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FAS Project on Intelligence Reform

Common High Bandwidth Data Link - Surface Terminal (CHBDL-ST)

The Common High Bandwidth Data Link - Surface Terminal (CHBDL-ST) will support the Navy's efforts by providing a wideband, full duplex, digital data communications link between the ship and the airborne sensor platform equipped with the Common Data Link Airborne (CDL A/B) subsystem. The CHBDL-ST is not designed to counter any specific threat, instead it is intended to operate in the threat environment.

CHBDL-ST is a communications terminal that provides full duplex data communications (at line-of-sight ranges) between aircraft, equipped with a Common Data Link Airborne (CDL A/B), and shipboard users’ signal processing equipment. The terminal receives variable data rates with an encryption and decryption capability in accordance with the interface specifications of the supported systems. The CHBDL-ST transmits user commands to the CDL A/B for Battle Group Passive Horizon Extension System (BGPHES) or JSIPS-N (ATARS) Prime Mission Equipment (PME) in the aircraft. CHBDL-ST receives link status and user mission data in the downlink and provides this mission data to the BGPHES-ST and JSIPS-N shipboard processors. The command uplink has Low Probability of Intercept (LPI) characteristics based upon parabolic antenna directivity, signal modulation format and transmitter power output control. The system is capable of operating only one link at a time.

The CHBDL-ST is comprised of two major functional subsystems, the Expandable Multi-Link Processor (EMLP) subsystem, and the Antenna/Radio Frequency (ARF) subsystem. The EMLP Subsystem consists of EMLP Group I, located in Radio or CIC spaces, and EMLP Group II located in the BGPHES-ST and JSIPS-N equipment spaces. The EMLP subsystem performs data formatting, modulation/demodulation, and Link Control (LC) operations which are divided functionally between the Command and Control Processor (CCP), the Modem(s), and the Link Switch (LS). These functional areas allow a system operator to input mission requirements, select a link configuration, and allocate CHBDL-ST resources for link operation.

The CHBDL-ST system operator uses the CCP to monitor link status and perform on-line testing of the equipment. The LC functions consist of data formatting and single link control. The ARF Subsystem consists of two equipment groups, the Shipboard Antenna (SA) Group and the Shipboard Antenna Electronics (SAE) Group. The SA Group, located above decks, is divided between two antenna systems. The shadowing effects imposed by the ship’s superstructure dictate the use of two independent antenna systems with handover coordination to provide 360 degrees of azimuth tracking. The two SAE Groups will be located in sheltered spaces between the EMLP Subsystem and each antenna. The EMLP and ARF are connected within the ship by an internal Fiber Optic Interface (FOI). External interfaces with CHBDL-ST exist between the EMLP subsystem, and the BGPHES-ST and JSIPS-N systems, where user commands originate and the PME sensor data is processed within the ship.

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Created by John Pike
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Updated Friday, February 11, 2000 12:31:18 PM