The AN/SPQ-9B is an X-Band, pulse Doppler, frequency agile radar which was designed specifically for the littoral environment. It has a very high clutter improvement factor supporting a very low false track rate in the littorals and in high clutter environments.
The AN/SPQ-9B scans out to the horizon and performs simultaneous and automatic air and surface target detection and tracking of low flying Anti-Ship Cruise Missiles (ASCMs), surface threats, and low/slow flying aircraft, UAVs and helicopters.
The radar consists of four air cooled below deck cabinets, a motor generator and one above deck Antenna unit. The antenna is designed, constructed and tested for low radar cross-section reflectivity (or signature) as required for stealth ship design and meets all MIL-STD-901D shock requirements. The AN/SPQ 9B radar is an unattended system. Preventative maintenance is scheduled for 3.5 hours per week.
The radar is installed on CVN-68, LPD-17, CG-47, WMSL-750, LHD-1, and LHA-6 ship classes. The radar is also to be installed on DDG-51 class and three Royal Australian Navy Air Warfare Destroyers. The radar has 90dB of clutter rejection in the air channel and 70dB of clutter rejection in the surface channel. This provides superior sub-clutter visibility.
Above decks, the radar uses a mechanically rotating, electronically stabilized antenna. The lightweight (1,500 lbs) antenna consists of dual planar arrays mounted back-to-back, each connected to independent transmitters and receivers. The antenna and entire system passed MIL-S-901D shock as well as shipboard shock testing on USS MESA VERDE (LPD 19).
Below decks, the radar consists of three cabinets (processor, receiver/exciter, and transmitter), Radar Set Control and Motor Generator. The processor cabinet performs all logical, signal processing, tracking, and interface functions. The receiver/exciter generates the frequencies and clocks required by the system. The receiver/exciter also contains three receivers; two receive the radar echoes from the air and surface RF received in the two arrays, and the third receives signals from the auxiliary antenna in the array. The auxiliary antenna is for the purpose of Electronic Counter-Countermeasures. The output of each receiver is converted to digital baseband I-Q data for Doppler processing in the processor cabinet. The transmitter cabinet receives the RF pulses from the receiver/exciter and amplifies them for output to the antenna. The Radar Set Control provides remote control and monitoring of radar operation in the ships Combat Information Center.
The AN/SPQ-9B radar has digital interfaces to the Aegis combat systems, the MK 34 Gun Weapon System (GWS), the MK 48 GWS, and Cooperative Engagement Capability/Ship Self Defense System.