• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    The present invention relates to a receiver device for a communication system. The receiver is arranged to receive a signal comprising several transponder signals each containing a plurality of modulated signals and comprising: - an adjustable spectral filter (262) configurable to select a desired transmponder signal (270), - means (263) for performing a non-linear transformation on the selected desired transponder signal, the non-linear transformation being represented by a set of parameter values, - at least one receive filter (264) configurable to select at least one desired modulated signal from the non-linear linear transformed selected desired transponder signal, means for measuring the performance for determining one or more performance metrics on at least one modulated signal of the plurality of modulated signals contained in the desired transponder signal, to obtain the set of parameter values.
    公开号:BE1022351B1
    申请号:E2015/5398
    申请日:2015-06-26
    公开日:2016-03-24
    发明作者:Frederik Simoens；Daniel Delaruelle
    申请人:Newtec Cy N.V.；
    IPC主号:
    专利说明:

    Field of the Invention The present invention relates generally to the field of techniques for reducing signal distortion in a digital communication system. More specifically, it relates to receiver compensation techniques to reduce the distortion introduced through a non-linear communication channel.
    Background of the Invention The present invention is about reducing distortion on one or more modulated signals (also called modulated carriers) that are outputted over a non-linear channel. An example of such a channel is a satellite communication channel.
    In a satellite communication system, the ground station amplifier and / or the satellite amplifier operate close to their saturation point in order to make optimum use of the available power sources. When the amplifier is operating in its non-linear range, it distorts the signal (this type of distortion is called self-distortion) and causes frequency regrowth, ie, it increases the bandwidth of the signal after the amplifier relative to the bandwidth that it signal for the amplifier.
    Furthermore, in order to make optimum use of the available bandwidth sources, different modulated signals are typically placed close to each other in the frequency domain, with little or no frequency spacing between the signals (called guard bands). Due to the non-linear nature of the channel, these signals interfere with each other. The distortion caused by this interference is called intermodulation.
    In summary, a modulated signal undergoes two forms of distortion: self-distortion (distortion of its own signal) and intermodulation (interference of other modulated signals) due to non-linear amplification of its own signal and of other modulated signals, respectively. When modulated signals undergo self-distortion and intermodulation, the reliability of the communication will deteriorate.
    A typical satellite communication configuration is shown in Fig. 1. The satellite communication system 100 includes a transmission segment 110, a satellite segment 130, and a receiving segment 160. The transmission segment includes one or more transmitters, typically referred to as modulators. The modulators in the transmission segment 110 may be placed together, but are often geographically separated. A modulator 111 transmits a modulated signal 121 to a satellite. The modulated carrier exhibits a certain bandwidth by carrying a modulated signal, which is typically protected by an error-correcting code. For example, a transmission format can be, but is not limited to, DVB-S, DVB-S2 or DVB-S2X. Other modulated signals transmitted by other modulators are typically placed next to carrier 121.
    A typical uplink spectrum is shown in 120. A person skilled in the art will understand that it is also possible to send out carriers with partially or fully overlapping bandwidths. In a bidirectional link, for example, one can place the forward and return carrier in the same bandwidth. In this example, the receiver can then subtract its own (known) carrier from the received signal, before demodulating the desired (unknown) modulated signal.
    The uplink signal 120 arrives in the input portion of the satellite. The satellite comprises one or more transponders 130. A transponder comprises an input multiplexing (IMUX) filter 131, a traveling waveform amplifier (TWTA) 132 and an output multiplexing (OMUX) filter 133. A transponder also contains other components, such as up- and down converters, but these are less relevant to the present invention and are therefore omitted in FIG. 1.
    Because of the IMUX filter 131, only a limited number of modulated signals are transmitted to the input of the TWTA 132. A TWTA in a transponder therefore has only a part of the full uplink spectrum at its input. In Fig. 1, carrier 121 passes through the IMUX and appears as carrier 141 in the output signal 140 of the IMUX. The TWTA 132 is typically used close to its saturation point. As a result of the non-linear behavior in the TWTA, the TWTA output spectrum 142 is influenced by inband and out-of-band distortion. The latter is called spectral regrowth, which increases the original bandwidth 140. The first is called self-distortion. The OMUX filter 133 removes the spectral components that exceed the bandwidth assigned to the corresponding transponder, so that the spectra of the output signals of the different transponders are non-overlapping before the recombination 134 takes place. Carrier 141 passes through the OMUX and appears as carrier 151 in the downlink spectrum 150. The useful signal in 151 is influenced by self-distortion and intermodulation of neighboring modulated signals within the spectrum allocated to the corresponding transponder.
    As illustrated in FIG. 1, a receiver 160 according to the prior art can be used to receive one specific modulated signal present in the signal 150. This receiver includes a down-converter 161, a matched filter 162 that filters out a single carrier (e.g., carrier 151) and produces a series of received data symbols. Finally, a decoder 163 attempts to retrieve the transmitted information bits from the received data symbols. One of ordinary skill in the art understands that appropriate synchronization is required before performing the decoding; for simplicity, however, this is not shown in the figure. A prior art receiver typically treats self-distortion and intermodulation as additional noise.
    A number of solutions are possible to control and reduce self-distortion and intermodulation in a satellite communication system. One possibility is to apply predistortion to one or more modulated carriers before sending them out, with the intention of anticipating the distortion caused by the carriers through the non-linear channel and reducing this distortion. Several solutions have been proposed in the past that apply signal manipulations in the transmission segment in line with this technique. However, the technique has a number of disadvantages which are listed below.
    The first disadvantage is that knowledge of the channel characteristics on the transmitter side is required or must be learned. This knowledge may not be available or inaccurate, thereby reducing the efficiency of predistortion. A second disadvantage is that in case several modulated signals are applied via the same non-linear channel, they must be pre-sorted together. This can only be done if these modulated signals are output from the same geographical location. Even in that case, however, it is known that the joint predistor of different carriers is an extremely computationally intensive operation.
    In another approach, self-distortion and intermodulation is reduced by performing a corrective action in the receiver segment. Few solutions from the state of the art make use of this strategy. US7263144 and US7242725 describe how distortion must be compensated for a single modulated signal that is forwarded over a non-linear channel. The invention described in US8331511 presents a method for jointly eliminating non-linear interference for multi-carrier transmission. The method makes it possible to demodulate and decode a multitude of carriers together, eliminating adjacent channel interference between neighboring channels. This approach offers several disadvantages. The first disadvantage is that corrective action is needed for all carriers. In certain scenarios, people are only interested in the data of one specific carrier. Moreover, the modulation parameters used by the other carriers are not necessarily known to the receiver. A second disadvantage is that the complexity of this receiver is relatively high. This can be remedied in part by only glancing interference from directly adjacent carriers. This naturally results in a certain loss of performance.
    Consequently, there is a need for a solution of low complexity that allows to reduce non-linear distortion on the receiver side.
    Summary of the Invention It is an object of embodiments of the present invention to provide a compensation method and circuit of low complexity that are capable of reducing the self-distortion and intermodulation that occur when one or more carriers are deployed. over a non-linear channel.
    The above object is achieved by the solution according to the present invention.
    In a first aspect, the invention relates to a method to compensate for distortion in a receiver of a communication system. The method comprises: - receiving a signal comprising a plurality of transponder signals, each containing a plurality of modulated signals, - applying the received signal to an adaptable spectral filter, the spectral filter being configurable to select a desired transponder signal, - performing a non-linear transformation on the selected desired transponder signal, the non-linear transformation being represented by a set of parameter values based on one or more performance metrics, - applying the non-linearly transformed selected desired transponder signal to at least one receive filter, said at least one receive filter set to select at least one desired modulated signal, wherein the one or more performance metrics are determined on at least one modulated signal of the plurality of modulated signals contained in the desired transponder signal.
    The proposed solution indeed allows to reduce self-distortion and intermodulation. A selective spectral filter in the receiver is configured to select a transponder signal of interest. At least the bandwidth and the central frequency of the transponder signal are used to configure the selective spectral filter. The resulting signal still contains a plurality of modulated signals. All of these modulated signals have undergone the same non-linearity. A non-linear transformation is then applied to compensate for the non-linear distortion introduced by the channel into this plurality of modulated signals. The applied non-linear transformation can be represented by a set of parameter values. These parameter values are determined by using one or more performance metrics. After the non-linear transformation block, a receive filter is provided, preferably a matched filter, in which the carrier whose data is interested is selected.
    In a preferred embodiment, the non-linear transformation is given as a product of a first function that operates on the amplitude of the selected desired transponder signal and a second function that operates on the phase of the selected desired transponder signal.
    In one embodiment, the first function that acts on the amplitude and the second function that works on the phase are polynomial functions.
    In a preferred embodiment, the method also includes a step of performing a decoding operation on the selected modulated signal. Advantageously, the set of parameter values representing the non-linear transformation is determined by means of a performance metric supplied by an error-correcting decoder. In one embodiment, the number of iterations required to achieve error-free decoding is minimized in the performance metric supplied by the error-correcting decoder.
    In an alternative embodiment, a weighted sum of the number of unsatisfactory parity check nodes in different iterations in the decoding process is minimized in the performance metric provided by said error-correcting decoder.
    In another embodiment, the signal-to-noise-plus distortion ratio of the received signal is used as a performance metric.
    In yet another embodiment, the set of parameter values is selected from a plurality of predefined sets of parameter values.
    The adjustable spectral filter is preferably configured by taking into account at least the central frequency and the bandwidth of the desired transponder signal.
    In another embodiment, the at least one desired modulated signal on which the one or more performance metrics are determined overlaps, at least in part, with one or more other known modulated signals of the plurality of modulated signals of the selected desired transponder signal and becomes a received version of the one or more known modulated signals subtracted from the at least one desired modulated signal and the result of that subtraction is used in the one or more performance metrics.
    In another aspect, the invention relates to a receiver device for a communication system, adapted to receive a signal comprising a plurality of transponder signals, each containing a plurality of modulated signals. The receiver device comprises - an adjustable spectral filter configurable for selecting a desired transponder signal, - means for performing a non-linear transformation on the selected desired transponder signal, the non-linear transformation being represented by a set of parameter values, at least one receive filter configurable to select at least one desired modulated signal from the non-linearly transformed selected desired transponder signal, - means for measuring the performance for determining a plurality of performance metrics on at least one modulated signal from the plurality of modulated signals contained in the desired transponder signal to obtain the set of parameter values.
    In one embodiment, the receiver device comprises a decoding unit for decoding the selected at least one desired modulated signal.
    In a typical embodiment, the receiver device comprises a down conversion mixer adapted to provide an input signal to the adjustable spectral filter.
    In another embodiment, the means for measuring the performance is arranged to receive from the at least one desired modulated signal on which the one or more performance metrics are determined, a received version of the one or more other known modulated signals from the plurality of subtract modulated signals from the selected desired transponder signal and to use the result of that subtraction in the one or more performance metrics.
    The invention relates to a satellite communication system comprising a receiver device as described above.
    In order to summarize the invention and the realized advantages over the prior art, certain objects and advantages of the invention have been described above. It goes without saying that all such objectives or advantages are not necessarily achieved according to one specific embodiment of the invention. Thus, for example, persons skilled in the art will recognize that the invention may be embodied or embodied in a manner that achieves or optimizes one advantage or group of benefits as described herein, without necessarily realizing other goals or benefits described or suggested herein. .
    The above and other aspects of the invention will become clear and further explained with reference to the embodiment (s) described below.
    Brief description of the drawings The invention will now be further described, by way of example, with reference to the accompanying drawings, in which like reference numerals refer to like elements in the various figures.
    FIG. 1 illustrates a satellite communication system as known in the art, wherein modulators are used to transmit modulated carriers over one or more satellite transponders. A receiver is used to demodulate and decode one or more carriers.
    FIG. 2 illustrates a satellite communication system, wherein a receiver applying the present invention, which allows the self-distortion and intermodulation to be reduced when demodulating and decoding one particular modulated signal.
    FIG. 3 illustrates a receiver employing the present invention for the demodulation and decoding of multiple modulated signals.
    FIG. 4a illustrates a scatter diagram of the received symbols at the decoder input in a prior art communication system. FIG. 4b shows a scatter diagram of the received symbols at the decoder input when using a receiver according to the present invention.
    Detailed Description of Illustrative Embodiments The present invention will be described with reference to specific embodiments and with reference to certain drawings, but the invention is not limited thereto, but is only limited by the claims.
    In addition, the terms first, second and so on are used in the description and in the claims to distinguish between similar elements and not necessarily for describing a sequence, either in time, in space, in terms of importance or in any other way. It is to be understood that the terms used are interchangeable under proper conditions and that the embodiments of the invention described herein are capable of operating in sequences other than those described or illustrated herein.
    It is to be noted that the term "comprising" as used in the claims should not be interpreted as being limited to the means given thereafter; it does not exclude other elements or steps. It must therefore be interpreted as a specification of the presence of the listed features, units, steps or components referred to, but it does not exclude the presence or addition of one or more other features, units, steps or components or groups thereof. Therefore, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of parts A and B. It means that with regard to the present invention, the only relevant parts of the device A and B to be.
    References in this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or feature described in connection with the embodiment is included in at least one embodiment of the present invention. Statements of the phrase "in one embodiment" or "in an embodiment" at different places in this specification do not necessarily all refer to the same embodiment, but it is possible. Furthermore, the specific features, structures or characteristics may be combined in any suitable manner in one or more embodiments, as will be apparent to those skilled in the art from this disclosure.
    In a similar manner, it should be noted that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped into a single embodiment, figure, or description thereof to streamline the disclosure and understanding of one or more of the facilitate various inventive aspects. However, this method of disclosure should not be interpreted as an expression of an intention that the claimed invention requires more features than expressly stated in each claim. As shown in the following claims, the inventive aspects lie in less than all the features of a single preceding disclosed embodiment. Therefore, the claims that follow the detailed description are hereby explicitly included in this detailed description, wherein each claim stands on its own as a separate embodiment of the present invention.
    In addition, since some embodiments described herein include some, but not other, features included in other embodiments, combinations of features of different embodiments are intended to fall within the scope of the invention and form different embodiments, such as will be understood by someone skilled in this field. For example, in the following claims, any of the claimed embodiments can be used in any combination.
    It should be noted that the use of certain terminology in describing certain aspects of the invention does not imply that the terminology herein is redefined to be limited to any specific features of the features or aspects of the invention with which that terminology is associated.
    In the description given here, numerous specific details are set forth. However, it is understood that embodiments of the invention can be worked out without these specific details. In other cases, well-known methods, structures and techniques were not shown in detail in order not to obstruct the understanding of this description.
    The present invention proposes a post-compensation method to reduce intermodulation and self-distortion at the receiver before decoding.
    The method of this invention can be used in a system where one or more (adjacent or spaced) transmitters communicate over a non-linear channel with one or more receivers. An example of such a system is a satellite communication system, as shown in FIG. 1 and FIG. 2.
    Fig. 2 illustrates a satellite communication system 200 adapted to apply the proposed post-compensation method. Flet transmission segment 210 and satellite segment 230 are similar to the transmission segment 110 and satellite segment 130 described in FIG. 1. Note that the transmit segment 210 includes one or more modulators that are not necessarily placed together.
    Fig. 2 considers an embodiment of a receiver device according to the present invention. The receiver 260 attempts to recover the data transmitted by a particular carrier. This carrier is referred to as the desired carrier. It bears reference sign 221 on the transmitter and 251 on the receiver input.
    A receiver adapted to use the invention typically comprises a down converter 261, followed by a selective filter 262. The input x (t) of this selective filter can be written as
    (1) where (t)) represents the signal received from a given desired transponder, designated A. The desired transponder is defined as the transponder that carries the desired modulated signal, i.e., the modulated signal that carries data in which one is interested. The transmitted signal sA (t) is amplified by the TWTA transponder. The transponder and the down conversion operation can be modeled by a non-linear function). Note that this function is not necessarily memoryless. Similarly, the other terms / wl-b (sb (0) << / wl-w (% (0) are the down-converted signals from transponders other than the desired transponder. The term w (t) represents the additive noise .
    The purpose of the selective filter 262 is to suppress all terms in equation (1), except for the term corresponding to the desired transponder. The signal sA (t) that is sent over this desired transponder can contain one or more modulated signals. One of these modulated signals is the signal 221 that carries the data in which one is interested. The output of the selective filter can be written as
    (2) wherein w (t) represents the filtered additive noise term. As is clear from equation (2), the output 270 of this selective filter 262 contains only the carriers that are outputted over the same non-linearity 232. Note that this selective filter can be implemented as an analog or a digital filter.
    The filter output 270 is applied via a non-linear transformation function, which can be modeled by a non-linear transformation 263. The output of the non-linear transformation function can be written as
    (3) where a non-linear transformation represents characterized by a finite set of parameters pA. The non-linear transformation function as well as the parameters describing this function are selected in such a way that z (t) represents a good approximation of the original signal sA (t):
    (4)
    Note that when the relationship from equation (4) applies, the self-distortion and intermodulation of the carriers in sA (t) is reduced. In the case of perfect equality in equation (4), the disadvantages introduced by the non-linear channel are completely eliminated.
    The output of the non-linear transformation block 263 is applied to a receive filter 264, which is typically matched to a send filter or to an equivalent filter obtained by concatenating the send filter and elements of the channel. The filter 264 filters the desired modulated signal 273 from sA (t) and produces the received data symbols.
    A decoding unit 265 further processes the received data symbols corresponding to the desired modulated signal. A person skilled in the art understands that suitable synchronization and equalization is required before decoding. For the sake of simplicity, however, this is not shown in the drawing.
    The non-linear transformation function in equation (3) is applied to the total signal sA (t), which contains all modulated signals that belong to the desired transponder. The receiver 260 is only interested in receiving the data from a single of these modulated signals. Prior art receivers that do not use the method disclosed in this invention are typically not familiar with the concept of desired transponder. To apply the present invention, the bandwidth and center frequency of the transponder of interest must be known to the receiver so that the selective filtering and non-linear transformation function can be applied. However, unlike other (multi-carrier) post-distortion compensation techniques, this invention does not necessarily require demodulation and decoding of modulated signals other than the modulated signal of interest.
    In one embodiment, the non-linear transformation function gm -) PA is a complex-value function that can be written as the product of two functions that operate on the amplitude and phase of the complex-value input signal
    (5) wherein | y (t) | represents the magnitude of y (t) and hNL [.; p '^] a non-linear function that operates on a real-value input. exp (.) is the exponential function and j is the imaginary unit (satisfying j2 = –1). i9 (y (t)) represents the argument (also called phase) of y (t). kNL [. ; p "A is a non-linear function that works on a realistic input. The functions άΝΙ [· ', ρ! Α] and kNL [.; p" can be described by means of a finite set of parameters. The parameters are used to configure the non-linear transformation (e.g., via a polynomial or non-polynomial function, or via a look-up table).
    A preferred way to split the non-linear transformation function Ρνι [·> Ρα into a product of a function that affects the amplitude and a function that works at the angle of the complex-worthy input signal is the following. The non-linear function hNL [. ; p'A] is written as
    (6) where p'A = [1, P2, P3] represents the parameter set describing the hNL [.; P'A] function. Similarly, the non-linear function kNL [. ; p "A] be written as
    (7) wherein p "A = [4, p5, p6] represents the parameter set describing the function kNL [.; P" A]. The rationale behind the models described in equations (6) and (7) is that they are good approximations of the inverse of certain amplifier models (described by / ^ - ^ (.)). Consequently, with an appropriate selection of the parameters, it is possible to reduce the self-distortion and intermodulation by satisfying the relationship described in equation (4).
    Alternatively, the non-linear and non-polynomial function hNL [.; P'A can be written as
    (8)
    Similarly, the non-linear and non-polynomial function kNL [.; p''A] be written as
    (9)
    The exponents p2, p4, pe, ps are not necessarily complete and may have real values. These functions are suitable for compensating for certain amplifier models. Other polynomial or non-polynomial models are suitable to compensate for yet other amplifier models.
    In an advantageous embodiment, the parameters of the non-linear transformation function 9NL [y (.t); pA ~] are selected in an adaptive manner based on performance metrics determined by the receiver on one or more modulated signals.
    In one embodiment, a performance metric of the decoder is used to measure the signal quality of the received desired modulated signal. In the case of a linear block code with an iterative decoding strategy, a good metric is the number of decoding itations required to achieve error-free reception. Another appropriate metric is the number of unsatisfactory parity check nodes in a given decoding iteration (e.g., the last decoding iteration) or a weighted sum of the number of unsatisfactory parity check nodes in different iteration phases in the decoding process. It can be seen that other similar decoding metrics can be designed that give an indication of the received signal quality.
    In another embodiment, the signal quality of the received modulated signal in which one is interested is measured with a noise and distortion level meter as known in the art. This noise and distortion level estimator estimates the thermal noise together with the negative impact caused by the self-distortion and intermodulation, and thus provides a signal-to-noise-plus distortion metric.
    The performance metrics described above drive a feedback loop, which is used to tune the parameters of the non-linear transformation function. The parameters are selected to reduce the distortion level measured by one of the performance metrics mentioned above. This can be done in a calibration phase or continuously via an adaptive parameter follow-up. When the non-linear transformation function approaches the inverse of the non-linearity on the satellite, equation (4) will be satisfied, resulting in a reduced self-distortion and intermodulation level, as can be seen in the spectrum 272.
    For certain scenarios, the distortion level is minimized if the non-linear transformation is selected using one of the methods outlined above. In an alternative embodiment, the parameters can also be selected such that the non-linear transformation is substantially equal to the inverse of the known non-linear channel. In this case, this channel is known to the receiver as perfect or approximate.
    In other scenarios, the distortion level is minimized if the non-linear transformation function is not equal to the inverse of the non-linear channel. This is the case, for example, with quasi-linear channels. Also note that the inverse of the non-linear channel does not always exist or is not always uniquely defined. This can occur, for example, with channels for which the output level does not increase monotonously with the input level. In this scenario, it is advisable to tune the parameters of the non-linear transformation function through an adaptive feedback loop.
    FIG. 3 illustrates another embodiment of the present invention. In this embodiment, the receiver has more than a desired modulated signal, ie more than one modulated signal is demodulated and decoded by a receiver 360. This receiver comprises a selective filter 362, a non-linear transformation block 363 and a plurality of matched filters 371, 372 and 373 and decoders 375, 376 and 377. In this scenario, the non-linear transformation parameters are tuned by combining the performance metrics of one or more receiver chains. A good combination comprises an optimization of the average of the performance metrics measured on the various modulated signals received. It is also possible to use the performance metric of the modulated signal that provides the best performance. It is clear that other combinations of the available performance metrics can be used.
    In another embodiment, the third-order intermodulation product of two or more received modulated signals (at the output of 371, 372 or 373) is calculated and correlated with the total signal 382. The correlation level is used as a performance metric for the intermodulation level present in signal 382.
    Although the invention has been illustrated and described in detail in the drawings and foregoing description, such illustrations and descriptions are to be considered as illustrative or exemplary and not restrictive. The foregoing description explains certain embodiments of the invention in detail. It should be noted, however, that no matter how detailed the foregoing is contained in the text, the invention can be made in many ways. The invention is not limited to the disclosed embodiments.
    Other variations on the disclosed embodiments may be understood and performed by persons skilled in the art and by practicing the claimed invention, through a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps and the indefinite article "a" does not exclude a plural. A single processor or other unit can perform the functions of different items in the claims. The mere fact that certain measures are listed in mutually different dependent claims does not mean that a combination of those measures cannot be used to benefit. A computer program can be stored / distributed on a suitable medium, such as an optical storage medium or semiconductor medium supplied with or as part of other hardware, but can also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. Any references in the claims should not be construed as limiting the scope.
    权利要求:
    Claims (16)
    [1]
    Conclusions
    A method of compensating distortion in a receiver of a communication system, the method comprising: - receiving a signal comprising a plurality of transponder signals each containing a plurality of modulated signals, - applying said received signal to an adjustable spectral filter, wherein said spectral filter is configurable to select a desired transponder signal, - performing a non-linear transformation on said selected desired transponder signal, said non-linear transformation being represented by a set of parameter values based on one or more performance metrics, - applying the non-linearly transformed selected desired transponder signal to at least one receive filter, said at least one receive filter set to select at least one desired modulated signal, said one or more performance metrics being determined to be at least one n modulated signal of said plurality of modulated signals contained in said desired transponder signal.
    [2]
    The method of compensating distortion according to claim 1, wherein said non-linear transformation is given as a product of a first function that operates on the amplitude of said selected desired transponder signal and a second function that operates on the phase of said selected desired transponder signal .
    [3]
    The method of compensating distortion according to claim 1, wherein said first function that acts on the amplitude and said second function that acts on the phase are polynomial functions.
    [4]
    The method of compensating distortion according to any of claims 1 to 3, comprising a step of performing a decoding operation on said selected at least one desired modulated signal.
    [5]
    The method of compensating distortion according to claim 4, wherein said set of parameter values representing said non-linear transformation is determined by a performance metric supplied by an error-correcting decoder.
    [6]
    The method of compensating distortion according to claim 5, wherein in said performance metric supplied by said error-correcting decoder, the number of iterations needed to achieve error-free decoding is minimized.
    [7]
    The method of compensating distortion according to claim 5, wherein in said performance metric supplied by said error-correcting decoder a weighted sum of the number of unsatisfactory parity check nodes in different iterations in the decoding process is minimized.
    [8]
    The method of compensating distortion according to any of the preceding claims, wherein the signal-to-noise-plus distortion ratio of said received signal is used as a performance metric.
    [9]
    The method of compensating distortion according to any of the preceding claims, wherein said set of parameter values is selected from a plurality of predefined sets of parameter values.
    [10]
    The method of compensating for distortion according to any of the preceding claims, wherein said adjustable spectral filter is configured by taking into account at least the central frequency and the bandwidth of said desired transponder signal.
    [11]
    A method of compensating distortion according to any of the preceding claims, wherein said at least one desired modulated signal on which the one or more performance metrics are determined at least partially overlaps with one or more other known modulated signals from the plurality of modulated signals of the selected desired transponder signal, and wherein a version of said one or more other known modulated signals is subtracted from said at least one desired modulated signal and the result of that subtraction is used in said one or more performance metrics.
    [12]
    A receiver for a communication system adapted to receive a signal comprising a plurality of transponder signals each containing a plurality of modulated signals including the receiver device - an adjustable spectral filter (262) configurable for selecting a desired transponder signal (270 - means (263) for performing a non-linear transformation on said selected desired transponder signal, said non-linear transformation being represented by a set of parameter values, - at least one receive filter (264) configurable to at least one desired select modulated signal from the non-linearly transformed selected desired transponder signal, - means for measuring the performance for determining a plurality of performance metrics on at least one modulated signal of said plurality of modulated signals contained in said desired transponder signal, o to obtain said set of parameter values.
    [13]
    The receiver device of claim 12, comprising a decoder (265) for decoding said selected at least one desired modulated signal.
    [14]
    A receiver device according to claim 12 or 13, comprising a down-conversion mixer adapted to supply an input signal to said adjustable spectral filter.
    [15]
    A receiver device according to any of claims 12 to 14, wherein said means for measuring performance is arranged to receive from the at least one desired modulated signal on which the one or more performance metrics are determined, a received version of one or more other known modulated signals to subtract from the plurality of modulated signals from the selected desired transponder signal and to use the result of that subtraction in the one or more performance metrics.
    [16]
    A satellite communication system comprising a receiver device according to any of claims 12 to 15.
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    申请号 | 申请日 | 专利标题
    NL2013087|2014-06-27|
    NL2013087A|NL2013087B1|2014-06-27|2014-06-27|Receiver Device and Method for Non-Linear Channel Compensation.|
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