The invention relates to a satellite receiving system as described in the preamble of claim 1.
The invention further relates to a satellite receiver, to a power supply unit for use in a satellite receiving system, and to switching means for use in such a power supply unit.
Such satellite receiving systems are known, for example from the book translated into Dutch "Televisietechniek" from O. Limann and H. Pelka. To receive satellite signals from satellites the satellite receiving system comprises normally a parabolic antenna and a converter to convert the satellite signal to an input signal for a satellite receiver. Such converters are normally called low noise (block) converters (LNC) and convert a frequency band called X-band (and a small part of the so called Ku-band) in the range of from 10 to 13 GHz to frequencies in the so called L-band in the range from 950 to 2150 MHz and further amplifies this signal.
The satellite receiver supplies the converter (located outside the home together with the antenna) from power. Further nowadays it is necessary to switch the reception between horizontal and vertical to receive the signals with both polarisation directions. Further it is necessary to select which part of the X-band has to be converted.
The horizontal/vertical switching is done by switching the power supply between 13 and 17 Volt. The band switching is normally done by whether or not modulating the power supply voltage with a 22 kHz signal.
This complete power supply voltage (comprising real power supply and switching information) is fed, via the tuner in the satellite receiver (Set Top Box) through the same (coax) cable that transmits the so called HF signal from the converter to the satellite receiver, to the converter.
In known solutions of satellite receiving systems which have to be able to switch the converter between different polarisation's, and frequency bands a power coil is used to AC separate the power supply from the output which contains the 22 kHz signal. Further a power 22 kHz generator is coupled to this power coil. The 13/17 volt switching is normally done with the main power supply. These solutions are as a consequence complex and expensive.
Nowadays the need arose to control more equipment along the same (coax) cable like amplifiers and switchers and to switch between more sub-bands than two.
Therefore the European Telecommunication Satellite Organization has made a standard "Digital Satellite Equipment Control" (DiSEqC), Mar. 22, 1996. DiSEqC is backwards compatible with the known 13/17 Volt and 22 kHz switching. In addition it can transmit commands by means of 22 kHz bursts.
Disadvantages of prior art satellite receiving systems are that these are not able to handle the more sophisticated equipment's and that the known systems further are complex and expensive.