Both radar and sonar are active systems; they provide a source of energy (electromagnetic and acoustic, respectively) to "illuminate" the terrain and can therefore operate both day and night. Energy returned from the terrain is detected by the system and recorded as images. Radar operates at much higher frequencies than does sonar and is used to create images of land areas above sea level (electromagnetic waves are strongly attenuated in water). The lower-frequency sonar signal is transmitted through water and is used to create images of the seafloor.

High-speed signal processing is critical to the function of both radar and sonar systems. To meet the demands of radar and sonar system designs, Altera offers digital signal processing (DSP) power in its high-density Stratix®  II and Stratix families.

Radar

Radar systems provide position and velocity of objects with respect to the radar unit. In some advanced systems it is possible to determine the shape of the object. The military requires all-weather, day-and-night imaging sensors to supply reconnaissance, surveillance, and targeting information. Radar systems demand tremendous amounts of DSP power, especially when used for target tracking and designation purposes. Some radar system applications include:

• Airborne fire control
• Ground-based air surveillance systems with an emphasis on VHF/UHF radar
• Maritime airborne early warning
• Bistatic radar
• SAR & SAR-image processing
• Naval multi-function radar

Sonar

Both surface vessels and submarines use sonar for navigation, obstacle avoidance, mine detection, salvage, and underwater surveillance. Unique receiver/amplifier designs require FPGAs to maintain high-levels of DSP in order to detect difficult targets obscured by background clutter. Anti-submarine warfare (ASW) is sonar-based, and the ASW applications include:

• Acoustic decoys
• Suspended array cables
• Helicopter-dipping sonar
• Torpedo guidance
• Mine-sweeping operations
• Surveillance & weapon ranges
• Air- & sea-towed antennae

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