CN101820303A - Radiation noise test method applied to power line communication network - Google Patents

Abstract

The invention relates to a radiation noise test method applied to a power line communication network. The method comprises the following steps of: extracting a first noise voltage of a live wire to a grounding wire and a second noise voltage of a neutral wire to the grounding wire in the power line communication network through a linear impedance stabilizing network to obtain a conducted noise in the power line communication network; calculating a vector sum and a vector difference for the first noise voltage and the second noise voltage through a noise separation network to obtain a differential mode noise voltage and a common-mode noise voltage so as to separate a differential mode conducted noise voltage from a common-mode conducted noise voltage; dividing the common-mode noise voltage by 50 ohms to obtain a common-mode noise current; and obtaining a radiation noise electric field emitted to a free space according to the common-mode noise current. The conducted noise is separated into a common-mode noise and a differential mode noise to obtain the relation between the radiation noise and the common-mode noise current so as to simplify test equipment and reduce test cost.

Description

A kind of radiation noise test method that is applied to power line communication network

Technical field

The present invention relates to a kind of radiated noise method of estimating that is applied to power line communication network, belong to electromagnetic compatibility test and power line communication field.

Background technology

Power line communication network (Power Line Communication) is to utilize ZAP to transmit the network of information as transmission medium with power line.Adopt this technology, electric energy and high-frequency signal can be transmitted by same power line, need not to adopt dedicated communication line.And the current also unspecial electromagnetic radiation method of estimating at power line communication network, and the existing cost that adopts microwave dark room to measure electromagnetic radiation is higher, therefore how at the characteristics of power line communication network, developing a kind of radiated noise short-cut method of estimating that is applied to power line communication network is the problem that the present invention studies.

Summary of the invention

The object of the invention provides a kind of radiation noise test method that is applied to power line communication network, and this method is estimated the radiated noise of power line communication network by common mode noise current.

For achieving the above object, the technical solution used in the present invention is: a kind of radiated noise method of estimating that is applied to power line communication network, and its innovation is: may further comprise the steps:

Step 1: test conducted noise separated network in power line communication network in the radiated noise frequency range common mode insert loss and differential mode rejection ratio performance, to determine that this conducted noise separated network satisfies measurement requirement in the radiated noise frequency range;

Step 2: extract in the power line communication network live wire first noise voltage (V of line over the ground by linear impedance stabilization network (LISN) _L), zero line is to the second noise voltage (V of ground wire _N), to draw the conducted noise in this power line communication network;

Step 3: by noise separating network with the first noise voltage (V _L), the second noise voltage (V _N) carry out vector and with the phasor difference computing, obtain differential mode conducted noise voltage and common mode conducted noise voltage, with differential mode conducted noise in the discrete conductive noise and common mode conducted noise;

Concrete formula is as follows:

$\left|V_{\mathrm{DM}}\right|=\left|\frac{V_L-V_N}{2}\right|---\left(1\right)$

$\left|V_{\mathrm{CM}}\right|=\left|\frac{V_L+V_N}{2}\right|---\left(2\right)$

In the formula, V _LBe first noise voltage, V _NBe second noise voltage, V _DMBe differential mode conducted noise voltage, V _CMBe common mode conducted noise voltage;

Step 4: with described common mode conducted noise voltage (V _CM) obtain common mode noise current divided by 50 ohm:

$i_{\mathrm{cm}}=\frac{V_{\mathrm{CM}}}{50};$

Step 5: pass through formula according to described common mode noise current:

$E_{\mathrm{\θ}}\≈j\frac{l{Z}_{0}I{\mathrm{\β}}_0\sin \mathrm{\θ}}{4\mathrm{\πr}}{e}^{-j{\mathrm{\β}}_{0}r}---\left(3\right)$

, obtain to launch the radiated noise electric field to free space, in the formula, Z ₀Be the free space wave impedance, unit is Ω; L is a conductor length, and unit is m; I is an electric current, and unit is A; R is a measuring distance, and unit is m; β ₀Be 2 π/λ, wherein λ is the correlated frequency signal wavelength, and unit is m; E _θBe the radiated noise electric field, unit is dBuV/m; J is the imaginary part sign; θ is for measuring vector angle.

Related content in the technique scheme is explained as follows:

1, in the such scheme, it be the conducted noise separated network in operating frequency is performance more than the 30MHz that described common mode is inserted loss and differential mode rejection ratio performance.

2, in the such scheme, described conducted noise shows by spectrum analyzer and analyzes.

Because the technique scheme utilization, the present invention compared with prior art has following advantage and effect:

1, the present invention analyzes the mechanism that radiated noise in the power line communication network produces, and it is separated into common-mode noise and differential mode noise, draws the relation of this radiated noise and common mode noise current, the testing equipment of simplification, thus reduced testing cost.

2, the present invention inserts loss and differential mode rejection ratio performance with the common mode that noise separating network is applied to testing radiation noise frequency range in the power line communication network, to determine its high frequency radiation frequency range performance more than 30MHz, guarantee that noise separating network can be used in the higher occasion of frequency range.

3, the present invention extracts conducted noise in the power line communication network by linear impedance stabilization network (LISN), extracting common mode noise current by noise separating network, can save great number measurement expense such as utilizing microwave dark room measures for radiated noise, thereby the testing equipment of simplifying has reduced testing cost.

4, the present invention designs noise suppressed measures such as respective filter and ferrite bead and suppresses conducted noise in the power line communication network and make power line communication network partly reach standard-required in the conduction common-mode noise.

Description of drawings

Accompanying drawing 1 produces schematic diagram for radiated noise;

Accompanying drawing 2 is a conduction common mode noise current extraction element schematic diagram in the power line communication network;

Accompanying drawing 3 is estimated schematic diagram for the radio-frequency current probe;

Accompanying drawing 4 is the schematic diagram that comprises the power line communication network test macro of filter;

Accompanying drawing 5 is a near-field thermal radiation noise testing experimental provision;

Accompanying drawing 6 is for to utilize ferrite bead to carry out porting principle figure for the radiated noise of electric line communication system;

Accompanying drawing 7 is a conducted noise separated network performance test experimental provision;

Accompanying drawing 8 is conducted noise separated network results of property under the radiation frequency range;

Accompanying drawing 9 is to add in the power line communication network of filter front and back to conduct the common-mode noise frequency spectrum, wherein, is that common mode conducted noise (b) is a common mode conducted noise behind the adding filter before the adding filter (a);

Accompanying drawing 10 is a radiated noise frequency spectrum in the electric line communication system of adding filter front and back, wherein, is that adding filter previous irradiation noise signal (b) is a radiated noise signals behind the adding filter (a);

Accompanying drawing 11 is based on radiated noise signals frequency spectrum before and after the Field probe measurement adding ferrite bead, wherein, is that adding ferrite bead previous irradiation noise signal (b) is a radiated noise signals behind the adding ferrite bead (a).

Embodiment

Below in conjunction with drawings and Examples the present invention is further described:

Embodiment: a kind of radiation noise test method that is applied to power line communication network

A kind of radiation noise test method that is applied to power line communication network may further comprise the steps:

Step 1: test conducted noise separated network in power line communication network in the radiated noise frequency range common mode insert loss and differential mode rejection ratio performance, to determine that this conducted noise separated network satisfies measurement requirement in the radiated noise frequency range; It is the conducted noise separated network in operating frequency is performance more than the 30MHz that described common mode is inserted loss and differential mode rejection ratio performance;

Step 2: extract in the power line communication network live wire first noise voltage (V of line over the ground by linear impedance stabilization network (LISN) _L), zero line is to the second noise voltage (V of ground wire _N), to draw the conducted noise in this power line communication network, described conducted noise shows by spectrum analyzer and analyzes;

Step 3: by noise separating network with the first noise voltage (V _L), the second noise voltage (V _N) carry out vector and with the phasor difference computing, obtain differential mode conducted noise voltage and common mode conducted noise voltage, with differential mode conducted noise in the discrete conductive noise and common mode conducted noise;

Concrete formula is as follows:

$\left|V_{\mathrm{DM}}\right|=\left|\frac{V_L-V_N}{2}\right|---\left(1\right)$

$\left|V_{\mathrm{CM}}\right|=\left|\frac{V_L+V_N}{2}\right|---\left(2\right)$

In the formula, V _LBe first noise voltage, V _NBe second noise voltage, V _DMBe differential mode conducted noise voltage, V _CMBe common mode conducted noise voltage;

Step 4: with described common mode conducted noise voltage (V _CM) obtain common mode noise current divided by 50 ohm:

$i_{\mathrm{cm}}=\frac{V_{\mathrm{CM}}}{50};$

Step 5: pass through formula according to described common mode noise current:

$E_{\mathrm{\θ}}\≈j\frac{l{Z}_{0}I{\mathrm{\β}}_0\sin \mathrm{\θ}}{4\mathrm{\πr}}{e}^{-j{\mathrm{\β}}_{0}r}---\left(3\right)$

, obtain to launch the radiated noise electric field to free space, in the formula, Z ₀Be the free space wave impedance, unit is Ω; L is a conductor length, and unit is m; I is an electric current, and unit is A; R is a measuring distance, and unit is m; β ₀Be 2 π/λ, wherein λ is the correlated frequency signal wavelength, and unit is m; E _θBe the radiated noise electric field, unit is dBuV/m; J is the imaginary part sign; θ is for measuring vector angle.

Along with the increase of frequency, the physical length of lead will be comparable with the physical dimension of wavelength, then along the uniformity no longer of the CURRENT DISTRIBUTION on the lead.Lead evenly can be divided into N segment for this reason, adopt the radio-frequency current probe to measure its electric current (seeing accompanying drawing 3) separately, establish and be respectively I1, I2 in the centre position of every segment ... In can adopt formula (3) to calculate for each section lead.

Adopt formula (3) to calculate the radiation field of each segment.Because open test site OATS normally measures the standard place of electromagnetic radiation, so need to consider the ground return effect, then total equivalent computation of radiation field is converted into as the formula (4).

$\left|E_c\right|\&ap;\frac{2\mathrm{\&pi;f}\&times;{10}^{-7}F({\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HSA00000005935700021.png"\; state="\{\{state\}\}">I</figure-callout>}}_1+I_2+...+I_n)l}{3\sqrt{r^2+{(H-0.8)}^2}}---\left(4\right)$

Wherein, | E _C| be radiated electric field, l is every segment equivalent aerial length, and f represents test frequency, and r represents open test site standard testing distance, and H represents the test antenna height, and F is for calculating the modifying factor under the test environment of open test site.

Present embodiment foregoing specific explanations is as follows.

With accompanying drawing 2 is the circuit connection diagram of experiment test system, and accompanying drawing 4 is the catenation principle figure behind the adding filter.The conductibility electromagnetic interference measurement, EMI measurement equipment of regulation has linear impedance stabilization network LISN (Line Impedance Stabilization Network is called for short LISN) and spectrum analyzer in the world at present.

The linear impedance network is called artificial mains network or source impedance stabilizing network again, is important electromagnetic compatibility test equipment.This network can effectively shield from the High-frequency Interference of external electrical network or stop the High-frequency Interference of load generation to import external electrical network into by supply socket, the power current (as domestic 50Hz electric current) that is provided under the load operate as normal is not provided again simultaneously, and the impedance of 50 stable Ω is provided to equipment under test in radio-frequency region, then interference voltage is transferred on the spectrum analyzer.

Spectrum analyzer be a kind of can frequency domain measurement system noise frequency spectrum instrument, this instrument can be directly shows measured noise signal in frequency domain, make the noiseproof feature that can more comprehensively analyze electric line communication system.

Concrete method of testing at first, is measured in the performance of radiation frequency range for the noise separating network that is adopted, and can apply in the middle of the estimating of radiated noise to determine this noise separating network.Judge that the good and bad leading indicator of common-mode noise separated network performance is that its common mode is inserted loss CMIL and its definition of differential mode rejection ratio DMRR as the formula (5):

$\mathrm{CMIL}=20\lg \left(\frac{V_{\mathrm{OC}}}{V_{\mathrm{CM}}}\right)$ $\mathrm{DMRR}=20\lg \left(\frac{V_{\mathrm{OC}}}{V_{\mathrm{DM}}}\right)---\left(5\right)$

Wherein, V _CMBe common mode input, V _OCBe common mode output; V _DMBe difference-mode input, V _ODBe differential mode output.In the common mode separated network, the ideal value that common mode is inserted loss should be 0, to guarantee that the loss of its common mode noise signal is less in the common-mode noise transmission; In like manner as can be known, its differential mode rejection ratio should be big as far as possible, can not be coupled in the transmission of common mode noise signal to guarantee its differential mode noise, so the ideal value of its differential mode rejection ratio should be-∞.Common-mode noise for this power line communication network is partly carried out performance test, sets up test trial assembly in fact and puts as shown in Figure 7, by test, can obtain its common mode insertion loss and differential mode rejection ratio test result as shown in Figure 8.This result shows that the radiation frequency range that this separated network can apply to power line communication network estimates.

Testing the conducted noise separated network on the basis of radiation frequency range performance, can the connecting circuit system.Power line communication network is connected with linear impedance stabilization network, and VL, the VN output port of the noise in the power line communication network via linear impedance stabilization network be linked in the conducted noise separated network, with in the noise input spectrum analyzer after separating to analyze the common mode noise current of power line communication network.For this experiment porch, need provide concrete experimental bench design objective according to standard according to the GB standard.For the power line communication network test macro, adopt the test of desktop ornaments, desktop conductibility disturbed test experiment place (seeing accompanying drawing 2) according to defined in the measurement standard, on the level ground and vertical wall of test site, must spread the grounding plate of area, provide shield effectiveness to reduce electromagnetic interference greater than 2m * 2m.On the horizontal metal plate, place the non-conductive material desk (2 * 1.5 * 0.8) of high a 80～90cm, again equipment under test EUT and load thereof are placed on the table, both are at a distance of 10cm and apart from vertical metal plate 40cm, power supply is supplied with by power line communication network via LISN, the high-frequency noise that it produced (60MHz～100MHz) transfer on the LISN, obtain its common-mode noise part by noise separating network again, transfer to the spectrum analyzer measurement then, the cable of equipment under test can be put by the requirement of institute's establishing criteria, more than is minimum test environment requirement.

Obtain to estimate for the radiated noise of electric line communication system according to formula (3), (4) after the common mode noise current.And design corresponding common-mode filter in the line to suppress the common-mode noise in the electric line communication system.Must design according to the spectrogram and the needed inhibition decibels of its common-mode noise during the design of common-mode noise frequency spectrum.

With designed common-mode filter according in the connected mode place in circuit shown in the experiment catenation principle figure of Fig. 4, this electric line communication system inserts filter and suppresses the front and back conducted noise as shown in Figure 9, by accompanying drawing 9 (a) as can be seen at 60MHz in this frequency band of 100MHz, before adding filter, its common-mode noise can reach about 60dBuV, and behind the adding filter, noise in this frequency range can well maintain below the 30dBuV, as accompanying drawing 9 (b), showing that this filter reaches for the common-mode noise in the power line communication network suppresses effect preferably.

Adopt near field probes to measure for the radiated noise size that suppresses common-mode noise front and back electric line communication system, its experimental system is seen Fig. 5, for this radiated noise experimental bench, should satisfy the long 150cm of table top, wide 70cm, high 50cm, the high 100cm of support, probe is fixed in frame bottom, can be at 120 * 50 * 100cm ³Move freely in the space.Experimental bench is all made with timber, all adopts gluing between timber and the timber, does not use any metal material, to avoid reflection of electromagnetic wave and absorption.Four independent power socket are arranged on the table top, can give spectrum analyzer, circuit-under-test and stand-by equipment power supply respectively.

Measure electric line communication system its near-field thermal radiation noise when not inserting filter and when inserting filter, it the results are shown in Figure 10.As can be seen, before not adding filter, radiated noise reaches nearly 60dBuV/m in the circuit, and after adding filter, owing to suppress the common-mode noise in the circuit, thereby has reduced the common mode current in the circuit, makes that its corresponding radiated noise is also corresponding to reduce.Make its radiated noise in whole frequency, all be not more than 40dBuV/m.

At last, this method is compared with traditional inhibition method, what conventional method adopted is to load ferrite bead on power line, to reach the purpose that suppresses radiated noise.

Utilize microwave dark room, directly measure the radiated noise of electric line communication system.Secondly, load ferrite bead on transmission line, in order to suppress the radiated noise of electric line communication system, the radiated noise of this system detects again behind the ferrite bead for loading to utilize microwave dark room.Its measurement result is seen Figure 11.As seen from Figure 11, in the experiment that the radiated noise that adopts ferrite bead for power line communication network suppresses, before adding ferrite bead, radiated noise maximum in the circuit can reach 60dBuV/m, after adding ferrite bead in the line, the radiated noise of power line communication network all is lower than 35dBuV/m, simultaneously, contrast Figure 10 and Figure 11 are as can be seen, in the band limits of 60MHz～100MHz, filter approximately can suppress about 20dBuV/m for radiated noise, and adopts ferrite bead to be about 21dBuV/m for the inhibition of radiated noise.This shows,, can estimate its radiated noise comparatively accurately when working by extracting its common mode noise current for the radiated noise that power line communication network produces.

By above-mentioned experiment as seen, for the power line communication system radiated noise estimate with the process that suppresses in, can be by the relation of its common mode current and radiation field, obtain common-mode voltage noise in the circuit thereby extract for overall noise in the circuit.Estimate its radiated noise after common-battery pressing mold noise is converted into the common mode current noise.And can suppress for estimating the radiated noise that obtains by filter and ferrite bead.Experimental result proves that this method is practical.

The foregoing description only is explanation technical conceive of the present invention and characteristics, and its purpose is to allow the personage who is familiar with this technology can understand content of the present invention and enforcement according to this, can not limit protection scope of the present invention with this.All equivalences that spirit is done according to the present invention change or modify, and all should be encompassed within protection scope of the present invention.

Claims (3)

1. radiation noise test method that is applied to power line communication network is characterized in that: may further comprise the steps:

Step 1: test conducted noise separated network common mode in the radiated noise frequency range is inserted the performance of loss and differential mode rejection ratio, to determine that this conducted noise separated network satisfies measurement requirement in the radiated noise frequency range;

Step 2: extract in the power line communication network live wire first noise voltage (V of line over the ground by linear impedance stabilization network (LISN) _L), zero line is to the second noise voltage (V of ground wire _N), to draw the conducted noise in this power line communication network;

Step 3: by noise separating network with the first noise voltage (V _L), the second noise voltage (V _N) carry out vector and with the phasor difference computing, obtain differential mode conducted noise voltage and common mode conducted noise voltage, with differential mode conducted noise in the discrete conductive noise and common mode conducted noise;

Concrete formula is as follows:

$\left|V_{\mathrm{DM}}\right|=\left|\frac{V_L-V_N}{2}\right|---\left(1\right)$

$\left|V_{\mathrm{CM}}\right|=\left|\frac{V_L+V_N}{2}\right|---\left(2\right)$

In the formula, V _LBe first noise voltage, V _NBe second noise voltage, V _DMBe differential mode conducted noise voltage, V _CMBe common mode conducted noise voltage;

Step 4: with described common mode conducted noise voltage (V _CM) obtain common mode noise current divided by 50 ohm:

$;i_{\mathrm{cm}}=\frac{V_{\mathrm{CM}}}{50}$

Step 5: pass through formula according to described common mode noise current:

$E_{\mathrm{\&theta;}}\&ap;j\frac{{\mathrm{lZ}}_0{\mathrm{I\&beta;}}_0\sin \mathrm{\&theta;}}{4\mathrm{\&pi;r}}{e}^{-j{\mathrm{\&beta;}}_{0}r}---\left(3\right)$

, obtain to launch the radiated noise electric field to free space, in the formula, Z ₀Be the free space wave impedance, unit is Ω; L is a conductor length, and unit is m; I is an electric current, and unit is A; R is a measuring distance, and unit is m; β ₀Be 2 π/λ, wherein λ is the correlated frequency signal wavelength, and unit is m; E _θBe the radiated noise electric field, unit is dBuV/m; J is the imaginary part sign; θ is for measuring vector angle.

2. method according to claim 1 is characterized in that: it be the conducted noise separated network in operating frequency is performance more than the 30MHz that described common mode is inserted loss and differential mode rejection ratio performance.

3. method according to claim 1 is characterized in that: described conducted noise shows by spectrum analyzer and analyzes.

Images