www.radartutorial.eu Radar Basics

Minimal Measuring Range

Rmin

Figure 1: The Radars “blind range”

Rmin

Figure 1: The Radars “blind range”

Rmin

Figure 1: The Radars “blind range”

What is radar waveforms minimum range?

Minimal Measuring Range

Monostatic pulse radar sets use the same antenna for transmitting and receiving. During the transmitting time the radar cannot receive: the radar receiver is switched off using an electronic switch, called duplexer. The minimal measuring range Rmin (“blind range”) is the minimum distance which the target must have to be detect. Therein, it is necessary that the transmitting pulse leaves the antenna completely and the radar unit must switch on the receiver. The transmitting time τ and the recovery time trecovery should are as short as possible, if targets shall be detected in the local area.

Rmin = c0·(τ + trecovery) in [m]

2

Targets at a range equivalent to the pulse width from the radar are not detected. A typical value of 1 µs pulse width of a short range radar corresponds to a minimum range of about 150 m, which is generally acceptable. However, radars with longer waveforms suffer a relatively large minimum range, notably pulse compression radars, which can use pulse lengths of the order of tens or even hundreds of microseconds. Targets at ranges closer than this minimum are said to be eclipsed.