CN102854400A - Method and device for acquiring specific absorption rate of electromagnetic waves - Google Patents

Abstract

The invention discloses a method and a device for acquiring specific absorption rate of electromagnetic waves. The method includes the steps of establishing a near-field reference plane S of a mobile terminal MIMO (multiple input multiple output) antenna in a free space, and computing electromagnetic field of the mobile terminal MIMO antenna on the reference plane S; utilizing the electromagnetic field equivalence principle to acquire frequency domain equivalent surface magnetic current (formula) on the near-field reference plane S; on the basis of the frequency domain equivalent surface magnetic current on the near-field reference plane S and electromagnetic interaction between the equivalent surface magnetic current and the human body model, computing electric field distribution inside a human body model, and acquiring a SAR (specific absorption rate) value corresponding to the electric field distribution. By decomposing jointed electromagnetism simulation of a data card, an antenna and a human body organization into the electromagnetism simulation of the data card and the antenna and the electromagnetism simulation of magnetic current motivated human body organization, and accordingly a standardized model for SAR simulation of the mobile terminal MIMO antenna is provided, and reliability and capability of being standardized of a SAR evaluation model are guaranteed.

Description

A kind of method and device that obtains the electromagnetic wave specific absorption rate

Technical field

The present invention relates to multiple-input and multiple-output (MIMO) antenna equipment Equivalent Modeling technology, relate in particular to a kind of method and device that obtains the electromagnetic wave specific absorption rate.

Background technology

The Wireless Telecom Equipments such as MIMO antenna and portable terminal (such as the cellular radio card of surfing Internet) are integrated, can satisfy the growing mobile communication needs of people.But the electromagnetic radiation energy that portable terminal when work produces can be absorbed by the body, and the electromagnetic energy of absorption of human body can work the mischief to health when excessive.

For quantitatively characterizing absorption of human body electromagnetic energy what, introduced electromagnetic wave specific absorption rate (SAR, Specific Absorption Rate) parameter.The SAR parameter-definition is the electromagnetic power that tissue absorbed or consumed of unit mass.The SAR value has now become an important indicator weighing the wireless electronic product quality, and formed SAR parameter series standard, such as, SAR testing standard (IEC 62209-2 Ed.1) and IEEE that International Electrotechnical Commission (IEC) formulates are formulating SAR simulation standard (IEEE P528.3/D3.0) etc., to overcome existing model fineness not and the limitation of test consistance deficiency.

According to above-mentioned standard, when MIMO antenna and portable terminal were in normal operating conditions, available probe test or emulation technology obtained being arranged in the electric field value of above-mentioned MIMO antenna near-field district each test point of test container, then according to formula S AR=0.5 σ | and E| ²/ ρ calculates the SAR value.Wherein, σ is the tissue fluid conductivity, and ρ is tissue fluid density, and E is institute's measuring point electric field value.

By above-mentioned SAR parameter-definition as can be known, the SAR parameter is a near field derived parameter.Therefore, the SAR characteristic of quantitatively characterizing portable terminal MIMO antenna, must its near-field thermal radiation characteristic of quantitative examination, to obtain its near-field thermal radiation model.Existing studies show that: the near-field thermal radiation model of portable terminal MIMO antenna equipment is the environmental factor of the most critical of SAR emulation success or failure, and reason is that fineness and the versatility of near-field thermal radiation model is very big for efficient and the Accuracy of whole SAR parameters simulation.

Yet, real portable terminal MIMO antenna, often have the high and poor characteristics of versatility of complexity, these characteristics have determined to adopt true portable terminal MIMO antenna equipment as standardized SAR assessment models, and need to carry out credible abstract and simplification to it, formation takes into account the credible SAR assessment models of versatility, modeling efficiency and cost three aspect factor, wherein, accurate MIMO antenna equipment equivalent modeling method is to guarantee that its SAR assessment models is credible and one of can standardized condition precedent.

In the SAR realistic model of present IEEE, also there is not the SAR simulation standard model of portable terminal MIMO antenna equipment.

Summary of the invention

In view of this, fundamental purpose of the present invention is to provide a kind of method and device that obtains the electromagnetic wave specific absorption rate, and the SAR simulation standard model of portable terminal MIMO antenna equipment can be provided, but guarantees the credible and standardization of SAR assessment models.

For achieving the above object, technical scheme of the present invention is achieved in that

A kind of method of obtaining the electromagnetic wave specific absorption rate comprises,

Set up portable terminal multiple-input and multiple-output MIMO antenna at the near field of free space reference surface S, calculate the electromagnetic field of portable terminal MIMO antenna on this reference surface S;

On described near field reference surface S, adopt the electromagnetic field equivalence principle to obtain frequency domain equivalent face magnetic current $J_{\mathrm{ms}}\left({\stackrel{\→}{r}}_{\mathrm{ms}}\right);$

Based on the equivalent face magnetic current on the described near field reference surface S Calculate the Electric Field Distribution of manikin inside, and obtain electromagnetic wave specific absorption rate SAR value corresponding to Electric Field Distribution.

The described portable terminal MIMO antenna of setting up calculates the electromagnetic field of portable terminal MIMO antenna on this reference surface S and specifically comprises at the near field of free space reference surface S:

Based on the three-D space structure model of described portable terminal MIMO antenna, described portable terminal MIMO antenna is not contained the Electromagnetic Modeling of tissue; Wherein, comprise definite described MIMO antenna material electromagnetic parameter, electric magnetization source parameter and boundary condition;

Obtain the described near field electricity that does not contain the portable terminal MIMO antenna of tissue by numerical evaluation $E\left[\left({\stackrel{\→}{r}}_{\mathrm{ms}}\right)\right].$

Described near field reference surface S is the area of space between described portable terminal MIMO antenna and tissue model, and the outer normal direction of described near field reference surface S is away from the MIMO antenna direction;

The described frequency domain equivalent face magnetic current that obtains Comprise: according to following formula, draw the lip-deep frequency domain equivalent face of described near field reference surface S magnetic current J _Ms:

Wherein, near field electromagnetic information With frequency domain equivalent face magnetic current

Electric field, magnetic current complex values had both been comprised

Comprise again this electric field, locus coordinate that magnetic current is corresponding

Also comprise before the method: according to following formula, with the real space coordinate

Be converted into the indexed coordinates that electromagnetic calculation needs:

Wherein, Δ x, Δ y and Δ z are respectively x, the spatial spreading unit of y and z direction, With

Be respectively x, the mikey vector of y and z direction.I, j and k are the indexed coordinates that electromagnetic calculation needs.

The described Electric Field Distribution that calculates manikin inside, and obtain SAR value corresponding to Electric Field Distribution and comprise:

Read in described frequency domain equivalent face magnetic current, be translated into time domain space distribution source;

With the time domain source space Distribution Value assignment that obtains to the near field with reference on site, space corresponding to S face;

Put into good conductor in the non-place of finding the solution, to guarantee this regional electromagnetic field as null field, the good conductor frequency domain equivalent face magnetic current of introducing

To produce telescope direct image planes magnetic current source, the equivalent face magnetic current source of finding the solution the place is 2 times that put into before the good conductor, is specially

By

Calculate externally driving source of tissue model

The Electric Field Distribution of inside under the incentive condition is utilized the SAR definition to calculate inside of human body SAR value and is distributed;

The non-place of finding the solution is null field.

The method also comprises: with the described SAR value distributed data of the inner additional space of the tissue model that obtains position, utilize 3 dimension figure show tools to show, obtain 3 of the inner SAR of manikin and tie up distribution plans.

A kind of device that obtains the electromagnetic wave specific absorption rate, the first acquisition module, the first computing module, the second computing module, and SAR acquisition module, wherein,

The first acquisition module is used for setting up portable terminal MIMO antenna at the near field of free space reference surface S;

The first computing module is used for calculating the electromagnetic field of portable terminal MIMO antenna on this reference surface S;

The second computing module is used for adopting the electromagnetic field equivalence principle, on the near field reference surface S that the first acquisition module obtains, obtains frequency domain equivalent face magnetic current

The SAR acquisition module is used for based on the equivalent face magnetic current on the reference surface S

This equivalent face magnetic current With the electromagnetic interaction of manikin, calculate the Electric Field Distribution of manikin inside, and obtain SAR value corresponding to Electric Field Distribution.

Can find out from the technical scheme that the invention described above provides, comprise and set up portable terminal MIMO antenna at the near field of free space reference surface S, calculate the electromagnetic field of portable terminal MIMO antenna on this reference surface S; Adopt the electromagnetic field equivalence principle, on described near field reference surface S, obtain frequency domain equivalent face magnetic current

Based on the equivalent face magnetic current on the reference surface S

This equivalent face magnetic current

With the electromagnetic interaction of manikin, calculate the Electric Field Distribution of manikin inside, and obtain SAR value corresponding to Electric Field Distribution.By the associating Electromagnetic Simulation problem of the present invention with data card, antenna and this three of tissue, be decomposed into the Electromagnetic Simulation of data card and antenna, and face magnetic current source forcing tissue Electromagnetic Simulation two parts; Then based on the electromagnetic field equivalence principle, by the equivalent face magnetic current on the reference surface, set up above-mentioned two-part contact, thereby consisted of unified Electromagnetic Simulation model.Because the equivalent face electromagnetic current that the Electromagnetic Simulation of data card and antenna obtains, the concrete structure that does not relate to data card and antenna, namely be applicable to all antenna structures, therefore, the present invention provides standardized model for the SAR emulation of portable terminal MIMO antenna equipment, but has guaranteed the credible and standardization of SAR assessment models.

Description of drawings

Fig. 1 is the process flow diagram that the present invention obtains the method for SAR;

Fig. 2 is notebook computer of the present invention, data card antenna and tissue geometric model (size, relative space position) and electromagnetic model (dielectric constant of medium material, conductivity, magnetic permeability) synoptic diagram;

Fig. 3 is data card antenna of the present invention, tissue and equivalent reference surface S synoptic diagram, and wherein the equivalent face magnetic current is on the S face;

Fig. 4 is the composition structural representation of the present invention's device of obtaining SAR.

Embodiment

Fig. 1 is the process flow diagram that the present invention obtains the method for SAR, as shown in Figure 1, may further comprise the steps:

Step 100: set up portable terminal MIMO antenna at the near field of free space reference surface S, calculate the electromagnetic field of portable terminal MIMO antenna on this reference surface S.

The detailed process of this step is: the three-D space structure model of movement-based terminal MIMO antenna at first, adopt Electromagnetic Simulation software that portable terminal MIMO antenna is carried out accurate Electromagnetic Modeling (not containing tissue), comprise and determine above-mentioned MIMO antenna material electromagnetic parameter, electric magnetization source parameter and boundary condition etc.; Secondly, employing Numerical Calculation of Electromagnetic Fields method is carried out numerical evaluation to above-mentioned model and is obtained the above-mentioned near field electricity that does not contain the portable terminal MIMO antenna of tissue When it is emphasized that this step Electromagnetic Modeling, the three-D space structure of portable terminal need to be considered as the part of portable terminal MIMO antenna.

What this step was emphasized is when portable terminal MIMO antenna is carried out accurate Electromagnetic Modeling, to be not comprise tissue.The near field electricity of concrete how to confirm above-mentioned parameter and calculating portable terminal MIMO antenna

Can adopt existing a lot of method to realize, belong to those skilled in the art's conventional techniques means, be not intended to limit the scope of the invention, no longer describe in detail here.

Step 101: adopt the electromagnetic field equivalence principle, on the reference surface S of the described near field of step 100, obtain frequency domain equivalent face magnetic current

The detailed process of this step is: the described near field of step 100 reference surface S is the area of space between portable terminal MIMO antenna and tissue model, the outer normal direction of this near field reference surface S is n (away from the MIMO antenna direction), the near field electromagnetic information that calculates based on step 100

In conjunction with following formula (1), draw the lip-deep frequency domain equivalent face of described near field reference surface S magnetic current J _Ms(comprising phase place and amplitude):

$J_{\mathrm{ms}}\left({\stackrel{\→}{r}}_{\mathrm{ms}}\right)=-n\×E\left[\left({\stackrel{\→}{r}}_{\mathrm{ms}}\right)\right]---\left(1\right)$

In formula (1), near field electromagnetic information

With frequency domain equivalent face magnetic current

Electric field, magnetic current complex values had both been comprised

Comprise again this electric field, locus coordinate that magnetic current is corresponding

It is emphasized that the locus coordinate time in processing formula (1), need to be with the real space coordinate

Be converted into the indexed coordinates (integer type) that electromagnetic calculation needs, change according to formula (2):

${\stackrel{\→}{r}}_{\mathrm{ms}}=\hat{x}\·\mathrm{i\Δx}+\hat{y}\·\mathrm{j\Δy}+\hat{z}\·\mathrm{k\Δz}---\left(2\right)$

In the formula (2), Δ x, Δ y and Δ z are respectively x, the spatial spreading unit of y and z direction,

With

Be respectively x, the mikey vector of y and z direction.I, j and k are the indexed coordinates (integer type) that electromagnetic calculation needs.

Fig. 2 is notebook computer of the present invention, data card antenna and tissue geometric model (size, relative space position) and electromagnetic model (dielectric constant of medium material, conductivity, magnetic permeability) synoptic diagram; Fig. 3 is data card antenna of the present invention, tissue and equivalent reference surface S synoptic diagram, and wherein the equivalent face magnetic current is on the S face.

Step 102: based on the equivalent face magnetic current on the reference surface S

This equivalent face magnetic current

The electromagnetic field that produces and the electromagnetic interaction between the manikin, calculate the Electric Field Distribution of tissue inside (seeing accompanying drawing 2), and then obtain the corresponding SAR value of Electric Field Distribution of tissue inside (seeing accompanying drawing 2), comprise SAR Distribution Value and SAR peak value.

The detailed process of this step is: the frequency domain equivalent face magnetic current J that at first reads in step 101 gained _Ms, then be translated into time domain space distribution source, with this time domain source space Distribution Value assignment to the near field with reference on site, space corresponding to S face.Owing to finding the solution the area of space that the place is described time domain source sensing scatterer, other area of space (being that the area of space away from scatterer is pointed in the time domain source) is the non-place of finding the solution, non-electromagnetic field of finding the solution the place needn't calculate, it wherein can be any, in order to analyze simplification, the non-place of finding the solution of hypothesis is null field (being electric field E=0) in the present embodiment, thereby obtain non-place and the field Equivalent Boundary condition of finding the solution the border, place found the solution, for this reason, adopt the electromagnetism equivalence principle to set up the equivalent source on this border, its process is: put into good conductor in the non-place of finding the solution, to guarantee this regional electromagnetic field as null field, the good conductor of introducing is to equivalent face magnetic current J _MsTo produce telescope direct image planes magnetic current source, the equivalent face magnetic current source of finding the solution the place is original (before putting into good conductor) 2 times, namely

And the equivalent face current source is 0 (negative mirror image surface current and equivalent face current canceling).Will

The substitution magnetic field integral equation calculates externally driving source of tissue model

The Electric Field Distribution of inside under the incentive condition is utilized the SAR definition to calculate inside of human body SAR value and is distributed.

Based on step 102, SAR value distributed data with the inner additional space of the tissue model that obtains position, (tie up graph function such as Matlab3 with 3 dimension figure show tools, specific implementation belongs to those skilled in the art's conventional techniques means, here repeat no more) show, obtain the 3 dimension distribution plans of the inner SAR of manikin, this just provides general a, assessment models intuitively for portable terminal MIMO Antenna Design.

Table 1 is data card antenna SAR maximal value and position thereof, as shown in table 1, provided the SAR simulation value contrast of 3 kinds of different pieces of information card antenna full wave models (CST software emulation) with analytical model of the present invention, can find out, no matter be the distribution SAR value of peak value SAR or XOY plane, analytical model SAR value of the present invention and full-wave simulation SAR value are all coincide fine.Full-wave simulation SAR value is by the verification experimental verification mistake, and its precision and accuracy are credible.Therefore, table 1 has been verified the validity of analytical model SAR emulation of the present invention.To sum up, except rectangular parallelepiped 1 height change, model changes and causes that the variation of data card MIMO antenna SAR value peak value is no more than 3.5%, can be similar to and think that the SAR characteristic is constant.

Table 1

Table 2 is data card antenna SAR simulation time, as shown in table 2, the simulation time that has needed when having provided the SAR emulation of 3 kinds of different pieces of information card antenna full wave models (CST software emulation) and analytical model of the present invention, as seen the SAR emulation of analytical model, compare full wave model, effectively reduced the SAR simulation time.

Table 2

In the inventive method, at first with data card, antenna and this three's of tissue associating Electromagnetic Simulation problem, be decomposed into two parts, that is: the Electromagnetic Simulation of (1) data card and antenna; (2) face magnetic current source forcing tissue Electromagnetic Simulation; Then based on the electromagnetic field equivalence principle, by the equivalent face magnetic current on the reference surface, set up the contact of above-mentioned 2 sub-problems, thereby consisted of unified Electromagnetic Simulation model.Because the equivalent face electromagnetic current that (1) obtains, the concrete structure that does not relate to data card and antenna namely is applicable to all antenna structures, therefore, this model provides standardized model for the SAR emulation of portable terminal MIMO antenna equipment, but has guaranteed the credible and standardization of SAR assessment models.

Also provide the device of a kind of SAR of obtaining for the inventive method, it forms structural representation as shown in Figure 4, mainly comprises the first acquisition module, the first computing module, the second computing module, and the SAR acquisition module, wherein,

The first acquisition module is used for setting up portable terminal MIMO antenna at the near field of free space reference surface S;

The first computing module is used for calculating the electromagnetic field of portable terminal MIMO antenna on this reference surface S;

The second computing module is used for adopting the electromagnetic field equivalence principle, on the near field reference surface S that the first acquisition module obtains, obtains frequency domain equivalent face magnetic current

The SAR acquisition module is used for based on the equivalent face magnetic current on the reference surface S

This equivalent face magnetic current

With the electromagnetic interaction of manikin, calculate the Electric Field Distribution of manikin inside, and obtain SAR value corresponding to Electric Field Distribution.

The above is preferred embodiment of the present invention only, is not for limiting protection scope of the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (7)

1. a method of obtaining the electromagnetic wave specific absorption rate is characterized in that, comprise,

Set up portable terminal multiple-input and multiple-output MIMO antenna at the near field of free space reference surface S, calculate the electromagnetic field of portable terminal MIMO antenna on this reference surface S;

On described near field reference surface S, adopt the electromagnetic field equivalence principle to obtain frequency domain equivalent face magnetic current $J_{\mathrm{ms}}\left({\stackrel{\→}{r}}_{\mathrm{ms}}\right);$

Based on the equivalent face magnetic current on the described near field reference surface S Calculate the Electric Field Distribution of manikin inside, and obtain electromagnetic wave specific absorption rate SAR value corresponding to Electric Field Distribution.

2. method according to claim 1 is characterized in that, the described portable terminal MIMO antenna of setting up calculates the electromagnetic field of portable terminal MIMO antenna on this reference surface S and specifically comprises at the near field of free space reference surface S:

Based on the three-D space structure model of described portable terminal MIMO antenna, described portable terminal MIMO antenna is not contained the Electromagnetic Modeling of tissue; Wherein, comprise definite described MIMO antenna material electromagnetic parameter, electric magnetization source parameter and boundary condition;

Obtain the described near field electricity that does not contain the portable terminal MIMO antenna of tissue by numerical evaluation $E\left[\left({\stackrel{\→}{r}}_{\mathrm{ms}}\right)\right].$

3. method according to claim 1 is characterized in that, described near field reference surface S is the area of space between described portable terminal MIMO antenna and tissue model, and the outer normal direction of described near field reference surface S is away from the MIMO antenna direction;

The described frequency domain equivalent face magnetic current that obtains

Comprise: according to following formula, draw the lip-deep frequency domain equivalent face of described near field reference surface S magnetic current J _Ms:

Wherein, near field electromagnetic information

With frequency domain equivalent face magnetic current

Electric field, magnetic current complex values had both been comprised

Comprise again this electric field, locus coordinate that magnetic current is corresponding

4. method according to claim 3 is characterized in that, also comprises before the method: according to following formula, with the real space coordinate Be converted into the indexed coordinates that electromagnetic calculation needs:

Wherein, Δ x, Δ y and Δ z are respectively x, the spatial spreading unit of y and z direction,

With

Be respectively x, the mikey vector of y and z direction.I, j and k are the indexed coordinates that electromagnetic calculation needs.

5. method according to claim 1 is characterized in that, the described Electric Field Distribution that calculates manikin inside, and obtain SAR value corresponding to Electric Field Distribution and comprise:

Read in described frequency domain equivalent face magnetic current, be translated into time domain space distribution source;

With the time domain source space Distribution Value assignment that obtains to the near field with reference on site, space corresponding to S face;

Put into good conductor in the non-place of finding the solution, to guarantee this regional electromagnetic field as null field, the good conductor frequency domain equivalent face magnetic current of introducing

To produce telescope direct image planes magnetic current source, the equivalent face magnetic current source of finding the solution the place is 2 times that put into before the good conductor, is specially

By

Calculate externally driving source of tissue model

The Electric Field Distribution of inside under the incentive condition is utilized the SAR definition to calculate inside of human body SAR value and is distributed;

The non-place of finding the solution is null field.

6. method according to claim 5, it is characterized in that, the method also comprises: with the described SAR value distributed data of the inner additional space of the tissue model that obtains position, utilize 3 dimension figure show tools to show, obtain 3 of the inner SAR of manikin and tie up distribution plans.

7. a device that obtains the electromagnetic wave specific absorption rate is characterized in that, the first acquisition module, the first computing module, the second computing module, and SAR acquisition module, wherein,

The first acquisition module is used for setting up portable terminal MIMO antenna at the near field of free space reference surface S;

The first computing module is used for calculating the electromagnetic field of portable terminal MIMO antenna on this reference surface S;

The second computing module is used for adopting the electromagnetic field equivalence principle, on the near field reference surface S that the first acquisition module obtains, obtains frequency domain equivalent face magnetic current

The SAR acquisition module is used for based on the equivalent face magnetic current on the reference surface S

This equivalent face magnetic current

With the electromagnetic interaction of manikin, calculate the Electric Field Distribution of manikin inside, and obtain SAR value corresponding to Electric Field Distribution.

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