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    • 专利摘要:
    System and method for the diagnosis of antennas comprising a probe antenna (1) that is manually moved by an operator in front of the antenna under measurement (3) describing an arbitrary trajectory (7) that captures the radiated signal (2). It also includes a radio frequency unit (4) that measures the properties of said signal, positioning means (5) of the probe antenna (1), and a processing system that performs the diagnosis of the antenna under measurement (3). The method comprises defining a reference surface (15), moving the probe antenna (1) near the antenna under measurement (3), homogenizing the sampling, processing the information and performing a diagnosis by calculating the tangential component of the field. Applicable in those sectors in which the diagnosis of antennas is required, such as in the communications sector. It is of special interest in 5G networks. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2802304A1
    申请号:ES201900105
    申请日:2019-07-05
    公开日:2021-01-18
    发明作者:Narciandi Guillermo Alvarez；Martinez Jaime Laviada；Lopez Yuri Alvarez；Andres Fernando Las-Heras
    申请人:Universidad de Oviedo；
    IPC主号:
    专利说明:

    [0004] TECHNICAL SECTOR
    [0006] The present invention relates to a system and a method for e! antenna diagnostics using a portable device. The system comprises a probe antenna that is manually moved by the system operator along an arbitrary path and that captures the signals radiated by the antenna under measurement, a radio-frequency unit that measures the properties of said signal, a positioning means that provide the position of the probe antenna and a processing means that perform the diagnosis of the antenna under measurement from the data obtained. The method of the invention comprises defining at least one reference surface close to the antenna under measurement, moving the probe antenna along a trajectory, homogenizing the spatial sampling of the measurements, processing the information to obtain the representation of the electromagnetic field and diagnose the antenna.
    [0008] The invention is applicable in those sectors in which the diagnosis of antennas is required quickly, avoiding the use of large measurement systems, such as in the communications sector. In addition, it is of special interest in areas where antennas composed of many radiating elements are deployed, where the probability of failure of some component is not negligible. The invention allows the detection of radiating elements with anomalous behavior, which is an important aspect to guarantee the correct operation of a system. This situation is common in advanced communication networks, such as those involving picocells deployed for 5G networks.
    [0010] BACKGROUND OF THE INVENTION
    [0012] The diagnosis of antennas and radiant electromagnetic emission systems is a fundamental aspect to guarantee compliance with their specifications. Advances in telecommunications systems require antennas with more demanding requirements, reducing margins and design tolerances. As an example, we can cite the radio frequency technology of the new 5G communication systems, where in order to optimize coverage, it is intended to use telephone base stations equipped with smart antennas, that is, antennas capable of generating one or more beams that provide coverage to users connected to said base station. Likewise, more and more satellite communications systems use techniques based on beamforming and electronic scanning, where the antennas incorporate electronic and radio frequency circuits that allow modifying the aiming of the antenna beam in real time (for example, equipment antennas of on-board communications in moving vehicles that have to keep pointing towards a satellite). This means that the technology of diagnosis and characterization of antennas, capable of carrying out the measurement of these antennas in realistic operating conditions, has acquired more and more prominence
    [0014] In general lines, antenna diagnosis systems can be classified into outdoor systems or ranges, and indoor systems or ranges. Outdoor systems or ranges allow direct measurement of the radiation pattern of the antenna to be diagnosed, since it is possible to separate the antenna under measurement from the antenna that is used as a probe, so that far-field measurements are taken. The main drawbacks they present are fundamentally the great distance that is needed between the infrastructure where the antenna under measurement is placed and the probe antenna to be able to carry out the measurement in the far field. In addition, exposure to inclement weather conditions and limits its use.
    [0016] Indoor systems or ranges are typically located in fixed enclosures called anechoic chambers that, in order to minimize the reflection of radio waves on walls, floors, and ceilings, are entirely covered by a material that absorbs electromagnetic radiation. . Like the outdoor ranges, the antenna under measurement is placed on a fixed base or tower with the ability to describe turns, and the antenna that is used as a measurement probe is placed on another base or stationary tower at a certain distance from the first. .
    [0018] The electromagnetic field that radiates an antenna and / or radiating system can be classified mainly into two spatial regions: near field region, where the spatial distribution of radiated energy changes with distance to the antenna, and far field region, where the Spatial distribution of radiated energy does not change with distance to the antenna. Depending on the size of the antenna under measurement, the working frequency and the separation between the antenna under measurement and the measurement probe, the electromagnetic field Radiated by the antenna under measurement can be acquired in the near field or far field region. Typically, it is considered that if the conditions Rmeasure> 2D2 / A and Rmeasure> 10A are met, the electromagnetic field is measured in the far field region (where Rmeasured is the distance between the antenna under measurement and the measurement probe, D is the diameter of the minimum sphere circumscribed to the antenna under measurement and A is the working wavelength).
    [0020] The measurement of the radiation pattern of an antenna can only be carried out in the far field. If the antenna is measured in the near-field region, it is necessary to apply a near-field to far-field transformation method to obtain the radiation pattern from the measurements made, since in the near-field region the spatial distribution of radiated energy changes with distance. The methods of transformation from near field to far field are based on the calculation of a set of coefficients that allow modeling the electromagnetic field radiated by the antenna, as described in the state of the art of patent document ES 2639687 (B2) .
    [0022] Diagnosing an antenna in the near field region requires the measurement of both the amplitude and the phase of the electromagnetic field radiated by it. This requires measuring devices such as vector signal analyzers or two-channel receivers (phase and quadrature) or the use of a method for recovering the phase of the electromagnetic field.
    [0024] The diagnosis of antennas and radiant systems of electromagnetic emissions includes not only the characterization of the radiation pattern but also the detection of faults and defects in the antenna, being of special interest in the case of groups of antennas (or arrays), where the failure of a single element degrades the characteristics of the radiation pattern (for example, worsening parameters such as directivity or secondary lobe ratio). It is also applied to detect deformations in reflector type antennas. The detection of faults and defects in the antenna under measurement is carried out by characterizing the distribution of the electromagnetic field radiated at a distance as close as possible to its surface. From the representation of this field, it is possible to identify deformations or elements with incorrect operation.
    [0026] The systems currently used to measure antennas, which allow information to be retrieved for diagnosis, have several drawbacks, whether they are in the interior range or in the exterior range. In general, they are systems characterized by a high complexity, both constructive and operative, which restricts its implementation. On the one hand, they require a specialized, complex infrastructure with large-volume facilities. On the other hand, the personnel in charge of the measures must be specialized, with training and extensive knowledge in the matter. Furthermore, electro-mechanical elements are also necessary for the positioning of the antenna under measurement and the probe used in the measurement. Likewise, the configuration and precision of the positioning system is one of the determining factors that define the type of antennas that can be measured in a specific antenna measurement system.
    [0028] The development of positioning systems has made it possible to introduce systems based on robotic arms for the measurement of antennas, such as that described in patent US 20180368011 (A1) or in the document Gordon, JA, Novotny, DR, Francis, MH, Wittmann , RC, Butler, ML, Curtin, AE, & Guerrieri, J. R "Millimeter-Wave Near-Field Measurements Using Coordinated Robotics." IEEE Transactions on Antennas and Propagation, pp. 5351-5362, 2015, December. This document describes a system and method for the measurement of antennas using a positioner consisting of a robotic arm, which allows the measurement of the field radiated by the antenna under measurement in different measurement ranges (flat, cylindrical, spherical). The system has a positioning accuracy of less than 22 pm. Since for the diagnosis of an antenna it is required that the separation between two adjacent measurement points be equal to or less than half a wavelength at the measurement frequency when a detector capable of measuring amplitude and phase is used, and equal to or less than a quarter of a wavelength at the measurement frequency when using a detector capable of measuring only amplitude, the described system allows the measurement of antennas up to the frequency of 300 GHz. The main limitation of systems that use this type of positioner is the high complexity and cost of a robotic arm, which also requires to be handled by an expert operator.
    [0030] In the case of diagnosis of large antennas, different solutions have been proposed. Patent document ES 2639687 (B2) presents an airborne system and a method for the characterization and measurement of antennas or radiating systems, made up of at least one air module, an earth station and a communication system between elements. The invention also relates to the method of processing the radiated electromagnetic field to obtain both the radiation pattern and the field at the opening of the antenna for fault detection purposes. This system is designed for measurements in-situ, outdoors, of antennas in operating conditions (so that it is not necessary to interrupt the radiocommunication service for the antenna diagnostics), located in hard-to-reach locations that make the use of airborne systems convenient. The main limitations of this system and methods are, on the one hand, the maximum precision in the positioning and georeferencing of the measurements, which is specified in about 3 cm, which imposes an upper limit on the frequency of the antennas that can be diagnosed ( about 5 GHz is indicated). On the other hand, the use of an airborne system increases the complexity of the system and the specialization of its operators, comparable to that of a measurement range of antennas with mechanical moving parts.
    [0032] In A. Geise, O. Neitz, J. Migl, H.-J. Steiner, T. Fritzel, C. Hunscher, TF Eibert, "A Crane Based Portable Antenna Measurement System - System Description and Validation", IEEE Transactions on Antennas and Propagation, pp. 1-12, 2019, a system and method for the measurement of antennas is described where the probe used for the measurement of the radiated field, as well as the radiofrequency equipment, is embarked on a gondola hanging from a moving bridge crane above the antenna or radiant system under measure. The proposed system involves the acquisition of the radiated field on irregular measurement surfaces due to the nature of the movements described by the gondola. The system presents various limitations such as the need for a large infrastructure to support the gondola. Likewise, the management of the system is complex, since the design of the trajectory and the orientation of the probe antenna requires taking into account all the inertia of the nacelle, weight, frictions or accelerations among other aspects of its dynamics, such as and as the authors themselves mention in the article in which they present the system.
    [0034] In patent document US 20180351631 (A1) a mobile device formed by at least one pair of antennas is presented, one with horizontal polarization and the other with vertical polarization. The device also includes a position detector system, an electromagnetic field intensity detector, and an information processing unit. The device allows to obtain the position of each measurement, providing intensity maps of the signals radiated by the device under measurement, for example, a WiFi transmitter. Said patent document claims the ability to obtain specific parameters of the radiated signals, such as phase measurement and delay spread. However, the system is limited to generating intensity maps of the captured signals or measuring certain of their parameters without obtaining the radiation diagram or the diagnosis of the emitting element.
    [0035] In the document by H. He, P. Maheshwari, and DJ Pommerenke, “The development of an EM-field probing system for manual near-field scanning.", IEEE Transactions on Electromagnetic Compatibility, 58, 356-363, April 2016, A system and method for the diagnosis of electronic circuits is presented by means of the measurement of the electric and magnetic field radiated by the electronic components constituting them. The system consists of an optical positioning system that allows obtaining the position of the measurement probe of the electric and magnetic field at each measurement point. Said measurement probe is connected to a spectrum analyzer that allows acquiring the intensity of the electric and magnetic field, allowing its visualization in real time. However, the measurements obtained with the probe do not They are obtained with an adequate sampling or processed to determine the source of said radiation, but are simply represented by creating intensity maps of the emissions. s electromagnetic. This prevents, for example, the modeling of the field with simple elements such as base functions in terms of which the fields can be expressed in the aperture or radiation modes (eg expansion in spherical, plane or cylindrical waves) that allow Obtain more accurate representations of the radiant system operation, which prevents greater precision in the diagnosis of the antenna. For example, if the antenna is protected by a radome, this system would not allow obtaining the fields inside said radome.
    [0037] Patent document US 20180090837 (A1) presents a system and method to characterize the operation of active phased array type antennas and their behavior against temperature changes. For this, measurements of the near field radiated by the antenna under measurement are combined using an XYZ measurement range that uses an articulated robotic arm with thermal images captured by a thermal camera. The document claims the possibility of characterizing the amplitude and phase of each of the elements that make up the phased array antenna. Canonical acquisition domains are used in this system. However, the system requires the use of a complex infrastructure characterized by the use of an articulated robot. Likewise, it is a fixed, large system that is not indicated to characterize or diagnose antennas once deployed.
    [0039] In patent document US 9439092 (B1) a system and method for carrying out the diagnosis of mobile telephone antennas is presented. In this invention, heat maps are used to determine the elements or antennas that present an anomalous operation, given that the thermal image of the antennas is proportional to their emission power. The main disadvantage of this invention is that it is only useful in antennas that radiate sufficient heat. Furthermore, it does not allow obtaining the amplitude or phase of the field at the aperture, so it does not allow an adequate diagnosis of antenna groups. In addition, it also does not allow the measurement of the radiation pattern, that is, it does not allow an evaluation of the consequences of the anomalous operation of a radiating element, which could radiate in an acceptable way within the necessary specifications without requiring its repair or replacement.
    [0041] EXPLANATION OF THE INVENTION
    [0043] The present invention refers to a system for the diagnosis of antennas by means of measurements carried out by moving by hand and without mechanical restrictions at least one probe antenna in front of the antenna under measurement, acquiring the radiated signal at a set of arbitrary points. The system also includes positioning means capable of determining the position of the probe antenna used to capture the signal radiated by the antenna under measurement. The data acquired from the radiated signal, as well as the position where these acquisitions have been made, are processed by processing means that calculate information on the distribution of electromagnetic fields in the aperture of the antenna under measurement. In this way it is possible to evaluate if the amplitudes and phases in the opening are correct, as well as the characteristics of the far field.
    [0045] The invention also relates to a method for the diagnosis of antennas using the above system that comprises processing the measured values to obtain the field data on the aperture and the radiation pattern of the antenna under measurement.
    [0047] For the purposes of this invention and its description, antenna under measurement refers to the antenna that is analyzed and diagnosed to find possible anomalies in its operation.
    [0049] An object of the present invention is, therefore, a system for the diagnosis of antennas that comprises:
    [0051] - At least one probe antenna, which can be arbitrarily moved by hand by the person operating the system, which captures the signal radiated by the antenna under measurement when it moves along a path. The probe antenna captures at least one component of the electric field at the point where it is located.
    [0052] - A radio frequency (RF) unit that measures one or more of the properties of the signal captured by the probe antenna along a path.
    [0054] For the purposes of this invention and its description, the properties of the signal measured or captured refer either to the intensity and phase, or only to the intensity in the case that only one property of the signal captured by the probe antenna.
    [0056] - A positioning means that provide the position of the probe antenna along the path.
    [0058] - Processing means with at least one processor, a memory and a program or programs that are stored in the memory and that comprise a plurality of instructions. The processing means carry out the diagnosis of the antenna under measurement, processing the properties of the signal measured by the radio frequency unit combined with the position of the probe antenna provided by the positioning means.
    [0060] The probe antenna of the system is manually movable by an operator following an arbitrary trajectory, within an investigation volume. The research volume comprises a reference surface located at a distance between 1 cm and 100 cm from the antenna under measurement.
    [0062] For the purposes of this invention and its description, a reference surface is called a virtual surface near which the probe antenna that captures the signal radiated by the antenna under measurement moves.
    [0064] On the other hand, the processing means of the system comprise a plurality of instructions which, when executed by the processor, diagnose the antenna under measurement. This diagnosis is carried out by calculating at least the tangential component of the electric field, or the magnetic field or both, in the antenna aperture under measurement based on a representation by means of an expansion in base functions of the equivalent currents in the aperture or electric field modes obtained from the properties of the signal captured by the probe antenna associated with the position provided by the positioning means.
    [0065] In a preferred embodiment of the system, it comprises two probe antennas with orthogonal polarizations allowing the measurement of the signal radiated by the antenna under measurement for two independent polarizations. An example of a system capable of measuring two independent polarizations would be one comprising two antennas with orthogonal linear polarizations and an RF unit composed of two power detectors, each connected to a different antenna.
    [0067] In another preferred embodiment, the radio frequency unit measures both the phase and the intensity of the signal captured by the probe antenna. In a more preferred embodiment, the radio frequency unit comprises a portable vector network analyzer.
    [0069] An example of an RF unit capable of providing intensity and phase would be a vector network analyzer with at least two ports, with a wireless or wired interface that transmits the measurements made, together with an antenna that works as an electromagnetic field probe. . In this embodiment, one of the ports of the vector network analyzer would be connected to the probe, which could be moved by hand, and the other would be connected to the antenna under measurement.
    [0071] In another preferred embodiment of the system, the RF unit provides the intensity of the signal picked up by the probe antenna. In a more preferred embodiment, the radio frequency unit comprises a power detector. In another preferred embodiment, the radio frequency unit comprises a spectrum analyzer.
    [0073] An example of an RF unit that provides intensity would be a power detector connected to an antenna through an RF port and whose video output is connected to an analog-digital converter that sends its data to the processing system through a wireless interface. or wired as a serial or USB port. In this example, the RF unit would be composed of the power detector and the analog-digital converter together with the connection interface. Another example of an RF unit that provides the intensity of the radiated signal is a spectrum analyzer with an interface, such as a GPIB port, that transmits the data obtained and that is connected to the probe antenna or antennas using flexible radio frequency cables. .
    [0075] In another preferred embodiment of the system, the RF unit is capable of extracting the information from the acquired radiated signal allowing it to detect parameters thereof. An example of extraction of information from the radiated signal would be a system for diagnosis of antennas 5G capable of detecting and interpreting the Synchronization Signal Block (SSB) and measuring the intensity corresponding to each SSB, allowing an intensity to be assigned to each beam radiated by the antenna under measurement.
    [0077] In another preferred embodiment, the positioning means is an optical tracking system of the probe antenna along the path.
    [0079] In a more preferred embodiment, the optical tracking system comprises at least one infrared camera, or at least one visible spectrum camera, or at least one depth camera, or a combination of the foregoing. Even more preferably, the optical tracking system captures the movement of the probe antenna (s) by means of markers attached to the probe antenna (s), while the cameras are positioned in fixed positions.
    [0081] In another more preferred embodiment, the optical tracking system comprises a camera integrated in the probe antenna that captures successive images along the path. In one example, the captured images can be processed by photogrammetry. In another example, the integrated camera can be a depth camera, which measures point clouds continuously so that the position of the probe antenna can be obtained by comparing the differences between the point clouds.
    [0083] In another preferred embodiment, the positioning means comprise an ultrawideband (UWB) positioning system that estimates the position of the probe antenna along the path.
    [0085] In another preferred embodiment, the positioning means comprise an inertial sensor arranged on the probe antenna that provides the relative data of its position along the trajectory. Thus, for example, an inertial sensor can be embodied by an inertial measurement unit (IMU) equipped with accelerometers and gyroscopes.
    [0087] In a more preferred embodiment, the positioning means provide the position of the probe antenna from the inertial sensor data combined with the images captured by the integrated camera. For example, the positioning means can integrate a depth camera and an IMU. In this example, the position would be provided by applying the iterative closest point algorithm ( iterative closest point, or ICP) using as input the point clouds measured by the depth camera and the inclination detected by the IMU.
    [0089] In another preferred embodiment, the probe antenna and the RF unit are integrated into a single device. In a more preferred embodiment, the positioning means are integrated in the same device together with the probe antenna and the radio frequency unit.
    [0091] In an even more preferred embodiment, that device is a mobile phone. Thus, for example, the probe antennas of the system are those of a mobile phone; the RF unit is the communication system of said mobile phone, which measures the properties of the signal radiated by the antenna under measurement; the processing means is the mobile phone processing unit; and the positioning means are made up of the sensors of the mobile phone and its processing unit.
    [0093] In another preferred embodiment, the processing means comprise a plurality of instructions which when executed by the processor cause the processing means to be configured to execute the method for diagnosing antennas of the invention.
    [0095] In another preferred embodiment of any of the foregoing, the data processing subsystem also calculates the far-field radiation pattern of the antenna under measurement.
    [0097] Another object of the present invention is a method for the diagnosis of antennas by means of the previous system from data of the signal radiated by them. The method comprises the following stages:
    [0099] a) Define at least one reference surface based on the properties of the signal radiated by an antenna under measurement that the radio frequency unit is capable of measuring. The reference surface is located at a distance between 1 cm and 100 cm from the antenna under measurement.
    [0101] b) Move a probe antenna manually describing an arbitrary trajectory within a research volume. The research volume includes the reference surface. As the probe antenna moves, the signal radiated by the antenna under measurement is captured and its properties are measured by means of a radio frequency unit. The position of the probe antenna along the path is also determined.
    [0103] c) Homogenize the spatial sampling of measurements of the signal radiated by the antenna under measurement.
    [0105] For the purposes of this invention and its description, homogenizing spatial sampling refers to the establishment of a method that regulates the acquisition of data in arbitrary positions in such a way that a data set with a more balanced distribution is obtained, selecting a number of data maximum per unit volume that is within a preset range.
    [0107] d) Process the information acquired to obtain a representation of the electromagnetic field generated by the antenna under measurement as expansion in base functions.
    [0109] e) Diagnose the antenna under measurement by calculating at least the tangential component of the electric field, or the magnetic field, or both, in the aperture of the antenna under measurement. In this way it is possible to identify defective radiating elements.
    [0111] In a preferred embodiment of the method, the properties measured in step b) are both the phase and the intensity of the signal captured by the probe antenna and a single reference surface is defined.
    [0113] In a more preferred embodiment, the coefficients of the expansion in base functions of the electromagnetic field of step d) when both the phase and the intensity are measured are obtained by finding the coefficients that minimize the cost function
    [0115] CF ( x ) = \ Ax - b \ 2
    [0117] where CF is the cost function, b is a column vector with the field measurements, x is a vector with the coefficients of the fundamental elements, and A is a matrix containing the linear relationship between the base functions and the field measurements. An example would be the use of the Source Reconstruction Method ( SRM), which allows the representation of the radiated electromagnetic field by equivalent currents.
    [0118] In another preferred embodiment of the method, the property measured in step b) is the intensity of the signal captured by the probe antenna. In a more preferred embodiment, in step a) two reference surfaces are defined. In an even more preferred embodiment, the representation of the electromagnetic field generated from the expansion in base functions of step d) comprises the following substeps:
    [0120] di) Assign an arbitrary initial phase <p a to the data measured on the first reference surface.
    [0122] d.ii) Calculate the weights of the base functions as the coefficients that minimize the cost function
    [0124] CFi (x) = IMiX-faiHz
    [0126] where CF1 is the cost function, or a column vector with the field measurements on the first surface with the measured intensity and with phase <plt x a vector with the weights of the base functions and A 1 a matrix containing the linear relationship between the base functions and the field measurements in the first of the surfaces.
    [0128] d.iii) Calculate the field at the second reference surface from the expansion in base functions calculated in step d.ii) obtaining a phase vector <p2 corresponding to the field at the measured positions of the second reference surface.
    [0130] d.iv) Calculate the coefficients of the base functions, which will be those that minimize the cost function
    [0132] CF2 ( x) = \ A2x - b 2 \ 2
    [0134] where CF2 is the cost function, b2 is a column vector with the field measurements on the second surface with the measured amplitude and with the phase calculated in step d.iii), cp 2, x a vector with the weights of the base functions and A2 a matrix containing the linear relationship between the base functions and the field measurements on the first of the surfaces.
    [0135] d.v) Calculate the field at the first reference surface from the expansion in base functions calculated in step d.iv) obtaining a phase vector <p1 (corresponding to the field at the measured positions of the first reference surface.
    [0137] d.vi) Repeat steps from d.ii) to d.v) if at least one convergence criterion is not reached. Otherwise this algorithm stops.
    [0139] An example of a convergence criterion for stage d.vi) is that the number of iterations exceeds a set value. Another example of a convergence criterion is that the error is below a threshold given by:
    [0141] eO) = (1 - cO M i * - M 2 aWA2 * ~ b2 \ 2
    [0143] being a a parameter that balances the weight between the error on surface one and surface two. An example would be the use of the source reconstruction method without using phase information ( phaseless Sources Reconstruction Method, pSRM) that allows the representation of the intensity of the radiated electromagnetic field by means of equivalent currents, expressed by means of an expansion in base functions.
    [0145] In another preferred embodiment of the method, the homogenization of step c) comprises discretizing the investigation volume from the orthogonal projection at a distance h from some cells comprised in the reference surface or surfaces. In this way, a plurality of non-overlapping discrete volumes are configured, where the number of captures of the radiated signal does not exceed a certain threshold. When the number of measurements exceeds the threshold, they are discarded. For example, only two measurements of the signal radiated by the antenna under measurement could be retained for each discrete volume, so that there are no cells with a significantly greater number of measurements than other cells.
    [0147] In a more preferred embodiment, the reference surface is flat and the discrete volumes are straight or cuboid prisms.
    [0149] In another specific embodiment of the method, after step e), the method further comprises the step
    [0150] f) Calculate the radiation pattern of the antenna under measurement from the expansion in base functions obtained in step d).
    [0152] After stage e) this new stage is added in which the far field is calculated from the expansion in base functions using near field to far field transformation techniques.
    [0154] In another preferred embodiment of the method, the base functions of the expansion of the electromagnetic field model the electric and magnetic currents expressed as linear combinations of said base functions.
    [0156] In another preferred embodiment of the method, the base functions of the electromagnetic field expansion are electromagnetic field modes. An example of this would be the expansions in plane, cylindrical or spherical waves.
    [0158] In a specific embodiment of the above embodiment, the modes are planar waves.
    [0160] In another specific embodiment of the method, steps c), d) and e) are repeated for each of the beams radiated by the antenna under measurement. For example, a custom antenna with several beams would be a base station antenna of a 5G system that emits several beams. These beams can be identified and differentiated, and their intensity is measured in such a way that an expansion in different base functions is obtained for each beam.
    [0162] In another preferred embodiment of the method of any of the above, the step e) of field calculation on aperture is implemented by calculating the radiated field from the expansion in base functions. An example of calculating the field at the aperture in the case that the base functions are plane waves would be a backward propagation using plane-to-plane propagations. Another example of calculating the field in the opening in the case that the base functions are equivalent currents in the opening would be to use the equivalent currents in the opening since these already represent the tangential field in the opening.
    [0164] The invention provides, compared to other systems that are currently known, a system for diagnosing antennas that avoids the use of mechanical positioning elements or large auxiliary structures, thanks to the use of a probe antenna that can be operated manually and to a positioning means that follows the free movement of the probe antenna.
    [0166] The invention also provides a method that makes it possible to homogenize the sampled data, thus achieving greater flexibility, portability and rapid deployment of the system. Furthermore, the system and method avoid the need for an expert operator since they allow the system operator to perform the data acquisition without the need to previously define the path to follow and to move the probe antenna with a certain tolerance.
    [0168] Likewise, the system provides visual feedback in real time of the samples obtained, allowing the operator to know in which areas to increase the sampling. Compared to other inventions that do allow arbitrary movements, the present invention provides the ability to handle this arbitrary data and convert it into information related to the field at the opening, thanks to a correct spacing of the data, thus allowing to know the amplitude and phase of the radiated field. by the different elements of the antenna, even in those cases in which there is no physical access to the aperture, such as when the antenna is protected by a radome.
    [0170] The present invention is applicable in those sectors in which the diagnosis of antennas is required quickly, avoiding the use of large measurement systems, such as in the communications sector. Furthermore, it is particularly relevant in areas where many antennas are deployed, composed of many radiating elements, since the probability that some element of the transmitting chain, such as phase shifters or attenuators to model the beam, will suffer a failure is not negligible. An example of the latter scenario is the deployment of picocells working in millimeter band for 5G communications.
    [0172] BRIEF DESCRIPTION OF THE DRAWINGS
    [0174] Fig. 1 shows an embodiment of the system corresponding to that described in example 1. The figure shows the probe antenna (1), which is moved by the system operator with his hand in front of the antenna under measurement (3) describing an arbitrary trajectory (7), connected to a radio frequency unit (4) embodied in a portable vector network analyzer (13). The antenna under measurement (3) is connected to the other port of said portable vector network analyzer (13) so that it is possible to obtain both the amplitude as the phase of the radiated signal (2) by the antenna under measurement (3) at the different acquisition positions along the path (7). The positions of the probe antenna (1) in which measurements of the electric field radiated by the antenna under measure are made (3) are obtained by means of positioning means (5) materialized by an optical tracking system (8) formed by four infrared cameras (9) connected to processing means (6) represented by a computer that processes and controls the acquisition of data. The xyz coordinates and the inclination of the probe antenna (1) of the system are estimated by the optical tracking system (8) from the four markers (18) attached to the probe antenna (1).
    [0176] Fig. 2 shows another embodiment of the system corresponding to that described in example 3. In this case the radio frequency unit (4), the probe antenna (1) and the positioning means (5) are integrated in a 5G smartphone mobile phone , which moves describing an arbitrary trajectory (7) in front of the antenna under measurement (3). The radio frequency unit (4) is formed by the communication system of the smartphone ; the probe antennas (1) of the measurement system, in charge of acquiring the intensity of the radiated signal (2) by the antenna under measurement (3), are those of the smartphone: and the positioning means (5) are made up of the sensors inertials (10) and the depth camera (12) of the same phone. The acquired data is sent through a WiFi connection to a computer that forms the processing means (6) and that performs the diagnosis of the antenna under measurement (3).
    [0178] Fig. 3 represents two reference surfaces (15) defined for the characterization of an antenna under measurement (3) using only information on the intensity of the signal radiated (2) by it. The two reference surfaces (15) are defined in front of the antenna under measurement (3). For the homogenization of the spatial sampling of the measured data, both reference surfaces (15) are segmented into cells that are projected forming a plurality of three-dimensional discrete volumes (16) in the form of non-overlapping straight prisms, within which the number of field strength acquisitions. In this case, the projection of the field intensity acquisition positions on each reference surface (15) is represented by a black circle. In addition to spatial homogenization, these discrete volumes (16) make it possible to discard samples that are too far from the reference surfaces (15) beyond a certain tolerance given by the height h of the right prisms. The arbitrary trajectory (7) described by the probe antenna (1) is represented by a solid line ending in an arrowhead at each reference surface (15).
    [0179] Fig. 4 shows the basic flow chart of the method for diagnosing antennas with the system described in this invention. In the first place, the initialization of the system is carried out, which includes the definition of the reference surface or surfaces (15), as well as its segmentation into discrete volumes (16) that allow the spatial homogenization of the information acquired. Subsequently, the probe antenna (1) is moved in front of the antenna under measurement (3) manually describing an arbitrary trajectory (7) according to the reference surfaces (15) previously defined. During said movement, acquisitions of the radiated signal (2) by the antenna under measurement (3) (either intensity and phase or only intensity, depending on the capabilities of the radio frequency unit (4)) are made and the position of the probe antenna (1) in which said acquisitions have been made thanks to the information provided by the positioning means (5). Likewise, during the acquisition, the spatial sampling of the antenna field under measurement is homogenized (3) discarding those measurements acquired in positions that are outside the previously defined discrete volumes (16) or that have been acquired within a discrete volume (16 ) in which the maximum number of acquisitions has been reached. Finally, the field of the antenna under measurement is characterized (3) through its expansion in base functions calculated from the available measurements. Said characterization is updated, in a preferred embodiment of the method, as new measurements are obtained. Optionally, the far field radiated by the antenna under measurement (3) can be calculated and its field is modeled from the expansion in base functions.
    [0181] PREFERRED EMBODIMENT OF THE INVENTION
    [0183] For a better understanding of the present invention, the following preferred embodiment examples are set forth, described in detail, which should be understood without limiting the scope of the invention.
    [0185] EXAMPLE 1
    [0187] A system was materialized consisting of an RF unit (4) consisting of a portable vector network analyzer (13) connected by a port and a coaxial cable to an electric field probe antenna (1) consisting of a guide-type antenna open wave WR28 operating in the range 26.5 to 40 GHz (Ka band) that captures the radiated signal (2) by the antenna under measurement (3). The other port of the portable vector network analyzer (13) is used to inject RF signal to the antenna under measurement (3). This radio frequency unit (4) was capable of providing the amplitude and phase of the electric field in a polarization by measuring parameter S21. The connection of this subsystem was made through a LAN interface that allowed sending and receiving SCPI commands ( Standard Commands for Programmable Instruments).
    [0189] The positioning means (5) were materialized in an optical tracking system (8), consisting of 4 infrared cameras (9) connected by a switch to a computer that monitored 4 markers (18) attached to the probe antenna ( 1) electric field. The processing software provided the position in xyz coordinates as well as the inclination of the antenna through the inclination angles ( pitch, roll and yaw) along the trajectory (7).
    [0191] The processing means (6) were materialized in the same personal computer that processed the positioning data and that communicated with the portable vector network analyzer (13) using SCPI commands.
    [0193] EXAMPLE 2
    [0195] To carry out the method for the diagnosis of antennas, the system described in Example 1 was used. The method was applied by carrying out the following steps:
    [0197] a) A single reference surface was defined (15) consisting of a plane of size 15 cm x 15 cm and located parallel to 5 cm from the aperture of the antenna under measurement (3), since the radio frequency unit was capable of measure the amplitude and phase of the radiated signal (2) by the antenna under measurement (3).
    [0199] b) The operator continuously moved the electric field probe antenna (1) with his hand, describing an arbitrary trajectory (7) taking as a reference surface (15) the surface of step a) capturing the radiated signal (2) by the antenna under measurement (3), measuring its amplitude and phase, and determining the position of the probe antenna (1).
    [0201] c) The spatial sampling was homogenized by retaining the first two measurements of the electromagnetic field acquired within each discrete volume (16).
    [0203] d) The information acquired was processed to obtain a representation of the electromagnetic field generated by the antenna under measurement (3) in terms of currents magnetic, approximated by a linear combination of non-overlapping pulse-type base functions, in a 5 cm x 5 cm aperture by the following operation:
    [0205] x = A ^ b
    [0207] where b is a column vector with the measurements of the field, x a vector with the coefficients of the magnetic currents and A 1 the pseudo-inverse of the matrix A whose element of the m- th row and n-th column contains the field radiated by the function nth base at the m- th point where the field has been measured.
    [0209] The antenna under measurement was diagnosed (3) by calculating the magnetic field at the opening directly from the magnetic currents since they are already proportional to the tangential magnetic field.
    [0211] Steps from b) to e) were repeated continuously, allowing the currents in the aperture to be viewed as the operator moved the probe antenna (1).
    [0213] The reference surface (15) was divided into discrete volumes (16) formed by non-overlapping straight prisms of size 3.5 mm x 3.5 mm x 3.5 mm, with two of their faces parallel to the reference surface (15).
    [0215] EXAMPLE 3
    [0217] This example is oriented to the diagnosis of 5G active antennas in the 28GHz band. In this example, the radio frequency unit (4) of the system materialized in the communications system of a 5G smartphone with the capacity to detect the intensity of the different 5G beams emitted by the antenna under measurement (3) identified by the SSB blocks . The probe antennas (1) that acquired the radiated signal (2) were those of the mobile phone. The measured data is sent over a WiFi connection and together with a timestamp to a personal computer.
    [0219] The positioning means (5) were materialized in a depth camera (12) and an IMU (10), both belonging to the smartphone. Inclination data was obtained directly from the IMU (10). The position was obtained by calculating the relative xyz displacement between point clouds acquired by the depth camera (12), corrected for the inclination of the phone from the IMU (10) and processed by the Iterative Closest Point (ICP) algorithm. This data was processed in the CPU / GPU system of the smartphone and sent to a personal computer! via a WiFi connection along with a timestamp.
    [0221] The processing means (6) were materialized in a personal computer that received the data of the intensity of each beam emitted by the antenna under measurement (3) and of the positions of the probe antenna (1) provided by the positioning means (5 ).
    [0223] EXAMPLE 4
    [0225] To carry out the method for the diagnosis of antennas, the system described in Example 3 was used. The method was applied through the following steps:
    [0227] a) Two reference surfaces (15) were defined consisting of two planes of size 30 cm x 30 cm, located 5 cm and 15 cm, respectively, from the aperture of the antenna under measurement (3), since the unit of Radio frequency was only capable of measuring the intensity of the radiated signal (2) by the antenna under measurement (3),
    [0229] b) The operator continuously moved the electric field probe antenna (1) with his hand, describing an arbitrary trajectory (7) taking as reference surfaces (15) the surfaces of step a).
    [0231] c) The spatial sampling was homogenized by retaining the first two measurements of the electromagnetic field acquired within each discrete volume (16).
    [0233] d) An expansion in base functions consisting of plane waves was calculated following steps d.i) to d.vi) described in the method embodiments for each measured beam.
    [0235] e) The tangential field at the opening was calculated from the expansion in plane waves.
    [0237] f) The radiation pattern of the antenna under measurement (3) was calculated for each beam measured from the visible spectrum of plane waves, with the following expression:
    [0240] where r, Q and ( p are the spherical coordinates, k the wave number and f ( kx, ky ) the spectrum of plane waves.
    [0242] Steps from b) to f) were repeated continuously, allowing the currents in the aperture and the far field to be visualized as the operator moved the probe antenna (1).
    [0244] The reference surfaces (15) were divided into discrete volumes (16) formed by non-overlapping straight prisms of size 5 mm x 5 mm x 5 mm, with two of their faces parallel to the reference surfaces (15).
    权利要求:
    Claims (28)
    [1]
    1. System for the diagnosis of antennae antennas, comprising:
    - at least one probe antenna (1) that captures the radiated signal (2) by the antenna under measurement (3) when it moves along a path (7);
    - a radio frequency unit (4) that measures one or more of the properties of the signal captured by the probe antenna (1) along a path (7);
    - positioning means (5) that provide the position of the probe antenna (1) along the path (7);
    - processing means (6) with at least one processor, a memory and a program or programs that are stored in the memory and that comprise a plurality of instructions, which carry out the diagnosis of the antenna under measurement (3) by processing the properties of the signal measured by the radio frequency unit (4) combined with the position provided by the positioning means (5);
    characterized in that the probe antenna (1) is movable manually by an operator following an arbitrary trajectory (7) within a research volume, comprising a reference surface (15) that is located at a distance between 1 cm and 100 cm of the antenna under measurement (3), and because the processing means (6) comprise a plurality of instructions that when executed by the processor diagnose the antenna under measurement (3) by calculating at least the tangential component of the electric field, or the magnetic field or both, in the antenna aperture under measurement (3) based on a representation by means of an expansion in base functions of the equivalent currents in the aperture or electric field modes obtained from the properties of the signal captured by the probe antenna (1) associated with the position provided by the positioning means (5).
    [2]
    System according to claim 1, characterized in that it comprises two probe antennas (2) with orthogonal polarizations and a radio frequency unit (4) that measures one or more of the properties of the signal captured by each probe antenna.
    [3]
    System according to claim 1 characterized in that the radio frequency unit (4) measures both the phase and the intensity of the signal captured by the probe antenna (1).
    [4]
    4. System according to claim 3, characterized in that the radio frequency unit (4) comprises a portable vector network analyzer (13).
    [5]
    System according to claim 1, characterized in that the radio frequency unit (4) measures the intensity of the signal captured by the probe antenna (1).
    [6]
    6. System according to claim 5 characterized in that the radio frequency unit (4) comprises a power detector (14).
    [7]
    System according to claim 5, characterized in that the radio frequency unit (4) comprises a spectrum analyzer.
    [8]
    8. System according to claim 1 characterized in that the positioning means (5) are an optical tracking system (8) of the probe antenna (1) along the path (7).
    [9]
    System according to claim 8, characterized in that the optical tracking system (8) comprises at least one infrared camera (9) or at least one visible spectrum camera or at least one depth camera (12), or a combination of previous.
    [10]
    System according to claim 8 characterized in that the positioning means (5) comprise a camera (11) integrated in the probe antenna (1) that captures successive images along the path (7).
    [11]
    System according to claim 1 characterized in that the positioning means (5) comprise an ultrawideband positioning system (UWB) of the probe antenna (1) along the path (7).
    [12]
    12. System according to claim 1 characterized in that the positioning means (5) comprise an inertial sensor (10) arranged on the probe antenna (1) that provides relative data of its position along the trajectory (7).
    [13]
    System according to claims 10 and 12 characterized in that the positioning means (5) provide the position of the probe antenna (1) from the data of the inertial sensor (10) combined with the images captured by the integrated camera
    ( 11 ).
    [14]
    14. System according to claim 1 characterized in that the probe antenna (1) is integrated into the radio frequency unit (4).
    [15]
    System according to claim 14 characterized in that the positioning means (5) and the processing means (6) are integrated in the same device together with the probe antenna (1) and the radio frequency unit (4).
    [16]
    16. System according to claim 15 characterized in that the device is a mobile phone (19).
    [17]
    17. System according to claim 1, characterized in that the processing means (6) comprise a plurality of instructions that, when executed by the processor, cause the processing means (6) to be configured to execute the method according to any of claims 18 to 28.
    [18]
    18. Method for diagnosing antennas using the system of claim 1 comprising the following steps:
    a) define at least one reference surface (15) based on the properties of the signal radiated (2) by an antenna under measurement (3), where the reference surface (15) is located at a distance between 1 cm and 100 cm from the antenna under measurement (3);
    b) moving a probe antenna (1) manually describing an arbitrary trajectory (7) within an investigation volume that comprises the reference surface (15), capturing the radiated signal (2) by the antenna under measurement (3) and measuring its properties by means of a radio frequency unit (4), and determining the position of the probe antenna (1) along the path (7);
    c) homogenize the spatial sampling of measurements of the radiated signal (2) by the antenna under measurement (3);
    d) processing the information acquired to obtain a representation of the electromagnetic field generated by the antenna under measurement (3) as expansion in base functions;
    e) diagnosing the antenna under measurement (3) by calculating at least the tangential component of the electric field, or the magnetic field or both in the aperture of the antenna under measurement (3).
    [19]
    19. Method according to claim 18 characterized in that the properties measured in step b) are both the phase and the intensity of the signal captured by the probe antenna (1) -
    [20]
    20. Method according to claim 19, characterized in that the coefficients of the expansion in base functions of the electromagnetic field of step d) are obtained by finding the coefficients that minimize the cost function
    CF ( x) = \ Ax - b \ 2
    where CF is the cost function, b a column vector with the field measurements, x a vector with the coefficients of the fundamental elements and A a matrix containing the linear relationship between the fundamental elements and the field measurements.
    [21]
    21. Method according to claim 18 characterized in that the property measured in step b) is the intensity of the signal captured by the probe antenna (1).
    [22]
    22. Method according to claim 21 characterized in that in step a) two reference surfaces (15) are defined.
    [23]
    23. Method according to claim 22, characterized in that the representation of the electromagnetic field generated from the expansion in base functions of step d) comprises the following sub-stages:
    di) assigning an arbitrary initial phase <^ to the data measured on the first reference surface (15);
    d.ii) calculate the weights of the base functions as the coefficients that minimize the cost function

    [24]
    24. Method according to claim 19, characterized in that the homogenization of step c) comprises discretizing the research volume from the orthogonal projection at a distance h from cells comprised in the reference surface (15), thus configuring a plurality of non-overlapping discrete volumes (16), where the number of captures of the radiated signal (2) does not exceed a certain threshold.
    [25]
    25. Method according to claim 24, characterized in that the reference surface (15) is flat and the discrete volumes (16) are straight prisms.
    [26]
    26. Method according to claim 18 characterized in that after step e) it also comprises the step
    f) calculate the radiation pattern of the antenna under measurement (3) from the expansion in base functions obtained in step d).
    [27]
    27. Method according to claim 18 where the base functions of step d) model the equivalent currents at the aperture of the antenna under measurement (3).
    [28]
    28. Method according to claim 18 characterized in that steps c), d) and e) are repeated for each of the beams radiated by the antenna under measurement (3).
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    同族专利:
    公开号 | 公开日
    WO2021005250A1|2021-01-14|
    ES2802304B2|2021-05-18|
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