Method for evaluating electromagnetic field

Abstract

The invention discloses a method for evaluating an electromagnetic field. The invention relates to a method for evaluating an electromagnetic field of a device under test. The method comprises the steps of providing a device under test radiating an electromagnetic field, performing a measurement of the device under test in order to obtain measurement data, determining an equivalent source of the device under test based on the measurement data, the equivalent source having a source surface, providing a model comprising the determined equivalent source and at least one modeled scatterer, creating a monitoring surface surrounding the equivalent source but not surrounding the at least one modeled scatterer, calculating an electromagnetic field of the equivalent source on the monitoring surface, while evaluating a total radiation power based on the electromagnetic field in the presence of the at least one modeled scatterer, and determining at least one normalization factor based on the determined total radiation power and the measurement data.

Description

Technical Field

[0001] The present invention relates to a method for evaluating the electromagnetic field of a device under test. Background Art

[0002] In the state of the art, it is known to evaluate the electromagnetic fields of a device under test, such as the electromagnetic fields radiated by the device under test which may have an antenna. However, in cases where there are nearby scatterers or the evaluation should be performed inside a scattering object, the evaluation can become complicated and time consuming.

[0003] Today, antennas to be tested are used in a variety of applications. Antennas can be integrated in complex structures, such as in the bumper of a vehicle. In addition, complex scenarios can be tested depending on the antenna radiating near a person's body or head, such as in the case of antennas for mobile devices. Therefore, the electromagnetic fields must be characterized under complex conditions, resulting in complex test scenarios.

[0004] It turns out that large calculation errors occur when scatterers are in close proximity to the DUT. This can happen when the DUT is integrated into a complex structure, such as a vehicle’s bumper, or is used in difficult conditions, such as close to the body or head.

[0005] In the state-of-the-art, these scenarios have to be handled by using detailed numerical models of the radiation sources, but this requires in-depth knowledge of the device under test. Obviously, such a priori knowledge of the device under test is not always available. Summary of the invention

[0006] Therefore, a different approach is used, according to which the electromagnetic fields are evaluated based on equivalent sources that are used for modeling. The corresponding modeling allows to take into account the interaction between the device under test (especially its antenna) and the environment. The calculations made usually include the normalization of the power of the source radiating the electromagnetic fields (i.e. the device under test). This is crucial, because an incorrect normalization affects all modeled power transfers in the computational domain with the same error.

[0007] In an ideal scenario, an equivalent source is identified that has similar characteristics (e.g. radiates similar power) as the real source (with respect to a priori power normalization). This is a reasonable approach and works well when all scatterers are far enough away from the radiation source (i.e., the device under test). However, it turns out that this approach is not feasible in cases where scatterers are located close to the excitation source.

[0008] Therefore, an efficient solution is needed to evaluate the electromagnetic field of the device under test, especially when there is no prior knowledge of the device under test.

[0009] An embodiment of the present invention provides a method for evaluating the electromagnetic field of a device under test. The method comprises the following steps:

[0010] - The device under test that provides the radiated electromagnetic field,

[0011] - performing measurements on the device under test in order to obtain measurement data, wherein at least two components of the electromagnetic field of the device under test are measured on a measurement surface with respect to their amplitude and phase,

[0012] - determining an equivalent source of the device under test based on the measurement data, wherein the equivalent source has a source surface different from the measurement surface,

[0013] - providing a model comprising the determined equivalent source and at least one modeled scatterer, wherein the determined equivalent source is used as an excitation source,

[0014] - creating a monitoring surface that surrounds the equivalent source but does not surround or pass through at least one modeled scatterer,

[0015] - Calculate the electromagnetic field of the equivalent source on the monitoring surface,

[0016] - evaluating a total radiated power based on the calculated electromagnetic field and the presence of at least one modeled scatterer, and - determining at least one normalization factor based on the determined total radiated power and the measurement data.

[0017] The main idea is to use in-situ normalization instead of a priori normalization. The in-situ normalization is based on the total radiated power determined on the monitoring surface for equivalent sources and simulated scatterers, i.e. the individual electromagnetic waves passing through the monitoring surface, and the measurement data obtained when performing measurements on the device under test, in particular measuring at least two components of the electromagnetic field on the measurement surface with respect to their amplitude and phase. For example, the at least two components of the electromagnetic field may be related to the electric field component with respect to spherical coordinates, i.e. E θ (E_theta) and Alternatively, the corresponding magnetic components, such as H θ (H_theta) and

[0018] In other words, the total radiated power takes into account the field originating from the excitation source (ie, the equivalent source) and the scattered field originating from the simulated scatterers.

[0019] In general, the accuracy of the normalization is improved compared to the solutions known from the state-of-the-art techniques.

[0020] The corresponding numerical electromagnetic simulation for calculating the equivalent sources and electromagnetic fields may be based on the finite difference time domain (FDTD) technique.

[0021] The model can be provided by a full-wave simulation, which can implement FDTD (finite difference time domain) technology, FEM (finite element method) technology and / or MOM (method of moments) technology. In other words, a model is established in the simulation, wherein the model includes a determined equivalent source and at least one modeled scatterer.

[0022] In particular, an evaluation of the total radiated power is performed on the monitoring surface.

[0023] One aspect provides that when performing a measurement of a device under test on a measurement surface, an initial total radiated power (TRP) is measured, wherein at least one normalization factor is determined based on the initial total radiated power and the total radiated power determined on the monitoring surface. The measurement data comprises, among other things, the initial total radiated power, based on which at least one normalization factor is determined. In particular, the at least one normalization factor can be based on a quotient of a total radiated power determined on the monitoring surface for an electromagnetic field of an equivalent source and the initial total radiated power measured during the measurement.

[0024] Another aspect provides that a normalization factor for the power, a normalization factor for the electric field and / or a normalization factor for the magnetic field is calculated. Thus, different normalization factors can be determined based on the steps performed in order to improve the accuracy of the normalization.

[0025] A further aspect provides that when performing a measurement of the device under test on the measuring surface, an initial total radiated power is measured, wherein at least one normalization factor is determined based on the initial total radiated power and the total radiated power determined on the monitoring surface. The normalization factor of the power is the quotient of the initial total radiated power and the total radiated power determined on the monitoring surface. Thus, the normalization factor of the power can be obtained in a simple and efficient manner.

[0026] Furthermore, when performing measurements of the device under test on the measuring surface, an initial radiated power can be measured, wherein at least one normalization factor is determined based on the initial total radiated power and the total radiated power determined on the monitoring surface. The normalization factor for the electric field and / or the normalization factor for the magnetic field is the square root of the quotient of the initial total radiated power and the total radiated power determined on the monitoring surface. Likewise, the corresponding normalization factor for the electric field and / or the magnetic field can be determined in an efficient manner based on the initial total radiated power obtained during the measurement of the device under test and the total radiated power determined when calculating the (simulated) electromagnetic field of an equivalent source on the monitoring surface.

[0027] Generally, the total radiation power determined on a respective surface (eg a monitoring surface) means that the total radiation power passing through the respective surface is determined, eg the influence of the excitation source (equivalent source) and scatterers.

[0028] Another aspect provides that the equivalent source is determined such that the simulated electromagnetic field of the equivalent source on the measurement surface is similar to the electromagnetic field of the device under test measured on the measurement surface. Thus, the equivalent source is created such that it radiates on the measurement surface a similar electric field and a similar magnetic field as seen from the measurement surface when performing measurements on the device under test.

[0029] When calculating the electromagnetic field of the equivalent source on the monitoring surface, the scattered electromagnetic field of at least one modeled scatterer can be taken into account. Therefore, the influence of at least one modeled scatterer is taken into account in order to determine its influence. In fact, the scattered field interacts with the electromagnetic field originating from the equivalent source, so the scattered field is taken into account. In other words, the output power of the equivalent source is affected by the scattered field of at least one modeled scatterer.

[0030] A further aspect provides that the device under test is completely surrounded by the source surface and / or the monitoring surface. The equivalent scatterer and its source surface are calculated so that the physical device under test is completely surrounded by the volume bounded by the source surface. The corresponding simulation ensures that all simulated exit powers are collected on the monitoring surface.

[0031] In other words, neither the source surface nor the monitoring surface can pass through the device under test. Therefore, no part of the device under test is located outside the volume defined by the corresponding surface (e.g., the source surface or more precisely the monitoring surface) because the volume defined by the device under test does not intersect the corresponding surface.

[0032] In general, the source surface and / or the monitoring surface may have any shape.

[0033] The source surface can be as small as possible while completely surrounding the device under test. The distance to the device under test can be several wavelengths, for example two wavelengths, or even only one wavelength. Thus, the source surface is arranged as close as possible relative to the device under test.

[0034] The equivalent source can be determined based on the applied algorithm. As discussed above, the equivalent source can be obtained during simulation (calculation). For example, the equivalent source is a Huygens source, and the source surface is a Huygens surface. The equivalent source, in particular the Huygens source, can be determined for the device under test by means of an over-the-air test (OTA) test system as follows.

[0035] The OTA test system comprises an analysis circuit and at least one measuring antenna. The determination comprises the following steps: - performing at least two sets of measurements of electromagnetic waves emitted by the device under test by means of at least one measuring antenna, thereby generating a measurement signal associated with the electromagnetic waves, i.e., measurement data;

[0036] - determining at least one radiation parameter of the device under test based on the measurement signal, ie the measurement data, by means of the analysis circuit, wherein the at least one radiation parameter is associated with electromagnetic waves emitted by the device under test; and

[0037] - determining an equivalent source on the Huygens surface by means of the analysis circuit based on at least one determined radiation parameter, wherein the equivalent source is associated with the device under test.

[0038] A Huygens surface can have any defined surface geometry. In particular, a Huygens surface can be a surface that closely surrounds the device under test.

[0039] For example, the Huygens surface may have a shape similar to or the same shape as the outer surface of the device under test. Thus, the equivalent source is very similar to the device under test, so that a realistic simulation of the device under test is provided by means of the equivalent source.

[0040] For example, a Huygens surface may be cubic, cuboid, columnar, cylindrical or spherical. However, a Huygens surface may have any other surface geometry, i.e. the surface geometry may be arbitrarily complex.

[0041] In fact, the equivalent source includes at least one equivalent current and / or at least one equivalent magnetic current. In general, at least one equivalent current and at least one equivalent magnetic current are determined so that when observed from the measurement surface, the electromagnetic waves emitted by these currents are similar to the electromagnetic waves emitted by the device under test. In other words, for example, when modeling the equivalent source, at least one equivalent current and at least one equivalent magnetic current are used as model parameters for the simulation of the device under test.

[0042] The equivalent source may be determined by solving a corresponding inverse mathematical equation based on at least one determined radiation parameter. In general, the inverse mathematical equation may be related to the electromagnetic radiation sources included in the equivalent source and the electromagnetic fields generated by these sources. Therefore, by solving the inverse mathematical equation, or more precisely, by fitting the parameters of the inverse mathematical equation to at least one determined radiation parameter, the equivalent source may be determined.

[0043] The source surface may be a numerical field surface. Since the source surface is determined based on an applied algorithm (ie numerical electromagnetic simulation), for example based on finite difference time domain—FDTD, the source surface is determined numerically.

[0044] At least one modeled scatterer may provide a scattering environment. The scattering environment may include more than one modeled scatterer. Thus, the accuracy provided by the normalization may be further improved.

[0045] The (physical) device under test may be surrounded by the measurement surface. Therefore, it is ensured that when all exiting powers are measured, the total radiated power can be determined with high accuracy.

[0046] For example, the measurement surface is a spherical surface. The measurement antenna can be driven along the spherical measurement surface in order to collect measurement data.

[0047] The measurement can be a free space measurement. Alternatively or additionally, the measurement is performed in an anechoic chamber. Thus, no interference from further radiation sources may have an influence on the obtained measurement data.

[0048] The device under test may include an antenna under test. For example, the antenna may be integrated into a complex structure, such as behind a vehicle bumper.

[0049] Typically, an enhanced antenna measurement can be performed where

[0050] - Amplitude and phase measurements of at least two electromagnetic field components radiated by the antenna under test (AUT) are performed under "free space" conditions, typically in an anechoic chamber;

[0051] - Create an equivalent source with a source surface containing the AUT from the measurement data using an appropriate algorithm (e.g. TUM FIAFTA);

[0052] - This equivalent source is then imported into a numerical modelling (e.g. FDTD code) where the nearby scatterer(s) are simulated;

[0053] - Numerical modeling allows to consider the interaction between the AUT and the environment provided by the scatterer(s), and thereby calculate the radiated field in complex scenarios.

[0054] The subject matter of the present invention generally allows to improve the accuracy of power normalization in numerical electromagnetic simulations when an equivalent source (e.g. a Huygens source) is used as excitation and is placed near at least one scattering object ("modeled scatterer"), or vice versa. This improvement is achieved by placing the source surface (i.e. the numerical field surface) around the device under test. The equivalent source is placed in the presence of a scattering environment (i.e. at least one modeled scatterer). Then, an "in situ" normalization of the power is performed based on the total radiated power (TRP) through the monitoring surface. Based on this and the measurement data obtained during the initial measurement of the device under test, at least one normalization factor is calculated. At least one normalization factor can be used to normalize the magnetic field and / or electric field within the simulation domain.

[0055] Since an equivalent source is created so that it radiates on the measurement surface similar electric fields and similar magnetic fields as seen from the measurement surface when performing measurements on the device under test, the relationship between the physical device under test and the equivalent source is obtained. In other words, the equivalent source is a simulated object that has similar characteristics as the physical device under test as seen from the measurement surface. Since the equivalent source is a simulated object, its radiation characteristics can be simulated for other surfaces (such as monitoring surfaces), while also taking into account the influence of nearby scatterers. Therefore, corresponding normalization can be performed, especially in-situ normalization. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily understood as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings.

[0057] - Figure 1 schematically shows an overview of a method for evaluating an electromagnetic field of a device under test according to an embodiment of the present invention, and

[0058] - Figure 2 The temporal behavior of a wave packet excited by a field source in two different scenarios, namely a distant scatterer and a nearby scatterer, is schematically illustrated. DETAILED DESCRIPTION

[0059] The detailed description set forth below in conjunction with the accompanying drawings, in which like reference numerals refer to like elements, is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiment. Each embodiment described in this disclosure is provided only as an example or illustration and should not be construed as being preferred or superior to other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise form disclosed.

[0060] For purposes of this disclosure, the phrase "at least one of A, B, and C" means, for example, (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when more than three elements are listed. In other words, the term "at least one of A and B" generally means "A and / or B", i.e., "A" alone, "B" alone, or "A and B".

[0061] exist Figure 1 In FIG. 1 , an overview of a method of evaluating the electromagnetic field of a device under test 10 is shown.

[0062] In a first step 1), a free-space measurement of the device under test 10 may be performed by means of a measuring antenna 12 which performs measurements on a measuring surface 14 in order to obtain measurement data.

[0063] The obtained measurement data are associated with at least two components of the electromagnetic field of the device under test 10 with respect to their amplitude and phase on the measurement surface 14. In the illustrated embodiment, the electric field E and the magnetic field H are schematically shown respectively.

[0064] Furthermore, the measurement data may include an initial total radiation power P0 which is also measured during the measurement.

[0065] The measuring antenna 12 may be movably positioned such that it can be moved around the device under test 10 during measurement in order to measure the initial total radiated power (TRP) accordingly.

[0066] like Figure 1 As shown, the measurement surface 14 may involve a spherical surface that completely surrounds the device under test 10. However, measurement surfaces 14 of different shapes may also be used, if appropriate.

[0067] The corresponding measurements can be carried out in an anechoic chamber 15 (e.g. Figure 1 Thus, interfering signals, which may damage the measurement of the device under test 10, can be avoided.

[0068] In a second step 2), an equivalent source 16 of the device under test 10 is determined based on the measurement data obtained during the measurement along the measurement surface 14. The equivalent source 16 has a source surface 18.

[0069] As in Figure 1 As can be seen in FIG. 1 , source surface 18 is different from measurement surface 14 because it is closer to device under test 10. In fact, source surface 18 completely surrounds device under test 10. Therefore, source surface 18 of equivalent source 16 does not pass through physical device under test 10.

[0070] Since the second step is performed by a computing program, the physical device under test 10 is shown in a shaded manner in step 2) for illustration purposes only, ie, to show that the physical device under test 10 is completely surrounded by the source surface 18 .

[0071] In fact, the equivalent source 16 refers to an object with defined characteristics based on the obtained measurement data. Therefore, the equivalent source 16 is a simulated object having similar characteristics to the physical device under test 10 as seen from the measurement surface 14 shown in dashed lines in step 2).

[0072] The source surface 18 may have a distance d of several wavelengths, in particular one wavelength, from the physical DUT 10. The size or volume enclosed by the source surface 18 may be chosen as desired, as long as the physical DUT 10 is confined by the source surface 18 of the equivalent source 16, as shown.

[0073] The equivalent source 16 may be a Huygens source having a source surface 18 , which may in turn be a Huygens surface.

[0074] Typically, the equivalent source 16 is calculated so as to have a simulated electromagnetic field on the measurement surface 14 that is similar to the electromagnetic field measured on the measurement surface 4, such as the electric and magnetic fields of the physical device under test 10. In other words, the equivalent source 16 with its source surface 18 is calculated so that its simulated electromagnetic field has (substantially) the same characteristics as the physical device under test 10 has on the measurement surface 14, such as the electromagnetic field radiated by the physical device under test 10.

[0075] Therefore, the equivalent source 16 corresponds to a simulated object having the same characteristics as the real device under test 12 on the measurement surface 14 (ie, in the real world). On the measurement surface 14, the measured electromagnetic field (eg, measurement data) corresponds to the simulated electromagnetic field of the equivalent source 16.

[0076] Therefore, the equivalent source 16 is calculated by means of the applied algorithm in order to ensure that the simulated electromagnetic field for the equivalent source 16 obtains corresponding features on the measurement surface 14. Thus, the source surface 18 can be related to the numerical field surface obtained by the applied algorithm.

[0077] In a third step 3), a model is provided which comprises the determined equivalent source 16 and at least one modeled scatterer 20. In fact, the equivalent source 16 is introduced into the simulation model with the additional scatterer 20 in the vicinity.

[0078] The determined equivalent source 16 is used as an excitation source, wherein a monitoring surface 22 is created which surrounds the equivalent source 16 with its source surface 18. Figure 1 In step 3), the monitoring surface 22 is shown by a dotted line. In fact, the monitoring surface 22 is larger than the source surface 18 or similar to the source surface 18, thereby ensuring that the equivalent source 16 is surrounded by the monitoring surface 22.

[0079] However, if Figure 1 As shown in step 3), the monitoring surface 22 does not surround at least one modeled scatterer 20 or pass through at least one modeled scatterer 20.

[0080] The physical device under test 10 is again shown in a shaded manner, since it no longer exists, as step 3) is also performed by a computing program executed on the processing circuit.

[0081] In other words, the determined equivalent source 16 is introduced into a simulation module (i.e. a processing circuit that performs the simulation (model)), which simulates, among other things, at least one modeled scatterer 20 in the vicinity of the equivalent source 16. The simulation module, in particular the executed simulation model, further calculates a monitoring surface 22 close to the source surface 18, such as Figure 1 shown.

[0082] Thereafter, the electromagnetic field of the equivalent source 16 is calculated on the monitoring surface 22 .

[0083] Based on the calculated electromagnetic fields and in the presence of at least one modeled scatterer 20 , a total radiated power (TRP) is evaluated, for example, on the monitoring surface 22 .

[0084] In fact, the scattered field (E S , H S ) interacts with the simulated electromagnetic fields E, H of the equivalent source 16, so that the output power of the equivalent source 16 is affected by the scattered field.

[0085] In the absence of at least one modeled scatterer 20 , the total radiation power through the monitoring surface 22 may be set to an initial total radiation power P0 measured during the measurement along the measurement surface 14 .

[0086] However, when there is at least one modeled scatterer 20, especially close to the equivalent source 16, or more precisely, a monitoring surface 22 that closely surrounds the equivalent source 16, the scattered field E S , H S It has an impact on the total radiated power.

[0087] When reference Figure 2 This becomes clear when two different scenarios are shown, where the difference between a scatterer far away from the equivalent source 16 or more precisely the device under test 10 (marked as scenario a) and a scatterer 20 close to the equivalent source 16 or more precisely the device under test 10 (marked as scenario b) is shown in more detail, in particular the temporal characteristics of the two pulses generated by the field source.

[0088] The field source, also called the excitation source, is an excitation pulse or more precisely a wave, such as a TEM wave, which travels to opposite directions, such as the left and the right. In other words, the corresponding pulse induces a wave. The corresponding scatterer, i.e. a perfect electrical conducting (PEC) wall, is located to the left of the field source, i.e. far away according to scenario a) or more precisely close according to scenario b).

[0089] In the graph, the positions of the scatterers and the field sources are shown by the vertical dashed lines. In addition, the temporal characteristics of the pulse (i.e., the induced wave) are shown by the corresponding z-component of the E field (Ex=Ey=0), the corresponding z-component of the H field multiplied by the free space impedance Z0 (Hx=Hy=0), the corresponding z-component of the Poynting vector (Sy=Sz=0), and the sum Sx normalized to the total energy of the pulse (i.e., ∑Sx / SxWgt).

[0090] Since the steps are shown in columns, where four columns are shown, the time behavior is shown.

[0091] The leftmost column and the middle right column belong together and show the time behavior of a scatterer far away from the equivalent source 16 or more precisely the device under test 10, which corresponds to the expected behavior. They are also marked by a).

[0092] The middle left column and the rightmost column belong together and show the time characteristics of a scatterer close to the equivalent source 16 or more precisely the device under test 10. They are also marked by b).

[0093] Therefore, the graphs in the leftmost column and the left-center column relate to the same time step. The same applies to the graphs in the right-center column and the rightmost column.

[0094] according to Figure 2 , it becomes apparent that there are distinctions between different locations of scatterers (in particular reflected pulses / waves).

[0095] Starting from step size 0, the field source radiates pulses / waves in the left and right directions, which becomes obvious when comparing the curve graphs of step size 50 and step size 0.

[0096] In addition, the graph for step size 80 shows that the pulse / wave that was originally traveling to the left has been reflected at a scatterer (“PEC”) located close to the source of the field, thereby changing the shape of the pulse / wave on the left ( Figure 2 100), while for the scatterer located far away, the pulse / wave that initially traveled to the left continues to travel in an undisturbed manner.

[0097] In step 100, the reflected pulse / wave hits both sides of the field source, while the field source (excitation source) is still exciting because the excitation pulse has not decayed, as shown in b), especially Figure 2 The center left column.

[0098] In step 120, the pulse / wave in the first scenario (distant scatterer) is now reflected by the scatterer, as shown in a), i.e. Figure 2 The leftmost column.

[0099] In step 150, the reflected pulse / wave interferes with the original pulse / wave travelling to the right, thereby providing a combined wave packet travelling to the right, as shown in b), i.e. Figure 2 The upper graph in the rightmost column. At this point, it also becomes apparent that at the source of a closely located scatterer, the sum Sx normalized to the total energy of the pulse, ∑Sx / SxWgt, is above 1. In contrast, at the source of a distant scatterer, the sum Sx normalized to the total energy of the pulse, ∑Sx / SxWgt, is 0.5.

[0100] In step size 160, Figure 2 The middle right column of (i.e. the scenario where the scatterer is far away) shows that the Ez component of the left pulse / wave flips from negative to positive due to the scatterer.

[0101] In step 190, the reflected pulse / wave for the scenario in which the scatterer is located far away also starts to travel to the right due to reflection at the scatterer located far away.

[0102] In the other scenario shown in b), ie the rightmost column, the combined wave packets travel further to the right, while the sum Sx normalized to the total energy of the pulse / wave, ie ΣSx / SxWgt, is above 1 at further locations.

[0103] In step 230, the reflected pulse / wave for the scenario where the scatterer is far away now passes through the field source. In this scenario, the excitation pulse has been attenuated, resulting in different characteristics compared to step 100 for the scenario where the scatterer is close. In fact, the reflected pulse / wave for the scenario where the scatterer is far away does not interact with the pulse / wave that originally traveled to the right. As shown, two separate pulses / waves travel to the right in separate ways.

[0104] In step 300, the pulses / waves for the scenario where the scatterer is far away are still separated, but travel further to the right. For the scenario where the scatterer is close, the combined wave packet also travels further to the right.

[0105] As shown in steps 300 and 350, for the scenario where the scatterer is located nearby, the sum Sx normalized to the total energy of the pulse / wave, i.e., ∑Sx / SxWgt, becomes higher than 1, while for the scenario where the scatterer is located farther away, the sum Sx normalized to the total energy of the pulse / wave, i.e., ∑Sx / SxWgt, is equal to 1 as expected.

[0106] From the temporal characteristics obtained for different scenarios, it becomes clear that in the scenario where the scatterer is located nearby, the reflected waves hit the field source while it is still excited, affecting the total radiated energy of the field source.

[0107] This difference clearly illustrates why the normalization factor must be determined for scenarios where the scatterers are located nearby, especially in situ rather than a priori.

[0108] Therefore, due to the additional modeled scatterer 20, for example, the influence thereof, the total radiated power P1 may differ from the initial total radiated power P0.

[0109] However, at least one normalization factor may be determined based on the total radiated power P1 determined on the monitoring surface 22 using at least one modeled scatterer 20 and the measurement data, ie the measured initial total radiated power P0 .

[0110] For example, normalization factors for power, electric field and magnetic field can be calculated, which can be used to improve the efficiency and accuracy of normalization, so that improved simulation results are obtained, in particular taking into account the effects, which in Figure 2 is shown in .

[0111] The normalization factor of the power may be related to the quotient of the initial total radiated power and the determined total radiated power (ie P0 / P1).

[0112] The normalization factor for the electric field or, more precisely, the magnetic field can be related to the square root of the quotient of the initial total radiated power and the determined total radiated power.

[0113] Certain embodiments disclosed herein, in particular (one or more) corresponding modules and / or (one or more) units, utilize circuit systems (e.g., one or more circuits) to implement the standards, protocols, methods or technologies disclosed herein, operably couple two or more components, generate information, process information, analyze information, generate signals, encode / decode signals, convert signals, send and / or receive signals, control other devices, etc. Any type of circuit system may be used.

[0114] In an embodiment, the circuit system includes, among other things, one or more computing devices, such as a processor (e.g., a microprocessor), a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system on a chip (SoC), or the like, or any combination thereof, and may include discrete digital or analog circuit elements or electronic devices, or a combination thereof. In an embodiment, the circuit system includes a hardware circuit implementation (e.g., an implementation in an analog circuit system, an implementation in a digital circuit system, and the like, and a combination thereof).

[0115] In an embodiment, the circuit system includes a combination of circuits and a computer program product having software or firmware instructions stored on one or more computer-readable memories that work together to cause the device to perform one or more protocols, methods, or techniques described herein. In an embodiment, the circuit system includes circuits that require software, firmware, and the like to operate, such as, for example, a microprocessor or a portion of a microprocessor. In an embodiment, the circuit system includes one or more processors or portions thereof and accompanying software, firmware, hardware, and the like.

[0116] The present application may quote quantities and numbers. Unless specifically stated, such quantities and numbers should not be considered restrictive, but exemplary of possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term "plurality" to quote quantities or numbers. In this regard, the term "plurality" means any number more than one, such as two, three, four, five, etc. The terms "approximately", "approximately", "close to", etc. mean plus or minus 5% of the value.

Claims

1. A method for evaluating the electromagnetic field of a device under test, wherein the method comprises the following steps: - The device under test that provides the radiated electromagnetic field, - performing measurements on the device under test in order to obtain measurement data, wherein at least two components of the electromagnetic field of the device under test are measured on a measurement surface with respect to their amplitude and phase, - determining an equivalent source of the device under test based on the measurement data, wherein the equivalent source has a source surface different from the measurement surface, - providing a model comprising the determined equivalent source and at least one modeled scatterer, wherein the determined equivalent source is used as an excitation source, - creating a monitoring surface surrounding the equivalent source but not surrounding or passing through the at least one modeled scatterer, - calculating the electromagnetic field of said equivalent source on said monitoring surface, - evaluating the total radiated power based on the calculated electromagnetic field in the presence of the at least one modeled scatterer, and - determining at least one normalization factor based on the determined total radiated power and the measurement data.

2. The method according to claim 1, wherein: When performing a measurement of the device under test on the measurement surface, an initial total radiated power is measured, and wherein the at least one normalization factor is determined based on the initial total radiated power and a total radiated power determined on the monitoring surface.

3. The method according to claim 1 or 2, wherein: A normalization factor of the power, a normalization factor of the electric field and / or a normalization factor of the magnetic field is calculated.

4. A method according to any one of the preceding claims, wherein: When performing measurements of the device under test on the measuring surface, an initial total radiated power is measured, wherein the at least one normalization factor is determined based on the initial total radiated power and the total radiated power determined on the monitoring surface, and wherein the normalization factor of the power is the quotient of the initial total radiated power and the total radiated power determined on the monitoring surface.

5. A method according to any one of the preceding claims, wherein: When performing measurements of the device under test on the measuring surface, an initial total radiated power is measured, wherein the at least one normalization factor is determined based on the initial total radiated power and the total radiated power determined on the monitoring surface, and wherein the normalization factor of the electric field and / or the normalization factor of the magnetic field is the square root of the quotient of the initial total radiated power and the total radiated power determined on the monitoring surface.

6. A method according to any one of the preceding claims, wherein: The equivalent source is determined such that a simulated electromagnetic field of the equivalent source on the measurement surface is similar to an electromagnetic field of the device under test measured on the measurement surface.

7. A method according to any one of the preceding claims, wherein: When determining the at least one normalization factor, the scattered electromagnetic field of the at least one modeled scatterer is taken into account.

8. A method according to any one of the preceding claims, wherein: The device under test is completely surrounded by at least one of the source surface and the monitoring surface.

9. A method according to any one of the preceding claims, wherein: At least one of the source surface and the monitoring surface does not pass through the device under test.

10. A method according to any one of the preceding claims, wherein: The equivalent sources are determined based on the applied algorithm.

11. A method according to any one of the preceding claims, wherein: The equivalent source is a Huygens source, and the source surface is a Huygens surface.

12. A method according to any one of the preceding claims, wherein: The source surface is a numerical field surface.

13. A method according to any one of the preceding claims, wherein: The at least one modeled scatterer provides a scattering environment.

14. A method according to any one of the preceding claims, wherein: The device under test is surrounded by the measurement surface.

15. A method according to any one of the preceding claims, wherein: The measuring surface is a spherical surface.

16. A method according to any one of the preceding claims, wherein: The measurements are free space measurements and / or wherein the measurements are performed in an anechoic chamber.

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