EP3245734A2

EP3245734A2 - System for monitoring the peak power for an rf power amplification and associated method of calculating peak value and of selecting supply voltage

Info

Publication number: EP3245734A2
Application number: EP16712943.6A
Authority: EP
Inventors: Emmanuel GATARD; Pierre LACHAUD
Original assignee: Wupatec
Current assignee: Wupatec
Priority date: 2015-01-15
Filing date: 2016-01-11
Publication date: 2017-11-22
Also published as: FR3031851B1; FR3031851A1; WO2016113493A3; WO2016113493A2; US20170373644A1; US10164575B2

Abstract

The subject of the invention is a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification (1) of said telecommunication signal to be transmitted, comprising a digital processing device (3), a digital-RF converter (4) and a DC-DC converter (5), the output of the DC-DC converter (5) being able to take a discrete voltage value from among N discrete voltage values, N being an integer number greater than or equal to 2, the digital processing device (3) comprising a processing pathway (6) comprising envelope monitoring control logic (7) able to create a continuous control signal for envelope monitoring. The processing pathway (6) furthermore comprises drive logic (8) for controlling the DC-DC converter (5) comprising a device for calculating peak value (9) and a device for selecting supply voltage (10).

Description

CRETE POWER MONITORING SYSTEM FOR RF POWER AMPLIFICATION AND METHOD OF CALCULATING THE CRETE VALUE AND POWER SUPPLY VOLTAGE SELECTION

The present invention relates to the field of radiofrequency (RF) power amplification, and in particular relates to a peak power monitoring system for RF power amplification and a method of peak value calculation and selection of power. associated supply voltage.

The constant increase in wireless communication rates necessitates the use of complex modulations with high spectral efficiency such as OFDM (Orthogonal Frequency Division Multiplexing), these modulations having significant peak factors (ratio of peak power). and the average power of the signal).

RF power amplifiers that are powered by a DC supply voltage provide maximum efficiency only when working on compression, i.e. at the peak power of the signal to be transmitted. However, most of the time, the amplifier provides a power well below its maximum power, close to the average power of the signal to be transmitted, the efficiency of the amplifier being in these conditions much lower than its maximum efficiency.

The envelope tracking technique (Envelope Tracking) is a power technique to improve the performance of RF power amplifiers, which replaces the continuous constant power supply of the amplifier with a continuous dynamic power supply. which follows the amplitude of the RF signal to be emitted. The technique Envelope tracking allows dynamically adjusting the supply voltage of the RF power amplifier so that it always works in compression and thus at its maximum efficiency, regardless of the power level of the envelope of the RF amplifier. RF signal, this technique allows for modern modulation formats to significantly improve the performance of RF power amplifiers while meeting the standards requirements in terms of linearity.

In the case of an RF power amplifier with envelope tracking, the supply voltage is by definition constantly readjusted to ensure that the amplifier is still operating at compression and thus at its maximum efficiency, whatever the desired power level on transmission.

The supply voltage of an envelope-tracking RF power amplifier is generated by a DC-DC converter (also known as polarization modulator) for generating a wide-band continuous control signal. The DC-DC converter generally comprises a DC-DC switching portion operating at low frequencies and a linear amplifying portion for tracking rapid changes in the envelope signal. However, the low efficiency linear amplification portion greatly degrades the overall efficiency of the DC-DC converter. In addition, the greater the bandwidth covered by the linear amplification part, the greater the overall efficiency is impacted by the low efficiency of the linear amplification part.

Another known technique commonly used to generate a continuous envelope tracking control signal relies solely on the use alone a DC / DC switching converter, which must be fast enough to meet the bandwidth requirements since it relies on a PWM type pulse width modulation signal ) or sigma-delta. In addition, the control signal of the DC-DC converter must have a resolution sufficient to generate a large number of voltage levels at the output of the converter and thus correctly reconstruct the original signal. However, the switching transistors used for this type of converter are mainly GaN and GaAs technology transistors which are able to switch very rapidly in the presence of a high power signal, and are generally made in integrated technology in order to achieve better yields and switching speeds, thus greatly increasing the manufacturing cost of this type of converter.

The very fast switching of high currents in the DC-DC converters thus leads to the use of expensive component technologies, in incompatibility with the power amplification market for telecommunications.

Another envelope tracking technique relies on the generation by a DC / DC converter of a multi-level envelope tracking signal which consists of the application of a polarization control signal. N-level power supply, the power control signal of the RF amplifier can take one of N possible discrete levels, which has the advantage of supporting large bandwidth while maintaining high performance without having use of a linear amplifier within the DC-DC converter. The problem of implementing the envelope tracking technique for high power applications lies in the ability to have high efficiency DC / DC converters with a large bandwidth. The difficulty lies in this DC-DC converter that must provide high power, have a very good performance, be extremely linear, generate little noise and especially support large modulation bands.

As the efficiency of the DC-DC converters decreases drastically as the bandwidth of the modulated signal increases, it appears difficult to use the envelope tracking technique for high power applications with modern telecommunications signals that can reach bandwidths. up to 100 MHz.

In conjunction with the envelope tracking technique, to reduce stress on the DC-DC converter, a band reduction technique can be used. The band reduction decreases the spectral occupancy of the supply signal while ensuring that the voltage of the reduced band supply signal is always greater than or equal to the original signal voltage so as not to over-compress the RF amplifier.

This band reduction of the supply signal necessarily induces a drop in efficiency of the power amplifier since the control signal no longer follows the envelope of the modulated signal at any moment.

Moreover, the addition of a band reduction algorithm requires a system of increased complexity to generate this type of control, in particular a point of view digital signal processing. A band reduction technique must also be coupled to a pre-distortion technique very specific to this mode of operation and therefore also complex to implement.

DC / DC converters for the envelope tracking technique must have bandwidths well in excess of the RF signal bandwidth. In view of the increasing increase in the bandwidths of modern telecommunications signals, it appears relatively complex to have DC / DC converters with good efficiency and low cost for high power applications, despite the use of new component technologies. like gallium nitride (GaN).

The existing band reduction techniques are complex to implement and do not allow to consider very broad modulation bands with a good overall system performance.

In addition, in the case of the discrete multi-level envelope tracking technique, the tape reduction principle is not applicable. Indeed, no reduction in the constraints in terms of speed and switching recurrences on the DC-DC converter appears.

The compromise between efficiency and bandwidth of the DC-DC converter is highly limiting for high power applications for the use of the envelope tracking technique. This results in an inability to use the envelope tracking technique for high bandwidth and high power applications. A first solution is to use DC-DC converters for multi-phase Boost (voltage booster) for the generation of a continuous type control signal, that is to say which contain several branches in parallel. These converters operate in pure commutation and in their very principle of operation make it possible to reduce the switching frequency for the same bandwidth and with a good efficiency. However, in order to reach high bandwidths, the switching frequencies remain very high and therefore this technique does not solve the yield-bandwidth problem. In addition, the frequency of the switching signal remains fixed for this type of converter and therefore, for low bandwidths, the efficiency of the converter will be sacrificed unnecessarily.

A second solution relies on band reduction techniques for envelope tracking that improve the efficiency-bandwidth trade-off without solving the problem for large modulation bands and gives the system increased complexity. a digital signal processing point of view, thus increasing the cost and power consumption of the system.

A last solution is to use either a control signal from a continuously variable modulator but from the selection of different power levels to generate a discrete type control signal. The multi-level envelope tracking technique does not provide as high RF amplifier yields as with a continuous drive signal but the converter losses are lower. However, this solution improves but does not allow not to solve the compromise bandwidth efficiency for large modulation bandwidths because the recurrences of switching remain significant in number.

US patent application US2014241462 A1 discloses a method and an envelope tracking system according to the prior art.

US patent application US2014118065 A1 describes a peak power monitoring system according to the prior art.

The present invention aims at solving the drawbacks of the prior art by proposing a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification of said telecommunication signal to be transmitted comprising logic. driving the DC-DC converter to greatly repel the yield-bandwidth limitation imposed by the DC-DC converters to make the envelope tracking technique applicable to high power applications with high bit rates, said system allowing generating a high power control signal adapted for applications with a very wide modulation band without necessarily requiring the use of converters, and therefore ultra-fast switching transistors capable of switching high currents in a very short time, said system permitting also to keep a very good on DC-DC converters even for wide modulation bands.

The control logic consists, among other things, in the analysis and detection of the maximum value of the continuous envelope monitoring control signal over an interval time, then applying, in place of a conventional envelope tracking control signal, a constant power supply voltage level on the RF power amplifier among a number of levels of voltage available, said voltage level being applied for a minimum duration equal to the determined time interval. The invention thus makes it possible to generate a slowly variable discrete-type power supply signal with respect to the signal modulation band, these characteristics making it possible to use a DC-DC converter at very low cost and strong performance even for wide modulation bands.

The invention also relates to a method of calculating peak value and supply voltage selection implemented by a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification of said signal. according to the present invention, and on an RF antenna equipped with such a system or implementing such a method.

The present invention therefore relates to a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification of said telecommunication signal to be transmitted, comprising an RF power amplifier having an RF input, an input of supply voltage and an RF output, a digital processing device, a digital-RF converter and a DC-DC converter, the digital processing device having an input adapted to receive the telecommunication signal to be transmitted as digital data, a first output connected to an input of the digital-RF converter and a second output connected to an input of the converter DC-DC, the digital-RF converter having an output connected to the RF input of the RF power amplifier, the DC-DC converter having an output connected to the power supply voltage input of the power amplifier RF, the output of the DC-DC converter can take a discrete voltage value among N discrete voltage values, N being an integer greater than or equal to 2, the digital processing device comprising, between its input and its first output an element of delay τ and between its input and its second output a processing chain comprising an envelope tracking control logic capable of creating a continuous envelope monitoring control signal from the digital data received at the input level of the digital processing device, characterized in that the processing chain further comprises, downstream of the envelope tracking control logic, a logic of flotation of the DC-DC converter comprising a peak value calculating device and a supply voltage selecting device, the peak value calculating device being adapted to temporally window the continuous envelope monitoring control signal and calculating the maximum value of the continuous envelope monitoring control signal on each time window, and the supply voltage selection device being able to control the DC-DC converter in order to impose on the output of the latter, among the N discrete voltage values, a discrete supply voltage value greater than or equal to the maximum value of the continuous envelope monitoring control signal over the entire corresponding time window, said discrete power supply voltage value being applied for a minimum period of time equal to the duration of the time window, the delay element τ being chosen such that the RF signal corresponding to digital data of the telecommunication signal to be transmitted at the RF input of the RF power amplifier is synchronized with the RF signal envelope-type supply voltage for these same digital data at the power supply voltage input of the RF power amplifier.

It should be noted that, in the system according to the invention, the N voltage levels are not necessarily uniformly distributed. The voltage selection device is thus able to select one of the N voltage levels which is greater than or equal to the maximum value of the continuous envelope monitoring control signal on a window, the N voltage levels being able to be uniformly distributed. or not.

The control logic of the processing chain is configured to implement an envelope tracking control law.

The proposed invention is to generate a discrete-type envelope tracking control signal having N slowly varying voltage levels through a peak voltage monitoring technique of the continuous envelope tracking control signal, the detection of the peak voltage of the continuous control signal being directly the image of the detection of the peak power input of the RF power amplifier.

The control signal of the RF amplifier can take only one voltage value among the N possible levels and these voltage levels do not adapt to the rapid changes of the envelope signal, the selected voltage level being applied for a minimum duration equal to the time window. The choice of the number N of levels and the duration of the time window depend mainly on the DC-DC converter capabilities, the symbol rate to be transmitted, and the modulation format (for example, QAM (quadrature amplitude modulation) or OFDM).

Thus, the generation of a discrete level signal that does not accurately track all variations of the modulation envelope makes it possible to support very large bandwidths while maintaining a high DC / DC converter efficiency, and to switching frequency within said converter, regardless of the architecture of the converter or the type of modulation. The discretization of a finite number of power levels makes it possible to avoid using a linear amplifier within the DC-DC converter, and the fact of not precisely following the amplitude of the envelope signal at each instant. allows to consider very large bandwidths without increasing the constraints on the DC-DC converter in terms of switching speed.

In addition, the control logic is simple to implement in a digital circuit, thus minimizing the number of logic circuits required in the digital circuits and their operating frequency, which results in a lower power consumption and a lower power consumption. lower circuit supply cost. The invention also allows the use of a DC-DC converter slower and therefore low manufacturing cost.

In addition, this control logic makes it possible to overcome threshold effects that can lead to very short pulses and thus to a dysfunction of the system at times. The delay τ makes it possible to synchronize the correct supply voltage of the RF amplifier according to the input data.

Finally, the fact that the discrete supply voltage value is greater than or equal to the maximum value of the continuous envelope monitoring control signal over the entire corresponding time window makes it possible to ensure that the amplifier of RF power, avoiding over-compression of the RF power amplifier.

According to a particular characteristic of the invention, the processing chain is a digital processing chain and N is less, preferably strictly less than, 2 ^{^} (number_bits_train_train), where number_trace_bits_train is the number of bits of the digital processing chain.

According to a particular characteristic of the invention, the continuous envelope monitoring control signal is sampled at a predetermined sampling frequency, the time window being defined by a predefined number of samples of the continuous control signal of tracking. sampled envelope, the frequency of the time window being a frequency sub-multiple of the sampling frequency.

Thus, the periodicity of the time window, which is defined by a predefined number of samples, makes it possible to limit the duration between two commutations in the DC-DC converter, the values of the different samples in a time window being compared in order to determine the maximum value of the samples in the time window. According to a particular characteristic of the invention, the number of voltage levels N is between 2 and 16.

The choice of N mainly depends on the capabilities of the DC-DC converter, the symbol rate to be transmitted and the modulation format.

It should be noted that the larger N is, the more complicated and expensive the system is to manufacture.

According to one particular characteristic of the invention, the phase difference between the clock of the time window and the sampling clock of the continuous envelope monitoring control signal is adjustable and is an integer number of samples of the control signal. continuous envelope tracking.

Thus, the position of the time window is adjustable relative to the sampling frequency of the signal to be transmitted in order to optimize the generated control signal to avoid the risk of a change of control voltage at the decision time. This results in practice by a phase shift between the sampling clock of the signal to be transmitted and the clock of the time window, said phase shift being defined by an integer number of samples.

According to a particular characteristic of the invention, the digital processing device is implemented in a programmable digital circuit, preferably a processor, a microprocessor, a microcontroller, a digital signal processing device (DSP), a specific integrated circuit an application (ASIC) or a programmable gate array (FPGA). Thus, the digital processing device can easily be implanted in a current programmable digital circuit.

According to a particular characteristic of the invention, the DC-DC converter is of the multi-input type of supply type Buck (voltage step) or Boost (voltage booster), or multi-phase type.

Thus, the DC-DC converter can generate a slow variation discrete-type control signal whose switching speed is not the predominant element, this converter having an excellent conversion efficiency.

In the case of a multi-input DC-DC converter, different supply voltages are connected to the multiple power inputs of the DC-DC converter, and one of the supply voltages is selected. by power transistor switches at the output of the DC-DC converter, the DC-DC converter having as many power inputs as output levels to be applied.

In the case of a DC-DC converter, one or two supply voltages are supplied to the DC-DC converter. For a Buck converter with two supply voltages, a low voltage and a high voltage limit the range of control voltages that the converter can provide for envelope tracking, thus minimizing switching losses, and significantly improving the efficiency of the converter. .

In the case of a Boost type DC / DC converter, only one supply voltage is supplied to the DC-DC converter. This voltage is necessarily lower than the low envelope tracking voltage.

In the case of a multi-phase DC / DC converter, which may be of the Buck or Boost type, one or two supply voltages are supplied to the DC-DC converter and the architecture of said converter makes it possible to distribute the current to provide on multiple phases in parallel and thus minimize the switching frequency of the switching transistors.

According to a particular characteristic of the invention, the digital-RF converter comprises a digital-analog converter associated with an RF mixer of the IQ modulator type, for example.

Thus, the digital-to-RF converter can first convert the digital data from the digital processing device to analog data, via the digital-to-analog converter, and then mix the analog data with an RF signal, via of the RF mixer.

According to a particular characteristic of the invention, the system further comprises a low-pass filter disposed between the output of the DC-DC converter and the supply voltage input of the RF power amplifier.

Thus, the low-pass filter makes it possible to perfectly control the transition characteristics of the discrete-type control signal from one discrete voltage level to another, and to reject, if necessary, the residual commutation ripple as much as possible.

According to a particular characteristic of the invention, the digital processing device comprises in addition pre-distortion logic that linearizes the gain of the RF power amplifier.

Thus, the distortions of the RF amplifier subjected to a discrete level envelope tracking signal can be linearized by the pre-distortion logic.

The present invention also relates to a method of calculating peak value and supply voltage selection implemented by a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification of said telecommunication signal to be transmitted as described above, characterized in that it comprises the following steps:

the time windowing of a continuous envelope tracking control signal;

calculating a maximum value of the continuous envelope monitoring control signal over each time window;

the selection, on each time window and among the N discrete voltage values, of a discrete supply voltage value greater than or equal to the maximum value of the continuous envelope monitoring control signal over the entire window corresponding temporal and

- The control of a DC-DC converter in order to impose at the output of the latter the discrete power supply voltage value selected on each time window.

Thus, said method makes it possible to limit the switching speed constraints on the DC-DC converter of the envelope-tracking RF power amplification system. It should be noted that in the case where the time window is defined by a predefined number of samples of the sampled envelope tracking continuous control signal, the calculated maximum value then corresponds to the value of the sample having the maximum value. among all the samples in the time window.

The present invention also relates to an RF transmission antenna equipped with a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification of said telecommunication signal to be transmitted according to the present invention or a method of calculating the peak value and selecting the supply voltage according to the invention is implemented.

To better illustrate the object of the present invention will be described below, by way of illustration and not limited to, a preferred embodiment, with reference to the accompanying drawings.

On these drawings:

- Figure 1 is a block diagram of a peak power monitoring system for RF power amplification according to the present invention;

- Figure 2 is a block diagram of a digital processing device of the peak power monitoring system for an RF power amplification according to the present invention;

FIG. 3 is a block diagram of a DC-DC converter of the peak power monitoring system for power amplification.

RF according to the present invention;

FIG. 4 is a flow diagram of a method for calculating peak value and selecting voltage power supply implemented by the peak power monitoring system for RF power amplification according to the present invention;

Figure 5 illustrates exemplary curves of different envelope tracking control signals in the peak power monitoring system for RF power amplification according to the present invention; and

FIG. 6 illustrates an exemplary curve of the performance of an RF power amplifier of the peak power monitoring system for the RF power amplification according to the present invention as a function of the ratio of the frequency of the window. time over the bandwidth of the modulation.

Referring to Figure 1, it can be seen that there is shown a peak power monitoring system for RF power amplification 1 according to the present invention.

The peak power monitoring system for RF power amplification 1 comprises an RF power amplifier 2 having an RF input 2a, a supply voltage input 2b and an RF output 2c, a digital processing device 3, an RF power amplifier 2a digital-RF converter 4 and a DC-DC converter 5.

The digital processing device 3 has an input 3a able to receive digital data I / Q representing a telecommunication signal to be transmitted by the RF channel via the RF amplifier 2, a first output 3b connected to an input of the digital-RF converter 4 and a second output 3c connected to an input of the DC-DC converter 5. The digital-RF converter 4 has an output connected to the RF input 2a of the RF power amplifier 2.

The DC-DC converter 5 has an output connected to the supply voltage input 2b of the RF power amplifier 2, the output of the DC-DC converter 5 being able to assume a discrete voltage value among N discrete voltage values. , N being an integer greater than or equal to 2, preferably between 2 and 16.

The RF power amplifier 2 comprises semi-conductor power elements such as semi-conductor power transistors (not shown in FIG. 1).

The digital-RF converter 4 comprises a digital-to-analog converter associated with an RF mixer (not shown in FIG. 1), the digital-analog converter converting the digital data coming from the digital processing device 3 into analog data, and the RF mixer. mixing said analog data with an RF signal.

The digital processing device 3 and the DC-DC converter 5 will be described in more detail below.

This system 1 thus makes it possible to apply a discreet level envelope tracking technique in order to improve the efficiency of the RF power amplifier 2, the power supply of the amplifier 2 being dynamic and depending on the amplitude of the signal RF to emit, the RF power amplifier 2 thus always operating in compression and therefore at its maximum output regardless of the power level of the RF signal envelope. The control signal of the RF power amplifier 2, at its supply voltage input 2b, can dynamically take one of the N possible discrete voltage values in order to follow the envelope of the RF signal to be transmitted.

Referring to Figure 2, it can be seen that there is shown the digital processing device 3 of the peak power monitoring system for RF power amplification 1 according to the present invention.

The digital processing device 3 comprises, between its input 3a and its first output 3b a delay element τ and between its input 3a and its second output 3c a processing chain 6.

The processing chain 6 comprises an envelope tracking control logic 7 able to create a continuous envelope tracking control signal from the digital data received at the input 3a of the digital processing device 3.

The control logic 7 is configured to implement an envelope tracking control law.

The control law is, for example, a non-linear function expressing itself in the form of a polynomial of order 3 to 7. The control law is described below, in the case of an order 3:

Vcommand = A + B * Venv + C * Venv ^{^} 2 + D * Venv ^{^} 3 where A, B, C and D are the constants of the control law and Venv is the envelope voltage of the signal to be transmitted, directly connected to the incoming power to the RF amplifier. The processing chain 6 further comprises a control logic 8 of the DC-DC converter 5 comprising a peak value calculating device 9 and a supply voltage selection device 10.

The peak value calculating device 9 is capable of temporally winding the continuous envelope monitoring control signal from the envelope tracking control logic 7, and calculating the maximum value of the continuous tracking control signal. envelope on each time window.

The supply voltage selection device 10 is able to control the DC-DC converter 5 in order to impose on the output of the latter an optimum discrete voltage value among the N discrete voltage values as a function of said maximum value on the time window calculated by the peak value calculating device 9, said optimum discrete voltage value being applied for a minimum duration equal to the duration of the time window, said optimum applied discrete voltage value being greater than or equal to the signal of Continuous envelope tracking control over the entire corresponding time window so as not to overcompress the RF power amplifier 2.

The delay element τ is chosen such that the RF signal corresponding to digital data of the telecommunication signal to be transmitted at the RF input 2a of the RF power amplifier 2 is synchronized with the supply voltage of the type RF signal envelope tracking for these same digital data at the power supply voltage input 2b of the RF power amplifier 2. It should be noted that the digital processing device 3 could further include a predistortion logic that linearizes the gain of the RF power amplifier 2 without departing from the scope of the present invention.

It should be noted that the entire digital processing device 3 is implemented in a programmable digital circuit, preferably a processor, a microprocessor, a microcontroller, a DSP, an ASIC or an FPGA.

The envelope tracking continuous control signal is sampled at a predetermined sampling frequency, the time window used by the peak value calculating device 9 being defined by a predefined number of samples of the continuous tracking control signal. sampled envelope, the frequency of the time window thus being a frequency sub-multiple of the sampling frequency.

It should be noted that an adjustable phase shift can be realized between the clock of the time window and the sampling clock of the continuous envelope tracking control signal, said phase difference being an integer number of samples of the signal of continuous sampled envelope tracking control. Thus, the adjustable position of the time window with respect to the sampling frequency of the signal to be transmitted makes it possible to optimize the generated control signal to avoid the risk of a change of control voltage at the decision time.

Referring to Figure 3, it can be seen that there is shown the DC-DC converter 5 of the peak power monitoring system for a RF power amplification 1 according to the present invention.

The DC-DC converter 5 in this preferred embodiment is of the multi-input power supply type.

It should be noted that the DC-DC converter 5 could also be of the Buck (voltage step-down) or Boost (voltage booster) type, or of the multi-phase type, without departing from the scope of the present invention.

The multi-input DC-DC converter 5 has N different supply voltages V _x to V _N , N corresponding to the desired number of possible discrete voltage values at the output of the DC-DC converter 5, and N switches with power transistors 11 to 11 _N each comprising first and second terminals, the first terminals of the N switches 11 to 11 _N being respectively connected to the N supply voltages, and the second terminals of the N switches 11 ia U _N being connected to a common node A.

The N switches 11 to 11 _N are dynamically controlled by the control processing device 3, so that only one of the N switches 11 to 11 _N is closed at a time in order to apply the associated supply voltage. at node A.

Thus, the DC-DC converter 5 can generate a slow varying discrete-type control signal whose switching speed is not the predominant element, this DC-DC converter 5 having an excellent conversion efficiency.

The DC-DC converter 5 further comprises a low-pass filter 12 disposed between the node A and the supply voltage input 2b of the RF power amplifier 2, the low-pass filter 12 making it possible to perfectly control the transition characteristics of the discrete-type control signal from one discrete voltage value to another and to reject, if necessary, the residual switching ripple as much as possible.

Although, for the sake of simplicity, a simple resonant circuit LC (inductor-capacitor) has been illustrated to represent the low-pass filter 12, the low-pass filter 12 could be a higher order higher order low-pass filter or equal to 2, without departing from the scope of the present invention.

It should be noted that the DC-DC converter 5 may not have a low-pass filter 12 at its output, without departing from the scope of the present invention.

Referring to Figure 4, it can be seen that there is shown a method of calculating peak value and supply voltage selection implemented by the peak power monitoring system for a RF power amplification 1 according to the present invention.

The method of calculating peak value and selecting power supply voltage comprises the following steps:

the temporal windowing of the envelope tracking continuous control signal from the envelope tracking control logic 7, the time window being defined by a predefined number of samples of the sampled envelope tracking continuous control signal ;

the calculation of a maximum value of the continuous envelope monitoring control signal on each window time, said calculation comprising, on each time window, the following steps:

the reception SI of the first sample of the time window, the maximum value being fixed at the value of the first sample;

the reception S2 of the following sample;

the determination S3 of whether or not the time window is completed, and if this is the case, the transition to step S6, and if this is not the case, the transition to step S4;

the determination S4 of whether the value of the current sample is greater than or not the maximum value, and if this is not the case the return to the step

S2, and if so the update S5 of the maximum value by the value of the current sample then return to step S2;

the selection S6, on each time window, of an optimum discrete voltage value among the N discrete voltage values as a function of said maximum value calculated over the time window, said optimum discrete voltage value being greater than or equal to the value envelope monitoring command signal over the entire corresponding time window; and

the control of the DC-DC converter 5 in order to impose on the output of the latter the optimum discrete voltage value selected on each time window.

With reference to Figure 5, it can be seen that curves are represented by way of example of different envelope tracking control signals in the peak power tracking system for RF power amplification 1 according to the present invention.

The dash curve represents an exemplary envelope tracking control signal from the envelope tracking control logic 7, which curve is represented as a supply voltage over time in order to facilitate the understanding of the reader.

The dashed line curve represents the control signal at the output of the peak value calculating device 9, said curve being represented as supply voltage over time in order to facilitate understanding of the reader.

The dashed line represents the control signal at the output of the DC-DC converter 5 applied to the RF power amplifier 2, said curve being represented as supply voltage over time.

In this example, the peak value calculation method and the supply voltage selection method is applied to the signal from the envelope tracking control logic 7 for a modulated signal of 1 MHz bandwidth. The time window used has an equivalent frequency of 2 MHz, ie 500 ns. In addition, the DC-DC converter used has four possible discrete output voltage values, viz. VI = 16V, V2 = 24V, V3 = 32V, and V4 = 40V.

The control signal at the output of the peak value calculating device 9 corresponds to the peak power of the continuous envelope tracking control signal after windowing every 500 ns. The control signal applied to the RF power amplifier 2, denoted V _out hereinafter tie, is created from the control signal at the output of peak value calculation device 9, denoted X (n) below according to the following algorithm:

if X (n) <VI, V _output = VI;

if VI <X (n) <V2, V _output = V2;

if V2 <X (n) <V3, V _output = V3; and

if V3 <X (n), V _output = V4.

Thus, V _out i _e is constantly greater than or equal to the continuous control signal envelope tracking to ensure the proper operation of the RF power amplifier 2, the duration of applying a voltage level being at least equal to the time window of 500 ns. In addition, this example shows that the present invention makes it possible to minimize the switching frequency within the DC-DC converter 5, thereby obtaining a high DC-DC converter efficiency for wide modulation bands.

Referring to Figure 6, it can be seen that there is shown as an example of the performance of an RF power amplifier 2 of the peak power monitoring system for power amplification. RF 1 according to the present invention as a function of the ratio of the frequency of the time window on the bandwidth of the modulation.

In this example, a 16QAM type modulation is applied to an RF power amplifier 2. The measured efficiency for a DC supply voltage is compared to the yields obtained for different time window widths for the detection of the peak control voltage. The frequency of the time window varies by 0.5 times the bandwidth (or symbols) of the modulated signal at 10 times the bandwidth of the modulated signal. In addition, in this example, four discrete power supply voltage levels are used to control the RF power amplifier 2.

The efficiency of the amplifier for the y-intercept corresponds to the yield obtained with a fixed supply voltage, namely about 38%.

The output of the amplifier obtained with a continuous envelope tracking signal is close to 60%.

Figure 6 shows that a time window of twice the bandwidth of the signal to be transmitted makes it possible, with four levels of supply voltage, to obtain an amplifier output close to the maximum efficiency while guaranteeing a continuous converter output. - Continuous 5 much higher than those of DC-DC converters using continuous or multi-level envelope tracking techniques. In addition, the DC-DC converter 5 does not need to be as fast in terms of switching speed and is therefore much simpler to implement.

The invention also relates to an RF transmit antenna equipped with the peak power monitoring system for an RF power amplification 1 according to the present invention or implementing a method for calculating peak value and selecting voltage from the supply according to the present invention.

The present invention may for example find application in base stations for mobile telephony, in radars, in electronic warfare devices, in mobile telephones or in any other wireless telecommunication equipment.

Claims

1 - System for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification (1) of said telecommunication signal to be transmitted, comprising:

an RF power amplifier (2) having an RF input (2a), a supply voltage input (2b) and an RF output (2c),

a digital processing device (3),

- a digital-RF converter (4) and

a continuous-DC converter (5),

the digital processing device (3) having an input (3a) adapted to receive the telecommunication signal to be transmitted as digital data, a first output (3b) connected to an input of the digital-RF converter (4) and a second output (3c) connected to an input of the DC-DC converter (5), the digital-RF converter (4) having an output connected to the RF input (2a) of the RF power amplifier (2), the converter DC-DC (5) having an output connected to the supply voltage input (2b) of the RF power amplifier (2), the output of the DC-DC converter (5) being able to assume a discrete voltage value among N discrete voltage values, N being an integer greater than or equal to 2, the digital processing device (3) comprising, between its input (3a) and its first output (3b) a delay element τ and between its input (3a) and its second output (3c) a processing chain t (6) comprising envelope tracking control logic (7) adapted to create a continuous envelope tracking control signal from the digital data received at the input (3a) of the processing device digital signal (3), characterized in that the processing chain (6) further comprises, downstream of the envelope tracking control logic (7), a control logic (8) of the DC-DC converter ( 5) comprising a peak value calculating device (9) and a supply voltage selection device (10), the peak value calculating device (9) being able to temporally wind the continuous control signal. envelope monitoring and calculating the maximum value of the continuous envelope monitoring control signal on each time window, and the supply voltage selection device (10) being adapted to control the DC-DC converter (5). ) to impose at the output of the latter, among the N discrete voltage values, a discrete supply voltage value greater than or equal to the maximum value of the continuous envelope monitoring control signal over the entire corrected time window the said discrete supply voltage value being applied for a minimum duration equal to the duration of the time window, the delay element τ being chosen such that the RF signal corresponding to digital data of the telecommunication signal to be transmitted at RF input (2a) input level of the RF power amplifier (2) is synchronized with the RF signal envelope tracking supply voltage for these same digital data at the voltage input of the RF power amplifier. power supply (2b) of the RF power amplifier (2).

2 - System (1) according to claim 1, characterized in that the processing chain (6) is a digital processing chain and in that N is lower, preferably strictly less than 2 ^ (number of bits in the chain treatment), where bit_bits_track_string is the number of bits in the digital processing chain (6).

3 - System (1) according to claim 1 or claim 2, characterized in that the envelope tracking continuous control signal is sampled at a predetermined sampling frequency, the time window being defined by a predefined number of samples of the sampled envelope tracking continuous control signal, the frequency of the time window being a sub-multiple frequency of the sampling frequency.

4 - System (1) according to one of claims 1 to 3, characterized in that the number of voltage levels N is between 2 and 16.

5 - System (1) according to one of claims 3 and 4, characterized in that the phase difference between the clock of the time window and the sampling clock of the continuous envelope tracking control signal is adjustable and is an integer number of samples of the continuous envelope tracking control signal.

6 - System (1) according to one of claims 1 to 5, characterized in that the digital processing device (3) is implemented in a programmable digital circuit, preferably a processor, a microprocessor, a microcontroller, a digital signal processing device (DSP), an application specific integrated circuit (ASIC) or a programmable gate array (FPGA).

7 - System (1) according to one of claims 1 to 6, characterized in that the DC-DC converter (5) is of the multi-input type of supply, of Buck type (voltage buckener) or Boost (voltage booster), or multi-phase type.

8 - System (1) according to one of claims 1 to 7, characterized in that the digital-RF converter (4) comprises a digital-analog converter associated with an RF mixer.

9 - System (1) according to one of claims 1 to 8, characterized in that the system (1) further comprises a low-pass filter (12) disposed between the output of the DC-DC converter (5) and the supply voltage input (2b) of the RF power amplifier (2).

10 - System (1) according to one of claims 1 to 9, characterized in that the digital processing device (3) further comprises a pre-distortion logic which linearizes the gain of the RF power amplifier ( 2).

11 - Method for calculating peak value and supply voltage selection implemented by a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification (1) of said telecommunication signal to be transmitted according to one of claims 1 to 10, characterized in that it comprises the following steps:

the time windowing of a continuous envelope tracking control signal;

calculating (S1-S5) a maximum value of the continuous envelope monitoring control signal over each time window;

the selection (S6), on each time window and among the N discrete voltage values, of a discrete supply voltage value greater than or equal to the maximum value of the continuous control signal of envelope tracking over the entire corresponding time window; and

- Controlling a DC-DC converter (5) in order to impose at the output of the latter the discrete power supply voltage value selected on each time window.

12 - An RF emission antenna equipped with a system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification (1) of said telecommunication signal to be transmitted according to one of Claims 1 to 10. or implementing a method of calculating peak value and supply voltage selection according to claim 11.