System for receiving a satellite signal

Abstract

The invention relates to a 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) which have 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 (21) comprising a second frequency converter (212) configured to frequency-shift the second signal of interest (21) 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 (Psati) constituting a bound of a linear operating range of the first channel (2R); - control an adjustment of the first gain (G1) on the basis of the first difference so as to reduce the first difference and keep the power of the first signal of interest (2R) lower than the first saturation power (Psati); - 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 (Psat2) constituting a bound of a linear operating range of the second channel (21); - control an adjustment of the second gain (G2) on the basis of the second difference so as to reduce the second difference and keep the power of the second signal of interest (L) lower than the second saturation power (Psat2).

Description

[0001] 1

[0002] DESCRIPTION

[0003] TITLE: SYSTEM FOR RECEIVING A SATELLITE SIGNAL

[0004] TECHNICAL FIELD

[0005] This disclosure relates to the general field of satellite communication and

[0006] 5 more particularly to processing applied to satellite signals received by a receiver.

[0007] STATE OF THE ART

[0008] The transmission of signals between satellites orbiting the Earth and ground stations is used in many applications, for example television, the internet, or

[0009] 10. 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 includes an amplifier, a fixed-gain frequency converter, and a transmission line.

[0010] 15. Transmission. The channel is statically dimensioned to verify certain performance criteria, notably limiting noise during satellite signal transmission and remaining within a linear operating range. The dimensioning is generally carried out for extreme conditions, including degraded weather conditions, to meet various availability objectives. Thus, the operation of the chain

[0011] A reception rate of 20 is mostly suboptimal.

[0012] 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 manage the power of the satellite signals received before the

[0013] 25 Implementation of digital processing.

[0014] To increase data rates and overcome spectrum occupancy limitations, modern satellite links use increasingly higher frequencies with wide bandwidths. Furthermore, the attenuation of transmitted satellite signals can vary depending on weather conditions or the type of satellite orbit.

[0015] 30 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 popular satellite links. Finally, the addition of local automatic gain controllers at the channel level introduces disturbances in related equipment functions, notably antenna position correction.

[0016] 5. DESCRIPTION OF THE INVENTION

[0017] One purpose of this disclosure is to enable the reception of a satellite signal by means that satisfy performance criteria (linear behavior and reduced noise sensitivity) regardless of the frequency band and bandwidth of the received signal.

[0018] 10 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:

[0019] • a first channel comprising a first configured frequency converter

[0020] 15 to frequency-shift the first signal of interest and to apply an initial gain,

[0021] • a second channel comprising a second frequency converter configured to frequency-shift the second signal of interest and to apply a second gain,

[0022] 20 • a centralized processing unit configured to: o estimate a first difference between a 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,

[0023] 25. To order an adjustment of the first gain based on the first deviation, so as to reduce the first deviation and maintain the power of the first signal of interest below the first saturation power; to estimate a second deviation between a power of the second signal of interest measured downstream of the second frequency converter and a second

[0024] 30 saturation power constituting a limit of a linear operating domain of the second channel, to control an adjustment of the second gain from the second deviation, so as to reduce the second deviation and keep the power of the second signal of interest below the second saturation power. 3

[0025] Dynamically adjusting the gains used by the first and second frequency converters allows the operation of the corresponding channels to be adapted so as to achieve the closest possible received signal power.

[0026] 5. Possible saturation power, and therefore better reception quality. Saturation in the channels is avoided. Furthermore, signals that are severely attenuated, for example by poor weather conditions, can be amplified. Using a centralized processing unit to control gain adjustments allows the above advantages to be achieved without having to make extensive modifications to the channels.

[0027] 10 In particular, this solution is less expensive than a solution that would consist of integrating an automatic gain controller specific to each channel.

[0028] 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.

[0029] 15. 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 channel gain values ​​also prevents disruption to channel operation and avoids interruptions in satellite signal transmission.

[0030] 20. The system for receiving a satellite signal may have the following advantageous and non-limiting characteristics, taken alone or in any technically possible combination:

[0031] - the first gain and the second gain are adjusted to identical values;

[0032] - The centralized processing unit is configured to:

[0033] 25 • 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

[0034] • Calculate the second saturation power using a second model estimating how the saturation power in the second channel varies as a function of a

[0035] 30 frequency of a signal processed by the second channel;

[0036] - The centralized processing unit is configured to:

[0037] • 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

[0038] • apply a spectral analysis to the second signal of interest, in order to determine

[0039] 35 the power of the second signal of interest measured; 4

[0040] - The first deviation 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

[0041] 5 of interest by a portion of the second channel connecting the second frequency converter to the centralized processing unit;

[0042] - the adjustment of the first gain is also controlled from a power feedback data dependent on a satellite signal modulation scheme, and / or the adjustment of the second gain is also controlled from the power feedback data;

[0043] 10 - the satellite signal has frequencies within the Ka band and / or has a bandwidth greater than 1.4 GHz;

[0044] - the system for receiving a satellite signal also includes

[0045] • a third channel specifically designed to process a deviation signal produced from the satellite signal, the third channel comprising

[0046] 15. 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

[0047] 20. The antenna and a direction of propagation of the satellite signal from a satellite to the antenna, taking into account the adjustment of the first gain and the second gain,

[0048] • in which the centralized processing unit is further configured to control an adjustment of the third gain.

[0049] 25. According to another aspect, a satellite signal receiving station is proposed, comprising:

[0050] • an antenna configured to receive a satellite signal,

[0051] • a system for receiving a satellite signal as described above, suitable for receiving the satellite signal, in which the centralized processing unit is

[0052] 30 configured to calculate satellite signal power from the first adjusted gain and / or the second adjusted gain,

[0053] • an antenna control unit configured to orient the antenna based on ephemeris data and satellite signal strength.

[0054] Finally, a method for receiving an acquired satellite signal is proposed.

[0055] 35 by an antenna, the satellite signal comprising a first signal of interest and a second signal of interest having different polarizations, the reception process comprising steps of:

[0056] • processing of the first signal of interest via a first channel comprising a first frequency converter which frequency-shifts the first signal of interest,

[0057] 5. The first frequency converter applying a first gain,

[0058] • 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,

[0059] 10 • estimation of a first difference between a 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,

[0060] • control for adjusting the first gain from the first deviation, so that

[0061] 15. Reduce the initial gap and maintain the power of the first signal of interest below the initial saturation power.

[0062] • 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

[0063] 20 second lane,

[0064] • 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.

[0065] DESCRIPTION OF THE FIGURES

[0066] 25 Other features, purposes 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:

[0067] Figure 1 schematically illustrates a state-of-the-art satellite signal receiving station, including a processing channel for receiving a polarization.

[0068] 30 Figure 2 schematically illustrates a satellite signal receiving station, comprising a processing channel to receive two polarizations and a processing channel to control the position of the antenna.

[0069] Figure 3 schematically illustrates the interactions between the channels and the centralized receiver of the receiving station in Figure 2.6

[0070] Figure 4 schematically illustrates a satellite signal receiving station according to a first embodiment of the invention.

[0071] Figure 5 schematically illustrates the interactions between the channels and the centralized receiver of the receiving station in Figure 4.

[0072] 5 Figure 6 is a flowchart representing a satellite signal reception process in one embodiment.

[0073] Across all figures, similar elements bear identical references.

[0074] DETAILED DESCRIPTION OF THE INVENTION

[0075] Ground stations are sized according to the desired link performance.

[0076] 10 and the power of the transmitting antenna.

[0077] 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.

[0078] 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. As is known, antenna A configured to receive a circularly polarized satellite signal comprises a right-hand circularly polarized (RHCP) antenna source.

[0079] 20 in English), 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 with 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 polarizations.

[0080] 25 corresponding circulars. 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.

[0081] Preferably, antenna A is also suitable for transmitting a deviation signal A produced by an antenna source from the satellite signal. Typically, the signal

[0082] 30 of deviation A is an output of the single antenna source as the signals of interest R,L.

[0083] 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 received signal strength, as antenna A can be highly directional.

[0084] 5 Each channel 2 includes a frequency converter 21 configured to frequency-shift the processed R,L signal of interest and to apply 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

[0085] 10 characteristics. Indeed, while 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

[0086] 15. The first gain G1, and the second channel 2L, comprising 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, G2 allows modification of the amplitude of the signal of interest R, L, in addition to applying the frequency shift. The applied frequency shift can be identical for the first converter.

[0087] 20 frequency 211 and the second frequency converter 212. The frequency offset can be constant and does not depend on the value of the first gain G1 and the second gain G2.

[0088] Preferably, the system for receiving a satellite signal also includes a third channel dedicated to processing the A-axis deviation signal and comprising a third frequency converter 213 configured to frequency-shift the signal

[0089] 25 of deviation and to apply a third gain G3.

[0090] As is known, the frequency converter 21 may include a mixer that combines, 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 signal frequency

[0091] 30 corresponds to the difference, and the other frequencies are removed. The resulting signal can then be amplified by applying the gain to compensate for conversion losses and / or adjust the signal level. The frequency converter 21 is preferably glitch-free.

[0092] Preferably, channel 2 includes an amplifier 22 upstream of the converter

[0093] Frequency 21, 35. Amplifier 22 is preferably a low-noise amplifier (LNA), placed at the output of the signal receiving antenna A. Amplifier 22 is configured to amplify the signal directly after reception to prevent transmission noise to receiver 100, typically located in the control room, from becoming excessive. This allows

[0094] 5 to increase 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.

[0095] The assembly formed by the amplifier 22 and the frequency converter 21 is generally called a radio frequency head. In general, the gains of

[0096] The amplifier 22 and the frequency converter 21, and therefore the gain of the radio frequency head, are configured for the maximum possible signal flow. The gains are static, meaning they are not changed 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 static gains

[0097] 15 can be performed for each satellite pass, taking into account the characteristics of the satellite and its trajectory, the characteristics of the ground station, and the weather conditions. More generally, channel 2 is sized to adapt the output power of the radio frequency 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

[0098] 20 here to dynamically modify the gains G1, G2 applied from instructions issued by the centralized processing unit 1.

[0099] 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.

[0100] 25 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. An addition of noise and an attenuation (or amplification) of the

[0101] 30 R,L interest signals processed can take place in the transmission line 20.

[0102] 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 R,L signals of interest. For example, the centralized processing unit 1 is configured to synchronize to an input signal.

[0103] 35 used to modulate a carrier signal, in amplitude, frequency or phase, in order to 9 decode the information transmitted by the satellite. Preferably, the centralized processing unit 1 is configured to calculate a satellite signal power P AGC from the first adjusted gain G1 and / or the second adjusted gain G2. The satellite signal power P AGC is an evaluation of the signal level transmitted by the satellite and received

[0104] 5 by antenna A.

[0105] Preferably, the receiver 100 includes an estimator 3 or deviation receiver (also called a "ddiiggiittaall ttrraacckkiinngg rreecceeiivveerr" in English) suitable for processing the deviation signal A. More precisely, the estimator 3 is arranged downstream of the third frequency converter 213, and configured to estimate an angle between the direction

[0106] 10. The main angle adopted by antenna A and the direction of propagation of the satellite signal from a satellite to antenna A, taking into account the adjustment of the first gain G1 and the second gain G2, i.e., as a function of the temporal variation 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 by algorithmic processing.

[0107] 15 complexes implemented by estimator 3.

[0108] In the illustrated embodiment, the ground station comprises the first channel 2R configured to transmit the right-hand polarized carrier signal R to the centralized processing unit 1 and the estimator 3, the second channel 2L configured to transmit the left-hand polarized carrier signal L to the centralized processing unit 1, and the third channel

[0109] 20 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.

[0110] Preferably, the receiver 100 includes an antenna control unit 4 (ACU), configured to orient antenna A based on ephemeris data and the satellite signal strength P AGC .

[0111] 25. As is known, 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

[0112] 30. Use ephemeris data to pre-position antenna A in the direction of the satellite.

[0113] Antenna control unit 4 can be connected to the estimator 3 or offset receiver and to the centralized processing unit 1. 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 precisely, 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 P AGC calculated by the centralized processing unit 1. Of

[0114] 5. Alternatively or complementaryly, the antenna control unit 4 is configured to improve positioning using the angle estimated and transmitted by the estimator 3.

[0115] Figure 2 schematically illustrates various elements of the centralized processing unit 1 that are commonly used. The centralized processing unit 1 comprises, by

[0116] 10. 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 P AGC .

[0117] In general, the automatic gain 5 controller may include a circuit of

[0118] 15. Closed-loop feedback control in an amplifier or a plurality of amplifiers in series. The gain of the amplifier of the internal automatic gain controller is configured to vary dynamically in order to maintain an appropriate 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 channels.

[0119] 20 of respective processing. In other words, the average or peak output signal level depends on the gain value of the automatic gain controller amplifier 5.

[0120] Typically, the automatic gain 5 controller is configured to regulate the carrier signal to a constant level. Here, the first automatic gain 5 controller takes as input the first signal of interest R, corresponding to the right-biased carrier signal.

[0121] 25 is processed by the first channel 2, and the second signal of interest L, corresponding to the left-biased carrier signal L, is processed by the second channel 2L. The automatic gain controller 5 provides at output a first regulated signal of interest Rr and a second regulated signal of interest Lr.

[0122] Demodulator 6 can be a second automatic gain controller. The demodulator

[0123] 30 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. 1 1

[0124] 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.

[0125] Power measurement unit 7 is configured to estimate the signal power at

[0126] 5 the input of the centralized processing unit 1, or more generally the power of the satellite signal P AGC , from the gain values ​​G5,G6. As illustrated in Figure 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 antenna A.

[0127] 10 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, in a frequency range between 26.5 GHz and 40 GHz, and especially for communications

[0128] 15 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 static radio frequency heads or frequency converters 21 with G1, G2 gain shows limitations when the dynamic range of the received satellite signal level increases. Typically, the frequency range defined by the International Union of

[0129] 20 telecommunications (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.

[0130] Preferably, the signal received by antenna A, emitted by the satellite, comprises spectrally efficient waveforms occupying the entire available bandwidth.

[0131] Typically, a total bandwidth greater than 1.4 GHz, for example, 1.5 GHz, is required. Such a signal demands a high signal-to-noise ratio (SNR) and exhibits a high peak-to-average power ratio (PAPR). Consequently, the satellite signal is highly sensitive to the linearity of channel 2 behavior.

[0132] 30 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 can 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 12 by atmospheric humidity, which are very significant in the Ka frequency band, variable propagation losses related to the distance traveled by the waves.

[0133] 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. The requirements in

[0134] Five availability rate terms 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 the ULT.

[0135] More specifically, the difference in level between the maximum satellite signal strength

[0136] 10 is permissible to remain within a linear operating range of channel 2, and the minimum power below which the thermal noise introduced by the frequency converter 21 no longer allows an error-free satellite link decreases with increasing bandwidth. The dynamic range required for this gap increases with environmental humidity. Furthermore, the level dynamic range

[0137] 15 tolerable at the input of the frequency converter 21 also depends on the waveform retained in the modulation of the satellite signal, that is to say the modulation scheme chosen, for example among the different modulation schemes of the DVB-S2 transmission standard, and the setting of the G1,G2 gains of the channels 2.

[0138] Thus, the frequency converters 211, 212 used with a fixed gain G1, G2 and put into

[0139] The 20 works in the ground station illustrated in figures 1 and 2 do not allow us to consider satellite links with a high availability rate in the case of very high speed transmissions in Ka band.

[0140] The centralized processing unit 1 is configured to: estimate a first difference between a power P R of the first signal of interest R measured

[0141] 25 downstream of the first frequency converter 211 and a first saturation power P satlConstituting a boundary 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 P R of the first signal of interest R

[0142] 30 lower than the first saturation power P sat i, estimate a second difference between a power P L of the second signal of interest L measured downstream of the second frequency converter 212 and a second saturation power P sat2 constituting a boundary of a linear operating domain of the second channel 2L, 13 control an adjustment of the second gain G2 from the second deviation, so as to reduce the second deviation and maintain the power P L of the second signal of interest L less than the second saturation power P sat 2-

[0143] With reference to Figure 4, the centralized processing unit 1 includes a controller

[0144] 5 external automatic gain 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.

[0145] The external automatic gain controller 11 is connected to the first frequency converter 211 and the second frequency converter 212. For example, the controller

[0146] 10 automatic external gain 11 is connected to each frequency converter 21 via a serial bus type communication bus, or a low data rate Ethernet type link.

[0147] Preferably, the external automatic gain controller 11 is connected to the frequency converter 21 of each channel linking antenna A to the centralized processing unit 1.

[0148] 15 In the illustrated embodiment, the external automatic gain controller 11 is thus also connected to the third frequency converter 213.

[0149] The external automatic gain controller 11 is configured to centrally control the respective gains G1 and G2 of the frequency converters 211 and 212. Centralizing the control process allows for consideration of relative values

[0150] 20 of the gains G1, G2 and the characteristics of the different channels 2R, 2L, in particular in order to preserve the differential levels between the first channel 2R and the second channel 2L.

[0151] Preferably, the first gain G1 and the second gain G2 are adjusted to identical values. The centralized processing unit 1 allows for coordinated adjustment of the gain values. This reduces the risk of preventing the algorithms from functioning correctly.

[0152] 25 implemented by estimator 3 and to lead to erroneous values ​​of the estimated angle used to orient antenna A.

[0153] Preferably, the external automatic gain controller 11 is also 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 dynamic adjustment of the third gain G3

[0154] 30 depending on the first and / or second power gap. The second link is not a control, but allows the sharing of adjustment information, i.e., the adjusted values ​​of the first gain G1 and / or the second gain G2 of the frequency converters 211, 212, so that the algorithms implemented by estimator 3 can function correctly. 14

[0155] Referring to Figure 5, the centralized processing unit 1 may include a deviation measurement unit 8. The deviation measurement unit 8 is configured to perform first and second deviation estimation. Typically, the first deviation is estimated from the gain G5 of the internal gain automatic controller 5 and the first signal

[0156] 5 of regulated interest Rr, and the second deviation is estimated from the gain G5 and the second regulated interest signal Lr. The first and second deviations will more generally be referred to as the "level deviation e sat The level gap sat This corresponds to a deviation, that is, a difference, from the saturation power, beyond which channel 2 no longer operates linearly. As explained previously, in order to

[0157] 10. To improve satellite signal reception, it is necessary to maintain 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.

[0158] 15. Preferably, the centralized processing unit 1 is configured to:

[0159] • Calculate the first saturation power P sat i ^ using a first model Psati(f) estimating how a saturation power P varies satl in the first channel 2R as a function of a frequency of a signal processed by the first channel 2R; and / or

[0160] • Calculate the second saturation power P sat2 using a second model

[0161] 20 P sat2( / ) 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.

[0162] The calculation can be implemented by a deviation measurement unit 8. Preferably, the centralized processing unit 1 stores in memory channel characterization data 2, i.e., information enabling the characterization of the domain of

[0163] 25 Linear operation of channels 2. RF characterization data can be obtained from a characterization, by measurement, for each of the 2R, 2L, 2A channels 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 cable type 20 and the characteristics of the

[0164] 30 frequency converters 21, including the respective gains G1, G2, G3.

[0165] More generally, from the lane characterization data 2, the deviation measurement unit 8 can calculate a model used to evaluate the level difference e sat including in particular the saturation power P sat not to be exceeded at the output of the frequency converter 21 so as not to saturate the frequency converter 21 or the 15 transmission line 20 between the frequency converter 21 and the centralized processing unit 1.

[0166] Preferably, the calculation of the level gap e sat The saturation measurement takes into account a power measurement at the input of the centralized processing unit 1. The measurement of

[0167] 5 power 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.

[0168] More generally, the centralized processing unit 1 can be configured to:

[0169] 10 • Apply a spectral analysis to the first signal of interest R, so as to determine the power P R of the first measured signal of interest R; and / or

[0170] • apply a spectral analysis to the second signal of interest L, so as to determine the power P L of the second signal of interest L measured.

[0171] The powers P R , P L The first and second R,L signals of interest measured depend on

[0172] 15 the frequency. Spectral analysis can be implemented before regulation by the automatic controller with internal gain 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 controller with internal gain 5. In other words, the deviation measurement unit 8 is configured to determine the level deviation e sat from a

[0173] 20 Local power measurement P mes (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.

[0174] Preferably, the first deviation is also estimated from a first transmission gain Gt1 applied to the first signal of interest R by a portion of the first channel

[0175] 25 2R connecting the first frequency converter 211 to the centralized processing unit 1, and / or the second deviation is also estimated from a second transmission gain Gt2 applied to the second signal of interest L by a portion of the second channel 21 connecting the second frequency converter 212 to the centralized processing unit 1. The first and second transmission gains Gt1, Gt2 typically depend on the

[0176] 30 frequency of the signal transmitted by the transmission line 20, and / or characteristics of the 2R,2L channel. These are known, typically evaluated upstream or provided by the manufacturer. They may take losses into account.

[0177] More specifically, the deviation measurement unit 8 can take into account known characteristics of the radio frequency cables or transmission lines 20 through which 16 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 sat at the output of the respective frequency converter 211,212.

[0178] The centralized processing unit 1, for example via the measuring unit

[0179] 5 of deviation 8, can implement the following calculation to obtain the level difference e sat in decibels relative to the saturation point:

[0180] With B the frequency range corresponding to the bandwidth of the satellite signal. The first and second deviations can be equal to the level difference e sat .

[0181] 10 More generally, we can define the first gap e satl and the second gap

[0182] The adjustment of the first gain G1 and the second gain G2 can be carried out so as to reduce their respective gaps. Typically, the centralized processing unit 1 implements, typically via the external automatic gain controller 11, a

[0183] 15 Classical regulation to vary the gains G1, G2 so that the respective differences tend towards zero.

[0184] Preferably, the centralized processing unit 1 is also 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.

[0185] 20 Preferably, the adjustment of the first gain G1 is also controlled from a power recoil data R dBdepending on a satellite signal modulation scheme, and / or the adjustment of the second gain G2 is also controlled from the power recoil data R dB Typically, the power recoil data R dB is common to the first track 2R and the second track 2L.

[0186] 25 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 recoil power value R dB relative to the saturation power P sat of the respective 2R,2L channel, for the frequency of the signal transmitted by the 2R,2L channel.

[0187] 30 The power recoil evaluation can take into account modulation characteristics, for example the waveform type, or the peak power to mean power ratio (PAPMR) of the satellite signal. The centralized processing unit 1, typically via the recoil evaluation unit 9, is configured to evaluate the power recoil. dB according to different modes of implementation.

[0188] In one embodiment, the power recoil taken into account in the adjustment of the

[0189] 5. Gains G1, G2 can be a static quantity. In this case, the power recoil R dBis determined in advance and stored by the centralized processing unit 1 in a dedicated memory. The power backoff is chosen to ensure 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 power backoff data

[0190] The stored value 10 can be calculated based on a worst-case use case for the ground station, or a worst-case scenario associated with the configuration of the central processing unit 1, for example. Thus, in the absence of available data, typically information on the type of modulation used, the backscatter value is set so that the central processing unit 1 can operate regardless of the modulation scheme used. Depending on the scheme

[0191] 15 modulation, the operating point of channel 2 may be suboptimal.

[0192] Preferably, the centralized processing unit 1 is configured to dynamically evaluate the power backlash. This allows an optimal operating point to be reached for each of the processing channels 2. In this case, information about the modulation scheme can be transmitted with the satellite signal and decoded by

[0193] 20. Centralized Processing Unit 1. Thus, if data is available, Centralized Processing Unit 1 is configured to provide a recoil value R dB Optimal setback data R dB can be obtained in the case of a static configuration of the centralized processing unit 1.

[0194] Preferably, the centralized processing unit includes an adaptive system (“Adaptive

[0195] 25 Coding and Modulation (or ACM). During adaptive operation, the link margin, i.e., the availability margin, can be converted into increased throughput when conditions are favorable. This allows for maximizing throughput under all the aforementioned conditions.

[0196] More specifically, the power recoil data R dB can be evaluated according to different

[0197] 30 ways depending on the available data. For example, the recoil evaluation unit 9 can be configured to infer the recoil power data R dB from the configuration of the centralized processing unit 1. Typically, the centralized processing unit 1 transmits its configuration information, i.e., the type of modulation used, during its initialization, to the recoil evaluation unit 9. The recoil evaluation unit 9 can then calculate the recoil data R. dBoptimal based on peak power which depends on the modulation scheme used.

[0198] Typically, the optimal power setback can be defined based on the saturation point. For example, centralized processing unit 1 can be configured to

[0199] 5 calculate the power recoil from a lookup table between modulation schemes and satellite signal power functions, the lookup table being stored in the memory of the centralized processing unit.

[0200] In the case of QPSK or 8PSK modulation of the DVB-S2 standard, the R-value data dB may be minimal, typically increased by a margin between 0 dB and 1 dB

[0201] 10 relative to the saturation point. In the case of M-APSK modulation, with M = 16, M = 32 or M = 64, the recoil value R dBis typically increased by a margin of between 1 dB and 3 dB relative to the saturation point. For example, for 16APSK modulation, the recoil value R dB can be increased by 1.05 dB relative to the saturation point. For 32APSK modulation, the recoil value R dB can

[0202] 15. This value should be increased by 2.05 dB relative to the saturation point. For 64APSK modulation, the recoil value R dB can be increased by 2.84 dB relative to the saturation point.

[0203] Additionally, the power recoil data R dB can be deduced from the modulation decoded by the centralized processing unit 1 during transmission. At

[0204] 20. During the mission, that is, when an exchange of information takes place via the satellite link, information from the configuration used by the centralized processing unit 1 can be transmitted to the recoil evaluation unit 9 to modify the recoil data R dB Typically, in the case of a dynamic configuration of the centralized processing unit 1 (ACM operation), DVB-S2 type transmissions can

[0205] 25. Modify the modulation scheme used during transmission. The recoil evaluation unit 9 is preferably configured to modify the power recoil data R dB depending on the evolution of the modulation scheme.

[0206] In the illustrated embodiment, the centralized processing unit 1 includes a gap calculation unit 10 configured to correct the level e gap sat relative to the point of

[0207] 30 saturation 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 deviation e dB based on the results of the calculation processes for the setback and the level difference relative to the saturation point. Typically, the difference e dB The value supplied to the external automatic gain controller 11 is obtained by the following formula: e dB = R dB + 19th sat In an implementation method that does not take into account the setback factor, we would have

[0208] ®dB ^sat'

[0209] The gap e dB is used by the external automatic gain controller 11 driving the gain of the frequency converters 21. Preferably, the rate of change of the first gain G1

[0210] 5 and / or the rate of change of the second gain G2 is bounded. This prevents sudden changes in the gains of the frequency converters 211, 212, which could lead to breaks or interruptions in the satellite link between antenna A and the centralized processing unit 1.

[0211] Preferably, the gain adjustment G1, G2 from the external automatic gain controller

[0212] 10 and 11 are monitored by the power measurement unit 7. In other words, the external automatic gain controller 11 is configured to transmit the adjusted gains G1 and G2 to the power measurement unit 7. This allows the signal level variations at antenna 4 to be reconstructed and an appropriate value for the satellite signal power P to be calculated. AGC transmitted to antenna control unit 4.

[0213] 15 A reception process implemented by the system described above includes the following steps.

[0214] During step S11, 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

[0215] 20 first frequency converter 211.

[0216] During an S21 step, the second signal of interest is processed via the second channel 2L comprising the second frequency converter 212. The S21 processing allows the second signal of interest 2L to be frequency shifted to apply the second gain G2 of the second frequency converter.

[0217] 25. Processing steps S11 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 processing steps S11 and S21. Steps S11 and S21 are performed continuously, i.e., during the

[0218] 30. Reception of the satellite signal by antenna A.

[0219] During an estimation step S12, the centralized processing unit 1 estimates the first difference between the power P R of the first signal of interest R measured downstream of the first frequency converter 211 and the first saturation power P satlconstituting a 20 limit of the linear operating domain of the first 2R channel. 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 for frequent updating of the first deviation value and therefore a better adjustment of the first gain G1.

[0220] 5 The estimation of the first gap is done from the first signal of interest processed during step S11.

[0221] Similarly, during an S22 estimation step, the centralized processing unit 1 estimates the second difference between the power P L of the second signal of interest L measured downstream of the second frequency converter 212 and the second power of

[0222] 10 saturation P sat2constituting a limit of the linear operating domain of the second channel 21. Similarly, step S22 may frequently, typically at regular intervals and after processing of the second signal of interest during step S21. Steps S12 and S22 may take place simultaneously or not.

[0223] The receiving process also includes an S13 adjustment command step of the

[0224] 15 first gain G1 from the first gap, so as to reduce the first gap and maintain the power P R of the first signal of interest 2R less than the first saturation power P satl Similarly, the adjustment command step S13 can be implemented frequently and requires the estimation of the first deviation from step S12.

[0225] Similarly, the receiving process includes an S23 ordering step

[0226] 20 adjustment of the second gain G2 from the second gap, so as to reduce the second gap and maintain the power P L of the second signal of interest L less than the second saturation power P sat2 The adjustment command step S23 can be implemented frequently and requires estimating the second deviation from step S22. Therefore, steps S23 and S13 can be implemented simultaneously or not.

[0227] 25 In particular, the steps do not necessarily follow the order shown in Figure 6, with steps S12 and S22 for estimating the deviation being independent and steps S13 and S23 for controlling the adjustment being independent, and thus being able to be carried out simultaneously or in a deferred manner.

Claims

1. 21 DEMANDS 1. 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: 5 • 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 (G1), • a second channel (21) comprising a second frequency converter (212) configured to frequency-shift the second signal of interest (21), the 10. Second frequency converter (212) and to apply a second gain (G2), • a centralized processing unit (1) configured to: o 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 (P sat i) constituting a boundary of a domain 15. Linear operation of the first channel (2R), to control 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 (P sa ti), to estimate a second difference between a power of the second signal of interest 20 (L) measured downstream of the second frequency converter (212) and a second saturation power (P sat2) constituting a limit of a linear operating domain of the second channel (21), to control an adjustment of the second gain (G2) from the second deviation, so as to reduce the second deviation and maintain the power of the 25 second signal of interest (L) less than the second saturation power (P sat2 y 2. System according to claim 1, wherein the first gain (G1) and the second gain (G2) are adjusted to identical values.

3. A system according to any one of claims 1 and 2, wherein the unit of 30. Centralized processing (1) is configured for: • calculate the first saturation power (Psati) using a first model estimating how a saturation power varies in the first channel (2R) as a function of the frequency of a signal processed by the first channel (2R), 22 • calculate the second saturation power (P sat2) 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. A system according to any one of claims 1 to 3, wherein the unit 5. Centralized processing (1) is configured for: • 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. 10.

5. A 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), 15 • The second gap is also estimated from a second transmission gain applied to the second signal of interest (L) by a portion of the second channel (21) linking the second frequency converter (212) to the centralized processing unit (1).

6. A system according to any one of claims 1 to 5, wherein: 20 • The adjustment of the first gain (G1) is also controlled from a power feedback data dependent on a satellite signal modulation scheme, and / or • The adjustment of the second gain (G2) is also controlled from the power recoil data. 25 7. System according to any one of claims 1 to 6, wherein the satellite signal has frequencies within the Ka band and / or has a bandwidth greater than 1.4 GHz.

8. A system according to any one of claims 1 to 7, further comprising • a third channel (2A) suitable for processing a deviation signal (A) produced from 30 of the satellite signal, the third channel (2A) comprising 23 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), O an estimator (3) arranged downstream of the third frequency converter 5 (213), and configured to estimate an angle between a principal direction adopted by the antenna (A) and a 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), • in which the centralized processing unit (1) is further configured for 10. Order 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 any one of claims 1 to 8, the system being suitable for receiving the satellite signal, in 15 in which 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. 20 10. 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 25 first signal of interest (R), the first frequency converter (211) applying a first gain (G1), • processing of the second signal of interest (L) via a second channel (21) comprising a second frequency converter (212) which frequency-shifts the second signal of interest (L), the second frequency converter (212) 30 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 (P sat i) constituting a boundary of a linear operating domain of the first channel (2R), 24 • control for adjusting the first gain (G1) 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 (P sa ti), • estimation of a second difference between the power of the second signal of interest 5 (L) measured downstream of the second frequency converter (212) and a second saturation power (P sat 2) constituting a boundary of a linear operating domain of the second channel (21), • Adjustment control for the second gain (G2) based on the second gap, so as to reduce the second gap and maintain the strength of the second signal of interest 10 (L) less than the second saturation power ^Psat2\

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