Measurement device and method for performing vector signal analysis

Abstract

The invention relates to a measuring device and a method for performing vector signal analysis. The measurement device comprises: an input port arranged to be connected to a device under test (DUT) wherein the input port is configured to receive repeated measurement signals from the DUT; and a processor configured to determine a reference signal based on at least one repetition of the received measurement signal, where the processor is configured to iteratively adjust the determined reference signal in at least one further repetition of the measurement signal.

Description

Technical Field

[0001] The present invention relates to a measurement device and a method for performing vector signal analysis. Background Art

[0002] In vector signal analysis (VSA), the quality of the measured signal sent by the device under test (DUT) is compared with an ideal signal, also called a reference signal. To ensure correct VSA measurements, the reference signal must be correct, meaning it must be based on the same sign as the measured signal.

[0003] VSA applications typically extract a reference signal from the measurement signal. However, if, for example, the measurement signal has a low signal-to-noise ratio (SNR), detection errors can occur. To ensure a correct reference signal, such detection errors should be avoided or corrected. However, correcting for detection errors requires knowledge of the actual bit sequence in the measurement signal, which is sometimes unknown or poorly understood. Currently, if the user has no way to provide the actual bit sequence of the measurement signal, they may not be able to detect and correct potential erroneous reference signals that could lead to erroneous VSA measurements. Summary of the Invention

[0004] Therefore, there is a need to provide an improved measurement device and an improved method for performing vector signal analysis, which avoid the above-mentioned disadvantages.

[0005] These and other objects are achieved by the embodiments provided in this application. Advantageous implementations of the invention are further defined in this application.

[0006] According to a first aspect, the present invention relates to a measurement device for performing vector signal analysis. The measurement device comprises: an input port arranged to be connected to a device under test (DUT); wherein the input port is configured to receive a repeated measurement signal from the DUT; and a processor configured to determine a reference signal based on at least one repetition of the received measurement signal; wherein the processor is configured to iteratively adjust the determined reference signal in at least one further repetition of the measurement signal.

[0007] This provides the advantage of providing a correct reference signal even in a low SNR (Signal-to-Noise Ratio) environment. Thus, incorrect VSA measurements caused by an erroneous reference signal can be avoided.

[0008] The measuring device may be a vector signal analyzer or a measuring instrument with a vector signal analysis function.

[0009] The DUT may be a communication device. The measurement signal may be an RF signal transmitted by the DUT. The measurement signal may be an I / Q signal. For example, the measurement signal includes symbols transmitted at a determined symbol rate.

[0010] The repeated measurement signal may be repeatedly sent by the DUT and / or repeatedly captured by the measurement device. Alternatively, multiple repetitions of the measurement signal may be received in one capture.

[0011] The reference signal may be an idealized (e.g., error-free and / or interference-free) version of the measurement signal. The reference signal may include the same symbols and / or symbol sequences as the measurement signal. The VSA measurement may include a comparison of the reference signal and the measurement signal.

[0012] The input port may be an RF (Radio Frequency) port.

[0013] The processor may be an ASIC (Application Specific Integrated Circuit) or a microprocessor of the measuring device.

[0014] The processor may be configured to adjust the determined reference signal over a plurality of further repetitions (and / or captures) of the measurement signal. The adjustment may be performed after each repetition / capture.

[0015] In one embodiment, the processor is configured to iteratively adjust the reference signal over a plurality of repetitions of the measurement signal based on a deterministic correction and / or based on a statistical error correction.

[0016] For example, in subsequent iterations of capture by the measurement device, different deterministic corrections (eg, channel filters, etc.) may be applied.

[0017] In one embodiment, the processor is configured to adjust the reference signal by performing I / Q averaging in at least two repetitions of the measurement signal and / or by calculating a probability distribution of symbols in at least two repetitions of the measurement signal.

[0018] For example, the processor can generate a histogram showing the distribution of symbol points in at least two repetitions of the measurement signal. The symbol that appears most frequently at a point in the measurement signal can be estimated as the correct symbol. In addition, the processor can be configured to correct nonlinearities in the measurement signal, such as nonlinearities that always appear at the same symbol (a common WiFi 7 problem).

[0019] In one embodiment, the processor is configured to adjust the reference signal by performing noise cancellation, equalization, channel filtering, and / or digital pre-distortion (DPD).

[0020] In one embodiment, the processor is configured to calculate a signal quality metric for the DUT based on a comparison of the measured signal with a conditioned reference signal. This provides the advantage that the processor can use the conditioned reference signal for VSA measurements. For example, the processor can thereby calculate an error vector magnitude (EVM).

[0021] In one embodiment, the processor is configured to perform a quality estimation of the adjusted reference signal. For example, the processor performs the quality estimation of the adjusted reference signal after each adjustment of the reference signal.

[0022] In one embodiment, the quality estimation comprises determining the extent of change of the reference signal at least after a most recent adjustment of the reference signal.

[0023] In one embodiment, the processor is configured to stop further adjustment of the reference signal if the quality estimate results in that the adjusted reference signal meets a quality condition.

[0024] In other words, the processor may freeze the adjustment of the reference signal if the quality condition is met, i.e., if the processor detects that the reference signal is "good enough." For example, the quality condition is met when the adjustment of the reference signal results in a change in the signal characteristic that is less than a threshold.

[0025] In one embodiment, if further adjustment of the reference signal is stopped, the processor is configured to extract symbols from the adjusted reference signal, wherein the processor is configured to store the extracted symbols in a memory of the measurement device. This provides the advantage that the stored symbols can be used for subsequent VSA measurements.

[0026] For example, the processor may extract symbols from the reference signal by demodulating the reference signal.

[0027] In one embodiment, the processor is configured to demodulate the measurement signal to detect symbols in the measurement signal; and calculate a symbol error rate and / or a bit error rate by comparing the detected symbols with pre-extracted symbols from the adjusted reference signal.

[0028] For example, the pre-extracted symbols are symbols stored in the memory.

[0029] According to a second aspect, the present invention relates to a method for performing vector signal analysis. The method comprises: connecting a device under test (DUT) to an input port of a measurement device; receiving a repeated measurement signal from the DUT at the input port; determining a reference signal based on at least one repetition of the received measurement signal; and iteratively adjusting the determined reference signal in at least one further repetition of the measurement signal.

[0030] The method according to the second aspect of the present invention may be performed by the measuring device according to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above aspects and implementation forms of the present invention will be explained in the following description of specific embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 shows a schematic diagram of a measurement device for performing vector signal analysis according to one embodiment;

[0033] Figure 2 According to one embodiment, Figure 1 The operating principle of the measuring equipment shown; and

[0034] Figure 3 A flow chart of a method for performing vector signal analysis according to one embodiment is shown. DETAILED DESCRIPTION

[0035] Figure 1 A schematic diagram of a measuring device 10 for performing vector signal analysis according to one embodiment is shown.

[0036] The measurement device 10 comprises an input port 11, which is arranged to be connected to a DUT 20, wherein the input port 11 is configured to receive a repeated measurement signal from the DUT 20. The measurement device 10 further comprises a processor 12, which is configured to determine a reference signal based on at least one repetition of the received measurement signal; wherein the processor 12 is configured to iteratively adjust the determined reference signal in at least one additional repetition of the measurement signal.

[0037] Measurement device 10 may be a vector signal analyzer or a measurement instrument with vector signal analysis (VSA) functionality. Measurement device 10 may perform VSA measurements. During a VSA measurement, the quality of the measurement signal may be determined by comparing the measurement signal with a reference signal. Measurement device 10 may reconstruct a reference signal based on the measurement signal transmitted by DUT 20.

[0038] The reference signal may be an idealized (eg, error-free and / or interference-free) version of the measurement signal. The reference signal may include the same symbols and / or symbol sequences as the measurement signal.

[0039] For example, the measurement device 10 first determines an initial reference signal based on at least one repetition of the measurement signal. The initial reference signal may contain errors. The measurement device 10 then iteratively adjusts the reference signal until an "improved" (i.e., corrected) reference signal is reached. After determining the improved reference signal, the measurement device 10 can compare the measurement signal with the improved reference signal as part of the VSA measurement. For example, the measurement device 10 can measure the bit error rate (BER) or symbol error rate (SER) of the measurement signal. BER / SER measurements can directly measure the throughput of a complex DUT. The measurement device 10 can also perform error vector magnitude (EVM) measurements.

[0040] By iteratively adjusting the reference signal, the measurement device 10 can detect and correct errors in the reference signal (e.g., possible symbol decision errors), thereby ensuring correct VSA measurements. Thus, the reference signal can be determined by the device 10 itself (via an iterative method), and no externally provided reference signal or transmitted symbol sequence is required. Furthermore, no visual inspection (e.g., of a constellation diagram) is required to detect an incorrect reference signal. For example, the measurement device 10 can perform BER / SER measurements even without knowledge of the measurement signal.

[0041] The DUT 20 may be a communication device and may have an output port for outputting a measurement signal.

[0042] The measurement signal may be an RF signal. The measurement signal may be an I / Q signal. For example, the measurement signal includes symbols transmitted at a specific symbol rate. The symbols may encode one or more binary digits (bits).

[0043] The repeated measurement signal may be repeatedly sent by the DUT 20 and / or repeatedly captured by the measurement device 10. Alternatively, multiple repetitions of the measurement signal may be received in one capture.

[0044] The input port 11 may be an RF port. The measurement device 10 may be connected to the DUT 20 via a cable.

[0045] The processor 12 may be an ASIC or a microprocessor of the measuring device 10 .

[0046] The processor 12 may be configured to adjust the determined reference signal over multiple repetitions (and / or captures) of the measurement signal, wherein the adjustment may be performed after each repetition / capture.

[0047] The measuring device 10 may further comprise a memory 13, such as a flash memory. For example, symbols extracted from the adjusted reference signal may be stored in the memory.

[0048] After receiving one or more captures of a repeated measurement signal, the processor may utilize all or a subset of the captured signal (ie, multiple measurement signal repetitions) to iteratively adjust and thereby improve the reference signal.

[0049] For example, the processor 12 may be configured to adjust the reference signal based on a deterministic correction. Additionally or alternatively, the processor 12 may be configured to adjust the reference signal based on a statistical error correction of multiple repetitions of the measurement signal.

[0050] Statistical error correction may include I / Q averaging of the reference signal and / or the measurement signal to reduce DUT and / or VSA noise.The processor 12 may also perform I / Q noise cancellation.

[0051] Additionally or alternatively, the processor 12 may perform any of the following on the measurement signal and / or the reference signal: equalization or channel filtering; digital predistortion (DPD); and making symbol decisions based on an estimated probability distribution (e.g., via a histogram of symbol instances).

[0052] Furthermore, the DUT 20 or a portion of the DUT 20 can be disconnected from the measuring device 10 step by step (eg component testing) and a calibrated reference signal can be recorded each time.

[0053] Processor 12 may be configured to compare the adjusted reference signal to the measurement signal to determine a signal quality metric for DUT 20. This may be done after each adjustment of the reference signal and / or after a final adjustment (ie, freezing) of the reference signal.

[0054] For example, a signal quality metric can be an error vector magnitude (EVM) value. To calculate the EVM value, a (adjusted) complex baseband reference signal can be subtracted from the complex baseband measurement signal, where the magnitude of the error vector represents the EVM value. If the EVM value is low, the DUT's signal quality is high.

[0055] Figure 2 The operating principle of the measuring device 10 according to one embodiment is shown, in particular the iterative adjustment of the reference signal.

[0056] After the first capture of the measurement signal, an initial reference signal (Initial Ref) can be generated. Based on this initial reference signal, universal synchronization or EVM measurement can be performed.

[0057] After subsequent capture of the measurement signal, the initial reference signal can be adjusted to generate an improved reference signal. For each adjusted reference signal, a corresponding universal synchronization or EVM measurement can be performed.

[0058] After each adjustment, the processor 12 may perform a quality estimation of the adjusted reference signal. For example, the quality estimation comprises determining the extent of change of the reference signal after at least the most recent adjustment of the reference signal.

[0059] In one example, the processor 12 compares each newly generated (or adjusted) reference signal in step N with the previously generated reference signal(s) in steps (N-1), (N-2), ... and determines whether the reference signal is stable.

[0060] For example, the processor 12 may use a metric to determine whether the reference signal is "good enough," such as whether it is stable within a certain measurement uncertainty, or whether further adjustment is required. The metric may consider the stability of the signal based on various factors, such as: histogram (e.g., if the symbol is unchanged), code utilization on the signal, calculated parameters (e.g., EVM, bit error rate, or symbol error rate), or the spacing between the ideal constellation point and the reference signal detection point.

[0061] Then, when the reference signal stabilizes, the processor 12 can "freeze" the reference signal (i.e., no longer adjust the reference signal). In other words, if the quality estimate indicates that the adjusted reference signal meets a quality condition, the processor 12 stops further adjusting the reference signal. The quality condition can be that the change in signal characteristics before and after adjustment is less than a threshold.

[0062] If further adjustment of the reference signal is stopped (i.e., the reference signal is frozen), the processor 12 can be configured to extract symbols from the adjusted reference signal, for example by demodulation. The processor 12 can then store these symbols (symbols of the stable reference signal) in the memory 13. In this way, subsequent measurements can be accelerated because the reference signal can be retrieved from the memory without having to be recalculated.

[0063] The processor can perform VSA measurements using a frozen reference signal generated through iterative adjustment. For example, the processor 12 can demodulate the measurement signal to extract symbols and compare these symbols with pre-extracted symbols of the "frozen" reference signal (e.g., symbols extracted and stored in memory after the reference signal was frozen). In this way, SER or BER measurements can be performed with the measurement signal, or possible symbol decision errors can be detected without having to determine and / or demodulate the reference signal each time.

[0064] Figure 3A flow chart of a method 30 for performing vector signal analysis according to one embodiment is shown. The method 30 may be used as follows Figure 1 The measuring device 10 shown is used to perform the above.

[0065] The method 30 comprises connecting 31 a DUT 20 to an input port 11, for example, the input port 11 of the measuring device 10; receiving 32 a repeated measurement signal from the DUT 20 at the input port 11; determining 33 a reference signal based on at least one repetition of the received measurement signal; and iteratively adjusting 34 the determined reference signal in at least one further repetition of the measurement signal.

[0066] The method 30 may also include performing a VSA measurement (eg, an EMV, BER, or SER measurement) on the DUT 20 using the adjusted reference signal.

[0067] Within the scope of the invention, all features mentioned above or shown in the drawings can be combined with one another in any advantageous manner.

Claims

1. A measurement device for performing vector signal analysis, comprising: an input port arranged to be connected to a device under test, wherein the input port is configured to receive a repeated measurement signal from the device under test; and a processor configured to determine a reference signal based on at least one repetition of the received measurement signal, Therein, the processor is configured to iteratively adjust the determined reference signal in at least one further repetition of the measurement signal.

2. The measuring device according to claim 1, wherein The processor is configured to iteratively adjust the reference signal over a plurality of repetitions of the measurement signal based on a deterministic correction and / or based on a statistical error correction.

3. The measuring device according to claim 1, wherein The processor is configured to adjust the reference signal by performing I / Q averaging in at least two repetitions of the measurement signal and / or by calculating a probability distribution of symbols in at least two repetitions of the measurement signal.

4. The measuring device according to claim 1, wherein The processor is configured to adjust the reference signal by performing noise cancellation, equalization, channel filtering, and / or digital predistortion.

5. The measuring device according to claim 1, wherein The processor is configured to calculate a signal quality metric of the device under test based on a comparison of the measurement signal and an adjusted reference signal.

6. The measuring device according to claim 1, wherein The processor is configured to perform quality estimation of an adjusted reference signal.

7. The measuring device according to claim 6, wherein The quality estimation comprises determining the extent of change of the reference signal at least after a most recent adjustment of the reference signal.

8. The measuring device according to claim 6, wherein The processor is configured to stop further adjustment of the reference signal if the quality estimate results that the adjusted reference signal meets a quality condition.

9. The measuring device according to claim 8, in, If further adjustment of the reference signal is stopped, the processor is configured to extract symbols from the adjusted reference signal; The processor is configured to store the extracted symbol in a memory of the measuring device.

10. The measuring device according to claim 1, in, The processor is configured to demodulate the measurement signal to detect a sign of the measurement signal; as well as The processor is configured to calculate a symbol error rate and / or a bit error rate by comparing the detected symbols with pre-extracted symbols from the adjusted reference signal.

11. A method for performing vector signal analysis, comprising: Connect the device under test to the input port of the measuring device; receiving a repetitive measurement signal from the device under test at the input port; determining a reference signal based on at least one repetition of the received measurement signal; as well as The determined reference signal is iteratively adjusted in at least one further repetition of the measurement signal.

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