﻿ Radar Basics - Dwell Time and Hits per Scan

#### Dwell 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.

Publisher: Christian Wolff
Text is available under the GNU Free Documentation License, and the