CN1135657C - Fast-wave oscillation type antenna with multi-layer grounding surface - Google Patents

Abstract

The present invention utilizes the resonance phenomenon of a fast-wave leaky mode to design an antenna. The antenna designed has the advantages that volume is small, the antenna can be arranged on a printed circuit board by surface mounting technology (SMT), and a general medium with relative dielectric constant value from 2 to 5 can be used.

Description

Fast-wave oscillation type antenna with multi-layer grounding surface

Technical field

The present invention relates to a kind of fast-wave oscillation type antenna, particularly relate to a kind of microminiature fast-wave oscillation type antenna that utilizes the surface adhering technology to install with multi-layer grounding surface with multi-layer grounding surface.

Background technology

Along with being extensive use of of wireless communication handset, concealed antenna more and more receives publicity.Concealed antenna can use the surface adhering technology to install because its volume is little, therefore can incorporate whole radio frequency electric circuit board, so promoted its reliability widely, has promoted the quality of mobile phone.

Common concealed antenna adopts the microstrip line of metal patch shape.Fig. 1 is a kind of metal patch microstrip antenna (patch antenna), and wherein, medium substrate 11 is positioned on the ground plane 12, be equipped with a metal patch 13 in the interposition of medium substrate 11, and the input of signal can be undertaken by feeder line 14.The design of the common many active antennas of this mode.

Fig. 2 is another kind of metal patch microstrip antenna, and its structure major part is similar to Fig. 1, and itself and Fig. 1 difference are that feeder line 15 is extended along the surface of medium substrate 11, utilize the via hole (via hole) of ceramic substrate descending along the edge again.Adopt this kind input mode to can be made into the antenna of surface adhesive type.

Fig. 3 is and the another kind of metal patch microstrip antenna that is widely known by the people, and its structure major part is similar to Fig. 1, but it is that employing probe or coaxial line 16 come input signal with Fig. 1 difference.This mode clearly is not suitable for being connected with other microwave circuits in the surface adhering mode, because coaxial cord need use microwave junction.

Studies show that: the resonance frequency of microstrip antenna approximately is inversely proportional to (ε _rBe relative dielectric constant).Because the restriction of this condition, Fig. 1 extremely microstrip antenna shown in Figure 3 need utilize dielectric constant to be higher than 20 medium substrate usually, to reach the purpose of microminiaturization.In addition, research also shows: the ground plane of limited size has very big influence to microstrip antenna.Therefore, ground plane must be greater than the area of metal patch, microstrip line ability operate as normal; If contact area is too little, then have influence on the performance of antenna.

In addition, utilize the dielectric material covibration, cooperate microstrip line or slotted line coupling energy, also can design the concealed antenna that is applied in the general volume circuit to dielectric resonator.But its size is also made peace greatly The class antenna is inversely proportional to, so also need utilize the dielectric material of high-k usually.

Observe the simplified model of the unipole antenna that is used for mobile phone again, shown in Fig. 4 (a), unipole antenna 42 length on the phone housing 41 are about 1/4th of free space wavelength.The simplified model of the another kind of helical antenna of Fig. 4 (b) expression mobile phone, the total length of this kind helical antenna 43 is also near free space wavelength λ ₀, so these two kinds of antennas obviously are not suitable as concealed microminiature antenna for mobile phone and use.

In addition, these two kinds of antennas all utilize casing to make ground plane, and the area of its ground plane is quite big usually, is about 2 λ in general design ₀ ²(λ ₀Be free space wavelength), along with this class mobile phone is more and more little, relatively the ground plane of antenna is also more and more little, so the performance of antenna just is affected.

Summary of the invention

In view of this, the present invention proposes a kind of microminiature antenna of particular design, remove non-radiating little band model (bound mode) except that utilizing unsettled microstrip line, also have the mutually interdependent fast wave leakage waves pattern of a kind of and non-radiating little band model, and this both mode current and transverse electric field (magnetic field) are all closely similar near the microstrip line scope.Therefore, can design a kind of fast-wave oscillation type antenna of multi-layer grounding surface according to the phenomenon that fast wave leakage waves pattern is resonated.

This antenna comprises a fast wave oscillation device and a multilayer earthing device, and wherein, this fast wave oscillation device comprises two parts, and first is the medium that shape is cuboid; Second portion is to climb the microstrip line that prolongs on this cuboid dielectric surface, and it is climbed the mode of prolonging and looks needed radiation pattern and adjust, and intensive in very little dielectric surface scope, and an end of this microstrip line is used for input signal, and the other end is for opening circuit.

This multilayer earthing device is positioned at the below of this fast wave oscillation device, its major part is most parallel layers that are positioned at the medium below, and most via holes (via hole), and all inner surfaces of the formed groove of these parallel layers are all metal ground plane with all inner surfaces of outer surface, these via holes and other surfaces below the medium.

Because the microstrip line in the fast wave oscillation device is distributed in the very little dielectric surface scope thick and fast, and the multilayer earthing device greatly increases the contact area in the confined space, so the size of antenna can be dwindled significantly.And this antenna can utilize the surface adhering technology to be directly installed on the printed circuit board (PCB).More particularly, antenna of the present invention does not need to use the dielectric material of high-k, as long as the general dielectric material of relative dielectric constant value between 2 to 5.

Description of drawings

Purpose of the present invention, advantage and characteristic are described in detail by following preferred embodiment, with reference to the accompanying drawings can be more clear.Wherein:

Fig. 1 is a kind of well-known metal patch microstrip antenna;

Fig. 2 is the another kind of well-known metal patch microstrip antenna that utilizes the via hole input;

Fig. 3 is for the well-known metal patch microstrip antenna of another probe input or coaxial line input;

The simplified model of the unipole antenna of a kind of well-known mobile phone of Fig. 4 (a) expression;

The simplified model of the helical antenna of the another kind of well-known mobile phone of Fig. 4 (b) expression;

The cross-sectional view of the desirable microstrip line construction of Fig. 5 (a) expression hanging type;

Fig. 5 (b) is the non-radiating wave mode of unsettled microstrip line and the propagation constant of fast wave leakage waves pattern;

Fig. 6 (a) is non-radiating wave mode and the fast wave leakage waves pattern CURRENT DISTRIBUTION at transverse direction;

Fig. 6 (b) non-radiating wave mode and fast wave leakage waves pattern are in the CURRENT DISTRIBUTION of longitudinal direction;

Fig. 7 is the pattern direction electric field field shape of unsettled microstrip line leakage waves pattern when diverse location (highly);

Fig. 8 represents the desirable microstrip line construction of hanging type;

Fig. 9 (a) is an embodiment with small-sized fast-wave oscillation type antenna of multi-layer grounding surface;

Fig. 9 (b) is the partial enlarged drawing of Fig. 9 (a);

Fig. 9 (c) is the schematic diagram of Fig. 9 (a);

Figure 10 (a) shows that antenna of the invention process is installed on the situation of external circuits substrate;

Figure 10 (b) shows on the external circuits substrate circuit corresponding to antenna part of the invention process;

Figure 11 is the equivalent electric circuit of the antenna of the embodiment of the invention;

Figure 12 is the measurement result of the single port Smith chart (one port SmithChart) of the embodiment of the invention;

Figure 13 is the measurement result of the single port scattering parameter (one port scatteringparameter) of the embodiment of the invention;

Figure 14 (a) is the current distributing figure on antenna top layer, top of its microstrip line (the A district among Fig. 9 (a)) when resonance frequency is 260MHz of the embodiment of the invention;

Figure 14 (b) is the current distributing figure on antenna top layer, below of its microstrip line (the A district among Fig. 9 (a)) when resonance frequency is 260MHz of the embodiment of the invention;

Figure 15 for the antenna of the embodiment of the invention when resonance frequency is 260MHz its radiation field shape on Y-Z plane.

Symbol description

11: medium substrate

12: ground plane

13: metal patch

14: feeder line

15: the feeder line that is connected to via hole

16: probe (or coaxial line) input

41: phone housing

42: unipole antenna

43: helical antenna

A: fast wave oscillation device

A0, A1, A2, A3: little band

B: multilayer earthing device

B1-B9: parallel layers

B10-B17,69: via hole

1,2,3,4: groove

C: hollow area

51: antenna I/O end

55,57: the antenna ground end

61: the I/O end of external circuits substrate

65,67: the earth terminal of external circuits substrate

70: metal ground connection

81: metal wire

82: medium substrate

83: the air band

84: ground plane

101: antenna of the present invention

103: the external circuits substrate

105: the ground plane of external circuits substrate

Embodiment

Fig. 5 (a) is the cross-sectional view of the desirable microstrip line construction of hanging type, and wherein each parameter is x ₁=300mm, b=421.6mm, w=1.6mm, h=0.762mm; ${\mathrm{\&epsiv;}}_{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="C9812338700202.png,C9812338700211.png"\; state="\{\{state\}\}">r</figure-callout>}}_1}=1.0,$ ${\mathrm{\&epsiv;}}_{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C9812338700202.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}=2.1$ And ${\mathrm{\&epsiv;}}_{{\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="C9812338700202.png"\; state="\{\{state\}\}">r</figure-callout>}}_3}=1.0.$ Fig. 5 (b) shows corresponding to Fig. 5 (a) and supposes that all metallic conductors have two kinds of patterns, i.e. γ of the unsettled microstrip line of infinitely great conductivity _m=β _m+ j0 and γ _l=β _l+ j α _lγ wherein _mWith γ _lBe respectively the propagation constant of non-radiating wave mode and leakage waves pattern, β _mWith β _lBe respectively the phase constant of non-radiating wave mode and leakage waves pattern, α _lAttenuation constant for the leakage waves pattern.

Shown in Fig. 6 (a) and Fig. 6 (b), its mould electric current (modal currents) is closely similar at the longitudinal direction and the transverse direction of microstrip line in the CURRENT DISTRIBUTION of transverse direction and longitudinal direction for these two kinds of patterns.In other words, if one of them pattern is excited, another also can be excited.

Except the mould electric current was similar, both transverse electric field/magnetic field was also closely similar near the microstrip line scope.Fig. 7 is illustrated in the pattern direction electric field field shape of leakage waves pattern of the unsettled microstrip line of diverse location, and wherein each parameter is (1) x _B1=299mm, x _T1=303mm, (2) X _B2=408mm, X _T2=412mm, (3) X _B3=677mm, x _T3=681mm; y ₁=208.3mm, y ₂=213.3mm.As shown in Figure 7, the leakage waves pattern has the attenuation constant of non-zero.

Detail analysis shows these two kinds coupling, i.e. its waveguide sectional area integration ∫ E mutually _(m)* H ^* _(l)Ds and ∫ E _(l)* H ^* _(m)Ds is all non-vanishing, E _(m), E _(l)Be respectively the electric field strength of the cross section of non-radiating wave mode and leakage waves pattern, H _(m), H _(l)Be respectively the magnetic field intensity of the cross section of non-radiating wave mode and leakage waves pattern.In other words, if excite well-known little band model, this little band model can convert portion of energy to the leakage waves pattern in communication process, and this leakage waves pattern can be delivered to energy in the atmosphere in propagation, process.On the contrary, the leakage waves pattern in the propagation also can convert portion of energy to little band model.

As shown in Figure 8, the desirable microstrip line construction of hanging type is formed by metal wire 81, medium substrate 82, air 83 and ground plane 84.The top of metal wire 81 also is full of by air.

Desirable microstrip line construction according to above operation principle and hanging type designs antenna of the present invention.It is made up of the two large divisions: a part is the fast wave oscillation device, and another part is by multi-layer grounding surface and the formed earthing device of via.

A preferred embodiment of Fig. 9 (a) expression antenna of the present invention, wherein A partly represents the fast wave oscillation device, B partly represents the multilayer earthing device.And,, in the A part medium in the fast wave oscillation device circuit is taken away in order more to clearly illustrate the circuit of fast wave oscillation device.In addition, the explanation of back is set three-dimensional X, Y and Z-direction and is respectively the length and width of antenna and high direction for convenience.Fig. 9 (b) is the partial enlarged drawing of Fig. 9 (a).

Fig. 8 is formed air band 83 between medium substrate and ground, and the hollow area C corresponding to Fig. 9 (b) can adopt the mode of grooving or casting to form.

Among Fig. 9 (b), fast wave oscillation device A is made of around the spirality metal microstrip line of cuboid dielectric surface a cuboid medium and little band A1, figure such as A2, A3.The tail end of this spirality metal microstrip line forms required the opening circuit of resonance.The microstrip line other end A0 that is connected little band A1 is used for the signal I/O end of antenna.Utilize printed-board technology or utilize casting to cooperate etched technology, can be made into this type of fast wave oscillation device.

Among Fig. 9 (b), multilayer earthing device B is positioned at the below of the cuboid medium of this fast wave oscillation device, and the major part of this device is most parallel layers B1-B9 that form below medium.Below these plane layers, in order to increase the surface area of ground plane, consider the mechanical strength of antenna simultaneously, most via hole B10-B17 have been made, and make all be formed within the groove 1-4 inner surface of surface and all via hole B10-B17 and all outer surfaces of associated media part are all metal ground plane, thereby form multilayer earthing device B by parallel layers.Its making can utilize the puncturing technique of printed circuit board (PCB), or utilizes casting to cooperate gold-plated technology to finish.

Among Fig. 9 (b), the I/O end A0 of microstrip line extends to 51 along dielectric surface, and forms the I/O mode of co-plane waveguides with multilayer earthing device B earth terminal 55,57.

Figure 10 (a) schematically illustrates the situation that antenna 101 of the present invention is installed on an external circuits substrate 103.With reference to Figure 10 (b), the connected mode of antenna and external circuit is among the present invention: the relevant position of external circuit substrate 103 also forms the I/O end 61,65,67 of co-plane waveguide, and wherein 61 is the I/O end of signal, and 65,67 all is earth terminal.Adopt the surface adhering technology, 51,55,57 are connected to 61,65,67 respectively; And, the same surface adhering technology that adopts, the multilayer earthing device, is connected with the ground plane 105 of external circuit substrate 103 by the many via holes 69 of external circuit substrate correspondence position and the metal of periphery 70 thereof to have the side of earth terminal and signal I/O end.

Fig. 9 (c) is the schematic diagram of Fig. 9 (a), and with reference to figure 9 (c), one of antenna group of design parameter is among the present invention: the width in little band territory and interval are respectively 0.39 * 10 ^-3λ ₀With 0.17 * 10 ^-3λ ₀(be w=0.39 * 10 ^-3λ ₀, s=0.17 * 10 ^-3λ ₀), being about of rectangle medium 10 is 0.039 λ ₀(be d=0.039 λ ₀, g=6.9 * 10 ^-3λ ₀), the length of side is about 4.3 * 10 ^-3λ ₀With 1.47 * 10 ^-3λ ₀(be e=4.3 * 10 ^-3λ ₀, f=1.47 * 10 ^-3λ ₀), i.e. ε _r=3.25, the number of turns N=57 of spiral type microstrip line.

According to above parameter, can calculate antenna volume of the present invention and be about 0.25 * 10 ^-6λ ₀ ³, the average length of side is about 0.63 * 10 ^-2λ ₀Reach the purpose of antenna microminiature integrated circuit.

In addition, the length of spiral type microstrip line is about:

5.8×10 ^-3λ ₀×57×2+0.17×10 ^-3λ ₀×57＝0.667λ ₀

The gross area of spiral type microstrip line is about:

0.667λ ₀×3.9×10 ^-4λ ₀＝260×10 ^-6λ ² ₀

When microstrip line formed resonance, current strength was roughly according to the distribution of shapes (this part back describes in detail again) on microstrip line of cosine function, and 1/4 the area that cosine function surrounded is 2/ π, so the average effective area of spiral type microstrip line is: $260\&times;{10}^{-6}{{\mathrm{\&lambda;}}^2}_0\&times;\frac{2}{\mathrm{\&pi;}}=166\&times;{10}^{-6}{{\mathrm{\&lambda;}}^2}_0$ Be equivalent to electric charge and be evenly distributed in effective area 166 * 10 ^-6λ ² ₀Microstrip line on.

And the estimation of the contact area of multilayer earthing device has 90.6 * 10 approximately ^-6λ ² ₀When shaking jointly, there is positive Q electric charge (Q is the quantity of electric charge) to flow into input 51 among Fig. 9 (b), enter the spiral type microstrip line through A0 again, be full of the microstrip line metal covering then; Some negative Q electric charge flows into earth terminal 55,57 simultaneously, is filled in all metal surfaces of multilayer earthing device then.Some negative Q electric charge then flows into external circuit plate earthing end 65,67 and reaches the ground plane that is connected with it in addition.Therefore, be maintained the balance of electric charge during resonance near the earth terminal of spiral type microstrip line and multilayer earthing device and input thereof.As seen, in antenna of the present invention, ground plane need not to accomplish that the area with existing mobile phone ground plane is the same big, but still enough uses.

And, need not use the dielectric material of high-k, use the relative dielectric constant value quite low as ε _rDielectric material between 2 to 5 gets final product.

The important function of fast wave leakage waves pattern in antenna of the present invention can be learnt by following calculating and deduction.

According to well-known microwave line theory, if the end that opens circuit of the transmission of a single mode element is without any fringing field effect (fringing field effect), but pure opening circuit, then as long as

(λ _gPropagation wavelength for single mode) odd multiple number of frequency of respective frequencies can form a resonant circuit.And, corresponding first resonance frequency, its resonance equation is: $l=\frac{1}{4}\&times;\frac{{\mathrm{\&lambda;}}_0}{\widehat{\mathrm{\&beta;}}}=\frac{1}{4}\mathrm{\&lambda;g}----\left(1\right)$ Wherein, l is the length of microstrip line,

Be normalized phase constant (normalizedphase constant), $\widehat{\mathrm{\&beta;}}=\frac{\mathrm{\&beta;}}{{\mathrm{<figure-callout\; id="0"\; label="K"\; filenames="C9812338700311.png"\; state="\{\{state\}\}">K</figure-callout>}}_0};$ ${\mathrm{<figure-callout\; id="0"\; label="K"\; filenames="C9812338700311.png"\; state="\{\{state\}\}">K</figure-callout>}}_0=\frac{2\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_0};$ $\mathrm{\&beta;}=\frac{2\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_g},$ And k ₀Be the free space wave number.

Figure 11 shows the equivalent electric circuit of antenna of the present invention, by open circuit 31, microstrip line 32, grounding system 33 and the power supply 34 of hanging type formed.Use above microwave line theory, if Figure 11 represents the resonant circuit of corresponding first resonance frequency, then the length of microstrip line 32 should be

The inventor utilizes three-dimensional all-wave electromagnetic field opinion to calculate resonance frequency and is 260MHz with above-mentioned Antenna Design parameter.On the other hand, will make single port S by the made antenna of above-mentioned design parameter ₁₁The measurement of parameter (being scattering parameter) can obtain Smith chart and corresponding S ₁₁The input stickogram is respectively as Figure 12 and shown in Figure 13.

In Figure 12, the vector analysis instrument scans to 300MHz from 240MHz.When low frequency, can learn Smith chart from its low order end promptly open circuit end points near, be docile and obedient clockwise by rotate near the end points place that opens circuit left near short dot, what stop at corresponding 300MHz then is positioned at the top-right point of Smith chart.Through labor, be that to be positioned at phase angle be 180 ° of operating frequency 259MHz that locate near the frequency of short-circuit end as can be known, this frequency is first resonance frequency.Differing with calculated value only is 1MHz.

First resonance frequency can more clearly be confirmed by Figure 13.With reference to Figure 13, S during resonance ₁₁Numerical value in the 259MHz minimum, be about-2.8dB, its phase angle is 180 °.Quarter-wave shown in Figure 11 ( ) resonator is when resonance, the reflection coefficient of its input is necessary for negative, and promptly phase angle is necessary for 180 °.Because this fast wave leakage waves pattern presents loss, so S ₁₁Absolute value will be less than 1, promptly less than 0dB.

Therefore, corresponding first resonance frequency is 0.667 λ with microstrip line length l of the present invention ₀In the substitution (1), learn Be 0.375.With respect to this

The phase velocity of the leakage waves pattern of value is: $c/\widehat{\mathrm{\&beta;}}=2.66c----\left(2\right)$ Wherein, c is the light velocity, and (2) formula represents that the phase velocity of this leakage waves pattern is 2.66 times of the light velocity, so it must be a fast wave (fast wave).

Further, utilize three-dimensional all-wave electromagnetic field opinion can calculate the top layer, top of the microstrip line (the A district among Fig. 9 (a)) when resonance frequency 260MHz and the CURRENT DISTRIBUTION on top layer, below, respectively shown in Figure 14 (a) and Figure 14 (b).When Figure 14 (a) is presented at resonance frequency 260MHz with Figure 14 (b), the electric current of microstrip line is in the input maximum, and its current strength diminishes gradually then, but that direction is kept is constant always, always towards the end points that opens circuit (being the terminal point of antenna resonator), to its current strength vanishing of end points of opening circuit.In other words, the variation of the size of mould electric current on microstrip line just as one between 0 cosine function to (pi/2) phase angle.Analyze as seen thus, this resonance mode must be that leakage waves could form.

The result of comprehensive above measurement data and Theoretical Calculation can obtain to draw a conclusion: new antenna of the present invention mainly relies on the conduction of fast wave leakage waves pattern.

Utilize antenna that well-known all-wave integral equation tries to achieve the embodiment of the invention when resonance frequency radiation field shape on the Y-Z plane during again for 260MHz, as shown in figure 15, wherein the θ angle is illustrated on the Y-Z plane certain a bit to the line of initial point and the angle between the Z axle.With reference to Figure 15, the radiation pattern of this radiation field and the unipole antenna on infinitely-great horizontal conductor ground plane is closely similar.

Above-mentioned is a specific embodiment of the present invention, yet the present invention is not limited to this embodiment.For example, observe the antenna structure of Fig. 9 (b), in fact, between the outer surface of the microstrip line of fast wave oscillation device and multilayer earthing device, be full of air, the air band 83 of same similar Fig. 8, so this hollow area C is not necessary.Correspondingly, the another kind of antenna that does not have hollow area C is arranged, in the case, the medium among fast wave oscillation device A and the multilayer earthing device B directly is engaged togather.

The shape of microstrip line also is not limited to spiral type, can look desired radiation pattern, uses different microstrip line shapes in the fast wave oscillation device.For example be most parallel and closed annular metal microstrip lines, its method for designing is similar to above-mentioned specific embodiment.

Moreover antenna of the present invention also can use the form of the direct I/O of feeder line.In the case, the relevant position of external circuit substrate also forms the corresponding directly form of input/output signal.Then, the microstrip line of fast wave oscillation device adopts the surface adhering mode to be connected to the I/O end of external circuit substrate correspondence in order to an end of input/output signal.And side and the employing surface adhering mode of this multilayer earthing device to have signal I/O end by a plurality of via holes of external circuit substrate correspondence position and the metal of periphery thereof, is connected with the ground plane of external circuit substrate.

So, can implement multiple variation in the situation of spirit that does not exceed the present invention and following claim scope.

Claims (3)

1, a kind of fast-wave oscillation type antenna with multi-layer grounding surface comprises:

One fast wave oscillation device is made up of first and second parts, this first

The medium substrate that is cuboid for shape, this second portion is the metal micro-strip line that is wrapped in this medium substrate surface, the winding form of this metal micro-strip line is looked needed radiation pattern and is adjusted, and it is intensive in this very little dielectric surface scope, one end of this metal micro-strip line is used to provide signal, and the other end is for opening circuit;

One earthing device is positioned at this fast wave oscillation device below, and the shape of this earthing device is cuboid, and is provided with most via holes, this via hole be shaped as rectangle,

Wherein this number that is shaped as rectangular via hole determines according to needed contact area with size, so that a predetermined structural strength to be provided, and

Take this this earthing device sizable contact area can be provided in the confined space.

2, the fast-wave oscillation type antenna with multi-layer grounding surface according to claim 1, wherein the medium substrate of this fast wave oscillation device is made of the dielectric material of relative dielectric constant value between 2 to 5.

3, a kind of fast-wave oscillation type antenna with multi-layer grounding surface comprises:

One fast wave oscillation device, formed by first and second parts, this first is the medium substrate that shape is cuboid, this second portion is the metal micro-strip line that is wrapped in this medium substrate surface, the winding form of this metal micro-strip line is looked needed radiation pattern and is adjusted, and intensive an end of this metal micro-strip line is used to provide signal in this very little dielectric surface scope, and the other end is for opening circuit;

One earthing device is positioned at this fast wave oscillation device below, and the shape of this earthing device is cuboid, and is provided with most via holes, and the shape part of this via hole is a rectangle, and a part is circular,

Wherein this number that is shaped as rectangular via hole determines according to needed contact area with size with size and this number that is shaped as circular via hole, so that a predetermined structural strength to be provided, and

Take this this earthing device sizable contact area can be provided in the confined space.

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