Methods and systems for air testing of millimeter-wave antenna arrays

Abstract

A system and method for (e.g., rapidly and inexpensively) testing an apparatus, such as an integrated circuit (IC) having an integrated antenna configured for millimeter-wave transmission and / or reception. The method may first perform a calibration operation on a reference device under test (DUT). The calibration operation may determine a set of fundamental frontier functions (FF) of the reference DUT and may also generate a set of calibration coefficients. Following the calibration step using the reference DUT, the resulting fundamental FF functions and calibration coefficients (or reconstruction matrix) of the reference DUT can be used to determine the far-field pattern of the DUT based on other field measurements (e.g., measurements performed in the near field of the DUT).

Description

[0001] Priority Statement

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 074,908, filed September 4, 2020, entitled “Over-the-Air Testing of Millimeter Wave Antenna Arrays,” inventors Martin Laabs, Dirk Plettermeier, Thomas Deckert, Johannes Lange, and Marc Vanden Bossche, which is hereby incorporated in its entirety as if fully and completely set forth herein.

[0003] By incorporating references

[0004] U.S. Patent Application No. 16 / 168,650, filed on October 23, 2018, entitled “Over-the-Air Testing of Millimeter Wave Integrated Circuits with Integrated Antenns,” is hereby incorporated in its entirety as if fully and completely set forth herein, and the inventors of that application are DaSilva et al. (U.S. Patent Publication 2019-0353698). Technical Field

[0005] This invention relates to the field of semiconductor testing, and more specifically, to the testing of millimeter-wave integrated circuits with integrated antennas. Background Technology

[0006] A key requirement for fifth-generation (5G) communication is the support for ultra-high data rates. One option to achieve higher data rates is to increase the system bandwidth by approximately 1-2 GHz. Continuous wide bandwidth is particularly available at higher millimeter-wave frequencies, such as 24 GHz and above. To overcome the high path loss at these frequencies, antenna array technology is used to redirect radiated energy in a specific direction.

[0007] Therefore, as fifth-generation (5G) wireless technology has become more prevalent, the importance of beamforming millimeter-wave technology has been rapidly growing. Current user equipment devices (e.g., cellular phones) use integrated circuits with integrated antenna arrays to transmit and / or receive millimeter-wave signals. These antenna arrays need to be characterized and subjected to over-the-air (OTS) testing to determine whether they meet various regulatory requirements.

[0008] Specifically, the challenges of implementing smartphones with millimeter-wave support are far greater than those of infrastructure components such as base stations, as high obstructions such as those by hand must be overcome. Therefore, each device requires multiple antenna-in-package (AiP) modules. If each advanced smartphone is assumed to have 3-4 AiP modules, this results in a test volume of >200M AiP units per year.

[0009] Such antenna arrays are typically characterized in an anechoic chamber with a distance R between the probe antenna and the device under test (DUT) to approximate the far-field (FF) conditions for electromagnetic wave propagation. One challenge of this testing method is that the required FF distance R is physically large, thus necessitating a large anechoic chamber size and consequently increasing testing costs. The minimum distance R for approximating the FF conditions depends on the antenna aperture D and wavelength λ as follows:

[0010] R = 2D 2 / λ

[0011] A larger antenna aperture obviously results in a larger far-field distance. For distances smaller than the far-field distance, the electric field may not be planar, and measurements may not accurately represent the far-field specifications required by regulations. Various miniaturized anechoic chambers and associated methods exist to reduce the size and cost of test equipment while creating FF conditions. However, the potential for such size reduction and cost reduction is limited.

[0012] Large testing capacity may benefit from entirely new testing methodologies. OTA testing using small-chamber-based methods would be prohibitively expensive. A viable approach should combine the ability to test a large number of devices with the possibility of correlating test results with device validation measurements at a reasonable price.

[0013] Current methods for testing antennas on these integrated circuits are slow, expensive, and / or have various drawbacks that prevent them from economically testing a sufficient number of antenna arrays. Improvements in the art are desired, particularly regarding the size, cost, and speed of test systems for automated production testing of devices and modules with integrated active antenna arrays. Summary of the Invention

[0014] The following presents various embodiments of systems and methods for (e.g., quickly and inexpensively) testing apparatus (such as integrated circuits (ICs) having integrated antennas configured for millimeter-wave transmission and / or reception).

[0015] The method can first perform a calibration operation on a reference device under test (DUT). The calibration operation can determine the set of fundamental functions of the reference DUT and can also generate a set of calibration coefficients.

[0016] The calibration step can determine the reference DUT FF fundamental function set by obtaining a set of reference DUT FF patterns generated by multiple antenna elements of the reference DUT under different beamforming settings. The reference DUT FF pattern set can be used to enable the calculation of any beamformer-specific FF pattern as a linear combination of this reference DUT FF pattern set. The reference DUT FF pattern set may include the reference DUT FF fundamental function set. The calibration step can generate calibration coefficients by obtaining a series of multiple reference DUT field measurements of the wireless signal generated by the reference DUT under different beamformer settings and processing said series of multiple reference DUT field measurements. In some embodiments, the calibration coefficients may be in the form of a matrix (referred to herein as a reconstruction matrix).

[0017] Following the calibration steps using a reference DUT, the resulting reference DUT FF fundamental function and calibration coefficients (or reconstruction matrix) can be used to determine the far-field pattern of the DUT based on field measurements that are not far-field (e.g., near-field measurements). Measurement operations can therefore include methods for determining the far-field (FF) pattern of the wireless signal generated by the device under test (DUT) based on non-far-field (e.g., NF) measurements and information generated during the calibration steps. The DUT may include an antenna array comprising multiple DUT antenna elements. The measurement (or runtime) method can operate as follows:

[0018] First, the measurement method obtains multiple DUT field measurements of the wireless signal generated by the DUT. These measurements can be performed by a probe antenna system (PAS) with multiple PAS antenna elements. The multiple PAS elements can be equal to or greater than the multiple DUT antenna elements. The measurement method then uses the multiple DUT field measurements and a set of calibration coefficients generated during the calibration phase to calculate a set of DUT FF scaling factors. The amount of the DUT FF scaling factor set can be equal to the amount of a set of reference DUT FF fundamental functions. In some embodiments, the calibration coefficients can first be converted to a reconstruction matrix format, and the reconstruction matrix is ​​used in place of the calibration coefficients. The measurement method can then determine (or estimate) the FF pattern of the DUT's wireless signal based on the DUT FF scaling factors and the set of reference DUT fundamental functions. The FF pattern of the wireless signal generated by the DUT can be used to evaluate the DUT's operation in FF.

[0019] The patterns generated by the DUT can be determined from wireless signals that can be unmodulated single-tone or multi-tone signals, or modulated signals. In modulated signals, modulation processing can affect the amplitude, frequency, and / or phase of the signal. Furthermore, these wireless signals can be continuous waves or intermittent waves, and can occupy narrow or wide bandwidths. Attached Figure Description

[0020] A better understanding of the invention can be obtained by considering the following detailed description of preferred embodiments in conjunction with the accompanying drawings, in which:

[0021] Figure 1 Examples illustrate over-the-air (OTA) test configurations according to some embodiments;

[0022] Figure 2 This shows a basic computer system block diagram;

[0023] Figure 3-4 Examples of test apparatus according to some embodiments are shown. The test apparatus may support or house a device under test (DUT) and may also include a probe antenna system (PAS) for measuring electromagnetic signals from the DUT.

[0024] Figure 5 Examples illustrating the field definitions related to wavelength and aperture size;

[0025] Figure 6 This illustrates the PAS that interacts with the DUT via an interface;

[0026] Figure 7 The front and back of an example embodiment of PAS are shown;

[0027] Figure 8 Examples illustrate the various types of coupling between PAS and DUT;

[0028] Figure 9 An example is given of a PAS antenna array without an absorption structure, which reveals the periodic mirror arrangement of the antenna elements.

[0029] Figure 10 An antipodal antenna with stripline-fed PAS is illustrated according to some embodiments;

[0030] Figure 11 Examples illustrate the relationship between far-field (FF) and near-field (NF) measurements, showing more specifically that for a given beamformer weight, the measurements in NF are proportional to the measurements in FF;

[0031] Figure 12 This section illustrates the PAS measurement process according to some embodiments;

[0032] Figure 13 This illustration demonstrates a PAS measurement system based on a vector network analyzer (VNA) for verifying the NF-FF reconstruction process, according to some embodiments; and

[0033] Figure 14A -B illustrates an example comparison of an NF-reconstructed FF pattern and a corresponding measured FF pattern according to some embodiments.

[0034] While the invention may have various modifications and alternative forms, specific embodiments thereof are shown by way of example in the accompanying drawings and are described in detail herein. However, it should be understood that the drawings and their detailed description are not intended to limit the invention to the specific forms disclosed, but rather, the invention is to cover all modifications, equivalents, and substitutions falling within the spirit and scope of the invention as defined by the appended claims. Detailed Implementation

[0035] acronym

[0036] The following is a list of acronyms used in this application:

[0037] DUT: Device Under Test

[0038] EIRP: Effective Isotropic Radiated Power

[0039] FF: Far Field

[0040] IF: Intermediate Frequency

[0041] NF: Close Range

[0042] OTA (Over-the-Air)

[0043] PAS: Detection Antenna System

[0044] RF: Radio Frequency

[0045] TRP: Total radiated power

[0046] VNA: Vector Network Analyzer

[0047] the term

[0048] The following is a compilation of terms used in this application:

[0049] Memory media – any of various types of non-transitory computer-accessible memory devices or storage devices. The term “memory media” is intended to include mounting media, such as CD-ROMs, floppy disks, or tape drives; computer system memory or random access memory, such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; non-volatile memory, such as Flash, magnetic media (e.g., hard disk drives), or optical storage; registers, or other similar types of memory elements. Memory media may also include other types of non-transitory memory, or combinations thereof. Furthermore, memory media may be housed in a first computer in which a program is executed, or may be housed in a different second computer connected to the first computer via a network (such as the Internet). In the latter case, the second computer can provide instructions to the first computer for execution. The term “memory media” can include two or more memory media that may reside in different locations (e.g., different computers connected via a network).

[0050] Carrier medium—the memory medium as described above, and physical transmission medium, such as buses, networks, and / or other physical transmission media for transmitting signals (such as electrical signals, electromagnetic signals, or digital signals).

[0051] Programmable hardware elements—including various hardware devices containing multiple programmable functional blocks connected via programmable interconnects. Examples include FPGAs (Field-Programmable Gate Arrays), PLDs (Programmable Logic Devices), FPOAs (Field-Programmable Object Arrays), and CPLDs (Complex PLDs). Programmable functional blocks can range from fine-grained (combinational logic or lookup tables) to coarse-grained (arithmetic logic units or processor cores). Programmable hardware elements can also be referred to as "reconfigurable logic."

[0052] A processing element is a component or combination of components capable of performing functions in a device, such as a user equipment or cellular network device. A processing element may include, for example, a processor and associated memory, a portion or circuitry of a single processor core, an entire processor core, a processor array, circuitry such as an ASIC (Application-Specific Integrated Circuit), programmable hardware components such as a Field-Programmable Gate Array (FPGA), and any combination thereof.

[0053] Software program – The term “software program” is intended to have the full breadth of its general meaning and includes any type of program instructions, code, scripts and / or data, or combinations thereof, that can be stored in a memory medium and executed by a processor. Exemplary software programs include programs written in text-based programming languages ​​such as C, C++, PASCAL, FORTRAN, COBOL, JAVA, assembly language, etc.; graphical programs (programs written in graphical programming languages); assembly language programs; programs that have been compiled into machine language; scripts; and other types of executable software. A software program may include two or more software programs that interoperate in some way. Note that the various embodiments described herein can be implemented by a computer or software program. A software program can be stored on a memory medium as program instructions.

[0054] Hardware configuration program – A program that can be used to program or configure programmable hardware components, such as netlists or bit files.

[0055] Program – The term “program” is intended to have its full breadth in its general sense. The term “program” includes 1) a software program that can be stored in memory and executed by a processor, or 2) a hardware configuration program that can be used to configure programmable hardware elements.

[0056] Computer system – any of various types of computing or processing systems, including personal computer systems (PCs), mainframe computer systems, workstations, network appliances, internet-connected appliances, personal digital assistants (PDAs), television systems, grid computing systems, or other devices or combinations thereof. Generally, the term "computer system" can be broadly defined as any device (or combination of devices) containing at least one processor that executes instructions from a memory medium.

[0057] A measuring device includes instruments, data acquisition devices, smart sensors, and any of various types of devices configured to acquire and / or store data. The measuring device may also be optionally further configured to analyze or process the acquired or stored data. The measuring device may also be optionally further configured to generate a signal generator for providing signals to the device under test. Examples of measuring devices include instruments such as traditional stand-alone “box-type” instruments, computer-based instruments (card-based instruments) or external instruments, data acquisition cards, external devices similar to data acquisition cards operating as data acquisition cards, smart sensors, modules or one or more DAQ or measurement cards in a base, image acquisition devices (such as image acquisition (or machine vision) cards (also known as video capture boards) or smart cameras), motion control devices, robots with machine vision, signal generators, and other similar types of devices. Exemplary “stand-alone” instruments include oscilloscopes, multimeters, signal analyzers, arbitrary waveform generators, beam splitters, and similar measurement, testing, or automation instruments.

[0058] The measuring device can be further configured to perform control functions, such as executing control functions in response to the analysis of acquired or stored data. For example, the measuring device can send control signals to external systems, such as motion control systems or sensors, in response to specific data. The measuring device can also be configured to perform automation functions, i.e., it can receive and analyze data and issue automation control signals in response.

[0059] A functional unit (or processing element) refers to a variety of elements or combinations of elements. Processing elements include, for example, circuitry such as ASICs (Application-Specific Integrated Circuits), portions or circuitry of a single processor core, an entire processor core, a single processor, programmable hardware devices such as field-programmable gate arrays (FPGAs), and / or larger portions of a system comprising multiple processors, and any combination thereof.

[0060] Wireless refers to communication, monitoring, or control systems in which electromagnetic or sound waves transmit signals through space rather than along wires.

[0061] "Approximately" refers to a value within a specified tolerance, error, or uncertainty of the target value, where the specific tolerance or margin generally depends on the application. Thus, for example, in various applications or embodiments, the term "approximately" may mean: within 0.1% of the target value, within 0.2% of the target value, within 0.5% of the target value, within 1%, 2%, 5%, or 10% of the target value, and so on, as required by the specific application of the present art.

[0062] A far-field (FF) pattern is a pattern of electromagnetic radiation that exists (or is assumed to exist) in the far-field region surrounding an object that generates electromagnetic radiation. Electromagnetic fields are created by signal-driven antennas or multiple antenna elements. Generally, the observed amplitude and phase of an electromagnetic field vary with the distance of the observer from the radiating object and the angular direction from the object to the observer. An FF pattern refers to the far-field pattern of the electromagnetic field around an antenna (or an object containing an antenna), and it is based on the fact that the amplitude and phase of these fields observed at a certain distance from the radiating object and acquired relative to a reference point at the same distance will be independent of the distance from the object. FF patterns, or gain, are well-known electromagnetic concepts.

[0063] A Probing Antenna System (PAS) consists of multiple antenna probes and possibly support components. It modifies the overall properties of the antenna probes and components toward the electromagnetic radiation associated with the wireless signal, and provides structural integrity to their assembly. It can also be used to measure the wireless signal generated by the DUT.

[0064] Probe-based field measurements or field detection measurements of wireless signals—electromagnetic field measurements performed using antenna probes that are part of a PAS. Measurements may include determining the amplitude and phase of the wireless signal present at the antenna probe. Multiple probe-based field measurements are an aggregation of measurements from all antenna probes belonging to the PAS, where all these measurements can be performed for the same one or more wireless signals present at the PAS. Here, "the same wireless signal" can mean that the arrangement and configuration of the DUT, the measuring instruments, the supporting equipment, and the surrounding environmental conditions are the same for all measurements performed with the antenna probes of the PAS. Different embodiments may choose to perform these measurements in various ways and in various orders; for example, measurements may be performed on all antenna probes simultaneously or in a sequential order. A series of multiple probe-based field measurements corresponds to multiplexing of multiple probe-based field measurements, each of which can be performed for a different wireless signal present at the PAS. When the source distance between the PAS and the wireless signal is near-field distance (either reactive near-field distance or radiated near-field distance), the field probe measurement can be a near-field probe measurement; when the distance is far-field distance, the field probe measurement can be a far-field probe measurement.

[0065] Figure 1 ——OTA Testing System

[0066] Figure 1 Examples of over-the-air (OTA) test systems configured to implement the techniques disclosed herein are illustrated according to some embodiments. Embodiments of methods for OTA testing (e.g., for production testing of integrated circuits) are described below. Systems and methods for OTA testing can utilize near-field to far-field (NF-FF) reconfiguration techniques as described herein.

[0067] It should be noted that various embodiments of the techniques disclosed herein can be implemented in a variety of different ways. For example, the methods described herein can be implemented by software that executes on a computer. However, while some embodiments are described based on one or more programs that execute on a computer, these embodiments are merely exemplary and are not intended to limit the techniques to any particular implementation or platform. Thus, for example, in some embodiments, the techniques can be implemented on or through functional units (also referred to herein as processing elements), which may include, for example, circuitry such as an ASIC (Application-Specific Integrated Circuit), a portion or circuitry of a single processor core, an entire processor core, a single processor, a programmable hardware device such as a field-programmable gate array (FPGA), and / or a larger portion of a system comprising multiple processors, and any combination thereof.

[0068] like Figure 1 As shown, the OTA testing system may include a computer system 72 coupled to the test device 84. Figure 1 In this design, the computer system is shown as a separate, independent computer system from the measurement base 83. The measurement base may be coupled to the test equipment 84. Alternatively, the computer may be implemented within the measurement base 83. For example, the computer may be implemented as a board or module inserted into a PXI (PCI eXtensions for Instrumentation) form factor. Any of various types of computer systems and / or base configurations may be used.

[0069] like Figure 2 As shown, computer system 82 may include a processor, random access memory (RAM), non-volatile memory, a display device, an input device, and an I / O interface for coupling to test device 84. For example, computer system 82 may include at least one memory medium thereon on which one or more computer programs or software components according to an embodiment of the present invention can be stored. For example, the memory medium may store one or more programs executable to perform the methods described herein. The memory medium may also store operating system software and other software for operating the computer system. Various embodiments further include receiving or storing instructions and / or data implemented according to the foregoing description on a carrier medium.

[0070] Test equipment 84 may include a structure designed to house a device under test (DUT). The DUT may be an antenna array chip, for example, a chip comprising multiple antennas, each antenna generating electromagnetic radiation. The DUT may also be user equipment (such as a cellular phone), or other chip or device having one or more antennas. The test equipment may also include a near-field signal (NF) measurement system (PAS) designed to be placed adjacent to the DUT for measuring electromagnetic signals generated by multiple antennas of the DUT. These measured NF signals are preferably not far-field signal measurements; in some embodiments, they are near-field (NF) measurements. Computer system 82 may be coupled to provide one or more stimulus signals to the DUT to selectively cause various antennas to generate electromagnetic radiation. The PAS may be configured to measure the NF electromagnetic signals generated by the DUT's antennas and may provide these measured NF electromagnetic signals to computer system 82 for processing.

[0071] exist Figure 1 In the illustrated embodiment, for ease of illustration, only a subset of the DUTs in test device 84 are shown as coupled to the measurement base (only a subset of the total number of wires between test device 84 and base 83 is shown). However, note that in a typical system, all antennas in the DUTs of test device 84 will be coupled to the measurement base 83.

[0072] Computer system 82 can execute the novel NF-FF reconstruction method described herein to measure and generate FF electromagnetic signal values ​​from received NF electromagnetic signals. The novel NF-FF reconstruction method is further described below.

[0073] Figure 2 —Computer System Block Diagram

[0074] Figure 2 A simplified block diagram illustrating computer system 82 is shown. As illustrated, computer system 82 may include a processor coupled to random access memory (RAM) and non-volatile memory. Computer system 82 may also include input devices for receiving user input and display devices for presenting output. Computer 82 may also include an input / output (I / O) interface coupled to test equipment 84. The I / O interface may be configured to supply signals to the DUT in test equipment 84 to selectively stimulate an antenna on the DUT to generate electromagnetic radiation. The I / O interface may be further coupled to PAS and configured to receive electromagnetic signals measured by PAS.

[0075] Figure 3-4 Test equipment

[0076] Figure 3 An embodiment of test equipment 84 is shown. Figure 4 More detailed examples Figure 3 Examples of implementations. As described above in Figure 1The points mentioned are merely for ease of illustration. Figure 3 and Figure 4 In this context, a subset or portion of the wires is shown as connected to the DUT. For example... Figure 3 As shown, the test apparatus 84 may include a mounting base configured to support or hold a PAS array for measuring near-field electromagnetic signals from the DUT. The test apparatus 84 may also include an absorber positioned around the PAS array to absorb unwanted electromagnetic signals during electromagnetic radiation measurements.

[0077] like Figure 4 As shown, the mounting base is also configured to support or hold the DUT below and adjacent to the PAS. The test device 84 may also include a first connector coupled to the DUT and also coupled to the computer system 82, enabling the computer system to provide a stimulation signal to the DUT, thereby causing an antenna on the DUT to generate an electromagnetic signal. The test device 84 may also include a second connector coupled to the PAS and also coupled to the computer system 82, enabling the computer system to receive the electromagnetic signal measured by the PAS.

[0078] Figure 5 —Field Definition

[0079] Figure 5 Examples illustrating various field definitions are provided. Two main distances play a crucial role in OTA measurements. The first is the distance R. NF and distance R FF At a distance R NF At a distance R, the reactance NF becomes the radiated NF. FF At that point, the radiation NF becomes (radiation) FF. For common OTA measurements, R FF This is the most relevant distance because it is the distance that can generally be assumed between the base station and the user terminal. Both distances depend on the antenna aperture size D and the wavelength λ, and are approximations. Details on how these boundaries are defined can be found, for example, in CA Balanis's book entitled "Antenna Theory – Analysis and Design".

[0080] If millimeter waves are used at 28 GHz (λ = c / f) C =(3) 8 m / s) / (28 9 If 1 / s = 0.0107m, then the following NF distance and FF distance can be obtained:

[0081] 1) D=λ / 2≈5.3mm→R NF =2.3mm; R FF =5.3mm

[0082] 2) D=10λ / 2≈5.3cm→R NF =7.4cm; R FF =53cm

[0083] It is immediately apparent that there is a significant difference between focusing on the single-element antenna represented in example (1) and focusing on the antenna array represented in example (2).

[0084] In a source antenna (FF), the electromagnetic field almost entirely comprises the component that causes the direction of the power flux to be strictly opposite to the direction pointed to by the radiation source (e.g., the antenna of the DUT); that is, the field may consist only of the radiation component. One consequence of this is that the shape of the spatial distribution of the field intensity, in terms of both amplitude and phase, may be almost independent of the distance between the radiation source and the observer. In other words, the distributions measured at two different distances in the FF may be (approximately) equal if normalized (e.g., normalized to their respective peak values); the actual scaling of the unnormalized distribution may still depend on the distance. This shape of the field intensity distribution is commonly referred to as the source antenna (FF) pattern and is an important characteristic of the radiating DUT. If the probe antenna can be placed in the FF of the DUT, the FF pattern of the DUT can be directly measured with the probe by repositioning the DUT and / or the probe relative to each other to multiple points on a sphere surrounding the DUT.

[0085] In the field of flux linkage (NF), the closer the observer is to the radiation source, the greater the influence of the reactive component on the electromagnetic field, causing a more significant portion of the power to travel back and forth between the radiation source and its point within the NF. This results in the spatial distribution of the field intensity, in terms of both amplitude and phase, depending on the distance between the source and the observer in both absolute value and shape. This also means that, in general, a probe antenna in the NF of the DUT antenna can be coupled to the DUT antenna, and its presence can alter the properties of the electromagnetic field radiated from the DUT.

[0086] Over-the-air (OTA) measurements in radiated nonlinear radiative (NF) are possible with low coupling between the probe and the DUT antenna, i.e., the presence of the probe antenna does not significantly alter the properties of the electromagnetic field radiated from the DUT (this is different in reactive NF, where there is more coupling and the probe antenna does not change the radiation properties of the DUT). Furthermore, the shape of the field strength distribution may still depend on the distance to the antenna.

[0087] However, FF data can be obtained using the classical NF-FF transform known from the literature. A drawback of this technique, especially for antenna arrays, is that the field must be spatially sampled, downsampled from approximately λ / 2 distance to λ / 10 distance, to obtain all the necessary information for applying the NF-FF transform. Furthermore, the classical NF-FF transform is computationally complex.

[0088] In the text, the unrestricted term "near field" (NF) includes both reactive NF and radiative NF.

[0089] Example

[0090] Embodiments of the present invention may include:

[0091] 1) Design of a non-far-field probe antenna system (PAS) for measurements performed in the non-far-field of the DUT. For example, some embodiments may be intended to operate in the radiation NF of a single antenna element (among multiple antennas in an active antenna array of the DUT) to enable the PAS to be positioned very close to the DUT based on the numerous wavelengths of the radio signal. Some embodiments may ensure that the PAS structure attenuates cross-coupling between adjacent antenna elements as much as possible. This design may specifically include particular absorber structures.

[0092] 2) The use of an NF-FF transformation method to reconstruct the FF pattern and related properties of the DUT antenna array from NF measurements by utilizing the linearity between specific measurements in NF and FF. The linear mapping relationship can be estimated during the calibration step and can be used for other antennas of the same type. The estimated mapping transforms the set of NF measurements into an equivalent FF pattern. In some embodiments, the linear mapping relationship can take the form of an NF-FF reconstruction matrix, and the superposition of single-element beam patterns can be used to transform the set of NF measurements into their equivalent FF form.

[0093] This combination of concepts allows for a very compact socket, similar to a test setup, where full-FF beam patterns, including amplitude and phase information, can still be measured, but without the need for a large, anechoic measurement chamber. This compact size enables OTA measurements to be performed in a small fraction of the space. It also has the potential for significant cost reduction, and due to the multiple antenna elements, it can significantly improve test time.

[0094] PAS Design

[0095] Figure 6 An example of a probe antenna system (PAS) positioned above (or mounted above) the DUT is illustrated. Figure 7 An embodiment of PAS is shown, wherein Figure 7 The left side shows the bottom of PAS. Figure 7 The right side shows the top of the PAS. In this embodiment, the PAS includes multiple (e.g., 16) probe antenna elements having SMPM RF connectors embedded in a solid-state RF absorbing material. Figure 6As shown, the PAS can be placed above the DUT in such a way that each antenna in the PAS is above its own or corresponding DUT antenna element, so that each antenna in the PAS is configured to measure the electromagnetic signal generated by its own or corresponding DUT antenna element.

[0096] Figure 8 This illustration demonstrates the direct path and unwanted coupling of transmission between the DUT and PAS. As shown, the direct path represents the desired coupling of electromagnetic signals between the PAS and the DUT, while "isolation" represents the unwanted coupling of electromagnetic signals between the PAS and the DUT. Therefore, as shown, for each measurement antenna element in the PAS, it is desirable to receive signals from its corresponding antenna on the DUT while minimizing interference from other non-corresponding antennas on the DUT.

[0097] The PAS can be designed to minimize disturbances to the input impedance of the individual component DUT antenna when measurements are performed using the PAS. Variations in antenna input impedance can be caused by the following effects:

[0098] 1. The dielectric loading of the antenna changes the field in the near field of the reactance, thus changing the input impedance.

[0099] 2. Signals from sources such as PAS are reflected back to the antenna, resulting in the superposition of the incident and reflected waves, thus changing the effective load impedance.

[0100] 3. When the array elements are excited by a phase / amplitude shifted input signal, the coupling between the elements changes, resulting in different superpositions of the incident signal and the coupled signal, thus changing the active load impedance.

[0101] In some embodiments, PAS may not necessarily significantly increase or decrease the coupling.

[0102] To aid in isolation between adjacent antennas and prevent reflections of signals transmitted from the DUT, the probe antenna can be surrounded by an absorbing material.

[0103] Different implementations can utilize various antenna structures from PAS to compare design guidelines and improve performance. Such antenna structures include, for example:

[0104] 1. Yagi antennas can help achieve high directivity with DUT antenna elements facing opposite directions, but metal guides may increase coupling between adjacent probe antennas and may increase near-field disturbances in reactance;

[0105] 2. The Vivaldi antenna allows for easy broadband operation with good matching over a wide frequency range and can reduce adjacent coupling, but its large aperture may increase the likelihood of reflection.

[0106] 3. Horn antennas can be advantageous due to the very good coupling between the DUT antenna elements and the PAS elements, as well as excellent isolation (especially with the dielectric filler). However, such filler may cause strong reflections from the PAS elements, thus excessively altering the DUT impedance.

[0107] PAS antenna elements and arrays are implemented in several ways. In some embodiments, the PAS array can be constructed from individual antenna elements. In other embodiments, multiple antenna elements can be implemented as a single module. Figure 9 In one particular embodiment shown, four components are arranged together on a single multilayer printed circuit board, and the entire array is constructed from four such modules.

[0108] In some embodiments, the PAS includes a pole antenna with an integrated balun. The pole antenna structure can be largely or mostly symmetrical, but the balun structure may introduce slight asymmetry. This can lead to non-uniform coupling in the unwanted DUT-PAS path. This non-uniform coupling does not significantly affect operation. Figure 9 As shown, in some embodiments, the PAS design includes a periodic mirrored arrangement of the antennas, which can solve this problem.

[0109] The design of the absorption structure between PAS antennas can incorporate absorbing materials, achieving a trade-off between isolation between PAS elements and (dielectric) loading of the DUT antenna. Too little absorbing material may result in insufficient isolation between PAS antenna elements. Too much absorbing material will cause the impedance of the DUT antenna to exceed a given limit. The shape of the absorbing material is as important as its volume. To achieve good absorption behavior and thus minimize reflected energy, the PAS design can include large surfaces that are not parallel to the direction of the electromagnetic radiation energy flux and / or at 90° angles.

[0110] In one embodiment, the PAS antenna can be directly cast into the absorbing structure. Direct casting of the antenna into the absorbing structure simplifies manufacturing. However, direct contact between the absorbing material and the RF transmission lines connecting the PAS antenna elements can increase losses on these transmission lines, especially for microstrip transmission lines.

[0111] If this is not desirable, another embodiment may leave a small non-absorber area in the absorber structure around and close to the RF transmission line.

[0112] Other embodiments can optimize RF transmission line loss in various other ways. One example could be using, for instance... Figure 10 The stripline transmission lines shown prevent electromagnetic fields from penetrating the absorbing material.

[0113] PAS receiver design

[0114] To perform measurements with PAS, it can be connected to a measurement receiver system that can be implemented in various ways. Some embodiments may choose to implement a parallel receiver circuit system, one for each PAS antenna element, to measure all PAS antenna elements simultaneously. An example is shown in Figure RA. Other embodiments may use a switched architecture, in which one receiver circuit is used to sequentially measure each of the PAS antenna elements. An example is shown in Figure RB.

[0115] The switching receiver design can employ a conventional "hard" switch, whereby only the signal picked up by one PAS antenna element is processed by the measurement receiver. An example is shown in Figure RB. Other embodiments of this variant can provide the ability to combine several or all of the signals from the PAS antenna elements, allowing the receiver to process the combined signals. Such combination can include circuitry that scales the amplitude and phase of the signals picked up by the PAS antenna elements separately, either before or during the combined processing. The scaling can be configured for each PAS antenna element, targeting both amplitude and / or phase. Specific embodiments of this method can use beamforming circuitry that is at least in principle similar to the beamforming elements used in the DUT. An example is shown in Figure RC. Such beamforming circuitry can use analog, digital, or hybrid techniques to achieve amplitude and / or phase changes.

[0116] Some embodiments implement the receiver system in a separate package from the PAS, with the two connected via cables, waveguides, or other means. An example is shown in Figure RB. Other embodiments may integrate the receiver system more extensively with the PAS antenna elements, allowing these parts to form a single package. An example is shown in Figure RC. It may also be advantageous to integrate only a portion of the receiver system with the PAS. For example, in a multi-stage receiver design, only the receiver section processing higher-frequency signals can be integrated with the PAS, while the processing stage for lower-frequency signals can be a separate entity connected to the former via cables, etc. An example is shown in Figure RA.

[0117] Some embodiments may implement the processing of measuring the raw output of the receiver system on another processing element, such as a computer system to which the receiver system is connected. Figures RA to RC illustrate this division. Other embodiments may include at least some of the processing utilizing the receiver itself, and may optionally use a dedicated circuit system to implement the processing.

[0118] Of course, an engineer skilled in the art will be readily able to design hybrid forms that utilize specific combinations of these basic methods. It is intended that all such embodiments be encompassed by this disclosure and the following claims.

[0119] PAF NF-FF Reconstruction Method

[0120] One aspect of NF-FF reconstruction is utilizing the linearity between NF and FF. In NF, the distribution of radiated field intensity can depend on distance, while in FF, the beam pattern is independent of distance, except that the amplitude scaling factor is inversely proportional to the distance. Figure 5 This is a schematic diagram depicting the NF and FF regions.

[0121] like Figure 11 As shown, field intensity-based measurements (E) in NF NF (w) is assumed to be for the same beamformer weights (w), DUT input signal and power (s) in Compared to field strength-based measurements in FF, and other relevant operating parameters (including temperature and humidity), ... FF (w) is proportional. The aforementioned conditions ensure that the radio signal (s(w)) generated by the DUT antenna element is the same for both FF and NF measurements. As mentioned above, at a position (θ) away from the DUT NF,m ,φ NF,m ,r NF,m The field distribution E in NF at a specific PAS antenna element (m, 1≤m≤M) at location M. NF,m It can be different from the field pattern E in FF FF (θ,φ). However, both depend on the same radio signal generated by the DUT, where the dependency takes the form of a linear relationship with the mapping on the FF side and the mapping on the NF side, the mapping on the FF side transforming the radio signal generated by the DUT antenna elements into their spatial representation (in the direction (θ)). p ,φ p The combined field strength effect at each point (p, 1≤p≤P) on the NF side is transformed into the combined field strength effect of the wireless signals generated by the DUT at different PAS antenna elements. Figure 11 Examples illustrate the exact parameters of these linear mappings and DUT operations (especially s). in It is independent of w) and depends only on the fixed intrinsic characteristics of the DUT and PAS (through the FF radiation characteristics of the DUT antenna elements (i.e., the pattern f of a single element)). FF,n (θ,φ), n, 1≤n≤N, and the coupling coefficient f between DUT and PAS NF,m,n (capture), and the spatial arrangement of the DUT and PAS relative to each other (the latter by the PAS position relative to the DUT (θ)NF,m ,φ NF,m ,r NF,m Changes in f affect the coupling. NF,m,n Therefore, the variations in the wireless signal generated by the DUT will be similarly measurable in both FF and NF, and there will be a constant scaling factor between various FF and NF measurements.

[0122] Used for FF measurement points (direction (θ)) p ,φ p The scaling factor for each combination of FF and NF measurement points (PAS antenna element m) can be determined by processing a series of FF measurements and a series of NF measurements, where both measurement series are performed using the same series of wireless signals generated by the DUT (a series of different values ​​for s(w)). When the number of PAS elements (M) equals the number of DUT antenna elements (N), it is sufficient to use N different wireless signals generated by the DUT. Some embodiments can create the desired different wireless signals generated by the DUT simply by changing the beamformer settings (w).

[0123] The aforementioned linear relationship between the field strength (NF) and field strength (FF) measurements can be applied to all wireless signals that the DUT can generate. Specifically, for signals covering a large frequency bandwidth, a scaling factor can be found for each specific frequency within that bandwidth, relating the NF and FF measurements. The scaling factor used for different such frequencies can be different. Some embodiments may choose to determine multiple sets of scaling factors corresponding to multiple frequencies of interest, so as to process the frequency-related measurement data using the associated set of scaling factors, and generate the broadband characteristics of the wireless signal generated by the DUT based on the intermediate results of the frequency-related processing.

[0124] During calibration, the reference DUT can be used to determine the reference DUT FF fundamental function and calibration coefficients. In some embodiments, the calibration coefficients may also be referred to as reconstruction coefficients or reconstruction matrices.

[0125] During measurement, calibration coefficients enable the determination of the DUT far-field scaling factor that can be applied to the reference DUT FF fundamental function. This allows establishing a correlation between the reference DUT FF fundamental function and probe-based field measurements, enabling the prediction of the DUT FF pattern from any probe-based field measurements for beamformer settings.

[0126] The far-field scaling factor of a DUT refers to a complex number used to scale the reference DUT's FF basic function to predict the corresponding FF pattern.

[0127] The reference DUT FF fundamental function can refer to a set of N patterns (preferably FF patterns) that can be used to create any other FF pattern. FF patterns are established when the reference DUT is driven by a beamformer setup. Assume the reference DUT has N antenna elements whose signal amplitude and phase can be controlled. Here, due to amplitude and phase control, the degrees of freedom for creating any FF pattern are equal to the number of antenna elements x2. This means that a series of N FF patterns (amplitude and phase) can be created from these patterns, from which any other FF pattern can be constructed for that reference DUT. These patterns are called the reference DUT FF fundamental function.

[0128] The ratio r can be determined for each DUT-PAS element link. n,m This will generate the reconstruction matrix as follows:

[0129]

[0130] The reconstruction matrix R (calibration coefficients) can be determined / estimated during the calibration procedure for a reference DUT. For DUTs of the same type, the reconstruction matrix can be constant, which is important for production test cases. Therefore, once R is obtained, the mapping can be computed by calculating the matrix-vector multiplication above. Due to design rules aimed at reducing cross-coupling between different DUT-PAS links, matrix R is assumed to be diagonally dominant.

[0131] Using the reconstruction matrix R, the DUT FF scaling factor c can be determined from multiple probe-based field measurements p using the following equation:

[0132]

[0133] If the DUT FF scaling factor c is calculated, then by utilizing the superposition principle, the single-element FF pattern is as follows, summing to form the total FF pattern:

[0134]

[0135] In some embodiments of the calibration process, for both FF and NF calibration measurements, only one DUT antenna element is used, while other DUT antenna elements can be turned off or attenuated as much as possible. Figure 11 As indicated, adjacent antenna elements can cause interference when they are not sufficiently attenuated. Although cross-coupling is reduced through the PAS design, the interference can be strong enough to negatively affect FF and NF single-antenna measurements, potentially causing the calibration factor c to become incorrect. This has been experimentally demonstrated. The effects of this interference can be compensated for by measuring the interference caused by the attenuated antenna and subtracting the interference from the measurement. Some embodiments may include algorithmic modifications to avoid single-antenna muting.

[0136] In some embodiments, the wireless signal generated by the DUT can occupy a wide bandwidth, such that the FF pattern (i.e., the distribution of radiated power in the space surrounding the DUT or equivalent distribution of the electric field strength) varies with frequency over the occupied bandwidth. Some embodiments may determine multiple sets of calibration coefficients, reference DUT fundamental functions, and DUT FF scaling factors, or otherwise characterize the frequency dependence of the NF-FF mapping. Various techniques can be used to determine these quantities, including frequency sweep analysis, multi-tone stimulus estimation, or NF-FF impulse response estimation. Some embodiments may use Fourier or other mathematical transform techniques to synthesize the wideband FF characteristics of the wireless signal generated by the DUT.

[0137] Phase measurements used to determine the fundamental function of the reference DUT FF are understood to be relative to a common reference. In some embodiments, the phase measurement may refer to a measurement of an accessible signal of the DUT's beamformer, the frequency of which is the same as the frequency of the electromagnetic field being measured, and is identical for determining the fundamental function of all reference DUT FFs. Other embodiments may refer to the phase of a wireless signal generated by the DUT at a fixed location.

[0138] Phase measurements of multiple probe-based field measurements or a series of multiple probe-based field measurements used to determine the wireless signal generated by the DUT are understood to be relative to a common reference. In some embodiments, the phase measurement may refer to a measurement of an accessible signal of the DUT's beamformer, the frequency of which is the same as the frequency of the electromagnetic field being measured, and is identical for determining the fundamental function of the FF of all reference DUTs. Other embodiments may refer to the phase of the wireless signal generated by the DUT at a fixed location.

[0139] The radiation of the wireless signal generated by the DUT can be single-polarized or dual-polarized. Some embodiments may determine calibration coefficients, reference the DUT FF basic function, and DUT FF scaling factor for a single polarization or each polarization to determine the FF pattern for a single polarization or each polarization.

[0140] Figure 12 —Reconstruction Algorithm

[0141] Figure 12 This is a flowchart illustrating one embodiment of a calibration and measurement task. As shown, the method includes... Figure 12 The calibration process, shown on the left-hand side, is first performed on a reference DUT, and the method also includes... Figure 12The DUT measurement process is shown on the right side. Therefore, the process for determining the far-field characteristics of the phased array DUT based on near-field indication using a probe antenna array (PAS) includes a calibration phase, followed by the actual measurement phase.

[0142] During the calibration phase, the relationship between the near-field PAS indication and the far-field E-field pattern of the DUT is established by quantizing the following two terms: the single-element far-field pattern and the calibration coefficients (also known as the reconstruction matrix) for a subset or all of the reference DUT elements (reference DUT FF fundamental function). These terms are quantized using measurements on a known good device (referred to as the reference DUT). Therefore, the calibration phase involves multiple far-field and near-field measurements on the reference DUT, resulting in a single-element far-field pattern (reference DUT FF fundamental function) and calibration coefficients (reconstruction matrix).

[0143] During calibration, a reference DUT can be placed in multiple beamformer setups and measurements can be performed. For example, one or more beamforming chips can be connected to the antenna panels in the reference DUT. These beamforming chips can be powered by signals (either RF, IF, or even baseband). These chips have the ability to control the signal power and phase of each signal entering each antenna panel internally. A beamformer setup refers to the aggregation of amplitude and phase settings of a beam resulting from the application of a signal to the beamforming chips.

[0144] The DUT measurement phase involves converting near-field indications from the PAS into far-field characteristics using a single-element far-field pattern (reference DUT fundamental function) and reconstruction coefficients (reconstruction matrix). In other words, the single-element far-field pattern and reconstruction matrix are applied to a series of DUTs (preferably of the same design as the reference DUT) for subsequent measurements. Measurements can be based on, for example, continuous wave monotones, multitones, or other wider bandwidth modulated stimuli.

[0145] like Figure 12 As shown, the calibration steps may include sub-steps 1-1, 1-2, 1-3, and 1-4, which are described in more detail below. Figure 12 As also shown, the DUT measurement steps may include sub-steps 2-1 and 2-2, which will be described in more detail below.

[0146] Phase 1: Calibration

[0147] As noted above, calibration can be performed using known good equipment (referred to as a reference DUT).

[0148] DUTs can operate in different ways, and some embodiments can apply general algorithms in a manner suitable for a particular DUT design. In this paper, two different DUT element control types are considered as examples. Control type 0 refers to a DUT where radiation from each individual element can be completely turned off. Control type ATT refers to a DUT where attenuation can be set for each element individually, where radiation from each element may not be completely turned off.

[0149] The following is an example method for measuring single-element far-field patterns as part of a calibration procedure.

[0150] Step 1-1: Procedure for measuring single-element far-field patterns (refer to DUT basic functions)

[0151] The following steps can be taken to measure the single-element far-field (E-field) pattern (amplitude and phase) f for all elements (n) of the reference DUT array. θ,int (θ,φ) and f φ,int (θ,φ). For a DUT with ATT control type: far-field disturbance pattern (amplitude and phase) f θ,int (θ,φ) and f φ,int (θ,φ). Far-field interference patterns may occur when, for example, a DUT is driving a single antenna element while other antennas are still radiating, thus causing interference with the electromagnetic signals being generated by the single antenna element being driven.

[0152] A. Install the reference DUT into the far-field measurement system.

[0153] B. For each polarization γ∈{θ,φ}

[0154] C. Align the polarization plane of the probe with the polarization γ.

[0155] D. For each direction (θ, φ) of the spatial sampling grid.

[0156] E. For control type ATT: Set the DUT element to the minimum possible radiation:

[0157]

[0158] F. For control type ATT: Measure the far-field E-field amplitude and phase, and record the results as a far-field disturbance pattern for polarized γ.

[0159]

[0160] G. For each DUT element n, n = 1, ...

[0161] H. Configure the DUT to radiate (primarily) from element n.

[0162]

[0163]

[0164] I. For control type ATT, measure the far-field E-field amplitude and phase:

[0165] Subtract the far-field interference pattern and record the result as the far-field pattern for element n and polarization γ.

[0166]

[0167] J. Once step 1-1 is completed, proceed to step 1-2.

[0168] In step B, if only a single polarization plane is of interest, for example, because the DUT is single-polarized, then measurements are performed only on that polarization. Polarization can be measured in parallel using a single spatial scan utilizing a dual-polarized probe antenna. In such cases, it can be ensured that...

[0169]

[0170] In step E, in the case of high loss and / or low output power in a far-field system, a fixed, but not minimal, setting may be beneficial for improving the signal-to-noise ratio of the measurement.

[0171] In step H, This can be the amplitude and phase settings for the radiating element n. Choosing a larger amplitude (corresponding to a larger radiated power) can improve measurement sensitivity.

[0172] In steps E and H, This can be the amplitude and phase settings that cause the "minimum possible radiation" from element n. For control type ATT, it can typically correspond to the minimum amplitude setting with a certain degree of freedom to select the phase setting that minimizes the overall uncertainty. For control type 0, it can be a setting that completely shuts off radiation from element n.

[0173] In steps E, F, and I, "minimum possible radiation" can be DUT-related. For a DUT design implementing control type 0, "minimum possible radiation" can mean "no radiation".

[0174] Steps 1-2: Procedure for measuring far-field reconstruction coefficients (calibration coefficients)

[0175] The following steps can be performed to set w for K beamformers. k For all elements of the reference DUT array, measure the far-field reconstruction coefficients (amplitude and phase) ck.

[0176] K. Install the reference DUT into the far-field measurement system.

[0177] L. The measurement system is tuned to measure the far-field E-field in a single fixed direction (θ0, φ0) using a probe aligned with a polarization γ∈{θ, φ}.

[0178] M. Select the number of measurements to be performed, K≥K min ,in

[0179]

[0180] N. Select K beamformer settings w k k = 1..., such that a certain DUT array element n k n k =1,…,N are the main radiations, i.e., the amplitude and phase settings w are selected. k (n k And ensure that other elements m≠n k Minimal level of radiation:

[0181]

[0182] And make w k Enough to be different from all other settings. l l≠k

[0183] O. Set w for each beamformer k , k=1…K,

[0184] P. Configure beamformer settings for DUT components. k

[0185] Q. For control type ATT, measure the far-field E-field amplitude and phase: subtract the direction (θ) 0,0 The far-field interference level on the φ0 direction is normalized to the pattern values ​​of the DUT elements in the direction (θ0, φ0), and the result is recorded as the far-field reconstruction coefficient c. k (n k )

[0186]

[0187] R. Once steps 1-2 are completed, proceed to steps 1-3.

[0188] Regarding step K, using the same far-field measurement settings as those used in measuring the single-element far-field pattern to measure the far-field reconstruction coefficients ensures that measurement distance, transmission line mismatch, and positional offset remain unchanged. Therefore, results from both processes can share the same reference, simplifying post-processing. Furthermore, the effects of some measurement uncertainties present in both steps can be eliminated.

[0189] In step L, the direction (θ) can be selected. 0,0 To optimize measurement sensitivity so that radiation from each of the components can be measured with negligible noise.

[0190] In step M, K min The number of unknowns in the process can be solved to determine the number of unknowns in the reconstruction matrix in steps 1-4.

[0191] In step N, w k (n k ) is for radiating element n k The amplitude and phase settings. Choosing a large amplitude (corresponding to a large radiated power) can improve measurement sensitivity. The same settings used in step 1-1 / E. Values ​​can be applied. "Distinct enough" means that the minimization problem solved in steps 1-4 is numerically stable.

[0192] In step Q, the interference pattern f γ,int (θ0,φ0) can come from step 1-1 / F, based on Single element pattern value f γ,k (θ0,φ0) can come from step 1-1 / I, based on

[0193] Steps 1-3: Procedures for measuring the near-field PAS response

[0194] The following steps can be taken to set w for K beamformers. k Measure the near-field PAS response (amplitude and phase) for all elements of the reference DUT array. k Here, the method obtains a series of probe-based field measurements of the wireless signal generated by the reference DUT.

[0195] S. Install the reference DUT into the near-field PAS measurement setup.

[0196] T. Allow the DUT and measuring instruments to reach a stable operating temperature.

[0197] U. For the beamformer settings selected in steps 1-2 / N, w k For each of k = 1, ..., K:

[0198] V. For control type ATT: Set the DUT element to reduce radiation.

[0199]

[0200] W. For control type ATT: Measure the near-field PAS response of all N PAS elements and record the results as a near-field disturbance indication vector.

[0201]

[0202] X. Configure beamformer settings for DUT components. k

[0203] Y. Measure the near-field PAS response of all N PAS elements and record the results in the original near-field PAS indicator vector.

[0204]

[0205] And recorded as the final near-field PAS indicator vector.

[0206]

[0207] Z. Once steps 1-3 are completed, proceed to steps 1-4.

[0208] Steps 1-4: The process for determining the reconstruction matrix

[0209] The following steps can be taken to determine the reconstruction matrix R and the regression residuals ε. Here, the method obtains calibration coefficients in the form of the reconstruction matrix.

[0210] To find the reconstructed matrix, the following minimization problem is solved.

[0211]

[0212] The function to be minimized is called the regression residual, and it is given by the following equation:

[0213]

[0214] If ε(R, {c off (m)})≤ε max If the calibration is successful, the DUT measurement in Phase 2 continues. Otherwise, the calibration is considered a failure.

[0215] In step X, the embodiment may use any of a number of numerical methods (including inverse matrix, pseudo-inverse matrix, least squares method, singular value decomposition, simulated annealing, differential evolution, and others). For example, for the general case of K≥N, the embodiment may follow R=CP. H (PP H ) -1 Find the reconstructed matrix from the pseudo-inverses of C and P.

[0216] In step X, {C off (m)} can represent the far-field response of the reference DUT's components, if disabled or set to minimum radiation, and can partially fill matrix C. For control level ATT: {C}off (m)} represents N additional unknowns. For control level 0: for all elements m, C off (m) = 0.

[0217] In step X, C = [c1, ..., c K ] is the N×K matrix of the far-field response, where c k This is given by the following equation:

[0218]

[0219] Where c k (n k From steps 1-2 / Q, {C off (m)} is defined as above.

[0220] In step X, P = [p1, ..., p K ] is an N×K matrix of near-field response, where p k From steps 1-3 / V.

[0221] {c k,k The correlation between {cl,pl} (k≠l) can be very low to ensure the numerical stability of the minimization problem.

[0222] Select limit value ε max Optimizing calibration can be beneficial for understanding the measurement uncertainty of the DUT. An example of such a limit could be ε. max =0.05, so that a relative error of no more than 5% for each DUT / PAS element can be used as a target.

[0223] Phase 2: DUT Measurement

[0224] A series of DUTs with the same design as the reference DUT can be measured. In step 2-1, the relationship of the DUT's beam pattern, established during the calibration phase, from the near-field indication from the PAS, can be determined. Other quantities of interest can be derived in step 2-2.

[0225] Step 2-1: The process of reconstructing the far-field beam pattern for the DUT

[0226] The following steps can be taken to determine the (beam) far-field pattern (amplitude and phase) E of the DUT array. θ (θ,φ) and E φ (θ,φ).

[0227] Z. Install the DUT into the near-field PAS measurement configuration.

[0228] AA. Configure some beamformer settings for the DUT components.

[0229] BB. Read the near-field responses from all N PAS elements and record them in vector p. Here, the method performs multiple probe-based field measurements of the wireless signal generated by the DUT.

[0230] CC. Calculate the DUT FF scaling factor c = Rp. Here, the method uses multiple probe-based field measurement and calibration coefficient sets to calculate the FF scaling factor set. In some embodiments, the amount of the FF scaling factor set is equal to the amount of the reference DUT FF fundamental function set. DD. Calculate the FF (far-field) beam pattern:

[0231] and

[0232]

[0233] Therefore, in step DD, the method determines the FF pattern of the DUT's wireless signal based on the DUT FF scaling factor and the reference DUT basic function set.

[0234] In step Z, the DUT can be positioned relative to the PAS in the same manner as the reference DUT was positioned relative to the PAS during calibration. In step CC, the reconstruction matrix determined in steps 1-4 can be used. In step DD, the single-element far-field pattern measured in step 1-1 can be used.

[0235] Step 2-2: The process used to derive other far-field quantities

[0236] The following steps can be taken to measure the total far-field amplitude of the E field in volts per meter (V / m); the effective isotropic radiated power (EIRP) in watts (W); the effective isotropic radiated power (EIRP) in decibels per milliwatt (dBm); the total radiated power (TRP) in watts (W); the total radiated power in decibels per milliwatt (dBm); and the directivity (D) in decibels of isotropy (dBi).

[0237]

[0238] Alternative methods for reconstructing DUT FF signals without interference suppression

[0239] The embodiments described above with reference to steps 1-1 to 2-2 illustrate the processing for reconstructing the FF DUT signal, which includes subtracting interference contributions between the different antenna elements of the DUT. The above method steps attempt to isolate the signal for each DUT antenna; however, perfectly isolating each antenna can be practically difficult. This can lead to some interference between antennas when, for example, a fundamental function of the reference DUT is measured and, as described above, this function is subsequently subtracted.

[0240] In another embodiment, an orthogonal beamformer weight set can be used to eliminate the cause of performing the interference subtraction. The method is described in detail below with reference to steps 1-1a to 2-1a. This alternative method is described to emphasize its difference from the method of performing interference subtraction. Therefore, for ease of explanation, some details of the method described below are omitted, as they have been described in sufficient detail above. In other words, the method described with reference to steps 1-1a to 2-1a can be combined with the relevant aspects, including this additional detail, described in steps 1-1 to 2-2.

[0241] The method described below refers to reconstructing the FF beam pattern for the DUT based on NF measurements. However, the described method can also be used, as needed, to reconstruct the FF beam pattern based on FF measurements.

[0242] Step 1-1a: The process of measuring the fundamental functions of the reference DUT to reconstruct the far-field pattern

[0243] The following steps can be taken to create a far-field (E-field) pattern (both amplitude and phase) for a given beamformer setup (w) and for all elements (n) of the measurement reference DUT array with two polarizations γ∈{θ,φ}. θ,w (θ,φ) and f φ,w (θ,φ). The far-field pattern may also include additional radiative portions of the DUT that are not directly controllable by a given beamformer setup. For example, other components of the DUT may emit thermal radiation or other types of radiation.

[0244] In some embodiments, the beamformer setup vector (w) is determined. i The set, the w i The collection results in a far-field (E-field) pattern (amplitude and phase) f θ,w (θ,φ) and f φ,wAn orthogonal basis of (θ, φ). Each beamformer setting vector w includes elements for each of the antenna elements of the DUT. For example, the method described above with reference to steps 1-1 to 2-2 utilizes a set of beamformer setting vectors, where each setting enables the radiation of one DUT antenna element and minimizes or disables the radiation of all other elements. More generally, the beamformer setting set can be selected such that the beamformer setting vector set spans the vector space of the beamformer setting set. In other words, the beamformer setting vector set can be selected such that any arbitrary beamformer setting vector can be constructed using a linear combination of the beamformer setting vector set. Advantageously, this can be achieved without setting the radiation of any DUT element to zero (which can be practically difficult to achieve) and can remove interference introduced by antenna elements that are never completely disabled. Therefore, an accurate FF beam pattern can be reconstructed without performing interference subtraction. In other words, each of the beamformer vectors w can include an amplitude that is perceptible for each of the DUT antenna elements, and at least one subset of the beamformer setup vectors can be orthogonal to each other such that a linear combination of the beamformer setup vectors can be used to obtain any desired beamformer setup vector. To achieve this, the number of beamformer setups can be at least equal to (or possibly greater than) the number of antenna elements on the DUT.

[0245] In some embodiments, a reference DUT can be mounted to a far-field measurement system. The far-field measurement system may include the mounted reference DUT and a far-field measurement probe. The reference DUT and measuring instruments are allowed to reach a stable operating state. For example, among other possibilities, they may be allowed to rest to achieve a stable operating temperature.

[0246] In some embodiments, for each polarization γ∈{θ,φ}, the polarization plane of the far-field probe is aligned with the polarization γ of the DUT. This can be done by physically rotating the DUT or FF probe by 90°, and / or it can be done by software (i.e., by changing the transmit and / or receive polarizations of the DUT and / or FF probe, respectively, through the circuitry of the DUT and / or FF probe). For orthogonal beamformer settings (w i For each beamformer setup in the set, and for each direction (θ, φ) from the spatial sampling grid, measure the corresponding far-field pattern f in an orthogonal beamforming setup. γ,i (θ,v).

[0247] Note that the order of operations for cyclic polarization and beamformer setup can be performed in any sequence, depending on the convenience and configuration of the DUT and / or FF probe. For example, the entire beamformer setup set can be measured for the first polarization before realigning with the second polarization and measuring the beamformer setup set. Alternatively, two polarizations can be measured for each beamformer setup as needed before proceeding to the next beamformer setup.

[0248] Step 1-2a: Procedure for measuring far-field reconstruction coefficients (calibration coefficients)

[0249] The following steps can be performed to determine the far-field reconstruction coefficient matrix R, which is used during measurement to determine the far-field scaling factors (amplitude and phase) for each of the fundamental functions of the reference DUT. k Each beamformer corresponding to an orthogonal beamformer is set with w k One of them. Matrix R can have rows corresponding to each beamformer setting in the beamformer setting (wi) set and columns corresponding to each probe antenna element of PAS (optionally, rows and columns can be switched as needed).

[0250] In some embodiments, a reference DUT can be mounted in a near-field PAS measurement setup. The reference DUT can be mounted such that it is configured to radiate toward the probe antenna system (PAS). The PAS can have at least the same number of probes as the number of antenna elements of the DUT. Among other possibilities, the reference DUT and measuring instruments can be allowed to reach a stable operating state, e.g., a stable operating temperature.

[0251] In some embodiments, for each polarization γ∈{θ,φ}, the reference DUT and PAS can be aligned for PAS to receive radiation from the reference DUT having polarization γ, and this can be repeated for each of the two polarizations. Measurement. For each beamformer setup (wi) used during the far-field characterization in steps 1-2a, the near-field PAS response can be measured for each probe element of the PAS, and the results are recorded in the original near-field PAS indication vector, where the subscript k indicates the specific beamformer setup wk:

[0252]

[0253] Set wk for each beamformer The combination includes the R matrix.

[0254] In some embodiments, when obtaining the near-field PAS indication vector At this time, the same input power to the DUT used when measuring the fundamental function of the reference DUT can be used, enabling absolute far-field reconstruction for arbitrary power and avoiding the adverse effects of beamformer characteristics scaling with input power on reconstruction accuracy. Advantageously, once the R matrix is ​​obtained, the FF pattern of the DUT can be reconstructed using arbitrary input power in step 2-1a.

[0255] Step 2-1a: The process of reconstructing the far-field beam pattern for the DUT

[0256] The following steps can be taken to determine the far-field beam pattern (amplitude and phase) of the DUT array based on near-field PAS measurements, setting w for any arbitrary beamformer. θ (θ,φ) and E φ (θ,φ).

[0257] In some embodiments, the DUT is mounted in the near-field PAS measurement configuration in the same manner as the reference DUT is positioned relative to the PAS during calibration in steps 1-2a. The DUT antenna element is configured with a beamformer setting w.

[0258] In some embodiments, the near-field response is read from all probe-based elements of the PAS and recorded in vector p. Here, the method performs multiple probe-based field measurements of the wireless signal generated by the DUT. For example, as... Figure 8 As shown, each antenna element of the DUT transmits its own signal according to the configured beamformer settings w, and each detector element of the PAS receives its own signal generated by the DUT antenna element set.

[0259] In some embodiments, the DUT FF scaling factor c = Rp is calculated. Here, the method uses multiple probe-based field measurement and calibration coefficient sets to calculate the FF scaling factor set. The size of the FF scaling factor set is equal to the size of the reference DUT FF fundamental function set.

[0260] In some embodiments, the FF (far-field) beam pattern is calculated according to the following equation:

[0261]

[0262]

[0263] Where index i is set in the beamformer (w) i The summation is performed on each of the M beamformer settings used to measure the basic functions of the reference DUT (note that M can be equal to or greater than the number of antenna elements N of the DUT), where the subscripts {θ,φ} refer to the polarization of the electric field, and the function arguments (θ,φ) specify the angular position of the reconstructed far-field beam pattern.

[0264] Determine the phase reference for the DUT signal

[0265] When a signal is received from the DUT (either via an FF probe or a PAS), phase information of the received signal is recorded in addition to amplitude information. Typically, this phase information is compared to a reference phase to provide a coherent reference point for phase information. In some embodiments, the DUT may receive an input signal transmitted by a stimulus having the same frequency as the transmitting DUT signal. In these embodiments, the phase of these input signals can be used as a reference phase. For example, the phase of the electromagnetic field of the received reference DUT FF pattern (or alternatively, multiple received probe-based field measurements) can be referred to as an accessible signal of the beamformer at the same frequency. This reference phase can be the same for determining the fundamental function of all reference DUT FF patterns.

[0266] Alternatively, in some embodiments, the DUT may receive a baseband or intermediate frequency input signal, which is up-converted to generate a radio frequency (RF) transmittance. In this case, an input signal with the same frequency as the output transmittance may not be accessible to obtain a reference phase. To address this issue, a reference phase can be obtained using a reference probe located at a fixed point that also receives the transmittance from the DUT. For far-field transmittance, a fixed reference probe can be used while the FF signal is measured. For measurements utilizing a PAS, one of the antenna elements of the PAS can be used as a reference to obtain the reference phase, while the other antenna elements are measured.

[0267] System for measuring far-field patterns

[0268] To measure single-element far-field patterns for all DUT elements, a suitable system needs to be configured.

[0269] The reference antenna can be used to receive the radiated signal from the DUT in the far field and to measure the single-element radiation pattern (in the far field or near field using an optional near-field to far-field transformation).

[0270] Some embodiments may use an additional amplifier behind the probe antenna to compensate for power consumption between the DUT and the probe antenna, as well as in potentially long cables and other connector-type devices, thereby improving the signal-to-noise ratio of the measurement.

[0271] The DUT array beamformer settings can be selected to cover all phase settings from 0° to 360° (or a subset thereof, depending on the desired FF characteristics to be measured and the DUT). In some embodiments, the beamformer settings can be selected to result in high output power for each DUT antenna element to ensure low noise associated measurement errors.

[0272] In some embodiments, interference from other elements besides the target DUT antenna element can be compensated during measurements of the target DUT antenna element. The beamformer setting for such other elements (“off” elements) can be selected to result in low power output from such elements to minimize the impact of interference on the measurement. In some embodiments, either additionally or alternatively, the phase setting for the DUT antenna element can be selected to improve the quality of interference compensation. For example, the phase setting for “off” elements can make the power level of the combined interference large enough to allow for good measurement of the interference effect itself. In another example, the phase setting for “off” elements can make the interference “deflected” from the measurement probe to reduce the impact of interference on the measurement of the target element. In some embodiments, the selection of the beamformer setting for “off” elements can (additionally or alternatively) be based on further constraints, such as possible DUT operating modes, DUT input and antenna impedance variations, and other factors.

[0273] FF pattern measurements can be performed using any of a variety of techniques, and all data can be normalized electric field strength at a distance of 1 meter.

[0274] System for measuring near-field radiation on a DUT

[0275] One or more phase-aligned VNAs can be used to measure near-field radiation on the DUT. The test ports of the VNA can be connected to multiple antenna probes on the PAS. Specifically, some embodiments can measure the amplitude and phase of the signal received on some or all of the test ports of the VNA, and these amplitudes and phases can be calibrated so that they reflect the amplitude and phase of the wireless signal generated by the DUT.

[0276] The signal driving the DUT input can be obtained from the VNA. Figure 11 (sin in). Some embodiments may open a source loop on one of the VNA test ports, feed a source signal to the DUT input, may appropriately terminate the open connection with the directional coupler (typically with a 50-ohm load), and / or may use the receiver of the VNA test port to perform a measurement on one of the PAS antenna elements.

[0277] The same wk vector as the wk vector in the FF measurement configuration (i.e., beamformer settings) can be used.

[0278] The input power of the DUT can be equal to or different from the far-field configuration, which may not affect the reconstruction algorithm because normalization can remove any absolute power relationship.

[0279] If the same settings and VNA are used for calibrating and reconstructing measurements, some embodiments may choose not to calibrate the VNA.

[0280] Figure 13 This illustration demonstrates a VNA-based PAS measurement system used to verify the NF-FF reconfiguration process. For experimental verification, a 4×4 antenna array DUT prototype is used. The PAS-DUT is fixed on the right side of the figure. Because the VNA used in verification only provides four separate ports for measurement, the verification shows the results for a 2×2 subarray of the antenna array DUT.

[0281] Figure 14A -B shows the results in terms of beam pattern. The solid curve represents the FF reference measurement for a specific beam configuration (beamformer setting). The dashed curve shows the reconstructed FF pattern based on the NF PAS measurement applied to the NF-FF reconstruction process described above.

[0282] Although the embodiments described above have been described in considerable detail, many variations and modifications will become apparent to those skilled in the art once the above disclosure has been fully appreciated. It is intended that the claims be construed as encompassing all such variations and modifications.

Claims

1. A method for determining a far-field (FF) pattern of a wireless signal generated by a device under test (DUT), wherein the DUT includes an antenna array comprising a plurality of DUT antenna elements, the method comprising: Multiple probe-based field measurements are obtained of the wireless signal generated by the DUT, wherein the wireless signal generated by the DUT is generated according to a multiple beamformer configuration set of the multiple DUT antenna elements, and wherein the multiple beamformer configuration set spans the vector space of the beamformer configuration set. The FF scaling factor set is calculated using the plurality of probe-based field measurement and calibration coefficient sets, the amount of which is equal to the amount of the reference DUT FF basic function set; The FF pattern of the wireless signal is determined based on the FF scaling factor and the reference DUT FF basic function set; The FF pattern of the wireless signal generated by the DUT can be used to evaluate the operation of the DUT in the FF.

2. The method according to claim 1, The acquisition is performed by a probe antenna system (PAS) having a plurality of PAS antenna elements, wherein the plurality of PAS elements is equal to or greater than the plurality of DUT antenna elements.

3. The method according to claim 1, The multiple field measurements used to obtain the wireless signal generated by the DUT include: While driving the beamformer with a signal, some beamformer settings are configured for multiple antenna elements of the DUT; as well as The amplitude and phase of multiple electromagnetic fields generated by the multiple antenna elements of the DUT are measured at at least one frequency.

4. The method according to claim 1, further comprising: The reference DUT FF basic function set is determined by the following steps: A set of reference DUT FF patterns generated by multiple antenna elements of a reference DUT under different beamformer settings is obtained, such that the set of reference DUT FF patterns can be used to enable the calculation of FF patterns specific to beamformer settings as linear combinations of the set of reference DUT FF patterns. The reference DUT FF pattern set is the reference DUT FF basic function set; as well as The calibration coefficients are generated through the following steps: A series of field measurements based on the reference DUT probes were obtained to obtain the wireless signals generated by the reference DUT under a set of different beamformer settings; and The series of field measurements based on the reference DUT probes are processed.

5. The method of claim 4, wherein the series of field measurements based on the reference DUT probe are processed by applying singular value decomposition.

6. The method of claim 4, wherein obtaining the set of reference DUT FF patterns generated by the plurality of antenna elements of the reference DUT under the different beamforming settings comprises: For each antenna element n of the reference DUT: The reference DUT is configured to radiate primarily from the antenna element n using at least one beamformer setup; as well as Measure the far-field electromagnetic amplitude and phase generated by the antenna element n at at least one frequency. The measurements of the far-field electromagnetic amplitude and phase generated by the antenna element n using the at least one beamformer result in a reference DUT fundamental function for the antenna element n.

7. The method of claim 6, further comprising: For each antenna element n of the reference DUT: To minimize the radiation of the multiple antenna elements of the reference DUT; Measure the electromagnetic amplitude and phase of the FF to determine the FF interference pattern; The far-field electromagnetic amplitude and phase generated from the antenna element n using the at least one beamformer are subtracted from the FF interference pattern.

8. The method of claim 4, wherein obtaining the series of field measurements based on the plurality of reference DUT probes of the wireless signal generated by the reference DUT under the set of different beamformer settings comprises: For each antenna element n of the reference DUT: The reference DUT is configured to radiate only from the antenna element n at at least one frequency using the set of different beamformer settings; as well as The field measurements generated by the antenna element n at at least one frequency using the plurality of reference DUT probes are performed.

9. The method of claim 8, further comprising: For each antenna element n of the reference DUT: To minimize the radiation of the plurality of antenna elements of the reference DUT; Measure the field measurements of the multiple reference DUT probes to determine probe-based interference indications; The interference indication is subtracted from the plurality of field measurements based on the reference DUT probe generated from the antenna element n for the at least one beamformer setting.

10. The method according to claim 4, The reference DUT FF pattern set includes phase and amplitude information, and the method further includes: Obtain multiple fixed reference FF measurements of the plurality of antenna elements of the reference DUT under the set of different beamformer settings; The phase information measured by the plurality of fixed reference FFs is used to obtain a reference phase for the phase information of the reference DUT FF pattern set.

11. The method according to claim 4, The reference DUT FF pattern set includes phase and amplitude information, and the method further includes: Phase information is extracted from the input signal that drives the wireless signal generated by the DUT; The phase information of the input signal is used to obtain a reference phase for the phase information of the reference DUT FF pattern set.

12. The method according to claim 1, The probe-based field measurement is obtained in the near field (NF) of the DUT.

13. The method according to claim 1, The plurality of beamformers are arranged in an array that is equal to or greater in number than the plurality of DUT antenna elements.

14. The method according to claim 1, The plurality of probe-based field measurements include phase and amplitude information, and the method further includes: Multiple reference probe field measurements were obtained to obtain the wireless signal generated by the DUT; The phase information from the field measurements of the multiple reference probes is used to obtain a reference phase for the phase information of the multiple probe-based field measurements.

15. The method according to claim 1, The plurality of probe-based field measurements include phase and amplitude information, and the method further includes: Phase information is extracted from the input signal that drives the wireless signal generated by the DUT; The phase information of the input signal is used to obtain a reference phase for the phase information of the multiple probe-based field measurements.

16. A non-transitory computer-readable storage medium comprising program instructions for determining a far-field (FF) pattern of a wireless signal generated by a device under test (DUT), wherein the DUT includes an antenna array comprising a plurality of DUT antenna elements, wherein the program instructions are executable by a processor to: Multiple probe-based near-field measurements are obtained of the wireless signal generated by the DUT, wherein the wireless signal generated by the DUT is generated according to a multiple beamformer setup set of the multiple DUT antenna elements, and wherein the multiple beamformer setup set spans the vector space of the beamformer setup set, wherein the acquisition is performed by a probe antenna system (PAS) having multiple PAS antenna elements, wherein the multiple PAS elements are equal to or greater than the multiple DUT antenna elements; The set of DUT FF scaling factors is calculated using the plurality of probe-based near-field measurement and calibration coefficient sets, the amount of which is equal to the amount of the reference DUT FF basic function set; The FF pattern of the wireless signal is determined based on the DUT FF scaling factor and the reference DUT FF basic function set; The FF pattern of the wireless signal generated by the DUT can be used to evaluate the operation of the DUT in the FF.

17. The non-transitory computer-readable storage medium according to claim 16, During the acquisition of the plurality of probe-based near-field measurements of the wireless signal generated by the DUT, the program instructions can be executed to: While driving the beamformer with a signal, some beamformer settings are configured for the antenna elements of the DUT; and The amplitude and phase of the electromagnetic field generated by multiple antenna elements of the DUT are measured at at least one frequency using the PAS.

18. The non-transitory computer-readable storage medium of claim 16, wherein the set of calibration coefficients is in the form of a reconstruction matrix; The program instructions described therein are executable to calculate the DUT FF scaling factor set using the plurality of probe-based field measurements and the reconstruction matrix.

19. The non-transitory computer-readable storage medium of claim 16, wherein the program instructions are executable to: The following steps are used to obtain the reference DUT FF basic function set: Obtain a set of reference DUT FF patterns generated by multiple antenna elements of the reference DUT under different beamforming settings, such that the set of reference DUT FF patterns can be used to enable the calculation of FF patterns specific to beamforming settings as linear combinations of the set of reference DUT FF patterns. The reference DUT FF pattern set is the reference DUT FF basic function set; and The calibration coefficients are generated through the following steps: A series of near-field measurements based on the reference DUT probes were obtained to obtain the wireless signals generated by the reference DUT under a set of different beamformer settings; and The near-field measurements of the series of multiple reference DUT probes are processed.

20. A system for determining a far-field (FF) pattern of a wireless signal generated by a device under test (DUT), wherein the DUT includes an antenna array comprising a plurality of DUT antenna elements, wherein the system includes: The test equipment supports the DUT, and the probe antenna system is used to measure the electromagnetic signals generated by the DUT. as well as A computer system, comprising a processor and a memory, wherein the memory stores program instructions that the processor can execute to perform the following steps: Multiple probe-based near-field measurements are obtained of the wireless signal generated by the DUT, wherein the wireless signal generated by the DUT is generated according to a multiple beamformer setup set of the multiple DUT antenna elements, and wherein the multiple beamformer setup set spans the vector space of the beamformer setup set, wherein the acquisition is performed by a probe antenna system (PAS) having multiple PAS antenna elements, wherein the multiple PAS elements are equal to or greater than the multiple DUT antenna elements; The set of DUT FF scaling factors is calculated using the plurality of probe-based near-field measurement and calibration coefficient sets, the amount of which is equal to the amount of the reference DUT FF basic function set; The FF pattern of the wireless signal is determined based on the DUT FF scaling factor and the reference DUT FF basic function set; The FF pattern of the wireless signal generated by the DUT can be used to evaluate the operation of the DUT in the FF.

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