Test and / or measurement system and method for calibrating test and / or measurement system

Abstract

The invention relates to a test and / or measurement system and a method for calibrating a test and / or measurement system. The system includes: an RF signal source that generates an RF excitation signal; a device port; a signal path electrically connecting the RF signal source to the device port; a measurement unit coupled to the signal path, where the measurement unit is adapted to measure an RF excitation signal transmitted to the device port via the signal path and a measurement signal received at the device port; and at least one bias device coupled to the signal path, where the bias device includes a DC input port that receives a DC bias signal, where the bias device couples the received DC bias signal into the signal path. The system is operable in a calibration mode during which at least four different calibration criteria are alternately connected to the device port. The system is configured to couple the DC bias signal into the signal path via the bias during connection of at least one but not all of the calibration standards.

Description

Technical Field

[0001] The present invention relates to a test and / or measurement system, such as a vector network analyzer (VNA), and to a method for calibrating a test and / or measurement system. Background Art

[0002] A vector network analyzer (VNA) is a device used to measure the RF performance of a radio frequency (RF) device under test (DUT). A VNA can be used to characterize the scattering parameters (S-parameters) of a DUT.

[0003] Regular calibration of a VNA setup is critical to achieving accurate and repeatable VNA measurements. To calibrate a VNA, a calibration routine is usually performed during which different calibration standards are connected to the VNA.

[0004] When characterizing certain DUTs (e.g., amplifiers) with a VNA, a DC voltage is applied to the DUT (so-called biasing). However, this DC voltage is usually not applied during calibration, since most calibration standards cannot dissipate much power. As a result, undesired effects originating from the DC signal, such as parasitic effects, are not taken into account during calibration and are then not compensated by the calibrated VNA during measurement. This can lead to measurement errors. Summary of the invention

[0005] It is therefore an object to provide an improved testing and / or measuring system and an improved method for calibrating a testing and / or measuring system which avoid the above-mentioned disadvantages.

[0006] The object of the present invention is achieved by the technical solution provided by the present invention. The present invention further defines an advantageous implementation method.

[0007] According to a first aspect, the invention relates to a test and / or measurement system, in particular a vector network analyzer (VNA). The test and / or measurement system comprises: an RF signal source, the RF signal source being configured to generate an RF excitation signal; a device port; a signal path, the signal path being arranged to electrically connect the RF signal source to the device port; and a measurement unit, the measurement unit being coupled to the signal path, wherein the measurement unit is adapted to measure the RF excitation signal transmitted to the device port via the signal path and the measurement signal received at the device port, wherein the measurement unit is configured to generate measurement values ​​representing respective measurement results. The test and / or measurement system further comprises: a processing unit, the processing unit being configured to receive the measurement values; and at least one biaser, the biaser being coupled to the signal path; wherein the biaser comprises a DC input port configured to receive a DC bias signal, wherein the biaser is arranged to couple the received DC bias signal into the signal path. The test and / or measurement system may be operated in a calibration mode, during which at least four different calibration standards are alternately connected to the device port; wherein, for each connected calibration standard, the measurement unit is configured to measure the RF excitation signal and the measurement signal; and wherein the test and / or measurement system is configured to couple the DC bias signal into the signal path during connection of at least one of the calibration standards, but not during connection of all of the calibration standards.

[0008] This achieves the advantage of taking the influence of the DC signal into account during calibration of the system.In this way, measurements of (active) DUTs with a calibrated system can be improved and measurement uncertainties can be reduced.

[0009] The measuring unit may be configured to measure the RF excitation signal and the measurement signal independently of each other. For example, the measuring unit may thereby measure the amplitude and / or phase of the RF excitation signal and the measurement signal.

[0010] The device port may be a test port and / or an RF port of a test and / or measurement system. For example, the device port is a coaxial port. The device port may be suitable for connecting a DUT to be measured or characterized.

[0011] The DC bias signal may be a voltage and / or a current signal.

[0012] The radio frequency (RF) excitation signal may be an AC and / or CW signal in the radio frequency or microwave range.

[0013] The measurement signal may be an RF signal or a signal comprising an RF signal component. For example, the measurement signal may be an RF signal superimposed by a DC voltage and / or current signal (eg, by a DC bias signal or a portion thereof).

[0014] The processing unit may be configured to receive the measurement values ​​in digital form from the measuring unit.Thereby, the processing unit and the measuring unit may be linked via a communication connection.

[0015] The processing unit may be a microprocessor, an FPGA or an ASIC.

[0016] In particular, the measurement value generated by the measuring unit represents or contains the result of a measurement of the RF excitation signal and the measurement signal.

[0017] For example, measurements of the RF excitation signal and the measurement signal with a calibration standard connected to each are calibration measurements.

[0018] In an embodiment, in the calibration mode, the processing unit is configured to calculate an error term for the test and / or measurement system based on the measurement values ​​received for each connected calibration standard.

[0019] In particular, the processing unit may be configured to calculate the error term based on measurements of the RF excitation signal and the measurement signal using at least four different calibration standards connected to the device port.

[0020] In one embodiment, the RF signal source is configured to sweep the RF excitation signal over a predetermined frequency range and / or a predetermined power range; wherein the processing unit is configured to receive the measurement values ​​for at least one of the calibration standards, preferably all of the calibration standards, for multiple frequencies and / or power levels within the corresponding range.

[0021] For example, the test and / or measurement system is configured to perform measurements on the RF excitation signal and the measurement signal against at least one, and preferably all, of the calibration standards for multiple frequencies and / or power levels of the RF excitation signal.

[0022] In an embodiment, the test and / or measurement system is configured to vary the level of the DC bias signal; wherein the processing unit is configured to receive the measured values ​​for at least one of the calibration standards for a plurality of DC bias signal levels.

[0023] Thus, the level of the DC bias signal may correspond to a signal or power level (e.g., a voltage and / or current level) of the DC bias signal. For example, the test and / or measurement system is configured to perform measurements on an RF excitation signal and a measurement signal using at least one calibration standard connected to a device port, while a DC bias signal having at least two different (power) levels is alternately coupled into the signal path.

[0024] For each connected calibration standard measured with an applied DC bias voltage, the processing unit may be configured to receive (from the measuring unit) a plurality of measured values ​​for different levels of the DC bias signal.

[0025] In one embodiment, the processing unit is configured to calculate a first set of error terms for a DC bias signal of a first level and to calculate at least a second set of error terms for a DC bias signal of at least a second level different from the first level.

[0026] In one embodiment, a device under test (DUT) may be connected to the device port; wherein the test and / or measurement system may be operated in a measurement mode, during which the test and / or measurement system is configured to calculate scattering parameters (S-parameters) of the DUT, wherein the scattering parameters are corrected by a set of error terms selected based on the level of a DC signal applied to the DUT.

[0027] The test and / or measurement system may be configured to apply a DC signal to the DUT during a measurement mode (eg, while in measurement mode).

[0028] The measurement mode may be a "normal operating mode" of the test and / or measurement system.

[0029] The selected set of error terms may be one of the set of error terms calculated during the calibration mode. Thus, if a set of error terms is calculated when a DC bias signal is applied whose signal level deviates from the signal level of the DC signal applied to the DUT by less than a threshold, then the set of error terms may be selected.

[0030] In one embodiment, the bias device is arranged between the RF signal source and the measuring unit, or the bias device is arranged between the measuring unit and the device port.

[0031] In one embodiment, the test and / or measurement system includes a DC signal generator, which is configured to generate the DC bias signal having a determined voltage and / or current level; wherein the DC signal generator is arranged in the housing of the test and / or measurement system and is connected to the DC input port of the bias generator.

[0032] In one embodiment, the DC input port of the bias device can be connected to an external DC signal generator arranged outside the housing of the test and / or measurement system; wherein the test and / or measurement system is configured to control the external DC signal generator to generate the DC bias signal having a determined voltage and / or current level.

[0033] For example, the test and / or measurement system (eg a central unit of the test and / or measurement system) is connected to the external DC signal generator via a data connection.

[0034] In one embodiment, the measurement unit includes: a first directional coupler, which is configured to forward at least a portion of the RF excitation signal from the signal path; a second directional coupler, which is configured to forward at least a portion of the measurement signal from the signal path; a first mixing stage, which is configured to down-convert the portion of the RF excitation signal; and a second mixing stage, which is configured to down-convert the portion of the measurement signal.

[0035] In an embodiment, the measuring unit further comprises a digitizing unit configured to simultaneously measure the down-converted portion of the RF excitation signal and the down-converted portion of the measurement signal.

[0036] In one embodiment, the first directional coupler is configured to decouple the DC bias signal from the first mixing stage; and the second directional coupler is configured to decouple the DC bias signal from the second mixing stage.

[0037] In one embodiment, the test and / or measurement system comprises: a first attenuator arranged between the first directional coupler and the first mixing stage; and a second attenuator arranged between the second directional coupler and the second mixing stage.

[0038] The first attenuator and / or the second attenuator may be a variable attenuator.

[0039] In an embodiment, the second attenuator is configured to adjust its attenuation factor depending on the measured signal level of the down-converted measurement signal.

[0040] For example, the processing unit may be configured to control the second variable attenuator to adjust its attenuation factor.

[0041] In an embodiment, the test and / or measurement system is configured to apply the DC bias signal to the DC input port of the biaser if a calibration standard other than a short or open calibration standard is attached to the device port.

[0042] This achieves the advantage that a DC bias signal can be applied to a suitable wideband calibration standard, while a "standard" calibration without a DC bias signal can be performed using a calibration standard that is not suitable for applying such a bias signal (e.g. a calibration standard that cannot dissipate significant power).

[0043] In one embodiment, the test and / or measurement system further comprises: at least one additional device port; at least one additional signal path, the additional signal path being arranged to electrically connect the RF signal source to the additional device port; and at least one additional measurement unit, the additional measurement unit being coupled to the additional signal path, wherein the additional measurement unit is adapted to measure the RF excitation signal transmitted to the additional device port via the additional signal path and an additional measurement signal received at the additional device port.

[0044] The further measurement unit may be configured to generate further measurement values ​​representing respective measurement results (of the RF excitation signal and the further measurement signal), and the processing unit may be configured to receive the further measurement values ​​from the measurement unit.

[0045] The RF excitation signal transmitted via the additional signal path may be the same as or different from the RF excitation signal transmitted via the signal path.

[0046] For example, a test and / or measurement system may include 2, 4, 6, 8, 10, or more device ports.

[0047] In one embodiment, the DUT is connectable to the device port and the further device port; wherein, in the measurement mode, the test and / or measurement system is configured to calculate scattering parameters of the DUT connected to the device port and the further device port, wherein the scattering parameters are corrected by a set of error terms, the set of error terms being selected based on a signal level of a DC signal applied to the DUT.

[0048] In one embodiment, one of the calibration standards is a straight-through calibration standard; wherein, in the calibration mode, the straight-through calibration standard is connected to the device port and the other device port so that a straight-through connection is established between the device port and the other device port; wherein the processing unit is configured to calculate an error term for the straight-through connection.

[0049] In one embodiment, the test and / or measurement system further comprises: at least one additional bias device coupled to the additional signal path; wherein the additional bias device comprises a DC input port configured to receive a DC bias signal, wherein the additional bias device is arranged to couple the received DC bias signal into the additional signal path.

[0050] The DC bias signal received at the DC input port of the further biaser may be the same as or different from the DC bias signal received at the DC input port of the biaser.

[0051] According to a second aspect, the invention relates to a method for calibrating a test and / or measurement system, in particular a vector network analyzer. The method comprises: alternately connecting at least four different calibration standards to a device port of the test and / or measurement system; during the connection of each of the calibration standards: generating an RF excitation signal, forwarding the RF excitation signal to the device port via a signal path of the test and / or measurement system, measuring the RF excitation signal transmitted to the device port via the signal path and a measurement signal received at the device port, generating measurement values ​​representing respective measurement results of the RF excitation signal and the measurement signal, and receiving the measurement values ​​at a processing unit of the test and / or measurement system; wherein during the connection of at least one of the calibration standards, but not during the connection of all of the calibration standards, a DC bias signal is coupled into the signal path.

[0052] The method may be performed with the test and / or measurement system set in a calibration mode.

[0053] In one embodiment, the method further comprises calculating an error term for the test and / or measurement system based on the measurements received for each connected calibration standard.

[0054] The above description regarding the testing and / or measuring system according to the first aspect of the invention is correspondingly valid for the method according to the second aspect of the invention.

[0055] The method according to the second aspect of the invention may be performed using a test and / or measurement system (eg a VNA) according to the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The present invention will be explained below with reference to the accompanying drawings.

[0057] Figure 1 A schematic diagram of a testing and / or measuring system according to an embodiment is shown;

[0058] Figure 2A schematic diagram showing a testing and / or measuring system according to an embodiment; and

[0059] Figure 3 A flow chart of a method for calibrating a test and / or measurement system is shown. DETAILED DESCRIPTION

[0060] Figure 1 A schematic diagram of a testing and / or measuring system 10 is shown in accordance with an embodiment.

[0061] The test and / or measurement system 10 comprises an RF signal source 11 configured to generate an RF excitation signal, a device port 13 , and a signal path 12 arranged to electrically connect the RF signal source 11 to the device port 13 .

[0062] The test and / or measurement system 10 further comprises a measurement unit 15 coupled to the signal path 12, wherein the measurement unit 15 is adapted to measure the RF excitation signal transmitted to the device port 13 via the signal path 12 and the measurement signal received at the device port 13, wherein the measurement unit 15 is configured to generate a measurement value representing a corresponding measurement result. The test and / or measurement system 10 further comprises: a processing unit ( Figure 1 ), which is configured to receive a measurement value; and at least one bias device 14 coupled to the signal path 12, wherein the bias device 14 includes a DC input port configured to receive a DC bias signal, wherein the bias device 14 is arranged to couple the received DC bias signal into the signal path 12.

[0063] The test and / or measurement system 10 may be operated in a calibration mode, during which at least four different calibration standards 40a-40d are alternately connected to the device port 13; wherein, for each of the connected calibration standards 40a-40d, the measurement unit 15 is configured to measure an RF excitation signal and a measurement signal; and wherein the test and / or measurement system 10 is configured to couple a DC bias signal into the signal path 12 via the bias device 14 during connection of at least one of the calibration standards 40a-40d, but not during connection of all of the calibration standards 40a-40d.

[0064] The test and / or measurement system 10 may be a vector network analyzer.

[0065] The measurement unit 15 may be configured to measure an RF excitation signal transmitted (or traveling) from the RF signal source 11 toward the device port 13 , and to measure a measurement signal transmitted (or traveling) from the device port 13 via the signal path 12 in the direction of the RF signal source 11 .

[0066] The DC bias signal may be a DC voltage and / or current signal.

[0067] The radio frequency (RF) excitation signal may be an AC and / or continuous wave (CW) signal in the radio frequency or microwave range.

[0068] The measurement signal may be an RF signal or an RF signal superimposed by a DC voltage and / or current signal.

[0069] The measurement signal measured in the calibration mode may be received in response to the RF excitation signal and / or the DC bias signal.For example, the measurement signal may include reflections of the RF excitation signal and / or the DC bias signal from a connected calibration standard.

[0070] The signal path 12 may include wires connecting the RF signal source 11 with the device port 13. The signal path 12 may be a measurement path.

[0071] The device port 13 may be a test port and / or an RF port of the test and / or measurement system 10. The device port 13 may be configured to connect to a DUT and / or different calibration standards.

[0072] Preferably, the coupling of the measuring unit to the signal path is not a resistive coupling. This can prevent additional (unwanted) power from being distributed into the measuring unit.

[0073] The measuring unit may be configured to measure the RF excitation signal and the measurement signal independently of each other.

[0074] For example, the measuring unit 15 may be configured to measure the amplitude and / or phase of the RF excitation signal and the measurement signal. Therefore, the measuring unit 15 may include an amplitude and / or phase sensor configured to measure the amplitude and / or phase of the RF excitation signal and the measurement signal. In addition, the measuring unit 15 may be configured to measure the relative phase difference between the RF excitation signal and the measurement signal.

[0075] The processing unit may be configured to receive the measurement values ​​in digital form from the measuring unit.

[0076] The measurement value may represent or include a measurement result of the measurement unit, ie, the measured RF excitation signal and the measurement signal.

[0077] In the calibration mode, the processing unit may be configured to calculate error terms of the test and / or measurement system 10 based on the results of the calibration measurements, for example based on the measured values ​​received from the measurement unit 15 for each connected calibration standard.

[0078] The error terms may include correction values ​​that may be mathematically applied to the measurements of the test and / or measurement system 10 to correct for the measurement errors.

[0079] For example, the processing unit may calculate the error term by comparing the (known) characteristic of the calibration standard with the measured quantity (e.g., the amplitude and / or phase of the RF excitation signal and the measurement signal, and / or the phase difference between these signals) and applying an error model. For example, the error model is a mathematical model that receives the characteristic of the calibration standard, the measured quantity and / or the DC signal level(s) as input parameters and calculates the error term using said parameters.

[0080] The error terms may be stored in a memory of the test and / or measurement system 10 .

[0081] The test and / or measurement system 10, in particular the RF signal source 11, may be configured to sweep the RF excitation signal within a determined frequency and / or power range. The sweep may be performed during connection of at least one of the calibration standards, preferably during connection of all calibration standards. The processing unit may be configured to receive measurement results (i.e., respective measurement values) for respective calibration standards at a plurality of frequencies and / or power levels of the RF excitation signal within the frequency and / or power range.

[0082] The at least four different calibration standards 40a-40d can be independently operated calibration standards, or at least some or all of these calibration standards 40a-40d can be combined in a common housing (e.g., a calibration unit) having one connection port. In the case where several calibration standards are combined in a common calibration unit, a data connection to the calibration unit can be used to select the corresponding calibration standard.

[0083] The calibration standards 40a-40d may include any of the following calibration standards: open, short, match, and thru.

[0084] For example, at least one calibration standard 40b is configured to calibrate using a low power, high bandwidth signal (e.g., sweeping the RF excitation signal over a wide frequency range without applying a DC bias signal, I=0). At least one additional calibration standard 40d is configured to calibrate using a high power, low bandwidth signal. For example, when additional calibration standard 40d is connected, a DC bias signal (I=I n ) and corresponding calibration measurements are performed without a DC bias signal (I=0) being coupled into the signal path.

[0085] Therefore, the additional calibration standard(s) 40d that may be added to the calibration routine may focus on higher power handling capabilities with low bandwidth. For example, these standards utilize an applied DC current signal I n By comparing I = 0 and I = I nThe error terms of , the resulting set of error terms can be corrected within the lower bandwidth of these (high power) calibration standards 40d.

[0086] For example, the test and / or measurement system 10 may be configured to apply a DC bias signal to the DC input port of the biaser (and thus to the signal path 12 ) if a calibration standard other than a short and an open is attached to the device port.

[0087] The test and / or measurement system 10 may include a DC signal generator 16 configured to generate a DC bias signal having a specific (determined) voltage and / or current level.

[0088] The DC signal generator 16 may be disposed within a housing of the test and / or measurement system and may be connected to a DC input port of the bias set 14 .

[0089] Alternatively, the DC signal generator 16 can be an external device (i.e., outside the housing of the test and / or measurement system 10), wherein the test and / or measurement system 10 (e.g., a processing unit) can be configured to control the DC signal generator 16 so that the DC signal generator 16 generates and outputs a DC bias signal having a specific voltage and / or current level. For example, the DC signal generator 16 can be controlled by the test and / or measurement system 10 via a USB or other suitable data connection component. The DC bias signal generated by the DC signal generator 16 can be fed to the components within the housing of the test and / or measurement system 10 via a coaxial cable, in particular to the DC input port of the bias 14.

[0090] The test and / or measurement system 10, in particular the DC signal generator 16, may be configured to vary the level of the DC bias signal.The processing unit may be configured to receive measurements of at least two different power levels of the DC signal for respective calibration standards 40a-40d suitable for DC bias.

[0091] Thus, for example, the DC bias signal is held constant during a frequency sweep of the RF excitation signal. After the frequency sweep, the power level of the DC bias signal may be changed. Then, another frequency sweep may be performed.

[0092] The processing unit may be configured to calculate a first set of error terms for a DC bias signal of a first level and to calculate at least a second set of error terms for a DC bias signal of at least one second level different from the first level.

[0093] The bias device 14 may include: a DC input port (e.g., a low frequency port) for receiving a DC bias signal, an RF input port (e.g., a high frequency port) for receiving an RF excitation signal, and a third port connected to the signal path. The bias device 14 may be a duplexer type that multiplexes the RF input port and the DC input port onto the third port.

[0094] For example, the biaser 14 further includes a capacitor connected to the RF input port and an inductor connected to the DC input port. The capacitor may be configured to transmit the RF excitation signal and block the DC bias signal, and the inductor may be configured to transmit the DC bias signal and block the RF excitation signal.

[0095] The bias trolley 14 may be arranged within the signal path 12. For example, the bias trolley 14 is arranged between the RF signal source 11 and the measuring unit 15. Alternatively, the bias trolley 14 may be arranged between the measuring unit 15 and the device port 13.

[0096] like Figure 1 As shown, the measurement unit 15 may include: a first directional coupler 18a configured to receive at least a portion of the RF excitation signal from the signal path 12, and a second directional coupler 18b configured to receive at least a portion of the measurement signal from the signal path 12. In addition, the measurement unit 15 may include: a first mixing stage 20a configured to down-convert the RF excitation signal, and a second mixing stage 20b configured to down-convert the measurement signal. Therefore, each mixing stage 20a, 20b may include a mixer that may receive a portion of the RF excitation signal or the measurement signal and a LO (local oscillator) signal.

[0097] The directional couplers 18a, 18b may be directly or indirectly connected to the respective mixing stages 20a, 20b and may be configured to forward the received RF excitation signal or the measurement signal to the respective mixing stages 20a, 20b.

[0098] The mixing stages 20a, 20b may be configured to down-convert the RF excitation signal and the measurement signal to an intermediate frequency (IF), for example for further processing.

[0099] The measuring unit 15 may further comprise a digitizing unit 17, which may be configured to simultaneously measure the down-converted portion of the excitation signal and the down-converted portion of the measurement signal. For example, the digitizing unit 17 may comprise an analog-to-digital converter (ADC).

[0100] Therefore, the measuring unit 15 may be configured to forward the digitized signal to the processing unit.

[0101] The first directional coupler 18a can be configured to decouple the DC bias signal from the first mixing stage 20a, and the second directional coupler 18b can be configured to decouple the DC bias signal (or its reflection) from the second mixing stage 20b. In other words, the directional couplers 18a, 18b can be configured to forward only the RF excitation signal and / or only the RF signal component of the measurement signal to the mixing stages 20a, 20b.

[0102] The test and / or measurement system 10, in particular the measuring unit 15, may include a first attenuator 19a arranged between the first directional coupler 18a and the first mixing stage 20a and a second attenuator 19b arranged between the second directional coupler 18b and the second mixing stage 20b.

[0103] The first attenuator 19a and / or the second attenuator 19b may be variable attenuators. By means of these attenuators 19a, 19b, the dynamic range of the measuring unit 15 may be increased, for example when measuring a DUT.

[0104] In particular, the second attenuator 19b arranged in the path for receiving the measurement signal is a variable attenuator. For example, if the DUT is an amplifier, the amplified signal received from the DUT is fed into the device port 13 and decoupled by the second directional coupler 18b. By changing the attenuation level of the attenuator 19b, the dynamic range can be extended (for example, to measure the amplified response signal from the amplifier).

[0105] For example, the second attenuator 19b may be configured to adjust its attenuation factor according to the measured signal level of the down-converted measurement signal. In an example, the second attenuator may be controlled by the processing unit to adjust its attenuation factor.

[0106] As a result, the attenuation factor of the first attenuator 19 a and / or the second attenuator 19 b can be increased until the digitization unit, for example the analog-to-digital converter, reaches its upper limit value.

[0107] Figure 2 A schematic diagram of a test and / or measurement system 10 according to an embodiment is shown. Thereby, a DUT 50 is connected to a device port 13 of the test and / or measurement system 10 .

[0108] The test and / or measurement system 10 may operate in a measurement mode (or normal operation mode), during which the system 10 , and in particular the processing unit 21 , is configured to calculate scattering parameters (S-parameters) of the DUT 50 .

[0109] The DUT 50 may be an RF device under test. For example, the DUT 50 may be an active device (eg, a communication device) or a passive device (eg, a cable or a filter).

[0110] The processing unit may be a (micro)processor, an FPGA or an ASIC.

[0111] like Figure 2 As shown, the test and / or measurement system 10 may include at least one further device port 23 and at least one further signal path 22 , wherein the RF signal source 11 may be connected to the further device port 23 via the second signal path 22 .

[0112] Applying a DC signal (eg, a DC voltage) to the device port (so-called biasing) is often necessary for measuring the DUT.

[0113] The DC signal applied to the DUT may be generated by the same DC signal generator 16 that generates the DC bias signal during calibration. The DC signal may be a DC measurement signal. The DC signal may be a voltage and / or current signal.

[0114] The test and / or measurement system 10 may include at least one further measurement unit 25 coupled to the further measurement path 22. The further measurement unit 25 may be configured to measure the RF excitation signal transmitted from the RF signal source 11 to the further device port 23, preferably independently of the measurement signal received at the further device port 23 (i.e. transmitted from the further device port 23 towards the RF signal source 11). The further measurement unit 25 may output a corresponding further measurement value based on the measurement, for example to the processing unit 21.

[0115] For example, the RF signal source 11 may be connected to either the device port 13 or the other device port 23 , but not to both device ports 13 , 23 at the same time.

[0116] The test and / or measurement system 10 may further include at least one further biaser 24 coupled to the further signal path 22. For example, the second biaser 24 may be arranged in the further signal path 22. In the calibration mode, the further biaser 24 may be configured to receive the DC bias signal (or the further DC bias signal) and couple the DC signal into the further signal path 22.

[0117] For example, Figure 1 One of the calibration standards 40a-40d shown in FIG. 4 may be a through-calibration standard, which in calibration mode may be connected to the device port 13 and the further device port 23. In this way, a through connection may be established between the device port 13 and the further device port 23. In this case, the processing unit may be configured to calculate an error term for the through connection.

[0118] When the system 10 is operating in the measurement mode, as Figure 2As shown, the DUT 50 can be connected to the device port 13 and the additional device port 23. The test and / or measurement system 10 can be configured to calculate the S-parameters of the DUT 50 so connected, wherein the S-parameters (or the measured values ​​used to calculate the S-parameters) can be corrected by a set of error terms (determined during the calibration mode), and this set of error terms can be selected based on the level of the DC signal applied to the DUT in the measurement mode. For example, if a set of error terms is calculated when a DC bias signal is applied that deviates less than a threshold relative to the DC signal applied to the DUT 50, this set of error terms can be selected.

[0119] Figure 3 A flow chart of a method 30 for calibrating a test and / or measurement system 10 is shown. For example, the method 30 may be used to calibrate a Figure 1 or Figure 2 A test and / or measurement system 10 is shown.

[0120] The method 30 comprises the steps of: alternately connecting 31 at least four different calibration standards to a device port of a test and / or measurement system; and during the connection of each calibration standard: generating 32 an RF excitation signal, forwarding 33 the RF excitation signal to the device port via a signal path of the test and / or measurement system, measuring 35 the RF excitation signal transmitted to the device port via the signal path and the measurement signal received at the device port, generating 36 measurement values ​​representing respective measurement results of the RF excitation signal and the measurement signal, and receiving 37 the measurement values ​​at a processing unit of the test and / or measurement system; wherein, during the connection of at least one of the calibration standards, but not during the connection of all calibration standards, a DC bias signal is coupled 34 into the signal path.

[0121] For example, the method 30 may be performed when the test and / or measurement system 10 is placed into a calibration mode.

[0122] The method 30 may also include the step of calculating an error term for the test and / or measurement system 10 based on the measurements received for each connected calibration standard 40a - 40d .

[0123] All features mentioned above or shown in the drawings can be combined with one another in any advantageous manner within the scope of the invention.

Claims

1. A test and / or measurement system (10), in particular a vector network analyzer, comprising: An RF signal source (11), the RF signal source being configured to generate an RF excitation signal; Device Port (13); a signal path (12) arranged to electrically connect the RF signal source (11) to the device port (13); a measuring unit (15) coupled to the signal path (12), wherein the measuring unit (15) is adapted to measure the RF excitation signal transmitted to the device port (13) via the signal path (12) and a measurement signal received at the device port (13), wherein the measuring unit (15) is configured to generate measurement values ​​representing respective measurement results; a processing unit (21) configured to receive the measurement value; and at least one biaser (14) coupled to the signal path (12), wherein the biaser (14) comprises a DC input port configured to receive a DC bias signal, wherein the biaser (14) is arranged to couple the received DC bias signal into the signal path (12); wherein the test and / or measurement system (10) is capable of operating in a calibration mode during which at least four different calibration standards (40a-40d) are alternately connected to the device port (13); wherein, for each connected calibration standard (40a-40d), the measuring unit (15) is configured to measure the RF excitation signal and the measurement signal; and The test and / or measurement system (10) is configured to couple the DC bias signal into the signal path (12) during connection of at least one of the calibration standards (40a-40d), but not during connection of all of the calibration standards (40a-40d).

2. The testing and / or measuring system (10) as claimed in claim 1, in, In the calibration mode, the processing unit (21) is configured to calculate an error term for the test and / or measurement system (10) based on the measurement values ​​received for each connected calibration standard (40a-40d).

3. The testing and / or measuring system (10) as claimed in claim 1 or 2, in, The RF signal source (11) is configured to sweep the RF excitation signal over a predetermined frequency range and / or a predetermined power range; The processing unit (21) is configured to receive the measured values ​​for at least one, preferably all, of the calibration standards (40a-40d) for a plurality of frequencies and / or power levels within a corresponding range.

4. The testing and / or measuring system (10) as claimed in any one of claims 1 to 3, in, The test and / or measurement system (10) is configured to change the level of the DC bias signal; The processing unit (21) is configured to receive the measured value for at least one of the calibration standards (40a-40d) for a plurality of DC bias signal levels.

5. The testing and / or measuring system (10) as claimed in claims 2 and 4, in, The processing unit (21) is configured to calculate a first set of error terms for a DC bias signal of a first level and to calculate at least a second set of error terms for a DC bias signal of at least a second level different from the first level.

6. The testing and / or measuring system (10) as claimed in claim 5, in, A device under test DUT (50) can be connected to the device port (13); The test and / or measurement system (10) is capable of operating in a measurement mode, during which the test and / or measurement system (10) is configured to calculate scattering parameters of the DUT (50), wherein the scattering parameters are corrected by a set of error terms selected based on the level of a DC signal applied to the DUT (50).

7. The testing and / or measuring system (10) according to any one of claims 1 to 6, in, The bias device (14) is arranged between the RF signal source (11) and the measuring unit (15), or wherein the bias device (14) is arranged between the measuring unit (15) and the device port (13).

8. The test and / or measurement system (10) according to any one of claims 1 to 7, further comprising: a DC signal generator (16) configured to generate the DC bias signal having a determined voltage and / or current level; The DC signal generator (16) is arranged in a housing of the test and / or measurement system (10) and is connected to a DC input port of the bias device (14).

9. The testing and / or measuring system (10) as claimed in any one of claims 1 to 7, in, The DC input port of the bias device (14) is connectable to an external DC signal generator (16) arranged outside the housing of the test and / or measurement system (10); The test and / or measurement system (10) is configured to control the external DC signal generator (16) to generate the DC bias signal with a determined voltage and / or current level.

10. The testing and / or measuring system (10) according to any one of claims 1 to 9, wherein: The measuring unit (15) comprises: - a first directional coupler (18a) configured to forward at least a portion of the RF excitation signal from the signal path (12), - a second directional coupler (18b) configured to forward at least a portion of the measurement signal from the signal path (12), - a first mixing stage (20a) configured to down-convert said portion of said RF excitation signal, and - a second mixing stage (20b) configured to down-convert said portion of said measurement signal.

11. The testing and / or measuring system (10) as claimed in claim 10, in, The measuring unit (15) further comprises a digitizing unit (17) configured to simultaneously measure the down-converted portion of the RF excitation signal and the down-converted portion of the measurement signal.

12. The testing and / or measuring system (10) according to claim 10 or 11, in, The first directional coupler (18a) is configured to decouple the DC bias signal from the first mixing stage (20a); as well as Wherein the second directional coupler (18b) is configured to decouple the DC bias signal from the second mixing stage (20b).

13. The test and / or measurement system (10) according to any one of claims 10 to 12, further comprising: a first attenuator (19a), the first attenuator being arranged between the first directional coupler and the first mixing stage; as well as A second attenuator (19b) is arranged between the second directional coupler and the second mixing stage.

14. The testing and / or measuring system (10) as claimed in claim 13, in, The second attenuator (19b) is configured to adjust its attenuation factor according to the measured signal level of the down-converted measurement signal.

15. The testing and / or measuring system (10) as claimed in any one of claims 1 to 14, in, The test and / or measurement system (10) is configured to apply the DC bias signal to the DC input port of the biaser (14) if a calibration standard (40a-40d) other than a short circuit or open circuit calibration standard is attached to the device port (13).

16. The test and / or measurement system (10) according to any one of claims 1 to 15, further comprising: at least one additional device port (23); at least one further signal path (22) arranged to electrically connect the RF signal source (11) to the further device port (23); as well as at least one further measurement unit (25) coupled to the further signal path (22), wherein the further measurement unit (25) is adapted to measure the RF excitation signal transmitted to the further device port (23) via the further signal path (22) and a further measurement signal received at the further device port (23).

17. The testing and / or measuring system (10) according to claims 6 and 16, in, The DUT (50) is connectable to the device port (13) and the further device port (23); Wherein, in the measurement mode, the test and / or measurement system (10) is configured to calculate scattering parameters of the DUT (50) connected to the device port (13) and the further device port (23), wherein the scattering parameters are corrected by a set of error terms, the set of error terms being selected based on the signal level of the DC signal applied to the DUT (50).

18. The testing and / or measuring system (10) according to claim 16 or 17, in, One of the calibration standards (40a-40d) is a through-calibration standard; wherein, in the calibration mode, the through-type calibration standard is connected to the device port (13) and the further device port (23), so that a through-type connection is established between the device port (13) and the further device port (23); The processing unit (21) is configured to calculate an error term for the through connection.

19. The test and / or measurement system (10) according to any one of claims 16 to 18, further comprising: At least one further biaser (24) coupled to the further signal path (22); wherein the further biaser (24) comprises a DC input port configured to receive a DC bias signal, wherein the further biaser (24) is arranged to couple the received DC bias signal into the further signal path (22).

20. A method (30) for calibrating a test and / or measurement system (10), in particular a vector network analyzer, comprising: Alternately connecting (31) at least four different calibration standards (40a-40d) to a device port (13) of the test and / or measurement system; During connection of each of said calibration standards (40a-40d): - generating (32) an RF excitation signal, - forwarding (33) the RF excitation signal to the device port (13) via the signal path (12) of the test and / or measurement system, - measuring (35) the RF excitation signal transmitted via the signal path (12) to the device port (13) and the measurement signal received at the device port (13), - generating (36) measurement values ​​representing respective measurements of said RF excitation signal and said measurement signal, and - receiving (37) the measured values ​​at a processing unit (21) of the testing and / or measuring system; wherein a DC bias signal is coupled (34) into the signal path (12) during connection of at least one of the calibration standards (40a-40d), but not during connection of all of the calibration standards (40a-40d).

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