CN104569889A - Concentric and taper TEM (transverse electromagnetic mode) cell and method for designing interior conductor semi-included angle and exterior conductor semi-included angle of transmission section of concentric and taper TEM cell - Google Patents

Abstract

The invention discloses a concentric and taper TEM (transverse electromagnetic mode) cell and a method for designing an interior conductor semi-included angle and an exterior conductor semi-included angle of a transmission section of the concentric and taper TEM cell. The method comprises the following steps: according to the use requirement of the transmission section of the concentric and taper TEM cell, characteristic impedance ZC and a ratio theta 2/theta 1 of the exterior conductor semi-included angle and the interior conductor semi-included angle of the transmission section are selected; high order mode quantities corresponding to different interior conductor semi-included angles and exterior conductor semi-included angles of the transmission section of the concentric and taper TEM cell are calculated according to the selected characteristic impedance ZC and the ratio theta 2/theta 1 of the exterior conductor semi-included angle and the interior conductor semi-included angle of the transmission section of the concentric and taper TEM cell, the interior conductor semi-included angle and the exterior conductor semi-included angle which correspond to the minimum high order mode quantity are selected to serve as the interior conductor semi-included angle and the exterior conductor semi-included angle of the transmission section of the concentric and taper TEM cell. With adoption of the technical scheme, the interior conductor semi-included angle and the exterior conductor semi-included angle of the transmission section of the concentric and taper TEM cell are designed, so that the quantity of the high order mode is reduced, the high order mode cut-off frequency is increased, and the performance of the concentric and taper TEM cell is improved.

Description

The method for designing of concentric tapered TEM room and span line internal and external conductor half angle thereof

Technical field

The present invention relates to concentric tapered TEM room.More specifically, the method for designing of a kind of concentric tapered TEM room and span line internal and external conductor angle thereof is related to.

Background technology

Concentric tapered TEM room is exactly a kind of field intensity generation device based on standard magnetic field method, compared with TEM room, GTEM room, concentric tapered TEM room can produce the wide band electromagnetic field of 200MHz ~ 40GHz, can be used for setting up broadband field intensity calibration system, meet the full frequency band of field intensity probe, broadband frequency sweep calibration requirements.Concentric cone TEM room, by National Institute of Standards and Technology NIST early than development in 1999, similar with coaxial transmission line, it is a kind of two conductor transmission line, adopt axially symmetric structure, by coaxial feed, impedance matching section, span line, a few part composition such as terminator and absorbing material, its structural representation as shown in Figure 1, coaxial feed provides power input for concentric tapered TEM room, concentric conductor 50 Ω characteristic impedance is transformed to span line characteristic impedance by impedance matching section, terminator and absorbing material are used for electromagnetic wave absorption, reduce the standing wave loss of whole system, uniform TEM ripple is produced in final cavity between two metal concentric cones, form computable standard field intensity.Concentric tapered TEM room is in order to meet broadband, inside is multimode transmissions, span line internal and external conductor structural design determines the quantity of high-order mode, and high-order mode quantity is more larger on the pattern field good general impact in TEM room in concentric tapered TEM room, high-order mode quantity fewer concentric tapered TEM room performance is better.The performance of concentric tapered TEM room is also relevant with high-order mode cutoff frequency, and high-order mode cutoff frequency is higher, and illustrate that the frequency of operation that concentric tapered TEM room can be used is wider, performance is better.So when designing, the main quantity considering minimizing high-order mode, secondly also will consider the cutoff frequency improving high-order mode.The dimensional structure of concentric tapered TEM room determines can not eliminate high-order mode, can only reduce the quantity of high-order mode as much as possible, and carry the cutoff frequency of high-order mode on this basis.

Inner wire half angle of the concentric tapered TEM room span line of America NI ST design is θ ₁=1.895 °, outer conductor half angle is θ ₂=10 °, by the concentric wimble structure size of S Design, calculate the cutoff wavelength of its higher mode as shown in Figure 2, the cutoff wavelength of its high-order mode is relevant to the distance r of test probe to feeding point, in test section, cross-sectional direction outer conductor radius deducts inner wire radius is that the distance r of feeding point to test probe is measured at 0.2m place, and the high-order cutoff frequency calculated herein, the cutoff frequency of high-order mode is as shown in table 1:

Table 1 concentric tapered TEM room high-order mode cutoff frequency statistical form

For above span line structure, within the scope of working frequency range 200MHz ~ 40GHz, in former rank mould time, high-order mode quantity is more, will affect pattern field quality.By changing internal and external conductor half angle of cone TEM room with one heart, the quantity of high-order mode can be reduced, will be conducive to ensureing field uniformity.

Therefore, the computing method that a kind of concentric tapered TEM room span line internal and external conductor half angle is provided are needed.

Summary of the invention

One object of the present invention is to provide a kind of concentric tapered TEM room.

Another object of the present invention is the method for designing providing a kind of concentric tapered TEM room span line internal and external conductor half angle.

For achieving the above object, the present invention adopts following technical proposals:

A kind of concentric tapered TEM room, this TEM room comprises impedance matching section, coaxial two-conductor span line, terminator and absorbing material, and inner wire half angle of coaxial two-conductor span line is 1.5136 ° and half angle of outer conductor is 8 °.

Preferably, the span of the span line characteristic impedance of this TEM room is 75 Ω to 125 Ω.

Preferably, the test section radial space of this TEM room is about 0.2m × 0.2m × 0.2m.

A method for designing for concentric tapered TEM room span line internal and external conductor half angle, the method comprises the steps:

S1, request for utilization according to this concentric tapered TEM room span line, select its characteristic impedance Z _cand outer conductor half angle theta ₂with inner wire half angle theta ₁ratio θ ₂/ θ ₁;

The concentric tapered TEM room span line characteristic impedance Z that S2, basis are selected _cwith the ratio θ of outer interior half angle ₂/ θ ₁calculate the high-order mode quantity of the different concentric tapered TEM room span lines corresponding to span line internal and external conductor half angle of concentric tapered TEM room, choose internal and external conductor half angle corresponding to minimum high-order mode quantity, as this concentric tapered TEM room span line internal and external conductor half angle.

Preferably, the method comprises step further:

S3, according to this concentric tapered TEM room span line internal and external conductor half angle, calculate this concentric tapered TEM room span line high-order mode cutoff frequency, contrast the performance of this concentric tapered TEM room and existing concentric tapered TEM room.

Preferably, span line characteristic impedance Z in concentric tapered TEM room in step S1 _cspan be 75 Ω to 125 Ω.

Preferably, span line characteristic impedance Z in concentric tapered TEM room in step S1 _cwith its outer conductor half angle theta ₂with inner wire half angle theta ₁ratio θ ₂/ θ ₁relation be expressed as formula:

$Z_C=\frac{V\left(r\right)}{I\left(r\right)}=\frac{\mathrm{\β}}{2\mathrm{\π\ω\ϵ}}\ln \left[\frac{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_1}{2}\right)}{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_2}{2}\right)}\right]=\frac{{\mathrm{\η}}_0}{2\mathrm{\π}\sqrt{{\mathrm{\ϵ}}_r}}\ln \left[\frac{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_1}{2}\right)}{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_2}{2}\right)}\right]$

In formula, r is the distance of feeding point to test probe, and V (r) is the voltage between test probe place internal and external conductor; I (r) is the electric current on inner wire surface, test probe place; θ ₁for inner wire half angle; θ ₂for outer conductor half angle; ε _rfor the relative dielectric constant of material between internal and external conductor; η ₀for free space wave impedance.

Preferably, step S2 comprises following sub-step further:

According to selected concentric tapered TEM room span line characteristic impedance Z _cwith the ratio θ of outer interior half angle ₂/ θ ₁adopt the high-order mode quantity of the concentric tapered TEM room span line corresponding to span line internal and external conductor half angle of concentric tapered TEM room that the high-order mode routine analyzer iterative computation of Matlab is different, choose internal and external conductor half angle corresponding to minimum high-order mode quantity, as this concentric tapered TEM room span line internal and external conductor half angle.

Preferably, step S3 comprises following sub-step further:

S3.1, according to this concentric tapered TEM room span line internal and external conductor half angle, calculate the cutoff wavelength λ of this concentric tapered TEM room span line high-order mode _c, formula is as follows:

${\mathrm{\λ}}_c=\frac{2\mathrm{\πr}}{\sqrt{v(v+1)}}$

In formula: r is the distance of feeding point to test probe; The high-order mode quantity of ν corresponding to internal and external conductor half angle;

S3.2, deduct according to cross-sectional direction outer conductor radius in test section the cutoff wavelength λ that inner wire radius is the high-order mode at 0.2m place _c, calculate cross-sectional direction outer conductor radius in test section and deduct the cutoff frequency f that inner wire radius is the high-order mode at 0.2m place _c, formula is as follows:

λ _c＝cf _c

In formula, c is the light velocity;

S3.3, contrast this concentric tapered TEM room span line compared with the span line of existing concentric tapered TEM room in test section cross-sectional direction outer conductor radius deduct quantity and the cutoff frequency of high-order mode in former rank mould time that inner wire radius is 0.2m place.

Beneficial effect of the present invention is as follows:

The high-order mode of concentric tapered TEM room span line is the important indicator affecting TEM room field uniformity and repeatability, is related to accuracy and the validity of Field strength calibration result.Technical scheme of the present invention is by theory calculate and simulation analysis, and design concentric tapered TEM room span line internal and external conductor half angle, effectively reduces the quantity of high-order mode and improve high-order mode cutoff frequency, improves concentric tapered TEM chamber body pattern field performance.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.

Fig. 1 illustrates concentric tapered TEM cell structure schematic diagram.

Fig. 2 illustrates that the concentric tapered TEM room span line that America NI ST designs adopts inner wire half angle theta ₁=1.895 °, outer conductor half angle theta ₂under the Parameter Conditions of=10 °, in the span line of concentric tapered TEM room, in test section, cross-sectional direction outer conductor radius deducts the cutoff wavelength schematic diagram that inner wire radius is former rank mould time interior high-order mode at 0.2m place.

Fig. 3 illustrates concentric tapered TEM room span line characteristic impedance Z _cwith the ratio θ of exafference body half angle ₂/ θ ₁graph of relation.

Fig. 4-a to 4-c illustrates concentric tapered TEM room span line inner wire half angle theta ₁=1.5136 °, outer conductor half angle theta ₂transverse electric wave TE wave height rank modular function curve under the Parameter Conditions of=8 °.

Fig. 5-a to 5-c illustrates concentric tapered TEM room span line inner wire half angle theta ₁=1.5136 °, outer conductor half angle theta ₂transverse magnetic wave TM wave height rank modular function curve under the Parameter Conditions of=8 °.

Fig. 6 illustrates inner wire half angle theta of concentric tapered TEM room span line ₁=1.5136 °, outer conductor half angle theta ₂under the Parameter Conditions of=8 °, in the span line of concentric tapered TEM room, in test section, cross-sectional direction outer conductor radius deducts the cutoff wavelength schematic diagram that inner wire radius is former rank mould time interior high-order mode at 0.2m place.

Fig. 7 illustrates the method for designing process flow diagram of concentric tapered TEM room span line internal and external conductor half angle.

Embodiment

In order to be illustrated more clearly in the present invention, below in conjunction with preferred embodiments and drawings, the present invention is described further.Parts similar in accompanying drawing represent with identical Reference numeral.It will be appreciated by those skilled in the art that specifically described content is illustrative and nonrestrictive, should not limit the scope of the invention with this below.

As shown in Figure 1, the concentric tapered TEM room span line similar that the concentric tapered TEM room span line structure adopted in the present embodiment and NIST design, but inner wire half angle of the coaxial two-conductor span line in concentric tapered TEM room is 1.5136 ° and half angle of outer conductor is 8 ° in the present embodiment, the span of characteristic impedance is 75 Ω to 125 Ω, and test section radial space is about 0.2m × 0.2m × 0.2m.

The method for designing of concentric tapered TEM room span line internal and external conductor half angle that the present embodiment provides comprises the steps:

Step1, request for utilization according to this concentric tapered TEM room span line, select its characteristic impedance Z _cand outer conductor half angle theta ₂with inner wire half angle theta ₁ratio θ ₂/ θ ₁;

Concentric tapered TEM room span line outer conductor half angle theta ₂with inner wire half angle theta ₁ratio θ ₂/ θ ₁with concentric tapered TEM room span line characteristic impedance Z _crelational expression formula as follows:

$Z_C=\frac{V\left(r\right)}{I\left(r\right)}=\frac{\mathrm{\β}}{2\mathrm{\π\ω\ϵ}}\ln \left[\frac{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_1}{2}\right)}{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_2}{2}\right)}\right]=\frac{{\mathrm{\η}}_0}{2\mathrm{\π}\sqrt{{\mathrm{\ϵ}}_r}}\ln \left[\frac{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_1}{2}\right)}{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_2}{2}\right)}\right]$

In formula, r is the distance of feeding point to test probe, and V (r) is the voltage between test probe place internal and external conductor; I (r) is the electric current on inner wire surface, test probe place; θ ₁for inner wire half angle; θ ₂for outer conductor half angle; ε _rfor the relative dielectric constant of material between internal and external conductor; η ₀for free space wave impedance.

Medium in the present embodiment in concentric tapered TEM room is air, the relative dielectric constant ε of material between internal and external conductor _r=1, concentric tapered TEM room span line characteristic impedance Z _cwith inner wire half angle theta ₁, outer conductor half angle theta ₂relevant, consider the structure packing engineering factor of concentric tapered TEM room, require that inner wire weight is more light better, therefore inner wire half angle is the smaller the better, setting outer conductor half angle theta ₂variation range is 10 ° to 90 °, the ratio θ of concentric tapered TEM room span line and exafference body half angle ₂/ θ ₁between relation as shown in Figure 3.

As shown in Figure 3, outer conductor half angle theta ₂change between 10 ° to 90 °, concentric tapered TEM room span line characteristic impedance Z _cchange curve closely, as the ratio θ of exafference body half angle ₂/ θ ₁larger, the cavity space of cone is larger with one heart, characteristic impedance Z _clarger, therefore concentric tapered TEM room span line characteristic impedance Z _cratio primarily of exafference body half angle determines.

The request for utilization of concentric tapered TEM room span line is:

Conventional probe size is 5cm, consider the uncertainty of calibration, in order to ensure that uncertainty is below 1dB, then the radial space of test section is 3 times of probe size, but in order to the calibration of satisfied great majority probe, the radial space of setting test section is at least 0.2m × 0.2m × 0.2m, radial as the vertical direction in Fig. 1.

If cone span line selectivity characteristic impedance 50 Ω with one heart, although can mate well with the impedance of signal source, because the ratio of exafference body half angle is too little, its test space is too little, can not meet the needs of probe calibration.If select larger characteristic impedance, its test space can meet the demands, but needs to inject larger power, under therefore considering, and concentric tapered TEM room span line characteristic impedance Z _cscope be 75 Ω to 125 Ω, preferred concentric tapered TEM room span line characteristic impedance Z _cfor scope central value 100 Ω.

The concentric tapered TEM room span line characteristic impedance Z that Step2, basis are selected _cwith the ratio θ of outer interior half angle ₂/ θ ₁calculate the high-order mode quantity of the different concentric tapered TEM room span lines corresponding to span line internal and external conductor half angle of concentric tapered TEM room, choose internal and external conductor half angle corresponding to minimum high-order mode quantity, as this concentric tapered TEM room span line internal and external conductor half angle, detailed process is as follows:

Determining concentric tapered TEM room span line characteristic impedance Z _ccondition under, when inner wire half angle theta ₁with outer conductor half angle theta ₂time larger, the transcendental equation function curve fluctuation that transverse electric wave TE ripple, transverse magnetic wave TM ripple are corresponding is larger, and more with abscissa axis intersection point, corresponding root is also more, illustrates that the high-order mode composition comprised is also abundanter.

According to characteristic impedance Z _cwith the ratio θ of test zone radial space by outer interior half angle ₂/ θ ₁in the scope of restriction, by adopting the high-order mode routine analyzer program calculation of Matlab, scan different concentric tapered TEM room span line internal and external conductor half angles, calculate the high-order mode function curve corresponding to different internal and external conductor half angle and solve the root of transcendental equation corresponding to higher order mode, namely the quantity of the high-order mode corresponding to different internal and external conductor half angle is calculated, choose internal and external conductor half angle corresponding to high-order mode minimum number, as this concentric tapered TEM room span line internal and external conductor half angle;

The transcendental equation of transverse electric wave TE ripple is as follows:

$\frac{d{P}_n^m\left(\cos {\mathrm{\θ}}_1\right)}{d{\mathrm{\θ}}_1}\frac{d{Q}_n^m\left(\cos {\mathrm{\θ}}_2\right)}{d{\mathrm{\θ}}_2}=\frac{d{P}_n^m\left(\cos {\mathrm{\θ}}_2\right)}{d{\mathrm{\θ}}_2}\frac{d{Q}_n^m\left(\cos {\mathrm{\θ}}_1\right)}{d{\mathrm{\θ}}_1}$

In equation be respectively Legendre function of the first kind and Legendre function of the second kind, θ ₁and θ ₂be respectively inner wire half angle and outer conductor half angle;

The transcendental equation of transverse magnetic wave TM ripple is as follows:

$P_n^m\left(\cos {\mathrm{\θ}}_1\right)Q_n^m\left(\cos {\mathrm{\θ}}_2\right)=P_n^m\left(\cos {\mathrm{\θ}}_2\right)Q_n^m\left(\cos {\mathrm{\θ}}_1\right)$

In equation be respectively Legendre function of the first kind and Legendre function of the second kind, θ ₁and θ ₂be respectively inner wire half angle and outer conductor half angle;

Adopt the high-order mode routine analyzer alternative manner of Matlab, solve the transcendental equation of transverse electric wave TE ripple and the transcendental equation of transverse magnetic wave TM ripple, computing method are as follows:

N rank Legendre function of the first kind is:

$P_n\left(x\right)=\underset{k=0}{\overset{\left[\frac{n}{2}\right]}{\mathrm{\Σ}}}{(-1)}^k\frac{(2n-2k)!}{2^{n}k!(n-k)!(n-2k)!}{x}^{n-2k}$ Formula (2.74)

N rank first kind associated Legendre function is:

$P_n^m\left(x\right)={(1-x^2)}^{\frac{m}{2}}\frac{d^m{P}_n\left(x\right)}{{\mathrm{dx}}^m}={(1-x^2)}^{\frac{m}{2}}{P}_n^{\left(m\right)}$ Formula (2.75)

N rank Legendre function of the second kind is:

$Q_n\left(x\right)=\frac{1}{2}{P}_n\left(x\right)\ln \frac{1+x}{1-x}-\underset{k=1}{\overset{n}{\mathrm{\Σ}}}\frac{2n-4k+3}{(2+-1)(n-k+1)}{P}_{n-2k+1}\left(x\right)$ Formula (2.76)

N rank Equations of The Second Kind associated Legendre function is:

$Q_n^m\left(x\right)={(1-x^2)}^{\frac{m}{2}}\frac{d^m{Q}_n\left(x\right)}{{\mathrm{dx}}^m}={(1-x^2)}^{\frac{m}{2}}{Q}_n^{\left(m\right)}$ Formula (2.77)

The recursion formula of associated Legendre polynomial is:

$P_n^m\left(x\right)=\frac{1}{n-m}[(2n-1)x{P}_{n-1}^m\left(x\right)-(n+m-1)P_{n-2}^m\left(x\right)]$ Formula (2.78)

$P_n^m\left(x\right)=-\frac{2(m-1)}{\sqrt{1-x^2}}x{P}_n^{m-1}\left(x\right)-(n+m-1)(n-m+2)P_n^{m-2}\left(x\right)$ Formula (2.79)

$\frac{d}{\mathrm{dx}}{P}_n^m\left(x\right)=\frac{1}{x^2-1}[\mathrm{nx}{P}_n^m\left(x\right)-(n+m)P_{n-1}^m\left(x\right)]$ Formula (2.80)

This recursion formula is applicable to Legendre function of the second kind simultaneously, in order to adopt recursion formula program calculation, first must calculate initial value, can draw associated Legendre polynomial by formula (2.75), formula (2.77) expression:

P ₁ ⁰(x)＝x $Q_0^0\left(x\right)=\frac{1}{2}\ln \frac{1+x}{1-x}$

$\begin{array}{cc}{P}_2^0\left(x\right)=\frac{1}{2}({3x}^2-1)& Q_1^0\left(x\right)=\frac{x}{2}\ln \frac{1+x}{1-x}-1\end{array}$

$\begin{array}{cc}{P_1}^1\left(x\right)={(1-x^2)}^{\frac{1}{2}}& Q_0^1\left(x\right)={(1-x^2)}^{-\frac{1}{2}}\end{array}$

$\begin{array}{cc}{P}_2^1\left(x\right)=3x{(1-x^2)}^{\frac{1}{2}}& Q_1^1\left(x\right)={(1-x^2)}^{1/2}(\frac{1}{2}\ln \frac{1+x}{1-x}+\frac{x}{1-x^2})\end{array}$

P ₁ ²(x)＝0 $Q_1^2\left(x\right)=\frac{2}{1-x^2}$

$\begin{array}{cc}{P}_2^2\left(x\right)=3(1-x^2)& Q_2^0\left(x\right)=\frac{1}{4}({3x}^2-1)\ln \frac{1+x}{1-x}-\frac{3}{2}x\end{array}$

Then recurrence method is passed through, adopt the high-order mode routine analyzer of Matlab, using various different internal and external conductor half angle as computer program initial value, the high-order mode quantity corresponding to different internal and external conductor half angle can be drawn after program computation, internal and external conductor half angle corresponding to the minimum high-order mode of seletion calculation result, as this concentric tapered TEM room span line internal and external conductor half angle.

Fig. 4-a is respectively to 4-c, Fig. 5-a to 5-c and adopts iterative algorithm program calculation to go out this concentric tapered TEM room span line inner wire half angle theta ₁=1.5136 ° and outer conductor half angle theta ₂the high-order mode function curve of transverse electric wave TE ripple, transverse magnetic wave TM ripple under the Parameter Conditions of=8 °.

Step3, according to this concentric tapered TEM room span line internal and external conductor half angle, calculate this concentric tapered TEM room span line high-order mode cutoff frequency, contrast the performance of this concentric tapered TEM room and existing concentric tapered TEM room;

According to this concentric tapered TEM room span line internal and external conductor half angle, calculate the cutoff wavelength λ of concentric tapered TEM room span line high-order mode _c, formula is as follows:

${\mathrm{\λ}}_c=\frac{2\mathrm{\πr}}{\sqrt{v(v+1)}}$

In formula: r is the distance of feeding point to test probe; ν is the root of transcendental equation under internal and external conductor half angle condition, i.e. the quantity of high-order mode.

The cutoff wavelength of high-order mode is relevant to the distance r of test probe to feeding point, in test section, cross-sectional direction outer conductor radius deducts inner wire radius is 0.2m place, measure the distance r of feeding point to test probe, calculate concentric tapered TEM room span line high-order mode cutoff frequency.

The cutoff wavelength λ that inner wire radius is the high-order mode at 0.2m place is deducted according to cross-sectional direction outer conductor radius in test section _c, calculate the cutoff frequency f that position, test section radial space is the high-order mode at 0.2m place _c, formula is as follows:

λ _c＝cf _c

In formula, c is the light velocity;

Concentric tapered TEM room span line inner wire half angle theta that the high-order mode routine analyzer adopting Matlab 6.5 to work out calculates ₁=1.5136 ° and outer conductor half angle theta ₂under the Parameter Conditions of=8 °, former rank mould time interior high-order mode cutoff wavelength as shown in Figure 6;

As can be seen from Figure 6, the cutoff wavelength of high-order mode is relevant to radial distance r, and in test section, cross-sectional direction outer conductor radius deducts inner wire radius is 0.2m place, and the cutoff frequency of former rank mould time interior high-order mode is as shown in table 2 below:

Table 2 concentric tapered TEM room high-order mode cutoff frequency statistical form

Compared with the high-order modulus table 1 of the concentric tapered TEM room span line designed with America NI ST, the high-order mode quantity of the concentric tapered TEM room span line of Technical Design of the present invention obviously reduces and high-order mode cutoff frequency increases.

Obviously; the above embodiment of the present invention is only for example of the present invention is clearly described; and be not the restriction to embodiments of the present invention; for those of ordinary skill in the field; can also make other changes in different forms on the basis of the above description; here cannot give exhaustive to all embodiments, every belong to technical scheme of the present invention the apparent change of extending out or variation be still in the row of protection scope of the present invention.

Claims (9)

1. a concentric tapered TEM room, this TEM room comprises impedance matching section, coaxial two-conductor span line, and terminator and absorbing material, is characterized in that,

Inner wire half angle of coaxial two-conductor span line is 1.5136 ° and half angle of outer conductor is 8 °.

2. concentric tapered TEM room according to claim 1, is characterized in that, the span of the span line characteristic impedance of this TEM room is 75 Ω to 125 Ω.

3. concentric tapered TEM room according to claim 1, is characterized in that, the test section radial space of this TEM room is about 0.2m × 0.2m × 0.2m.

4. a method for designing for concentric tapered TEM room span line internal and external conductor half angle, it is characterized in that, the method comprises the steps:

S1, request for utilization according to this concentric tapered TEM room span line, select its characteristic impedance Z _cand outer conductor half angle theta ₂with inner wire half angle theta ₁ratio θ ₂/ θ ₁;

The concentric tapered TEM room span line characteristic impedance Z that S2, basis are selected _cwith the ratio θ of outer interior half angle ₂/ θ ₁calculate the high-order mode quantity of the different concentric tapered TEM room span lines corresponding to span line internal and external conductor half angle of concentric tapered TEM room, choose internal and external conductor half angle corresponding to minimum high-order mode quantity, as this concentric tapered TEM room span line internal and external conductor half angle.

5. the method for designing of concentric tapered TEM room according to claim 4 span line internal and external conductor half angle, it is characterized in that, the method comprises step further:

S3, according to this concentric tapered TEM room span line internal and external conductor half angle, calculate this concentric tapered TEM room span line high-order mode cutoff frequency, contrast the performance of this concentric tapered TEM room and existing concentric tapered TEM room.

6. the computing method of concentric tapered TEM room according to claim 4 span line internal and external conductor half angle, is characterized in that, span line characteristic impedance Z in concentric tapered TEM room in described step S1 _cspan be 75 Ω to 125 Ω.

7. the method for designing of concentric tapered TEM room according to claim 4 span line internal and external conductor half angle, is characterized in that, span line characteristic impedance Z in concentric tapered TEM room in described step S1 _cwith its outer conductor half angle theta ₂with inner wire half angle theta ₁ratio θ ₂/ θ ₁relation be expressed as formula:

$Z_C=\frac{V\left(r\right)}{I\left(r\right)}=\frac{\mathrm{\β}}{2\mathrm{\π\ω\ϵ}}\ln [\frac{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_1}{2}\right)}{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_2}{2}\right)}=\frac{{\mathrm{\η}}_0}{2\mathrm{\π}\sqrt{{\mathrm{\ϵ}}_r}}\ln [\frac{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_1}{2}\right)}{\mathrm{ctg}\left(\frac{{\mathrm{\θ}}_2}{2}\right)}$

In formula, r is the distance of feeding point to test probe, and V (r) is the voltage between test probe place internal and external conductor; I (r) is the electric current on inner wire surface, test probe place; θ ₁for inner wire half angle; θ ₂for outer conductor half angle; ε _rfor the relative dielectric constant of material between internal and external conductor; η ₀for free space wave impedance.

8. the method for designing of concentric tapered TEM room according to claim 4 span line internal and external conductor half angle, it is characterized in that, described step S2 comprises following sub-step further:

According to selected concentric tapered TEM room span line characteristic impedance Z _cwith the ratio θ of outer interior half angle ₂/ θ ₁adopt the high-order mode quantity of the concentric tapered TEM room span line corresponding to span line internal and external conductor half angle of concentric tapered TEM room that the high-order mode routine analyzer iterative computation of Matlab is different, choose internal and external conductor half angle corresponding to minimum high-order mode quantity, as this concentric tapered TEM room span line internal and external conductor half angle.

9. the method for designing of concentric tapered TEM room according to claim 5 span line internal and external conductor half angle, it is characterized in that, described step S3 comprises following sub-step further:

S3.1, according to this concentric tapered TEM room span line internal and external conductor half angle, calculate the cutoff wavelength λ of this concentric tapered TEM room span line high-order mode _c, formula is as follows:

${\mathrm{\λ}}_c=\frac{2\mathrm{\πr}}{\sqrt{v(v+1)}}$

In formula: r is the distance of feeding point to test probe; The high-order mode quantity of ν corresponding to internal and external conductor half angle;

S3.2, deduct according to cross-sectional direction outer conductor radius in test section the cutoff wavelength λ that inner wire radius is the high-order mode at 0.2m place _c, calculate cross-sectional direction outer conductor radius in test section and deduct the cutoff frequency f that inner wire radius is the high-order mode at 0.2m place _c, formula is as follows:

λ _c＝cf _c

In formula, c is the light velocity;

S3.3, contrast this concentric tapered TEM room span line compared with the span line of existing concentric tapered TEM room in test section cross-sectional direction outer conductor radius deduct quantity and the cutoff frequency of high-order mode in former rank mould time that inner wire radius is 0.2m place.