Digital wireless system of receiving-transfer of sound and image signals of Grass Valley a Thomson Brand Company

By Fedor Samojlov

Specialists in the field of television broadcasting for the long time were dreaming about technical opportunities of transfer and receiving o signals of images and sound through radio frequency without use of connection cables. In last years that problem was realized by small number of companies-developers of TV and radio techniques and to come to international market of receiving-transmitting equipment with facilities, which with different level of quality and reliability are capable to satisfy the requirements of specialists of television industry.

One of the latter, and in specialists’ opinion, the most successful developing in this field became the system created by specialists of Grass Valley a Thomson Brand Company. It got the name DWCS (Digital Wireless Camera System). Due to the use of most contemporary digital technologies of processing, transfer and receiving of sound and image signals it became possible to create really reliable compact set of equipment, which provides high quality of signal on receiving side.

The use of antennas with circular direction diagram allows ignoring reflections and fading of signal when it is passing from transmitter to receiver. Experimental investigations in field conditions proved the opportunity of reliable work of systems when conducting of filming in most hardly accessible places even with presence of different natural signal screening and reflecting elements and constructions. Usually it is reasonable to use such systems in filming conditions when the opportunity of use of multiple-strand and triax connecting cable is expelled.

New wireless DWCS system is assigned for operating in set with transmitting TV and video cameras of LDK100/200 models. These cameras, as it is well known to specialists, provide high quality of formed signals and exploitation reliability as during operation in stationary studio conditions, as in the set of equipment for mobile television unit and out of studio conditions of filming. System of receiving/transmitting integrates successfully into the structure of camera channel of these cameras and, in particular, without necessity to use some additional adapters can operate with facilities of camera control of Series 9000 model. So, an opportunity of camera functioning in follower condition (gunlock) and its independent work with other cameras, for example, in mobile television unit is foreseen. Besides, due to that DWCS system practically doesn’t implement time delay in transfer and receiving of signal (less than 60 ms), directly during filming plots can be used for including into “live” program, broadcasted in real time scale, without worrying that, for example, there will be delay of sound accompaniment from video image.

DWCS has very small overall dimensions and weight. It is equipped with autonomous power supply unit, doesn’t require additional stuff of serving personnel and allows to conduct filming and signal transfer in closed premises, to process fast filming with very little viewing angles and in most firm exploitation conditions, what is especially comfortable during broadcasting of sports games or concert-mass performances. The quality of transmitted signal is significantly higher, than during filming with camera equipped with triax cable. New system provides quality corresponding to 4:2:2, 10 bit, DVB-T COFDM standard. In video image there is no unpleasant effects, usual for MPEG systems, when the lower level of discretization is used. In DWCS inter-field compression is used what guarantees the same quality of image signal in each half shot.

Wireless system mounted to LDK camera

Ten-unit processing also provides absents of visual edging or contour on objects with same background, for example, such as sky.

System consists of small separate modules. Receiving block connects to receiving antenna with the help of standard triax cable with 8 cm diameter, which can achieve the length of up to 400 m if it is required. As it was said earlier, DWCS can be synchronized from external supporting signal. So, for example, in studio conditions of filming attachment to one synchronizing system is possible for an opportunity to work with camera in the set of studio television-production facility equipment.

Wireless system can get power supply from accumulator battery or from the source of continuous current of 12 V voltage. Consumed power is about 35 Wt (including camera head and camera viewfinder). The weight of the set of camera with viewfinder and system is about 4.8 kg. Minimal distance of receiving/transmitting of image and sound signal achieves 150 m. Standard diapason of system operation is 2.4…2.5 GHz. Camera adapter LDK 5450, radio frequency module LDK 5451, wireless control block LDK 4450 WCU, block of receiving antenna LDK 4452, receiver LDK 4453/00, block of data processing LDK 4454/00, and also all necessary cutoff points and connection cables are included in the set.

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