Error vector measurement apparatus and method

Abstract

The application discloses an error vector measurement device, comprising: a signal sampling module, which is used for collecting radio frequency signals on a device to be measured; a radio frequency receiving channel module, which is used for changing the collected radio frequency signals into baseband signals; a sampling point acquisition module, which is used for acquiring an optimal sampling sequence according to the baseband signals; a measurement value acquisition module, which is used for calculating the average amplitude of the baseband signals according to the optimal sampling sequence; a power estimation module, which is used for obtaining the average power, noise power and useful signal power of the baseband signals according to the optimal sampling sequence and the average amplitude; an EVM acquisition module, which is used for obtaining the EVM according to the noise power and the signal power. The application also discloses an error vector measurement method. The application reduces the complexity of measurement and improves the accuracy of measurement.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, specifically to an error vector measurement device and method. Background Technology

[0002] In an ideal radio frequency (RF) system, the signal transmitted by the transmitter is in an ideal position. However, in reality, due to various imperfections in the RF system, such as phase noise, low image rejection ratio, and carrier leakage, the signal position changes and deviates from the ideal position. The deviation between the actual signal and the ideal signal is the error vector, such as... Figure 1 As shown, error vector magnitude (EVM) refers to the difference between the theoretical waveform and the received actual waveform, and is the root mean square of the ratio of the average error vector signal power to the average reference signal power. Therefore, it can directly represent the signal quality of a wireless system and is a very important indicator in various current wireless communication systems. While the definition of EVM is very simple, in practice, due to imperfections in the crystal oscillator, frequency offset in the actual signal, and timing synchronization issues, a series of problems can significantly complicate EVM measurement. Patent CN202011108895.2 requires the use of a known signal with no frequency offset; patent CN201710585721.7 performs frequency offset correction, channel estimation, and equalization on the received signal before measuring EVM. The former adds constraints, while the latter increases the complexity of the measurement. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing methods by providing an error vector measurement device and method that reduces the complexity of measurement and improves the accuracy of measurement.

[0004] The technical solution to achieve the above objectives is:

[0005] One of the present inventions provides an error vector measurement device, comprising:

[0006] The signal sampling module is used to acquire radio frequency signals from the device under test.

[0007] The radio frequency receiving channel module is used to convert the acquired radio frequency signals into baseband signals;

[0008] The sampling point acquisition module is used to obtain the optimal sampling sequence based on the baseband signal;

[0009] The measurement acquisition module is used to calculate the average amplitude of the baseband signal based on the optimal sampling sequence.

[0010] The power estimation module is used to obtain the average power, noise power, and useful signal power of the baseband signal based on the optimal sampling sequence and average amplitude.

[0011] The EVM acquisition module is used to obtain the EVM based on noise power and signal power.

[0012] Preferably, the radio frequency receiving channel module includes:

[0013] The downconversion unit is used to convert the acquired radio frequency signal from a high-frequency signal to a zero-IF signal;

[0014] The AD conversion unit is used to sample the zero intermediate frequency signal to obtain a digital signal;

[0015] The filtering downsampling unit is used to transform the digital signal obtained by the AD conversion unit into the required baseband signal.

[0016] A second method for measuring error vectors according to the present invention includes:

[0017] Step S1: Acquire radio frequency signals on the device under test;

[0018] Step S2: Convert the acquired radio frequency signal into a baseband signal;

[0019] Step S3: Obtain the optimal sampling sequence based on the baseband signal;

[0020] Step S4: Calculate the average amplitude of the baseband signal based on the optimal sampling sequence;

[0021] Step S5: Obtain the average power, noise power, and useful signal power of the baseband signal based on the optimal sampling sequence and average amplitude;

[0022] Step S6: Obtain EVM based on noise power and signal power.

[0023] Preferably, step S2 includes:

[0024] Step S21: Convert the acquired radio frequency signal from a high-frequency signal to a zero-IF signal by down-conversion;

[0025] Step S22: Sample the zero intermediate frequency signal to obtain a digital signal;

[0026] Step S23: Transform the digital signal to obtain the required baseband signal.

[0027] Preferably, in step S3, obtaining the optimal sampling sequence includes:

[0028] First, calculate an energy sequence P. i ;

[0029]

[0030] In the formula, i = 0, 1, ... γ-1, abs(*) is the absolute value, rx(*) is the baseband signal, and N is the length of the baseband signal;

[0031] Secondly, find the i corresponding to the maximum value of the energy sequence.

[0032] P τ =max(P i );

[0033] The timing τ at this point can then be obtained;

[0034] Finally, the optimal sampling sequence rx' is obtained. j ,

[0035] rx' j =rx(j*γ+τ);

[0036] In the formula, j = 0, 1, ... N-1.

[0037] Preferably, in step S4, the average amplitude var of the baseband signal is calculated using the following formula:

[0038]

[0039] In the formula, abs(*) is the absolute value, and rx' j This is the optimal sampling sequence.

[0040] Preferably, in step S5, the average power rssi of the baseband signal is calculated using the optimal sampling sequence.

[0041]

[0042] The noise power n of the baseband signal is calculated using the average power rssi and the average amplitude var. p ,

[0043] n p =2*(rssi-var) 2 );

[0044] Through average power rssi and noise power n p Calculate the useful signal power sig of the baseband signal p ,

[0045] sig p =rssi-n p .

[0046] Preferably, in step S6, the EVM is obtained through noise power and signal power, and the calculation formula is as follows:

[0047]

[0048] The beneficial effects of this invention are as follows: This invention acquires radio frequency (RF) signals from the device under test (DUT), converts the acquired RF signals from high-frequency signals to zero-IF signals, samples the zero-IF signals to obtain digital signals, transforms the digital signals to obtain the required baseband signals, and obtains the optimal sampling sequence, average amplitude, average power, noise power, and useful signal power based on the baseband signals, finally obtaining the EVM value. This invention does not require the transmission of known signal sequences and does not perform frequency offset estimation and correction, channel estimation, equalization, or other calculations on the baseband signals, yet still achieves high estimation accuracy, reduces measurement complexity, and improves measurement accuracy. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the error vector, which represents the deviation between the actual signal and the ideal signal.

[0050] Figure 2 This is a block diagram of an error vector measurement device according to the present invention;

[0051] Figure 3 This is a flowchart of an error vector measurement method according to the present invention;

[0052] Figure 4 This is a flowchart illustrating the specific process of converting the acquired radio frequency signal into a baseband signal in this invention.

[0053] Figure 5 It is an ideal constellation chart;

[0054] Figure 6 This is the constellation diagram after adding a 1500Hz frequency offset;

[0055] Figure 7 This is the constellation diagram after adding 6% EVM;

[0056] Figure 8 This is the final EVM distribution map obtained by this invention. Detailed Implementation

[0057] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings. In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0058] The invention will now be further described with reference to the accompanying drawings.

[0059] like Figure 2 As shown, an error vector measurement device includes: a signal sampling module 1, an RF receiving channel module 2, a sampling point acquisition module 3, a measurement value acquisition module 4, a power estimation module 5, and an EVM acquisition module 6.

[0060] Signal sampling module 1 is used to acquire radio frequency signals on the device under test.

[0061] RF receiving channel module 2 is used to convert the acquired RF signal into a baseband signal.

[0062] In this embodiment, the radio frequency receiving channel module 2 specifically includes: a downconversion unit 21, an AD conversion unit 22, and a filtering downsampling unit 23; the downconversion unit 21 is used to convert the acquired radio frequency signal from a high-frequency signal into a zero-IF signal; the AD conversion unit 22 is used to sample the zero-IF signal to obtain a digital signal; and the filtering downsampling unit 23 is used to transform the digital signal obtained by the AD conversion unit 22 into the required baseband signal.

[0063] The sampling point acquisition module 3 is used to obtain the optimal sampling sequence based on the baseband signal.

[0064] The measurement acquisition module 4 is used to calculate the average amplitude of the baseband signal based on the optimal sampling sequence.

[0065] The power estimation module 5 is used to obtain the average power, noise power and useful signal power of the baseband signal based on the optimal sampling sequence and average amplitude.

[0066] EVM acquisition module 6 is used to obtain EVM based on noise power and signal power.

[0067] like Figure 3 As shown, an error vector measurement method includes:

[0068] Step S1: Acquire radio frequency signals on the device under test.

[0069] Step S2: Convert the acquired radio frequency signal into a baseband signal.

[0070] like Figure 4 As shown, step S2 specifically includes:

[0071] Step S21: Convert the acquired radio frequency signal from a high-frequency signal to a zero-IF signal by down-conversion;

[0072] Step S22: Sample the zero intermediate frequency signal to obtain a digital signal;

[0073] Step S23: Transform the digital signal to obtain the required baseband signal.

[0074] Step S3: Obtain the optimal sampling sequence based on the baseband signal.

[0075] In this embodiment, obtaining the optimal sampling sequence includes:

[0076] First, calculate an energy sequence P. i ;

[0077]

[0078] In the formula, i = 0, 1, ... γ-1, abs(*) is the absolute value, rx(*) is the baseband signal, and N is the length of the baseband signal;

[0079] Secondly, find the i corresponding to the maximum value of the energy sequence.

[0080] P τ =max(P i );

[0081] The timing τ at this point can then be obtained;

[0082] Finally, the optimal sampling sequence rx' is obtained. j ,

[0083] rx' j =rx(j*γ+τ);

[0084] In the formula, j = 0, 1, ... N-1.

[0085] Step S4: Calculate the average amplitude of the baseband signal based on the optimal sampling sequence.

[0086] In this embodiment, the average amplitude var of the baseband signal is calculated using the following formula:

[0087]

[0088] In the formula, abs(*) is the absolute value, and rx' j This is the optimal sampling sequence.

[0089] Step S5: Obtain the average power, noise power, and useful signal power of the baseband signal based on the optimal sampling sequence and average amplitude.

[0090] In this embodiment, the average power rssi of the baseband signal is calculated using the optimal sampling sequence.

[0091]

[0092] The noise power n of the baseband signal is calculated using the average power rssi and the average amplitude var. p ,

[0093] n p =2*(rssi-var) 2 );

[0094] Through average power rssi and noise power n p Calculate the useful signal power sig of the baseband signal p ,

[0095] sig p =rssi-n p .

[0096] Step S6: Obtain EVM based on noise power and signal power.

[0097] In this embodiment, EVM is obtained by combining noise power and signal power, and the calculation formula is as follows:

[0098]

[0099] This invention was verified using MATLAB. 100 tests were conducted with a frequency offset of 1500Hz and an EVM of 6. The ideal constellation diagram is shown below. Figure 5 As shown, the constellation diagram after adding a 1500Hz frequency offset is as follows. Figure 6 As shown, the constellation diagram after adding 6% EVM is as follows: Figure 7 As shown, the obtained EVM distribution is as follows: Figure 8 As shown, when the EVM is set to 6, the estimated EVM is 5-7, meaning that the maximum deviation between the single estimate and the ideal value is 1%.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An error vector measurement device, characterized in that, include: The signal sampling module is used to acquire radio frequency signals from the device under test. The radio frequency receiving channel module is used to convert the acquired radio frequency signals into baseband signals; The sampling point acquisition module is used to obtain the optimal sampling sequence based on the baseband signal; The measurement acquisition module is used to calculate the average amplitude of the baseband signal based on the optimal sampling sequence. The power estimation module is used to obtain the average power, noise power, and useful signal power of the baseband signal based on the optimal sampling sequence and average amplitude. The EVM acquisition module is used to obtain the EVM based on the noise power and the useful signal power. To obtain the optimal sampling sequence, including: First, calculate an energy sequence. ; ； In the formula, , To find the absolute value, For baseband signals, The length of the baseband signal; Secondly, find the maximum value corresponding to the energy sequence. , ； The timing can then be obtained. ; Finally, the optimal sampling sequence is obtained. , ； In the formula, .

2. The error vector measuring device according to claim 1, characterized in that, The radio frequency receiving channel module includes: The downconversion unit is used to convert the acquired radio frequency signal from a high-frequency signal to a zero-IF signal; The AD conversion unit is used to sample the zero intermediate frequency signal to obtain a digital signal; The filtering downsampling unit is used to transform the digital signal obtained by the AD conversion unit into the required baseband signal.

3. A method for measuring error vectors, characterized in that, include: Step S1: Acquire radio frequency signals on the device under test; Step S2: Convert the acquired radio frequency signal into a baseband signal; Step S3: Obtain the optimal sampling sequence based on the baseband signal; Step S4: Calculate the average amplitude of the baseband signal based on the optimal sampling sequence; Step S5: Obtain the average power, noise power, and useful signal power of the baseband signal based on the optimal sampling sequence and average amplitude; Step S6: Obtain the EVM based on the noise power and the useful signal power; In step S3, obtaining the optimal sampling sequence includes: First, calculate an energy sequence. ; ； In the formula, , To find the absolute value, For baseband signals, The length of the baseband signal; Secondly, find the maximum value corresponding to the energy sequence. , ； The timing can then be obtained. ; Finally, the optimal sampling sequence is obtained. , ； In the formula, .

4. The error vector measurement method according to claim 3, characterized in that, Step S2 includes: Step S21: Convert the acquired radio frequency signal from a high-frequency signal to a zero-IF signal by down-conversion; Step S22: Sample the zero intermediate frequency signal to obtain a digital signal; Step S23: Transform the digital signal to obtain the required baseband signal.

5. The error vector measurement method according to claim 3, characterized in that, In step S4, the average amplitude of the baseband signal is calculated. The calculation formula is as follows: ； In the formula, To find the absolute value, This is the optimal sampling sequence.

6. The error vector measurement method according to claim 5, characterized in that, In step S5, the average power of the baseband signal is calculated using the optimal sampling sequence. , ； Through average power and average amplitude Calculate the noise power of the baseband signal , ； Through average power and noise power Calculate the useful signal power of the baseband signal , 。 7. The error vector measurement method according to claim 6, characterized in that, In step S6, the EVM is obtained by combining the noise power and the useful signal power, using the following calculation formula: 。

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