The Erieye is an active, pulse-Doppler, S-band radar which has a range of 400 km. Designed by the Swedish firm Ericsson Microwave Systems, the Erieye is used onboard the Saab 2000, Saab and the Brazilian Embraer E-99. The Erieye radar is equipped with a fixed electronically scanned antenna, which is mounted on the fuselage, providing superior resolution over rotodome radars. Erieye radar can detect and track air and sea targets out there on the very distant horizon, and sometimes beyond this due to anomalous propagation. Typical detection range against fighter-sized targets is approximately 425 km, in a 150° broadside sector, both sides of the aircraft. Outside these sectors, performance is reduced in forward and aft directions.
The Erieye radar is fitted with 200 two-way transmit/receive modules that combine to produce a pencil beam, steered as required within the operating 150° sector each side of the aircraft (one side at a time). It is understood that Erieye has some ability to detect aircraft in the 30° sectors fore and aft of the aircraft heading, but has no track capability in this sector. The Erieye also features adaptive waveform generation (including digital, phase-coded pulse compression); Signal processing and target tracking; Track While Scan (TWS); Low sidelobe values (throughout the system's angular coverage); Low- and medium-pulse repetition frequency operating modes; Frequency agility; Air-to-air and sea surveillance modes; and Target radar cross-section display. Today, the Erieye is manufactured by the firm Saab Microwave Systems.