AN/SPS-55

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**AN/SPS-55**
AN/SPS-55 antenna on USS Samuel B. Roberts (FFG-58)
Country of origin	United States
Introduced	1971
Type	Surface-search
Frequency	I band (9.05 to 10.0 GHz)
Range	greater than 50 nautical miles (92.6 km)^[1]
Azimuth	1.5º
Elevation	-10° to +10°, centered on the horizon
Power	130 kW

The AN/SPS-55 is a solid state surface search and navigation radar. It was developed by Cardion Electronics for the U.S. Navy under a contract awarded in 1971. It was originally developed for a class of ships known as Patrol Frigates, but it was also installed on numerous Cruisers, Destroyers and Minesweepers. It is an I band radar and it's antenna consists of two waveguide slotted arrays mounted back-to-back. One array provides linear polarization and the other provides circular polarization. Polarization is user selectable and the circular polarized array is more effective in reducing returns from precipitation.^[2]

1 Features
2 Platforms
3 References
4 External links

[edit] Features

Magnetron transmitter
Low noise RF receiver
Sensitivity time control (STC)
Fast time constant filtering (FTC)
Sector radiate (SR)

The effective range of the radar is from 50 feet to beyond 50 miles. It is primarily used to detect other ships, coastlines and navigation hazards.

The "Sensitivity Time Control" automatically adjusts the gain of the RF receiver from low to high based on the time elapsed from the last transmitter pulse. This helps to adjust for the fact that near by targets generate a larger return than distant targets of the same size.

The "Fast Time Constant Filtering" helps to remove targets which have a very large range size, like clouds, while passing targets with a smaller range size, like ships or aircraft.

The "Sector Radiate" allows the operator to turn off the transmitter for any sized pie shaped sector of the antenna's 360 degree rotation. An operator might want to do this to avoid detection by an enemy receiver which with a known or suspected location.