US9270498B2 - System and method for amplifying a signal - Google Patents

System and method for amplifying a signal Download PDF

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US9270498B2
US9270498B2 US14/516,358 US201414516358A US9270498B2 US 9270498 B2 US9270498 B2 US 9270498B2 US 201414516358 A US201414516358 A US 201414516358A US 9270498 B2 US9270498 B2 US 9270498B2
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signal
gain
amplification
amplified
determination
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US20150110222A1 (en
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Jessica BOUVIER
Bruno Costa
Pierre Guern
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Thales SA
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Thales SA
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/028—Arrangements specific to the transmitter end
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
    • H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
    • H03F1/3247—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits using feedback acting on predistortion circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers
    • H03G3/3042—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers
    • H03G3/3047—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers for intermittent signals, e.g. burst signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0002—Modulated-carrier systems analog front ends; means for connecting modulators, demodulators or transceivers to a transmission line
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2201/00—Indexing scheme relating to details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements covered by H03F1/00
    • H03F2201/32—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion
    • H03F2201/3233—Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion

Definitions

  • the present invention concerns an amplification system having a servo-control device for the transmission power.
  • These systems can be used in civil or military radio communications equipment, for example, using waveforms that have a non-constant envelope and that can be single-carrier or multi-carrier.
  • this allowance is likewise known by the expression Output Back-Off.
  • the aim of this allowance is to remain within a region of linear operation of the power amplifier.
  • the presence of this allowance is inconsistent with the quest for the best possible yield.
  • the reason is that in order to improve the yield of the power transistors used in radio communications equipment, they are often focussed into class AB.
  • One of the special features of the AB class is that its yield increases when the transmitted power increases.
  • Another special feature of this class of operation is that its optimum operating point in terms of linearity is dependent on a certain number of operating variables such as the transmission frequency used or the temperature.
  • FIG. 1 Systems operating in closed-looped mode are also known from the prior art. These systems are shown in FIG. 1 , are connected to a modem 101 and have an amplification device 102 exhibiting a variable amplification gain. They also have a device 103 for determining a difference between the amplified signal and a copy of the signal to be amplified. Finally, these systems have a device 104 for determining the amplification gain on the basis of the difference.
  • the device 103 for determining a difference is known to carry out filtering of the amplified signal or of the signal representing the difference so as to remove the contribution of the variations in the modulation envelope on the gain control signal.
  • the automatic gain control is then severely slowed down in relation to the spread band for the frequencies of the modulation used.
  • the loop band must be one hundred times lower than the bandwidth of the modulation in order to completely eliminate envelope variations.
  • the device 103 for determining a difference is known to make direct use of the samples of the signal to be amplified as a setpoint. It this case, the gain control loop can be rapid and it is possible to eliminate the envelope variations of the gain control signal.
  • U.S. Pat. No. 7,353,006 B2 Analog Devices, 2004
  • U.S. Pat. No. 7,773,691 B2 RF Micro devices, 2005
  • the device 104 for determining the amplification gain can take account of the perturbations of the signal that are generated by the amplification device 102 .
  • this taking-account of the perturbations is static, that is to say that it does not use an estimator to update the model of the perturbations of the amplification device.
  • these systems can cause instability if the gain and the delay of the radio channel differ from the expected values.
  • the present invention therefore aims to overcome these problems by proposing an amplification system that is connected to a modem delivering a signal to be amplified.
  • This system has at least one amplification device in which an amplification gain is variable. It also has at least one first determination device for determination of a first difference between an amplified signal and the signal to be amplified. Moreover, this system has at least one second determination device for determination of the variable gain. Moreover, the second determination device is capable of the determination of said variable gain on the basis of said signal to be amplified, said amplified signal and said first difference.
  • This second device has at least one third determination device for determination of a model of the perturbation of the first difference by said amplification device on the basis of said signal to be amplified and said amplified signal.
  • This second device also has at least one fourth determination device for determination of perturbations of the first difference, which are caused by said amplification device, on the basis of said model and said signal to be amplified.
  • the second device also has at least one fifth determination device for determination of a second difference between said first difference and said perturbations and a controller that is capable of determining said variable gain on the basis of said second difference.
  • the amplification system has at least one extraction device, for extraction of the amplified signal to the first determination device.
  • This extraction device comprises a directional coupler that is used to recover the signal transmitted on a wire connecting the amplification device and an antenna. It also has at least one device for regulating the gain of the recovered signal. It then has a mixer for mixing the signal that has had its gain regulated with a sinusoidal signal.
  • This coupler also has a plurality of filters for filtering the mixed signal, these filters comprising at least one fixed-bandwidth analogue filter that is used for anti-aliasing and/or anti-jamming and at least one switchable digital filter for the bandwidth that varies as a function of a bandwidth of said signal to be amplified and/or of a disparity between a frequency of said signal to be amplified and a frequency of said perturbations.
  • the first determination device is connected directly to the modem.
  • the model of the perturbations comprises a delay and a gain and the third determination device for determination of a model is capable of the determination of said model by means of a correlation between said signal to be amplified and said amplified signal.
  • the controller is a PID controller.
  • the second determination device has a conversion table relating a power of said signal to be transmitted to the amplification gain.
  • the present invention also proposes a method for using the amplification system having the following successive steps:
  • the method has a step of regulation of the amplification gain of the amplification device. This step of regulation of the amplification gain is carried out after the step of increase of the amplification gain. Moreover, this step of regulation is carried out on the basis of a setpoint.
  • the step of configuration is suited to configuring the amplification device so as to be able to transmit a maximum output power of Pout_max.
  • Pout_max by means of this calculation allows configuration of the gain to be applied to the setpoint signal (setpoint gain) so as to compare it with the signal received on the measurement path.
  • calibration tables for the measurement path and for the transmission path contain the values of the setpoint gain and the configuration on the variable-gain elements of the measurement path and of the transmission path corresponding a priori to the power Pout_max.
  • the step of increase of the amplification gain is implemented by means of a conversion table relating a power of said signal to be transmitted to said amplification gain when the power of said signal to be amplified is lower than a threshold; and by means of the controller when the power of said signal to be amplified is higher than said threshold.
  • the delay in the main loop which is caused by the filters of the amplification system that are necessary for co-site operation, is eliminated from the gain error (first difference) by virtue of the estimator of the model of perturbation of the signal by the amplification system.
  • Co-site operation is implemented when various radio systems are situated in a close geographical region.
  • This geographical region is defined by a circle having a radius in the order of ten or so meters.
  • the modelling of the signal as perturbed by the amplification system and the use of the modulated samples as a reference for the calculation of the first difference make it possible to significantly increase the bandwidth of the main loop and to make it independent of the bandwidth of the signal to be amplified.
  • the bandwidth of the loop can then be chosen solely in order to comply with the rise time required by the waveform (in the case of waveform regularly changing transmission frequency, also known by the expression FH waveform).
  • the loop bandwidth characterizes the behaviour of the system in closed-looped mode. It is calculated on the basis of the closed-looped transfer function of the system.
  • This transfer function in the case of this invention includes the contribution of all the filters of the transmission path and of the measurement path (when likened to their transfer function) and the transfer function of the controller.
  • A(p) is the transfer function of the transmission chain associated with the controller and B(p) is the function of the chain of the measurement path.
  • the closed loop transfer function (also known by the acronym CLTF) has the following value:
  • the estimator of the perturbation of the signal caused by the amplification device allows optimum and stable gain control to be obtained, which makes it possible to control gain continuously, including during phases containing useful data and for waveforms with a non-constant envelope.
  • the precision of the transmitted power depends on the precision of calibration of the transmission path.
  • the transmission path has a large number of non-linear elements (amplifiers, tuneable filters, etc.). Its gain is therefore greatly dependent on transmission power, temperature and frequency. It is therefore necessary to perform calibration over the entire range of operation that the radio station can cover.
  • the precision of the system of the invention is solely dependent on the precision of the calibration of the measurement path. Since the measurement path does not have any non-linear elements, it is easier and faster to calibrate than the transmission path.
  • the first determination device 103 connected directly to said modem 101 allows direct use of the samples from the modem to perform gain control.
  • the amplification system allows a precise power for the amplified signal, even in a harsh environment.
  • the harsh environment translates into two phenomena:
  • the use of a mixer associated with the anti-jamming device makes power servo control possible in a co-site situation (This situation is realized when various radio systems are situated in a close geographical region. This geographical region is defined by a circle having a radius in the order of ten or so meters).
  • a mixer which has a linear voltage response
  • a logarithmic detector facilitates servo control because it is no longer necessary to use conversion tables. These conversion tables allow an item of information of logarithmic type to be converted into an item of information of linear type.
  • FIG. 1 shows a system according to the prior art.
  • FIG. 2 shows the system using the method of the invention.
  • FIG. 3 shows the voltage-controlled variable attenuator.
  • FIGS. 4 . a to 4 . c show the model of perturbation of the signal by the amplification device.
  • FIG. 4 d shows the voltage-controlled variable attenuator.
  • FIG. 5 shows the system using a conversion table.
  • FIG. 6 shows the method for using the system.
  • FIG. 7 shows the various phases of use of an FH signal.
  • FIG. 8 shows a mode of implementation of the system.
  • FIG. 2 describes the system according to a first aspect of the invention.
  • the modem 101 is connected to the amplification system.
  • the amplification system has:
  • the second device 104 for determining the variable gain effects this determination on the basis of:
  • This second device has:
  • the system has an extraction device 301 for extraction of the amplified signal to the first device for determining a difference.
  • This extraction device 301 comprises:
  • the model of perturbations of the signal to be amplified which are caused by the amplification device and the extraction device 301 , has a pure delay and a gain.
  • the third device 201 uses a correlator of difference amplitude type that works in non-real time during the start of use of the automatic gain controller. In order to determine the value of this delay and of this gain, the third device uses the correlation function R(m) between the signal to be amplified X(n) and the amplified signal z(n). This correlation is expressed using the following relationship:
  • the value of mean_g is corrected by the value of the variable gain (the gain of the voltage-controlled variable attenuator denoted by the acronym GWA) to give an estimate of the static gain G_stat.
  • GWA the gain of the voltage-controlled variable attenuator
  • the determination device 202 for determination of the perturbation of the first difference adapts the operation of a Smith predictor to the case of a modulated signal which, in association with a pure delay of the radio channel, causes a perturbation of the error signal.
  • FIG. 4 . a shows a classic example of a looped system having a delay.
  • the transfer function C(p) corresponds to a controller.
  • the transfer function H(p)e ⁇ Tp corresponds to the rest of the loop.
  • it is likened to the set made up of the transmission path and the measurement path.
  • OLTF′ c ( p )* H ( p )
  • CLTF closed-looped transfer function
  • CLTF ′ OLTF ′ 1 + OLTF ′
  • CLTF ′ C ⁇ ( p ) * H ⁇ ( p ) 1 + C ⁇ ( p ) * H ⁇ ( p )
  • OLTF open-looped transfer function
  • CLTF closed-looped transfer function
  • FIG. 4 . b illustrates the new loop thus formed.
  • FIG. 4 . c shows this loop in the digital domain.
  • the secondary loop implements the transfer function: H ( z )(1 ⁇ z ⁇ k )
  • the main error signal E(z) is subtracted from the output signal of the Smith predictor S corr (z) to produce a corrected error E_corr(z).
  • E _cor( n ) Error( n ) ⁇ S corr( n )
  • the signal E_cor(z) is sent to the transfer function controller C(z).
  • the variable attenuator is modelled as a voltage-controlled variable gain or a system having two inputs and one output.
  • FIG. 4 . d shows the model of this attenuator.
  • the gain response GVVA of the voltage-controlled attenuator is modelled by a 2nd-order transfer function associated with a pure delay and with an offset. This transfer function is set up on the basis of measurements from a component targeted to implement the automatic gain control function.
  • the transfer function HVVA(p) is identified on the basis of measurement and takes the following form:
  • HVVA ⁇ ( p ) GVVA 0 ⁇ ( p )
  • V_cmd ⁇ ( p ) Katt * e - Tatt * p ( 1 + ⁇ ⁇ ⁇ a ⁇ ⁇ tt * p 2 ) + off_att
  • V_cmd(p) represents the control voltage of the attenuator.
  • GVVA 0 (p) represents the modelled gain of the attenuator.
  • Katt represents the gain of the attenuator.
  • e ⁇ Tatt*p represents the pure delay of the attenuator vis-à-vis its control voltage.
  • 1+ratt*p 2 represents the denominator of a 2nd-order low-pass function.
  • off_att represents the gain offset, thus when the control voltage is zero the gain is not zero. This offset allows the attenuation dynamics of the component to be modelled, which are limited.
  • the infinite impulse response filter representing HVVAt(z), thus obtained is, in a non-limiting embodiment, of 6th-order (convolution of a 2nd-order filter and of a 3rd-order filter for the delay).
  • the samples GVVA 0 (n) from the filter HVVA(z) are multiplied by a polynomial function.
  • the polynomial function is applied directly to the samples GVVA 0 (n) in order to obtain the gain GVVA(n) by virtue of the following formula:
  • FIG. 5 describes the system in which the second determination device 104 has a conversion table 501 that allows a power of said signal to be transmitted to be related to the amplification gain.
  • FIG. 6 describes a first embodiment of the method for implementing the system described in this invention. This method has the following steps:
  • step 603 of regulation of the gain is not realized explicitly.
  • the amplification system must therefore be capable of regulating the gain without degrading the useful data.
  • the operation of the amplification system is identical to FH operation with, moreover, transitions from step 604 of deactivation of the regulation to step 603 of regulation of the gain.
  • the time interval during which step 603 of regulation of the gain is carried out needs to be signalled to the gain control device so that it is able to adapt the model of perturbations. This interval must be compatible with the determination carried out by the determination device 201 for determination of the model.
  • the modem and the amplification system exchange a certain number of parameters that are representative of the waveform that needs to be amplified. These parameters can be exchanged at the moment at which the waveform is loaded or during the use of the waveform and include:
  • the bandwidth information allows addressing of the tables containing the parameters of the regulation loop, notably the coefficients of the P controller (integration constant, gain) and of the digital filters of the measurement path.
  • FIG. 8 shows a mode of implementation of the system of the invention.
  • the system comprises the following elements:

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Transmitters (AREA)
  • Control Of Amplification And Gain Control (AREA)
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FR1302416 2013-10-18
FR1302416A FR3012272B1 (fr) 2013-10-18 2013-10-18 Systeme et procede d'amplification d'un signal

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EP (1) EP2863541B1 (de)
ES (1) ES2683423T3 (de)
FR (1) FR3012272B1 (de)
IL (1) IL235114A (de)
MY (1) MY167984A (de)
PL (1) PL2863541T3 (de)
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Publication number Priority date Publication date Assignee Title
US6133789A (en) * 1997-12-10 2000-10-17 Nortel Networks Corporation Method and system for robustly linearizing a radio frequency power amplifier using vector feedback
US20020171484A1 (en) 2001-04-23 2002-11-21 Lars Sundstorm Automatic optimization of linearity for envelope feedback RF amplifier linearization
GB2394374A (en) 2002-10-17 2004-04-21 Roke Manor Research An IQ feedback predistortion loop comprising a power amplifier (PA) and a PA model
US6735420B2 (en) 2001-12-18 2004-05-11 Globespanvirata, Inc. Transmit power control for multiple rate wireless communications
US7023278B1 (en) 2004-09-21 2006-04-04 Rockwell Collins, Inc. Digital power amplifier level control
US7058369B1 (en) 2001-11-21 2006-06-06 Pmc-Sierra Inc. Constant gain digital predistortion controller for linearization of non-linear amplifiers
US7353006B2 (en) 2003-03-12 2008-04-01 Analog Devices, Inc. Closed loop power control of non-constant envelope waveforms using sample/hold
US7773691B2 (en) 2005-04-25 2010-08-10 Rf Micro Devices, Inc. Power control system for a continuous time mobile transmitter
US20100248658A1 (en) 2007-10-18 2010-09-30 Freescale Semiconductor, Inc. Method and system of adaptive predistortion of a wireless transmitter
US20120034887A1 (en) * 2010-08-03 2012-02-09 Crestcom, Inc. Transmitter Linearized Using Cartesian-Processed Look-Up Table and Method Therefor
US20130034188A1 (en) * 2006-04-04 2013-02-07 Apple Inc. Signal Transmitter Linearization
US8706062B1 (en) * 2008-12-19 2014-04-22 Scintera Networks, Inc. Self-adaptive power amplification

Patent Citations (12)

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Publication number Priority date Publication date Assignee Title
US6133789A (en) * 1997-12-10 2000-10-17 Nortel Networks Corporation Method and system for robustly linearizing a radio frequency power amplifier using vector feedback
US20020171484A1 (en) 2001-04-23 2002-11-21 Lars Sundstorm Automatic optimization of linearity for envelope feedback RF amplifier linearization
US7058369B1 (en) 2001-11-21 2006-06-06 Pmc-Sierra Inc. Constant gain digital predistortion controller for linearization of non-linear amplifiers
US6735420B2 (en) 2001-12-18 2004-05-11 Globespanvirata, Inc. Transmit power control for multiple rate wireless communications
GB2394374A (en) 2002-10-17 2004-04-21 Roke Manor Research An IQ feedback predistortion loop comprising a power amplifier (PA) and a PA model
US7353006B2 (en) 2003-03-12 2008-04-01 Analog Devices, Inc. Closed loop power control of non-constant envelope waveforms using sample/hold
US7023278B1 (en) 2004-09-21 2006-04-04 Rockwell Collins, Inc. Digital power amplifier level control
US7773691B2 (en) 2005-04-25 2010-08-10 Rf Micro Devices, Inc. Power control system for a continuous time mobile transmitter
US20130034188A1 (en) * 2006-04-04 2013-02-07 Apple Inc. Signal Transmitter Linearization
US20100248658A1 (en) 2007-10-18 2010-09-30 Freescale Semiconductor, Inc. Method and system of adaptive predistortion of a wireless transmitter
US8706062B1 (en) * 2008-12-19 2014-04-22 Scintera Networks, Inc. Self-adaptive power amplification
US20120034887A1 (en) * 2010-08-03 2012-02-09 Crestcom, Inc. Transmitter Linearized Using Cartesian-Processed Look-Up Table and Method Therefor

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IL235114A0 (en) 2015-01-29
MY167984A (en) 2018-10-09
EP2863541A1 (de) 2015-04-22
SG10201406747PA (en) 2015-05-28
FR3012272B1 (fr) 2017-05-26
FR3012272A1 (fr) 2015-04-24
US20150110222A1 (en) 2015-04-23
ES2683423T3 (es) 2018-09-26
PL2863541T3 (pl) 2018-11-30
EP2863541B1 (de) 2018-05-16
IL235114A (en) 2017-09-28

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