SYSTEM FOR RECEIVING A SATELLITE SIGNAL

Abstract

System for receiving a satellite signal acquired by an antenna (A), the satellite signal comprising a first signal of interest (R) and a second signal of interest (L) having different polarizations, the system for receiving a satellite signal comprising: a first channel (2R) comprising a first frequency converter (211) configured to frequency shift the first signal of interest (2R) and to apply a first gain (G1), a second channel (2L) comprising a second frequency converter (212) configured to frequency shift the second signal of interest (2L) and to apply a second gain (G2), a centralized processing unit (1) configured to: estimate a first difference between a power of the first signal of interest (R) measured downstream of the first frequency converter (211) and a first saturation power ( ) constituting a limit of a linear operating domain of the first channel (2R),command an adjustment of the first gain (G1) from the first deviation, so as to reduce the first deviation and maintain the power of the first signal of interest (2R) below the first saturation power (), estimate a second deviation between a power of the second signal of interest (L) measured downstream of the second frequency converter (212) and a second saturation power () constituting a limit of a linear operating domain of the second channel (2L), command an adjustment of the second gain (G2) from the second deviation, so as to reduce the second deviation and maintain the power of the second signal of interest (L) below the second saturation power (). Figure for the abstract: Fig. 4,

Description

Title of the invention: SYSTEM FOR RECEIVING A SATELLITE SIGNAL technical field

[0001] This disclosure relates to the general field of satellite communication and more particularly to processing applied to satellite signals received by a receiver. STATE OF THE ART

[0002] The transmission of signals between satellites orbiting the Earth and ground stations is used in numerous applications, such as television, the internet, and secure communications. Satellite signals emitted by the satellite and received by the antenna are radio frequency communications belonging to a given frequency band. After being received by the antenna, they are generally carried by one or more radio frequency channels. Such a channel typically comprises an amplifier, a fixed-gain frequency converter, and a transmission line. The channel is statically dimensioned to meet certain performance criteria, including limiting noise during satellite signal transmission and remaining within a linear operating range.The sizing is generally carried out for extreme conditions, particularly degraded weather conditions, for various availability objectives. Thus, the operation of the receiving chain is most often suboptimal.

[0003] The satellite signals are then transmitted via the transmission line to various pieces of equipment, notably to extract information carried by the signals and to correct the antenna position. This equipment includes automatic gain controllers to control the power of the received satellite signals before the digital processing is carried out.

[0004] In order to increase data rates and overcome spectral occupancy limitations, recent satellite links use increasingly higher frequencies with wide bandwidths. Furthermore, depending on weather conditions or the type of satellite orbit, the attenuation of transmitted satellite signals can vary.

[0005] Fixed-gain transmission chains do not allow for high-availability data links in the case of very high-speed transmissions. Furthermore, reconfiguring channel gains between each satellite link, or based on weather forecasts, proves insufficient to meet performance criteria with high-dynamic-range satellites, particularly for Satellite links are highly preferred. Finally, the addition of local automatic gain controllers at the channel level induces disturbances in related equipment functions, notably antenna position correction. Description of the invention

[0006] One purpose of this disclosure is to enable the reception of a satellite signal by means satisfying performance criteria (linear behavior and reduced noise sensitivity) regardless of the frequency band and bandwidth of the received signal.

[0007] This goal is achieved by a system for receiving a satellite signal acquired by an antenna, the satellite signal comprising a first signal of interest and a second signal of interest having different polarizations, the system for receiving a satellite signal comprising: • a first channel comprising a first frequency converter configured to frequency-shift the first signal of interest and to apply a first gain, • a second channel comprising a second frequency converter configured to frequency-shift the second signal of interest and to apply a second gain, • a centralized processing unit configured for: • estimate an initial difference between the power of the first signal of interest measured downstream of the first frequency converter and a first saturation power constituting a limit of a linear operating domain of the first channel, • to order an adjustment of the first gain from the first deviation, so as to reduce the first deviation and keep the power of the first signal of interest below the first saturation power. • estimate a second difference between a power of the second signal of interest measured downstream of the second frequency converter and a second saturation power constituting a limit of a linear operating domain of the second channel, • command an adjustment of the second gain from the second gap, so as to reduce the second gap and keep the power of the second signal of interest below the second saturation power.

[0008] Dynamically modifying the gains used by the first frequency converter and the second frequency converter allows the The operation of the corresponding channels is optimized to ensure that the received signal power of interest is as close as possible to the saturation power, thus improving reception quality. Saturation within the channels is avoided. Furthermore, signals that are severely attenuated, for example by adverse weather conditions, can be amplified. Using a centralized processing unit to control gain adjustments achieves the aforementioned advantages without requiring extensive channel modifications. In particular, this solution is less expensive than integrating a dedicated automatic gain controller into each channel.

[0009] Since the gain is modified upstream of the centralized processing unit, and therefore closer to the antenna receiving the satellite signal, the noises related to the transmission of the satellite signal to the centralized processing unit are not likely to be amplified.

[0010] Furthermore, the gains of the different channels can be modified in a coordinated manner. This prevents disruption to the related functions of the satellite signal receiving system equipment. The continuous and precise adjustment of the channel gain values ​​also prevents disruption to channel operation and avoids interruptions in the transmission of the satellite signal.

[0011] The system for receiving a satellite signal may have the following advantageous and non-limiting characteristics, taken alone or in any technically possible combination:

[0012] - the first gain and the second gain are adjusted to identical values;

[0013] - the centralized processing unit is configured to: • calculate the first saturation power using a first model estimating how the saturation power in the first channel varies as a function of the frequency of a signal processed by the first channel, and • calculate the second saturation power using a second model estimating how a saturation power varies in the second channel as a function of a frequency of a signal processed by the second channel;

[0014] - the centralized processing unit is configured to: • apply a spectral analysis to the first signal of interest, in order to determine the power of the first signal of interest measured, and / or • apply a spectral analysis to the second signal of interest, so as to determine the power of the second signal of interest measured;

[0015] - the first difference is also estimated from a first transmission gain applied to the first signal of interest by a portion of the first channel connecting the first frequency converter to the centralized processing unit, and the second deviation is also estimated from a second transmission gain applied to the second signal of interest by a portion of the second channel connecting the second frequency converter to the centralized processing unit;

[0016] - the adjustment of the first gain is also controlled from a data point power recoil depending on a satellite signal modulation scheme, and / or the adjustment of the second gain is also controlled from the power recoil data;

[0017] - the satellite signal has frequencies within the Ka band and / or has a band bandwidth greater than 1.4 GHz;

[0018] - the system for receiving a satellite signal further comprises • a third channel specifically designed to process a deviation signal produced from the satellite signal, the third channel comprising • a third frequency converter configured to frequency-shift the deviation signal and to apply a third gain, • an estimator arranged downstream of the third frequency converter, and configured to estimate an angle between a principal direction adopted by the antenna and a propagation direction of the satellite signal from a satellite to the antenna, taking into account the adjustment of the first gain and the second gain, • in which the centralized processing unit is further configured to control an adjustment of the third gain.

[0019] According to another aspect, a satellite signal receiving station is proposed comprising: • an antenna configured to receive a satellite signal, • a system for receiving a satellite signal as described above, suitable for receiving the satellite signal, in which the centralized processing unit is configured to calculate a satellite signal power from the first adjusted gain and / or the second adjusted gain, • an antenna control unit configured to orient the antenna based on ephemeris data and satellite signal strength.

[0020] According to a final aspect, a method for receiving a satellite signal acquired by an antenna is proposed, the satellite signal comprising a first signal of interest and a second signal of interest having different polarizations, the reception method comprising the following steps: • processing of the first signal of interest via a first channel comprising a first frequency converter which frequency-shifts the first signal of interest, the first frequency converter applying a first gain, • processing of the second signal of interest via a second channel comprising a second frequency converter which frequency-shifts the second signal of interest, the second frequency converter applying a second gain, • estimation of an initial difference between the power of the first signal of interest measured downstream of the first frequency converter and a first saturation power constituting a limit of a linear operating domain of the first channel, • control for adjusting the first gain from the first deviation, so as to reduce the first deviation and keep the power of the first signal of interest below the first saturation power. • estimation of a second difference between a power of the second signal of interest measured downstream of the second frequency converter and a second saturation power constituting a limit of a linear operating domain of the second channel, • control for adjusting the second gain from the second gap, so as to reduce the second gap and keep the power of the second signal of interest below the second saturation power. DESCRIPTION OF THE FIGURES

[0021] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0022] Fig. 1 schematically illustrates a prior art satellite signal receiving station, comprising a processing channel for receiving a polarization.

[0023] Fig. 2 schematically illustrates a satellite signal receiving station, comprising a processing channel for receiving two polarizations and a processing channel for controlling the position of the antenna.

[0024] Fig. 3 schematically illustrates the interactions between the channels and the centralized receiver of the receiving station of Fig. 2.

[0025] Figure 4 schematically illustrates a satellite signal receiving station according to a first embodiment of the invention.

[0026] Fig. 5 schematically illustrates the interactions between the channels and the centralized receiver of the receiving station of Fig. 4.

[0027] The [Fig.6] is a flowchart representing a satellite signal reception method in one embodiment.

[0028] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0029] Ground stations are sized according to the performance of the desired link and the power of the transmitting antenna.

[0030] Generally, a satellite receiving ground station is a receiver comprising an antenna A connected to a centralized processing unit 1 in a control room via one or more processing channels 2 also called radio frequency receiving chains.

[0031] Figure 1 illustrates a satellite signal receiving station comprising a circularly polarized antenna A. Such antennas are widely used in applications where the signal orientation varies or is unpredictable. In a manner known per se, antenna A configured to receive a circularly polarized satellite signal comprises a right-hand circularly polarized (RHCP) antenna source and a left-hand circularly polarized (LHCP) antenna source. In this context, the satellite signal comprises a first signal of interest and a second signal of interest having different polarizations. In other words, the signals received by antenna A are initially separated into two information-carrying signals, also called R,L signals of interest, transmitted on the two corresponding circular polarizations.The system for receiving a satellite signal 1 includes a first channel 2R suitable for processing the first signal of interest R, and a second channel 2L suitable for processing the second signal of interest L.

[0032] Preferably, the antenna A is also suitable for transmitting a deviation signal A produced by an antenna source from the satellite signal. Typically, the deviation signal A is a single output from the antenna source such as the signals of interest R,L.

[0033] In general, the offset signal A is used to measure and correct positional deviations of antenna A relative to the satellite's trajectory. It is used to correct the orientation of antenna A, for example, to correct the angle between a principal direction adopted by antenna A and a propagation direction of the satellite signal from the satellite to antenna A. This allows for maximizing the power of the received signal, as antenna A can be highly directional.

[0034] Each channel 2 includes a frequency converter 21 configured to frequency-shift the processed R,L signal of interest and to apply a gain. Typically, the frequency converter 21 is a carrier frequency down-converter configured to transpose the received RF radio frequency signals of interest from the satellite to lower intermediate frequencies IF, preferably without changing other characteristics. Indeed, if the use of high frequencies is Necessary for transmitting the signal from the satellite to antenna A, the use of lower frequencies facilitates the processing of the signals of interest and their demodulation by receiver 100. More specifically, the first channel 2R includes a first frequency converter 211 configured to frequency-shift the first signal of interest R and to apply a first gain G1, and the second channel 2L includes a second frequency converter 212 configured to frequency-shift the second signal of interest L and to apply a second gain G2. Applying the gains G1 and G2 allows for modification of the amplitude of the signal of interest R and L, in addition to applying the frequency shift. The applied frequency shift can be identical for the first frequency converter 211 and the second frequency converter 212. The frequency shift can be constant and does not depend on the values ​​of the first gain G1 and the second gain G2.

[0035] Preferably, the system for receiving a satellite signal also includes a third channel for processing the deviation signal A and including a third frequency converter 213 configured to frequency shift the deviation signal and to apply a third gain G3.

[0036] In a manner known per se, the frequency converter 21 may include a mixer combining, for example by summing and subtracting, the processed R,L signal of interest with a reference signal from a local oscillator. The frequency converter 21 may include a low-pass or band-pass filter to select the frequency of the signal corresponding to the difference and to suppress the other frequencies. The resulting signal may then be amplified by applying gain to compensate for conversion losses and / or adjust the signal level. The frequency converter 21 is preferably glitch-free.

[0037] Preferably, channel 2 includes an amplifier 22 upstream of the frequency converter 21. The amplifier 22 is preferably a low-noise amplifier (LNA), located at the output of the signal receiving antenna A. The amplifier 22 is configured to amplify the signal directly after reception to prevent noise related to transmission along the channel to the receiver 100, typically located in the control room, from becoming excessive. This increases the signal-to-noise ratio (SNR). In the embodiments illustrated in Figures 2 and 4, the first channel 2R includes a first amplifier 221, and the second channel 2L includes a second amplifier 222.

[0038] The assembly formed by the amplifier 22 and the frequency converter 21 is generally called a radio frequency head. Generally, the gains of the amplifier 22 and the frequency converter 21, and therefore the gain of the head Radio frequency inputs are configured for maximum receiveable signal flow. The gains are static, meaning they are not modified during signal reception. To maximize the signal-to-noise ratio (SNR), the maximum compatible gain within a linear operating range is generally selected. Optimization of the static gains can be performed for each satellite pass, taking into account the satellite's characteristics and trajectory, the ground station's characteristics, and weather conditions. More generally, channel 2 is sized to match the output power of the radio frequency input head 21, 22 to the input characteristics of a centralized processing unit 1 of the receiver 100. As will be detailed later, it is proposed here to dynamically modify the gains G1, G2 applied based on commands issued by the centralized processing unit 1.

[0039] After processing by the frequency converter 21, the satellite signal is then transmitted to the centralized processing unit 1 via the associated channel 2. Each channel 2 is dedicated to processing the signal of interest R,L transmitted by the antenna A.

[0040] Channel 2 includes a radio frequency cable 20 or transmission line 20 connecting the radio frequency head 21, 22 to the centralized processing unit 1. Generally, the receiver 100 of the receiving station includes equipment located away from the antenna A. Thus, the transmission line 20 can extend over a considerable distance, typically several hundred meters. Noise addition and attenuation (or amplification) of the processed signal of interest R,L can occur in the transmission line 20.

[0041] Various components of the receiving station are illustrated in Figures 2 and 4. Typically, the receiver 100 includes the centralized processing unit 1. The centralized processing unit 1 is configured to process the signals of interest R,L. For example, the centralized processing unit 1 is configured to synchronize with an input signal that has been used to modulate a carrier signal, in amplitude, frequency, or phase, in order to decode the information transmitted by the satellite. Preferably, the centralized processing unit 1 is configured to calculate a satellite signal power (Pagc) from the first adjusted gain (G1) and / or the second adjusted gain (G2). The satellite signal power (Pagc) is an evaluation of the received signal level transmitted by the satellite and received by the antenna A.

[0042] Preferably, the receiver 100 includes an estimator 3 or tracking receiver (also called a "digital tracking receiver") suitable for processing the tracking signal A. More specifically, the estimator 3 is arranged downstream of the third frequency converter 213 and configured to estimate an angle between the principal direction adopted by the antenna A and the direction of propagation of the satellite signal from a satellite to the antenna A, taking into account the adjustment of the first gain G1 and the second gain G2, that is, as a function of the variation temporal of their respective values. The angle corresponds to an angular position deviation of antenna A or a pointing error that we seek to correct. It is obtained through complex algorithmic processing implemented by estimator 3.

[0043] In the illustrated embodiment, the ground station includes the first channel 2R configured to transmit the right-biased carrier signal R to the centralized processing unit 1 and to the estimator 3, the second channel 2L, configured to transmit the left-biased carrier signal L to the centralized processing unit 1, and the third channel 2, configured to transmit the deviation signal A to the estimator 3. The estimator 3 advantageously takes into account the first signal of interest R in the estimation of the angle.

[0044] Preferably, the receiver 100 includes an antenna control unit 4 (ACU), configured to orient the antenna A based on ephemeris data and the power of the satellite signal Pagc-

[0045] In a manner known per se, the pointing of antenna A is performed using ephemeris data. The ephemeris data is provided by the satellite operator. The ephemeris data reflects the satellite's orbit and allows the antenna control unit 4 to calculate the satellite's position relative to antenna A, as explained previously. Initially, the antenna control unit 4 is configured to use the ephemeris data to pre-position antenna A in the direction of the satellite.

[0046] The antenna control unit 4 can be connected to the estimator 3 or offset receiver and to the centralized processing unit 1. The antenna control unit 4 is configured to perform antenna pointing, that is, to control the position of antenna A so that antenna A tracks the position of the satellite. More specifically, the antenna control unit 4 is configured to improve the positioning of antenna A after pre-positioning using the received satellite signal, that is, from the satellite signal power (PAGC) calculated by the centralized processing unit 1. Alternatively or complementarily, the antenna control unit 4 is configured to improve the positioning using the angle estimated and transmitted by the estimator 3.

[0047]

[0048] Figure 2 schematically illustrates various elements of the centralized processing unit 1 commonly used. The centralized processing unit 1 includes, for example, a demodulator 6 and an automatic gain control (AGC) 5. The centralized processing unit 1 may also include a power measurement unit 7 configured to calculate, i.e., estimate, the power of the satellite signal Pagc-

[0049] Generally, the automatic gain controller 5 may include a closed-loop feedback control circuit in one or more amplifiers in series. The gain of the amplifier in the internal automatic gain controller is configured to vary dynamically in order to maintain a suitable output signal amplitude despite variations in the amplitude of the input signal, i.e., here, the first and second signals of interest, after processing by their respective processing channels. In other words, the average or peak output signal level depends on the gain value of the amplifier in the automatic gain controller 5.

[0050] Typically, the automatic gain controller 5 is configured to regulate the carrier signal to a constant level. Here, the first automatic gain controller 5 takes as input the first signal of interest R, corresponding to the right-biased carrier signal processed by the first channel 2, and the second signal of interest L, corresponding to the left-biased carrier signal L processed by the second channel 2L. The automatic gain controller 5 provides as output a first regulated signal of interest Rr and a second regulated signal of interest Lr.

[0051] The demodulator 6 can be a second automatic gain controller. The demodulator 6 is configured to perform demodulation of the signal regulated by the automatic gain controller 5. The demodulator 6 advantageously allows for fine-tuning the regulation for the signal of interest.

[0052] The automatic gain controller 5 and the demodulator 6 are configured to calculate a respective gain G5, G6 of the transmitted signals of interest, from the gains applied respectively.

[0053] The power measurement unit 7 is configured to estimate the signal power at the input of the centralized processing unit 1, or more generally the power of the satellite signal Pagc, from the gain values ​​G5, G6. As illustrated in [Fig. 2], the gains G5, G6 are transmitted to the power measurement unit 7. The variations in the signal level estimated by the power measurement unit 7 are representative of the variations in the level of the satellite signal received by the antenna A.

[0054] The processed satellite signal may have frequencies within other frequency ranges, for example in the X band (approximately 10 GHz) or in the S band (between 2 GHz and 4 GHz). The present invention is particularly advantageous when the processed satellite signal has frequencies within the Ka band, that is, within a frequency range between 26.5 GHz and 40 GHz, and especially for communications over a wide bandwidth, for example, 1.5 GHz. The processed satellite signal generally has a bandwidth of less than 1.5 GHz. Indeed, the use of channels 2 with radio frequency heads or static gain G1,G2 frequency converters 21 shows limitations when the dynamic range of the The level of received satellite signal increases. Typically, the frequency range defined by the International Telecommunication Union (ITU) for Earth observation is between 25.5 GHz and 27 GHz. Preferably, the satellite signal processed by the processing unit has frequencies within the Ka band.

[0055] Preferably, the signal received by antenna A, emitted by the satellite, comprises spectrally efficient waveforms occupying the entire available bandwidth, typically a total bandwidth greater than 1.4 GHz, for example, 1.5 GHz. Such a signal requires a high signal-to-noise ratio (SNR) and has a high peak-to-average power ratio (PAPR). Consequently, the satellite signal is very sensitive to the linearity of channel 2 behavior.

[0056] Depending on the availability rate of the data link and the geographical location of antenna A, the input signal dynamics for the required frequency converter 21 may vary. For example, satellites used for observation purposes are often in low Earth orbit (LEO) and are therefore not geostationary. The variation in their position introduces, in addition to variations in losses due to absorption by atmospheric humidity, which are very significant in the Ka frequency band, variable propagation losses related to the distance traveled by the waves.

[0057] The availability rate corresponds to the percentage of time during which communication between the satellite and antenna A is possible when they are within line of sight. Availability rate requirements affect the dynamics of the signals to be received, which can be impacted by the geographical location of antenna A (particularly weather conditions) and the frequency range used. This impact is described in charts established by FUIT.

[0058] More specifically, the level difference between the maximum permissible satellite signal power for remaining within the linear operating range of channel 2, and the minimum power below which thermal noise introduced by the frequency converter 21 prevents an error-free satellite link, decreases with increasing bandwidth. The required dynamic range of this difference increases with environmental humidity. Furthermore, the tolerable input dynamic range of the frequency converter 21 also depends on the waveform used in the modulation of the satellite signal, i.e., the modulation scheme chosen, for example, from among the various modulation schemes of the DVB-S2 transmission standard, and the gain settings of channels 2 (G1, G2).

[0059] Thus, the frequency converters 211, 212 used with a fixed gain G1, G2 and implemented in the ground station illustrated in Figures 1 and 2 do not allow to consider satellite links with a high availability rate in the case of very high-speed transmissions in Ka band.

[0060] The centralized processing unit 1 is configured to: • estimate a first difference between a power P g of the first signal of interest R measured downstream of the first frequency converter 211 and a first saturation power P^tx constituting a limit of a linear operating domain of the first channel 2R, • command an adjustment of the first gain G1 from the first deviation, so as to reduce the first deviation and maintain the power Pg of the first signal of interest R below the first saturation power Psati, • estimate a second difference between a power Pg of the second signal of interest L measured downstream of the second frequency converter 212 and a second saturation power P^ constituting a limit of a linear operating domain of the second channel 2L, • command an adjustment of the second gain G2 from the second gap, so as to reduce the second gap and keep the power Pg of the second signal of interest L lower than the second saturation power Pv,t2-

[0061] With reference to [Fig.4], the centralized processing unit 1 includes an external automatic gain controller 11 configured to drive the frequency converters 211,212. The centralized processing unit 1 includes the elements described above, and in particular the internal automatic gain controller 5.

[0062] The external automatic gain controller 11 is connected to the first frequency converter 211 and the second frequency converter 212. For example, the external automatic gain controller 11 is connected to each frequency converter 21 via a serial bus communication bus, or a low-speed Ethernet link.

[0063] Preferably, the external automatic gain controller 11 is connected to the frequency converter 21 of each channel linking the antenna A to the centralized processing unit 1. In the illustrated embodiment, the external automatic gain controller 11 is thus also connected to the third frequency converter 213.

[0064] The external automatic gain controller 11 is configured to centrally control the respective gains G1, G2 of the frequency converters 211, 212. Centralizing the control process allows for consideration of the relative values ​​of the gains G1, G2 and the characteristics of the different channels 2R, 2L, in particular to maintain the differential levels between the first channel 2R and the second channel 2L.

[0065] Preferably, the first gain G1 and the second gain G2 are adjusted to identical values. The centralized processing unit 1 allows for an adjustment coordinate of the gain values. This reduces the risk of preventing the operation of the algorithms implemented by estimator 3 and of leading to erroneous values ​​of the estimated angle used to orient antenna A.

[0066] Preferably, the external automatic gain controller 11 is further connected on one side to the third frequency converter 213 of the third channel 2A, and on the other side to the estimator 3. The first connection allows the third gain G3 to be dynamically adjusted according to the first and / or second power deviation. The second connection is not a control, but allows the adjustment information, i.e., the adjusted values ​​of the first gain G1 and / or the second gain G2 of the frequency converters 211, 212, to be shared so that the algorithms implemented by the estimator 3 can function correctly.

[0067] With reference to Figure 5, the centralized processing unit 1 may include a deviation measurement unit 8. The deviation measurement unit 8 is configured to perform the estimation of the first and second deviations. Typically, the first deviation is estimated from the gain G5 of the automatic internal gain controller 5 and the first regulated signal of interest Rr, and the second deviation is estimated from the gain G5 and the second regulated signal of interest Lr. The first and second deviations will more generally be referred to as the "esat level deviation." The esat level deviation corresponds to a deviation, i.e., a difference, from the saturation power, beyond which channel 2 no longer operates linearly.As explained previously, in order to improve satellite signal reception, it is necessary to keep channels 2R and 2L within their respective linear operating ranges, and therefore not to amplify the signals of interest beyond the saturation power. The respective gains G1 and G2 are adjusted to ensure that the signal power at the output of the associated frequency converters 211 and 212 does not saturate the transmission line 20.

[0068] Preferably, the centralized processing unit 1 is configured to: • calculate the first saturation power Psan using a first model PgatAf) estimating how a saturation power P^ varies in the first channel 2R as a function of the frequency of a signal processed by the first channel 2R; and / or • calculate the second saturation power P^ using a second model p estimating how a saturation power varies in the second channel 2L as a function of a frequency of a signal processed by the second channel 2L.

[0069] The calculation can be implemented by a deviation measurement unit 8. Preferably, the centralized processing unit 1 stores data in memory of Characterization of channels 2, i.e. information enabling the characterization of the linear operating domain of channels 2. The RF characterization data can be derived from a characterization, by measurement, for each of the channels 2R, 2L, 2A of the ground station connected to the centralized processing unit 1. Preferably, the RF characterization data are adapted according to the ground station and the equipment used upstream of the centralized processing unit 1, typically the type of cable 20 and the characteristics of the frequency converters 21, in particular the respective gains G1, G2, G3.

[0070] More generally, from the channel characterization data 2, the deviation measurement unit 8 can calculate a model used to evaluate the level difference including in particular the saturation power Psat not to be exceeded at the output of the frequency converter 21 so as not to saturate the frequency converter 21 or the transmission line 20 between the frequency converter 21 and the centralized processing unit 1.

[0071] Preferably, the calculation of the level deviation e™t from saturation takes into account a power measurement at the input of the centralized processing unit 1. The power measurement can be obtained in a conventional way, for example by using the gain of the automatic gain controller 5 and spectral analysis techniques, in order to obtain a characterization of the power at the input of the centralized processing unit as a function of the frequency of the signals on the transmission line 20.

[0072] More generally, the centralized processing unit 1 can be configured to: • apply a spectral analysis to the first signal of interest R, so as to determine the measured power Pr of the first signal of interest R; and / or • apply a spectral analysis to the second signal of interest L, so as to determine the power Pr of the second signal of interest L measured.

[0073] The powers Pr-Pr of the first and second signals of interest R,L measured depend on the frequency. Spectral analysis can be implemented before regulation by the automatic internal gain controller 5, or after regulation. In this case, the power measurement is obtained by spectral analysis of the regulated signals of interest Rr,Lr, and takes into account the gain G5 applied by the automatic internal gain controller 5. In other words, the deviation measurement unit 8 is configured to determine the level deviation esat from a local power measurement Pmes(f) transmitted by the centralized processing unit 1 based on a spectral analysis of the regulated signals of interest Rr, Lr allowing the frequency dispersion to be characterized.

[0074] Preferably, the first deviation is also estimated from a first transmission gain Gtl applied to the first signal of interest R by a portion of the first channel 2R connecting the first frequency converter 211 to the centralized processing unit 1, and / or the second deviation is also estimated from a second The transmission gain Gt2 applied to the second signal of interest L by a portion of the second channel 2L connecting the second frequency converter 212 to the centralized processing unit 1. The first and second transmission gains Gt1,Gt2 typically depend on the frequency of the signal transmitted by the transmission line 20, and / or the characteristics of the channel 2R,2L. They are known, typically evaluated beforehand, or provided by the manufacturer. They may take losses into account.

[0075] More specifically, the deviation measurement unit 8 can take into account known characteristics of the radio frequency cables or transmission lines 20 through which the signals of interest R, L are transmitted between their frequency converter 211,212, for example possible filtering elements, in order to calculate the level difference e™t at the output of the respective frequency converter 211,212.

[0076] The centralized processing unit 1, for example via the deviation measurement unit 8, can implement the following calculation to obtain the level deviation esat in decibels from the saturation point:

[0077] p f..........df

[0078] With B the frequency range corresponding to the bandwidth of the satellite signal. The first and second deviations can be equal to the level deviation ewt-

[0079] More generally, we can define the first gap . f pdf) > z- and the second gap esal2 =

[0080] The adjustment of the first gain G1 and the second gain G2 can be carried out so as to reduce the respective gap. Typically, the centralized processing unit 1 implements, typically via the external automatic gain controller 11, a conventional regulation to vary the gains G1,G2 so that the respective gaps tend towards zero.

[0081] Preferably, the centralized processing unit 1 is further configured to control an adjustment of the third gain G3. The adjustment of the third gain can be made based on the adjustments of the first gain G1 and / or the second gain G2.

[0082] Preferably, the adjustment of the first gain G1 is also controlled from a power recoil data Rjb depending on a modulation scheme of the satellite signal, and / or the adjustment of the second gain G2 is also controlled from the power recoil data R(ib- Typically, the power recoil data Rjb is common to the first channel 2R and the second channel 2L.

[0083] As illustrated, the centralized processing unit 1 includes, for example, a recoil evaluation unit 9 relative to the saturation point. The recoil evaluation unit 9 is configured to evaluate the best power recoil value R^b relative to the saturation power Psat of the respective 2R,2L channel, for the frequency of the signal transmitted by the 2R,2L channel.

[0084] The power recoil evaluation can take into account the characteristics of the modulation, for example the type of waveform, or the peak power to average power ratio (PAPR) of the satellite signal. The centralized processing unit 1, typically via the recoil evaluation unit 9, is configured to evaluate the power recoil Rjb according to different embodiments.

[0085] In one embodiment, the power backslash taken into account in adjusting the gains Gl, G2 can be a static quantity. In this case, the power backslash R^b is determined in advance and stored by the centralized processing unit 1 in dedicated memory. The power backslash is chosen so as to guarantee that performance criteria (noise, linear behavior) are met, regardless of the use of the ground station and / or the centralized processing unit 1. For example, the stored power backslash data can be calculated based on a worst-case use case for the ground station, or a worst-case associated with the configuration of the centralized processing unit 1, for example. Thus, in the absence of available data, typically information on the type of modulation used, the backslash data is fixed so that the centralized processing unit 1 can operate regardless of the modulation scheme used.Depending on the modulation scheme, the operating point of channel 2 may be suboptimal.

[0086] Preferably, the centralized processing unit 1 is configured to evaluate the power backlash dynamically. This allows an optimal operating point to be reached for each of the processing channels 2. In this case, information concerning the modulation scheme can be transmitted with the satellite signal and decoded by the centralized processing unit 1. Thus, if data is available, the centralized processing unit 1 is configured to provide an optimal backlash value Rjb. The backlash data R^ can be obtained in the case of a static configuration of the centralized processing unit 1.

[0087] Preferably, the centralized processing unit includes an adaptive coding and modulation (ACM) system. During adaptive operation, the link margin, i.e., the availability margin, can be converted into increased throughput when conditions are favorable. This allows the throughput to be maximized under all the aforementioned conditions.

[0088] More specifically, the power recoil data R^b can be evaluated in different ways depending on the available data. For example, the recoil evaluation unit 9 can be configured to infer the power recoil data R^b from the configuration of the centralized processing unit 1. Typically, the unit centralized processing unit 1 transmits information about its configuration, i.e. the type of modulation used, during its initialization, to the recoil evaluation unit 9. The recoil evaluation unit 9 can calculate the optimal recoil data Rjb from the peak power which depends on the modulation scheme used.

[0089] Typically, the optimal power recoil can be defined as a function of the saturation point. For example, the centralized processing unit 1 can be configured to calculate the power recoil from a lookup table between modulation schemes and power functions of the satellite signal, the lookup table being stored in the memory of the centralized processing unit.

[0090] In the case of QPSK or 8PSK modulation of the DVB-S2 standard, the RdB recoil value can be minimal, typically increased by a margin of between 0 dB and 1 dB relative to the saturation point. In the case of M-APSK modulation, with M = 16, M = 32, or M = 64, the RdB recoil value is typically increased by a margin of between 1 dB and 3 dB relative to the saturation point. For example, for 16APSK modulation, the RdB recoil value can be increased by 1.05 dB relative to the saturation point. For 32APSK modulation, the RdB recoil value can be increased by 2.05 dB relative to the saturation point. For a 64APSK type modulation, the R^b recoil data can be increased by 2.84 dB relative to the saturation point.

[0091] Additionally, the RdB power recoil data can be deduced from the modulation decoded by the centralized processing unit 1 during transmission. During the mission, i.e., when information is exchanged via the satellite link, information about the configuration used by the centralized processing unit 1 can be transmitted to the recoil evaluation unit 9 to modify the RdB power recoil data. Typically, in the case of a dynamic configuration of the centralized processing unit 1 (ACM operation), DVB-S2 transmissions can modify the modulation scheme used during transmission. The recoil evaluation unit 9 is preferably configured to modify the RdB power recoil data according to changes in the modulation scheme.

[0092] In the illustrated embodiment, the centralized processing unit 1 includes a gap calculation unit 10 configured to correct the level deviation esat from the saturation point transmitted by the deviation unit 8 with the optimal recoil data transmitted by the recoil evaluation unit 9. More generally, the centralized processing unit 1 is configured to obtain the edB deviation from the results of the recoil and level deviation calculation processes. Typically, the edB deviation supplied to the external automatic gain controller 11 is obtained by the The following formula: = PdB + esat - In an embodiment without taking into account the recoil data, we would have edn ~ esat.

[0093] The edB difference is used by the external automatic gain controller 11, which drives the gain of the frequency converters 21. Preferably, the rate of change of the first gain G1 and / or the rate of change of the second gain G2 is bounded. This prevents abrupt changes in the gains of the frequency converters 211, 212, which could lead to breaks or interruptions in the satellite link between the antenna A and the centralized processing unit 1.

[0094] Preferably, the gain adjustment G1,G2 from the external automatic gain controller 11 is monitored by the power measurement unit 7. In other words, the external automatic gain controller 11 is configured to transmit the adjusted gains G1,G2 to the power measurement unit 7. This makes it possible to reconstruct the signal level variations at the antenna 4, and to calculate an appropriate value for the power of the satellite signal Pagc transmitted to the antenna control unit 4.

[0095] A receiving process implemented by the system described above comprises the following steps.

[0096] During a step SI 1, the first signal of interest R is processed via a first channel 2R comprising the first frequency converter 211. The processing allows the first signal of interest R to be frequency shifted, in order to apply the first gain G1 of the first frequency converter 211.

[0097] During a step S21, the second signal of interest is processed via the second channel 2L comprising the second frequency converter 212. The processing S21 allows the second signal of interest 2L to be frequency shifted to apply the second gain G2 of the second frequency converter.

[0098] The processing steps SI 1 and S21 can be implemented simultaneously or not. As explained previously, the satellite signal received by antenna A is generally separated into the first and second signals of interest upon reception, and then transmitted on the respective 2R,2L channels to implement the processing steps SI 1 and S21. The steps SI 1 and S21 are performed continuously, that is, during the reception of the satellite signal by antenna A.

[0099] During an estimation step S12, the centralized processing unit 1 estimates the first difference between the power Pr of the first signal of interest R measured downstream of the first frequency converter 211 and the first saturation power PSat\ constituting a boundary of the linear operating domain of the first channel 2R. The estimation step S12 can take place frequently, for example at a frequency of 1 Hz, preferably at a frequency greater than 10 Hz. This allows the value of the first difference to be updated frequently and thus provides a better adjustment of the first gain Gl. The estimation of the first deviation is done from the first signal of interest processed during step SI 1.

[0100] Similarly, during an estimation step S22, the centralized processing unit 1 estimates the second difference between the power P^ of the second signal of interest L measured downstream of the second frequency converter 212 and the second saturation power Psati constituting a boundary of the linear operating domain of the second channel 2L. Likewise, step S22 may frequently, typically at regular intervals and after processing of the second signal of interest in step S21. Steps S12 and S22 may or may not occur simultaneously.

[0101] The receiving method also includes a step S13 for adjusting the first gain Gl from the first deviation, so as to reduce the first deviation and keep the power P% of the first signal of interest 2R below the first saturation power Px. Similarly, the adjustment control step S13 can be implemented frequently and requires the estimation of the first deviation from step S12.

[0102] Similarly, the receiving method includes a step S23 for adjusting the second gain G2 from the second deviation, so as to reduce the second deviation and keep the power P^ of the second signal of interest L below the second saturation power Psati. The adjustment control step S23 can be implemented frequently and requires the estimation of the second deviation from step S22. Thus, steps S23 and S13 can be implemented simultaneously or not. In particular, the steps do not necessarily follow the order shown in [Fig. 6], the deviation estimation steps S12 and S22 being independent and the adjustment control steps S13 and S23 being independent, and can thus be carried out simultaneously or sequentially.

Claims

1. Demands System for receiving a satellite signal acquired by an antenna (A), the satellite signal comprising a first signal of interest (R) and a second signal of interest (L) having different polarizations, the system comprising: • a first channel (2R) comprising a first frequency converter (211) configured to frequency shift the first signal of interest (2R), the first frequency converter (211) and to apply a first gain (Gl), • a second channel (2L) comprising a second frequency converter (212) configured to frequency-shift the second signal of interest (2L), the second frequency converter (212) and to apply a second gain (G2), • a centralized processing unit (1) configured for: • estimate a first difference between a power of the first signal of interest (R) measured downstream of the first frequency converter (211) and a first saturation power (Psatù constituting a limit of a linear operating domain of the first channel (2R), • command an adjustment of the first gain (Gl) from the first deviation, so as to reduce the first deviation and maintain the power of the first signal of interest (2R) below the first saturation power (PSatv), • estimate a second difference between a power of the second signal of interest (L) measured downstream of the second frequency converter (212) and a second saturation power (Psatz) constituting a limit of a linear operating domain of the second channel (2L), • command an adjustment of the second gain (G2) from the second gap, so as to reduce the second gap and maintain the power of the second signal of interest (L) less than the second saturation power (PSitt2)-

2. System according to claim 1, wherein the first gain (G1) and the second gain (G2) are adjusted to identical values.

3. System according to any one of claims 1 and 2, wherein the centralized processing unit (1) is configured to: • calculate the first saturation power (R.^i) using a first model estimating how a saturation power varies in the first channel (2R) as a function of a frequency of a signal processed by the first channel (2R), • calculate the second saturation power (P$at2) using a second model estimating how a saturation power varies in the second channel (2L) as a function of a frequency of a signal processed by the second channel (2L).

4. System according to any one of claims 1 to 3, wherein the centralized processing unit (1) is configured to: • apply a spectral analysis to the first signal of interest (R), so as to determine the power of the first signal of interest measured, and / or • apply a spectral analysis to the second signal of interest (L), so as to determine the power of the second signal of interest measured.

5. System according to any one of claims 1 to 4, wherein: • the first deviation is also estimated from a first transmission gain applied to the first signal of interest (R) by a portion of the first channel (2R) connecting the first frequency converter (211) to the centralized processing unit (1), • the second deviation is also estimated from a second transmission gain applied to the second signal of interest (L) by a portion of the second channel (2L) connecting the second frequency converter (212) to the centralized processing unit (1).

6. System according to any one of claims 1 to 5, wherein: • the adjustment of the first gain (G1) is also controlled from a power recoil data dependent on a modulation scheme of the satellite signal, and / or • the adjustment of the second gain (G2) is also controlled from the power recoil data.

7. System according to any one of claims 1 to 6, wherein the satellite signal has frequencies in the Ka band and / or has a bandwidth greater than 1.4 GHz.

8. A system according to any one of claims 1 to 6, further comprising • a third channel (2A) for processing a deviation signal (A) produced from the satellite signal, the third channel (2A) comprising • a third frequency converter (213) configured to frequency-shift the deviation signal (A), the third frequency converter (213) and to apply a third gain (G3), • an estimator (3) arranged downstream of the third frequency converter (213), and configured to estimate an angle between a principal direction adopted by the antenna (A) and a propagation direction of the satellite signal from a satellite to the antenna (A), taking into account the adjustment of the first gain (G1) and the second gain (G2), • wherein the centralized processing unit (1) is further configured to control an adjustment of the third gain (G3).

9. Satellite signal receiving station comprising: • an antenna (A) configured to receive a satellite signal, • a system for receiving a satellite signal according to the preceding claim adapted to receive the signal

10. satellite, wherein the centralized processing unit (1) is configured to calculate a satellite signal power from the first adjusted gain (G1) and / or the second adjusted gain (G2), • an antenna control unit (4) configured to orient the antenna (A) from ephemeris data and satellite signal strength. Method for receiving a satellite signal acquired by an antenna (A), the satellite signal comprising a first signal of interest (R) and a second signal of interest (L) having different polarizations, the reception method comprising the following steps: • processing of the first signal of interest (R) via a first channel (2R) comprising a first frequency converter (211) which frequency-shifts the first signal of interest (R), the first frequency converter (211) applying a first gain (Gl), • processing of the second signal of interest (L) via a second channel (2L) comprising a second frequency converter (212) which frequency-shifts the second signal of interest (L), the second frequency converter (212) applying a second gain (G2), • estimation of a first difference between a power of the first signal of interest (R) measured downstream of the first frequency converter (211) and a first saturation power (Psati) constituting a limit of a linear operating domain of the first channel (2R), • control for adjusting the first gain (Gl) from the first deviation, so as to reduce the first deviation and keep the power of the first signal of interest lower (R) than the first saturation power (Psat\), • estimation of a second difference between a power of the second signal of interest (L) measured downstream of the second frequency converter (212) and a second saturation power (P^2) constituting a limit of a linear operating domain of the second channel (2L), second gain adjustment command (G2) from the second gap, so as to reduce the second gap and keep the power of the second signal of interest (L) lower than the second saturation power (Psat2)-