Ships rely on S-Band and X-Band frequency radar system for navigation and detection of incoming ships or land obstacles to avoid a collision. The radards use Rotating Antennas to discover the surrounding area of the ship. It can detect targets and display the information. Radar is an important component of every ship. It ensures ships safety across sea and near shore. In Commercial Ships, radars are integrated to form a complete system of Marine Instruments Duplexer - The use of a pulse technique to detect aircraft and ships was proposed by NRL's Leo Young in 1933. His colleague, Robert M. Page, made important advances over the next few years in the area of transmitters and receivers. He eventually developed the highly important duplexer, which permitted an antenna to be used for both transmitting and receiving. Combined with the duplexer, the pulse technique did away with the separate receiving and transmitting antennas that early radar developers had used. Submarine Radar - In 1940, NRL developed submarine radar. This radar enabled a submarine to rise to periscope depth and search for hostile aircraft before surfacing. Aircraft could be detected by the radar out to a range of 20 miles. At that time, this was considered adequate to allow the submarine to submerge before becoming vulnerable to the aircraft's weapons. This radar became popular with submarine skippers during World War II; units were installed in submarines as quickly as they became available-more than 400 were produced. The Laboratory later perfected a directional radar antenna for use with the Western Electric Radar System. It was effective enough to be used as a fire-control instrument, allowing several enemy ships to be torpedoed without the submarine being seen.
The PPI radar display as originated by NRL. The PPI is now used worldwide in detection, navigation, air traffic control, and object identification radar systems.
Plan-Position Indicator - To provide a polar-coordinate map-like display of targets, NRL originated the radar plan-position indicator (PPI)-the well-known radar scope with the round face and the sweeping hand-between 1939 and 1940. The PPI is now universally used by military and commercial interests around the world for the display of radar information for such functions as air and surface detection, navigation, air traffic control, air intercept, and object identification. Naval and Coast Guard Radar - These ship borne radars search the surrounding radars and provide 3D surveillance. It detects small targets in a long range while in severe weather. It uses both X and S band frequency mechanisms to ensure high reliability on detection of small objects in distance. Solid radars requires minimal maintenance routines and uses low power patented pulse sequence. Naval Fire Control Radar - Fire control radars are designed to provide information to the navy officers on how to control their weapons to hit a target. They use radio waves to accurately track, target and provide the location to avoid losing the target. VTS and Coastal Surveillance Radar - This type of radar systems provide Vessel Traffic Management Services (VMTS) and ships with early warning of incoming targets. They ensure safety and security along the ports, coastlines or on waterways. These radars provide information to the Navy Officers on ships, remotely piloted vehicles and objects on a long range.

Commercial and Merchant Marine Navigation Radar - This marine radar provides a safe navigation watch. The radar is used to identify, track, position vessels and safely navigate the vessels from one point to another. The radar tracks the exact range of target in order to avoid collision. It uses X-band frequency to sharpen the image of the target.

High Frequency - Modulated Continuous Wave (HF-CW) Radar - This kind of radar changes the frequency with time. To get the actual range of the target, the frequency of the transmitted and received  frequency is recorded. The radar model changes the frequency in a linear manner to give room for up and down frequency alternates.

Electronic Scanned Phased Array Radar - In this type of Radar, a scanned phased array antenna beam placed on the direction scans the area without moving the entire navigation system. The beam switching enables the radar to detect incoming targets simultaneously.

Simple Pulse Radar - This is the most common type of radar which consists of short duration pulses to monitor any moving objects. It uses Doppler Frequency to accurately measure the distance of the moving objects.

3D Radar - This radar measures the exact location of the target object in two dimensions. It can determine the angle of elevation on the target object. Has an automatically or manually rotated antenna to determine the target range.