Koden MDC-5004, Operation Manuals

Page: 137 / 192

MDC-5000 Series Chapter 8 Principal of radar system
0093153004-00 8-1
Chapter 8 Principal of radar system
8.1 What is radar system?
The radar is a navigation device that transmits a very high frequency radio wave referred to as
microwave from the antenna. The radar then receives the radio wave reflected by target(s) (e.g. other
ship, buoy, island, etc.) via the same antenna and converts the received radio wave to electronic
signals and sends these signals to the Processor unit. The radar makes it possible to find objects
(targets), such as other ships, rocks or coastline, not seen by eyesight at night or in fog and allows
ships to avoid these potential hazards. As the antenna transmits during 360-degree rotation, it is
possible to see the current surrounding situation around your ship at a glance.
The microwave radiated from the radar is referred to as pulse wave and the transmitting and receiving
of these waves is alternated. Up to thousands of pulse waves are transmitted and received during one
rotation
The typical radar antenna is of parabolic type or slotted array type and its performance is essential for
good radar performance. Some of factors affecting the quality of the target returns are antenna beam
width and side lobe level. The narrow beam width provides high resolution for angular orientation to
distinguish objects and the low side lobe level reduces false image effect.
Radar wav e
Antenna
(during rotating)
Own
ship
Other
ship
Buoy
Radar display
Side lobe
The main lobe means the strongest radiated beam sent from the specific antenna, and the other
weaker beams, are referred to as a side lobes. A side lobe level is a difference between the largest side
lobe level and main lobe level.
Main lobe
Beam width
Side lobe lev el
Side lobe
Antenna pattern
Antenna