Founding in 1937 as a response to the impending World War II conflict, Saab was established to help defend Sweden’s freedom and national sovereignty by maintaining its supply of military aircraft. Today, the company remains active in the areas of air, land and naval defence, as well as civil security and commercial aeronautics, delivering products and services globally.
Naval mines are a major maritime threat to both merchant and military boats. These explosive devices can sink or damage a vessel that comes into contact or within detonation range. With 90% of global trade transported by sea* and naval operations increasing, the detection and safe neutralisation of mines is a major priority for naval forces.
Today’s naval mines are incredibly sophisticated, with some models able to distinguish between different types of vessels: influence mines, for example, use narrow-band sensors that can be programmed to detect acoustic properties of specific boats – from propeller design to changes in cavitation sounds.
To counteract the threat of these intelligent mines and ensure the safety of naval personnel and boat passengers, Saab Naval developed a remote control surface drone mine sweeper. Designed to be piloted from the mother ship, these unmanned vessels resemble naval craft, journeying miles ahead of the fleet to detect and clear mines.
The main issue facing Saab during development of the drone was finding a suitable wireless system that would not only control the vessel remotely, but also transmit a video link from the drone, back to the mother ship over distances of up to five miles. Saab asked Wood & Douglas to provide this powerful wireless link.
To maintain a strong signal, Wood & Douglas installed four antennas, one on each corner of the main control boat. Known as ‘diversity’, multiple transmission reduces the chance of signal drop out and interference, improving reliability, especially over long distances. Because this configuration requires digital processing of multiple streams, Wood & Douglas deployed a dVMo (Digital Video for Moving Objects) two-way transmitter and receiver system of radios.
Using COFDM (Coded Orthogonal Frequency Division Multiplexing) modulation, the dVMo delivers a more resilient signal in the presence of interference, while processing delayed multipath signals in challenging environments. This robust performance also allows the signal range to extend beyond that of a typical RF power output and meet SAAB’s requirements for a long distance connection. The dVMO is also designed to provide low delay video.
A power amplifier was needed to increase the effective range of the transmission without widening the signal through intermodulation distortion. Wood & Douglas’ dVMo PA unit was able to produce 1W COFDM output from a standard 100mW dVMo-T drive signal without causing spectral regrowth.
Securing the sensitive nature of the transmission was also a top priority for SAAB and its naval customers. Wood & Douglas uses high ABS encryption to guard against interception offering upgrades from standard 32 up to 128 and 256 bit key systems.
- Critical wireless transmission of data and video from control ship to a surface drone mine sweeping vessel
- dVMO radio set-up performs under heavy interference and problem of multipathing without any hint of delay