CN105842561B - A kind of background signal removing method for being suitable for live electromagnetic interference detection - Google Patents
A kind of background signal removing method for being suitable for live electromagnetic interference detection Download PDFInfo
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- CN105842561B CN105842561B CN201610183115.8A CN201610183115A CN105842561B CN 105842561 B CN105842561 B CN 105842561B CN 201610183115 A CN201610183115 A CN 201610183115A CN 105842561 B CN105842561 B CN 105842561B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/001—Measuring interference from external sources to, or emission from, the device under test, e.g. EMC, EMI, EMP or ESD testing
Abstract
The invention discloses a kind of background signal removing methods for being suitable for live electromagnetic interference detection, test can be completed using the easily-testing of portable frequency spectrum instrument and common antenna equipment, with the maximum ambient noise for keeping type collection interior for a period of time, then the Electromagnetic Launching of EUT and the mixed signal of environment are acquired when equipment under test is switched on, then the Electromagnetic Launching of EUT is obtained using frequency domain adaptive filtering algorithm.The present invention keeps the frequency spectrum datas such as type collection ambient noise, mixed signal using maximum, it is possible to reduce influence caused by ambient noise is unstable；The present invention obtains the frequency point of EUT Electromagnetic Launchings by after mixed signal and ambient noise input adaptive digital filter from output signal；Then, the range value of each frequency point of EUT Electromagnetic Launchings is obtained from mixed signal, the background noise of remaining frequency point spectrum analyzer is as the range value after elimination background signal.
Description
Technical field
The invention belongs to electromagnetic interference detection technique fields, and in particular to a kind of back of the body for being suitable for live electromagnetic interference detection
Scape signal clearing method.
Background technology
In order to avoid the influence of external environment, electromagnetic interference detection is usually carried out in microwave dark room or special open area test site.
But with the development of communication and the extension of mankind's activity, ideal open area test site has been difficult to find.And the cost in darkroom is very
Height, along with some tests are that the use site in equipment is needed to carry out, because some equipment are very big or need to set with other
It is standby to work together, if being done in darkroom, need and accompany test product accordingly.So now more and more people research how
Electromagnetic interference measurement, EMI measurement is carried out in the use site of equipment.However, the difficulty of in-site measurement maximum is exactly to eliminate ambient noise, eliminate
Ambient noise common practice has timesharing measurement and synchro measure.
Timesharing measurement is in same position, using general electromagnetic interference detection receiver or frequency spectrograph in test item
An ambient noise is surveyed when (Equipment under test, EUT) is closed, an EUT and background are then surveyed when EUT is opened
Noise emits jointly.It again will test result " subtracting each other " twice, you can offset ambient noise.Timesharing measurement needs ambient noise steady
It is fixed, but can there are various signals, such as frequency modulation broadcasting, mobile phone signal in common site environment.Synchro measure needs simultaneously
The mixed signal of ambient noise and EUT radiation signals is obtained, this method requirement uses two-channel receiver and the uniform back of the body
Scape noise, similarly, the either sky high cost of two-channel receiver or uniform noise circumstance are not easy in true environment
It is satisfied.
Invention content
The purpose of the present invention is to solve the above problems, propose a kind of background letter for being suitable for live electromagnetic interference detection
Number removing method.It is the test that can be completed using the easily-testing of portable frequency spectrum instrument and common antenna equipment, with maximum
Then the ambient noise for keeping type collection interior for a period of time acquires the Electromagnetic Launching and environment of EUT when equipment under test is switched on
Mixed signal, then using frequency domain adaptive filtering algorithm obtain EUT Electromagnetic Launching.
A kind of background signal removing method for being suitable for live electromagnetic interference detection, including following steps：
The first step：Reception antenna and spectrum analyzer are connected by radio-frequency cable, spectrum analyzer is set, is operated in it
Maximum holding pattern；
Second step：EUT is closed, spectrum analyzer is made to be in maximum holding pattern, the ambient noise of T1 times is acquired, obtains
Ambient noise E；
Third walks：EUT is opened, spectrum analyzer is made to be in maximum holding pattern, acquires the T1 times, obtains the electromagnetism of EUT
Transmitting and the mixed signal M of ambient noise；
4th step：The connection of radio-frequency cable and spectrum analyzer is disconnected, obtains the background noise N of spectrum analyzer；
5th step：Frequency f (n), background noise amplitude e_signal (n), mixed signal amplitude m_ are extracted from E, M, N
The background noise amplitude nosie (n) of signal (n) and spectrum analyzer；
6th step：Background noise amplitude e_signal (n) and mixed signal amplitude m_signal (n) is become from logarithmic coordinates
Linear coordinate is changed to, the unit of e_signal (n) and m_signal (n) becomes mw from dBm；
7th step：The background noise amplitude e_signal (n) of linear coordinate and mixed signal amplitude m_signal (n) is defeated
Enter to adaptive digital filter, obtain output signal y (n) and error signal e rror (n)；
8th step：Threshold value t0 is put in acquisition, if T is | y (n) | maximum value, threshold value t0 values are：
9th step：Mixed signal amplitude m_signal (n) is converted into logarithmic coordinates, m_signal (n) by linear coordinate
Unit dBm is become from mw；
Tenth step：Compare one by one | y (n) | and the size of t0, if | y (n) | more than or equal to t0, EUT_signal (n)=
m_signal(n)；If | y (n) | less than t0, EUT_signal (n)=noise (n)；
11st step：Be abscissa with frequency f (n), EUT_signal (n) be ordinate draw curve graph, be eliminated
The electromagnetic emission spectra figure of EUT after background signal.
The advantage of the invention is that：
(1) frequency spectrum datas such as type collection ambient noise, mixed signal are kept using maximum, it is possible to reduce ambient noise is not
Influence caused by stabilization；
(2) by after mixed signal and ambient noise input adaptive digital filter, EUT electromagnetism is obtained from output signal
The frequency point of transmitting；Then, the range value of each frequency point of EUT Electromagnetic Launchings, remaining frequency point spectrum analysis are obtained from mixed signal
The background noise of instrument is as the range value after eliminating background signal.No matter background signal range value is much, how wide frequency band is, should
Method can effectively eliminate；
(3) compared with prior art, used test equipment of the present invention is simple, at low cost.
Description of the drawings
Fig. 1 is to carry out Site Detection suitable for the background signal removing method of live electromagnetic interference detection using the present invention
Configuration diagram.
Fig. 2 is the adaptive digital filter for the background signal removing method that the present invention is suitable for live electromagnetic interference detection
Schematic diagram.
Fig. 3 is the schematic diagram of the ambient noise E containing background signal.
Fig. 4 is the schematic diagram of the Electromagnetic Launching of EUT and the mixed signal M of ambient noise.
Fig. 5 is is abscissa, adaptive digital filter output signal with frequency f (n) | y (n) | it is what ordinate was drawn
The schematic diagram of curve graph.
Fig. 6 is the electromagnetic emission spectra figure that EUT after background signal is eliminated using this method.
Fig. 7 is flow chart of the method for the present invention.
Specific embodiment
Below in conjunction with drawings and examples, the present invention is described in further detail.
The present invention is a kind of background signal removing method for being suitable for live electromagnetic interference detection, and flow is as shown in fig. 7, packet
Include following steps：
The first step：Reception antenna and spectrum analyzer are connected by radio-frequency cable, such as Fig. 1 sets spectrum analyzer, makes it
It is operated in maximum holding pattern；
Second step：EUT is closed, spectrum analyzer is made to be in maximum holding pattern, the ambient noise of T1 times is acquired, obtains
Metastable ambient noise E, such as Fig. 3；
Third walks：EUT is opened, spectrum analyzer is made to be in maximum holding pattern, acquires the T1 times, obtains the electromagnetism of EUT
Transmitting and the mixed signal M, such as Fig. 4 of ambient noise；
4th step：The connection of radio-frequency cable and spectrum analyzer is disconnected, obtains the background noise N of spectrum analyzer；
5th step：Frequency f (n), background noise amplitude e_signal (n), mixed signal amplitude m_ are extracted from E, M, N
The background noise amplitude nosie (n) of signal (n) and spectrum analyzer；
E, M, N are the data of two row multirows, and wherein first row is all frequency, and secondary series is amplitude.
6th step：Background noise amplitude e_signal (n) and mixed signal amplitude m_signal (n) is become from logarithmic coordinates
Linear coordinate is changed to, the unit of e_signal (n) and m_signal (n) becomes mw from dBm, specially：
Wherein, e_signal (mw) is the background noise amplitude after e_signal (n) units become mw from dBm, m_
Signal (mw) is the mixed signal amplitude after m_signal (n) units become mw from dBm.
7th step：As shown in Fig. 2, by the background noise amplitude e_signal (n) of linear coordinate and mixed signal amplitude m_
Signal (n) is input to adaptive digital filter, obtains output signal y (n) and error signal e rror (n)；
8th step：It is abscissa, adaptive digital filter output signal with frequency f (n) | y (n) | it is that ordinate is drawn
Curve graph, set threshold value t0, if T is | y (n) | maximum value, threshold value t0 obtaining value methods：
Threshold value is according to | y (n) | it is configured, as shown in figure 5, significantly there was only 9.1*10 in figure8This bin magnitudes value ratio
It is larger, then according to this range value size threshold value can be 1.3 × 10-6。
9th step：Mixed signal amplitude m_signal (n) is converted into logarithmic coordinates, m_signal (n) by linear coordinate
Unit dBm is become from mw, it is specific as follows；
M_signal (dBm)=10lg (m_signal (mw))
Wherein：M_signal (dBm) represents that m_signal (n) is converted to the mixed signal after logarithmic coordinates by linear coordinate
Amplitude.
Tenth step：Compare one by one | y (n) | and the size of t0, it determines to eliminate the amplitude output signal after background signal
EUT_signal (n), specific method are：
If | y (n) | more than or equal to t0, EUT_signal (n)=m_signal (n)；If | y (n) | less than t0,
EUT_signal (n)=noise (n)；
11st step：Be abscissa with frequency f (n), EUT_signal (n) be ordinate draw curve graph, be eliminated
The electromagnetic emission spectra figure of EUT after background signal, as shown in Figure 6.
Claims (3)
1. a kind of background signal removing method for being suitable for live electromagnetic interference detection, including following steps：
The first step：Reception antenna and spectrum analyzer are connected by radio-frequency cable, spectrum analyzer is set, it is made to be operated in maximum
Holding pattern；
Second step：EUT is closed, spectrum analyzer is made to be in maximum holding pattern, the ambient noise of T1 times is acquired, obtains background
Noise E；
Third walks：EUT is opened, spectrum analyzer is made to be in maximum holding pattern, acquires the T1 times, obtains the Electromagnetic Launching of EUT
With the mixed signal M of ambient noise；
4th step：The connection of radio-frequency cable and spectrum analyzer is disconnected, obtains the background noise N of spectrum analyzer；
5th step：Frequency f (n), background noise amplitude e_signal (n), mixed signal amplitude m_signal are extracted from E, M, N
(n) and the background noise amplitude nosie (n) of spectrum analyzer；
6th step：Background noise amplitude e_signal (n) and mixed signal amplitude m_signal (n) are transformed to from logarithmic coordinates
The unit of linear coordinate, e_signal (n) and m_signal (n) become mw from dBm；
7th step：The background noise amplitude e_signal (n) of linear coordinate and mixed signal amplitude m_signal (n) are input to
Adaptive digital filter obtains output signal y (n) and error signal e rror (n)；
8th step：Threshold value t0 is put in acquisition, if T is | y (n) | maximum value, threshold value t0 values are：
9th step：Mixed signal amplitude m_signal (n) is converted into logarithmic coordinates, the list of m_signal (n) by linear coordinate
Position becomes dBm from mw；
Tenth step：Compare one by one | y (n) | and the size of t0, if | y (n) | more than or equal to t0, EUT_signal (n)=m_
signal(n)；If | y (n) | less than t0, EUT_signal (n)=noise (n)；
11st step：Be abscissa with frequency f (n), EUT_signal (n) be ordinate draw curve graph, be eliminated background
The electromagnetic emission spectra figure of EUT after signal.
2. a kind of background signal removing method for being suitable for live electromagnetic interference detection according to claim 1, described
6th step, specially：
Wherein, e_signal (mw) is the background noise amplitude after e_signal (n) units become mw from dBm, m_signal
(mw) it is mixed signal amplitude after m_signal (n) units become mw from dBm.
3. a kind of background signal removing method for being suitable for live electromagnetic interference detection according to claim 1, described
9th step, specially：
M_signal (dBm)=10lg (m_signal (mw))
Wherein：M_signal (dBm) represents that m_signal (n) is converted to the mixed signal width after logarithmic coordinates by linear coordinate
Degree.
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| CN107871343A (en) * | 2016-09-28 | 2018-04-03 | 北京中科国技信息系统有限公司 | Electronic charging system without parking ETC detecting systems and method |
| CN108155959B (en) * | 2017-12-15 | 2020-09-29 | 成都爱科特科技发展有限公司 | Unmanned aerial vehicle measurement and control signal detection method under complex network environment |
| CN112162159A (en) * | 2020-09-08 | 2021-01-01 | 中电科仪器仪表有限公司 | Electromagnetic interference field test method based on signal identification |
| CN113541851B (en) * | 2021-07-20 | 2022-04-15 | 成都云溯新起点科技有限公司 | Steady-state broadband electromagnetic spectrum suppression method |
| CN113644997B (en) * | 2021-10-14 | 2022-01-21 | 中国民用航空总局第二研究所 | Electromagnetic environment detection method, device and system |
| CN114662540B (en) * | 2022-03-22 | 2024-02-27 | 重庆大学 | Noise elimination method for electromagnetic interference field test signal |
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