WO2010069349A1

WO2010069349A1 - Apparatus for determining a compensation parameter for compensating a signal level change of a test signal

Info

Publication number: WO2010069349A1
Application number: PCT/EP2008/010854
Authority: WO
Inventors: Bernd Laquai
Original assignee: Verigy (Singapore) Pte Ltd.
Priority date: 2008-12-18
Filing date: 2008-12-18
Publication date: 2010-06-24
Also published as: TW201030360A; TWI445990B

Abstract

An apparatus (190) for determining a compensation parameter for compensating a signal level change of a test signal, wherein the signal level change is caused by a propagation of the test signal along a signal path (102), comprises a test signal generator (110) and a test signal analyzer (120). The test signal generator is configured to provide the test signal and couple it into the signal path. The test signal analyzer is configured to analyze a reflection of the test signal and configured to determine the compensation parameter based on the analysis of the reflected test signal. The analysis of the reflected test signal is based on determining a signal level of the reflected test signal.

Description

Apparatus for determining a compensation parameter for compensating a signal level change of a test signal

Description

Embodiments according to the invention relate to an apparatus and a method for determining a compensation parameter for compensating a signal level change of a test signal.

For example, compensating a signal level change is of high interest for automated test equipment.

Automated test equipment (ATE) typically uses various sophisticated calibration techniques to ensure that signals that stimulate a device under test (DUT) are generated as accurate as possible with respect to the signal levels and the signal timing. Similar calibration techniques ensure that signals that are generated from a DUT as a response to the stimulus are analyzed as accurate as possible with respect to signal levels and timing. However, it is quite common that these calibration techniques refer to the electrical connectors of the testhead (e.g. a pogo interface) . This also means that the specification of the ATE system accuracy refers to the testhead connectors.

The user of an ATE however, needs a fixture to establish the mechanical and electrical connection between one or more devices under test and the testhead. Such a fixture consists of cables, printed circuit boards (PCBs) and device sockets that form the fixture signal path on which the stimulus and receive signals propagate to and from the DUT. In particular at higher data rates and when many DUTs are tested in parallel, the signal paths on the fixture cause substantial inaccuracies of signal levels and timing. The consequence is that the ATE system accuracy is significantly degraded with respect to the electrical connection to the DUT (for example the DUT socket) .

In order to also take into account the impact of the fixture signal path on the ATE accuracy, some ATE provides at least a compensation of the impact of the fixture on the timing accuracy. Typically, a fixture delay calibration can be executed by the user that measures the additional fixture signal path delay. A time-domain-reflectometry (TDR) -based measurement technique is used to determine the signal path delay (FXDL-CaI, fixture delay calibration) . In such a case, the delay compensation circuitry contained in the ATE is implemented flexible enough to also compensate the measured propagation delay of the fixture signal path.

At even higher speeds (data rates > 1 Gbps) and/or higher parallelism (number of DUTs > 64), the fixture signal path becomes electrically long and thin. In addition, the cost pressure may limit the quality of the material and of the fixture manufacturing process having an additional negative impact on the signal integrity. This may result in an unacceptable loss of accuracy on the signal levels. As an example, the skin effect and the dielectric loss may cause a so-called signal droop.

This means that a signal transition reaches only a fraction of the programmed voltage level with the fast rising portion of the transition. A slow rising portion of the transition follows and the final target voltage is reached only gradually.

Fig. 2 shows a voltage-time diagram 200 of a fixture signal in presence of a droop. The continuous line 210 shows a signal at an output of a fixture signal path and the dashed line 220 shows a signal at an input of a fixture signal path. In such a case, a signal with high transition rate will never reach the programmed voltage level causing a vertical data eye closure. Depending on the length of the signal path, the level attenuation caused by the fixture is different for each signal path.

Another fixture effect that may also cause a degradation of signal level accuracy are impedance mismatches in the signal path, for example, caused by inevitable manufacturing variations of PCBs. Further sources of level inaccuracy are reflections from signal vias in the PCB or other discontinuities such as lumped capacitive, inductive or resistive elements that are connected to the fixture signal path including the DUT loading effect itself.

Summary of the invention

It is the object of the present invention to provide an apparatus for determining a compensation parameter for compensating a signal level change of a test signal caused by a propagation of the test signal along a signal path.

This object is solved by an apparatus according to claim 1 and a method according to claim 10.

An embodiment of the invention provides an apparatus for determining a compensation parameter for compensating a signal level change of a test signal. The signal level change is caused by a propagation of the test signal along a signal path. The apparatus comprises a test signal generator and a test signal analyzer.

The test signal generator is configured to provide the test signal and couple it into the signal path.

The test signal analyzer is configured to analyze a reflection of the test signal and configured to determine the compensation parameter based on the analysis of the reflected test signal. The analysis of the reflected test signal is based on determining a signal level of the reflected test signal. Embodiments according to the present invention are based on the central ideal that a signal level change of the test signal is linked to a signal level change of the reflected test signal. Therefore, a compensation parameter for compensating the signal level change of the test signal may be determined based on a signal level of the reflected test signal .

Some embodiments according to the invention relate to a test system comprising an apparatus for determining a compensation parameter and a test signal adapting means. The test signal adapting means is configured to adapt the test signal based on the compensation parameter. The test signal adapting means may be a part of the test signal generator.

In this way, for example, a signal droop may be compensated and/or the accuracy of the signal level of a test system may be improved.

Brief description of the drawings

Embodiments according to the invention will be detailed subsequently referring to the appended drawings, in which:

Fig. 1 is a block diagram of an apparatus for determining a compensation parameter for compensating a signal level change of a test signal;

Fig. 2 is a schematic voltage-time diagram of a signal in presence of a droop;

Fig. 3a, 3b are schematic illustrations of an apparatus for determining a compensation parameter for compensating a signal level change of a test signal; Fig. 4 is a schematic voltage-time diagram of a reflected test signal;

Fig. 5 is a voltage-time diagram of a test signal transmitted through the signal path;

Fig. 6 is a voltage-time diagram of a reflected test signal;

Fig. 7 is a close-up of the voltage-time diagram shown in Fig. 6;

Fig. 8 is a voltage-time diagram of a reflected test signal;

Fig. 9 is a block diagram of an apparatus for determining a compensation parameter for compensating a signal level change of a test signal; and

Fig. 10 is a flowchart of a method for determining a compensation parameter.

Detailed description of embodiments

Fig. 1 shows a block diagram of an apparatus 100 for determining a compensation parameter for compensating a signal level change of a test signal according to an embodiment of the invention. The signal level change is caused by a propagation of the test signal along a signal path 102. The apparatus 100 comprises a test signal generator 110 and a test signal analyzer 120.

The test signal generator 110 is connected to the signal path 102 and configured to provide the test signal and couple it into the signal path 102. The test signal analyzer 120 is also connected to the signal path 102 and configured to analyze a reflection of the test signal and configured to determine the compensation parameter based on the analysis of the reference signal. The analysis of the reference signal is based on determining a signal level of the reflected test signal.

The dashed line indicates the signal path 102.

The idea is that a time domain reflectometry (TDR) like measurement may not only reveal signal path delay information but may also reveal, for example, signal attenuation information that is inherent to the signal path 102.

For example, in the case of a signal droop, the reflected test signal caused by an incident step wave (the test signal) as used for a regular TDR measurement shows a similar signal droop as the signal at the signal path output. The Signal path output is the end of the signal path 102 not connected to the test signal generator 110 and the test signal analyzer 120. The difference is that the signal droop of the reflected test signal results from the step wave traveling forth and back the measured signal path. Nevertheless, the reference signal carries information on the droop properties of the signal path 102 and therefore the compensation parameter may be determined based on the analysis of the reflected test signal.

Trace impedance mismatches and other discontinuities in the signal path 102 often result in level attenuation or level overshoot. Also in these cases a TDR-based level measurement can be used to determine a compensation parameter, because the reflected test signal may also reveal the respective kind of level information. Many of these cases cause effects that behave similar to the droop effect. The test signal generator 110 may be a common signal generator for generating signals with different waveforms. The test signal may be a step wave, a triangle signal, a sine or cosine signal or a signal with another waveform.

The test signal analyzer 120 may be a common signal analyzer with sufficient time resolution. For example, the test signal analyzer 120 detects an arrival of a reflected test signal at an arrival time. At a specific time after the arrival time, the test signal analyzer 120 determines a signal level of the reflected test signal. The test signal analyzer 120 may be configured to determine a plurality of signal levels of the reflected test signal at different times after the arrival time.

Alternatively, the test signal analyzer 120 may determine a plurality of signal levels of the reflected test signal continuously at regular time intervals.

The signal level change of the test signal may be caused, for example, by a signal droop, an impedance mismatch or other discontinuities in the signal path 102.

Fig. 3a and 3b show a schematic illustration of an apparatus 300 for determining a compensation parameter for compensating a signal level change of a test signal according to an embodiment of the invention.

Fig. 3a shows the apparatus 300 with a signal path 102, wherein the end of the signal path 102 not connected to the test signal generator 110 and the test signal analyzer 120 is open. Further, schematic illustrations of the incident step wave 310 (the test signal) , the signal droop 320 at the open end of the signal path 102, and the reflected wave 330 (reflected test signal) with the droop information are shown. Fig. 3b shows the apparatus 300 with a signal path 102, wherein the end of the signal path 102 not connected with the test signal generator 110 and the test signal analyzer 120 is shorted. Furthermore, a schematic illustration of the incident step wave 310 (the test signal) and the reflected wave 330 (the reflected test signal) with droop information are shown.

Depending on whether the signal path 102 comprises an open or a shorted end, the reflected test signal comprises a different waveform, but carries in both cases a droop information.

The example shown in Fig. 3a and 3b may be a TDR measurement with open end and shorted end carrying droop information.

Fig. 4 shows a schematic voltage-time diagram 400 of a reflected test signal 402.

In this example, the signal level is measured at three different times 412, 414, 416 after the arrival time 410 of the reflection of the test signal. The measured signal levels, for example, correspond to extracted attenuation values 422, 424, 426. The attenuation values 422, 424, 426 (al, a2, a3) indicate the percentage of the signal level reached by the reflected test signal at the associated time 412, 414, 416 with respect to the original test signal. The signal level of the original test signal is indicated by the dashed line 420. Also tangents 442, 444, 446 of the waveform of the reference signal may be determined to obtain time constants 432, 434, 436 (τl, τ2, τ3) that approximate the droop.

A compensation parameter may be the measured signal level at a specific time, an extracted attenuation value at a specific time, a time constant at a specific time or another value based on the measured signal level at a specific time.

Further compensation parameters may be determined by linear interpolation between two known compensation parameters of the plurality of compensation parameters. Also another algorithm for fitting further compensation parameters between two known compensation parameters may be used. For example, the known compensation parameters may be fitted by a polynomial.

The shown example may be a level measurement on the reflected TDR waveform.

Fig. 5 shows a voltage-time diagram 500 of a test signal transmitted through a signal path. The diagram 500 shows the transmitted test signal 510, wherein the dash-dotted line 520 shows the original test signal, which is also the desired transmitted test signal. The transmitted test signal 510 is measured at the end of the signal path not connected to the test signal generator and the test signal analyzer.

In this example, the diagram 500 has an origin 530 with an offset of 100 mV, a vertical scale of 50 mV/div, a horizontal scale of 200 ps/div, a delay of 44.6791 ns and a trigger level of 200 mV.

In this case, a droop on a 40 cm long high-speed cable (signal path) with 1 mm diameter, for example, for a very high-density memory fixture with a level loss of more than 10 % in the first 100 ps is shown. The example may be a time domain transmission (TDT) scope measurement from input to output.

Fittingly, Fig. 6 shows a voltage-time diagram 600 of a reflected test signal. The reflected test signal 610 corresponds to the transmitted test signal 510 of Fig. 5. In this example, the diagram 600 has an origin 530 with an offset of 200 mV, a vertical scale of 100 mV/div, a horizontal scale of 1000 ns/div, a delay of 46.1511 ns and a trigger level of 200 mV.

The time domain reflectometry (TDR) measurement with a scope into the high-speed cable (signal path) , for example, shows the same droop information on the reflected wave (the reflected test signal) from the shorted end. In other words, the droop information of the droop of a transmitted test signal may be seen and/or determined based on the reflected test signal.

Fig. 7 shows a close-up 700 of the voltage-time diagram shown in Fig. 6. It is a close-up 700 into the transition reflected from the shorted end. The small visible distortions 710 result from the SMA (sub miniature version A) connector attached to the cable end (the end of the signal path) .

In this example, the close-up 700 has an origin 530 with an offset of 100 mV, a vertical scale of 500 mV/div, a horizontal time scale of 200 ps/div, a delay of 46.4911 ns and a trigger level of 200 mV.

Some embodiments according to the invention relate to a test system with an apparatus for determining a compensation parameter for compensating a signal level change of a test signal. The test system may be an automated test equipment (ATE) .

Fig. 8 shows a voltage-time diagram 800 of a reflected test signal 810 measured by a test system. For example, a time domain reflectometry (TDR) measurement performed with an automated test equipment (ATE) on a shorted signal path of a DDR2 64site high-speed memory interface is shown. The figure clearly shows the reflected droop information. The horizontal axis shows the time (par_rcvs) in ns with a scale of 1.2 ns/div and the vertical axis shows the signal level (Vth) in V.

In Fig. 8, a fail/pass behavior is indicated, but this is only due to the limited representation possibilities of the test system and may be ignored.

Fig. 9 shows a block diagram of a test system 900 with an apparatus for determining a compensation parameter for compensating a signal level change of a test signal according to an embodiment of the invention. The test system 900 comprises the test signal generator 110 connected to a test signal adapting means 910, the test signal adapting means 910 connected to the signal path 102 and the test signal analyzer 120 connected to the signal path 102. The test signal analyzer 120 is configured to provide the determined compensation parameter 902 to the test signal adapting means 910.

Alternatively, the test signal adapting means 910 may be a part of the test signal generator 110 and the test signal analyzer 120 may provide the determined compensation parameter 902 directly to the test signal generator 110.

The test signal adapting means 910 is configured to adapt the test signal generated by the test signal generator 110 based on the compensation parameter 902 and configured to adapt the test signal in a way that a signal level change of the test signal may be compensated. In this way, the test signal at the end of the signal path not connected to the test signal adapting means 910 and the test signal analyzer 120 may comprise a desired waveform. So, for example, droop effects, impedance mismatches and other discontinuities may be compensated.

Alternatively, the test signal generator 110 may be configured to generate a test signal based on the compensation parameter 902. Then, a test signal adapting means 910 may not be necessary.

The test signal generator 110 may be, for example, a pin electronic driver channel of an ATE.

The test signal analyzer 120 may be connected directly (shown at reference numerals 920) to the output of the test signal adapting means or the output of the test signal generator 110. The connection 920 may also be build, for example, by a coupler configured to adapt the reflected test signal for the test signal analyzer 120, which may be done by amplification, amplitude of phase variation, or a delay.

The test signal analyzer 120 may be, for example a pin electronic receiver channel of an ATE.

Usually, a test system, for example an automated test equipment (ATE) , is compensated as far as the connection 930 to the signal path 102. This may be the connectors of a testhead of an automated test equipment. The described apparatus for determining a compensation parameter and the described test system may provide the possibility to compensate also signal level changes of the signal path, so that a signal with a desired waveform may reach the end of the signal path 102 not connected to the test signal analyzer 120 and the test signal generator 110 or the test signal adapting means 910.

The test signal adapting means 910 or the test signal generator 110 may be configured to determine a necessary waveform of the test signal to obtain a desired waveform of the test signal at the end of the signal path not connected to the test signal generator 110 or the test signal adapting means 910 based on the compensation parameter. The adapting quality of the test signal may be improved by calculating the necessary waveform of the test signal by using a plurality of compensation parameters determined at different times.

Adapting the test signal to provide a compensated test signal at the end of the signal path not connected to the test signal generator 110 or the test signal adapting means

910 may improve the waveform. For example, the edge steepness or the rise or fall time of a square wave signal, a rectangular pulse, a step wave or in general a rising or a falling edge of a signal may be optimized.

Some embodiments according to the invention relate to a time-domain-reflectometry (TDR) -based fixture attenuation calibration (Fatt-cal) .

Some further embodiments according to the invention relate to a new concept of a time-domain-reflectometry (TDR) -based fixture attenuation calibration in the signal level domain in order to address the issue of level inaccuracy caused by the fixture (of an ATE with a DUT) . This may be a compliment to the fixture delay calibration in the signal time domain. The idea is based on the fact that a TDR measurement may not only reveal signal path delay information but also may reveal signal attenuation information that is inherent to the fixture signal path and can be analyzed and evaluated for compensation, for example, by an ATE itself.

Similar to the fixture delay calibration, the fixture attenuation calibration could be implemented in a way that it can be executed by the user for selected signal paths, for example assigned to specific ATE channels, of a given fixture. The obtained compensation values (compensation parameters) for the selected signal paths on the fixture can be stored to a data structure that accompanies the fixture, for example independently of the system calibration data, and can be loaded to the ATE for compensation whenever the fixture is used together with the ATE. Alternatively, the compensation parameters may be stored directly by the ATE and may be loaded when the fixture is used.

Some embodiments according to the invention relate to the very frequently occurring case of signal droop. An important property for the proposed method is the fact that the reflected wave (reflected test signal) caused, for example, by an incident step wave (test signal) as used for a regular TDR measurement shows a similar signal droop as the signal at the signal path output. This may be the case for either a reflection at the open or the shorted end.

The difference, however, is that the signal droop of the reflected wave results from the step wave traveling forth and back the measured signal path. Nevertheless, the reflected signal may carry the full information on the droop properties of the signal path and the single way properties can be obtained from a suitable calculation on the reflected signal data.

The calculation may be based on a measured signal level of the reflected test signal and, for example, a database of calibration values based on a comparison of transmitted test signals with reflected test signals. Alternatively, since the signal level change of the test signal may be proportional to the signal level change of the reflected test signal, an amplification of the test signal proportional to the measured signal level of the reflected test signal may be done to compensate the signal level change .

Some embodiments according to the invention relate to a droop compensation circuitry (a test system with an apparatus for determining a compensation parameter) providing several time constants to implement an inverse behavior of the expected droop, the information for setting the compensation values (compensation parameters) can be obtained from several level measurement at different timing points on the reflected TDR waveform (the reflected test signal) .

To achieve this, the ATE (test system) can send an incident step wave (test signal) with its pin electronic driver channel, for example calibrated to the testhead connector, into the fixture (signal path) and simultaneously receive the reflected waveform with its pin electronic receiver channel, also calibrated to the testhead connector.

For example, when additionally the fixture delay calibration is performed correctly, the reflected droop step may be seen by the ATE at time t=0. Referring to this timing reference (arrival time of the reflected test signal) , the ATE may execute a level measurement at given time differences to this reference point according to the given time constants.

From the measured level attenuation information, the compensation values (compensation parameter) can be derived according to a suitable algorithm. This may be, for example, a multiplication of the measured signal level with a constant or a calibration parameter stored in a memory. Then, the test signal may be amplified or attenuated based on the compensation values or compensation parameters.

Such a measurement (measurement of a signal level of a reflected signal) can also be performed by any other suitable instrument, for example such as a time domain reflectometry (TDR) scope. As with the fixture delay measurement, the level measurement can also be conducted by the fixture manufacturer before shipment. The obtained compensation parameters may be stored by a memory unit of the fixture and may be loaded later on by the ATE.

In some embodiments according to the invention, the test signal analyzer 120 is configured to compare a signal level of the test signal and a signal level of the reflected test signal and configured to determine the compensation parameter based on the comparison of the signal level of the test signal and the signal level of the reflected test signal.

Some further embodiments according to the invention relate to determining compensation parameters for impedance mismatches and other discontinuities. Trace impedance mismatches and other discontinuities in the fixture signal path often result in level attenuation or level overshoot. Also in these case a TDR-based level measurement can be used to determine fixture-related level compensation values, because the reflected wave may also reveal the respective kind of level information. Many of these cases cause effects that behave similar to the droop effect and can therefore be readily compensated with the same level compensation circuitry. Therefore, the proposed method is a very flexible strategy to enhance the accuracy of the ATE, for example, in conjunction with fixtures for very high speed and/or very high parallelism.

Some embodiments according to the invention relate to a possible data structure that contains the per pin fixture attenuation compensation values (the compensation parameters) . A modified channel attribute file loaded with a testflow setup (by an ATE) as an example of a possible data structure that contains the per pin fixture attenuation compensation values may be:

hp93000,chan_attribute, 0.1

SATR 0

FXDL 20501,2.004

FXDL 20502,2.026 #fixture path delay information FXDL 20503,2.218

FXDL 20504,2.216

FATT 20501,0.512,0.732,0.918 #fixture attenuation information FATT 20502,0.482,0.639,0.817 #expressed in a fraction of full scale

FATT 20503,0.534,0.697,0.912 # (determined at three timing points) FATT 20504,0.552,0.678,0.875

In this example, hp93000 is the name of the test system, chan_attribute is the name of the file, FXDL stands for fixture delay followed by the channel number (e.g. 20501) and the path delay information in ns (e.g. 2.004), and FATT stands for fixture attenuation followed by the channel number and followed by three compensation parameters (e.g. 0.512, 0.732, 0.918) determined at three different timing points .

For example, the compensation parameters indicate the fraction of the signal level of the test signal reached by the reflected test signal.

Fig. 10 shows a flowchart of a method 1000 for determining a compensation parameter for compensating a signal level change of a test signal according to an embodiment of the invention. The signal level change is caused by a propagation of the test signal along a signal path. The method 1000 comprises providing 1010 the test signal, coupling 1020 the test signal into the signal path, analyzing 1030 a reflection of the test signal and determining 1040 the compensation parameter.

The analysis 1030 of the reflected test signal is based on determining a signal level of the reflected test signal.

Determining 1030 the compensation parameter is based on the analysis of the reflected test signal.

Some embodiments according to the invention relate to a method for providing a compensated test signal for compensating a signal level change of a test signal. The method comprises an adapting of the test signal based on the compensation parameter to obtain a compensated test signal.

In the present application, the same reference numerals are partly used for objects and functional units having the same or similar functional properties.

In particular, it is pointed out that, depending on the conditions, the inventive scheme may also be implemented in software. The implementation may be on a digital storage medium, particularly a floppy disk or a CD with electronically readable control signals capable of cooperating with a programmable computer system so that the corresponding method is executed. In general, the invention thus also consists in a computer program product with a program code stored on a machine-readable carrier for performing the inventive method, when the computer program product is executed on a computer. Stated in other words, the invention may thus also be realized as a computer program with a program code for performing the method, when the computer program product is executed on a computer.

Claims

1. Apparatus (100) for determining a compensation parameter for compensating a signal level change of a test signal, wherein the signal level change is caused by a propagation of the test signal along a signal path (102), comprising:

a test signal generator (110) configured to provide the test signal and couple it into the signal path (102); and

a test signal analyzer (120) configured to analyze a reflection of the test signal and configured to determine the compensation parameter based on the analysis of the reflected test signal, wherein the analysis of the reflected test signal is based on determining a signal level of the reflected test signal .

2. Apparatus for determining a compensation parameter according to claim 1, wherein the test signal analyzer (120) is configured to determine a plurality of signal levels of the reflected test signal at different times and is configured to determine a compensation parameter for each determined signal level of the plurality of signal levels.

3. Apparatus for determining a compensation parameter according to claim 2, wherein the test signal analyzer

(120) is configured to determine a further compensation parameter between two already determined compensation parameters by linear interpolation or another fitting algorithm.

4. Apparatus for determining a compensation parameter according to one of the claims 1 to 3, wherein the signal path (102) comprises a first end and a second end, wherein the first end is connected to the test signal generator (110) and the test signal analyzer (120), and wherein the second end is open or shorted.

5. Apparatus for determining a compensation parameter according to one of the claims 1 to 4, wherein the test signal analyzer (120) is configured to compare a signal level of the test signal and a signal level of the reflected test signal and configured to determine the compensation parameter based on the comparison of the signal level of the test signal and the signal level of the reflected test signal.

6. Apparatus for determining a compensation parameter according to one of the claims 1 to 5, comprising a memory unit, wherein the test signal analyzer (120) is configured to determine a plurality of compensation parameters for a plurality of different signal paths, wherein the plurality of compensation parameters is stored by the memory unit.

7. Apparatus for determining a compensation parameter according to one of the claims 1 to 6, wherein the test signal analyzer (120) is configured to determine a delay parameter for compensating a delay of the test signal based on the analysis of the reflected test signal .

8. Test system for providing a compensated test signal with an apparatus for determining a compensation parameter according to one of the claims 1 to 7, wherein the test signal generator (110) is configured to adapt the test signal based on the compensation parameter to obtain the compensated test signal.

9. Test system for providing a compensated test signal with an apparatus for determining a compensation parameter according to one of the claims 1 to 7, comprising a test signal adapting means (910) configured to adapt the test signal provided by the test signal generator (110) based on the compensation parameter to obtain the compensated test signal.

10. Method (1000) for determining a compensation parameter for compensating a signal level change of a test signal, wherein the signal level change is caused by a propagation of the test signal along a signal path, comprising:

providing (1010) the test signal;

coupling (1020) the test signal into the signal path;

analyzing (1030) a reflection of the test signal, wherein the analysis of the reflected test signal is based on determining a signal level of the reflected test signal; and

determining (1040) the compensation parameter based on the analysis of the reflected test signal.

11. Method for providing a compensated test signal for compensating a signal level change of a test signal, wherein the signal level change is caused by a propagation of the test signal along a signal path, comprising:

providing the test signal;

coupling the test signal into the signal path;

analyzing a reflection of the test signal, wherein the analysis of the reflected test signal is based on determining a signal level of the reflected test signal; II

determining the compensation parameter based on the analysis of the reflected test signal; and

adapting the test signal based on the compensation parameter to obtain the compensated test signal.

12. Method for providing a compensated test signal according to claim 11, wherein adapting the test signal comprises an amplification of the test signal, a change of the amplitude or a phase of the test signal or a delay of the test signal.

13. Computer program with a program code for performing the method according to one of claims 10 to 12, when the computer program runs on a computer or a microcontroller.