Transmission of Digital Satellite

Transmission of Digital Satellite

Transmission of Digital Satellite

The methods used to multiplex different signals

Different method are usually used in satellite TV signals oval naturally too (with Mel + / -63.4 degrees and orbital period of about 12 hours, also known as Molniya orbit), or orbit 37,000 kilometers (22,300 miles) above Earth's surface in the line of equator.

And satellite television, like other related communication satellite, starts with a transmitting antenna located in the facility transmission. And satellite dishes are sending a very large, estimated at around 9 to 12 meters (30 to 40 feet) in diameter. The result is the increase in diameter greater accuracy and power of the satellite signal. Transmission dish refers to a specific satellite and transmitted signals are transmitted within a specific frequency, so that it is received by a Mazboot receptors on the frequency range of the satellite. The future re-broadcast signals to the land, but the scope of different frequencies (a process known as translation, used to avoid interference with the signal transmission), usually in the C-band (4-8 GHz) or band Ku (12-18 GHz), or both. Called stem signal path from satellite to ground receiving station downlink reference. (Ambardar 1999)

Calculations and experiments show that the transmission method of the double World Cup on subcarriers placed uniformly in the strip videospektra. manages to convey not more than eight mono programs.

The main obstacle is arising because of nonlinear effects comprehensible crosstalk, which in audio broadcasting set particularly stringent standards.

In another embodiment, the analog transmission trunk HIS condenses multiple audio broadcasting signals, each of which is transmitted on a single carrier using FM (the principle of "one channel in one carrier," is widely used in the transmission telephony). And in this case the capacity of the trunk does not exceed eighty-sound program of first class quality, which is not cost effective.

Much better results are achieved when transmitting audio signals in digital form with a temporary separation. Based on this work equipment "Orbit-RV." designed to feed via satellite audio programs to regional broadcasting center. Audio broadcasting signals are converted at the input of the transmitting complex Orbit-RV "into a discrete form, using the nonlinear instantaneous companding, so that in a standard digital stream 2048 kbit / s can transmit six channels of high quality class, or ten channels of the first or second class, 15 channels . Total number of channels for audio broadcasting is allocated two streams of 2048 kbit / s, they are subject to error-correcting coding with a relative speed of 3 / 4, here are added to the image signals of newspaper strips, the total flow at a rate of about 19 Mbit / s for further processing.

Apparatus "Orbit-RV" at work through satellite "Horizon" demanded the receiving antenna with a diameter 12 m, ie could only work in the station "Orbita", which greatly restricted its application. Significantly greater flexibility has introduced in the near future digital audio broadcasting system with multiple access ...