MXPA06007698A - Outside unit for satellite reception and method of reception with said unit - Google Patents

Abstract

The invention proposes an LNB using two transposition frequencies chosen on either side of the reception band 200 so as to obtain a transposition of supradyne type 205 and a transposition of infradyne type 204 according to the frequency used. This choice of transposition frequencies makes it possible to have an overlap zone 202 in the middle of the reception band which is transposed with the aid of the two oscillation frequencies but at different frequencies. This makes it possible to choose between the two transpositions in the case where the frequency transposed with the aid of an oscillator corresponds to a particularly noisy frequency.

Description

EXTERNAL UNIT FOR RECEIVING SATELLITE SIGNALS AND SIGNAL RECEPTION METHOD WITH SUCH UNIT DESCRIPTION OF THE INVENTION The invention relates to an external unit for receiving satellite signals and to a method of receiving signals with said unit. The invention aims to improve the problems of interference with the coexisting communication systems. External units for reception of satellite signals are commonly referred to as LNB (acronyms for low noise blocks). These units are usually placed in the center of a parabolic reflector which focuses the waves. A unit generally comprises a source which transforms the electromagnetic waves into an electrical signal and then the signals are amplified and transposed to an intermediate frequency band so that it is sent to an internal unit, for example a television program decoder, for example. half of a coaxial cale. For reception of television programs, the useful satellite band is between 10.7 GHz and 12. 75 GHz. The external units are manufactured to receive the entire frequency band according to a horizontal polarization and a vertical polarization. The intermediate band used is between 950 and 2150 MHz. The external units divide the reception of band signal into four secondary bands (sub-bands), each corresponding to half of the satellite band for each of the polarizations. The selection of the band is made, for example, with the help of instructions sent by the internal unit to the external unit via the coaxial cable in accordance with the DiSEqC standard. According to the state of the art, the separation of the satellite band into two secondary bands is carried out by using a transposition signal which can take two frequency values which are conventionally 9.75 GHz and . 6 GHz. With these two transposition frequencies, the part of the satellite band that is between 10.7 and 11. 7 GHz is transposed between 950 and 1950 MHz and the frequency band between 11.7 and 12.75 GHz is transposed between 1100 and 2150 MHz. Interference problems can arise with other transmission devices, in particular with wireless digital telephones. The DECT standard provides for the use of a frequency band that is between 1881 and 1898 MHz in Europe and between 1897 and 1914 MHz in the United States. However, this frequency band is placed in the intermediate satellite band, so it needs adequate protection so that the reception of the programs that are transposed to this part of the intermediate satellite band is not altered. The protection problem is completely greater when the decoder comprises a transmitter / receiver operating in the DECT band so that it is related to a telephone line via a DECT telephone base or when the decoder itself includes a DECT telephone base. This problem has already been identified in the patent application of EUA 2002/0052184 Al, and the solution provided consists of adding a frequency converter in the vicinity of the LNB which performs an additional transposition of the intermediate band signal when this signal needs to correspond at a frequency located in the band part subject to interference. However, such a solution requires an additional means at the LNB level and therefore an additional cost. In addition, - this requires the use of an additional control signal and therefore bandwidth in the linker cable. The invention proposes to solve the problem of interference using a less expensive technique in which it hardly modifies the known structure of an external unit of type LNB. The invention proposes an LNB that uses two transposition frequencies that are selected on both sides of the reception band in such a way that a transposition of the supradynamic type and an infra-dynamic transposition are obtained according to the frequency used. This selection of transposition frequencies makes it possible to have an overlap zone in the middle part of the reception band which is transposed with the help of the two oscillation frequencies, but at different frequencies. This makes it possible to select between two transpositions in the case where the frequency transposed with the help of an oscillator corresponds to a particularly noisy frequency. The invention is an external unit for receiving waves originating from a satellite, the unit comprises an amplification means and a transposition means using two transposition frequencies to perform the transposition of a satellite reception band to an intermediate frequency band of smaller size compared to the size of the reception band. The two transposition frequencies are such that a part of the satellite reception band is transposed to the intermediate frequency band in an infra-dynamic manner by using one of the transposition frequencies and another part of the satellite reception band is transposes the intermediate frequency band in a supradynamic manner by using the other of the transposition frequencies. The two transposition frequencies are selected so that there is a common intersection with the two parts of the satellite reception band which are transposed to the intermediate band with the help of each of the two oscillators with an inverted spectrum in itself . The invention is also a method for receiving a radio signal originating from a satellite in a satellite reception band with the help of an external unit having an amplification means and a transposition means using two transposition frequencies to transpose a satellite reception band to an intermediate frequency band of a size smaller than the size of the reception band. The reception band is separated, for a given polarization, into at least four secondary bands of increasing frequencies and two adjacent secondary bands which are transposed with the aid of two different transposition frequencies. Preferably, one of the transposition frequencies is located at a frequency below the lower frequency of the satellite reception band from which the lower frequency of the intermediate band is subtracted. The other frequency is located at a frequency higher than the highest frequency of the satellite reception band to which the base frequency of the intermediate band is added. The maximum separation between the oscillation frequencies is fixed by the width of the reception band to which is added twice the lowest frequency of the intermediate band and to which 81 MHz are also added. The invention will be better understood and other characteristics and advantages will become evident upon reading and description that follows, the description refers to the attached drawings, in which: Figure 1 represents the structure of an LNB, according to the present invention, Figure 2 presents a first example of transposition according to the invention, figure 3 presents a second example of transposition, according to the invention. Figure 1 represents an external unit 1 (hereinafter referred to as LNB) implementing the invention. The LNB 1 comprises a source 100, for example an up, which receives the waves originating from the reflection in a parabolic dish (not shown). The waves received by the source 100 are transformed by a transition zone 101 into two electrical signals H and V representative of the waves received respectively under the horizontal and vertical polarization. Two low noise amplifiers 102 and 103 respectively amplify each of the electrical signals H and V. A switch 104 selects the output of one of the two low noise amplifiers 102 and 103 so as to supply the signal to the transposition means. The transposition means comprises a first bandpass filter 105 coupled to an amplifier 106 so as to amplify the selected signal in the reception band of the LNB 1., for example the band between 10.7 GHz and 12.75 GHz. The transposition means comprises a mixer 107 which mixes the signal originating from the first filter 105 with a transposition signal. The transposition signal is provided in the example described by two oscillators 108 and 1.09, only one of which is provided so that it has a fixed frequency transposition signal that is selected from two frequencies. An amplifier 110 coupled to a second band pass filter 111 amplifies the signal originating from the mixer and selects a pass band corresponding to an intermediate frequency band, for example between 950 and 2150 MHz, so that provides a signal transposed in the intermediate band to an input / output terminal of the LNB 1 in which a coaxial cable (not shown) is plugged. The LNB 1 also comprises a low pass filter 112 attached to the input / output terminal so as to extract the power supply to the LNB and the control signals that originate from a remote indoor unit (not shown) '. A drive and power supply circuit 113 is connected to the low pass filter 112. The drive and power supply circuit provides a voltage to all the elements of the LNB 1, selectively for the oscillators 108 and 109 so that only one operates. The drive and power supply circuit 113 also provides the switch 104 with a control signal so that it selects the desired polarization by the indoor unit. The control signals sent by the internal unit are, for example, signals encoded according to the DiSEqC standard. The exemplary mode shows two oscillators, only one of which is energized. It is possible to have a single oscillator capable of providing both frequencies as a control function. It is also possible to have two oscillators that operate permanently but whose output is supplied with a selection means which makes it possible to link only one of the oscillators to the mixer. What is important is to have an oscillation means that makes it possible to provide a fixed frequency transposition signal selected from two frequencies. As can be seen by a person skilled in the art, the described example corresponds to a universal LNB and all the structures of a universal LNB are applicable. However, this LNB produced according to the invention is itself distinguished by the transposition frequencies provided by the oscillators 108 and 109. The frequencies of the oscillators are selected on both sides of the reception band so as to obtain a transposition of supradynamic type and transposition of infradinamic type, according to. the frequency used. Such selection leads to having an overlap zone in the middle part of the reception band in which the transposed frequencies are not located at the same frequencies. . This makes it possible to select between the two transpositions in the case where the frequency transposed with the help of an oscillator corresponds to a particularly noisy frequency. One condition, to form a good transposition of the entire reception band, is to have the transposition frequencies separated from the limit frequencies of the reception band by a frequency corresponding to the lower frequency of the transposition band. Figure 2 shows an example of transposition carried out with equal transposition frequencies, respectively, at 9.75 'GHz and 13.7 GHz, which correspond to the minimum separation. The reception band 200 which is between 10.7 GHz and 12.75 GHz is separated in the first to the third secondary bands 201 to 203, the first secondary band 201 is between 10.7 and 11.55 GHz, the second secondary band 202 is between 11.55 and .11.9 GHz and the third secondary band is between 11.9 and 12.75 GHz. The first and second secondary bands 201 and 202 are transposed simultaneously and in an infra-dynamic way to the intermediate band between 950 and 2150 MHz with the help of the frequency oscillator 9.75 GHz, this transposition is represented by the band 204. The second and third secondary bands 202 and 203 are transposed simultaneously and in a supradynamic way to the intermediate band between 950 and 2150 MHz with the help of the frequency oscillator 13.7 GHz, this transposition is represented by band 205. The band is represented in an inverted manner for better compression since the effect of supradinamic transposition is to invert the spectrum. Those skilled in the art will appreciate that the second subband 202 is transposed with the two oscillators to a portion in the intermediate band where it is between 1800 and 2150 MHz. Spectrum inversion does not represent a problem at the demodulation level of signal since the demodulators used for satellite transmissions are designed to make an inversion of the demodulated channel, if necessary. In addition, it is common to have mutually inverted spectrum channels. Yes one considers the frequency bands used for DECT phones: Europe uses a band that is between 1881 and 1898 MHz and the United States uses a band that is between 1897 and 1914 MHZ. The union of these bands corresponds to a DECT band that is between 1881 and 1914 MHz. When an indoor unit includes a communication device that operates in accordance with the DECT standard, this DECT band corresponds to a band that is vnoisy at a level of the internal unit and therefore it is rather unreliable. The DECT band is represented in black on the transposed intermediate bands 204 and 205 and it can be seen that the noisy DECT band for a transposition carried out with an oscillator corresponds to a non-noisy band which is between 2036 and 2069 MHZ for transposition carried out with the help of another oscillator. The division limit of the transposition arises if transposition frequencies are selected so that they are too far apart with respect to the reception band. The maximum limit of separation between the oscillation frequencies is fixed by the width of the reception band, for example 2050 MHz, to which is added twice the lowest frequency of the intermediate band, that is, twice 950 MHz. and in which the difference is also added, obtained with the example of figure 2 and between the upper junction of the intermediate band which is 2150 MHz and the transposed upper band of the non-noisy band corresponding to a noisy band , that is, 2069 MHz, for example 81 MHz. Furthermore, in the lower part of the intermediate band a GSM band coexists between 935 and 960 MHz. This band is superimposed with the intermediate band on the lower part that is between 950 and 960 MHz. The GSM band can be altered when a GSM base station is in proximity to an LNB. Although less problematic than the DECT band, should a DECT apparatus be included in the indoor unit, this GSM band can also be eliminated without any problem by shifting the oscillation sequences. It is possible to provide a safety margin around the DECT and GSM bands so as to ensure that there is no invasion in a channel located at the boundary of the intermediate band. The example of Figure 3 corresponds to a preferred example which diverts the DECT and GSM bands and at the same time retains a safety margin. The transposition frequencies are set, for example, at 9.72 GHz and 13.73 GHz. The reception band 300 is between 10.7 GHz and 12.75 GHz and is divided as in the previous example into three secondary bands, the first one being between 10.7 and 11.58 GHz, the second one is between 11.55 and 11.87 GHz and the third one is between 11.87 and 12.75 GHz. The first and second secondary bands are transposed simultaneously and in an infra-dynamic way to the intermediate band between 980 and 2150 MHz with the help of the frequency oscillator at 9.72 GHz. The second and third secondary bands are transposed simultaneously and in a supradynamic way to the intermediate band between 980 and 2150 MHz with the help of the frequency oscillator 13.73 GHz. The band is represented in an inverted way for better given compression that the effect of supradinamic transposition is to invert the spectrum. A person skilled in the art will appreciate that the portion of the intermediate band in which it is between 1860 and 2150 MHz and which is transposed with the help of the two oscillators is smaller in size but sufficient to deflect the DECT band as shown in FIG. explain previously, the image of the DECT band is located between-2106 MHz and 2129 MHz. The useful spectral width of the intermediate band is also reduced on its lower part in order to separate it from the GSM band and to deflect any related interference problem. with this band. The transposition of frequency differs from the state of the art without, however, requiring any significant change at the level of the internal unit. Specifically, scanning of the satellite band is performed in an alternative manner. With the help of figure 3, the transposition method will now be detailed. The reception band 300 is divided into a first to fourth secondary bands 301 to 304. The first secondary band 301 is between 10.7 and 11.58 GHz, this first secondary band is transposed with the help of the transposition frequency of 9.72 GHz given that there are no other possibilities. The second secondary band 302 is between 11.58 and 11.725 GHz, this second secondary band 302 is transposed with the help of the 13.73 GHz transposition frequency in such a way that it deflects the problems related to the DECT band which can arise if the frequency of 9.72 GHz. The third secondary band 303 is between 11.725 and 11.87 GHz, this third secondary band 303 is transposed with the help of the transposition frequency of 9.72 GHz in such a way that it deflects the problems related to the DECT band which can arise if the frequency of 13.73 GHz is used. The fourth secondary band 304 is between 11.87 and 12.75 GHz, this fourth secondary band 304 is transposed with the help of the transposition frequency of 13.73 GHz, since there are no other possibilities. The size of the second and third secondary bands 302 and 303 may vary since their widths are greater than those of the bands. It is also possible to produce two adjacent secondary bands that are slightly overlapped so as to ensure that the cut-off of the reception band in secondary bands does not occur exactly in the middle of a transmitted channel. The person skilled in the art will understand that the separation into four secondary bands with the transposition frequencies as defined correspond to the minimum separation that can be carried out in order to deflect the DECT band. In the selected example, the transposition frequencies are selected symmetrically with respect to the reception band. It is not necessary to have a symmetry like this. It is more practical to select non-symmetric frequencies, for example in order to select a cheaper component, this is completely possible if the previously established conditions are met.

A person skilled in the art will understand that the invention is applicable with respect to each of the LNB polarizations as well as with respect to the LNB having only a single polarization.

Claims (11)

1. External unit for receiving waves originating from a satellite, the unit comprises an amplification means and a transposition means using two transposition frequencies to transpose a satellite reception band to an intermediate frequency band of a smaller size than the size of the reception band, characterized in that the two transposition frequencies are such that a part of the satellite reception band is transposed to the intermediate frequency band in an infradynamic manner by using one of the transposition frequencies and another part of the satellite reception band is transposed to the intermediate frequency band in a supradynamic manner by using the other of the transposition frequencies and wherein the two transposition frequencies are selected such that there is a common intersection to the two parts of the satellite reception band which are tra They place the intermediate band with the help of each of the two oscillators with an inverted spectrum on itself.

2. External unit, as described in claim 1, characterized in that one of the transposition frequencies is located at a frequency below the lower frequency of the satellite reception band from which the lower frequency of the satellite is subtracted. intermediate band and where the other of the frequencies is located at a frequency above the upper frequency of the satellite reception band to which the base frequency of the intermediate band is added.

3. External unit, as described in claim 2, characterized in that one of the transposition frequencies is equal to 9.75 GHz and the other of the frequencies is equal to 13.7 GHz.

4. External unit, as described in claim 2 , characterized in that the maximum separation between the oscillation frequencies is fixed by the width of the reception band to which the lower frequency of the intermediate band is added twice and to which 81 MHz is also added.

5. External unit , as described in claim 4, characterized in that one of the transposition frequencies is equal to 9.72 GHz and the other of the frequencies is equal to 13.73 GHz.

6. External unit, as described in claim 1, characterized in that the transposition means comprises two oscillators which are alternatively supplied so that there is a fixed frequency transposition signal that is selected from two frequencies. transposition.

7. Method for receiving a radio signal originating from a satellite in a satellite reception band with the help of an external unit having an amplification means and a transposition means using two transposition frequencies to transpose a band of satellite reception. to an intermediate frequency band of a size smaller than the size of the intermediate band, characterized in that the reception band is separated, for a given polarization, in at least four secondary bands of increasing frequencies where a part of the band satellite reception is transposed to the intermediate frequency band in an infradinamic manner by using one of the transposition frequencies and another part of the satellite reception band is transposed to the intermediate frequency band in a supradinamic manner by Using the other of the transposition frequencies, two adjacent secondary bands are transposed with the help of two different transposition frequencies. Method as described in claim 7, characterized in that one of the transposition frequencies is located at a frequency below the lower frequency of the satellite reception band from which the lower frequency of the intermediate band is subtracted and wherein another frequency is located at a frequency higher than the highest frequency of the satellite reception band to which the base frequency of the intermediate band is added. 9. Method as described in claim 8, characterized in that one of the transposition frequencies is equal to 9.75 GHz and the other one of the frequencies is equal to 13.7 GHz. 10. Method as described in claim 8, characterized in that the maximum separation between the oscillation frequencies is fixed by the width of the reception band to which is added twice the lower frequency of the intermediate band and to which 81 MHz are also added. 11. Method as described in claim 10, characterized in that one of the frequencies of transposition is equal to 9.72 GHz and the other of the frequencies is equal to 13.73 GHz.