Method for adapting an impedance of an impedance-matching network in a radiofrequency application chain

Abstract

The invention relates to an impedance-matching method (P) for matching a load (5) located at the end of a radiofrequency application chain by way of an impedance-matching network (4) having two degrees of freedom placed upstream of the load. The method is in particular implemented by way of a radiofrequency discriminator (1) positioned upstream of the impedance-matching network and at the output of a radiofrequency generator (2) generating an electromagnetic wave. The method is noteworthy in that the radiofrequency discriminator remains positioned at the same position, that is to say a fixed position (p0), and carries out two impedance measurements (Z1, Z2) on the load at two distinct distances of interest (d1, d2) such that these make it possible to decouple the two degrees of freedom of the impedance-matching network purely digitally, so as then to be able to control them independently of one other and carry out the impedance matching.

Description

[0001] DESCRIPTION

[0002] TITLE: Method for adapting an impedance of an impedance matching network in a radiofrequency application chain

[0003] [Technical field]

[0004] The invention relates to a method for adapting the impedance of an impedance matching network in a radiofrequency application chain.

[0005] It relates more particularly to a method for adapting the impedance of an impedance matching network as a function of the impedance of a load placed downstream of the radiofrequency application chain, so that the impedance of the impedance matching network associated with the load is adapted to the output impedance of the source of the chain.

[0006] The invention finds a preferred, and non-limiting, application in the field of radiofrequency electronics for any radiofrequency application chain requiring the use of an impedance matching network to adapt an input impedance of a load whose value is too far from that of the output impedance of the source.

[0007] [State of the art]

[0008] As is known, in the field of radiofrequency electronics, it is customary, for a radiofrequency application chain comprising at least one radiofrequency generator (or source) transmitting a radiofrequency signal to a receiver system (or load) downstream of the chain, for example through a transmission line (such as a coaxial cable) connecting the source to the load if they are a certain distance apart, to adapt their respective impedances, that is to say that the output impedance of the source and the input impedance of the load are conjugated, and the impedance of the transmission line is equal to the input impedance of the load. More precisely, impedance adaptation consists of adapting the impedance of a system to that of the closest system(s) located downstream and / or upstream of it.

[0009] A radiofrequency application chain for which all impedances are adapted allows optimized signal transmission for maximum electrical power transfer between the source and the load. Otherwise, if at least one of the elements / systems downstream of the source does not have an impedance adapted to the rest of the other elements, it does not absorb the entire signal and reflects a part of it propagating in the direction of the source. Signal reflections on the chain then prevent part of the energy from being transmitted in the chain, thus attenuating the signal and causing an unnecessary surge on the application chain.

[0010] The impedances of the chain elements are adapted to a value of 50 Ohms.

[0011] However, the impedances of the elements of a chain can be defined by: a real / purely resistive part (e.g., a resistor), an imaginary / purely reactive part (an inductance, a capacitance), or both. Moreover, two impedances of the same nature can have resistance and / or reactance values ​​that are far from each other.

[0012] This is why, in the case where two successive systems in the radiofrequency chain have distant impedances, a so-called impedance matching network can be inserted between these two systems, the function of which is to carry out an impedance transformation between the two systems. More precisely, the impedance matching network is itself characterized by an impedance whose value is such that, when the impedance matching network is associated with one of the two systems, the impedance formed by this association is adapted to the second system.

[0013] For example, in the case of a chain comprising a source and a load for which the output impedance of the source would be very far away and / or of a different nature from that of the load input impedance, the impedance of the matching network is adjusted such that when it is associated with the load, the impedance formed by their association is equal to the conjugate impedance of the output impedance of the source.

[0014] Impedance matching networks are widely used by associating passive components (resistance, capacitance, inductance) in a topology (T, L, etc.) depending on the characteristics of the radiofrequency application chain. Impedance matching networks are also characterized by degrees of freedom corresponding to the number of discrete or distributed variable components they contain, which allow their impedance to be modified.

[0015] For example, a matching network consisting of two passive components, one of which has a fixed imposed value, has a single degree of freedom, insofar as the fixed value of said component conditions the value that the second component can take in order to adapt the impedance of a system to a given impedance value. A matching network consisting of two passive components but for which the value of each of the components can be modified independently of that of the other has two degrees of freedom. Also, in the case where the impedance matching network includes a transmission line, the length of said transmission line constitutes a degree of freedom.

[0016] In order to determine the values ​​that the components of the impedance matching network must take to achieve the impedance transformation of a given system, a radiofrequency discriminator can be used. This is a measuring device which, positioned at a given point in the radiofrequency application chain, is designed to measure an impedance or a reflection coefficient (from which the impedance can be mathematically deduced) of the entire part of the chain located downstream of this point.

[0017] When a two-degree-of-freedom impedance matching network is used, a known method of impedance matching of a radiofrequency application chain is to use an analog radiofrequency discriminator and position it in a particular position on the transmission line upstream of the load, such that in this said particular position, the measurements made by the discriminator are decoupled from the two degrees of freedom of the network; that is to say that each of the two measurements makes it possible to adjust the value of one degree of freedom independently of the other, the radiofrequency application chain being adapted once the two degrees of freedom are adjusted adequately.

[0018] This approach has two drawbacks. First, since the particular position is a compromise established from two other positions, it is therefore not very precise, meaning that the adjustments of the two degrees of freedom from the measurements made there by the analog discriminator do not allow for perfect impedance matching of the radiofrequency application chain. Second, the use of an analog radiofrequency discriminator requires having to move it manually to identify the two positions of interest and then the particular position. Knowing for example that the identification of the first position and the second position consists of placing the discriminator at any point on the transmission line, then checking at this point whether the conditions allowing the identification of one or the other of the two positions of interest are met or not, the approach can be very time-consuming depending on the length of the transmission line.

[0019] [Summary of the invention]

[0020] The invention proposes to solve the problems posed by means of an impedance matching method for matching an impedance of an impedance matching network which is inexpensive in terms of time; and ergonomic in being easy to implement in terms of installation, handling of equipment, etc. Thus, the invention relates to an impedance matching method for matching the impedance of a radiofrequency application chain (which may have a chain length) and comprising at least:

[0021] - a radiofrequency generator generating an electromagnetic wave and having a reference impedance defined at least by an imaginary reference part, and a reference module,

[0022] - a transmission line which is positioned (along the chain length) at the output of the radiofrequency generator and which has a characteristic line impedance adapted to the reference impedance,

[0023] - a functional block positioned (along the chain length) at the output of the transmission line and which comprises an impedance matching network and a load positioned at the output of the impedance matching network, in which the impedance matching network has two degrees of freedom by comprising a first variable component and a second variable component,

[0024] - a radio frequency discriminator positioned at a fixed position (located along the chain length), distant from the functional block by a fixed discriminator distance, between the output of the radio frequency generator and the input of the transmission line, and

[0025] - a control unit connected on the one hand to the radiofrequency discriminator, and on the other hand to the two-degree-of-freedom impedance matching network which it controls by transmitting a control order to it; which impedance matching method firstly implements a determination phase which is automated and during which a modulus and a phase of a reflection coefficient at the fixed position are numerically determined, from at least one measurement carried out by the radiofrequency discriminator; then subsequently implements an identification phase comprising:

[0026] - a first identification step during which a first position of interest is digitally identified, distant from the functional block by a first distance of interest, such that at said first position of interest, a modulus of a first impedance, seen at the first position of interest, varies only as a function of a value of the first variable component around the reference impedance, said first impedance being calculated digitally from at least the modulus and the phase of the reflection coefficient at the fixed position, and

[0027] - a second identification step during which a second position of interest is digitally identified, distant from the functional block by a second distance of interest such that at said second position of interest, an imaginary part of a second impedance, seen at the second position of interest, varies only as a function of a value of the second variable component around the reference impedance, said second impedance being calculated digitally from at least the modulus and the phase of the reflection coefficient at the fixed position; and finally said adaptation method implements an adaptation phase which is automated and during which the value of the first variable component is physically adjusted so that the modulus of the first impedance is equal to the reference modulus, and the value of the second variable component is physically adjusted so that the imaginary part of the second impedance is equal to the reference imaginary part.

[0028] In other words, the proposed impedance matching method is advantageously based on the use of a radiofrequency discriminator physically positioned at a fixed position at the output of a radiofrequency generator of a radiofrequency application chain, in order to be able to determine the reflection coefficient and / or the impedance at the fixed position; and then calculate the reflection coefficient and / or the impedance at any point in the chain located upstream of the functional block constituted by the impedance matching network placed in series with the load located at the end of the chain, without it being necessary to physically move the radiofrequency discriminator from its fixed position.

[0029] With regard to the chain length mentioned above, this concept refers to a physical length of electrical connection between upstream equipment in a radiofrequency application chain and downstream equipment in said radiofrequency application chain.

[0030] In the context of the present method, the chain length refers to the physical length of electrical connection between the output of the radio frequency generator and the input of the functional block. This chain length may include:

[0031] - a length of a connecting cable used to physically and electrically connect the output of the radiofrequency generator to the input of the radiofrequency discriminator;

[0032] - a dimension of the radiofrequency discriminator given in the length direction;

[0033] - the length of the transmission line.

[0034] Optionally, the chain length may also include a length of another connecting cable used to physically and electrically connect the output of the radio frequency discriminator with the input of the transmission line, in the case where the output of the radio frequency discriminator is not connected directly to the input of the transmission line. Metrically, the chain length is equal to the sum of these different lengths.

[0035] The term fixed position refers to a physical position of the radio frequency discriminator between the output of the radio frequency generator and the input of the transmission line, and therefore refers to the established discriminator distance from the functional block. In other words, when in a fixed position, the radio frequency discriminator is physically distant from the functional block by this discriminator distance which is fixed (i.e. it is not variable). Since the output of the radio frequency generator and the input of the functional block are electrically connected through the radio frequency discriminator and the transmission line, the physical position of the radio frequency discriminator is included in (or is on) the chain length.

[0036] Once it is placed between the output of the radio frequency generator and the input of the transmission line, the radio frequency discriminator is not intended to be moved during the implementation of the impedance matching method. This is why the physical position of the radio frequency discriminator is referred to as a fixed position. The decoupling that the radio frequency discriminator achieves between the two degrees of freedom of the impedance matching network is digital. From the knowledge of the reflection coefficient at the fixed position where the radio frequency discriminator is positioned, the reflection coefficient and the impedance at any point (hereinafter called the test point) located upstream of the functional block at a distance called the test distance can be calculated. In a way, this amounts to “fictitiously” moving the radio frequency discriminator from its fixed position to this test point on the physical radio frequency application chain.

[0037] Once the impedance at the test point is calculated, the first variable component and the second variable component are manipulated / driven to determine whether or not the test distance corresponds to the first distance of interest or the second distance of interest.

[0038] As stated above, the first distance of interest is determined when the modulus of the impedance (i.e., the modulus of the first impedance) seen at that first distance of interest varies only as a function of one of the two degrees of freedom of the impedance matching network (i.e., as a function of the first variable component) around the value of the reference modulus (which is typically 50 Ohms).

[0039] The second distance of interest is determined when the imaginary part of the impedance (i.e., the imaginary part of the second impedance) seen at this second distance of interest varies only as a function of the other of the two degrees of freedom of the impedance matching network (i.e., as a function of the second variable component) around the value of the reference imaginary part. The reference imaginary part is generally zero, the impedance matching of a radiofrequency application chain being often carried out for 50 Ohms.

[0040] In the case where the specific conditions for the first impedance or the second impedance at the test point / test distance are not met, another test point / test distance is considered on the radiofrequency application chain. When a test distance is identified as corresponding to the first or second distance of interest, it is stored by the control unit.

[0041] Once the two distances of interest have been identified, the impedance matching process finally implements the adaptation phase to adapt the impedance of the radiofrequency application chain.

[0042] In addition to memorizing the two distances of interest, the control unit is also designed to communicate:

[0043] - during the identification phase, with the radiofrequency discriminator for calculating the reflection coefficients and / or impedances at the test points and determining the two distances of interest, and

[0044] - with the impedance matching network for adjusting / setting the first and second variable components during the adaptation phase.

[0045] In a first embodiment of the invention, the control unit is an integral part of the radiofrequency discriminator, and corresponds for example to a microprocessor and / or an electronic card which contains a program relating to the execution of the impedance matching method. In this mode, the radiofrequency discriminator is therefore connected and / or in communication with the impedance matching network.

[0046] In a second variant embodiment of the invention, the control unit is an external system, such as a workstation (for example a desktop computer), connected and / or in communication with the radiofrequency discriminator, and comprising software for: controlling the radiofrequency discriminator and the impedance matching network, and implementing the impedance matching method.

[0047] An advantage of the impedance matching method is that it allows for continuous and automated matching. Indeed, in the event that an impedance mismatch occurs on the radiofrequency application chain after the implementation of the matching phase, a new impedance matching phase is performed with the control unit again controlling the impedance matching network for the adjustment of the two variable components, without it being necessary to implement the determination and identification phases again. Indeed, the location of the two positions of interest is not dependent on the matching or mismatching of the impedance of the radiofrequency application chain. In other words, the location of the two positions of interest does not change if a mismatch occurs.

[0048] According to a characteristic of the invention, the determination step comprises at least:

[0049] - a measurement step during which the radiofrequency discriminator physically measures (over the length of the chain) at least one direct voltage and one reflected voltage,

[0050] - a calculation step during which the modulus and phase of the reflection coefficient at the fixed position are at least calculated from a ratio of the reflected voltage to the direct voltage.

[0051] In other words, the radio frequency discriminator calculates the modulus and phase of the reflection coefficient at the fixed position where the radio frequency discriminator is located, then the corresponding impedance, from a direct voltage (also called incident voltage) and a reflected voltage measured by it (and which are both attenuated by the same coupling factor).

[0052] In one embodiment of the invention, in order to measure the direct and reflected voltages, the radiofrequency discriminator contains a bidirectional coupler.

[0053] According to one embodiment of the invention, during the measurement step a delayed reflected voltage is also measured which is delayed by a given delay relative to the direct voltage, and during the calculation sub-step the following are calculated:

[0054] - the modulus of the reflection coefficient at the fixed position from a modulus of the ratio of the reflected voltage to the direct voltage,

[0055] - a cosine of the phase of the reflection coefficient at the fixed position from at least one argument of the ratio of the reflected voltage to the direct voltage,

[0056] - a sine of the phase from at least one argument of the ratio of the delayed reflected voltage to the direct voltage,

[0057] - the phase of the reflection coefficient at the fixed position which is equal to a cotangent of a ratio of the cosine of the phase to the sine of the phase.

[0058] A control unit can calculate, from the ratio of a reflected voltage to a direct voltage measured by a modulus and phase detector, the modulus and phase of the reflection coefficient at a position along the length of the radiofrequency application chain with: the modulus being equal to the modulus of the ratio between the two voltages; and the phase being equal to the argument of the ratio between the two voltages. However, if commercially available modulus and phase detectors can determine voltages that are functions of the modulus and the phase, the control unit can then deduce / calculate the modulus of the reflection coefficient over a 360° interval, as some detector references are not capable of distinguishing between positive and negative phases of voltage signals. As a reminder, the positive phase is between 0° and 180°, and the negative phase between 0° and -180°.

[0059] Advantageously, the impedance matching method allows calculating the phase of the reflection coefficient and is applicable for any type / reference of module and phase detector. In the case where designers have no other alternative than to use phase detectors covering the phase over 180° and therefore only being able to detect a positive phase or a negative phase, an additional voltage is measured during the measurement step. This additional voltage corresponds to the reflected voltage but delayed / phase shifted by a certain time delay, and which is called delayed reflected voltage.

[0060] The modulus of the reflection coefficient remains calculated as explained above, being equal to the modulus of the ratio between the reflected voltage and the direct voltage.

[0061] The phase is determined from the calculation of the cotangent of the ratio of its cosine to its sine. The cosine of the phase is obtained by calculating the argument of the ratio of the reflected voltage to the forward voltage. The sine of the phase is obtained by calculating the argument of the ratio of the delayed reflected voltage to the forward voltage.

[0062] In a preferred embodiment of the invention, the radiofrequency discriminator contains two module and phase detectors.

[0063] One of the two detectors is used to measure the direct voltage and the reflected voltage, which will be used by the control unit to calculate the cosine of the phase of the reflection coefficient at the fixed position.

[0064] The other of the two detectors is used to measure the direct voltage and the delayed reflected voltage, which will be used by the control unit to calculate the sine of the phase of the reflection coefficient at the fixed position.

[0065] Following these two calculations, the control unit finally calculates the phase of the reflection coefficient. According to one embodiment of the invention, the delay defining the delayed reflected voltage is equal to 90°, to within plus or minus 15 degrees.

[0066] In a preferred embodiment of the invention, the delay defining the delayed reflected voltage is between 90 degrees and 100 degrees.

[0067] In other words, the phase of the reflection coefficient at the fixed position is calculated with the best possible accuracy when the delayed reflected voltage is delayed by 90° relative to the forward voltage, i.e., when the delayed reflected voltage and the forward voltage are in quadrature.

[0068] However, the delayed reflected voltage does not need to be strictly delayed by 90° relative to the forward voltage. A slight tolerance is permissible in the delay value considered.

[0069] Indeed, and advantageously in the case where the radiofrequency discriminator used or designed does not allow a measurement of the reflected voltage with a phase shift of 90° relative to the direct voltage, the impedance matching method remains valid when the delay is less than 90° and greater than or equal to 80°, or if it is greater than 90° and less than or equal to 100°. In these two delay value intervals, the phase value of the reflection coefficient at the fixed position obtained may be less precise than that obtained for a phase shift of 90°. This inaccuracy in the calculation of the phase of the reflection coefficient at the fixed position may induce an inaccuracy in the calculation of the first and second impedances during the first and second identification steps.However, the inaccuracies in the determination of the first and second impedances have no impact on the adaptation phase: the values ​​of the first and second variable components for the impedance adaptation of the radiofrequency application chain remain determined precisely.

[0070] According to an embodiment characteristic of the invention, during the first identification step and the second identification step, the first impedance and the second impedance are calculated as a function of a wave vector characteristic of the electromagnetic wave generated by the radiofrequency generator.

[0071] The control unit is able to determine the impedance (modulus and phase) at the fixed position from the reflection coefficient calculated at this same position.

[0072] It is also capable of calculating the reflection coefficient of any position located between the fixed position and the input of the functional block; which fictitiously amounts to physically moving and placing the radiofrequency discriminator at this position. The reflection coefficient at this new position, which may possibly correspond to the first or second position of interest, is calculated from: the reflection coefficient at the fixed position, the distance separating this new position from the functional block, and a wave vector representative of the propagation of the wave generated by the radiofrequency generator on the radiofrequency application chain. From the reflection coefficient of the new position, the control unit deduces the impedance at said new position, said impedance possibly corresponding to the first impedance or the second impedance.

[0073] Note that considering the negligible line attenuation over the entire chain length of the radiofrequency application chain, the modulus of the reflection coefficient does not change whatever the position considered between the radiofrequency discriminator and the functional block. On the other hand, for the same value of the modulus of the reflection coefficient, the real part and the imaginary part of the reflection coefficient can vary for two distinct positions; similarly for the real part and the imaginary part of the impedance deduced from the reflection coefficient.

[0074] According to a characteristic of the invention, the first identification step comprises the following sub-steps:

[0075] - a sub-step of selecting a first test point which is distant from the functional block by a first test distance,

[0076] - a sub-step of calculating a reflection coefficient at the first test point from the reflection coefficient at the fixed position, the first test distance and the wave vector,

[0077] - a sub-step of calculating an impedance at the first test point from the reflection coefficient at the first test point,

[0078] - a step of determining a module of the impedance at the first test point,

[0079] - a test sub-step during which monitoring of the impedance modulus at the first test point is implemented by varying the value of the first variable component and the value of the second variable component, in order to test the dependence of the impedance modulus at the first test point as a function of these two values; and if the impedance modulus at the first test point varies only as a function of the value of the first variable component, then the first distance of interest corresponds to the first test distance; otherwise the first test distance is modified, and the first identification step is repeated.In other words, the control unit considers a test point (referred to as the first test point) located on the radiofrequency application chain between the output of the radiofrequency discriminator and the input of the functional block, then implements the first identification step in order to determine whether the distance separating the functional block from this first test point, called the first test distance, corresponds or not to the first distance of interest. To do this, it calculates the reflection coefficient (module and phase) at this first test point, then the corresponding impedance from which it then deduces the modulus. The variable components of the impedance matching network are then manipulated / adjusted to vary their value in order to test the dependence of the modulus of the impedance obtained at the first test point on these variations.

[0080] If the impedance modulus at the first test point depends only on variations in one of the two variable components (here the first variable component), then the first test distance is identified as the first distance of interest and then stored by the control unit. If not, the first identification step is repeated as many times as necessary until a first distance of interest is identified.

[0081] According to a characteristic of the invention, the second identification step comprises the following sub-steps:

[0082] - a sub-step of selecting a second test point which is distant from the functional block by a second test distance,

[0083] - a sub-step of calculating a reflection coefficient at the second test point from the reflection coefficient at the fixed position, the second test distance and the wave vector,

[0084] - a sub-step of calculating an impedance at the second test point from the reflection coefficient at the second test point,

[0085] - a sub-step of determining an imaginary part of the impedance at the second test point;

[0086] - a test sub-step during which monitoring of the imaginary part of the impedance at the second test point is implemented by varying the value of the first variable component and the value of the second variable component, in order to test the dependence of the imaginary part of the impedance at the second test point as a function of these two values; and if the imaginary part of the impedance at the second test point varies only as a function of the value of the second variable component, then the second distance of interest corresponds to the second test distance; otherwise the second test distance is modified and the second identification step is repeated.

[0087] Similar to the first identification step, the control unit determines during a second identification step whether the second test distance separating the functional block from a second test point located on the radiofrequency application chain between the radiofrequency discriminator and the functional block corresponds or not to the second distance of interest. After calculating the phase of the impedance at this second test point, the variable components of the impedance matching network are manipulated to vary their value in order to test the dependence of the imaginary part of the impedance at the second test point on these variations.

[0088] If the imaginary part of the impedance at the second test point depends only on the other of the two degrees of freedom / variable components, then the second test distance is identified as the second distance of interest. The control unit then stores the second distance of interest as well as the imaginary part of the second impedance. If not, the control unit repeats the second identification step as many times as necessary until a second distance of interest is identified.

[0089] Depending on the application context, the second distance of interest can be identified after or before the first distance of interest.

[0090] According to one embodiment of the invention, at least the adaptation phase is carried out by means of a servo system included in the impedance adaptation network and at least in communication with the control unit; said servo system comprising at least:

[0091] - a first upstream comparator, a first upstream corrector, a first downstream comparator, a first downstream corrector, and a first actuator,

[0092] - a second upstream comparator, a second upstream corrector, a second downstream comparator, a second downstream corrector, and a second actuator, with:

[0093] - the first upstream corrector connected in series at the output of the first upstream comparator, and the second upstream corrector connected in series at the output of the second upstream comparator;

[0094] - the first downstream corrector connected in series at the output of the first downstream comparator, and the second downstream corrector connected in series at the output of the second downstream comparator;

[0095] - the first actuator connected in series at the output of the first downstream comparator and connected to the first variable component, and the second actuator connected in series at the output of the second downstream comparator and connected to the second variable component; and

[0096] - the first downstream comparator having at least a first input and a second input such that the first input is connected to the output of the first upstream corrector; the second downstream comparator having at least a first input and a second input such that the first input is connected to the output of the second upstream corrector.

[0097] In other words, the adaptation network includes a control system contributing at least to the realization of the adaptation phase. The control system includes two independent control branches, with:

[0098] - one of the two servo branches dedicated to adjusting the value of the first variable component, and

[0099] - the other of the two servo branches dedicated to adjusting the value of the second variable component; this according to the control order received by the servo system from the control unit.

[0100] Each servo branch includes an upstream comparator and an upstream corrector, a downstream comparator and a downstream corrector, and an actuator whose positions in the branch are specified above, and whose respective roles are specified below.

[0101] The first actuator and the second actuator at the end of the servo branch and connected respectively to the first and second variable components are used to physically vary / adjust the values ​​of the latter.

[0102] According to one embodiment of the invention, the impedance matching method comprises:

[0103] - a first downstream correction during which the first downstream corrector generates a first adjustment voltage from a first downstream shaped voltage difference coming from the first downstream comparator;

[0104] - a second downstream correction carried out in parallel with the first downstream correction during which the second downstream corrector generates a second adjustment voltage from a second downstream shaped voltage difference coming from the second downstream comparator;

[0105] - a first adjustment during which the first actuator varies the value of the first variable component from a current value to a new value as a function of the first adjustment voltage;

[0106] - a second adjustment carried out in parallel with the first adjustment during which the second actuator varies the value of the second variable component from a current value to a new value as a function of the second adjustment voltage. In other words, the first actuator and the second actuator respectively controlling the first variable component and the second variable component vary their value from their current value to a new value from a first adjustment voltage and a second adjustment voltage. These two adjustment voltages are provided by the first downstream corrector and the second downstream corrector, generated as a function of a first downstream shaped voltage difference and a second downstream shaped voltage difference that they receive. These two downstream shaped voltage differences are defined subsequently.

[0107] According to one embodiment of the invention, the test sub-steps of the first identification step and the second identification step each comprise at least:

[0108] - a transmission during which a first control voltage and a second control voltage are transmitted to the servo system;

[0109] - a distribution such that once the first control voltage and the second control voltage have been received by the servo system, the first control voltage is sent to the input of the first downstream comparator, and the second control voltage is sent to the input of the second downstream comparator;

[0110] - a first downstream comparison during which the first downstream comparator compares the first control voltage with a first voltage position measurement representative of the current value of the first variable component, and generates the first downstream shaped voltage difference corresponding to a difference between the first control voltage and the first voltage position measurement;

[0111] - a second downstream comparison carried out in parallel with the first downstream comparison during which the second downstream comparator compares the second control voltage with a second voltage position measurement representative of the current value of the second variable component, and generates the second downstream shaped voltage difference corresponding to a difference between the second control voltage and the second voltage position measurement;

[0112] - the first downstream correction and the second downstream correction, based respectively on said first downstream shaped voltage difference and on said second downstream shaped voltage difference resulting respectively from the first downstream comparison and the second downstream comparison;

[0113] - the first setting and the second setting for which, respectively, the first actuator varies the value of the first variable component from its current value to the new value as a function of the first setting voltage, and the second actuator varies the value of the second variable component from its current value to the new value as a function of the second setting voltage.

[0114] In one embodiment of the invention, which also corresponds to the preferred embodiment, the first and second actuators are both direct current motors requiring to be supplied by analog voltages, called adjustment voltages, in order to control and adjust the values ​​of the first and second variable components.

[0115] By means of their respective actuator, the value of the first variable component is adjusted by means of a first adjustment voltage, and the value of the second variable component is adjusted by means of a second adjustment voltage.

[0116] In each of the servo-control branches of the impedance matching network, the adjustment voltage is generated by means of the association / series connection of a downstream comparator with a downstream corrector.

[0117] Each of the two downstream comparators has three independent inputs such as:

[0118] - the first of the three inputs is connected in series with the output of the upstream corrector of its control branch,

[0119] - the second input is configured to receive a voltage from a system / component external to the servo system; and

[0120] - the third input is connected to the output of the upstream corrector of its servo branch.

[0121] In order to implement the test sub-steps of the first and second identification steps, and to verify whether the modulus of the impedance at the first test distance (respectively the imaginary part of the impedance at the second test distance) depends or not only on the variations of the first variable component (respectively of the second variable component), control voltages are sent to the second input of the downstream comparator of each control branch. In other words, a first control voltage is sent to the second input of the first downstream comparator and a second control voltage is sent to the second input of the second downstream comparator.

[0122] The first and second control voltages are compared respectively with a first voltage position measurement and a second voltage position measurement. The first voltage position measurement and the second voltage position measurement are respectively representative of a position of the first actuator and a position of the second actuator, and therefore of an adjustment of the first and second variable components to given values ​​at time t. Following this comparison, the first (respectively the second) downstream comparator generates a first (respectively a second) downstream shaped voltage difference which is equal to the difference between the first (respectively the second) control voltage and the first (respectively the second) voltage position measurement.

[0123] The first and second downstream conforming voltages are sent to the input of the first and second downstream correctors for the generation of the first and second adjustment voltages which are transmitted to the actuators.

[0124] Once their respective adjustment voltage has been received, each of the actuators controls the variable component to which it is connected according to the value of the adjustment voltage, by varying its value from its current value to a new value.

[0125] The settings of the two variable components are carried out in parallel.

[0126] In one embodiment of the invention, the first and second downstream correctors each comprise a voltage shifter for adapting the voltage levels of the first and second adjustment voltages so that they are within the operating voltage range of the first and second actuators.

[0127] According to one embodiment of the invention, the impedance matching network is connected and / or in communication with a control station having a human-machine interface in which a user enters the first control voltage and the second control voltage, which will be transmitted by the control station to the impedance matching network.

[0128] In order to verify that the modulus of the impedance at the first test distance and the imaginary part of the impedance at the second test distance depend or not respectively only on the variations of the first variable component and the second variable component, several first control voltages and several second control voltages are sent to the first and second downstream comparator, so as to vary the values ​​of the two variable components several times for a reliable dependence analysis.

[0129] According to one embodiment of the invention, the adaptation phase comprises at least:

[0130] - a conversion during which the control unit converts: the module of the first impedance at the first distance of interest into a first measurement voltage representative of said module, and the imaginary part of the second impedance at the second distance of interest into a second measurement voltage representative of said imaginary part; - a transmission during which the control unit sends to the servo-control system the control order which comprises the first measurement voltage and the second measurement voltage;

[0131] - a distribution such that once the control order is received by the servo system, the first measurement voltage is sent to the input of the first upstream comparator, and the second measurement voltage is sent to the input of the second upstream comparator;

[0132] - a first upstream comparison during which the first upstream comparator compares the first measurement voltage with a first reference voltage representative of the reference module, and generates a first upstream conformal voltage difference corresponding to a difference between the first measurement voltage and the first reference voltage;

[0133] - a second upstream comparison carried out in parallel with the first upstream comparison during which the second upstream comparator compares the second measurement voltage with a second reference voltage representative of the imaginary reference part, and generates a second upstream conformal voltage difference corresponding to a difference between the second measurement voltage and the second reference voltage;

[0134] - a first upstream correction during which the first upstream corrector generates a third measurement voltage from the first upstream shaped voltage difference;

[0135] - a second upstream correction carried out in parallel with the first upstream correction during which the second upstream corrector generates a fourth measurement voltage from the second upstream shaped voltage difference;

[0136] - a first downstream comparison during which the first downstream comparator compares the third measurement voltage with a first voltage position measurement representative of a current value of the first variable component, and generates the first downstream shaped voltage difference corresponding to a difference between the third measurement voltage and the first voltage position measurement;

[0137] - a second downstream comparison carried out in parallel with the first downstream comparison during which the second downstream comparator compares the fourth measurement voltage with a second voltage position measurement representative of a current value of the second variable component, and generates the second downstream shaped voltage difference corresponding to a difference between the fourth measurement voltage and the second voltage position measurement;

[0138] - the first downstream correction and the second downstream correction, based respectively on said first downstream shaped voltage difference and on said second downstream shaped voltage difference resulting respectively from the first downstream comparison and the second downstream comparison;

[0139] - the first setting and the second setting, for which, respectively, the first actuator varies the value of the first variable component from its current value to the new value as a function of the first setting voltage, and the second actuator varies the value of the second variable component from its current value to the new value as a function of the second setting voltage.

[0140] As stated before, once a test distance is identified as the first distance of interest or the second distance of interest, it is stored by the control unit.

[0141] The adaptation phase is implemented once the two distances of interest have been identified and stored. At the start of the adaptation phase, the control unit considers the first impedance, seen at the first distance of interest, and the second impedance, seen at the second distance of interest, then converts the value of the modulus of the first impedance and the value of the imaginary part of the second impedance respectively into a first measurement voltage and a second measurement voltage which will ultimately be used to adjust the first and second variable components.

[0142] The two control voltages are sent by the control unit to the servo system of the impedance matching network. Each of the control voltages is injected into the input of the upstream comparator of each servo branch. More precisely, the first measurement voltage is injected into the input of the first upstream comparator and the second measurement voltage is injected into the input of the second upstream comparator.

[0143] The first measuring voltage (respectively the second measuring voltage) is compared to a first reference voltage (respectively a second reference voltage) upstream representative of the reference module (respectively of the imaginary reference part).

[0144] The first upstream comparator then generates a first upstream conformed voltage difference which is equal to the voltage difference between the first measurement voltage and the first setpoint voltage, and which corresponds to a difference in modulus value between the modulus value calculated at the first distance of interest and the reference modulus.

[0145] Similarly, the second upstream comparator generates a second upstream shaped voltage difference which is equal to the voltage difference between the second measurement voltage and the second reference voltage, and which corresponds to a difference in imaginary part value between the imaginary part calculated at the second distance of interest and the reference imaginary part.

[0146] The first upstream shaped voltage difference (respectively the second upstream shaped voltage difference) is then sent to the input of the first upstream corrector (respectively the second upstream corrector), which will generate from the first upstream shaped voltage difference (respectively the second upstream shaped voltage difference) a third measurement voltage (respectively a fourth measurement voltage).

[0147] In one embodiment of the invention, if necessary, the first and second upstream correctors each comprise a voltage shifter for adapting the voltage levels of the third measurement voltage and the fourth measurement voltage so that they are included in the operating voltage range of the first and second actuators.

[0148] The third measurement voltage and the fourth measurement voltage are transmitted respectively to the first and second downstream comparators, to be compared with the first voltage position measurement and the second voltage position measurement.

[0149] The first and second downstream comparator will generate a first and second downstream conformed voltage difference which will be corrected by the first and second downstream corrector, which will also generate the first and second adjustment voltage for controlling / adjusting the first and second actuator, by varying both of them from their current value until reaching a new value allowing the adaptation of the impedance over the entire length of the radiofrequency application chain.

[0150] The controls, that is to say the adjustments, of the two variable components to obtain the reference module and the reference imaginary part are carried out in parallel.

[0151] According to a characteristic of the invention, during the conversion:

[0152] - the modulus of the first impedance is converted into the first measurement voltage by means of a first injective and monotonic function having a slope around a first reference voltage value representative of the reference modulus, and

[0153] - the imaginary part of the second impedance is converted into the second measurement voltage by means of a second injective and monotonic function having a slope around a second reference voltage value representative of the reference imaginary part. In other words, during the conversion of the adaptation phase, the modulus of the first impedance at the first distance of interest and the imaginary part of the second impedance at the second distance of interest are converted into voltage by two mathematical functions. Each of the two mathematical functions is an injective and monotonic function, that is to say a function for which each modulus value (or imaginary part) corresponds to a single voltage value.

[0154] Each of the injective functions has a slope around a reference voltage value corresponding, depending on the injective function considered, to the voltage value representative of the reference module or the reference imaginary part.

[0155] According to a characteristic of the invention, the impedance matching method is such that:

[0156] - the first injective and monotonic function is defined in a first voltage interval by being bounded by a first minimum bound and a first maximum bound; the first minimum bound being representative of an impedance module value equal to zero, and the first maximum bound being representative of an impedance module value tending towards infinity; and

[0157] - the second injective and monotonic function is defined in a second voltage interval by being bounded by a second minimum bound and a second maximum bound; the second minimum bound being representative of a value of the imaginary part of impedance tending towards minus infinity, and the second maximum bound being representative of a value of the imaginary part of impedance tending towards plus infinity.

[0158] By definition, the value of the impedance modulus lies between zero and infinity, while the value of the imaginary part lies between negative infinity and infinity. This is why the first and second injective and monotonic functions are bounded as described above, with the minimum and maximum bounds corresponding to the limiting values ​​(low and high) that the modulus and the imaginary part can take.

[0159] According to one embodiment of the invention, the first reference voltage value corresponds to an average value of the first voltage interval, and the second reference voltage value corresponds to an average value of the second voltage interval.

[0160] According to one embodiment of the invention, the impedance matching method is such that:

[0161] - the first minimum terminal and the first maximum terminal are respectively equal to -0.2 Volts and 0.2 Volts, with the first reference voltage value equal to zero; and

[0162] - the second minimum terminal and the second maximum terminal are respectively equal to -0.2 Volts and 0.2 Volts, with the second reference voltage value equal to zero.

[0163] In other words, the two reference voltage values ​​are defined such that for:

[0164] - the first injective and monotonic function, the first reference voltage value, representative of a reference module equal to 50 Ohms, is zero; and

[0165] - the second injective and monotonic function, the second reference voltage value is equal, representative of a zero imaginary part, is equal to zero.

[0166] According to one embodiment of the invention, the first setpoint voltage is equal to the first reference voltage value, and the second setpoint voltage is equal to the second reference voltage value.

[0167] According to one embodiment of the invention, the reference impedance is equal to 50 Ohms, that is to say: that the reference modulus of the reference impedance is equal to 50 Ohms; and that the reference imaginary part of the reference impedance is zero.

[0168] According to one embodiment of the invention, the impedance matching method is such that the first variable component and the second variable component:

[0169] - each correspond either to a variable capacitor or to a variable inductance; and

[0170] - are either in series with the transmission line or in parallel with it.

[0171] [Brief description of the figures]

[0172] Other characteristics and advantages of the present invention will appear on reading the detailed description below, of a non-limiting example of implementation, made with reference to the appended figures in which:

[0173] [Fig 1] is a flowchart showing the main steps implemented in the impedance matching process;

[0174] [Fig 2] is a schematic view of an entire radiofrequency application chain for which the impedance matching method is implemented, with: a load at the end of the chain associated with an impedance matching network with two degrees of freedom, both forming a functional block powered through a transmission line by a radiofrequency generator; and a radiofrequency discriminator which is positioned at a fixed position at the output of the radiofrequency generator and upstream of the impedance matching networks, which radiofrequency discriminator carries out impedance measurements seen at separate distances from the functional block in order to decouple and independently control the two degrees of freedom of the impedance matching network to adapt the impedance over the entire length of the chain;

[0175] [Fig 3] is a schematic view illustrating the servo system contained in the impedance matching network and which is configured to control the two degrees of freedom, which correspond to two variable components, as a function of control orders coming from a control unit integrated in the radiofrequency discriminator;

[0176] [Fig 4] is a flowchart of a determination phase included in the impedance matching method for determining a reflection coefficient at the position where the radiofrequency discriminator is located;

[0177] [Fig 5] is an illustration of the evolution of two voltages called first analog phase and second analog phase, with: the first analog phase (curve Cl) representative of an argument of the ratio of a reflected voltage to a direct voltage which are both measured on the transmission line by the radiofrequency discriminator; and the second analog phase representative of an argument of the ratio of a delayed reflected voltage to the direct voltage, with the reflected voltage also delayed which is measured on the transmission line by the radiofrequency discriminator and which is phase shifted by a delay of 90° (curve C2) and a delay of 100° (curve C3) with respect to the direct voltage;

[0178] [Fig 6] illustrates three evolution curves corresponding respectively to the evolution of the cosine of the phase of the reflection coefficient at the fixed position which is calculated from the first analog phase (curve C4); and of the sine of the phase of the reflection coefficient at the fixed position which is calculated from the second analog phase when the delayed reflected voltage is measured with a delay of 90° (curve C5) and 100° (curve C6);

[0179] [Fig 7] illustrates an evolution of the phase of the reflection coefficient at the fixed position, which is determined from the calculation of the cotangent of the cosine of the phase on the sine of the phase, for a delayed reflected voltage shifted by 90° (curve C7) and 100° (curve C8);

[0180] [Fig 8] illustrates a flowchart of a first identification step implemented in the impedance matching method and taking place after the determination step, with the aim of identifying a first position of interest on the radiofrequency application chain, between the radiofrequency generator output and the input of the impedance matching network, such that the modulus of an impedance calculated at this first position varies only as a function of one of the two degrees of freedom of the impedance matching network around the reference impedance, which first identification step comprises a first calculation phase during which the impedance at the first position is calculated and a first test phase during which the dependence of the modulus of the impedance on the variations of the two variable components is tested;

[0181] [Fig 9] is a flowchart of a second identification step implemented in the impedance matching method and taking place after the determination step, in parallel with the first identification step, with the aim of identifying a second position of interest on the radiofrequency application chain, between the radiofrequency generator output and the input of the impedance matching network, such that an imaginary part of the impedance calculated at this second position varies only as a function of the other of the two degrees of freedom of the impedance matching network around the reference impedance, which second identification step comprises a second calculation phase during which the impedance at the second position is calculated and a second test phase during which the dependence of the imaginary part of the impedance on the variations of the two variable components is tested;

[0182] [Fig 10] is a flowchart of a test sub-step implemented during the first and second identification steps.

[0183] [Fig 11] is a flowchart detailing the set of steps included in an adaptation phase implemented following the identification of the first and second distances of interest, and during which the first variable component and the second variable component are controlled / adjusted independently in order to adapt the impedance of the radiofrequency application chain over its entire chain length, as a function of the modulus of the first impedance and the imaginary part of the second impedance.

[0184] [Detailed description of one or more embodiments of the invention]

[0185] With reference to Figures 1 to 3, the impedance matching method P is implemented to match the impedance of a radiofrequency application chain over its entire chain length dL. The term chain length dL refers to a physical length of electrical connection between an upstream device of a radiofrequency application chain and a downstream device of said radiofrequency application chain. In the application context illustrated in Figure 2, the radiofrequency application chain comprises upstream a radiofrequency generator 2 generating an electromagnetic wave and having a reference impedance Zref defined at least by a reference module Mref and / or an imaginary reference part Imref.The radiofrequency generator 2 is used to supply, via a transmission line 3 whose characteristic impedance is matched to the reference impedance Zref, a load 5, also called an applicator, located downstream of the radiofrequency application chain. The impedance of the load 5 is not matched / is not equal to the reference impedance Zref, causing the radiofrequency application chain to be mismatched.

[0186] In the following description, the reference impedance Zref is considered to be 50 Ohms. Thus, the reference modulus Mref is equal to 50 Ohms and the reference imaginary part Imref is equal to zero.

[0187] In order to adapt the impedance of the radiofrequency application chain, the impedance adaptation method P involves an impedance adaptation network 4 with two degrees of freedom comprising a first variable component XI and a second variable component X2, and which is placed upstream of the load 5. This impedance adaptation network 4 is physically positioned between the output of the transmission line 3 and the load 5. In the remainder of the description, it is considered that the series connection of the impedance adaptation network 4 and the load 5 constitutes a functional block 6.

[0188] The impedance matching method P also involves a radiofrequency discriminator 1 physically positioned between the output of the radiofrequency generator 2 and the input of the transmission line 3. In other words, the radiofrequency discriminator 1 is physically distant from the functional block 6 (in other words from the input of the functional block 6) by a fixed (and therefore non-variable) discriminator distance dO.

[0189] In the context of the invention, the chain length dL refers to the physical length of electrical connection between the output of the radiofrequency generator 2 and the input of the functional block 6 (more precisely, the input of the impedance matching network 4 placed upstream of the load 5). It includes:

[0190] - a length of a connecting cable used to physically and electrically connect the output of the radiofrequency generator 2 to the input of the radiofrequency discriminator 1;

[0191] - a dimension of the radiofrequency discriminator 1 given in the length direction;

[0192] - the length of the transmission line 3.

[0193] Optionally, the chain length dL also includes a length of another connecting cable used to physically and electrically connect the output of the radio frequency discriminator 1 with the input of the transmission line 3, in the case where the output of the radio frequency discriminator 1 is not connected directly to the input of the transmission line 3.

[0194] Metrically, the chain length dL is equal to the sum of these different lengths.

[0195] Since the output of the radio frequency generator 2 and the input of the functional block 6 are electrically connected via the radio frequency discriminator 1 and the transmission line 3, the physical position of the radio frequency discriminator 1 is included in (or lies on) the chain length dL.

[0196] Once it is placed between the output of the radio frequency generator 2 and the input of the transmission line 3, the radio frequency discriminator 1 is not intended to be moved during the implementation of the impedance matching method. This is why the physical position of the radio frequency discriminator 1 is subsequently referred to as the fixed position pO.

[0197] The impedance matching method P is remarkable in that the radiofrequency discriminator 1 makes it possible to measure at particular points along the chain length dL, positioned upstream of the functional block 6, impedances such that they make it possible to carry out a decoupling between the two degrees of freedom of the impedance matching network, in order to control them individually to carry out the impedance matching, without it being necessary to physically move said radiofrequency discriminator 1 to these particular points. In other words, the decoupling of the two degrees of freedom (i.e. the decoupling of the first and second variable components XI, X2) is carried out digitally, with the radiofrequency discriminator 1 remaining in its fixed position pO at the output of the radiofrequency generator 2. In a certain way, this amounts to “fictitiously” moving the radiofrequency discriminator from its fixed position to these particular points.More details are given later, when the operating principle of the P impedance matching process is detailed.

[0198] With reference to Figure 3, the impedance matching network 4 comprises a servo system shaped to drive the two variable components XI, X2. More precisely, the servo system comprises two servo branches, which can be described as the first and second servo branches, each shaped to drive one of the two variable components XI, X2. For each of the servo branches, several elements are cascaded. These are the same for each of them.

[0199] Thus, the first (respectively the second) branch of control includes:

[0200] - a first upstream comparator CFI (respectively a second upstream comparator CF2) having two inputs and one output;

[0201] - a first upstream corrector RFI (respectively a second upstream corrector RF2) whose input is put in series with the output of the first upstream comparator CFI (respectively a second upstream comparator CF2);

[0202] - a first downstream comparator CB1 (respectively a second downstream comparator CB2) having three inputs and one output, for which: the first of the three inputs is put in series with the output of the upstream corrector of its control branch, the second input is configured to receive a voltage from a system / component external to the control system, and the third input is connected to the output of the corrector of the first upstream corrector RFI (respectively a second upstream corrector RF2);

[0203] - a first downstream corrector RB1 (respectively a second downstream corrector RB2) whose input is connected in series with the output of the first downstream comparator CB1 (respectively a second downstream comparator CB2);

[0204] - a first actuator Al (respectively a second actuator A2) whose input is connected in series with the output of the first downstream corrector RB1 (respectively a second downstream corrector RB2), and whose output is connected to the first variable component XI (respectively to the second variable component X2) for controlling and adjusting their value.

[0205] The role of each of the elements is specified later.

[0206] According to a first embodiment of the invention, the first variable component XI corresponds to a capacitance, and the second variable component X2 to an inductance; or vice versa in a second embodiment. In a third mode and a fourth mode, the two variable components XI, X2 are both capacitances, or inductances.

[0207] According to two embodiments of the invention, the two variable components XI, X2 are placed, on the radiofrequency application chain, either in series or in parallel. The impedance adaptation method P is implemented by a control unit 10 attached to the radiofrequency discriminator 1 and to the impedance adaptation network 4.

[0208] In a first embodiment of the invention, the control unit 10 is an external system, such as a workstation (for example a desktop computer), connected and / or in communication with the radiofrequency discriminator 1 and the impedance matching network 4, and comprising software for implementing the impedance matching method P. The radiofrequency discriminator 1 and the impedance matching network 4 are not connected to each other directly, but indirectly via the control unit 10.

[0209] In a second variant embodiment, which corresponds to that illustrated in Figure 1, the control unit 10 is an integral part of the radiofrequency discriminator 1, and corresponds for example to a microprocessor and / or an electronic card which contains a program relating to the execution of the impedance adaptation method.

[0210] With reference to Figure 1 and Figure 4, the impedance matching process P begins with a DP determination phase during which the radiofrequency discriminator 1 determines the reflection coefficient SllpO at the fixed position pO where it is installed.

[0211] To do this, by means of a bidirectional coupler that it integrates (and not illustrated in the figures), the radiofrequency discriminator 1 measures during a measurement step E01 at least one direct voltage Vd (or incident voltage) and one reflected voltage Vr. From these two voltages, the radiofrequency discriminator calculates, during a calculation step E02 and according to the equations Eq.l to Eq.3, the reflection coefficient SllpO from the two measured voltages Vd, Vr, from which it can also deduce its module M_Sllp0 and its phase P_SllpO.

[0212] Vr / Cf Vr

[0213] SllpO = Eq.l

[0214] Vd / Cf Vd

[0215] Note that the direct voltage Vd and the reflected voltage Vr are both attenuated by the same coupling factor Cf, which does not intervene as shown by the three previous equations in the calculation of the modulus M_SllpO and the phase P_SllpO of the reflection coefficient SllpO at the fixed position pO.

[0216] In one embodiment of the invention, the radiofrequency discriminator comprises a module and phase detector whose role is to calculate the module M_SllpO and the phase P_SllpO from the two measured voltages Vd, Vr, then to transmit them to the control unit 10.

[0217] However, while commercially available modulus and phase detectors can deduce / calculate the modulus of a reflection coefficient over a 360° interval, some detector references are not able to distinguish, for the phase calculation, the positive phases from the negative phases of voltage signals. As a reminder, the positive phase of a voltage signal is between 0° and 180°, and the negative phase between 0° and -180°. Thus, while they are able to calculate the actual modulus M_Sllp0 of the reflection coefficient SllpO at the fixed position pO, they are not able to calculate its actual phase P_SllpO.

[0218] In order to resolve this problem, in another embodiment of the invention, the radiofrequency discriminator 1 comprises two module and phase detectors, ideally of the same reference, which can be analog detectors delivering voltages which are functions of the module and the phase.

[0219] One of the two modulus and phase detectors, or first detector, is configured to measure the direct voltage and the reflected voltage, which will be used to calculate the modulus M_Sllp0 of the reflection coefficient SllpO at the fixed position pO, and also to calculate an argument of the ratio of the reflected voltage Vr to the direct voltage Vd which corresponds to the cosine of the phase P_SllpO of the reflection coefficient SllpO.

[0220] The other of the two module and phase detectors, or second detector, is configured to measure the direct voltage but also a delayed reflected voltage Vr_d, which corresponds to the reflected voltage Vr but delayed / phase shifted by a delay dly. These two voltages will be used to calculate an argument of the ratio of the delayed reflected voltage Vr_d to the direct voltage Vd, which corresponds to the sine of the phase P_SllpO.

[0221] The first detector and the second detector are connected to the control unit 10 which calculates the cosine and sine of the phase P_SllpO of the reflection coefficient SllpO. Once the cosine and sine of the phase P_SllpO are calculated, the control unit 10 determines the phase P_SllpO of the reflection coefficient SllpO at the fixed position pO by calculating its cotangent. In other words, these modulus and phase detectors are designed to provide respective voltages, called analog phases P_anal and P_ana2, which are functions of the phase and the modulus.

[0222] In other words, the first detector and the second detector respectively provide a first analog phase P_anal and a second analog phase P_ana2 representing respectively the argument of the ratio of the reflected voltage Vr to the direct voltage Vd (Eq.4) and the argument of the ratio of the delayed reflected voltage Vr_d to the direct voltage Vd (Eq.5).

[0223] The first analog phase P_anal and the second analog phase P_ana2 are transmitted by the first detector and the second detector to the control unit 10. The control unit 10 then first calculates the cosine and the sine of the phase P_SllpO of the reflection coefficient SllpO can be deduced respectively from the first analog phase P_anal and the second analog phase P_ana2 from the following equations: Finally, the control unit 10 deduces from the equations Eq.6 and Eq.7 the phase

[0224] P_SllpO of the reflection coefficient SllpO by calculating its cotangent such that:

[0225] ( (P ana cos ( - 1801 \

[0226] P_SllpO = cotan. (P_ana2 \ Eq.8 s in l — ïô - 1-90 ) /

[0227] Referring to Figure 7, the actual phase P_SllpO of the reflection coefficient SllpO at the fixed position pO is calculated with the best possible accuracy from the first analog phase P_anal and the second analog phase P_ana2 when the delayed reflected voltage Vr_d is measured with a delay dly of 90° with respect to the direct voltage Vd, i.e. when the two voltages are in quadrature.

[0228] However, the delayed reflected voltage Vr_d does not need to be strictly delayed by a 90° delay dly relative to the forward voltage. A slight tolerance is permissible in the considered delay value dly.

[0229] In the case where the radiofrequency discriminator 1 does not allow a measurement of the reflected voltage Vr with a phase shift of 90° compared to the direct voltage Vd, the calculation of the real phase P_SllpO remains valid when the delay dly remains between 75° and 105°.

[0230] Figure 5 illustrates examples of the evolution of the first analog phase P_anal; and of the second analog phase P_ana2 when a delay dly of 90° and 100° is considered for the delayed reflected voltage Vr_d with respect to the direct voltage Vd.

[0231] The phase shift for which the delayed reflected voltage Vr_d was measured is directly reflected in the evolution of the analog phases P_anal, P_ana2. It is observable that the second analog phase P_ana2, depending on the delay value dly considered, is shifted by 90° or 100° relative to the first analog phase P_anal; or that the curves C2, C3 devolution of the second analog phase P_ana2 are shifted / phase-shifted by 10°.

[0232] This 10° shift is also observable in Figure 6 which shows examples of the evolution of the cosine of the phase P_SllpO which is calculated from the first analog phase (curve C4); and of the sine of the phase P_SllpO which is calculated from the second analog phase when the delayed reflected voltage Vr_d is measured with a delay dly of 90° (curve C5) and 100° (curve C6) with respect to the direct voltage Vd.

[0233] Figure 7 shows the evolutions of the phase P_SllpO when it is calculated from equation Eq. 8 and when a delay dly of 90° (curve C7) or 100° (curve C8) is considered for the delayed reflected voltage. Both evolutions show that the phase shift of 10° leads to a slight inaccuracy in the estimation of the value of the real phase P_SllpO. Nevertheless, both curves C7, C8 show that the real phase P_SllpO remains calculated with a good degree of accuracy when a delay dly of 100° is considered for the delayed reflected voltage Vr_d.

[0234] Furthermore, ultimately, these estimation errors have no impact during the impedance matching of the radiofrequency application chain and the adjustment of the first and second variable components XI, X2. From the knowledge of the reflection coefficient SllpO at the fixed position pO, the radiofrequency discriminator 1, more precisely the control unit 10, is capable of calculating the reflection coefficient at any point of the radiofrequency application chain located between the fixed position pO and the input of the functional block 6, that is to say the input of the impedance matching network 4. This amounts fictitiously to physically moving and positioning the radiofrequency discriminator at a position different from the fixed position pO between the output of the radiofrequency generator 2 and the input of the functional block 6.

[0235] The control unit is capable of calculating the reflection coefficient at any other position of the radiofrequency application chain from: the reflection coefficient SllpO at the fixed position pO, the distance separating this new position from the functional block 6 (in other words, the distance separating the fixed position pO from the new position), and a wave vector k representative of the propagation of the wave generated by the radiofrequency generator 2 on the radiofrequency application chain.

[0236] It is considered in the implementation of the impedance matching method P that the line attenuation is negligible over the entire chain length dL. Consequently, whatever the new position considered between the radiofrequency generator 2 and the functional block 6, the modulus of the reflection coefficient calculated in this new position is equal to the modulus M_SllpO of the reflection coefficient SllpO at the fixed position pO. On the other hand, for the same value of the reflection coefficient modulus (here the modulus M_SllpO), the real part and the imaginary part defining the reflection coefficient can vary for two distinct positions; similarly for the real part and the imaginary part of an impedance deduced from said reflection coefficient.

[0237] Following completion of the determination phase DP, an identification phase IP is implemented with the objective of decoupling and independently controlling the first and second variable components XI, X2 to adapt the impedance of the radiofrequency application chain. A first position of interest pl, respectively a second position of interest p2, are sought, distant from the input of the functional block 6 by a first distance of interest dl, respectively a second distance of interest d2 such that:

[0238] - the modulus MZ1 of the impedance at the first position of interest pl (or at the first distance of interest dl), called the first impedance Zl, varies only as a function of the variations of one of the two degrees of freedom of the impedance matching network 4 of the reference impedance Zref, i.e. here 50 Ohms. It is considered that the modulus MZ1 varies as a function of the variations of the first variable component XI; - the imaginary part lmZ2 of the impedance at the second position of interest p2 (or at the second distance of interest d2), called the second impedance Z2, varies only as a function of the variations of the other of the two degrees of freedom of the impedance matching network 4 around the reference impedance Zref, i.e. here 50 Ohms. It is considered that the imaginary part MZ2 varies as a function of the variations of the second variable component X2.

[0239] The IP identification phase comprises a first identification step and a second identification step which are respectively dedicated to the identification of the first position of interest pl (or the first distance of interest dl) and the second position of interest p2 (or the second distance of interest d2) on the radiofrequency application chain.

[0240] Note that the first position of interest pl and the second position of interest p2 are determined numerically by the control unit 10. The first distance of interest dl and the second distance of interest d2 are therefore virtual distances. Thus, from the reflection coefficient SllpO determined at the fixed position pO, the control unit is able to numerically determine a first position of interest pl and a second position of interest p2 located:

[0241] - downstream of the radiofrequency discriminator 1, as illustrated in Figure 2 and considered subsequently; or

[0242] - upstream of the latter (for example, in the diagram of Figure 2, between the output of radiofrequency generator 2 and the input of radiofrequency discriminator 1). In another application context, the positions of interest pl, p2 can even be located upstream of the output of radiofrequency generator 2.

[0243] With reference to Figure 8 and Figure 9, the first and second identification steps E1, E2 both start for a selection sub-step E11, E21 during which the control unit 10 selects between the fixed position p0 and the input of the functional block 6 a test point (respectively called first test point and second test point for the first identification step E1 and the second identification step E2) located, on the transmission line 3, at a test distance (respectively called first test distance dt1 and second test distance dt2 for the first identification step E1 and the second identification step E2) from the functional block 6.

[0244] After having chosen a first test point ptl (respectively a second test point pt2), the control unit 10 calculates during a calculation sub-step E12, E22 the reflection coefficient Sllptl, Sllpt2 at the first test point ptl (respectively at the second test point pt2). It then calculates / deduces, during another calculation sub-step E13, E23, from the reflection coefficient Sllptl, Sllpt2, the impedance Zptl at the first test point ptl or the impedance Zpt2 at the second test point pt2 (depending on whether the first identification step El or the second identification step E2 is implemented).

[0245] The first identification step El continues with a determination sub-step E14 during which the control unit 10 deduces, from the impedance Zptl at the first test point ptl, the modulus Mptl of said impedance Zptl.

[0246] The second identification step E2 continues with a determination sub-step E24 during which the control unit 10 deduces, from the impedance Zpt2 at the first test point pt2, the imaginary part Impt2 of said impedance Zpt2.

[0247] The variations of the modulus Mptl of the impedance Zptl at the first test point ptl and the imaginary part Impt2 of the impedance Zpt2 at the second test point pt2 as a function of the variations of the first and second variable components XI, X2 are tested during the identification steps El, E2 during test sub-steps E15, E25.

[0248] In the case where the value of the modulus Mptl of the impedance Zptl at the first test point ptl depends only on the variations of the first variable component XI, then the first test point ptl is identified as being the first position of interest pl. The first test distance dtl then corresponds to the first distance of interest dl, and the impedance Zptl at the first test point ptl to the first impedance Zl. The control unit 10 keeps in memory the first distance of interest dl. Otherwise, the first identification step El is repeated / reiterated, with the control unit 10 selecting a new first test point ptl (always between the position pO and the input of the functional block 6).

[0249] Similarly, in the case where the value of the imaginary part Impt2 of the impedance Zpt2 at the second test point pt2 depends only on the variations of the second variable component X2, then the second test point pt2 is identified as being the second position of interest p2. The second test distance dt2 then corresponds to the second distance of interest d2, and the impedance Zpt2 at the second test point pt2 to the second impedance Z2. The control unit 10 keeps in memory the second distance of interest d2. Otherwise, the second identification step E2 is repeated / reiterated, with the control unit 10 selecting a new second test point pt2 (always between the position p0 and the input of the functional block 6).

[0250] As illustrated in Figure 1, the second identification step E2 is implemented after the first identification step E1. However, it is conceivable that the first identification step E1 can be implemented after the second identification step E2. In a first variant embodiment of the invention, which corresponds to the preferred embodiment of the invention, the identification phase IP, and therefore the first and second identification steps E1, E2 are semi-automated.

[0251] In this variant, during the selection sub-steps Ell, E21, the first test point ptl and the second test point pt2 are chosen by an operator implementing the impedance matching method P. For this, it interacts with the control unit 10 (if it is a remote station) or with the radiofrequency discriminator 1 (if the control unit 10 is integrated in it) by entering the first test distance dtl and the second test distance dt2.

[0252] Following this, the control unit 10 automatically calculates the reflection coefficient Sllptl at the first test point ptl and the reflection coefficient Sllpt2 at the second test point pt2 to ultimately deduce the modulus Mptl of the impedance Zptl at the first test point ptl and the imaginary part Impt2 of the impedance Zpt2 at the second test point pt2. In other words, the control unit automatically implements the calculation sub-steps E12, E13, E22, E23 and the determination sub-step E14, E24.

[0253] Once the determination sub-step E14, E24 is completed, and in order to proceed to the test sub-step E15, E25, the user interacts with a human-machine interface 21 of a control station 20 connected and / or in communication with the impedance matching network 4 in which he enters / defines a first control voltage Vpl and a second control voltage Vp2.

[0254] The two control voltages Vpl, Vp2 are transmitted during a transmission Tl to the impedance matching network 4 by the control station 20. More precisely, they are in this embodiment transmitted to a distributor 22 configured, during a distribution T2, to send the first control voltage Vpl to the second input of the first downstream comparator CB1 and the second control voltage Vp2 to the second input of the second downstream comparator CB2.

[0255] In one embodiment of the invention, the impedance matching network does not include a distributor 22, and the control station 20 directly sends the control voltages Vpl, Vp2 to the second inputs of the downstream comparators CB1, CB2.

[0256] The first control voltage Vpl and the second control voltage Vp2 are compared respectively, during a first downstream comparison T31 and a second downstream comparison T32, with a first voltage position measurement VCB1 and a second voltage position measurement VCB2 which are recovered at the level of the first actuator A1 and the second actuator A2, then injected onto the third input of the first and second downstream correctors CB1, CB2. The voltage position measurements VCB1, VCB2 are representative of a position of the two actuators A1, A2 at the present time, or also of an adjustment of the variable components X1, X2 to given values.

[0257] The first downstream comparator CB1 (respectively the second downstream comparator CB2) generates a first downstream shaped voltage difference dvbl (respectively a second downstream shaped voltage difference dvb2) which is equal to the difference between the first control voltage Vpl (respectively the second control voltage Vp2) and the first voltage position measurement VCBl (respectively the second voltage position measurement VCB2).

[0258] The first downstream shaped voltage difference dvbl and the second downstream shaped voltage difference dvb2 are then sent respectively to the input of the first downstream corrector RB1 and the second downstream corrector RB2 which will generate from these, during a first downstream correction E371 and a second downstream correction E372, a first adjustment voltage Vtunel and a second adjustment voltage Vtune2.

[0259] The two adjustment voltages Vtunel, Vtune 2 are representative of a change in position (and value) of the variable components XI, X2 from their current position / value (at time t) to a new position / value.

[0260] These position / value changes are implemented during a first adjustment E381 and a second adjustment E382 by the actuators Al, A2 connected to the variable components XI, X2 once they have received the adjustment voltages Vtunel, Vtune2 transmitted by the downstream correctors RBI, RB2.

[0261] Following these changes in position, the values ​​of the variable components previously designated as their current value become their value at time t-1, and the new values ​​in fact become their current value at time t.

[0262] The first downstream comparison T31 and the second downstream comparison T32 are carried out in parallel. The same applies to the downstream corrections E371, E372 and the adjustments E381, E382.

[0263] In one embodiment of the invention, the downstream correctors RBI, RB2 each comprise a voltage shifter for adapting the voltage levels of the adjustment voltages Vtunel, Vtune2 so that they are included in the operating voltage range of the actuators A1, A2.

[0264] In order to verify whether the modulus Mptl of the impedance Zptl at the first test distance ptl and the imaginary part Impt2 of the impedance Zpt2 at the second test distance pt2 depend or not respectively only on the variations of the first variable component XI and the second variable component X2, several first driving voltages Vpl and several second driving voltages Vp2 are transmitted to the impedance matching network 4, so as to vary the values ​​of the two variable components several times for a reliable dependence analysis.

[0265] When, following the sending of the control voltages Vp2, Vp2 and the control of the first and second variable components XI, X2, the user observes during the test sub-step E15 of the first identification step El that the module Mptl the impedance Zptl at the first test point ptl only varies as a function of the variations of the first variable component XI, it interacts with the control unit 10 to save the first test distance dtl which then corresponds to the first distance of interest dl (the module Mptl of the impedance Zptl at the first test point ptl therefore corresponding to the module MZ1 of the first impedance Zl). If not, in the case where the module Mptl depends on the variations of the two variable components XI, X2, it considers and informs the control unit 10 of a new first test point ptl.

[0266] Similarly, if the user observes during the test sub-step E25 of the second identification step E2 that the imaginary part Impt2 at the second test point pt2 only varies as a function of the variations of the second variable component X2, he interacts with the control unit 10 to save the second test distance dt2 which then corresponds to the second distance of interest d2. If not, in the case where the imaginary part Impt2 depends on the variations of the two variable components XI, X2, he considers and enters in the control unit 10 a new second test point pt2 (the imaginary part Impt2 of the impedance Zpt2 at the second test point pt2 therefore corresponding to the imaginary part lmZ2 of the second impedance Z2).

[0267] In a first variant embodiment of the invention, it is possible for the user to enter the control voltages Vpl, Vp2 from the control unit 10 which transmits them to the impedance matching network 4, making the use of a control station 20 unnecessary.

[0268] In a second embodiment, it is possible to envisage the identification steps E1, E2 being fully automated with the control unit 10:

[0269] - choosing during the selection sub-steps Ell, E21 the first and second test points ptl, pt2,

[0270] - sending during the test sub-steps E15, E25 the control voltages Vpl, Vp2 to the impedance matching network 4, then

[0271] - detecting whether the modulus Mptl of the impedance Zptl at the first test point ptl and the imaginary part Impt2 of the impedance Zpt2 at the second test point pt2 depend on the variations of a single variable component XI, X2 or both. In other words, the control unit detects whether the first test distance dtl and the second test distance dt2 correspond or not to the first distance of interest dl and second distance of interest d2.

[0272] Following the identification of the first distance of interest dl and the second distance of interest d2, the impedance adaptation method P implements a final phase called the adaptation phase AP.

[0273] During the AP adaptation phase, illustrated in Figure 11, the first variable component XI and the second variable component X2 are controlled / adjusted independently in order to adapt the impedance of the radiofrequency application chain over its entire chain length dL, this according to: the modulus MZ1 of the first impedance ZI; the imaginary part lmZ2 of the second impedance Z2; and the modulus Mref and the imaginary part Imref of the reference impedance Zref. During the AP adaptation phase, we therefore control to have MZl=Mref and lmZ2=lmref, these equalities not being immediately obtained by considering the static errors.

[0274] As indicated previously, the variable components XI, X2 are adjustable by means of two actuators A1, A2 included in the impedance matching network 4. In the embodiment of the invention described, the two actuators A1, A2 are direct current motors requiring to be supplied by analog voltages in order to ensure the adjustments of the variable components XI, X2.

[0275] In order to be able to carry out these adjustments, the modulus MZ1 of the first impedance Z1 and the imaginary part lmZ2 of the second impedance Z2 are converted by the control unit 10 during a conversion E31 respectively into two control voltages VCl, VC2. The control unit 10 carries out the two conversions by means of two injective and monotonic mathematical functions, the first injective and monotonic function being used for the conversion of the modulus MZ1 of the first impedance Z1, and the second for the conversion of the imaginary part lmZ2 of the second impedance Z2. By definition, an injective and monotonic function is a monotonic function. In other words, to each modulus MZ1 of the first impedance Z1 (respectively imaginary part lmZ2 of the second impedance Z2) corresponds a single first measurement voltage VCl (respectively a second measurement voltage VC2).

[0276] The first injective and monotone function is defined as:

[0277] - being bounded in a first voltage interval by a first minimum terminal and a first maximum terminal; the first minimum terminal (respectively the first maximum terminal) being representative of an impedance module value equal to zero (respectively tending towards infinity); and

[0278] - having a slope around a first reference voltage value representative of the reference module Mref (i.e. representative of a module equal to 50 Ohms).

[0279] The second injective and monotonic function is defined as:

[0280] - being bounded in a second voltage interval by a second minimum terminal and a second maximum terminal; the second minimum terminal (respectively the second maximum terminal) being representative of a value of the imaginary part of impedance tending towards minus infinity (respectively towards infinity; and

[0281] - having a slope around a second reference voltage value representative of the imaginary part of reference Mref (i.e. a zero imaginary part).

[0282] In the embodiment of the invention, presented:

[0283] - the first minimum terminal and the first maximum terminal are respectively equal to -0.2 Volts and 0.2 Volts;

[0284] - the second minimum terminal and the second maximum terminal are respectively equal to -0.2 Volts and 0.2 Volts; and

[0285] - the first reference voltage value, respectively the second reference voltage value, is equal to the average value of the first voltage interval, respectively the second voltage interval. In other words, both reference voltage values ​​are equal to zero.

[0286] Once the control unit 10 has converted the modulus MZ1 of the first impedance ZI and the imaginary part lmZ2 of the second impedance Z2 converted into the first and second measurement voltages VC1, VC2, it transmits the two control voltages VC1, VC2 in a control order CO to the impedance matching network 4 during a transmission E32.

[0287] The control order is received by a distributor 19 included in the impedance matching network 4 which has the function, during a distribution E33, of transmitting the first measurement voltage VC1 to an input of the first upstream comparator CFI of the first control branch, and the second measurement voltage VC2 to an input of the second upstream comparator CF2 of the second control branch.

[0288] In an alternative embodiment of the invention, the impedance matching network 4 does not contain a distributor 19: the control unit 10 directly transmits the control voltages VC1, VC2 to the inputs of the upstream comparators CFI, CF2.

[0289] During a first upstream comparison E341, the first upstream comparator CFI compares the first measurement voltage VC1 with a first setpoint voltage VCF1 representative of the module Mref of the reference impedance Zref. In the embodiment of the invention, the first setpoint voltage VCF1 corresponds to the first reference voltage value. In other words, the first setpoint voltage VCF1 is equal to zero. The first upstream comparator CFI then generates at its output a first upstream shaped voltage difference dvfl corresponding to a difference between the first measurement voltage VC1 and the first setpoint voltage VCF1, which it sends to the input of the first upstream corrector RFI. This first upstream shaped voltage difference dvfl is therefore representative of a difference in module value between the module MZ1 of the first impedance and the reference module Mref.

[0290] Similarly, during a second upstream comparison E342 taking place in parallel with the first upstream comparison E341, the second upstream comparator CF2 compares the second measurement voltage VC2 with a second reference voltage VCF2 representative of the imaginary reference part Imref of the reference impedance Zref. In the embodiment of the invention, the second reference voltage VCF2 corresponds to the second reference voltage value. In other words, the second reference voltage VCF2 is equal to zero. The second upstream comparator CF2 then generates at its output a second upstream shaped voltage difference dvf2 corresponding to a difference between the second measurement voltage VC2 and the first second reference voltage VCF2, which it sends to the input of the second upstream corrector RF2.This second upstream conformal voltage difference dvf2 is therefore representative of a difference in the value of the imaginary part between the imaginary part lmZ2 of the second impedance Z2 and the reference imaginary part Imref.

[0291] Once the first upstream shaped voltage deviation dvfl and the second upstream shaped voltage deviation dvf2 have been received respectively, the first upstream corrector RFI and the second upstream corrector RF2 generate a third measurement voltage VC3 and a fourth measurement voltage VC4 during a first upstream correction E351 and a second upstream correction E352. The second upstream correction E352 is implemented in parallel with the first upstream correction E351.

[0292] The first upstream corrector RFI then transmits the third measurement voltage VC3 to the input of a first downstream comparator CB1, and the second upstream corrector RF2 then transmits the fourth measurement voltage VC4 to the input of a first downstream comparator CB2.

[0293] In one embodiment of the invention, the first and second upstream correctors RFI, RF2 each comprise a voltage shifter for adapting the voltage levels of the third measurement voltage VC3 and the fourth measurement voltage VC4 so that they are included in the operating voltage range of the first and second actuators A1, A2.

[0294] Following receipt of the third and fourth control voltages VC3, VC4, a first downstream comparison E361 and a second downstream comparison E362 are implemented in parallel and respectively.

[0295] The first downstream comparator CB1 (respectively the second downstream comparator CB2) compares the third measurement voltage VC3 (respectively the fourth measurement voltage VC4) with the first voltage position measurement VCB1 (respectively the second voltage position measurement VCB2). The first downstream comparator CB1 (respectively the second downstream comparator CB2) then generates a first downstream shaped voltage difference dvbl (respectively a second downstream shaped voltage difference dvb2).

[0296] The generated downstream conformal voltage deviations dvbl are representative of the voltage difference necessary to apply to the actuators A1, A2 so that they adjust the values ​​of the variable components XI, X2 by changing them from their current value to new values ​​making it possible to obtain a module and an imaginary part of impedance which correspond to the reference module Mref and to the reference imaginary part Imref.

[0297] The adaptation phase continues with the implementation of downstream corrections E371, E372 and adjustments E381, E382 as described previously.

[0298] Finally, following the settings E381, E382, the new values / positions of the variable components XI, X2 allow the adaptation of the radiofrequency application chain over its entire chain length dL.

[0299] In an alternative embodiment of the invention, it is possible to artificially increase the slopes around the reference voltage values ​​of the injective and monotonic functions, even if it means saturating their minimum and maximum limits in order to improve the response time of the control of the two control branches. For each of the two control branches, the response time corresponds to the overall time required to successively implement all the following sub-steps:

[0300] - the upstream comparison E341, E342;

[0301] - upstream correction E351, E352;

[0302] - the downstream comparison E361, E362;

[0303] - downstream correction E371, E372; and

[0304] - setting E381, E382. However, the improvement in response time comes at the expense of increased sensitivity.

Claims

CLAIMS 1. Impedance matching method (P) for impedance matching of a radiofrequency application chain comprising at least: - a radiofrequency generator (2) generating an electromagnetic wave and having a reference impedance (Zref) defined at least by an imaginary reference part (Imref), and a reference module (Mref), - a transmission line (3) which is positioned at the output of the radiofrequency generator (2) and which has a characteristic line impedance adapted to the reference impedance (Zref), - a functional block (6) positioned at the output of the transmission line (3) and which comprises an impedance matching network (4) and a load (5) positioned at the output of the impedance matching network (4), in which the impedance matching network (4) has two degrees of freedom by comprising a first variable component (XI) and a second variable component (X2), - a radiofrequency discriminator (1) positioned at a fixed position (pO), distant from the functional block (6) by a fixed discriminator distance (dO), between the output of the radiofrequency generator (2) and the input of the transmission line (3), and - a control unit (10) connected on the one hand to the radiofrequency discriminator (1), and on the other hand to the impedance matching network (4) with two degrees of freedom which it controls by transmitting a control order (CO) to it; which impedance matching method (P) firstly implements a determination phase (DP) which is automated and during which a module (M_SllpO) and a phase (P_SllpO) of a reflection coefficient (SllpO) at the fixed position (pO) are numerically determined, from at least one measurement carried out by the radiofrequency discriminator (1); then subsequently implements an identification phase (IP) comprising: - a first identification step (El) during which a first position of interest (pl) is digitally identified, distant from the functional block (6) by a first distance of interest (dl), such that at said first position of interest (pl), a modulus (MZ1) of a first impedance (Zl), seen at the first position of interest (pl), varies only as a function of a value of the first variable component (XI) around the reference impedance (Zref), said first impedance (Zl) being calculated digitally from at least the modulus (M_SllpO) and the phase (P_SllpO) of the reflection coefficient (SllpO) at the fixed position (pO), and - a second identification step (E2) during which the digital identification is carried out a second position of interest (p2) distant from the functional block (6) by a second distance of interest (d2) such that at said second position of interest (p2), an imaginary part (lmZ2) of a second impedance (Z2), seen at the second position of interest (p2), varies only as a function of a value of the second variable component (X2) around the reference impedance (Zref), said second impedance (Z2) being calculated numerically from at least the modulus (M_SllpO) and the phase (P_SllpO) of the reflection coefficient (SllpO) at the fixed position (pO);and finally said impedance matching method (P) implements an adaptation phase (AP) which is automated and during which the value of the first variable component (XI) is physically adjusted so that the modulus (MZ1) of the first impedance (Zl) is equal to the reference modulus (Mref), and the value of the second variable component (X2) is physically adjusted so that the imaginary part (lmZ2) of the second impedance (Z2) is equal to the reference imaginary part (Imref).; 2. Impedance matching method (P) according to claim 1, in which the determination phase (DP) comprises at least: - a measurement step (E01) during which the radiofrequency discriminator (4) physically measures at least one direct voltage (Vd) and one reflected voltage (Vr), - a calculation step (E02) during which the modulus (M_SllpO) and the phase (P_SllpO) of the reflection coefficient (SllpO) at the fixed position (pO) are calculated at least from a ratio of the reflected voltage (Vr) to the direct voltage (Vd).

3. Impedance matching method (P) according to claim 2, wherein during the measuring step (E01) a delayed reflected voltage (Vr_d) is also measured which is delayed by a given delay (dly) with respect to the direct voltage (Vd), and during the calculating step (E02) are calculated: - the modulus (M_SllpO) of the reflection coefficient (SllpO) at the fixed position (pO) from a modulus of the ratio of the reflected voltage (Vr) to the direct voltage (Vd), - a cosine of the phase (P_SllpO) of the reflection coefficient (SllpO) at the fixed position (pO) from at least one argument of the ratio of the reflected voltage (Vr) to the direct voltage (Vd), - a sine of the phase (P_SllpO) from at least one argument of the ratio of the delayed reflected voltage (Vr_d) to the direct voltage (Vd), - the phase (P_SllpO) of the reflection coefficient (SllpO) at the fixed position (pO) which is equal to a cotangent of a ratio of the cosine of the phase (P_SllpO) to the sine of the phase (P_SllpO).

4. Impedance matching method (P) according to claim 3, wherein the delay (dly) defining the delayed reflected voltage (Vr_d) is equal to 90°, to within plus or minus 15 degrees.

5. Impedance matching method (P) according to any one of the preceding claims, wherein, during the first identification step (El) and the second identification step (E2), the first impedance (Zl) and the second impedance (Z2) are calculated as a function of a wave vector (k) characteristic of the electromagnetic wave generated by the radiofrequency generator (2).

6. Impedance matching method (P) according to claim 5, wherein the first identification step (El) comprises the following sub-steps: - a sub-step of selection (Eli) of a first test point (ptl) which is distant from the functional block (6) by a first test distance (dtl), - a sub-step of calculating (E12) a reflection coefficient (Sllptl) at the first test point (ptl) from the reflection coefficient (SllpO) at the fixed position (pO), the first test distance (dtl) and the wave vector (k), - a sub-step of calculating (E13) an impedance (Zptl) at the first test point (ptl) from the reflection coefficient (Sllptl) at the first test point (ptl), - a sub-step of determining (E14) a module (Mptl) of the impedance (Zptl) at the first test point (ptl); - a test sub-step (E15) during which monitoring of the modulus (Mptl) of the impedance (Zptl) at the first test point (ptl) is implemented by varying the value of the first variable component (XI) and the value of the second variable component (X2), in order to test the dependence of the modulus of the impedance (Zptl) at the first test point (ptl) as a function of these two values; and if the modulus (Mptl) of the impedance (Zptl) at the first test point (ptl) varies only as a function of the value of the first variable component (XI), then the first distance of interest (dl) corresponds to the first test distance (dtl); otherwise the first test distance (dtl) is modified and the first identification step (El) is repeated.

7. Impedance matching method (P) according to claim 5 or 6, wherein the second identification step (E2) comprises the following sub-steps: - a sub-step of selection (E21) of a second test point (pt2) which is distant from the functional block (6) by a second test distance (dt2), - a sub-step of calculating (E22) a reflection coefficient (Sllpt2) at the second test point (pt2) from the reflection coefficient (SllpO) at the fixed position (pO), the second test distance (dt2) and the wave vector (k), - a sub-step of calculating (E23) an impedance (Zpt2) at the second test point (pt2) from the reflection coefficient (Sllpt2) at the second test point (pt2), - a step of determining (E24) an imaginary part (Impt2) of the impedance (Zpt2) at the second test point (pt2); - a test sub-step (E25) during which monitoring of the imaginary part (Impt2) of the impedance (Zpt2) at the second test point (pt2) is implemented by varying the value of the first variable component (XI) and the value of the second variable component (X2), in order to test the dependence of the imaginary part (Impt2) of the impedance (Zpt2) at the second test point (pt2) as a function of these two values; and if the imaginary part (Impt2) of the impedance (Zpt2) at the second test point (pt2) varies only as a function of the value of the second variable component (X2), then the second distance of interest (d2) corresponds to the second test distance (dt2); otherwise the second test distance (dt2) is modified and the second identification step (E2) is repeated.

8. Impedance matching method (P) according to any one of the preceding claims, wherein at least the matching phase (AP) is carried out by means of a servo system included in the impedance matching network (4) and at least in communication with the control unit (10); said servo system comprising at least: - a first upstream comparator (CFI), a first upstream corrector (RFI), a first downstream comparator (CB1), a first downstream corrector (RB1), and a first actuator (Al), - a second upstream comparator (CF2), a second upstream corrector (RF2), a second downstream comparator (CB2), a second downstream corrector (RB2), and a second actuator (A2), with: - the first upstream corrector (RFI) connected in series at the output of the first upstream comparator (CB1), and the second upstream corrector (RF2) connected in series at the output of the second upstream comparator (CB2); - the first downstream corrector (RB1) connected in series at the output of the first downstream comparator (CB1), and the second downstream corrector (RB2) connected in series at the output of the second comparator downstream (CB2); - the first actuator (Al) connected in series at the output of the first downstream comparator (RBI) and connected to the first variable component (XI), and the second actuator (A2) connected in series at the output of the second downstream comparator (RB2) and connected to the second variable component (X2); and - the first downstream comparator (CB1) having at least a first input and a second input such that the first input is connected to the output of the first upstream corrector (RFI); the second downstream comparator (CB2) having at least a first input and a second input such that the first input is connected to the output of the second upstream corrector (RF2).

9. Impedance matching method (P) according to claim 8, wherein the impedance matching method (P) comprises: - a first downstream correction (E371) during which the first downstream corrector (RB1) generates a first adjustment voltage (Vtunel) from a first downstream shaped voltage difference (dvbl) coming from the first downstream comparator (CB1); - a second downstream correction (E372) carried out in parallel with the first downstream correction (E371) during which the second downstream corrector (RB2) generates a second adjustment voltage (Vtune2) from a second downstream shaped voltage difference (dvb2) coming from the second downstream comparator (CB2); - a first adjustment (E381) during which the first actuator (Al) varies the value of the first variable component (XI) from a current value to a new value as a function of the first adjustment voltage (Vtunel); - a second adjustment (E382) carried out in parallel with the first adjustment (E381) during which the second actuator (A2) varies the value of the second variable component (X2) from a current value to a new value as a function of the second adjustment voltage (Vtune2).

10. Impedance matching method (P) according to claims 6 to 9, wherein the test sub-steps (E15, E25) of the first identification step (El) and of the second identification step (E2) each comprise at least: - a transmission (Tl) during which a first control voltage (Vpl) and a second control voltage (Vp2) are transmitted to the servo system; - a distribution (T2) such that once the first control voltage (Vpl) and the second control voltage (Vp2) have been received by the servo system, the first control voltage (Vpl) is sent to the input of the first downstream comparator (CB1), and the second control voltage (Vp2) is sent to the input of the second downstream comparator (CF2); - a first downstream comparison (T31) during which the first downstream comparator (CB1) compares the first control voltage (Vpl) with a first voltage position measurement (VCBl) representative of the current value of the first variable component (XI), and generates the first downstream shaped voltage difference (dvbl) corresponding to a difference between the first control voltage (Vpl) and the first voltage position measurement (VCBl); - a second downstream comparison (T32) carried out in parallel with the first downstream comparison (T31) during which the second downstream comparator (CB2) compares the second control voltage (Vp2) with a second voltage position measurement (VCB2) representative of the current value of the second variable component (X2), and generates the second downstream shaped voltage difference (dvb2) corresponding to a difference between the second control voltage (Vpt2) and the second voltage position measurement (VCB2); - the first downstream correction (E371) and the second downstream correction (E372), based respectively on said first downstream shaped voltage difference (dvbl) and on said second downstream shaped voltage difference (dvb2) resulting respectively from the first downstream comparison (T31) and the second downstream comparison (T32); - the first setting (E381) and the second setting (E382) for which, respectively, the first actuator (Al) varies the value of the first variable component (XI) from its current value to the new value as a function of the first setting voltage (Vtunel), and the second actuator (A2) varies the value of the second variable component (X2) from its current value to the new value as a function of the second setting voltage (Vtune2).

11. Dependency adaptation method (P) according to claim 9 or 10, in which the adaptation phase (AP) comprises at least: - a conversion (E31) during which the control unit (10) converts: the module (MZ1) of the first impedance (Zl) at the first distance of interest (dl) into a first measurement voltage (VC1) representative of said module (MZ1), and the imaginary part (lmZ2) of the second impedance (Z2) at the second distance of interest (d2) into a second measurement voltage (VC2) representative of said imaginary part (lmZ2); - a transmission (E32) during which the control unit (10) sends to the servo system the control order (CO) which includes the first measurement voltage (VC1) and the second measurement voltage (VC2); - a distribution (E33) such that once the control order (CO) is received by the system control, the first measurement voltage (VC1) is sent to the input of the first upstream comparator (CFI), and the second measurement voltage (VC2) is sent to the input of the second upstream comparator (CF2); - a first upstream comparison (E341) during which the first upstream comparator (CFI) compares the first measurement voltage (VC1) with a first setpoint voltage (VCF1) representative of the reference module (Mref), and generates a first upstream shaped voltage difference (dvfl) corresponding to a difference between the first measurement voltage (VC1) and the first setpoint voltage (VCF1); - a second upstream comparison (E342) carried out in parallel with the first upstream comparison (E341) during which the second upstream comparator (CF2) compares the second measurement voltage (VC2) with a second reference voltage (VCF2) representative of the imaginary reference part (Imref), and generates a second upstream voltage difference (dvf2) corresponding to a difference between the second measurement voltage (VC2) and the second reference voltage (VCF2); - a first upstream correction (E351) during which the first upstream corrector (RFI) generates a third measurement voltage (VC3) from the first upstream voltage difference (dvfl); - a second upstream correction (E352) carried out in parallel with the first upstream correction (E351) during which the second upstream corrector (RF2) generates a fourth measurement voltage (VC4) from the second upstream voltage difference (dvf2); - a first downstream comparison (E361) during which the first downstream comparator (CB1) compares the third measurement voltage (VC3) with a first voltage position measurement (VCB1) representative of a current value of the first variable component (XI), and generates the first downstream voltage difference (dvbl) corresponding to a difference between the third measurement voltage (VC3) and the first voltage position measurement (VCB1); - a second downstream comparison (E362) carried out in parallel with the first downstream comparison (E361) during which the second downstream comparator (CB2) compares the fourth measurement voltage (VC4) with a second voltage position measurement (VCB2) representative of a current value of the second variable component (X2), and generates the second downstream voltage difference (dvb2) corresponding to a difference between the fourth measurement voltage (VC4) and the second voltage position measurement (VCB2); - the first downstream correction (E371) and the second downstream correction (E372), based respectively on said first downstream shaped voltage difference (dvbl) and on said second downstream shaped voltage difference (dvb2) resulting respectively from the first downstream comparison (E361) and the second downstream comparison (E362); - the first setting (E381) and the second setting (E382), for which, respectively, the first actuator (Al) varies the value of the first variable component (XI) from its current value to the new value as a function of the first setting voltage (Vtunel), and the second actuator (A2) varies the value of the second variable component (X2) from its current value to the new value as a function of the second setting voltage (Vtune2).

12. Impedance matching method (P) according to claim 11, in which, during the conversion (E31): - the modulus (MZ1) of the first impedance (Zl) is converted into the first measurement voltage (VC1) by means of a first injective and monotonic function having a slope around a first reference voltage value representative of the reference modulus (Mref), and - the imaginary part (I mZ2) of the second impedance (Z2) is converted into the second measurement voltage (VC2) by means of a second injective and monotonic function having a slope around a second reference voltage value representative of the imaginary reference part (Imref).

13. Impedance matching method (P) according to claim 12, in which: - the first injective and monotonic function is defined in a first voltage interval by being bounded by a first minimum bound and a first maximum bound; the first minimum bound being representative of an impedance module value equal to zero, and the first maximum bound being representative of an impedance module value tending towards infinity; and - the second injective and monotonic function is defined in a second voltage interval by being bounded by a second minimum bound and a second maximum bound; the second minimum bound being representative of a value of the imaginary part of impedance tending towards minus infinity, and the second maximum bound being representative of a value of the imaginary part of impedance tending towards plus infinity.

14. Adaptation method (P) according to claim 13, wherein the first reference voltage value corresponds to an average value of the first voltage interval, and the second reference voltage value corresponds to an average value of the second voltage interval.

15. Impedance matching method (P) according to claim 13 and 14, wherein: - the first minimum terminal and the first maximum terminal are respectively equal to -0.2 Volts and 0.2 Volts, with the first reference voltage value equal to zero; and - the second minimum terminal and the second maximum terminal are respectively equal to -0.2 Volts and 0.2 Volts, with the second reference voltage value equal to zero.

16. Method according to any one of claims 12 to 15, wherein the first setpoint voltage (VCF1) is equal to the first reference voltage value, and the second setpoint voltage (VCF2) is equal to the second reference voltage value.

17. Impedance matching method (P) according to any one of the preceding claims, wherein the reference impedance (Zref) is equal to 50 Ohms, that is to say: that the reference modulus (Mref) of the reference impedance (Zref) is equal to 50 Ohms; and that the reference imaginary part (Imref) of the reference impedance (Zref) is zero.

18. Impedance matching method (P) according to any one of the preceding claims, in which the first variable component (XI) and the second variable component (X2): - each correspond either to a variable capacitor or to a variable inductance; and - are either in series with the transmission line (3) or in parallel with it.

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