detector module, signal processing module and measuring instrument

Abstract

A detector module (24) for a measuring instrument (12) is described. The detector module (24) comprises a first signal input (54), a second signal input (58) and an averaging sub-module (64). The first signal input (54) is configured to receive a first complex-valued measurement signal associated with an input signal received from a device under test (14). The second signal input (58) is configured to receive a second complex-valued measurement signal associated with the input signal received from the device under test (14). The averaging sub-module (64) is configured to determine an average of a complex conjugate of the first complex-valued measurement signal and the second complex-valued measurement signal over a predetermined number of samples, thereby obtaining a complex-valued average signal. The averaging sub-module (64) is configured to generate an output signal based on the complex-valued average signal. Furthermore, a signal processing module (18) and a measuring instrument (12) are described.

Description

TECHNICAL FIELD

[0001] The present invention generally relates to a detector module for a measuring instrument. The invention further relates to a signal processing module for a measuring instrument, and to a measuring instrument. BACKGROUND

[0002] Measuring detectors are used in order to map a higher number of measurement points to a lower number of output results. For example, a root-mean-square (RMS) detector is used in order to determine the average power of a signal, for example for noise analysis.

[0003] However, detectors such as RMS detectors are not able to distinguish between noise originating from a device under test (DUT) and noise added by the measuring instrument itself.

[0004] Therefore, if the measuring instrument has an inherent noise level of the same magnitude or even higher than the noise level of the device under test, the noise caused by the device under test cannot be reliably measured. Furthermore, small signals of the device under test below the inherent noise level of the measuring instrument cannot be detected.

[0005] A known solution to this problem is to perform a reference measurement without the device under test in the signal chain. The additional noise generated by the measuring instrument can be determined based on the reference measurement and can be subtracted in the respective measurement of the device under test. However, this only works reliably to a certain extent, up to about 10 dB.

[0006] However, performing an additional reference measurement requires additional time. Furthermore, the measuring instrument can behave differently when the device under test is connected to the measuring instrument and when the device under test is not connected to the measuring instrument. SUMMARY

[0007] It is therefore an object of the present invention to provide a detector module for a measuring instrument, a signal processing module for a measuring instrument, and a measuring instrument allowing for a faster analysis of the noise level of a device under test.

[0008] According to the invention, the problem is solved by a detector module for a measuring instrument. The detector module comprises a first signal input, a second signal input, and an averaging sub-module. The first signal input is configured to receive a first complex-valued measurement signal associated with an input signal received from a device under test. The second signal input is configured to receive a second complex-valued measurement signal associated with the input signal received from the device under test. The averaging sub-module is configured to determine a combined average of the complex conjugate of the first complex-valued measurement signal and the second complex-valued measurement signal over a predetermined number of samples, thereby obtaining a complex-valued average signal. The averaging sub-module is configured to generate an output signal based on the complex-valued average signal.

[0009] The detector module according to the present application is based on the idea that noise originating from sources other than the device under test is selectively removed from the input signal by averaging the cross-correlation between the first complex-valued measurement signal and the second complex-valued measurement signal over a predetermined number of samples.

[0010] Herein, both the amplitude and the phase of the complex-valued measurement signals are considered for determining the combined average. In other words, the complex-valued measurement signals each comprise amplitude information and phase information which are considered for determining the combined average. Thus, the combined average can also be referred to as a "vector average".

[0011] Both the first complex-valued measurement signal and the second complex-valued measurement signal are associated with the same input signal received from the device under test.

[0012] Thus, by performing the combined averaging as described above, the resulting complex-valued average signal comprises significantly reduced noise from sources other than the device under test.

[0013] This is due to the fact that both the first complex-valued measurement signal and the second complex-valued measurement signal contain noise originating from the device under test such that these parts of the complex-valued measurement signals are correlated with each other and do not cancel out when performing the combined averaging.

[0014] On the other hand, noise from other sources, e.g. from measurement channels which are parallel to the input signal processing, are not correlated with each other and at least partially cancel out when performing the combined averaging.

[0015] Thus, the detector module according to the present application effectively reduces the noise level without compromising the ability to analyze the noise contribution of the device under test.

[0016] In fact, the detector module according to the present application allows for a fast suppression of the inherent noise of the measurement instrument such that, for example, the noise level of the device under test and / or small amplitude signals of the device under test can be reliably measured.

[0017] In addition, the detector module according to the present application allows for an increased signal-to-noise ratio of the measurement of the signal of the device under test, in particular of the measurement of small amplitude signals of the device under test.

[0018] Moreover, additional reference measurements for determining the noise contribution of components in the signal chain other than the device under test are not necessary. Thus, the noise contribution of the device under test can be reliably analyzed based on a single measurement.

[0019] The averaging sub-module can comprise a multiplication unit, wherein the multiplication unit is configured to multiply the first complex-valued measurement signal with a complex conjugate of the second complex-valued measurement signal, thereby obtaining a complex-valued multiplication signal.

[0020] The averaging submodule can be further configured to average the complex-valued multiplication signal over a predetermined number of samples, thereby obtaining a complex-valued average signal.

[0021] If the first and second complex-valued measurement signals are in the frequency domain, the complex-valued average signal corresponds to a cross-correlation between the first and second complex-valued measurement signals averaged over the predetermined number of samples. This is due to the fact that multiplication of complex-valued measurement signals in the frequency domain corresponds to convolution of complex-valued measurement signals in the time domain.

[0022] In other words, the complex-valued average signal can correspond to a trace of a cross-correlation matrix of the first and second complex-valued measurement signals divided by the predetermined number of samples.

[0023] Hence, the detector module according to the present application can colloquially be referred to as a "cross-correlation detector" or "x-corr detector".

[0024] The predetermined number of samples can be coupled to a sweep time parameter of the spectrum analyzer. Hence, a larger sweep time parameter can be associated with a larger predetermined number of samples.

[0025] According to an aspect of the present application, the averaging submodule is configured to determine an absolute value of the complex-valued average signal in order to generate the output signal. Alternatively or additionally, the averaging submodule is configured to determine a real part of the complex-valued average signal in order to generate the output signal. The absolute value of the complex-valued average signal is a measure for the power of the desired signal (also referred to as "useful signal") of the device under test (including noise contributions of the device under test) since other noise contributions are partially or completely cancelled due to the performed combined averaging. It turns out that the real part of the complex-valued average signal is also a suitable measure for the power of the desired signal of the device under test (including noise contributions of the device under test), especially if the predetermined number of samples is large. However, the use of the real part can not be appropriate in certain situations, e.g. if the real part is negative.

[0026] It turns out that the undesired noise contributions are reduced by approximately 5•log 10 (N) dB or reduced by where N is the predetermined number of samples.

[0027] The averaging submodule can switch between an absolute value mode in which the averaging submodule is configured to determine an absolute value of the complex-valued average signal and a real part mode in which the averaging submodule is configured to determine a real part of the complex-valued average signal. In other words, a user can select which mode the averaging submodule uses.

[0028] According to another aspect of the present disclosure, the first complex-valued measurement signal and the second complex-valued measurement signal are established as IQ signals, respectively. Alternatively or additionally, the first complex-valued measurement signal and the second complex-valued measurement signal are established as Fourier-transformed signals, respectively.

[0029] If the complex-valued measurement signals are established as IQ signals, respectively, the averaging sub-module is configured to perform a combined averaging on the IQ signals as described above. Thus, the averaging sub-module averages several consecutive samples of the IQ signals as described above.

[0030] If the complex-valued measurement signals are established as Fourier-transformed signals, respectively, the averaging sub-module averages several consecutive samples of the Fourier-transformed signals in the time domain and / or in the frequency domain. In other words, the averaging sub-module can perform a combined averaging on subsequent samples of the Fourier-transformed signals and / or on adjacent bins of the Fourier-transformed signals.

[0031] In embodiments of the present invention, the predetermined number of samples is adjustable. Generally, increasing the predetermined number of samples results in an enhanced noise suppression, since the larger the predetermined number of samples, the more uncorrelated parts of the noise, i.e. unwanted noise parts, are suppressed. Since the predetermined number of samples is adjustable, the detector module can adapt to different requirements ranging from high resolution to high noise suppression.

[0032] In further embodiments of the present invention, the detector module is switchable between different detector modes, wherein the detector modes comprise a cross-correlation detector mode and one or several of the following detector modes: a sample detector mode, a minimum detector mode, a maximum detector mode, an auto-peak detector mode, an average detector mode, and a root-mean-square detector mode. In other words, the detector module is configured to provide one or several output signals (also referred to as "traces"), wherein different mathematical operations are applied to the measurement signals in different detector modes.

[0033] In fact, for the sample detector mode, the minimum detector mode, the maximum detector mode, the auto-peak detector mode, the average detector mode, and the root-mean-square detector mode, at least one of the complex-valued measurement signals can be converted into a real-valued measurement signal before being processed by the detector module.

[0034] For example, at least one converter unit can be arranged upstream of the first signal input and / or upstream of the second signal input, wherein the at least one converter unit is configured to convert the first complex-valued measurement signal and / or the second complex-valued measurement signal into a real-valued measurement signal.

[0035] Alternatively, the detector module can comprise a converter unit.

[0036] In fact, in the sample detector mode, the minimum detector mode, the maximum detector mode, the automatic peak detector mode, the average detector mode and the root mean square detector mode, only one complex-valued measurement signal can be converted into a real-valued measurement signal and processed by the detector module.

[0037] More than one detector mode can be activated at a time, such that the detector module provides at least two output signals corresponding to at least two different detector modes.

[0038] The output signals generated by the detector module can be displayed on a display. In particular, the at least two output signals can be displayed on the display simultaneously.

[0039] The user can select one or several detector modes to be applied to the complex-valued measurement signal, e.g. by means of a suitable user interface of a measurement instrument comprising the detector module.

[0040] The different modes of the detector module can correspond to different detectors that can be selected by the user.

[0041] According to the present application, the problem is further solved by a signal processing module for a measurement instrument. The signal processing module comprises a detector module as described above and a measurement input. The signal processing module comprises two parallel measurement channels, wherein the two parallel measurement channels are each connected to the measurement input, such that an input signal received via the measurement input is forwarded to the two parallel measurement channels. A first of the two parallel measurement channels is connected with a first signal input and a second of the two parallel measurement channels is connected with a second signal input. The first of the two parallel measurement channels is configured to process the input signal, thereby generating a first complex-valued measurement signal. The second of the two parallel measurement channels is configured to process the input signal, thereby generating a second complex-valued measurement signal.

[0042] wherein the first signal input of the detector module is arranged downstream of the first of the two parallel measurement channels and the second signal input of the detector module is arranged downstream of the second of the two parallel measurement channels.

[0043] In particular, the signal processing module comprises exactly two parallel measurement channels connected to the measurement input.

[0044] With regard to further advantages and properties of the signal processing module, reference is made to the explanations given above with regard to the detector module, which are also applicable to the signal processing module and vice versa.

[0045] According to one aspect of the present application, the two parallel measurement channels are functionally identical. In other words, the two parallel measurement channels are identically constructed, i.e. they comprise identically constructed electronic components. Thus, the two parallel measurement channels process the input signal received from the device under test in the same way. However, the noise originating from the first one of the two parallel measurement channels is uncorrelated with the noise originating from the second one of the two parallel measurement channels and thus cancels out when performing the combined averaging of the complex-valued measurement signals.

[0046] According to another aspect of the present application, the two parallel measurement channels each comprise an analog-to-digital converter. The analog-to-digital converters can be functionally identical, i.e. identically constructed. Thus, the additional noise generated by the analog-to-digital converters is uncorrelated with each other and thus cancels out when performing the combined averaging of the complex-valued measurement signals.

[0047] In embodiments of the present application, the two parallel measurement channels are synchronized. In other words, the same portion of the input signal is processed by both parallel measurement channels at the same time, such that samples corresponding to the same portion of the input signal are forwarded to the first input and the second input at the same time. This ensures that the desired signal (also referred to as "useful signal") comprising noise generated by the device under test does not cancel out when performing the combined averaging.

[0048] In further embodiments of the present application, the two parallel measurement channels each comprise a mixer sub-module, wherein the mixer sub-modules are configured to convert the input signal into an IQ signal, respectively. Thus, the complex-valued measurement signals forwarded to the detector module can be established as IQ signals, respectively. Thus, the averaging sub-module averages several consecutive samples of the IQ signals, as described above.

[0049] In particular, the two parallel measurement channels each comprise a resolution bandwidth (RBW) filter. In particular, the RBW filters are functionally identical, i.e. identically constructed. The RBW filters determine the resolution bandwidth of the signal processing module and thus of the measurement instrument comprising the signal processing module.

[0050] The resolution bandwidth can be fixed or can be adjustable, in particular by a user via a suitable user interface.

[0051] According to another aspect of the present application, the two parallel measurement channels each comprise a Fourier transformation unit, wherein the Fourier transformation units are each configured to determine a Fourier transform of the respective signal processed in the respective measurement channel over a predetermined time interval, in particular wherein the predetermined time interval is adjustable. In other words, the Fourier transformation units determine a series of Fourier transforms of the respective signal processed over the predetermined time interval. Therein, the time intervals associated with consecutive Fourier transforms can overlap. Thus, the Fourier-transformed signal comprises time and frequency information.

[0052] Accordingly, the averaging sub-module of the detector module can average several consecutive samples of the Fourier-transformed signal in the time domain and / or in the frequency domain. In other words, the averaging sub-module can perform a combined average over subsequent samples of the Fourier-transformed signal and / or over adjacent bins of the Fourier-transformed signal.

[0053] In particular, the Fourier transformation units are each configured to determine a fast Fourier transform (FFT) of the respective signal processed.

[0054] The Fourier transform of the respective signal can be determined on-line, i.e. in real-time or on-site. In particular, the Fourier transform can be determined and subsequently processed in real-time by the detector module, such that a real-time analysis of the input signal received from the device under test is provided.

[0055] Alternatively or additionally, the Fourier transform of the respective signal can be determined off-line, i.e. based on samples of the input signal of the device under test stored in a measurement memory. In particular, the Fourier transform can be determined and subsequently processed off-line by the detector module.

[0056] The first and second signal inputs can be selectively connectable to the measurement memory and / or the parallel measurement channels. In other words, the signal processing module and the detector module can process input signals received from the device under test in real-time. However, the detector module can also process input signals associated with the device under test that have been previously processed by the parallel measurement channels and recorded in the measurement memory.

[0057] According to the present application, the problem is further solved by a measuring instrument. The measuring instrument comprises a detector module as described above and / or a signal processing module as described above.

[0058] With regard to further advantages and properties of the measuring instrument, reference is made to the explanations given above with regard to the detector module and the signal processing module, which are also applicable to the measuring instrument and vice versa.

[0059] The measuring instrument can be set up as a signal analyzer, as a spectrum analyzer, as an electromagnetic interference (EMI) test receiver, as an EMI measurement receiver, as an oscilloscope, as a digital oscilloscope, or as a power sensor.

[0060] It is to be understood, however, that the measuring instrument can be set up as any other suitable measuring instrument.

[0061] According to an aspect of the present application, the measuring instrument comprises a display, wherein the display is configured to display the output signal of the detector module. The display can be configured to display several output signals of the detector module simultaneously, in particular several output signals corresponding to several detector modes of the detector module described above.

[0062] The measuring instrument can further comprise a user interface. The user interface can comprise input means allowing a user to set operating parameters of the measuring instrument, such as detector mode, predetermined number of samples, resolution bandwidth, etc. BRIEF DESCRIPTION OF DRAWINGS

[0063] The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily apparent as they are better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0064] Figure 1 A measuring instrument according to the present application is schematically illustrated;

[0065] Figure 2 A user interface of the measuring instrument of Figure 1 is schematically illustrated;

[0066] Figure 3 A table illustrating mathematical operations performed by the detector module of the measuring instrument of Figure 1 is shown;

[0067] Figure 4 A graph illustrating a combined average performed by the measuring instrument of Figure 1 is shown;

[0068] Figure 5 A further variant embodiment of the measuring instrument of Figure 1 is schematically illustrated; and

[0069] Figure 6 A graph illustrating a combined average performed by the measuring instrument of Figure 5 is shown. DETAILED DESCRIPTION

[0070] The detailed description set forth below (with reference to the accompanying drawings) is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments in which the disclosed subject matter can be practiced. Each embodiment described in this disclosure is provided merely as an example or illustration of the disclosed subject matter, and should not be construed as preferred or superior over other embodiments. The illustrative examples provided herein are not meant to be exhaustive or limiting to the claimed subject matter.

[0071] For the purposes of this disclosure, the phrase "at least one of A, B, and C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C) for example, and includes all further possible permutations of the elements listed. In other words, the term "at least one of A and B" generally means "A and / or B", i.e. either "A" alone, "B" alone, or "A and B".

[0072] Figure 1 A measurement system 10 comprising a measuring instrument 12 and a device under test 14 is schematically shown.

[0073] Generally, the measuring instrument 12 is configured to analyze an input signal received from the device under test 14 in order to analyze certain properties of the device under test 14.

[0074] For example, the measuring instrument 12 can be a signal analyzer, a spectrum analyzer, an electromagnetic interference (EMI) test receiver, an EMI measurement receiver, an oscilloscope, a digital oscilloscope, or a power sensor.

[0075] However, the measuring instrument 12 can be established as any other type of measuring instrument depending on which aspects of the performance of the device under test 14 are to be tested.

[0076] The device under test 14 can be established as any electronic device configured to generate a radio-frequency (RF) signal. For example, the device under test 14 comprises one or several electronic circuits generating an RF signal, wherein the performance of the electronic circuits is evaluated by means of the measuring instrument 12.

[0077] The device under test 14 is connected to the measuring instrument 12 in a signal transmission manner.

[0078] In and hereinafter, the term "connected in a signal transmission manner" is understood to mean a cable-based or wireless connection configured to transmit signals between the respective devices or components.

[0079] For example, the device under test 14 is connected to a measurement input 16 of the measuring instrument 12 via a suitable cable and a suitable connector, such that an electrical signal output by the device under test 14 is transmitted from the device under test 14 to the measuring instrument via the cable.

[0080] Alternatively, the device under test 14 can transmit a radio electromagnetic signal, which is received via an RF antenna connected to the measurement input 16.

[0081] Alternatively, a measurement probe can be connected to the measurement input 16, wherein the measurement probe is configured to pick up electrical signals from the device under test 14 by contacting corresponding contact points of the device under test 14.

[0082] The measurement instrument 12 comprises a signal processing module 18 having an RF front end 20, a digital back end 22 and a detector module 24.

[0083] In the following and in the following, the terms "module" and "unit" are understood to describe a suitable hardware, a suitable software, or a combination of hardware and software configured to have a certain functionality.

[0084] The hardware can comprise, among others, a CPU, a GPU, a FPGA, an ASIC or other types of electronic circuits.

[0085] The measurement instrument 12 comprises a first measurement channel 26 and a second measurement channel 28, each connected to the measurement input 16.

[0086] The measurement channels 26, 28 are arranged in parallel, such that an input signal received from the device under test 14 via the measurement input 16 is forwarded to and processed by both measurement channels 26, 28 in parallel.

[0087] The measurement channels 26, 28 are functionally identical, i.e. the electronic components of the first measurement channel 26 are identical in construction to the electronic components of the second measurement channel 28.

[0088] Therefore, in the following only the first measurement channel 26 is described, since the explanations given in the following equally apply to the second measurement channel 28.

[0089] The first measurement channel 26 comprises a first mixer sub-module 30 associated with the RF front end 20 of the measurement instrument 12.

[0090] Generally, the first mixer sub-module 30 is configured to down-convert the input signal received from the device under test 14 to an intermediate frequency suitable for being processed by the electronic components downstream of the first mixer sub-module 30.

[0091] Generally, the first mixer sub-module 30 comprises a local oscillator input 32 configured to receive a local oscillator signal.

[0092] The first mixer sub-module 30 further comprises a mixer unit 34 configured to mix the input signal received from the device under test 14 with the local oscillator signal, and a bandpass filter 36 configured to appropriately filter the resulting mixed signal in order to down-convert the input signal to the intermediate frequency.

[0093] In particular, the frequency of the local oscillator signal received via the oscillator input 42 can be constant. Alternatively, the frequency of the local oscillator signal received via the oscillator input 42 can vary over time, i.e. a frequency sweep can be applied to the local oscillator signal.

[0094] The first measurement channel 26 further comprises an analog-to-digital converter (ADC) 38 of the signal, which is configured to digitize the signal output by the first mixer sub-module 30.

[0095] The first measurement channel 26 further comprises a second mixer sub-module 40 having an oscillator input 42, a mixer unit 44 and a filter unit 46.

[0096] In general, the second mixer sub-module 40 is configured to mix the digitized signal received from the ADC 38 into a complex baseband by means of any suitable technique known in the art.

[0097] In particular, the second mixer sub-module 40 can be configured to generate an IQ signal on the basis of the digitized signal received from the ADC 38 by means of any suitable technique known in the art.

[0098] In particular, the frequency of the local oscillator signal received via the oscillator input 42 can be constant. Alternatively, the frequency of the local oscillator signal received via the oscillator input 42 can vary over time, i.e. a frequency sweep can be applied to the local oscillator signal.

[0099] In Figure 1 In the exemplary embodiment shown, the first measurement channel 26 further comprises a down-converter unit 48 and a resolution bandwidth (RBW) filter 50.

[0100] The down-converter unit 48 is configured to down-sample the signal received from the second mixer sub-module 40 by a predetermined factor, i.e. to reduce the number of samples by a predetermined factor.

[0101] The RBW filter 50 determines the resolution bandwidth of the first measurement channel 26.

[0102] The resolution bandwidth can be fixed or can be adjustable. In particular, the resolution bandwidth can be adjusted by a user via a user interface 52 of the measuring instrument 12.

[0103] In summary, the input signal received from the device under test 14 is processed by the electronic components of the first measurement channel 26 described above, thereby generating a first complex-valued measurement signal.

[0104] Likewise, the input signal received from the device under test 14 is processed by the electronic components of the second measurement channel 28, thereby generating a second complex-valued measurement signal.

[0105] In which, the two parallel measurement channels 26, 28 are synchronized. In other words, the same portion of the input signal is processed by both parallel measurement channels 26, 28 at the same time.

[0106] The first complex-valued measurement signal is forwarded to a first signal input 54 of the detector module 24.

[0107] Alternatively or additionally, the first complex-valued measurement signal is saved in a measurement memory 56 of the measuring instrument 12.

[0108] The second complex-valued measurement signal is forwarded to a second signal input 58 of the detector module 24.

[0109] Alternatively or additionally, the second complex-valued measurement signal is saved in the measurement memory 56.

[0110] Generally, the detector module 24 is configured to apply a mathematical operation to the complex-valued measurement signals in order to transform the complex-valued measurement signals into an output signal, i.e. into a measurement trace to be displayed on a display 60 of the measuring instrument 12.

[0111] In which, the input signal can be received from the device under test 14 and processed in real-time by the signal processing module 18, in particular by the detector module 24.

[0112] Alternatively, the input signal can be received from the device under test 14, processed by the measurement channels 26, 28 as described above, and the complex-valued measurement signals can be saved in the measurement memory 56.

[0113] The saved complex-valued measurement signals can later be forwarded to the signal inputs 54, 58 for further processing by the detector module 24.

[0114] The type of mathematical operation applied to the measurement signals depends on the detector mode of the detector module 24.

[0115] The detector module 24 can be switchable between different detector modes, wherein the detector modes include a cross-correlation detector mode and one or several of the following detector modes: a sample detector mode, a minimum detector mode, a maximum detector mode, an auto-peak detector mode, an average detector mode, and a root-mean-square detector mode.

[0116] In fact, for the sample detector mode, the minimum detector mode, the maximum detector mode, the auto-peak detector mode, the average detector mode, and the root-mean-square detector mode, at least one of the complex-valued measurement signals can be converted into a real-valued measurement signal before being processed by the detector module 24.

[0117] For example, the at least one converter unit can be arranged upstream of the first signal input and / or upstream of the second signal input, wherein the at least one converter unit is configured to convert the first complex-valued measurement signal and / or the second complex-valued measurement signal into a real-valued measurement signal.

[0118] Alternatively, the detector module 24 can comprise a converter unit.

[0119] In fact, in the sample detector mode, the minimum detector mode, the maximum detector mode, the automatic peak detector mode, the average detector mode and the root mean square detector mode, only one complex-valued measurement signal can be converted into a real-valued measurement signal and processed by the detector module 24.

[0120] For example, the user can select one or several detector modes to be applied to the complex-valued measurement signals via the user interface 52.

[0121] Figure 2 An exemplary embodiment of the user interface 52 is shown. As Figure 2 shown, the user can select one or several detector modes (‘Trace 1’ to ‘Trace 6’) from a drop-down menu 62. Figure 2

[0122] Furthermore, the user can adjust further operating parameters of the detector module 24, the signal processing module 18 and / or the measurement instrument 12 by means of the user interface 52.

[0123] However, it is to be understood that any other type of user interface can be used.

[0124] Mathematical operations applied to the measurement signals in the different detector modes are shown in Figure 3 wherein a table of mathematical operations is shown.

[0125] In the average detector mode, y det denotes the measurement trace, whereas x(k) denotes the k-th sample of the respective measurement signal. Furthermore, N denotes a predetermined number of samples over which the real-valued measurement signal is averaged in the average detector mode and in the root mean square detector mode.

[0126] In the last row, N denotes a predetermined number of samples over which the complex-valued measurement signals xi(k) and x2(k) are averaged in the cross-correlation detector mode. In the last row, N denotes a predetermined number of samples over which the complex-valued measurement signals xi(k) and x2(k) are averaged in the cross-correlation detector mode.

[0127] In the following, the cross-correlation detector mode is explained in more detail. Figure 1

[0128] In the cross-correlation detector mode, the detector module 24 comprises an averaging sub-module 64 having a multiplication unit 66, an averaging unit 68 and an output unit 70.​​

[0129] The multiplication unit 66 is configured to multiply the first complex-valued measurement signal y1(k) with the complex conjugate of the second complex-valued measurement signal , thereby obtaining a complex-valued multiplication signal y(k), i.e.

[0130]

[0131] The averaging unit 68 is configured to average the complex-valued multiplication signal over a predetermined number of samples N, thereby obtaining a complex-valued average signal.

[0132] Thus, if y1(k) and are in the frequency domain, the complex-valued average signal can correspond to the trace of the cross-correlation matrix of the first and second complex-valued measurement signals divided by the predetermined number of samples N.

[0133] The output unit 70 determines the absolute value (Abs) of the complex-valued average signal or the real part of the complex-valued average signal, thereby obtaining the output signal of the detector module 24.

[0134] This way, noise originating from the measurement channels 26, 28 is at least partially cancelled out, while the desired signal of the device under test 14, including noise contributions, is preserved.

[0135] This can be seen as follows. The complex-valued measurement signals output by the digital backend 22 can be split into a relevant part (a) from the device under test 14 and two uncorrelated noise parts (n1 and n2) from the measurement channels 26, 28:

[0136] y1 = a + n1

[0137] y2 = a + n2

[0138] The output signal (Det) of the detector module 24 is then

[0139]

[0140] The first term, i.e. 1 / N∑|a i | 2 , corresponds to the average power over time of the input signal received from the device under test 14, which corresponds to the desired detector result.

[0141] The other terms correspond to the multiplication of uncorrelated signals and are thus at least partially cancelled out. More precisely, the other terms correspond to the noise originating from the measurement channels 26, 28.

[0142] In fact, it turns out that these undesired noise contributions are reduced by approximately 5 · log 10 (N) dB or

[0143] The result of the output signal Det given above corresponds to the absolute value of the complex-valued average signal.

[0144] Alternatively, the output signal Det can be given by

[0145]

[0146] From a comparison of the two possible results of the output signal Det it can be seen that both results are identical for N→∞.

[0147] The predetermined number of samples N can be adjustable, e.g. via the user interface 52.

[0148] Generally, increasing the predetermined number of samples N results in an enhanced noise suppression, since the more the predetermined number of samples N is, the more the non-correlated part of the noise, i.e. the undesired noise part, is suppressed.

[0149] As shown in Figure 4 Increasing the predetermined number of samples N results in a smoothing of the output signal, i.e. the measurement trace, since the N samples of the complex-valued measurement signal Figure 4 are shown as "Chl" and "Ch2" in Figure 4 are mapped onto a single output signal sample

[0150] Since the predetermined number of samples N is adjustable, the detector module 24 can be adapted to different requirements, ranging from high resolution to high noise suppression.

[0151] The output signal provided by the averaging sub-module 64 is displayed on the display 60 of the measuring instrument 12.

[0152] Figure 5 A second variant embodiment of the measurement system 10 is shown, wherein only the differences compared to the first variant embodiment described above are explained in the following.

[0153] In contrast to the first variant embodiment described above, the RBW filter 50 is replaced by a window unit 72 and a Fourier transform unit 74.

[0154] The window unit 72 is configured to apply a window function to the signal output by the down-converter unit 48, thereby determining the resolution bandwidth of the measurement channels 26, 28.

[0155] The Fourier transform unit 74 is configured to determine a fast Fourier transform (FFT) of the signal output by the window unit 72.

[0156] Thus, in the second variant embodiment of the measurement system 10, the complex-valued measurement signal is established as a Fourier-transformed signal, respectively.

[0157] In other words, the Fourier transform unit 74 determines a series of Fourier transforms of the respective signal processed over a predetermined time interval. In which, the time interval associated with the successive Fourier transforms can overlap.

[0158] It is noted that, alternatively or additionally to Figure 5 In the variant embodiment shown, the measurement memory 56 can be connected to the down-converter unit 48 upstream of the down-converter unit 48 in the down-converter unit 48.

[0159] Furthermore, the measurement memory 56 can be connected to the window unit 72 upstream of the window unit 72 in the window unit 72.

[0160] Thus, the signal output by the down-converter unit 48 can be saved in the measurement memory 56 and can be processed later by the window unit 72, the Fourier transform unit 72 and the detector module 24.

[0161] In other words, the Fourier transforms can be determined and subsequently processed offline by the detector module 24.

[0162] It is understood, however, that the Fourier transforms can be determined and subsequently processed in real time by the detector module 24, so as to provide a real-time analysis of the input signal received from the device under test 14.

[0163] The multiplication unit 66 multiplies the first complex-valued measurement signal FFT1(k) with the complex conjugate of the second complex-valued measurement signal FFT2(k), thereby obtaining a complex-valued multiplication signal FFT(k), i.e.

[0164] FFT(k) = FFT1(k) · FFT2(k). *

[0165] As Figure 6 shown, the signals of the Fourier transforms (FFT1, FFT2, etc.), i.e. the complex-valued measurement signals, comprise time and frequency information.

[0166] Thus, the averaging sub-module 64 can average the signals of the Fourier transforms over a predetermined number of samples N in the time domain.

[0167] Alternatively or additionally, the averaging sub-module 64 can average the signals of the Fourier transforms over a predetermined number of samples in the frequency domain.

[0168] In other words, the averaging sub-module 64 can perform a combined average over subsequent samples of the signals of the Fourier transforms and / or over adjacent bins of the signals of the Fourier transforms.

[0169] ​Certain embodiments of the present disclosure, particularly 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 can be used.

[0170] In embodiments, 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), etc., or any combination thereof, and can include discrete digital or analog circuit elements or electronics, or combinations thereof. In embodiments, the circuitry includes a hardware-only implementation of circuitry (e.g., an implementation in analog circuitry, an implementation in digital circuitry, etc., and combinations thereof).

[0171] In embodiments, the circuitry includes a combination of circuitry and a computer program product having software or firmware instructions stored on one or more computer-readable memories that work in coordination to cause devices to perform one or more of the protocols, methods, or techniques described herein. In embodiments, the circuitry includes circuitry, such as, for example, a microprocessor or portions thereof, that requires software, firmware, etc. for operation. In embodiments, the circuitry includes one or more processors or portions thereof and accompanying software, firmware, hardware, etc.

[0172] This application can refer to quantities and numbers. Unless specifically stated, these 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 can use the term “a plurality” to refer to quantities or numbers. In this regard, the term “a plurality” means any number more than one, e.g., two, three, four, five, etc. The terms “about,” “approximately,” “nearly,” etc. mean plus or minus 5% of the stated value.

Claims

1. A detector module for a measuring instrument (12), wherein the detector module (24) comprising a first signal input (54), a second signal input (58) and an averaging submodule (64), wherein the first signal input (54) is configured to receive a first complex-valued measurement signal associated with an input signal received from a device under test (14), wherein the second signal input (58) is configured to receive a second complex-valued measurement signal associated with the input signal received from the device under test (14), characterized in that wherein the averaging submodule (64) is configured to determine a combined average of the complex conjugate of the first complex-valued measurement signal and the second complex-valued measurement signal over a predetermined number of samples, thereby obtaining a complex-valued average signal, wherein the averaging submodule (64) is configured to generate an output signal based on the complex-valued average signal, and wherein the detector module (24) is capable of switching between different detector modes, wherein the detector modes comprise a cross-correlation detector mode and one or more of the following detector modes: a sample detector mode, a minimum detector mode, a maximum detector mode, an automatic peak detector mode, an average detector mode and a root mean square detector mode.

2. The detector module of claim 1, wherein, the averaging submodule (64) is configured to determine an absolute value of the complex-valued average signal in order to generate the output signal, and / or wherein the averaging submodule (64) is configured to determine a real part of the complex-valued average signal in order to generate the output signal.

3. The detector module of claim 1, wherein, the first complex-valued measurement signal and the second complex-valued measurement signal are each established as an IQ signal, and / or wherein the first complex-valued measurement signal and the second complex-valued measurement signal are each established as a Fourier-transformed signal.

4. The detector module of claim 1, wherein, the predetermined number of samples is adjustable.

5. A signal processing module for a measuring instrument (12) comprising a detector module (24) according to any one of the preceding claims and a measurement input (16), wherein the signal processing module (18) comprising two parallel measurement channels (26, 28), wherein the two parallel measurement channels (26, 28) are each connected to the measurement input (16) such that an input signal received via the measurement input (16) is forwarded to the two parallel measurement channels (26, 28), wherein a first one of the two parallel measurement channels (26, 28) is connected with the first signal input (54) and a second one of the two parallel measurement channels (26, 28) is connected with the second signal input (58), wherein the first one of the two parallel measurement channels (26, 28) is configured to process the input signal thereby generating a first complex-valued measurement signal, and wherein the second one of the two parallel measurement channels (26, 28) is configured to process the input signal thereby generating a second complex-valued measurement signal.

6. The signal processing module of claim 5, wherein, the two parallel measurement channels (26, 28) are functionally identical.

7. The signal processing module of claim 5, wherein, The two parallel measurement channels (26, 28) each comprise an analog-to-digital converter (38).

8. The signal processing module of claim 5, wherein, The two parallel measurement channels (26, 28) are synchronized.

9. The signal processing module of claim 5, wherein, The two parallel measurement channels (26, 28) each comprise a mixer sub-module (40), wherein the mixer sub-modules (40) are configured to convert the input signals to IQ signals, respectively.

10. The signal processing module of claim 5, wherein, The two parallel measurement channels (26, 28) each comprise a resolution bandwidth filter (50).

11. The signal processing module of claim 5, wherein, The two parallel measurement channels (26, 28) each comprise a Fourier transform unit (74), wherein the Fourier transform units (74) are each configured to determine a Fourier transform of the respective signal processed in the respective measurement channel over a predetermined time interval, wherein the predetermined time interval is adjustable.

12. The signal processing module of claim 5, wherein, The first signal input (54) and the second signal input (58) are selectively connectable to a measurement memory (56) and / or the parallel measurement channels (26, 28).

13. A measuring instrument comprising a detector module (24) according to any one of claims 1 to 4 and / or a signal processing module (18) according to any one of claims 5 to 12.

14. Measuring instrument according to claim 13, wherein The measuring instrument (12) comprises a display (60), wherein the display (60) is configured to display the output signal of the detector module (24). The measuring instrument (12) comprises a display (60), wherein the display (60) is configured to display the output signal of the detector module (24).

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