Expanding the use of aerial downlinks

April 04, 2012 // By John Payne IV, IMT Chief Technology Officer
Today, airborne downlinks are no longer limited to strategic command applications. More and more, first responders, fire departments, EMS, CBP and others are employing airborne downlinks to meet a diverse array of needs. Through the use of digital downlink technology, these systems are easier to use, eliminating the need for highly trained technical personnel to operate them. They also now have full-featured infrared cameras and secure digital COFDM transmitters, allowing users to share the video intelligence, surveillance, and reconnaissance information across multiple organizations and agencies.

At Integrated Microwave Technologies, LLC (IMT) we developed a turnkey approach to aerial downlinking for military and government users who need IP streaming and receivers for decoding and encoding, as well as installation and troubleshooting.

The situation

Whether the downlink platform is a fixed-wing aircraft, helicopter, unmanned aerial vehicle (UAV) or even a rapidly deployable blimp, these vehicles carry with them an arsenal of high-quality imagers. These imagers can be daylight cameras, infrared cameras or other sensors capable of chemical or biological detection. Infrared imagers are able to see through smoke from an industrial fire or track a perpetrator under the cover of darkness. Depending on your operational need, these platforms can be positioned far away from the situation — covertly spying on a perpetrator — or right on top of it.

The equipment

The video from the aerial platform has a tremendous value to operations. Sharing this effectively requires a digital downlink transmitter. The transmitter accepts the high definition video from the imager or other onboard sensor and compresses the video so that it can be transmitted in an effective manner. The compressed digital video is then encrypted using a universal standard AES encryption method known as BCRYPT. The encrypted signal is then applied to a COFDM RF modulator and transmitter, which takes the data intended to be transmitted and converts it into a format optimized for aerial downlink transmission. The transmitter is set to transmit at a specific RF frequency; typically between 6.4 GHz and 6.5 GHz, and is divided into twelve discrete channels. It is important to understand that these bands require a license and often require coordination with a local frequency coordinator.

Once the signal is prepared for transmission, the RF output of the transmitter is connected to an antenna system. This system can be composed of a single omni-direction antenna, or a more complex hybrid-directional or a downward-facing antenna. Several factors dictate the type of

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