Koden MDC-2240, Operation Manual

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Chapter 6 Principle of radar system MDC-2200/2500 Series
0093125002-02 6-2
Beam width
Antenna beam width is defined as the angle where the radiation power density is within a half of
maximum power density (-3 dB) in main lobe (also, referred to as “half value width”).
6.2 Characteristics of radar radio wave
The radar radio wave propagates slightly along the ground (primarily line of sight). This characteristics
varies depend on density of atmosphere but is generally calculated according to the formula as shown
below, considering that the distance with radar sight D is about 6 % longer than the distance with
optical sight.
Target hardness reflected
The strength of the reflected wave from a target varies depending on not only the distance from the
target, its height or size, but also its material and features. A target with a low degree of reflection or
low incident angle, such as FRP and wooden is not reflected well. Therefore, care shall be taken that
an FRP ship, a wooden vessel or an object such as sand, a sandbar and muddy cay are poor radar
targets.
Since the distance from the coastline, etc. to your ship on a radar image tends to be seen as longer
than that from the actual coastline, more caution should be used navigating around such objects..
h2
Radar radio wave
Sight line
Earth
D(NM)
≈
2.22 X ( h1+ h2)
h1
Figure 7-3 Characteristics of radar radio wave
h2 : T
arget height (m)
h1
h2
:
Antenna height (m)
6-3
Seen
Not seen
3
1
HU
Coastline on radar image
Actual (not seen)
coastline
Figure 7-4 Example of targets hard to be reflected
6-4