beam width ΘAZ and
- the turn speed n of the antenna (rotations per minute).
The dwell time can be calculated using the following equation:
| TD = | ΘAZ · 60 | ; in [seconds] | (1) |
| 360° · n |
Hits per Scan
The value of hits per scan m says how many echo signals per single target during every antenna swing are received. The hit number stands e.g. for a search radar with a rotating antenna for the number of the received echo pulses of a single target per antenna turn. The dwell time TD and the pulse repetition time PRT determine the value of hits per scan.
| m = | TD | = | ΘAZ · 60 | (2) |
| PRT | 360° · n · PRT |
So that radar equipment can evaluate the target informations with sufficient precision, hit numbers are between 1 and 20 as necessary, which depends on the radar set operating mode.