Oscillator, measurement device comprising such an oscillator and method for generating electromagnetic signals using such an oscillator

Abstract

The invention relates to an oscillator, comprising: a diffuser (2a) which is configured to backscatter an electromagnetic signal from a received electromagnetic signal; an amplifier unit (3) comprising: a transmitter unit (4) which is configured to transmit an output signal (7) to the diffuser (2a); a receiver unit (5) which is configured to receive an input signal (8), backscattered by the diffuser (2a) from the output signal (7); and an amplifier (6) having an input port (9), which is electrically coupled to the receiver unit (5), and an output port (10), which is coupled to the transmitter unit (4); wherein the amplifier (6) is configured to amplify the input signal (8) and to provide an amplified signal corresponding to the output signal (7); wherein the amplifier unit (3) is configured to transmit the output signal (7) and receive the input signal (8) via a wireless connection with the at least one diffuser (2a).

Description

[0001] Oscillator, measuring device comprising such an oscillator, and method for generating electromagnetic signals using such an oscillator

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to oscillators and their uses.

[0004] STATE OF THE ART

[0005] Currently, we are witnessing an explosion of communication between a powered transmitter / receiver (for example, by a battery) and a multitude of much less complex transmitters / receivers for performing a sensor or identification function, characterized by the absence of a battery (passive system). A widespread example of this type of system is RFID (Radio Frequency Identification), where the RFID reader, operating at ultra-high frequency (UHF), for example, is powered, and RFID tags are most often passive and require power from the reader to function.One of the problems with these devices, due to the passive nature of one of the transmitters / receivers, is that the reader must constantly emit an electromagnetic wave (most often a periodic transmission of frames), without knowing whether the RFID tag is present in the reading area or not. These emissions pollute the environment due to the wasted power emitted when there is no tag, and also generate electromagnetic pollution that disrupts and degrades other communication systems in the vicinity.

[0006] More generally, this problem also arises for very compact, mobile, battery-powered (active) systems where the application's lifespan is linked to the battery capacity. Significant research has led to the introduction of alternatives to reduce energy consumption, similar to what is found in "wake-up radio" systems. In this case, the idea is to implement a strategy to reduce consumption during periods when the device is not communicating. However, whether for completely passive systems (e.g., RFID) or systems based on the wake-up radio principle, the active transmitter / receiver must continuously emit a signal to establish communication.We could use a camera, or a sensor to detect the presence of the RFID tag, in this case the problem is the same, these systems must work all the time in order to be able to detect the presence of the object sought.

[0007] Furthermore, oscillators can be used to determine the electrical permittivity of a dielectric material. Dielectric materials are insulating materials that do not conduct electricity, used in a wide range of electronic devices and systems such as antennas, resonators, 5G network components, radars, satellite systems, magnetic resonance imaging (MRI) machines, and IoT (Internet of Things) devices. To be deployed in industrial segments with varying requirements, dielectric materials often require radio frequency (RF) characterization.

[0008] Radio frequency characterization allows for the understanding of electrical properties at different frequencies (e.g., permittivity or dielectric constant, loss tangent), the selection of the most suitable material for a specific application (e.g., a low-loss material to minimize signal attenuation or a high-permittivity material for compact devices). Characterization also allows for the confirmation of dielectric quality during manufacturing processes, the prediction of signal behavior as it passes through dielectric materials (propagation and reflection), the minimization of interference and crosstalk between different components, and the ensuring of safety, reliability, and compliance with regulations and industry standards, particularly for medical devices or aerospace systems.

[0009] Several techniques exist for measuring the dielectric properties of materials. Examples include the coaxial probe method, the resonant cavity method, the transmission line method, free-space measurement, and the parallel-plate capacitor method. These techniques are based on the same principle: the use of RF measurement equipment, most often a vector network analyzer (VNA), and a dedicated test setup connected to the VNA via cables. The calibration of the free-space method, in particular, is difficult to implement. Furthermore, the fact that this method is "non-contact" introduces specific challenges, notably the practical difficulty of calibrating the system.The size of the material can introduce errors due to diffraction effects at the edges, which is why the minimum frequency is determined by the maximum sample length. Furthermore, resonance techniques, such as the cavity method, are only possible with samples that are small relative to the characterization wavelength. In addition, measurements can only be performed at a few frequencies (other frequencies require a cavity with different dimensions), and this technique necessitates specialized, and very expensive, equipment (a precision metallic cavity).

[0010] Generally speaking, each of these techniques is only suitable for a particular type / shape of material or frequency. As a result, existing methods are not adapted to the ever-increasing needs of companies developing products requiring dielectric materials of diverse properties, because most of them lack the advanced skills necessary for material characterization, nor the equipment to implement these characterization methods. Furthermore, for reasons of cost or supply, these companies are forced to use materials that are not necessarily suitable for RF applications (or simply whose RF properties are unknown), which poses a problem: typically, plastics that, despite having the same name, can actually have very different dielectric properties, particularly in terms of losses.

[0011] One example is the publication "Permittivity characterization based on Radar Cross Measurements, Etienne Perret, 2016 URSI International Symposium on Electromagnetic Theory (EMTS), Aug 2016, Espoo, France, pp. 457-460; ffhal-02053983," which describes a method for measuring the permittivity of a dielectric material using a diffuser placed on the material and a vector network analyzer (VNA) connected to an antenna to transmit and receive oscillating signals through the diffuser in order to determine the material's permittivity. Specifically, the VNA measures the field backscattered by the diffuser. However, dielectric losses are not measured.

[0012] Another relevant publication is "Wireless Communication in Feedback-Assisted Active Sensors," by Mohammad Abdolrazzaghi, Mohammad Hossein Zarifi, and Mojgan Daneshmand, published in the IEEE Sensors Journal, Vol. 16, No. 22, November 15, 2016, pages 8151-8157. This publication discloses a method for measuring the permittivity of a dielectric material using a system comprising a support on which a resonator and an active feedback loop are mounted. This loop is electromagnetically coupled to the resonator to form an oscillator that generates oscillating signals at the oscillator's oscillation frequency. The dielectric material is placed on the support in electrical contact with the resonator. The system also includes two antennas used to receive and transmit the oscillating signals generated by the oscillator, and a vector network analyzer used to determine the oscillation frequency of the oscillating signals.In particular, the antennas are connected to the resonator by electrical transmission lines, and the dielectric material is placed in contact with the resonator and a transmission line connected to one of the two antennas.

[0013] However, the transmission lines and feedback loop affect the behavior of the resonator and the dielectric material, resulting in imprecise measurements. Furthermore, the measurement is dependent on the precise geometry and position of the dielectric material, and the method is not suitable for all material geometries. Moreover, errors in the dimensions of the dielectric material or its positioning relative to the resonator impact the measurement results, particularly the permittivity value. Additionally, the feedback loop's connection to the dielectric material being characterized introduces measurement errors and leads to imprecise characterization.

[0014] SUMMARY OF THE INVENTION

[0015] One object of the invention is to overcome these drawbacks, and more particularly to provide means to detect the presence of an object, using a simple system that consumes the least amount of energy.

[0016] Another objective is to provide means for the characterization of a material, in particular for measuring a permittivity of the material, which are more accurate and simpler to implement.

[0017] Another object of the invention is to provide simple means for providing a device for measuring various parameters, such as temperature, humidity, the presence of a particular gas, or the presence of a device or the identification of a device.

[0018] According to one aspect of the invention, an oscillator is proposed, comprising:

[0019] - at least one broadcaster configured to backscatter an electromagnetic signal from a received electromagnetic signal; and

[0020] - an amplifier unit comprising: o a transmitting unit configured to transmit an electromagnetic signal, called the output signal, to said at least one broadcaster; o a receiving unit configured to receive an electromagnetic signal, called the input signal, backscattered by said at least one broadcaster from the output signal received by said at least one broadcaster; and o an amplifier having an input port electrically coupled to the receiving unit and an output port coupled to the transmitting unit; the amplifier being configured to amplify the input signal received at its input port and to provide, at its output port, an amplified signal corresponding to the output signal transmitted by the transmitting unit to said at least one broadcaster.

[0021] In particular, the amplifier unit is configured to transmit the output signal and receive the input signal via a wireless connection with said at least one broadcaster.

[0022] Thus, there is no mechanical link between the diffuser and the amplifier unit, nor are there any wires connecting them. Communication between the diffuser and the amplifier unit occurs via an electromagnetic signal transmitted through the air between the two geometrically separated elements, that is, at a distance from each other, allowing for the creation of an oscillation. The diffuser, or amplifier unit, is therefore potentially mobile relative to the other, with no mechanical connection between the amplifier and the diffuser.

[0023] Thus, an oscillator with a wireless feedback loop, formed in particular by the amplifier, is provided. Such an oscillator is particularly simple to implement. Advantageously, it is an inexpensive oscillator to manufacture. Furthermore, it is a simple oscillator to implement and particularly well-suited for various applications such as: a presence sensor or a physical parameter measurement device, like the radio frequency characterization of a dielectric.

[0024] According to another aspect, a device is proposed for measuring at least one parameter of an electromagnetic signal, comprising an oscillator as defined above, and a processing unit configured to determine a frequency and amplitude of the input signal.

[0025] Thus, we provide a device that allows us to significantly improve the accuracy of a measurement of a parameter of an electromagnetic signal.

[0026] Furthermore, a device is provided which, when the diffuser is not near the amplification unit, emits no electromagnetic signal other than noise. Conversely, once the diffuser is positioned near the amplification unit, the system composed of the diffuser and the amplification unit will generate in space at least one electromagnetic wave at at least one given frequency (or several given frequencies) related to the properties of the diffuser and the amplification unit.

[0027] According to another aspect, a method for generating electromagnetic signals is proposed, including the provision of an oscillator as defined above.

[0028] The method includes transmission, by the amplifier unit, of the output signal and reception, by the amplifier unit, of the input signal via a wireless connection with said at least one broadcaster.

[0029] BRIEF DESCRIPTION OF THE FIGURES

[0030] Other objects, features and advantages of the present invention will become apparent upon examination of the following detailed description and accompanying drawings, in which:

[0031] Figures 1 to 4 represent different embodiments of an oscillator and a measuring device according to the invention.

[0032] The drawings are given as examples and are not limiting to the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications.

[0033] DETAILED DESCRIPTION OF THE INVENTION

[0034] Before beginning a detailed review of embodiments and implementations of the invention, optional features that may be used in combination or alternatively are stated below.

[0035] According to one example, said at least one diffuser is a resonant diffuser configured to backscatter an input electromagnetic signal having a specific frequency, called the resonance frequency.

[0036] For example, the resonant frequency is between 10 MHz and 200

[0037] GHz.

[0038] According to one example, at least one element, taken from said at least one broadcaster and the amplifier unit, is configured to be movable relative to the other element between a first relative position of the amplifier unit with respect to said at least one broadcaster in which the amplifier generates, at its output port, an initial output signal and said at least one broadcaster does not backscatter the input signal, and at least a second relative position of the amplifier unit with respect to said at least one broadcaster, said at least a second position being distinct from the first position, in which said at least one broadcaster backscatters the input signal to the receiving unit, and the amplifier provides, at its output port, the amplified signal corresponding to the output signal transmitted by the transmitting unit to said at least one broadcaster.

[0039] In one example, the amplifying unit includes a phase shifter electrically coupled in series with the amplifier.

[0040] In one example, the amplifier unit includes a filter electrically coupled in series with the amplifier.

[0041] In one example, the receiving unit is located at a distance from the transmitting unit, so that the receiving unit does not receive the output signal directly transmitted by the transmitting unit.

[0042] In one example, the transmitting unit has a first polarization and the receiving unit has a second polarization different from the first polarization.

[0043] According to one example, the transmitting unit and the receiving unit form a single antenna, and the amplifier unit includes a radio frequency circulator comprising first and second ports coupled respectively to the input and output ports of the amplifier, and a third port coupled to the transmitting and receiving units of the antenna, the radio frequency circulator being configured to transmit the amplified signal from the output port of the amplifier to the third port and to transmit the input signal received, via the receiving unit, on the third port to the first port of the radio frequency circulator.

[0044] According to one example, the device is configured to determine a complex permittivity of a sample, in which said at least one scatterer has a complex permittivity having a reference value for which said at least one scatterer backscatters the input signal having a first frequency and a first amplitude as a function of the reference value, and when said at least one scatterer cooperates with a sample in such a way that the sample changes the value of the complex permittivity of said at least one scatterer, said at least one scatterer backscatters the input signal having a second frequency and a second amplitude distinct from the first frequency and first amplitude, and the processing unit is configured to determine the complex permittivity of the sample as a function of a difference between the first and second frequencies and a difference between the first and second amplitudes.Such a device is particularly well-suited for characterizing materials with very low dielectric losses. Very low losses are defined as materials characterized by loss tangent values ​​(or delta tangent or tan(5)) less than 10⁻³. These materials are widely used in radio frequency applications, where losses play a crucial role in the performance of devices made with this type of material. For example, some materials have a loss tangent of 0.0012 at frequencies of 12 GHz. Other materials have a loss tangent on the order of 0.01. Materials with a loss tangent greater than 0.1 are considered to have high losses for radio frequency applications.

[0045] The device is also suitable for characterizing various materials, such as rigid or semi-rigid dielectrics in the form of thin plates (typically materials used for printed circuit boards), with thicknesses on the order of millimeters (up to 1 cm), dielectric plates that are not perfectly flat (potentially curved), and not necessarily homogeneous. The device also allows for the characterization of non-solid dielectric materials such as powders, liquids, or gels.

[0046] The device is also suitable for characterizing the permeability and magnetic losses of materials.

[0047] According to one example, the device is configured to determine a temperature of an environment, in which said at least one diffuser has a geometry and / or permittivity having a reference value for a reference temperature for which said at least one diffuser backscatters the input signal having a first frequency as a function of the reference temperature, and when said at least one diffuser cooperates with an environment having a temperature in such a way that the environment modifies the geometry and / or permittivity of said at least one diffuser, said at least one diffuser backscatters the input signal having a second frequency distinct from the first frequency, and the processing unit is configured to determine the temperature of the environment as a function of a difference between the first and second frequencies.

[0048] According to one example, the device is configured to determine a humidity level, wherein said at least one diffuser has a permittivity having a reference value for a reference humidity level for which said at least one diffuser backscatters the input signal having a first frequency as a function of the reference humidity level, and when said at least one diffuser cooperates with an environment having a humidity level such that the environment modifies the permittivity of said at least one diffuser, said at least one diffuser backscatters the input signal having a second frequency distinct from the first frequency, and the processing unit is configured to determine the humidity level of the environment as a function of a difference between the first and second frequencies.

[0049] According to one example, the device is configured to determine the presence of said at least one scatterer, wherein at least one element, taken from said at least one scatterer and the amplifier unit, is configured to be movable relative to the other element, and when said at least one scatterer is located at a first distance from the oscillator transmitting unit, said at least one scatterer does not backscatter the input signal and when said at least one scatterer is located at a second distance from the oscillator transmitting unit, the second distance being distinct from the first distance, said at least one scatterer backscatters the input signal having a reference frequency, and the processing unit is configured to determine the presence of said at least one scatterer when a difference between the frequency of the input signal determined by the processing unit and the reference frequency is less than or equal to a frequency threshold.

[0050] According to one example, the device is configured to identify said at least one scatterer, wherein said at least one scatterer is configured to backscatter the input signal having a reference frequency and exhibiting an electromagnetic field having a reference orientation, the receiving unit of the oscillator has a polarization configured to receive a signal exhibiting an electromagnetic field having the reference orientation, and the processing unit is configured to identify said at least one scatterer when a difference between the frequency of the input signal determined by the processing unit and the reference frequency is less than or equal to a frequency threshold.

[0051] In one example, the oscillator includes several diffusers configured to backscatter several input signals having distinct frequency values, and the processing unit is configured to identify the diffusers when the processing unit determines the frequency values.

[0052] According to one example, the method comprises a first relative positioning of at least one element, taken from said at least one diffuser and the amplifier unit, with respect to the other element in a first relative position in which the amplifier generates, at its output port, an initial output signal and said at least one diffuser does not backscatter the input signal and a second relative positioning in at least a second relative position, distinct from the first position, in which said at least one diffuser backscatters the input signal to the receiving unit, and the amplifier provides, at its output port, the amplified signal corresponding to the output signal transmitted by the transmitting unit to said at least one diffuser.

[0053] It is specified that, within the framework of the present invention, the expressions "A coupled to B," "A electrically coupled to B," "A connected to B," or "A electrically connected to B" are synonymous with "A is electrically connected to B" and do not necessarily imply that there is no component between A and B. Thus, these expressions refer to an electrical connection between two elements, this connection being either direct or indirect. This means that it is possible for a current to flow between a first device A and a second device B that are electrically connected, linked, or coupled, at A, at B, and along the path connecting A to B, this path being either or not including other electrical equipment. Device A can be electrically coupled to B, either in series or in parallel.

[0054] Conversely, in the context of the present invention, the term "electrically connected directly" or "directly linked" refers to a direct electrical connection between two elements. This means that between a first device A and a second device B that are electrically connected directly, no other equipment is present, other than an electrical connection (such as an electrical wire) or several electrical connections.

[0055] Figures 1 to 4 depict an oscillator 1. Generally, an oscillator is configured to produce an electromagnetic signal, in particular a periodic one. More specifically, an oscillator produces a signal having a characteristic frequency, called the resonant frequency.

[0056] The oscillator 1 includes at least one diffuser 2a, 2b and one amplifier unit 3.

[0057] In general, a 2a, 2b scatterer is configured to backscatter at least one electromagnetic signal, in particular a periodic signal, and more specifically at least one signal having a characteristic frequency, known as the resonance frequency, from a received electromagnetic signal. A 2a, 2b scatterer can be any object, for example, a user's hand, a metal plate, a polymer card, or an RFID tag. A 2a, 2b scatterer can be resonant. In this case, the 2a, 2b scatterer is configured to backscatter a signal having a specific frequency, known as the resonance frequency, within a particular frequency band, called the resonance frequency band. A resonant 2a, 2b scatterer acts as a radio frequency filter, backscattering electromagnetic signals into space only within the aforementioned resonance frequency band. This filter is a bandpass type, thus allowing one or more frequency bands to pass through.For example, the diffuser 2a, 2b is metallic, for example, made of aluminum or copper. For example, the diffuser 2a, 2b can be flat. Generally, the diffuser 2a, 2b has a loop shape, for example, an open loop and preferably a closed loop. The open loop shape is such that the length of the loop opening is strictly less than the length L of the loop. The loop can be rectangular. Furthermore, the diffuser 2a, 2b is configured to resonate, that is, to emit at least one periodic electromagnetic signal at the resonant frequency, the resonant frequency being a function of the length L of the diffuser 2a, 2b. Advantageously, a metallic loop can be easily obtained using laser cutting.

[0058] Alternatively, the diffuser 2a, 2b can include several metallic parts such as a rear ground plane (a metallic part that completely covers the face) and a metallic pattern on the front face. Between the two metallic parts is a dielectric material. The metallic pattern on the front face can be simply a rectangle or a loop as described previously. It is the combination of these three elements that will resonate and exhibit the behavior of a radio frequency filter capable of re-emitting a signal at at least one given frequency (resonance frequency) into space.

[0059] Alternatively, as illustrated in Figure 4, the oscillator 1 can include several diffusers 2a, 2b having distinct resonant frequencies respectively. By "distinct," we mean that the resonant frequencies have different respective values.

[0060] The amplifier unit 3 comprises a transmitter unit 4, a receiver unit 5, and an amplifier 6. The transmitter unit 4 is configured to transmit an electromagnetic signal 7, called the output signal, to the diffuser 2a, 2b. More specifically, the transmitter unit 4 transmits the output signal 7 provided by the amplifier 6. The receiver unit 5 is configured to receive an electromagnetic signal 8, called the input signal, generated by the diffuser 2a, 2b from the output signal 7 received by the diffuser 2a, 2b. In particular, the input signal 8 is a periodic signal having a frequency equal to the resonant frequency of the diffuser 2a, 2b. Furthermore, the amplifier 6 has an input port 9 electrically coupled to the receiving unit 5, preferably directly, by a first connection C1, and an output port 10 coupled to the transmitting unit 4, for example directly, by a second connection C2.Thus, the amplifier 6 receives, at its input port 9, the input signal 8 emitted by the diffuser 2a, 2b and transmitted by the receiving unit 5 to the amplifier 6. The amplifier 6 is configured to amplify the input signal 8 received at its input port 9 and to provide, at its output port 10, an amplified signal corresponding to the output signal 7 transmitted by the transmitting unit 4 to the diffuser 2a, 2b.

[0061] More specifically, the amplifier unit 3 is configured to transmit the output signal 7 and receive the input signal 8 via a wireless connection with each diffuser 2a, 2b. A wireless connection is defined as the fact that the amplifier unit 3 is not mechanically connected to the diffusers 2a, 2b. Furthermore, the amplifier unit 3 is not electrically connected to the diffusers 2a, 2b. There is no wired electrical connection between the amplifier unit 3 and the diffusers 2a, 2b. The amplifier unit 3 is also configured to be coupled to the diffusers 2a, 2b via radio frequency electromagnetic waves. For example, at least one element, chosen from among the diffusers 2a, 2b and the amplifier unit 3, is configured to be mobile relative to the other element. Preferably, the amplifier unit 3 is configured to be mobile when moving relative to the diffuser 2a, 2b.In other words, the amplifier 6 is not directly coupled to the diffuser 2a, 2b, but the amplifier 6 is connected, via the transmitter unit 4 and receiver unit 5, to the diffuser 2a, 2b by a wireless connection, which allows, in particular, the placement of the amplifier 6 at a distance from the diffuser 2a, 2b, that is to say, which allows the amplifier 6 to be moved further away or closer to the diffuser 2a, 2b.

[0062] Such an oscillator 1 allows the generation of an electromagnetic wave in the space surrounding the transmitting and receiving units 4, 5 (continuous wave, or sinusoidal wave) only when a diffuser 2a, 2b is present in the vicinity of the units 4, 5 of the amplifying unit 3. Indeed, when a diffuser 2a, 2b is far away, no continuous wave is backscattered by the diffuser 2a, 2b, on the other hand once the diffuser 2a, 2b is located in the vicinity (on the order of a meter) of the amplifying unit 3, the diffuser 2a, 2b will allow an oscillation, we also say that the oscillator 1 oscillates. Oscillator 1 can be used to measure various parameters, such as the electrical permittivity of a sample, temperature, humidity, or oscillator 1 can be used as a detector of the presence of an object or gas, or as an object identifier.In general, the measurements of the aforementioned parameters depend on the resonant frequency of the diffuser 2a, 2b and the frequency of the input signal 8 backscattered by the diffuser 2a, 2b. Figures 1 to 4 also show a measuring device 100 for at least one parameter of an electromagnetic signal. The measuring device 100 comprises the oscillator 1, as described above, and a processing unit 101. The processing unit 101 is configured to determine the frequency and amplitude of the input signal 8 backscattered by the diffuser 2a, 2b of the oscillator 1. For example, the processing unit 101 may include an electronic control unit 200 integrated within the amplifier unit 3. The electronic control unit 200 may be a microprocessor or a transistor logic circuit. The electronic control unit 200 is configured to perform logical operations, such as calculations, comparisons, etc.from electromagnetic signals. Alternatively, the processing unit 101 may include a vector network analyzer or spectrum analyzer or oscilloscope 201 coupled to an antenna 202 to determine the frequency of the input signal 8.

[0063] In general, the amplifier 6 forms a feedback loop with the diffuser 2a, 2b, allowing the oscillations generated by the oscillator 1 to be maintained (or self-sustained). These oscillations correspond to the periodic input 8 and output 7 signals. This improves control of the quality factor of the diffuser 2a, 2b and, consequently, significantly reduces measurement errors. The quality factor of the diffuser 2a, 2b is the ratio of its resonant frequency to the bandwidth of the backscattered input signal 8; the quality factor is dimensionless. For example, the frequency band could range from 10 MHz to 200 GHz. In addition, the quality factor of the diffuser 2a, 2b can be between 10 and 1000, and more specifically between 50 and 150. The amplifier unit 3 allows the use of an active feedback loop remotely, i.e. not directly connected to the diffuser 2a, 2b.Amplifier 6 compensates for the attenuation of the input signal 8. Since the attenuation is related to the frequency of the input signal 8 backscattered by the diffuser 2a, 2b, amplifier 6 maintains the oscillations and thus provides periodic signals 8, 7 with a stable frequency. When the oscillator oscillates, at least one periodic signal at the resonant frequency of a diffuser 2a, 2b circulates in the feedback loop. The device can be set into oscillation extremely quickly (on the order of less than a second) because the propagating electromagnetic waves are electromagnetic fields with a propagation speed close to the speed of light.

[0064] Advantageously, the amplifier unit 3 includes a coupler 203 electrically connected in series with the amplifier 6. The coupler 203 is configured to take an adjustable portion (preferably very small, i.e., less than or equal to 1%) of the signal circulating in the feedback loop. The coupler 203 includes an output port 204 on which the coupler provides the taken portion of the signal circulating in the feedback loop. For example, the coupler 203 can be electrically connected between the receiving unit 5 and the input port 9 of the amplifier 6, and the coupler 203 provides a portion of the input signal 8 on its output port 204. The coupler 203 can also be electrically connected between the output port 10 of the amplifier 6 and the transmitting unit 4, and in this case the coupler 203 provides a portion of the output signal 7.For example, output port 204 of coupler 203 can be electrically coupled to processing unit 101 to determine the various parameters mentioned above. Generally, the sampled portion of the signal can be processed by processing unit 101 to determine the amplitude and / or frequency of the signal circulating in the feedback loop, and thus determine the various parameters mentioned above. Alternatively, the VNA can be directly connected to coupler 203 to measure the signal quantities. One advantage of coupler 203 is that it causes minimal disturbance to the signal circulating in the feedback loop (less than 1%).

[0065] For example, the amplifier unit 3 is movable between a first position P1 in which the amplifier 6 generates, at its output port 10, an initial output signal 11 and the diffuser 2a, 2b does not backscatter the input signal 8, and at least a second position P2 in which the amplifier 6 generates, at its output port 10, the initial output signal 11, the diffuser 2a, 2b backscatters the input signal 8 to the receiving unit 5, and the amplifier 6 provides, at its output port 10, the amplified signal corresponding to the output signal 7 transmitted by the transmitting unit 4 to the diffuser 2a, 2b. In other words, the initial output signal 11 can be an aperiodic electromagnetic signal, that is, a signal corresponding to noise, also called a noisy signal. The initial output signal 11 can also be periodic. In addition, the input signal 8 generated by the diffuser 2a, 2b is periodic, its frequency is noted as the resonance frequency.Then, when the output signal 7, corresponding to the amplified input signal 8, becomes periodic, we say that oscillator 1 produces periodic signals; we also say that oscillator 1 oscillates. In particular, the input signal 8 and the output signal 7 have the resonant frequency of the diffuser 2a, 2b. Unlike the initial output signal 11, which is aperiodic, the output signal 7 is a periodic amplified signal.

[0066] Thus, when the amplifier unit 3 occupies the first position P1, the transmitter unit 4 is located at a first distance D1 from the diffuser 2a, 2b. In this case, the diffuser 2a, 2b does not backscatter the periodic input signal 8, and the oscillator 1 does not generate oscillations. The first position P1 is considered to be a position far from the amplifier unit relative to the diffuser 2a, 2b. Conversely, when the amplifier unit occupies at least a second position P2 (distinct from the first position P1), the transmitter unit 4 is located at a second distance D2 from the diffuser 2a, 2b, the second distance D2 being distinct from the first distance D1. By "distinct," we mean that the first and second distances have different respective values.

[0067] In other words, in the first position P1, oscillator 1 emits no electromagnetic signal other than noise 11. It is also said that the oscillator does not oscillate. That is to say, when the diffuser 2a, 2b is located at a first distance D1 from the transmitting unit 4 of oscillator 1 (in particular when the diffuser 2a, 2b is located far away, i.e., several meters away), the diffuser 2a, 2b does not backscatter the input signal 8 to the amplifier unit 3. Conversely, when the diffuser 2a, 2b is located at a second distance D2 from the transmitting unit 4 of oscillator 1, the second distance D2 being strictly less than the first distance, the diffuser 2a, 2b backscatters the input signal 8 having a reference frequency (the resonant frequency of the diffuser 2a, 2b).In this case, oscillator 1 emits an electromagnetic wave in space at the reference frequency (directly linked to the diffuser) throughout space, allowing any system capable of recovering this signal (located even at a distance of several tens, or even several hundred meters) and interpreting it, to associate a specific action (such as sending a message, turning on a light bulb, emitting a sound signal...).

[0068] For example, the second distance D2 can be less than or equal to 10 * (2 * D2) / A; where D is the greatest length of the receiving unit 5 (in cm) and A is the wavelength of the input signal 8 emitted by the diffuser 2a, 2b (in cm). For example, the second distance D2 can be between 1 cm and 10 m, preferably between 1 cm and 1 m.

[0069] Thus, thanks to a mobile amplifier unit 3 that is free to move and has no mechanical or electrical connection to the diffuser 2a, 2b, the amplifier 6 can be moved closer to or further from the diffuser 2a, 2b. Moving the amplifier 6 further from the diffuser 2a, 2b allows for frequency measurements of the input signal 8 and the output signal 7 by placing the diffuser and the amplifier in two different environments. Furthermore, this movement can be used to operate the oscillator 1 as a presence detector. When the amplifier unit 3 is sufficiently far from the diffuser 2a, 2b, there are no oscillations. Then, when the amplifier unit 3 is moved sufficiently close to the diffuser 2a, 2b, the oscillator 1 generates oscillations. We can then determine for each position of the amplifier unit 3 relative to the diffuser 2a, 2b, whether there are oscillations.In other words, oscillations are generated when the diffuser 2a, 2b is positioned in a specific area of ​​the transmitting unit 4. This generation of oscillations, occurring in the space surrounding the transmitting unit 4 and the receiving unit 5 of the amplifier unit 3, can be detected over very long distances, namely several meters or even hundreds of meters. In this case, the telecommunications equation (also called the Friis equation, which allows us to obtain the radio power collected by a receiver as a function of the distance between the receiver and the radio transmitter) makes it possible to determine the maximum permissible distance between the amplifier unit 3 and the diffusers 2a, 2b.

[0070] Advantageously, the amplifier unit 3 can include a phase shifter 12 electrically coupled in series with the amplifier 6. For example, the phase shifter 12 can be electrically coupled between the output port 10 of the amplifier 6 and the transmitter unit 4. That is to say, the phase shifter includes a first port 13 coupled to the output port 10 of the amplifier, preferably directly, and a second port 14 coupled to the transmitter unit 4, by the second connection C2. For example, the phase shifter 12 can be coupled between the receiver unit 5 and the input port 9 of the amplifier 6. The phase shifter 12 improves the maintenance of oscillations when the diffuser 2a, 2b is moved relative to the amplifier unit 3. The oscillations can indeed be maintained for continuous variations in distance (i.e. different distances D1 and D2) between the diffuser 2a, 2b and the amplifier unit 3.

[0071] According to another advantage, the amplifier unit 3 includes a filter 205 electrically coupled in series with the amplifier 6. For example, the filter 205 can be electrically coupled between the receiver unit 5 and the input port 9 of the amplifier 6. Preferably, the filter 205 is electrically coupled between the output port 10 of the amplifier 6 and the transmitter unit 4. The filter 205 is configured to block signals having frequencies different from the resonant frequency of the diffuser 2a, 2b. In other words, the filter 205 is configured to filter a portion of the input signal 8 and to transmit to the transmitter unit 4 a filtered output signal 7 towards the diffuser 2a, 2b. For example, the filter 205 is of the bandpass type. In particular, the filter 205 has a center attenuation frequency equal to the resonant frequency of the diffuser 2a, 2b. The 205 filter will allow control of the resonance frequency.Furthermore, without filter 205, we can obtain an oscillation of oscillator 1 that we can detect.

[0072] Advantageously, oscillator 1 can be coupled to an RFID reader. For example, oscillator 1 can be used as a presence detector: the diffuser 2a, 2b can be equivalent to an RFID tag. Thus, when an oscillation is detected, the RFID reader can be activated by initiating wave transmission. In this case, if there is no tag present, for example, when the diffuser 2a, 2b is too far from the amplifier unit 3 (for example, in the first position P1), the oscillator blocks the RFID reader; that is, oscillator 1 does not oscillate, and therefore no wave is sent by the RFID reader. Conversely, if the tag is present in the oscillator's reading range, i.e., in the second position P2, the diffuser 2a, 2b is detected, and the RFID reader is activated to read the tag. Thus, oscillator 1 does not read the information emitted by the label but the presence of the label.

[0073] Figure 1 shows an embodiment in which the receiving unit 5 is located at a distance D3 from the transmitting unit 4, so that the receiving unit 5 does not receive the output signal 7 transmitted directly by the transmitting unit 4. This avoids interference of the output signal 7 on the input signal 8. In this configuration, the signal recovered by the receiving unit 5 originates predominantly from the signal backscattered by the diffuser 2a, 2b.

[0074] Figure 2 shows another embodiment in which the transmitting unit 4 has a first bias and the receiving unit 5 has a second bias different from the first. This configuration also ensures that the receiving unit 5 does not receive the output signal 7 transmitted directly by the transmitting unit 4.

[0075] Figure 3 shows another embodiment in which the transmitting unit 4 and the receiving unit 5 form a single antenna 20, and the amplifier unit 3 includes a radio frequency circulator 21. The radio frequency circulator 21 includes first and second ports B1, B2 coupled respectively to the input and output ports 9, 10 of the amplifier 6, by the first and second connections C1, C2, and a third port B3 coupled to the transmitting and receiving units 4, 5 of the antenna 20, by a third connection C3. The radio frequency circulator 21 is further configured to transmit the amplified signal 7 from the output port 10 of the amplifier 6 to the third port B3 and to transmit the input signal 8 received, via the receiving unit 5, on the third port B3 to the first port B1 of the radio frequency circulator 21.

[0076] For example, device 100 is configured to determine the complex permittivity of a sample 102, in which the diffuser 2a, 2b exhibits a complex permittivity having a reference value for which the diffuser 2a, 2b backscatters the input signal 8 having a first frequency F1 as a function of the reference value. Complex permittivity is understood to be a permittivity having a real part and an imaginary part. The imaginary part (which corresponds to the loss tangent) represents the conductivity losses of the dielectric as a function of the frequency of the electromagnetic wave propagating through it. For example, sample 102 is a dielectric material. In this case, when the diffuser 2a, 2b interacts with sample 102 in such a way that sample 102 modifies the complex permittivity value of the diffuser 2a, 2b, the diffuser 2a, 2b backscatters the input signal 8 having a second frequency F2 distinct from the first frequency F1.Thus, the processing unit 101 is configured to determine the complex permittivity of sample 102 as a function of the difference between the first and second frequencies F1, F2 and the amplitudes associated with the different RF signals. The processing unit 101 is also configured to determine the bandwidth of the input signal 8 backscattered by the diffuser. Therefore, the processing unit 101 is configured to determine the complex permittivity of sample 102 as a function of the frequency of the input signal 8 and the power factor of the diffuser 2a, 2b.

[0077] In other words, sample 102 affects the resonance frequency and quality factor of the diffuser 2a, 2b. Thus, by determining, for example, the frequency difference F2-F1, one can determine the permittivity of sample 102. Furthermore, the first frequency F1 can be determined beforehand, for example using the vector network analyzer 201, by placing the diffuser 2a, 2b in air. Adhesive tape can be used to suspend the diffuser 2a, 2b in air to approximate a free-space condition as closely as possible. Then, the diffuser 2a, 2b is placed in contact with the sample 102 to be characterized. For example, the diffuser 2a, 2b can be attached to sample 102 using the same adhesive tape. Thus, we can determine the second frequency F2 of the input signal 8 emitted by the diffuser 2a, 2b in contact with the sample 102.In each of the two configurations, it is also possible to measure the amplitude level of the two signals for the same spacing between the diffuser 2a, 2b and the amplifier unit 3. From the resonance frequencies and amplitude levels, it is possible to determine the complex permittivity of the sample that we are trying to characterize.

[0078] The size of the sample 102 is chosen according to the frequency band of the diffuser 2a, 2b. For example, the length and width of the sample 102 can be greater than A / 2 so that the diffuser 2a, 2b is completely flattened on the sample 102, which facilitates the determination of the complex permittivity, with A the resonant wavelength of the diffuser 2a, 2b, i.e. the wavelength of the input signal 8 backscattered by the diffuser 2a, 2b.

[0079] Cooperation between diffuser 2a, 2b and sample 102 refers to the fact that diffuser 2a, 2b can be positioned on sample 102, through mechanical contact, or within sample 102. Cooperation corresponds to mechanical contact of diffuser 2a, 2b with sample 102. Advantageously, diffuser 2a, 2b is purely metallic and contains no substrate. In this case, diffuser 2a, 2b can be brought into direct contact with sample 102, further improving the permittivity measurement. In the case of a diffuser with a ground plane, the face opposite the ground plane is brought into mechanical contact with the dielectric.

[0080] Because only the diffuser 2a, 2b interacts with the sample 102, the accuracy of the complex permittivity measurement is improved. Furthermore, the shape of the diffuser 2a, 2b can be easily adapted to that of the sample 102. This provides an apparatus 100 suitable for samples of various sizes, shapes (e.g., curved shapes), or types, such as powders, gels, liquids, pastes, etc. In addition, the sample 102 and the diffuser 2a, 2b can be placed in different environments 103, for example, in a climate chamber (the amplifier unit 3 can thus be positioned outside the chamber). This allows measurements to be performed as a function of different physical quantities, such as temperature, humidity, or the presence of specific gases to be characterized.

[0081] According to another example, device 100 is configured to determine the temperature of an environment 103. In particular, the diffuser 2a, 2b has a geometry and / or permittivity with a reference value for a reference temperature for which the diffuser 2a, 2b backscatters the input signal 8 having a first frequency F1 as a function of the reference temperature. Thus, when the diffuser 2a, 2b interacts with an environment having a temperature such that the environment 103 modifies the geometry and / or permittivity of the diffuser 2a, 2b, the diffuser 2a, 2b backscatters the input signal having a second frequency F2 distinct from the first frequency F1, and the processing unit 101 is configured to determine the temperature of the environment 103 as a function of the difference between the first and second frequencies F1, F2.

[0082] According to another example, the device 100 is configured to determine the presence of a particular gas. A diffuser 2a, 2b exhibits a permittivity having a reference value when the diffuser 2a, 2b cooperates with air for which said diffuser 2a, 2b backscatters the input signal 8 having a first frequency as a function of the air, and when said diffuser 2a, 2b cooperates with a particular gas other than air such that the particular gas modifies the permittivity of said diffuser 2a, 2b, said diffuser 2a, 2b backscatters the input signal 8 having a second frequency distinct from the first frequency, and the processing unit 101 is configured to determine the particular gas as a function of a difference between the first and second frequencies.

[0083] According to another example, device 100 can be configured to determine the humidity level of an environment 103. In this case, the resonant diffuser 2a, 2b has a permittivity with a reference value for a reference humidity level at which the diffuser 2a, 2b backscatters the input signal having a first frequency F1 as a function of the reference humidity level. Thus, when the diffuser 2a, 2b interacts with an environment 103 having a humidity level such that the environment 103 modifies the permittivity of the diffuser 2a, 2b, the diffuser 2a, 2b is configured to backscatter the input signal 8 having a second frequency F2 distinct from the first frequency F1. Furthermore, the processing unit 101 is configured to determine the humidity level of the environment 103 as a function of the difference between the first and second frequencies F1, F2.

[0084] According to another example, device 100 can be configured to determine the presence of the diffuser 2a, 2b. When the diffuser 2a, 2b is located at a first distance D1 from the transmitting unit 4 of oscillator 1, the diffuser 2a, 2b does not backscatter the input signal 8. However, when the diffuser 2a, 2b is located at least a second distance from the transmitting unit 4, the second distance D2 being distinct from the first distance D1, the diffuser 2a, 2b backscatters the input signal 8 having a reference frequency Fref. Thus, the processing unit 101 is configured to determine the presence of the diffuser 2a, 2b when a difference between the frequency of the input signal 8, as determined by the processing unit 101, and the reference frequency Fref is less than or equal to a frequency threshold. For example, the frequency threshold is equal to 0 Hz, it can also be equal to 1 Hz.In other words, the processing unit 101 determines the presence of the scatterer 2a, 2b when it detects a signal at frequency Fref, preferably with a certain amplitude (greater than the sensitivity of the measuring device 100). The presence of the scatterer 2a, 2b can also be determined when the electronic control unit 200 detects a change in the supply current of the amplifier 6. The device 100, configured to determine the presence of the scatterer 2a, 2b, does not need to continuously emit a periodic signal, as is the case for radio frequency systems, for example, in the field of UHF RFID. Indeed, in the absence of a scatterer, the amplifier 6's supply does not allow for the backscattering of a periodic signal; the initial output signal 11 is noise in this case, and therefore the oscillator 1 does not continuously or periodically emit an electromagnetic wave.Only when the amplifier unit 3 is sufficiently close to the diffuser 2a, 2b does the oscillator 1 generate oscillations and thus an identifiable periodic signal. Such a device 100 consumes little electrical energy, notably less than devices requiring a continuous periodic signal to detect the presence of a diffuser. It is also more discreet and less disruptive.

[0085] In another example, device 100 can be configured to identify a broadcaster 2a, 2b. In this case, broadcaster 2a, 2b is configured to backscatter the input signal 8 having the reference frequency Fref and exhibiting an electromagnetic field with a reference orientation. In this case, the receiving unit 5 has a polarization configured to receive a signal exhibiting an electromagnetic field with the reference orientation, and the processing unit 101 is configured to identify broadcaster 2a, 2b when a difference between the frequency of the input signal 8 determined by the processing unit 101 and the reference frequency Fref is less than or equal to a frequency threshold.

[0086] Figure 4 shows a variant of oscillator 1. In this variant, the oscillator includes several diffusers 2a, 2b, and, for example, an amplifier unit 3. This allows for multiple measurements of different physical parameters (e.g., temperature, humidity, a particular gas, etc.). In other words, several physical parameters can be measured simultaneously or independently. For example, oscillator 1 includes several diffusers 2a, 2b configured to backscatter several input signals 8, each with distinct frequency values. Furthermore, the processing unit 101 can be configured to identify the diffusers 2a, 2b when determining the frequency values. Such identification is similar to barcode identification. In other words, identifying multiple frequencies is equivalent to reading a barcode.

[0087] A method for generating periodic signals can also be provided, which can be implemented using the oscillator 1 and the apparatus 100 as described above. The method comprises providing the oscillator 1 and displacing the amplifier unit 3 of the oscillator 1 relative to the diffuser 2a, 2b of the oscillator 1.

Claims

22 DEMANDS 1. Oscillator, comprising: • at least one broadcaster (2a, 2b) configured to backscatter an electromagnetic signal from a received electromagnetic signal; and • an amplifier unit (3) comprising: i. a transmitting unit (4) configured to transmit an electromagnetic signal (7), referred to as the output signal, to said at least one broadcaster (2a, 2b); ii. a receiving unit (5) configured to receive an electromagnetic signal (8), referred to as the input signal, backscattered by said at least one broadcaster (2a, 2b) from the output signal (7) received by said at least one broadcaster (2a, 2b); and iii.an amplifier (6) having an input port (9) electrically coupled to the receiving unit (5) and an output port (10) coupled to the transmitting unit (4); the amplifier (6) being configured to amplify the input signal (8) received at its input port (9) and to provide, at its output port (10), an amplified signal corresponding to the output signal (7) transmitted by the transmitting unit (4) to said at least one broadcaster (2a, 2b); characterized in that the amplifier unit (3) is configured to transmit the output signal (7) and receive the input signal (8) by a wireless connection with said at least one broadcaster (2a, 2b).

2. Oscillator according to the preceding claim, wherein said at least one diffuser (2a, 2b) is a resonant diffuser configured to backscatter an input electromagnetic signal (8) having a specific frequency, said to be the resonance frequency.

3. Oscillator according to the preceding claim, in which the resonant frequency is between 10 MHz and 200 GHz.

4. Oscillator according to any one of the preceding claims, wherein at least one element, taken from said at least one diffuser (2a, 2b) and the amplifier unit (3), is configured to be movable relative to the other element between a first relative position (P1) of the amplifier unit (3) with respect to said at least one diffuser (2a, 2b), in which the amplifier (6) generates, at its output port (10), an initial output signal (11) and said at least one diffuser (2a, 2b) does not backscatter the input signal (8), and at least one second relative position (P2) of the amplifier unit (3) with respect to said at least one diffuser (2a, 2b), said at least one second position (P2) being distinct from the first position (P1), in which said at least one diffuser (2a, 2b) backscatters the input signal (8) to the receiving unit (5), and the amplifier (6) provides, at its output port (10), the amplified signal corresponding to the output signal (7) transmitted by the transmitting unit (4) to said at least one diffuser (2a, 2b).

5. Oscillator according to any one of the preceding claims, wherein the amplifying unit (3) comprises a phase shifter (12) electrically coupled in series with the amplifier (6).

6. Oscillator according to any one of the preceding claims, wherein the amplifier unit (3) comprises a filter (205) electrically coupled in series with the amplifier (6).

7. Oscillator according to any one of the preceding claims, wherein the receiving unit (5) is located at a distance (D3) from the transmitting unit (4), such that the receiving unit (5) does not receive the output signal (7) directly transmitted by the transmitting unit (4).

8. Oscillator according to any one of the preceding claims, wherein the transmitting unit (4) has a first polarization and the receiving unit (5) has a second polarization different from the first polarization.

9. Oscillator according to any one of the preceding claims, wherein the transmitting unit (4) and the receiving unit (5) form a single antenna (20), and the amplifier unit (3) comprises a radio frequency circulator (21) comprising first and second ports (B1, B2) coupled respectively to the input (9) and output (10) ports of the amplifier (6), and a third port (B3) coupled to the transmitting and receiving units of the antenna (20), the radio frequency circulator (21) being configured to transmit the amplified signal from the output port (10) of the amplifier (6) to the third port (B3) and to transmit the input signal (8) received, via the receiving unit (5), on the third port (B3) to the first port (B1) of the radio frequency circulator (21).

10. Apparatus for measuring at least one parameter of an electromagnetic signal, comprising an oscillator according to any one of the preceding claims, and a processing unit (101) configured to determine a frequency and amplitude of the input signal (8).

11. Apparatus according to the preceding claim, configured to determine a complex permittivity of a sample (102), wherein said at least one diffuser (2a, 2b) has a complex permittivity having a reference value for which said at least one diffuser (2a, 2b) backscatters the input signal (8) having a first frequency (F1) and a first amplitude (A1) as a function of the reference value, and when said at least one diffuser (2a, 2b) cooperates with a sample (102) such that the sample (102) modifies the value of the complex permittivity of said at least one diffuser (2a, 2b), said at least one diffuser (2a, 2b) backscatters the input signal (8) having a second frequency (F2) and a second amplitude (A2) distinct from the first frequency (F1) and first amplitude (A1),and the processing unit (101) is configured to determine the complex permittivity of the sample (102) as a function of a difference between the first and second frequencies (F1, F2) and a difference between the first and second amplitudes (A1, A2).

12. Apparatus according to claim 10, configured to determine a temperature of an environment (103), in which said at least one diffuser (2a, 2b) has a geometry and / or permittivity having a reference value for a reference temperature for which said at least one diffuser (2a, 2b) backscatters the input signal (8) having a first frequency (F1) as a function of the reference temperature, and when said at least one diffuser cooperates with an environment (103) having a temperature such that the environment (103) modifies the geometry and / or permittivity of said at least one diffuser (2a, 2b), said at least one diffuser (2a, 2b) backscatters the input signal (8) having a second frequency (F2) distinct from the first frequency (F1), and the processing unit (101) is configured to determine the temperature of the environment (103) as a function of a difference between the first and second frequencies (F1, F2).

13. Apparatus according to claim 10, configured to determine a humidity level, wherein said at least one diffuser (2a, 2b) has a permittivity having a reference value for a reference humidity level, for which said at least one diffuser (2a, 2b) backscatters the input signal (8) having a first frequency (F1) as a function of the reference humidity level, and when said at least one diffuser (2a, 2b) interacts with an environment (103) having a humidity level such that the environment (103) modifies the permittivity of said at least one diffuser (2a, 2b), said at least one diffuser (2a, 2b) backscatters the input signal (8) having a second frequency (F2) distinct from the first frequency (F1), and the processing unit (101) is 25 configured to determine the humidity level of the environment (103) based on a difference between the first and second frequencies (F1, F2).

14. Apparatus according to claim 10, configured to determine the presence of said at least one diffuser (2a, 2b), wherein at least one element, taken from said at least one diffuser (2a, 2b) and the amplifier unit (3), is configured to be movable relative to the other element, and when said at least one diffuser (2a, 2b) is located at a first distance (D1) from the transmitting unit (4) of the oscillator, said at least one diffuser (2a, 2b) does not backscatter the input signal (8), and when said at least one diffuser (2a, 2b) is located at at least a second distance (D2) from the transmitting unit (4) of the oscillator, said at least a second distance (D2) distinct from the first distance (D1), said at least one diffuser (2a, 2b) backscatters the input signal (8) having a reference frequency (Fret), and the processing unit (101) is configured to determine the presence of said at least one diffuser (2a,2b) when a difference between the frequency of the input signal (8) determined by the processing unit (101) and the reference frequency (Fret) is less than or equal to a frequency threshold.

15. Apparatus according to claim 10, configured to identify said at least one scatterer (2a, 2b), wherein said at least one scatterer (2a, 2b) is configured to backscatter the input signal (8) having a reference frequency (Fret) and presenting an electromagnetic field having a reference orientation, the receiving unit (5) of the oscillator has a polarization configured to receive a signal presenting an electromagnetic field having the reference orientation, and the processing unit (101) is configured to identify said at least one scatterer (2a, 2b) when a difference between the frequency of the input signal (8) determined by the processing unit (101) and the reference frequency (Fret) is less than or equal to a frequency threshold.

16. Apparatus according to the preceding claim, wherein the oscillator comprises several diffusers (2a, 2b) configured to backscatter several input signals (8) respectively having distinct frequency values, and the processing unit (101) is configured to identify the diffusers (2a, 2b) when the processing unit (101) determines the frequency values.

17. Method for generating electromagnetic signals, comprising supplying an oscillator according to any one of claims 1 to 9, characterized in that the method comprises a transmission, by the amplifier unit (3), of the output signal (7) and a reception, by the amplifier unit (3), of the input signal (8) by a wireless connection with said at least one broadcaster (2a, 2b).

18. A method according to the preceding claim, comprising a first relative positioning of at least one element, taken from said at least one diffuser (2a, 2b) and the amplifier unit (3), with respect to the other element in a first relative position (P1) in which the amplifier (6) generates, at its output port (10), an initial output signal (11) and said at least one diffuser (2a, 2b) does not backscatter the input signal (8) and a second relative positioning in at least a second relative position (P2), distinct from the first position (P1), in which said at least one diffuser (2a, 2b) backscatters the input signal (8) to the receiving unit (5), and the amplifier (6) provides, at its output port (10), the amplified signal corresponding to the output signal (7) transmitted by the transmitting unit (4) to said at least one diffuser (2a, 2b).

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