CN101895354A - Method for measuring signal error vector magnitude in digital domain - Google Patents
Method for measuring signal error vector magnitude in digital domain Download PDFInfo
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- CN101895354A CN101895354A CN2010102313619A CN201010231361A CN101895354A CN 101895354 A CN101895354 A CN 101895354A CN 2010102313619 A CN2010102313619 A CN 2010102313619A CN 201010231361 A CN201010231361 A CN 201010231361A CN 101895354 A CN101895354 A CN 101895354A
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Abstract
The invention belongs to the technical field of digital signal processing in communication technology, in particular to a method for measuring signal error vector magnitude in a digital domain. The invention is used for removing the limit that the prior method can only measure the error vector magnitude of the specific digital signal. The method comprises the following steps: carrying out digital frequency conversion, transforming sampling rate, adjusting power, shaping waveform, phasing, sampling, calculating the error vector magnitude and the like. The method can receive digital signals with different modulation modes, different sampling rates, different energy, and different intermediate frequencies or zero intermediate frequency. The invention can remove the limit that the prior method can only measure the error vector magnitude of the specific digital signal.
Description
Technical field
The invention belongs to the digital signal processing technique field in the communication technology, be specifically related to a kind of method of Error Vector Magnitude (EVM, Error Vector Magnitude) measurement of digital signal.
Background technology
Error Vector Magnitude (EVM) is the important parameter that is used for the quality of gauge signal in the communications field.By calculating the error between actual signal and the ideal signal, come the modulation accuracy of measuring-signal.The EVM value is more little, illustrates that quality of signals is good more.Adopt the mean-square value of the error vector of interior symbol of one or more time slot scope or chip to represent when EVM calculates usually, difference according to modulation system, the calculating object of EVM also can be different, as the signal of QPSK (quarternary phase-shift keying (QPSK)) modulation, be to obtain EVM by the error of calculating amplitude; And the signal of GMSK (Gaussian minimum shift keyed) modulation, because modulation signal is permanent envelope, the signal variation only is embodied in the angle variation, therefore obtains EVM by the angular error of calculating on the planisphere.
The current communications field, communication protocol is varied, and they all have different separately modulation systems, carrier frequency, waveform shaping mode, character rate, spreading rate etc.Along with the fast development of Digital Signal Processing, increasing module begins to change to digitized processing in the communication system, to realize stronger data-handling capacity and the data processing precision of Geng Gao.At numeric field signal is analyzed and also to be seemed more and more important.But, existing error amplitude of the vector measurement mechanism generally all is analog signal to be carried out characteristic frequency sample and calculate the EVM value, the baseband digital signal of perhaps handling lucky is-symbol rate of sample rate or code check integral multiple calculates EVM, and, but have no idea to measure at the signals sampling rate EVM of the digital signal of is-symbol rate or code check integral multiple not.
In sum, the direct analytical sampling rate EVM index of the digital signal of is-symbol rate or code check integral multiple not of existing Error Vector Magnitude measurement mechanism.
Summary of the invention
The objective of the invention is to propose a kind of can compatible different sample rates and modulation system at numeric field signal is carried out the method that Error Vector Magnitude is measured.It not only can compatible different sample rates and modulation system, and the digital intermediate frequency signal or the baseband digital signal that can compatible have the various carrier frequencies of different-energy.
This Error Vector Magnitude method of measurement that the present invention proposes, its flow chart is seen shown in Figure 1, mainly comprise: digital frequency conversion (S1), sample rate conversion (S2), power adjustment (S3), these 6 key steps of waveform shaping (S4), phase place adjustment (S5), sampler and error of calculation amplitude of the vector (S6).
The first step, digital frequency conversion (S1), the signal that receives can be any sample rates, according to the carrier frequency of setting, input signal (signal that receives) and reference carrier signal are carried out mixing, any digital intermediate frequency signal is converted to digital baseband signal or is called zero intermediate frequency signals.Reference carrier signal can realize by the mode of look-up table, also can be used to the signal from the frequency synthesizer.
In second step, sample rate conversion (S2) is with any sample rate conversion to a symbol rate of the zero intermediate frequency signals of first step output or the integral multiple of code check.This sampling rate converting method can utilize methods such as cascaded integrator-comb (CIC, Cascaded Integrator-comb) filter, half-band filter, finite impulse response filter, polynomial interopolation filter to realize.
The 3rd step, power adjustment (S3), because the signal energy that receives is changeable, the power set-up procedure is to decay to a fixing value with the small-signal amplification or with large-signal.
The 4th step, waveform shaping (S4), if received signal has been passed through the root raised cosine filter shaping when emission, then the signal here is after power adjustment (S3) finishes, also need to carry out the filtering of root raised cosine filter or other waveform shaping modes (S4), realize reducing the effect of intersymbol interference.If received signal is not to utilize root raised cosine filter or other waveform shaping modes to be shaped, this step (S4) is skipped, and directly enters phase place set-up procedure (S5).）
In the 5th step, phase place adjustment (S5) is adjusted phase place, makes the extraction operation in the step (S6) can reach the extraction of amplitude peak component.Extract at interval and equate with the over-sampling multiple of input signal.Signals sampling rate is-symbol rate or code check after the extraction.
In the 6th step, sampling and EVM calculating (S6), the phase place adjustment by step (5) have guaranteed that amplitude peak samples to the symbol rate or the code check of signal.Square root by the mean value of error of calculation vector in the certain hour scope obtains the EVM value.This time range is too short will to influence certainty of measurement, longly will increase Measuring Time, generally get one to eight, the length of more a plurality of time slots.Whether the sample rate of the digital signal that so no matter to receive is the integral multiple of symbol rate or code check, how intermediate-freuqncy signal, energy size can measure its EVM value.
In the said method, digital frequency conversion step (S1), when the signal that receives was zero intermediate frequency signals, this step can be deleted.When the signal intermediate frequency that receives was higher, this step can split into double conversion or repeatedly frequency conversion.Sampling rate conversion step (S2) can be a variable sampling rate when realizing, perhaps splits into multistage realization sampling rate conversion, also can reuse one or more such variable sampling rate module and realize repeatedly sampling rate conversion.Power set-up procedure (S3) satisfies under certain threshold value or the constant situation and can delete in the signal power that receives.Phase place set-up procedure (S5) can once be finished, and also can repeatedly repeat.
In the said method, digital frequency conversion (S1), sampling rate conversion (S2), three step execution sequences of power adjustment (S3) can change arbitrarily, be that 6 kinds of orders that permutation and combination generates can, carry out in the middle of also step (S1) and step (3) can being clipped in step (S2), perhaps with step (S2) with (S3) be clipped in step (S1) centre and carry out.
The present invention not only can compatible different sample rates and modulation system, and the digital intermediate frequency signal or the baseband digital signal that can compatible have the various carrier frequencies of different-energy.
Description of drawings
Fig. 1 be the present invention propose signal is carried out the flow chart of Error Vector Magnitude method of measurement at numeric field.
Fig. 2 is an Error Vector Magnitude measurement mechanism structural representation of implementing instantiation of the present invention.
Embodiment
Below in conjunction with Fig. 2, describe in detail and implement example of the present invention.
Corresponding and said method, the present invention has designed the Error Vector Magnitude measurement mechanism.This device comprises connection successively: digital down converter (1), decimal sampling rate converter (2), integral multiple sampling rate converter (3), waveshaper (root raised cosine filter) (4), phase delay device (5), sampler (6), Error Vector Magnitude computing unit (7).Controller (8) is controlled above-mentioned 7 modules respectively.Above-mentioned 7 modules are finished the work of 6 steps of the inventive method respectively under the control of controller (8).
In this embodiment, the signal that the Error Vector Magnitude measurement mechanism receives is a TD-SCDMA(Time Division-Synchronous Code Division Multiple Access, be the CDMA technological of time-division) digital signal, adopt the QPSK modulation system, it is the intermediate-freuqncy signal with 100 KHz carrier waves, sample rate is 26 Mbps, because the spreading rate of TD-SCDMA signal is 1.28Mbps, therefore 26Mbps is 20.3125 times of code check, is not the sampling rate signal of integral multiple code check.
At first, the carrier frequency that disposes digital down converter (1) by controller (8) is 100KHz, and the modulation system of configuration Error Vector Magnitude computing unit (7) is the QPSK modulation.The multiple that controller (8) process calculates decimal sampling rate converter (2) to be needed to change is 0.9846, and sends parameter to decimal sampling rate converter (2).The conversion multiple of controller (8) integral multiple sampling rate converter (3) is set to 4 times.
Digital down converter (1) is with the digital intermediate frequency signal that receives
I,
QTwo-way carries out the digital mixing computing, the zero intermediate frequency that obtains with the 100KHz carrier signal under the identical 26Mbps sample rate
I,
QTwo paths of signals sends decimal sampling rate converter (2) to.
The expression formula of optical mixing process is:
Wherein,
nBe meant
nIndividual sampling instant,
s i ,
s q It is respectively input signal
I,
QTwo paths of signals,
f Ci ,
f Cq Be respectively cosine carrier signal and sinusoidal carrier signal,
y i ,
y q It is respectively the output signal after the mixing
I,
QTwo paths of signals.
Decimal sampling rate converter (2) utilizes the method for polynomial interopolation that signal sampling rate is transformed into 25.6Mbps by 26Mbps, and it is 20 times of code check.Integral multiple sampling rate converter (3) adopts the two-stage half-band filter that signal is risen 4 times of samplings, because half is 0 for the coefficient of half-band filter, and can not introduce intersymbol interference, therefore very little to the influence of signal, and have fine inhibition mirror image and the anti-effect repeatedly of mixing, passband is smooth, therefore is specially adapted to the data transfer rate conversion of the twice of broadband signal.If the signal of handling is narrow band signal (as the GSM signal), can utilize cascaded integrator-comb (CIC, Cascaded Integrator-comb) filter to finish the integral multiple sample rate conversion, can save circuit hardware and power consumption like this.The output signal of integral multiple sampling rate converter (3) has become the digital signal of a zero intermediate frequency, 80 times of over-samplings.Whether the energy size decision according to signal is adjusted signal.
Because the TD-SCDMA signal has adopted root raised cosine filter as forming filter in transmitter, therefore signal demand carries out root raised cosine filtering through waveshaper (4) to signal here, rolling the factor is 0.22, and the over-sampling rate that provides according to controller (8) amplitude of coming normalized signal.Controller (8) makes the sample point of sampler (6) aim at the interior amplitude peak point of each symbolic range, the i.e. situation of EVM minimum by the phase place of control phase delayer (5) adjustment data.Last Error Vector Magnitude computing unit (7) will obtain digital signal with the sample rate of code check 1.28Mbps, obtain the EVM value by the root-mean-square error that compares between received signal and the ideal signal.
Claims (9)
1. the method for a measuring signal error vector magnitude in digital domain is characterized in that concrete steps are:
The first step, digital frequency conversion (S1) carries out mixing according to the carrier frequency of setting with input signal and reference carrier signal, and any digital intermediate frequency signal is converted to digital baseband signal or is called zero intermediate frequency signals; Described reference carrier signal realizes by the mode of look-up table, perhaps is used to the signal from the frequency synthesizer;
In second step, sample rate conversion (S2) is with any sample rate conversion to a symbol rate of the zero intermediate frequency signals of first step output or the integral multiple of code check;
In the 3rd step, power adjustment (S3) is to decay to a fixing value with the small-signal amplification or with large-signal;
The 4th step, waveform shaping (S4) is if received signal has been passed through the root raised cosine filter shaping when emission, then signal also carries out the filtering of root raised cosine filter or other waveform shapings (S4) after power adjustment (S3) finishes, to reduce intersymbol interference; If received signal is not to utilize root raised cosine filter or other waveform shaping modes to be shaped, this step (S4) is skipped, and directly enters phase place set-up procedure (S5);
In the 5th step, phase place adjustment (S5) is adjusted phase place, makes the extraction operation in the step (S6) reach the extraction of amplitude peak component, extracts at interval to equate signals sampling rate is-symbol rate or code check after the extraction with the over-sampling multiple of input signal;
In the 6th step, sampling and EVM calculating (S6), the phase place adjustment by step (5) have guaranteed that amplitude peak samples to the symbol rate or the code check of signal; Square root by the mean value of error of calculation vector in the certain hour scope obtains the EVM value; Described time range is got the length to eight time slots.
2. method according to claim 1 is characterized in that described sample rate conversion (S2), comprises integral multiple conversion and decimal and doubly changes, and adopts cascade integral dressing filter, half-band filter, finite impulse response filter or polynomial interopolation device to realize.
3. method according to claim 1 is characterized in that described digital frequency conversion step (S1), when the signal that receives is zero intermediate frequency signals, and the deletion of this step; When the signal intermediate frequency that receives was higher, this step can split into double conversion or repeatedly frequency conversion.
4. method according to claim 1, it is characterized in that described sampling rate conversion step (S2) is a variable sampling rate when realizing, perhaps split into multistage realization sampling rate conversion, perhaps reuse one or more such variable sampling rate module and realize repeatedly sampling rate conversion.
5. method according to claim 1 is characterized in that described power set-up procedure (S3) satisfies under certain threshold value or the constant situation in the signal power that receives to delete.
6. method according to claim 1 is characterized in that described phase place set-up procedure (S5) is once adjusted to finish, and perhaps repeatedly adjusts and finishes.
7. method according to claim 1 is characterized in that described digital frequency conversion (S1), sampling rate conversion (S2), three step execution sequences of power adjustment (S3) can change arbitrarily.
8. method according to claim 1, it is characterized in that in described digital frequency conversion (S1), sampling rate conversion (S2), three steps of power adjustment (S3), carry out in the middle of perhaps step (S1) and step (3) being clipped in step (S2), perhaps with step (S2) with (S3) be clipped in step (S1) centre and carry out.
9. implement device as method as described in one of claim 1-8, it is characterized in that this device comprises successively connects: digital down converter (1), decimal sampling rate converter (2), integral multiple sampling rate converter (3), waveshaper (4), phase delay device (5), sampler (6), Error Vector Magnitude computing unit (7); Controller (8) is controlled above-mentioned 7 modules respectively; Above-mentioned 7 modules are finished the work of 6 steps of the inventive method respectively under the control of controller (8).
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102904653A (en) * | 2012-10-24 | 2013-01-30 | 复旦大学 | Method for measuring signal EVM (Error Vector Magnitude) in numeric field and realizing device |
| CN103490824A (en) * | 2013-09-04 | 2014-01-01 | 中国电子科技集团公司第四十一研究所 | Reference signal recovery method for EVM analysis |
| CN103841058A (en) * | 2012-11-21 | 2014-06-04 | 电信科学技术研究院 | Method and apparatus for determining EVM (error vector magnitude) |
| CN106249215A (en) * | 2016-07-22 | 2016-12-21 | 华南理工大学 | A kind of sampling ultrasonic phase array signal resolution power that rises the most again improves method |
| CN110149650A (en) * | 2014-08-31 | 2019-08-20 | 优倍快网络公司 | The method and wireless device of monitoring wireless network |
| CN113225286A (en) * | 2021-04-22 | 2021-08-06 | 中国电子科技集团公司第五十四研究所 | UQPSK signal demodulation device with high symbol rate |
| US11451545B2 (en) | 2014-03-07 | 2022-09-20 | Ubiquiti Inc. | Cloud device identification and authentication |
| US11751068B2 (en) | 2014-06-30 | 2023-09-05 | Ubiquiti Inc. | Methods and tools for assisting in the configuration of a wireless radio network |
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| US20070297537A1 (en) * | 2006-06-27 | 2007-12-27 | Luce Lawrence B | System and method for EVM self-test |
| CN101162970A (en) * | 2006-10-12 | 2008-04-16 | 安科特纳有限责任公司 | Digital quality index for qam digital signals |
| CN101373989A (en) * | 2008-10-29 | 2009-02-25 | 北京星河亮点通信软件有限责任公司 | Method and system for testing terminal radio frequency consistency |
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Patent Citations (3)
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| US20070297537A1 (en) * | 2006-06-27 | 2007-12-27 | Luce Lawrence B | System and method for EVM self-test |
| CN101162970A (en) * | 2006-10-12 | 2008-04-16 | 安科特纳有限责任公司 | Digital quality index for qam digital signals |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102904653A (en) * | 2012-10-24 | 2013-01-30 | 复旦大学 | Method for measuring signal EVM (Error Vector Magnitude) in numeric field and realizing device |
| CN103841058A (en) * | 2012-11-21 | 2014-06-04 | 电信科学技术研究院 | Method and apparatus for determining EVM (error vector magnitude) |
| CN103841058B (en) * | 2012-11-21 | 2016-11-02 | 电信科学技术研究院 | A kind of Error Vector Magnitude determines method and device |
| CN103490824A (en) * | 2013-09-04 | 2014-01-01 | 中国电子科技集团公司第四十一研究所 | Reference signal recovery method for EVM analysis |
| US11451545B2 (en) | 2014-03-07 | 2022-09-20 | Ubiquiti Inc. | Cloud device identification and authentication |
| US11751068B2 (en) | 2014-06-30 | 2023-09-05 | Ubiquiti Inc. | Methods and tools for assisting in the configuration of a wireless radio network |
| CN110149650A (en) * | 2014-08-31 | 2019-08-20 | 优倍快网络公司 | The method and wireless device of monitoring wireless network |
| CN110149650B (en) * | 2014-08-31 | 2022-06-28 | 优倍快公司 | Method for monitoring wireless network and wireless device |
| US11943755B2 (en) | 2014-08-31 | 2024-03-26 | Ubiquiti Inc. | Methods and apparatuses for graphically indicating station efficiency and pseudo-dynamic error vector magnitude information for a network of wireless stations |
| CN106249215A (en) * | 2016-07-22 | 2016-12-21 | 华南理工大学 | A kind of sampling ultrasonic phase array signal resolution power that rises the most again improves method |
| CN113225286A (en) * | 2021-04-22 | 2021-08-06 | 中国电子科技集团公司第五十四研究所 | UQPSK signal demodulation device with high symbol rate |
| CN113225286B (en) * | 2021-04-22 | 2022-03-01 | 中国电子科技集团公司第五十四研究所 | UQPSK signal demodulating device |
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