The history of Marine radar and structure

Marine radar is installed on ships for navigation avoidance, ship positioning and navigation in narrow waterways. It is also known as Marine radar. Marine radar provides necessary observation means for seafarers when the visibility is bad. Its appearance was a significant milestone in the development of navigation technology

In 1904, German engineer Jules meyer made a device that could emit and receive electromagnetic waves to detect Marine radar of ships. However, due to the operating distance of less than 1 mile, it was not taken seriously. The Normandy, a French liner, was the first to install navigational radar in 1935. Its antenna could not be rotated to detect icebergs in front of it.

In the late 1930s, shipboard meter-wave air-search radars were made in Britain and the United States. During the second world war, the centimeter-wave radar was developed. In 1940, the Englishman Randall and bout made a cavity magnetron, which solved the problem of microwave source. In 1941 the United States first developed a pulsed microwave sea surface search radar with a planar position display. This kind of radar played an important role in the anti-submarine warfare in the second world war. After the war, it was used as the merchant ship navigation radar to ensure the safety of navigation. In the late 1960s to the early 1970s, automatic radar plotter appeared, which further played the role of radar in avoiding collision and was widely used

Antennas: early parabolic reflector antennas have been replaced by waveguide slot antennas. The radiation of antenna is dominated by horizontal linear polarization. In order to improve the detection ability of radar in rain and snow, some antennas are equipped with circular polarization devices. Transmitting and receiving generally share an antenna, which is converted by a duplex (transceiver switch). Continuous ring antenna by motor drive, 360 ° sweep. In order to ensure the azimuth measurement precision and azimuth resolution, level of antenna beam width is narrower, a lot of 3 cm radar sailing within 1 °. To prevent ship swaying missing target, vertical beam width is wide, about 25 °

Transmitter: pulse system is adopted. The pulse width is about 0.05 ~ 2 microseconds. Short pulse is used to improve range resolution. A longer pulse is used to increase the operating distance. The working bands are mainly x-band (9320-9500mhz) and s-band (3000-3246mhz), which are usually called 3cm radar and 10cm radar respectively.

History and construction of ship radar

In the case of the same antenna size, the former has higher azimuth resolution, which is beneficial to the close-range detection. The latter is less disturbed by rain and snow clutter and wave clutter, and the attenuation of electromagnetic wave through the rain area is also small. If the transmitting power is the same, the remote sensitivity is higher, which is conducive to remote detection. Radar at the same time the installation of these two bands, can learn from each other.

Receiver: it adopts direct mixing superheterodyne, and is equipped with wave interference suppression circuit and rain-snow interference suppression circuit. In order to prevent radar interference in the same band, some radars are equipped with anti-same-frequency asynchronous interference circuits. Transmitter and receiver are assembled in the same cabinet, collectively called transceiver

Display: display the plane position by the distance azimuth polar coordinates, the scan line and the antenna rotate synchronously, there are a number of range range to choose from. The range may use the movable range mark or the fixed range mark; The electronic azimuth line or the mechanical azimuth circle can be used for azimuth measurement. The high brightness display that appeared in the 1970s could be viewed by several people at the same time in the normal light of the bridge during the day without an optical hood. Some use color display, with different colors to represent different content, make the screen screen more eye-catching.