Measuring instrument

Abstract

A measuring instrument is described. The measuring instrument comprises at least one input port and a measuring module. The input port is configured to receive a radio frequency (RF) signal from a device under test, where the RF signal includes a sequence of symbols. The measurement module is configured to receive an RF signal from the input port. The measurement module includes a reference signal module, where the reference signal module is configured to generate a reference signal based on the received RF signal, where the reference signal includes an extracted symbol sequence corresponding to a symbol sequence of the RF signal. The measurement module also includes an error module, wherein the error module is configured to determine an error vector based on the RF signal and based on the reference signal. The measurement module further comprises an analysis module, wherein the analysis module is configured to determine whether the reference signal is correct based on the determined error vector.

Description

Technical Field

[0001] The present invention generally relates to a measuring instrument. Background Art

[0002] For different types of measurement applications, a reference signal corresponding to an ideal version of a received RF signal is extracted from the RF signal.

[0003] For these measurements to be correct, it is required that the extracted reference signal includes the same symbol sequence as the RF signal.

[0004] In some cases, e.g., if the RF signal has a low signal-to-noise ratio, detection errors may occur, i.e., the individual symbols of the symbol sequence in the extracted reference signal may be incorrect.

[0005] In the prior art, the actual symbol sequence included in the RF signal must be known in order to avoid or correct such detection errors.

[0006] However, there are cases where the actual symbol sequence is unknown. In these measurement scenarios, the above detection errors cannot be reliably corrected.

[0007] Therefore, an object of the present invention is to provide a measuring instrument capable of reliably detecting detection errors. Summary of the Invention

[0008] According to the present invention, the problem is solved by a measuring instrument. The measuring instrument includes at least one input port and a measurement module. The input port is configured to receive a radio frequency (RF) signal from a device under test, where the RF signal includes a symbol sequence. The measurement module is configured to receive the RF signal from the input port. The measurement module includes a reference signal module, where the reference signal module is configured to generate a reference signal based on the received RF signal, where the reference signal includes an extracted symbol sequence corresponding to the symbol sequence of the RF signal. The measurement module further includes an error module, where the error module is configured to determine an error vector based on the RF signal and based on the reference signal. The measurement module further includes an analysis module, where the analysis module is configured to determine whether the reference signal is correct based on the determined error vector.

[0009] Wherein and hereinafter, the term "module" is understood to describe suitable hardware, suitable software, or a combination of hardware and software configured to have a specific function.

[0010] The hardware may include, among other things, a CPU, a GPU, an FPGA, an ASIC, or other types of electronic circuitry.

[0011] Furthermore, the term "error vector" is understood to represent a vector equal to the difference between the RF signal and the reference signal at a certain point (i.e., at the symbol instance). More precisely, each error vector is equal to the difference between a sample of the RF signal and the corresponding sample of the reference signal.

[0012] For example, if the RF signal is an IQ modulated signal, each error vector is the difference between one of the samples of the RF signal and the corresponding constellation point.

[0013] The present invention is based on the discovery that the correctness of the reference signal can be evaluated based on the determined error vectors, as will be described in more detail below.

[0014] Among them, it is not necessary to know the actual symbol sequence included in the RF signal.

[0015] On the contrary, the correctness of the reference signal, and thus the correctness of the performed measurement, can be evaluated based only on the RF signal and the extracted reference signal.

[0016] Therefore, even if the details of the RF signal, especially the symbol sequence included in the RF signal, are unknown, the measuring instrument according to the present invention is capable of detecting errors in the extracted reference signal.

[0017] According to one aspect of the present invention, the analysis module is configured to determine an error distribution based on the error vectors, wherein the analysis module is configured to determine whether the reference signal is correct based on the determined error distribution. Generally speaking, the error distribution associated with a certain type of error in the RF signal has a certain expected shape. On the contrary, if the shape of the error distribution is significantly different from the expected shape, it can be concluded that additional errors have occurred, especially errors in the extracted reference signal.

[0018] For example, uncorrelated noise in the RF signal is expected to cause the error distribution to have the shape of a normal distribution, or more precisely, the shape of a multivariate normal distribution. If the error distribution is significantly different from the multivariate normal distribution, it can be concluded that a detection error has occurred, that is, at least one symbol of the extracted reference signal is incorrect.

[0019] In an embodiment of the present invention, the reference signal module is configured to demodulate the RF signal to obtain a demodulated RF signal, wherein the reference signal module is configured to generate a reference signal based on the demodulated RF signal. By demodulating the RF signal, the individual symbols included in the RF signal can be extracted. Then, a reference signal can be generated based on the extracted symbols, that is, as an ideal version of the RF signal including the extracted symbols.

[0020] Among them, the modulation scheme on which the RF signal is based may be known or unknown.

[0021] According to another aspect of the present invention, the analysis module is configured to determine at least one analysis parameter, wherein at least one analysis parameter is associated with an RF signal, and wherein the analysis module is configured to determine at least one statistical parameter associated with the at least one analysis parameter based on the determined error vector, wherein the at least one statistical parameter indicates the measurement uncertainty with respect to the at least one analysis parameter. In other words, the measuring instrument can be configured to evaluate the accuracy of the measurement made on the RF signal based on the determined error vector, wherein the at least one statistical parameter is the measurement accuracy, or rather a measure of the measurement uncertainty.

[0022] Generally, the at least one analysis parameter is a parameter indicating the signal quality of the RF signal and thus the performance of the device under test that generates the RF signal.

[0023] For example, the at least one analysis parameter can be or include an error vector magnitude (EVM).

[0024] The measuring instrument may further include a visualization module, wherein the visualization module is configured to generate joint visualization data of the at least one analysis parameter and the at least one statistical parameter. Thus, the information about the at least one analysis parameter and the information about the at least one statistical parameter can be visualized together, such that the information about the at least one analysis parameter and the information about the at least one statistical parameter are presented to the user of the measuring instrument in an illustrative manner.

[0025] The measuring instrument may include a display configured to display the joint visualization data.

[0026] Alternatively or additionally, the measuring instrument may be connectable to an external display configured to display the joint visualization data.

[0027] If the analysis module detects that the extracted reference signal is incorrect, the visualization data may further include a warning signal, such as a text message and / or a warning flag. Thus, the user is warned that the measurement performed may be incorrect or even invalid.

[0028] Another aspect of the present invention provides that the analysis module is configured to estimate the symbol error rate of the RF signal based on the determined error vector. In fact, the symbol error rate can be estimated based on the determined error vector without an actual symbol error occurring in the RF signal. In this way, the measurement time for determining the symbol error rate of the RF signal can be significantly reduced, because the analysis module does not have to wait for a statistically significant amount of errors to occur. This is particularly advantageous for RF signals with a low symbol error rate.

[0029] In one embodiment of the present invention, the analysis module is configured to determine an error distribution based on an error vector, wherein the analysis module is configured to estimate the symbol error rate of the RF signal based on the determined error distribution. In fact, the symbol error rate can be estimated based on the determined error distribution without an actual symbol error occurring in the RF signal. In this way, the measurement time for determining the symbol error rate of the RF signal can be significantly reduced because the analysis module does not have to wait for a statistically significant amount of errors to occur. This is particularly advantageous for RF signals with a low symbol error rate.

[0030] In another embodiment of the present invention, the analysis module is configured to estimate the symbol error rate based on the portion of the determined error distribution that is outside a decision boundary, particularly wherein the analysis module is configured to integrate over the portion of the determined error distribution that is outside the decision boundary in order to estimate the symbol error rate. The decision boundary represents a line in the IQ plane that separates the various possible symbol values. Thus, by evaluating the error distribution over the portions outside the respective decision boundaries, particularly by integrating the error distribution over the portions outside the respective decision boundaries, a measure of the probability that a constellation point lies outside the decision boundary is obtained, which measure corresponds to the probability of a symbol error.

[0031] The analysis module can be configured to determine whether a reference signal is correct based on additional system information. In this way, the accuracy of the detection of symbol errors in the extracted reference signal can be improved.

[0032] In particular, the additional system information may relate to the type of error expected in the RF signal. For example, the additional system information may include the type of noise expected, such as only uncorrelated noise. As another example, the additional system information may include information as to whether the non-linear behavior of the RF signal is expected.

[0033] In an embodiment of the present invention, the symbol sequence included in the RF signal is unknown to the measurement module. Thus, the measuring instrument is configured to detect errors in the extracted reference signal without prior knowledge of the symbol sequence included in the RF signal. Thus, measurements can be reliably performed even if the symbol sequence is unknown.

[0034] According to an aspect of the present invention, the modulation scheme of the RF signal is unknown to the measurement module. In fact, the measurement module can be configured to determine the modulation scheme of the RF signal based on the RF signal, particularly based on the constellation diagram of the RF signal. Thus, the measuring instrument is configured to detect errors in the extracted reference signal without prior knowledge of the modulation scheme of the RF signal.

[0035] In yet another embodiment of the present invention, the analysis module is configured to determine the error vector of an error, in particular the error component of the error vector of the error. In other words, the analysis module can be configured to identify the individual error vectors that are incorrect, i.e., the error vectors that refer to the symbol values extracted in error.

[0036] In particular, the analysis module is configured to correct the determined error vector of the error. In this way, the accuracy of the measurement performed on the RF signal can be improved because the error vector of the error can be corrected for the measurement.

[0037] For example, the accuracy of at least one of the above-mentioned analysis parameters can be improved because the error vector of the error can be corrected before determining at least one analysis parameter.

[0038] As another example, the symbol error rate can be estimated with improved accuracy because the error vector of the error can be corrected before determining the error distribution.

[0039] In another embodiment of the present invention, the analysis module is configured to discard the determined error vector of the error. In this way, the accuracy of the measurement performed on the RF signal can be improved because the error vector of the error can be discarded for the measurement.

[0040] For example, the accuracy of at least one of the above-mentioned analysis parameters can be improved because the error vector of the error can be discarded before determining at least one analysis parameter.

[0041] As another example, the symbol error rate can be estimated with improved accuracy because the error vector of the error can be discarded before determining the error distribution.

[0042] Yet another aspect of the present disclosure provides that the measuring instrument is a signal analyzer, a spectrum analyzer or an oscilloscope. However, it should be understood that the measuring instrument can be configured as any other suitable type of measuring instrument. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated, as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0044] - Figure 1 Schematically shows a measurement system having a measuring instrument according to the present invention;

[0045] - Figure 2 Schematically shows an exemplary constellation diagram of an RF signal;

[0046] - Figure 3 Shows in more detail a single constellation point of the constellation Figure 4 ;

[0047] -Figure 4 shows Figure 2 constellation points, where there is an additional error; and

[0048] - Figure 5 shows Figure 2 the constellation points in and the associated decision boundaries. DETAILED DESCRIPTION

[0049] The following detailed description presented in conjunction with the accompanying drawings, where 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 embodiments. Each embodiment described in this disclosure is provided by way of example or illustration only and should not be construed as 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 exact forms disclosed.

[0050] For the 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.

[0051] Figure 1 Schematically shows a measurement system 10 including a device under test (DUT) 12 and a measuring instrument 14.

[0052] Generally, the device under test 12 can be any type of electronic device configured to generate an RF signal or configured to process an input signal to obtain an RF signal, where the RF signal is an IQ modulated signal.

[0053] For example, the device under test 12 can be an amplifier, an attenuator, a filter, or a mixer.

[0054] As another example, the device under test 12 can be a signal generator, a mobile communication device, a network device, such as a router, etc.

[0055] However, it should be understood that the device under test 12 can be any other type of electronic device configured to generate and / or process an RF signal including a symbol sequence.

[0056] Generally, the measuring instrument 14 is configured to measure the device under test 12 in order to evaluate the performance of the device under test 12.

[0057] The measuring instrument 14 includes an input port 16 configured to receive the output signal of the device under test 12, i.e., the above-mentioned RF signal.

[0058] Note that the measuring instrument 14 may of course include further input ports.

[0059] In Figure 1 the exemplary embodiment shown, the output of the device under test 12 is connected to the input port 16 via a cable.

[0060] However, it should be understood that a wireless connection between the device under test 12 and the measuring instrument 14 is also possible. In this case, the input port 16 may include or be connected to an RF antenna configured to receive a wireless RF signal from the device under test 12.

[0061] The measuring instrument 14 further includes a measurement module 18 connected to the input port 16 to receive the RF signal.

[0062] Optionally, the measurement module 18 may include a mixer module 20 configured to down-convert the frequency of the RF signal by mixing the RF signal with a local oscillator (LO) signal.

[0063] Optionally, the measurement module 18 may further include a filter module 22 configured to filter the down-converted RF signal.

[0064] Hereinafter, the term "RF signal" is used to denote the RF signal received from the device under test 12 or the down-converted RF signal, depending on whether the mixer module 20 and the filter module 22 are provided.

[0065] The measurement module 18 further includes an analog-to-digital converter (ADC) 24 configured to digitize the RF signal to obtain a digitized RF signal.

[0066] Downstream of the ADC 24, a reference signal module 26 is provided.

[0067] Generally, the reference signal module 26 is configured to generate a reference signal based on the digitized RF signal, where the reference signal includes an extracted symbol sequence corresponding to the symbol sequence of the RF signal.

[0068] In fact, the reference signal module 26 may first demodulate the digitized RF signal to obtain a demodulated RF signal, and then may generate a reference signal based on the demodulated RF signal.

[0069] Wherein, the modulation scheme of the RF signal may be known, i.e., the reference signal module 26 may demodulate the RF signal based on a priori known modulation schemes.

[0070] If the modulation scheme of the RF signal is unknown, the reference signal module 26 can determine the modulation scheme based on the digitized RF signal, particularly based on the constellation diagram of the digitized RF signal.

[0071] As Figure 2 exemplarily shown in, the constellation diagram of the digitized RF signal typically includes samples of the digitized RF signal that are clustered around different possible constellation points 28 corresponding to different possible symbol values.

[0072] Conversely, the different possible constellation points 28, and thus the modulation scheme, can be derived from the constellation diagram, i.e., the sample distribution of the digitized RF signal in the IQ plane.

[0073] The reference signal module 26 extracts the symbols included in the demodulated RF signal and generates a corresponding ideal version of the RF signal including the same symbol sequence, i.e., the reference signal.

[0074] Wherein, prior knowledge of the symbol sequence included in the RF signal is not required.

[0075] As Figure 1 shown, the measurement module 18 further includes an error module 30 which is connected to the reference signal module 26 to receive the generated reference signal.

[0076] The error module 30 is also connected to the ADC 24 so as to receive the digitized RF signal.

[0077] Generally, the error module 30 is configured to determine an error vector based on the digitized RF signal and based on the generated reference signal.

[0078] Each error vector corresponds to the difference between the actual value of the sample of the digitized RF signal and the corresponding sample of the reference signal.

[0079] As for Figure 2 one sample exemplarily shown in, the error vector e corresponds to the vector from the ideal sample value (i.e., from the associated constellation point 28) to the actual sample value.

[0080] The determined error vector is forwarded to the analysis module 32 provided downstream of the error module 30.

[0081] The analysis module 32 can also be connected to the ADC 24 so as to receive the digitized RF signal.

[0082] In addition, the analysis module 32 can be connected to the reference signal module 26 so as to receive the reference signal.

[0083] Generally, the analysis module 32 is configured to determine whether the reference signal is correct based on the error vector determined by the error module 30.

[0084] More precisely, the analysis module 32 is configured to determine an error distribution based on an error vector, where the error distribution D(I,Q) describes the number or rather the density of error vectors as a function of I and Q (i.e., variables spanning the IQ plane).

[0085] Typically, the error distribution has the shape of a multivariate normal distribution around each constellation point 28.

[0086] More precisely, the error distribution typically has the shape of a bivariate normal distribution around each constellation point 28.

[0087] Thus, the error distribution across the entire IQ plane can be a superposition of bivariate normal distributions around each constellation point 28.

[0088] As Figure 3 shown, which shows a single constellation point 28 of the constellation diagram of Figure 2 and which corresponds to an approximately circular distribution of the respective sampling points around the constellation point 28.

[0089] If the determined error distribution matches the typical shape described above for all constellation points 28, it can be concluded that the extracted reference signal is correct.

[0090] However, if the determined error distribution is significantly different from the typical shape described above for at least one of the constellation points 28, it can be concluded that there are additional errors, in particular errors in the extracted reference signal.

[0091] In fact, the analysis module 32 can determine whether the extracted reference signal is correct based on the error distribution and based on additional system information.

[0092] In particular, the additional system information may be related to the type of error expected in the RF signal. For example, the additional system information can include the type of noise expected, such as only uncorrelated noise. As another example, the additional system information can include information on whether the non-linear behavior of the RF signal is expected.

[0093] Different types of errors are typically associated with different shapes of the resulting error distribution. Thus, if, taking into account the additional system information, the error distribution is different from the expected shape, it can be concluded that at least one symbol of the extracted reference signal is incorrect.

[0094] As Figure 4 exemplarily shown, the deviation of the error distribution from the bivariate normal distribution shape can also be visible in the constellation diagram.

[0095] In Figure 4In the specific example shown, the sample distribution around the constellation point 28 shown is different from a circular distribution and has an approximately rectangular shape.

[0096] The analysis module 32 may also be configured to estimate the symbol error rate of the RF signal based on the determined error vector, or rather, based on the determined error distribution.

[0097] As Figure 5 shown, there are decision boundaries 34 for each of the constellation points 28, which represent the lines in the IQ plane that separate the respective possible symbol values.

[0098] The symbol error rate (SER) can be estimated based on the portion of the determined error distribution D(I,Q) that is outside the decision boundary 34, that is, by evaluating the portion of the determined error distribution D(I,Q) that is outside the decision boundary 34.

[0099] In fact, the SER can be estimated by integrating the error distribution D(I,Q) over the portion of the error distribution that is outside the decision boundary 34. It holds

[0100]

[0101] where the region A1 is the region outside the decision boundary 34, and the integral in the denominator spans the entire portion of the IQ plane related to the error distribution, specifically the entire IQ plane.

[0102] Using this way of calculating the estimated symbol error rate, the symbol error rate can be estimated based on the determined error vector or rather based on the determined error distribution, without an actual symbol error occurring in the RF signal, because no actual symbol error is required to determine the error distribution.

[0103] The analysis module 32 may also be configured to determine at least one analysis parameter based on the determined error vector, based on a reference signal, and / or based on the digitized RF signal.

[0104] Generally, the at least one analysis parameter is a parameter indicating the performance of the device under test 12 or rather the signal quality of the RF signal.

[0105] For example, the at least one analysis parameter may be or include the error vector magnitude.

[0106] The analysis module 32 may also be configured to determine at least one statistical parameter associated with the at least one analysis parameter based on the determined error vector, where the at least one statistical parameter indicates the measurement uncertainty with respect to the at least one analysis parameter.

[0107] For example, at least one statistical parameter may be or include a standard deviation, a variance, and / or higher statistical moments.

[0108] To improve the accuracy of the above measurements, the analysis module 32 may be configured to determine an error error vector, in particular an error component of the error vector of the error.

[0109] Such an error error vector may occur if the symbol of the reference signal has been incorrectly determined such that the corresponding error vector points to an incorrect constellation point 28.

[0110] The analysis module 32 may correct the error error vector for determining at least one analysis parameter, at least one statistical parameter, an error distribution, and / or an estimated symbol error rate.

[0111] The measurement module 18 further includes a visualization module 36 connected to the analysis module 32.

[0112] The visualization module 36 is configured to generate joint visualization data of at least one analysis parameter and at least one statistical parameter.

[0113] The joint visualization data may further include visualization data for an estimated symbol error rate.

[0114] If the analysis module detects that the extracted reference signal is incorrect, the joint visualization data may further include a warning signal, such as a text message and / or a warning flag.

[0115] The joint visualization data may be displayed on a display 38 integrated into the measuring instrument 14.

[0116] Alternatively or additionally, the joint visualization data may be displayed on a display connected to the measuring instrument 14.

[0117] Certain embodiments disclosed herein, in particular the corresponding modules and / or units, utilize circuitry (e.g., one or more circuits) to implement the standards, protocols, methods, or techniques disclosed herein, operably couple two or more components, generate information, process information, analyze information, generate signals, encode / decode signals, convert signals, transmit and / or receive signals, control other devices, etc. Any type of circuitry may be used.

[0118] In one embodiment, the circuitry 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 electronics, or a combination thereof. In one embodiment, the circuitry includes hardware circuit implementations (e.g., implementations in analog circuitry, implementations in digital circuitry, and the like, and combinations thereof).

[0119] In one embodiment, the circuitry includes a combination of a circuit 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 of the protocols, methods, or techniques described herein. In one embodiment, the circuitry includes a circuit that requires software, firmware, and the like to operate, such as, for example, a microprocessor or a portion of a microprocessor. In one embodiment, the circuitry includes one or more processors or portions thereof and attendant software, firmware, hardware, and the like.

[0120] This application may refer to quantities and numbers. Unless otherwise specified, such quantities and numbers should not be considered limiting but rather exemplary of possible quantities or numbers associated with this application. Also in this regard, this application may use the term "plurality" to refer to a quantity or number. In this regard, the term "plurality" means any number greater than one, such as two, three, four, five, etc. The terms "about," "approximately," "close to," etc. mean plus or minus 5% of the stated value.

Claims

1. A measuring instrument, wherein the measuring instrument (14) comprises at least one input port (16) and a measurement module (18), Among them, The input port is configured to receive a radio frequency (RF) signal from a device under test (12), wherein the RF signal comprises a symbol sequence, wherein the measurement module (18) is configured to receive the RF signal from the input port (16), wherein the measurement module (18) comprises a reference signal module (26), wherein the reference signal module (26) is configured to generate a reference signal based on the received RF signal, wherein the reference signal comprises an extracted symbol sequence corresponding to the symbol sequence of the RF signal, wherein the measurement module (18) further comprises an error module (30), wherein the error module (30) is configured to determine an error vector based on the RF signal and based on the reference signal, and wherein the measurement module (18) further comprises an analysis module (32), wherein the analysis module (32) is configured to determine whether the reference signal is correct based on the determined error vector.

2. The measuring instrument according to claim 1, wherein, The analysis module (32) is configured to determine an error distribution based on the error vector, and wherein the analysis module (32) is configured to determine whether the reference signal is correct based on the determined error distribution.

3. The measuring instrument according to any one of the preceding claims, wherein, The reference signal module (26) is configured to demodulate the RF signal to obtain a demodulated RF signal, and wherein the reference signal module (26) is configured to generate the reference signal based on the demodulated RF signal.

4. The measuring instrument according to any one of the preceding claims, wherein, The analysis module (32) is configured to determine at least one analysis parameter, wherein the at least one analysis parameter is associated with the RF signal, and wherein the analysis module (32) is configured to determine at least one statistical parameter associated with the at least one analysis parameter based on the determined error vector, wherein the at least one statistical parameter indicates measurement uncertainty with respect to the at least one analysis parameter.

5. The measuring instrument according to claim 4, further comprising a visualization module (36), wherein the visualization module (36) is configured to generate joint visualization data of the at least one analysis parameter and the at least one statistical parameter.

6. The measuring instrument according to any one of the preceding claims, wherein, The analysis module (32) is configured to estimate a symbol error rate of the RF signal based on the determined error vector.

7. The measuring instrument according to claim 6, wherein, The analysis module (32) is configured to determine an error distribution based on the error vector, and wherein the analysis module (32) is configured to estimate the symbol error rate of the RF signal based on the determined error distribution.

8. The measuring instrument according to claim 7, wherein, The analysis module (32) is configured to estimate the symbol error rate based on a portion of the determined error distribution outside a decision boundary (34), in particular, wherein the analysis module (32) is configured to integrate over the portion of the determined error distribution outside the decision boundary (34) in order to estimate the symbol error rate.

9. The measuring instrument according to any one of the preceding claims, wherein, The analysis module (32) is configured to determine whether the reference signal is correct based on additional system information.

10. The measuring instrument according to any one of the preceding claims, wherein, The symbol sequence included in the RF signal is unknown to the measurement module (18).

11. The measuring instrument according to any one of the preceding claims, wherein, The modulation scheme of the RF signal is unknown to the measurement module (18).

12. The measuring instrument according to any one of the preceding claims, wherein, The analysis module (32) is configured to determine an error error vector, in particular an error component of the error error vector.

13. The measuring instrument according to claim 12, wherein, The analysis module (32) is configured to correct the determined error error vector.

14. The measuring instrument according to claim 12, wherein, The analysis module (32) is configured to discard the determined error error vector.

15. The measuring instrument according to any one of the preceding claims, wherein, The measuring instrument (14) is a signal analyzer, a spectrum analyzer or an oscilloscope.

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