Koden MDC-2900, Operation Manual

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Chapter 6 Principle of radar system MDC-2900 Series
0093129012-06 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 characteristic
varies depending 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.
h2
Radar radio wave
Sight line
Earth
h1
Characteristics of radar radio wave
D(NM)
h2 : Target height (m)
h1 : Antenna height (m)
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 (Fiber Reinforced Plastic) and wooden ship is not reflected well. Therefore,
care shall be taken that a FRP ship, a wooden ship 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 paid when navigating around such objects.
Seen
Not seen
3
1
HU
Coastline on radar image
Actual (not seen)
coastline
Example of targets hard to be reflected