Patent Publication Number: US-2023161980-A1

Title: Method and system for detecting receivers, and adjustable receiver

Description:
TECHNICAL FIELD 
     This invention relates to a receiver detection method and to a system which enables implementing the method, as well as to an adjustable receiver. 
     STATE OF THE PRIOR ART 
     Items available for purchase may be provided with labels or badges equipped with RFID technology, for example in order to reduce checkout time. The items are placed in a tray in front or to the side of the cash register, and the system identifies the items by means of the RFID tags and issues the receipt automatically, without the cashier needing to scan each item individually. Time is therefore saved. 
     However, some items may not be detected by the system, which can lead to checkout errors. 
     When multiple receivers (or badges) are placed next to each other, as in the case of a cash register tray, they may be difficult to read, in particular because of interference and/or electromagnetic field minimas. These interferences are due both to the environment, which can scatter, reflect, and/or diffract the waves, but also to the receivers themselves, which, because they are also scatterers, can reflect, scatter, diffract, even attenuate the waves. 
     There may also be problems with detection of the receivers when they send simultaneous responses. 
     STATEMENT OF DISCLOSURE 
     This disclosure is intended to improve badge detection within a volume. 
     To this end, a method is provided for detecting receivers, implemented by a detection system comprising a general antenna suitable for emitting a primary wave, and a general controller connected to the general antenna, the system comprising an adjustable receiver having a receiver antenna suitable for receiving the primary wave and for emitting a secondary wave, the adjustable receiver having a receiver controller connected to the receiver antenna, the receiver controller being suitable for detecting the primary wave received by the receiver antenna and for commanding the emission of the secondary wave by the receiver antenna, the adjustable receiver having a modifiable impedance thus influencing the secondary wave emitted, the adjustable receiver initially being in a detection mode where the adjustable receiver has a base impedance, the method comprising:
     a receiver detection step in which the adjustable receiver is detected by the general controller when the general antenna receives the secondary wave emitted by the adjustable receiver, followed by   a reconfiguration step in which the general controller commands the receiver controller to switch to an interaction mode where the impedance of the adjustable receiver is alternated between a first configuration impedance and a second configuration impedance in order to detect other receivers, the reconfiguration step being of a duration that is an order of magnitude higher than the duration of each alternation of the first and second configuration impedances.   

     By means of the above arrangements, the number of adjustable receivers made available to the general controller for the detection of new receivers increases as they are detected. Each time a receiver is detected, its impedance is adjusted by the general controller to a mode suitable for the detection of other receivers. The system is then able to more effectively detect the presence of one or more receivers not yet detected, regardless of the position of said receivers and whether they are fixed or mobile. 
     In various embodiments of the system, use may be made of one or more of the following arrangements:
     the base impedance is imposed by the receiver controller independently of the general controller.   the first configuration impedance is the base impedance.   the first configuration impedance is at a distance from the second configuration impedance.   the first configuration impedance and the second configuration impedance are close to and with one on either side of the base impedance within the complex plane.   the adjustable receiver is a first adjustable receiver, the receiver antenna is a first receiver antenna, the primary wave is a first primary wave, the secondary wave is a first secondary wave, the receiver controller is a first receiver controller, the base impedance is a first base impedance, the configuration impedance is a first configuration impedance, and the system contains a second adjustable receiver, the second adjustable receiver having a second receiver antenna suitable for receiving the primary wave and emitting a second secondary wave and a second receiver controller connected to the second receiver antenna, the second receiver controller being suitable for controlling the emission of the second secondary wave by the second receiver antenna and for detecting the primary wave received by the second receiver antenna, the second adjustable receiver having a modifiable impedance thus influencing the second secondary wave emitted by the second receiver antenna, the second adjustable receiver initially being in detection mode where the second adjustable receiver has a second base impedance,   the method further comprising a reconfiguration step of reconfiguring the second receiver in which, when the general antenna receives the second secondary wave emitted by the second adjustable receiver and the controller detects the second adjustable receiver, the general controller commands the second adjustable receiver to switch to interaction mode where the impedance of the second adjustable receiver alternates between a first configuration impedance of the second receiver and a second configuration impedance of the second receiver in order to detect other receivers, the reconfiguration step of reconfiguring the second adjustable receiver being of a duration that is an order of magnitude higher than the duration of each alternation of the first and second configuration impedances of the second receiver.   the first configuration impedance of the second receiver is the second base impedance of the second receiver.   the first configuration impedance of the second receiver is at a distance from the second configuration impedance of the second receiver.   the first configuration impedance of the second receiver and the second configuration impedance of the second receiver are close to and with one on either side of the base impedance within the complex plane.   the alternations of the configuration impedances of the second receiver in interaction mode are determined by an optimization algorithm, or by a predefined series of impedance values.   the alternations of the configuration impedances of the second receiver in interaction mode are carried out at irregular non-periodic time instants.   the general controller determines the alternations of the configuration impedances of the second receiver in interaction mode.   the general controller commands the switch to interaction mode of the identified receivers, and the controllers of these identified adjustable receivers determine the alternations of the configuration impedances when they are in interaction mode.   in interaction mode, the impedance of the adjustable receiver alternates between a plurality of configuration impedances.   the adjustable receiver includes a plurality of adjustable components and associated antennas, and: the general controller commands the emission by the general antenna of a general control wave containing identification information along with an associated adjustment parameter to designate each adjustable component for which said adjustment parameter is intended, and said adjustable component controls the impedance of the associated antenna in relation to the adjustment parameter if the identification information is equal to its adjustable component identifier.   the system further comprises an adjustable element connected to the general antenna, and in the receiver detection step the general controller also modifies the impedance of the adjustable element.   the general controller simultaneously modifies the impedance of the adjustable element and the impedance of the identified adjustable receiver, according to values determined by an optimization algorithm.   

     Also provided is a receiver detection system, comprising:
         an adjustable receiver,   a general antenna suitable for emitting a primary wave, and for receiving a secondary wave emitted by the adjustable receiver in response to reception of the primary wave,   a general controller connected to the general antenna, the general controller being suitable for commanding the emission of the primary wave and for detecting the adjustable receiver by means of the secondary wave received by the general antenna, characterized in that the adjustable receiver further comprises:   a receiver antenna suitable for emitting the secondary wave;   a receiver controller connected to the receiver antenna, the receiver controller being suitable for commanding the emission of the secondary wave by the receiver antenna and for detecting the primary wave received by the receiver antenna,       the adjustable receiver having a modifiable impedance in order to modify the manner in which the primary wave is reflected and/or transmitted by the receiver antenna as a secondary wave,   the system being configured such that, when the adjustable receiver is detected by the general controller, the general controller commands the receiver controller to switch from a detection mode to an interaction mode,   in detection mode, the adjustable receiver has a base impedance,   in interaction mode, the impedance of the adjustable receiver is alternated between a first configuration impedance and a second configuration impedance in order to detect other receivers, the interaction mode being of a duration that is an order of magnitude higher than the duration of each alternation of the first and second configuration impedances.   

     In various embodiments of the system, use may be made of one or more of the following arrangements:
     the first configuration impedance is the base impedance.   the first configuration impedance is at a distance from the second configuration impedance.   the alternations of the configuration impedances in interaction mode are determined by an optimization algorithm or by a predefined series of impedance values.   the alternations of the configuration impedances in interaction mode are carried out at irregular non-periodic time instants.   the general controller is suitable for commanding the alternations of the configuration impedances in interaction mode of the adjustable receiver.   the general controller is suitable for commanding the switch to interaction mode of the identified adjustable receivers, and the controller of the identified adjustable receiver is suitable for commanding the alternations of the configuration impedance when it is in interaction mode.   

     Also provided is an adjustable receiver comprising:
     an antenna suitable for emitting a secondary wave in response to receiving a primary wave and for receiving a general control wave; and   a controller connected to the antenna, the controller being suitable for commanding the emission of the secondary wave and for detecting the primary wave received and the general control wave,   the adjustable receiver having a modifiable impedance thus influencing the secondary wave emitted, the adjustable receiver having a detection mode and an interaction mode, the adjustable receiver switching from detection mode to interaction mode according to the general control wave received,   in detection mode, the adjustable receiver has a base impedance, and   in interaction mode, the impedance of the adjustable receiver is adapted to alternate between a first configuration impedance and a second configuration impedance in order to detect other receivers, the interaction mode being of a duration that is an order of magnitude higher than the duration of each alternation of the first and second configuration impedances.   

    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Other features and advantages of this disclosure will become apparent from the following description of one of its embodiments, given by way of non-limiting example, with reference to the appended drawings. 
       In the drawings: 
         FIG.  1    is a general diagram of one embodiment of a receiver detection system; 
         FIG.  2    illustrates an example of an adjustable receiver for the system of  FIG.  1   ; 
         FIG.  3    illustrates an alternation over time of the impedance for an adjustable receiver of  FIG.  2   ; and 
         FIG.  4    illustrates a dynamic list used by an algorithm that can be used by the system of  FIG.  1   . 
     
    
    
     In the various figures, the same reference numerals designate identical or similar elements. 
     DETAILED DESCRIPTION 
     System 
       FIG.  1    is a schematic perspective view of one embodiment of a receiver detection system  10 . In this example, the system  10  comprises a container C having a volume V. The container C may be optional, and the volume V defined without physical walls. The container C is suitable for containing within its volume V one, two, or a plurality of receivers. Among these receivers, one or more may be adjustable receivers  30  which, once detected, can be controlled to participate in the detection of other receivers possibly contained within the volume V. The adjustable receivers may comprise in particular a first adjustable receiver  30   a  and a second adjustable receiver  30   b . The adjustable receivers  30  may be static or mobile. An identification or a simple communication in itself also corresponds to a detection. The system  10  is thus a system for receiver detection and/or receiver identification and/or communication with a receiver. According to one example, the adjustable receiver(s)  30  is attached to merchandise (e.g. items for sale), and the container C is a tray of a store checkout register. Thus, simply by placing the items in the tray, the register can identify the items without scanning them one by one. Other applications are described in this disclosure. 
     As will be described below, the adjustable receivers identified contribute, as they are identified, to the identification of other receivers present within the volume V. Although only two adjustable receivers  30   a ,  30   b  are illustrated in the figures, the system  10  could have three or more receivers similar to adjustable receivers  30   a ,  30   b . It could be that some of the receivers, among those identified, are not receivers whose impedance is adjustable. 
     In the particular case of  FIG.  1   , the container C is a parallelepiped comprising a bottom face C 1 , four side faces C 2 , C 3 , C 4 , C 5 , and an open face C 6  in opposition to the bottom face C 1 . Adjustable receivers  30  such as the first adjustable receiver  30   a  and the second adjustable receiver  30   b  can be inserted into and/or removed from the volume through the opening face C 6 . These adjustable receivers  30  may also be moved about within the volume V. The first adjustable receiver  30   a  and the second adjustable receiver  30   b  are generally identical and will be described in detail below with reference to a generic receiver  30 . 
     The system  10  further comprises:
         a general antenna  42  suitable for emitting a primary wave OP into the volume V, and suitable for receiving a secondary wave OS respectively emitted by each adjustable receiver  30  positioned in the volume V in response to the reception by this receiver of the primary wave OP, and   a general controller  41  connected to the general antenna  42 , the general controller  41  being suitable for commanding the emission of the primary wave OP and for identifying the adjustable receiver(s)  30  by the corresponding secondary wave OS emitted by the adjustable receiver(s)  30  and received by the general antenna  42 . The general controller  41  and the general antenna  42  are shown in the figures according to one embodiment as being arranged outside the volume V. Alternatively, the general controller  41  and the general antenna  42  could one or both be arranged inside the volume V.       

     Adjustable Receiver 
     One of the adjustable receivers  30  is schematically illustrated in  FIG.  2   . The first adjustable receiver  30   a  and the second adjustable receiver  30   b  being similar to the generic adjustable receiver  30 , the description of the structure and the mode of operation of the adjustable receiver  30  will serve as a description for the first adjustable receiver  30   a  and the second adjustable receiver  30   b , bearing in mind that the common elements will be denoted with the index “a” for the first adjustable receiver  30   a  and with the index “b” for the second adjustable receiver  30   b.    
     The adjustable receiver  30  comprises an antenna  32  suitable for emitting the secondary wave OS in response to reception of the primary wave OP emitted by the general antenna  42 . The adjustable receiver  30  also comprises a controller  31  connected to the antenna  32  and an adjustable component  35  connected to the controller  31  on the one hand and to the antenna  32  on the other hand. The controller  31  is configured to command the emission of the secondary wave OS, and to detect the primary wave OP received and to decode the information contained therein. The controller  31  also controls the impedance of the adjustable component  35 , which influences the secondary wave OS emitted by the antenna  32 . The adjustable component  35  may be connected to the controller  31  in a wired or wireless manner. A local control wave OC 1  may be sent from the controller  31  to the adjustable component  35  in order to transmit the adjustment parameters to the adjustable component  35 . 
     Each adjustable component  35  has an associated antenna. This antenna may be the antenna  32  of the adjustable receiver  30  or a separate antenna. 
     According to one embodiment, at least one of the adjustable receivers  30  comprises a plurality of adjustable components  35 . The adjustable receiver  30  could comprise several adjustable components  35 , each component having an associated antenna. In another embodiment, the adjustable receiver  30  comprises a single antenna for the plurality of adjustable components  35  of this receiver. The adjustable receiver  30  may comprise one or more controllers  31  for controlling the whole. For simplicity, as an example this description will describe adjustable receivers each having one antenna, one controller, and one adjustable component, it being understood that there could be several antennas and/or several adjustable components and/or several controllers per adjustable receiver. 
     General Structure 
     The adjustable receiver  30  is for example a device of the technology known as RFID for “radio frequency identification”. 
     The adjustable receiver  30  is for example a connected object, for example of the Internet of Things (IoT) type or of the type with transmission via WiFi or Bluetooth or via a LoRa network. 
     The adjustable receiver  30  could comprise one or more sensors (e.g. temperature, humidity, presence detection, gas detection, flow rate, voltage, current). One or more of the values measured by a sensor would be stored in a receiver memory or any other memory and could be transmitted to the general controller  41  by means of the secondary wave OS. 
     The controller  31 , the antenna  32 , and the adjustable component  35  of a same receiver  30  may be grouped together on a base  36  so that the receiver  30  forms a compact object. According to one embodiment, the base  36  is for example a label for clothes or supplies that is thin, e.g. less than 0.2 mm in thickness, for example made of a flexible polymer material. The adjustable component  35 , the antenna  32 , and the controller  31  may for example be fixed on the base  36  by adhesion. The adjustable component  35 , the antenna  32 , and the controller  31  of the adjustable receiver  30  are themselves circuits that are thin, such that the adjustable receiver  30  is a thin and flexible device which is associated with an item. 
     Adjustable Components 
     There are several ways to obtain an adjustable receiver  30  of variable impedance. 
     The adjustable component  35  of the adjustable receiver  30  is composed for example of at least one adjustable electronic circuit connected to the antenna  32  in order to modify the impedance of the electromagnetic radiation, which characterizes its interaction with the electromagnetic field and in particular the waves around the receiver. The adjustable electronic circuit(s) is for example a capacitor, a diode, a transistor, or a combination thereof. This adjustable electronic circuit comprises an input that is controllable by the controller  31  so as to modify one of its electronic characteristics, meaning more generally its electrical impedance which is the load impedance of the antenna  32  of the adjustable receiver  30 . This modification involves modifying the radiation impedance of the antenna  32  and the interaction with the waves. 
     The adjustable component  35  is therefore controllable by an input which can be modified for example by a voltage value imposed by the controller  31 , and which corresponds for example to one or more adjustment parameter values. These adjustment parameters may be determined by the general controller  41  or alternatively by the controller  31  of the adjustable receiver, as explained in more detail below. 
     Modifying the impedance of the adjustable receiver  30  modifies the spatial distribution of the primary wave OP within the volume V. This modification may be optimized so as to detect other receivers contained in the volume V and initially not identified by the general controller  41 . In addition, as the detection of receivers in the volume V progresses, these receivers become controlled by the general controller  41  so as to participate in modifying the spatial distribution of the primary wave OP in order to detect more effectively any other receivers present in the volume V. Modifying the impedance of the adjustable receiver  30  is much more complex than spatial directivity or focusing: it involves modifying the electromagnetic field within the volume around the receiver. 
     Modes 
     When the impedance of the adjustable receiver  30  is modified, the manner in which the primary wave OP is reflected and/or transmitted by the adjustable receiver  30  is modified as well, which influences the overall electromagnetic field within the volume V. This modification is used here to detect other receivers invisible to the general controller  41 . Thus, the general controller  41  can command the adjustable receiver  30  to switch to an interaction mode in which the adjustable receiver  30  has changing impedance in order to modify the general electromagnetic field within the volume V. This modification of the electromagnetic field can help detect one or more other receivers previously silent to the general controller  41 . 
     Each adjustable receiver  30  contained in the volume V is initially undetected by the general controller  41  and is in detection mode. In detection mode, the adjustable receiver  30  has a base impedance IB 1 . The base impedance IB 1  is for example a load impedance of the antenna  32  of the adjustable receiver  30 , meaning an impedance adapted for receiving maximum energy. For example, the base impedance IB 1  of an adjustable receiver  30  is 11+143*j (j is the complex for which j{circumflex over ( )}2=−1). According to one embodiment, the base impedance IB 1  of an adjustable receiver  30  is imposed by its controller  31  independently of the general controller  41 . According to another embodiment, the base impedance IB 1  of an adjustable receiver  30  is commanded by the general controller  41 . In detection mode, the adjustable receiver  30  could have several base impedances, and the controller  31  of the adjustable receiver  30  could alternate between these different base impedances. This alternation could take place without the general controller  41  commanding the controller  31  of the adjustable receiver  30 , or alternatively could be under the control of the general controller  41 . 
     When the general antenna  42  receives the secondary wave OSa emitted by a receiver located in the volume V and the receiver is an adjustable receiver  30 , the general controller  41  can command the controller  31  of this adjustable receiver  30  to switch into interaction mode, in order to help identify other receivers contained within the volume. 
     In interaction mode, the impedance of the adjustable receiver  30  is alternated between a first configuration impedance IC 1  and a second configuration impedance IC 2 . For example, the first configuration impedance ICI is IB 1 −20j, and the second configuration impedance IC 2  is IB 1 +20j. The first configuration impedance IC 1  could be infinite and the second configuration impedance IC 2  could be zero or of low modulus or close to zero. It is possible for the impedance of the adjustable element  35  to be alternated between three or more configuration impedances. At least one among the first and second configuration impedances IC 1 , IC 2  could be the base impedance IB in order to be able to recover energy. 
     According to one embodiment, the first configuration impedance ICI is at a distance from the second configuration impedance IC 2 . “At a distance” is understood to mean that there is for example an order of magnitude of at least 10 between them. An impedance is a complex value, so an impedance can be considered to be at a distance from another impedance when for example:
         their moduli have values that are at a distance from each other, for example having a magnitude ratio between them of at least 2, and preferably of at least 10 (as mentioned above), or   their phases have values that are at a distance from each other, such as values differing by at least pi/4, and preferably by more than pi/2, or   the modulus of the difference of the first and second impedance has a high value, for example greater than a threshold value, or for example greater than the modulus of the first impedance and/or greater than the modulus of the second impedance.       

     Many criteria for the distances between impedances can be defined. 
     A small variation in the impedance of the adjustable components allows greatly modifying the radiation impedance of the antenna which functions as a resonator: at the base frequency in particular of this resonator, the amplitude and the phase of the impedance seen by electromagnetic waves will vary greatly via this small change in load impedance. Thus, as the antenna is dispersive, a small modification to its load impedance around its resonant frequency makes it possible to obtain a distanced type of alternation between a first configuration impedance ICI and a second configuration impedance IC 2 . In addition, this type of resonator is fairly easy to implement in an adjustable receiver  30  that is small in size and in particular is thin. 
     According to another embodiment, the first configuration impedance ICI and the second configuration impedance IC 2  are close to the base impedance IB. “Close” is understood to mean that there is an order of magnitude of at most  10  between them. An impedance is a complex value, thus an impedance is close to another impedance when their moduli and/or their phases and/or the modulus of their complex difference are close to each other. An advantage of having the first configuration impedance IC 1  and the second configuration impedance IC 2  be close to the base impedance IB is that the adjustable receiver  30  is able to recover energy and remains powered during interaction mode. According to one embodiment, the first configuration impedance IC 1  and the second configuration impedance IC 2  are close to and with one on either side of the base impedance within the complex plane. 
     The first configuration impedance ICI and the second configuration impedance IC 2  could both be higher than the base impedance IB 1 , or both be lower than the base impedance IB 1 , or one could be higher and one lower than the base impedance IB 1 . 
     In interaction mode, there is therefore a fairly frequent alternation between the two or more configuration impedances, in the sense that the duration T 1  of interaction mode is of an order of magnitude higher than the duration T 2 , T 3  of each alternation of the first and second configuration impedances ICI and IC 2 .  FIG.  3    for example illustrates this point. According to one example, the duration T 1  of interaction mode is 100 ms, and the duration T 2 , T 3  of each alternation of the first and second configuration impedances ICI and IC 2  is 10 ms. 
     Exiting Interaction Mode 
     Each adjustable receiver detected and switched into interaction mode by the general controller  41  may remain in interaction mode until all receivers present in the volume V are detected. 
     The adjustable receiver(s)  30  may exit interaction mode after a predetermined period of time which could correspond to the time deemed sufficient for detecting all receivers present in the volume V, for example a few tens or a few hundreds of milliseconds. This period of time could be imposed by the general controller  41  or else could be imposed by the controller  31  of the adjustable receiver  30 . It is possible for this time to be different for each or for some of the receivers contained in the volume V. This time could be random. 
     According to another embodiment, the general controller  41  controls the exiting of the adjustable receivers from interaction mode. The general controller  41  may command all the detected adjustable receivers to exit simultaneously, or may do so by group of receivers. 
     According to another embodiment, the adjustable receiver  30  remains in interaction mode until the energy stored in this adjustable receiver is below a minimum value. 
     Alternation Based on Predefined or Random Sequences 
     According to one embodiment, the general controller  41  periodically defines adjustment parameters for the adjustable components  35  of the receivers  30  that it has detected, randomly or in a predefined manner, in order to sweep through a set of combinations of adjustment parameters, which allows sweeping the volume V of the container with various electromagnetic fields. With each impedance alternation, at the same time the general controller  41  emits a primary wave OP in order to detect receivers with this new setting. Alternatively, the general controller  41  could emit the primary wave OP temporally after sending the impedance adjustment parameters. According to a variant of this embodiment, the general controller  41  only commands the switch of the identified receivers from detection mode to interaction mode, and the controller of each identified adjustable receiver  30  periodically defines adjustment parameters for its adjustable components  35  in a random manner in order to sweep through a set of combinations of the adjustment parameters. 
     According to another embodiment, the timing of the alternations is not periodic but irregular, dictated, or random. 
     According to another embodiment, once an adjustable receiver  30  is detected and is in interaction mode, its controller  31  is passive and the general controller  41  commands the impedance alternations of the adjustable receivers  30  via the controller  31  of the adjustable receiver. 
     According to one embodiment, the general controller  41  commands only the switch of the identified receiver(s) to interaction mode, and the controller(s)  31  of this or these receivers command the impedance alternations of the adjustable receivers  30 . These alternations may be preprogrammed. To this end, each controller  31  of the adjustable receiver  30  may include a memory  33  which would contain programming of the interaction mode impedance sequences to be alternated (possibly with a time delay associated with the sequence or with each alternation, for example alternating after an alternation duration on the order of a few milliseconds to a few hundred milliseconds) when the adjustable receiver  30  is switched to interaction mode by the general controller  41 . 
     Alternation Based on Optimization 
     According to another embodiment, the modification of the electromagnetic field by the adjustable receiver(s)  30  which have been switched to interaction mode may be done so as to optimize this electromagnetic field for detecting other receivers. Optimization makes it possible to use several adjustable receivers  30  (the ones detected) to improve the electromagnetic field within the volume V and thus to detect other receivers which could not be detected before. The general controller  41  monitors the secondary waves OS received by the general antenna  42  (when said waves are received) and originating from the various adjustable receivers  30  detected. Via these waves, the general controller  41  can for example determine reception information concerning the reception of the secondary wave OS received by its general antenna  42 , this reception information being for example the level of reception and/or the quality of reception. 
     The general controller  41  can then use the reception information to estimate a value to be optimized (optimization value), this value being one piece of information or a combination of the pieces of reception information. 
     The general controller  41  executes, for example, an optimization algorithm based on the set of (temporally) previous parameters, previous estimated values, and current estimated value. 
     The optimization algorithm may be a maximization or a minimization of the estimated value, depending on the magnitude represented by this value. In one or more successive steps, the optimization algorithm makes it possible to obtain an optimal set of parameters for detecting a new adjustable receiver  30 . At each step or at predetermined periodicities, the general controller  41  applies the new set of parameters to the adjustable receivers  30  that it has identified and/or determines reception information for performing the next iteration. These iterations may be performed at a very high rate such that the duration of this optimization is very short compared to the number of receivers to be detected and/or identified in the volume. 
     The optimal set of parameters makes it possible, for example, to improve the level of reception of the secondary wave OS at the general antenna  42 . Due to this modification via the optimized state of the adjustable components of the identified receivers, for example such as the first receiver  30 , the propagation field of the secondary wave OS towards the general antenna  42  is improved, and the receiver detection and/or identification, for example of a second receiver  30   b  previously unidentified in the volume V, is improved or even becomes possible. 
     Thus, according to one embodiment, the general controller  41  determines the set of parameters for adjusting the plurality of adjustable components of the receivers identified by the general controller  41 , for example in order to optimize reception of the secondary wave by the general antenna.  42 . The optimization concerns the estimated value, which is for example an estimate of the level of reception and/or of the quality of reception of the secondary wave by the general antenna  42 . 
     Dynamic Optimization 
     The optimization is dynamic, i.e. the number of parameters sent by the general controller  41  to the adjustable receivers  30  in order to adjust the adjustable components  35  increases as new receivers are detected in the volume V. Thus, when a first adjustable receiver  30   a  is detected, the general controller  41  will command the change of impedance of this adjustable receiver, and will then do the same for each new adjustable receiver detected. Thus, after a few iterations, five adjustable receivers  30  for example will be controlled by the general controller  41  so as to detect a new receiver present within the volume V. 
     To illustrate, let us take the example of the first receiver  30   a  and second receiver  30   b  present within the volume V, on the assumption that they are initially not identified by the general controller  41 . The first  30   a  and second  30   b  receivers are initially (t=t 0 ) in detection mode with a respective base impedance IBa, IBb fixed only by their associated controller  31 a,  31 b (independently of the general controller  41 ). In a first step, the receiver detection step, the first receiver  30   a  is detected by the general controller  41  when the general antenna  42  receives the secondary wave OSa emitted by the first receiver  30   a  (time t=t 1 ). The general controller  41  can then add the first receiver  30   a  to a dynamic list L of identified receivers (see  FIG.  4   ). The dynamic list L may be saved in a memory of the general controller  41 . The list is dynamic because it is updated in real time by adding to it the receivers detected by the general controller  41  as they are detected and switched to interaction mode. 
     During a third step, the second receiver detection step, the general antenna  42  receives the secondary wave OSb emitted by the second receiver  30   b . The general controller  41  identifies the second receiver  30   b  and can then add the second receiver  30   b  to its dynamic list L of identified receivers (time t=t 2 ). The general controller  41  further commands the controller  31 b of the second receiver  30   b  to switch to interaction mode in which the impedance of the second adjustable receiver  30   b  alternates at least between a first configuration impedance IClb and a second configuration impedance IC 2 b. 
     According to one embodiment, the first configuration impedance IC 1   b  of the second receiver  30   b  is at a distance from the second configuration impedance IC 2   b  of the second receiver  30   b . “At a distance” is understood to mean that they have for example an order of magnitude of at least 10 between them. Impedance is a complex value, thus an impedance can be considered to be at a distance from another impedance when for example:
         their moduli have values that are at a distance from each other, for example having a magnitude ratio between them of at least 2, and preferably of at least 10 (as mentioned above), or   their phases have values that are at a distance from each other, such as values differing by at least pi/4, and preferably more than pi/2, or   the modulus of the difference of the first and second impedance has a high value, for example greater than a threshold value, or for example greater than the modulus of the first impedance and/or greater than the modulus of the second impedance.       

     Many criteria for distances between impedances can be defined. 
     Optimization with Previously Saved Parameters 
     According to one embodiment, the general controller  41  periodically defines adjustment parameters for the adjustable components of the detected receivers according to a previously saved table in order to sweep through a set of combinations of adjustment parameters. 
     This previously stored table is for example defined by knowing the propagation of the primary waves OP within the volume V, either by simulation or by measurement in the environment of the volume V. The previously stored table is for example defined in order to ensure the ability to sweep the entire volume V with a predetermined spatial precision. 
     Next, the general controller  41  proceeds as before: at each adjustment of the adjustable components of the identified receivers, the general controller  41  also controls the emission of a primary wave OP in order to detect receivers with this new setting. This procedure allows it to detect one or more new receivers (adjustable or not) within the volume V. After a predefined number of combinations, this procedure makes it possible to obtain knowledge of all receivers in the volume V. 
     Alternatively, the general controller  41  periodically carries out a calibration of said previously saved table, for example during a predetermined time (within a time slot and/or on a given day of the week and/or of a month), by searching for the optimum adjustment parameters for some reference adjustable receivers. 
     This other optimization may be based on the secondary wave OS received by the general controller  41 . The general controller  41  determines reception information concerning the reception of the returning secondary wave OS by its antenna (level of reception and/or quality of reception). The general controller  41  then performs an optimization of the set of adjustment parameters for identified adjustable receivers  30 . 
     Following these optimizations of the adjustment parameters for identified adjustable receivers, the general controller  41  deduces the previously saved table by various techniques, such as a parameterization model and/or an interpolation technique. 
     According to a variant of this embodiment, the general controller  41  only commands the switch of the identified adjustable receivers  30  from detection mode to interaction mode, and the controller  31  of each receiver periodically defines adjustment parameters for the adjustable components according to a previously saved table in the memory of the receiver in question in order to sweep through a set of combinations of adjustment parameters. 
     Receiver—Identification 
     In addition, the memory  33  of each receiver  30  may comprise an adjustable receiver identifier IDrr, making it possible to differentiate between receivers (the identifiers are all different). 
     In this case, the general controller  41  may emit, in a general control wave emission OCg, identification information IID with an impedance adjustment parameter, which makes it possible to designate the identified adjustable receiver of the system  10  for which said adjustment parameter is intended. The general controller  41  thus emits for example the entire set of parameters (all adjustment parameters) sequentially, each adjustment parameter being associated with identification information so that the adjustable receiver  30  to which said adjustment parameter is sent is the only one to apply said adjustment parameter in question. 
     In the case where the adjustable receiver  30  includes a plurality of adjustable components with their associated antennas, the general control wave contains identification information with an associated adjustment parameter in order to designate each adjustable component for which said adjustment parameter is intended, and the adjustable component controls the impedance of the associated antenna in relation to the adjustment parameter if the identification information is equal to its adjustable component identifier IDcr. 
     The receiver  30  may thus comprise a receiving device  34  for receiving the general control wave OCg, which decodes an adjustment parameter contained in this general control wave OCg, originating from the general controller  41 . The controller  31  of the adjustable receiver  30  then uses the adjustment parameter to control and modify the impedance of the associated adjustable component  35 . 
     The receiving device  34  of the receiver  30  then decodes the identification information IID and the adjustment parameter, in the general control wave OCg. Next, the adjustable receiver  30  controls its impedance (i.e. the adjustable component  35  controls the impedance of its associated antenna) according to the adjustment parameter if the identification information is equal to its adjustable receiver identifier IDrr. 
     The general controller  41  emits primary waves OP, possibly periodically, within the volume V of the container C in order to detect and identify receivers, and it periodically emits general control waves OCg within the volume V in order to adjust the adjustable receivers  30  which have been detected. Each detected adjustable receiver  30  then selects the adjustment parameter intended for it. 
     Alternatively, the memory  33  of the adjustable receiver(s)  30  stores a set of adjustment parameters (saved beforehand and/or saved by transmission from the controller) and one (or more) reading period associated with these adjustment parameters. This set of adjustment parameters and reading periods are known to the general controller  41 . This arrangement can enable the general controller  41  to avoid systematically sending new adjustment parameters to the adjustable receivers; in other words this reduces the need for transmission. It is possible that this set of adjustment parameters and/or these reading periods are different for each adjustable receiver  30 . 
     According to a first variant of the general controller  41 , the general controller  41  comprises, in its memory  43 , the dynamic list L of identifiers of the adjustable components or of the adjustable receiver if it has only one adjustable component, this list being filled in with the adjustable receiver identifiers IDrr of the system  10  which are identified in order to be able to transmit the identifier of the adjustable component with the adjustment parameter. Each adjustable receiver  30  emits its adjustable receiver identifier IDrr, possibly periodically, via a return wave which may be the secondary wave Osa. The general controller  41  then establishes the list of adjustable receivers  30  identified in the system  10  and updates it each time a new receiver identifier is received. In addition, an adjustable receiver  30  may be removed from the dynamic list or may be deactivated in said list (by an activity flag) if the general controller  41  no longer receives the identifier of the adjustable receiver  30  after a period of time greater than an inactivation duration limit of an adjustable receiver  30 . 
     Thus, by this dynamic operation, the general controller  41  will always use operative or functional adjustable receivers  30 . This dynamic operation also facilitates installation of the system  10 , which automatically adapts to the adjustable receivers  30  present within the volume V. 
     In addition, according to one variant, the adjustable receiver  30  will periodically emit its adjustable identifier IDrr solely in the presence of a primary wave OP and/or of a general control wave OCg originating from the antenna  42  of the controller  41 , in particular:
         either because this adjustable receiver  30  uses an energy recovery device  37  for recovering energy from this wave for its operation. In the absence of energy, the adjustable receiver  30  will be automatically switched off and will not broadcast its identifier;   or because this adjustable receiver  30  is designed not to transmit its identifier if it has not received a primary wave OP or a general control wave OCg for a period of time greater than a predetermined standby time.       

     Receiver—Impedance Alternation Command 
     The impedance alternations in interaction mode of the identified adjustable receivers  30  may be carried out in different ways. According to one embodiment, an optimization algorithm iteratively determines the impedances of each of the adjustable components in the dynamic list L, the aim being to optimize the electromagnetic field in the volume V. Alternatively, the general controller  41  comprises a memory which stores one or more sets of optimal parameters for detecting receivers present in the volume V but which are still unidentified. In this manner, the optimization algorithm can start its process based on one or more of the saved sets of parameters, which allows saving time in the optimization and avoids transient effects. 
     Alternatively, the optimization algorithm monitors its performance and stops its optimization iterations when a stop criterion is reached. The stop criterion may be the reception by the general controller  41  of an identifier of a receiver not yet identified. It is thus possible to avoid insignificant variations or fluctuations in the reception of the secondary wave OS. 
     Finally, the above embodiments of the general controller  41  may be combined to produce part of the adjustment parameters by optimization on the secondary wave OS received, part of the adjustment parameters by random adjustment, and part of the adjustment parameters by predefinition within the volume V. This strategy allows identifying even more receivers within the volume V, and more rapidly. 
     Furthermore, so that a receiver is able to receive and decode an adjustment parameter intended for it, the general controller  41  determines this adjustment parameter, for example according to the optimization procedure described above for each adjustable receiver  30  included in the system  10  (i.e. the receivers detected and listed by the general controller  41  in the dynamic list L at that moment in time), and the general controller  41  transmits each adjustment parameter to the corresponding associated receiver in the emission of a general control wave OCg, which may or may not be the primary wave OP. 
     In particular, this transmission in a control wave OC is carried out by any type of encoding and/or any type of modulation in the general control wave OCg emission signal that the general controller  41  supplies to the general antenna  42 . 
     Alternatively, the general controller  41  may command all adjustable receivers  30  at the same time to change their impedance or to adjust their impedance according to a parameter which is specific to each receiver. For example, a command may be sent which depends on the identity of each receiver (“includes or does not include a  0 ”, “has an even last number”, etc.), and which modifies the impedance of each reception according to a defined formula. 
     Receiver—Energy Recovery 
     Furthermore, with reference to  FIG.  2   , one (or more) adjustable receiver(s)  30  may further include an energy storage device  38  suitable for storing and possibly accumulating energy received by the energy recovery device  37 . In this manner, the adjustable receiver  30  will have more autonomy and is able to operate for a period of time determined by the capacity of said energy storage device. This energy storage device is for example a capacitor, or a battery, or any other energy storage device. 
     The energy recovery device  37  is for example capable of recovering energy from the primary wave OP and/or from the general control wave OCg in order to power its receiving device  34  and/or its controller  31  and/or the adjustable component(s)  35 . 
     The adjustable receiver  30  can thus be energy self-sufficient and also self-sufficient in adapting its impedance. It is possible that the adjustable component(s)  35  of each adjustable receiver  30  do not need a wired connection with the controller  31  of the adjustable receiver  30 , and also have access to their energy recovery device. 
     Advantageously, all the adjustable receivers of the system  10  may each have (individually) their own energy recovery device  37  and are thus independent of each other. 
     Adjustable Elements 
     Optionally, and with reference again to  FIG.  1   , the system  10  may further comprise one (or more) adjustable element  20  fixed within the volume V. The adjustable elements  20  may have an impedance which can be modified in order to modify the manner in which the primary wave OP is reflected and/or transmitted by each adjustable element  20 , in the same manner as discussed above for the adjustable receivers  30 . 
     The adjustable elements  20  are structurally and functionally similar to the adjustable receivers  30 , except that they are fixed relative to the volume V, are identified at all times by the general controller  41 , and are directly controlled at all times by the general controller  41 . Thus, they are passive elements which have their impedance dictated by the general controller  41 . 
     The number N of adjustable elements  20  is preferably greater than or equal to two. Optionally, the number N is greater than five, or ten or twenty, to further modify the distribution of the primary wave OP within the volume V. 
     According to one embodiment, the general control wave OCg or the primary wave OP emitted by the general controller  41  makes it possible to control or drive the adjustable elements  20 . The general controller  41  can thus simultaneously control or drive the adjustable elements  20  and adjustable receivers  30  of the system  10 . 
     Furthermore, each adjustable element  20  comprises a receiving device for receiving the general control wave OCg, which decodes an adjustment parameter contained in this general control wave OCg and originating from the general controller  41 . The adjustable element  20  then uses the adjustment parameter to control and modify its impedance. 
     The general control wave OCg may be within a frequency band that is identical or different from the primary wave OP. Advantageously, these waves are at a different frequency, and the transmissions are independent. 
     In addition, as the adjustable elements  20  are fixed to the container C in a plurality of different positions, it is possible to modify even further the distribution of the primary wave OP within the volume V. The positions of the adjustable elements  20  on the container C may be optimized so as to best cover the volume V with a minimum number of adjustable elements  20 . This spatial optimization may be carried out by simulation and/or measurement of the volume V. A margin may be added to the number of adjustable elements  20  used, in order to increase the identification robustness of the system  10 . 
     Adjustable Elements—Optimization 
     The adjustable element(s)  20  may be taken into account in the adjustment and/or optimization processes described above for the adjustable receivers  30 . As the adjustable element(s)  20  are identified at all times, they may then also be part of the dynamic list L. 
     Adjustable Elements—Energy Recovery 
     In addition, one, several, or all of the adjustable elements  20  (if they are part of the system  10 ) may comprise an energy recovery device similar to the one described above for the adjustable receivers  30 . The adjustable element  20  can thus be energy self-sufficient and also self-sufficient in adapting its impedance. In this case, each adjustable element  20  will not need a wired connection with a general control module, and it will not need a wired connection with the general controller  41  of this detection system  10 . 
     Adjustable Element—Spatial Distribution 
     The adjustable elements  20 , when they are present in the system  10 , can be located within the volume V without any wiring constraints (for example inside or outside the container C or on any surface of the container C). This gives great freedom in placing the adjustable elements  20  so as to best maximize the possibilities for detection and identification of all adjustable receivers  30  within the volume V. This also makes it possible to equip a container C very quickly, since it is sufficient to fix the adjustable elements  20  on the container C and to position the general antenna  42  close to the volume V. 
     The adjustable elements  20  may be attached to the container C by any attachment means. For example, the adjustable elements  20  are fixed to the container C by an adhesive or by an elastic fastening clip or by a screw or by a rivet or by interlocking or by force-fitting. 
     Furthermore, the adjustable elements  20  advantageously have a flat shape. A portion of their electrical circuit is for example directly printed on a substrate. The substrate is for example made of paper or cardboard or plastic or fabric, and for example has one side comprising an adhesive. Optionally, the portion of electrical circuit comprises an antenna. The adjustable elements  20  may also have a flexibility which allows them to bend along a radius of curvature which enables them to be fixed on non-planar surfaces. By means of these arrangements, the adjustable elements  20  can easily be fixed on a large number of surfaces (planar or non-planar) of a container, which allows positioning them at locations suitable for controlling the electromagnetic field inside the volume V. 
     Non-Adjustable Element 
     The system  10  according to the invention may further comprise non-adjustable elements  29  fixed within the volume V, having a predetermined and fixed impedance, this impedance being adapted to modify the manner in which the primary wave OP is reflected and/or absorbed by said non-adjustable element  29 . 
     This or these non-adjustable elements  29  are fixed to the container C at different positions. These non-adjustable elements  29  allow modifying in a non-controllable manner the distribution of the primary wave OP within the volume V. 
     For example, these non-adjustable elements  29  are elements resonant in the frequency band of the primary wave OP. 
     For example, a non-adjustable element  29  can reflect the primary wave OP and/or absorb the primary wave OP. This non-adjustable element can make it possible to confine the primary wave OP to the volume V of the container C in order to optimize the efficiency of the adjustable elements  20  and adjustable receivers  30  within the volume V. 
     The positions of the non-adjustable elements  29  on the container C may be optimized so that the primary wave best covers the volume V with a minimum number of adjustable elements  20 . This optimization may be carried out by simulation and/or by measurement (experimental method) of the volume V. 
     INDUSTRIAL APPLICATION 
     The system  10  incorporating adjustable receivers which participate in the detection of other receivers by their participation, in increasing numbers, in the modification and/or optimization of the electromagnetic field as they are identified by the general controller  41 , allows the general controller  41  to more quickly determine other receivers present in the volume V but not yet identified. 
     This system  10  has numerous industrial applications. 
     For example in:
         a piece of furniture (optionally equipped with adjustable elements  20 ), such as storage furniture suitable for receiving products, such as a cupboard or a shelving unit, each product having an adjustable receiver attached to it, or such as office furniture such as a desk or a table;       

     or -
         a container of a store&#39;s cash register (optionally equipped with adjustable elements  20 ), into which products are inserted, each product having an associated adjustable receiver  30 . The system will be able to identify the products by the adjustable receivers attached to the products, and the cash register will be able to issue a receipt; or   a shopping cart of a store (optionally equipped with adjustable elements  20 ) and containing inside it several items for purchase, each item having an associated adjustable receiver  30 ; or   a bag (optionally equipped with adjustable elements  20 ), for example a shopping bag, and containing inside it several items each having an adjustable receiver  30 ; or   a motor vehicle or an airplane or a train (optionally equipped with adjustable elements  20  and/or adjustable receivers  30 ) and carrying devices inside it each having an adjustable receiver  30 ; or   a room or other premises (optionally equipped with adjustable elements  20 ), for example an industrial space such as a warehouse, or a room in a residence, or a retail space in a shopping center, having movable elements each with an associated adjustable receiver  30 ; or   store shelving, where each product is equipped with an adjustable receiver  30 ; or   a storage or transit center for products, which may be sold by mail order, and where each product is equipped with an adjustable receiver  30 .