TWI391677B - Coupled-line structure hf capacitance tester and its test method - Google Patents

Description

High-frequency capacitance tester with coupled line structure and test method thereof

The present invention relates to a high-frequency capacitance tester for a coupled line structure and a test method thereof, and more particularly to a method of coating a coupled line group on a substrate for electrical bonding of a capacitor to be tested, and measuring the same by a measuring device. A scattering parameter of the high-frequency capacitance tester is obtained, and then the capacitance value to be measured corresponding to the scattering parameter is obtained.

According to the general structure of the capacitor, the basic structure of the capacitor is composed of two metal plates, and the intermediate space is formed by a combination of insulating materials. The size of the capacitance depends on the area of the metal piece, the spacing between the two plates, and the material between the two plates. Medium constant. The first recorded capacitor in history was invented by Ewald Georg von Kleist in October 1745. The structure is a glass bottle with a metal film inside and outside, and a glass bottle. The metal rod has one end connected to the inner metal film and the other end to a metal sphere. In January 1746, a Danish physicist, Masonbrook, independently invented a very similar capacitor, and the invention of Bishop Crest was not well known. Since Masonbrook taught at Leiden University at the time, he named it the Leiden bottle as a reference [1].

With the rapid development of modern communication systems, capacitors are widely used in high-frequency bypass, cross-connect capacitors and DC blocking (DC block), such as reference [2-3]. If combined with inductors, they can be designed as filters. Such as reference [4-6], or tuning circuit such as reference [7]. With the widespread use of capacitors, the technology of measuring capacitance is becoming increasingly important.

At present, the specific method of the capacitance tester is: using the LCR meter measurement, the principle is to send an AC signal with a known amplitude and frequency to the capacitor to be tested, and the current of the capacitor can be measured by the internal processing of the instrument to measure the capacitor to be tested. Capacitance value. M. Fonseca da Silva et al. proposed an analog-to-digital (ADC) circuit, a digital to analog (DAC) circuit, an integrated circuit, and an automatic capacitance measurement of a personal computer based on a conventional Schering bridge circuit. Method [8]. P. Aronhime et al. proposed three architectures, using a basic RC series circuit, plus a diode and a switch, and calculating the capacitance through the charge and discharge time of the capacitor as described in [9]. MA Atmanand et al. proposed to measure the voltage or current on the component and its phase difference on the unknown component to be tested, and then measure the unknown component to be tested as an inductor or capacitor. [10]. This paper proposes a new method for measuring high-frequency capacitance values using planar circuit structures and network analyzers.

references

[1] http://wikipedia. tw/

[2] D. Lacombe, J. Cohen, "Octave-Band Microstrip DC Blocks (Short Papers)," IEEE Trans. Microwave Theory and Tech., Vol. 20, no. 8, pp. 555-556, Aug. 1972 .

[3] C. Y. Ho, "Analysis of DC Blocks Using Coupled Lines (Letters)," IEEE Trans. Microwave Theory and Techniques, Vol. 23, no. 9, pp. 773-774, Sep. 1975.

[4] G. L. Matthaei, L. Young and E. M. T. Jones, Microwave Filters, Impedanc-Matching Network, and Coupling Structures, Artech House, Debham, Mass., 1980.

[5] R. E. Collin, Foundations for Microwave Engineering, Second Edition, McGraw-Hill, N. Y., 1992.

[6] J. S. Hong, M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, Wiley, N. Y., 2001.

[7] S. Sabaroff, "Impulse Excitation of a Cascade of Series Tuned Circuits," Proceedings of the IRE, Vol. 32, no. 12, pp. 758-760, Dec. 1944.

[8] M. Fonseca da Silva, A. Cruz Serra, “Capacitance measurement method,” IEEE AFRICON 4th AFRICON, Vol. 1, pp. 247-250, Sept. 1996.

[9] P. Aronhime, G. Cecil, "A new method of capacitance measurement," Proceedings of the 35th Midwest Symposium on Circuits and Systems, Vol. 1, pp. 718-721, Aug. 1992.

[10] M. A. Atmanand, V. J. Kumar, V. G. K. Murti, “Anovel method of measurement of L and C,” IEEE Transactions on Instrumentation and Measurement, Vol. 44, no. 4, pp. 898-903, Aug. 1995.

[11] E. M. T. Jones, "Coupled-Strip-Transmission-Line Filters and Directional Couplers," IEEE Trans. Microwave Theory and Tech., vol. 4, pp. 75-81, Apr. 1956.

[12] G. I. Zysman and A. K. Johnson, "Coupled Transmission Line Networks in an Inhomogeneous Dielectric Medium," IEEE Trans. Microwave Theory and Tech., vol. 17, pp. 753-759, Oct. 1969.

[13] Pozar, D. M., Microwave Engineering, Second Edition, New York: Wiley, 1998.

The main object of the present invention is to provide a high-frequency capacitance tester with a coupled line structure and a test method thereof, which mainly utilizes a planar circuit structure and a network analyzer to measure a high-frequency capacitance value, and after actual circuit measurement and simulation results It shows that the analog value is quite consistent with the measured value, so it can be used in the production line in the industry. Therefore, it has the characteristics of simple structure, convenient design, quick and convenient measurement, and easy production to greatly reduce production cost.

In order to achieve the above-mentioned effects, the technical means adopted by the present invention is to apply a coupling line group on a substrate, the coupling line group is a first coupling line extending in a straight line and two second coupling lines on the substrate and on the same line. The first end of the first coupling line is a signal input end, the second end of which is a signal output end, the first ends of each second coupling line are respectively grounded, and the second ends of the two second coupling lines are opposite And having a gap for electrically connecting the capacitor to be tested, and measuring a scattering parameter of the high-frequency capacitance tester by using a measuring device, and obtaining a test corresponding to the scattering parameter after calculation Capacitor value.

壹. The technical concept of the present invention

Referring to FIG. 5 and FIG. 2, the present invention is mainly applied to the technical field of high-frequency capacitance measurement, and uses a planar circuit structure and a network analyzer to achieve measurement of high-frequency capacitance values, and A coupling line group (20) composed of two coupled lines connected in series for electrically connecting the capacitor C to be tested, and the circuit simulation can be transmitted through the coupling line (as shown in Reference [11-12]) and the odd-even mode analysis method. The analysis (such as reference [13]) has the characteristics of simple structure, convenient design and production, and the actual circuit measurement and simulation results show that the simulated value and the measured value are quite consistent, so it can be used for a large number of industries. application.

贰. The specific implementation of the present invention

2.1 Basic features of the invention

Referring to FIG. 5 and FIG. 2, the basic technical feature of the present invention is that a coupling line group (20) is disposed on a substrate (10), and the coupling line group (20) is a first coupling line extending from a straight line. (21) and a second coupling line (22) on the substrate (10) and on the same straight line for electrically connecting a capacitor C to be tested.

A measuring stud is connected to the conductive studs (216) (217) provided with external threads at the signal input end (210) and the signal output end (211) to measure the scattering parameters. The scattering parameter calculates the corresponding capacitance value of the capacitor C to be tested.

In order to facilitate the review of the present invention, the constituent elements and the like are respectively described in detail as follows.

2.2 substrate

Referring to FIG. 5 and FIG. 2, the substrate (10) of the present invention is mainly provided with a coupling line group (20) disposed thereon to form a high frequency capacitance tester. In a specific embodiment, the coupling line The group (20) is formed on the substrate (10) by printing or etching, and the board used for the substrate (10) is a FR-4 copper-clad double-sided panel, the substrate (10) has a thickness of 1.6 mm, and a relative dielectric constant. At 4.3, the substrate (10) has a size of 5.784 cm x 0.402 cm.

2.3 Coupling line group

Referring to FIG. 5 and FIG. 2, the coupling line set (20) of the present invention comprises a first coupling line (21) and two second coupling lines (22) extending in a straight line, and the first coupling line (21) and the The two coupling lines (22) respectively have a first end and a second end, wherein the first end of the first coupling line (21) is a signal input end (210), and the second end is a signal output end (211). In addition, the two second coupling lines (22) are located on the same line of the substrate (10) and are parallel to the first coupling line (21) and can be coupled, and each second coupling line (22) The first ends are respectively grounded, and have a gap (220) opposite to the second ends of the two second coupling lines (22), and the gaps (220) can be placed for a capacitor C to be tested, and the two The second ends of the two coupling lines (22) are respectively electrically connected by the two ends of the power supply container C, and a scattering device can measure a scattering parameter of the high-frequency capacitance tester according to the scattering parameter. After calculation, the capacitance value to be measured corresponding to the scattering parameter can be obtained.

Referring to FIG. 5, the size of the coupling group (20) is standardized to reduce the size of the substrate (10), and the coupling mode group (20) has an even mode impedance of 100 ohms, and the odd mode impedance is 50 ohms, and then the signal is made. The characteristic impedance of the input terminal (210) and the signal output terminal (211) are both 50 ohms to improve the measurement accuracy.

Furthermore, in the experimental example of the present invention, the line width of the first coupling line and the second coupling line of the coupling line group (20) is 1.36 mm, and the first coupling line (21) and the second coupling line (22) The pitch is 0.43 mm, the lengths of the first coupling line (21) and the second coupling line (22) are respectively 21.42 mm, and the spacing of the second ends of the second coupling line (22) is 1 mm. Moreover, the first end and the second end of the first coupling line (21) respectively have an outwardly enlarged trapezoidal section (212) (213) and a rectangular section (214) (215) at the enlarged end, respectively. A rectangular segment (214) is used as the signal input terminal (210), and another rectangular segment (215) is used as the signal output terminal (211). Wherein each trapezoidal segment (212) (213) has a length of 2 mm, each rectangular segment (214) (215) has a length of 5 mm, and each rectangular segment (214) (215) has a line width of 3.1mm.

2.4 Measuring device

The specific embodiment of the measuring device of the present invention is a vector network analyzer. Since the vector network analyzer of the measuring device is a measuring tool widely used for measuring RF radio frequency and microwave scattering parameters, No further specific disclosure is made in the illustrated example. The vector network analyzer used in the present invention comprises an output port connected to the signal input terminal (210), and a receiving port connected to the signal output terminal (211). The vector network analyzer consists of The output 埠 output is measured by a first coupling line (21) coupled to the second coupling line (22), and the receiving 埠 receives a signal to measure the scatter parameter.

In the vector network analyzer, a line Gauge embedded in an electromagnetic simulation software IE3D is used to calculate the impedance and electrical length (θ) of the coupled line group (20) for the microstrip line structure size. The circuit simulation is performed with the electromagnetic simulation software IE3D. The circuit simulation sets the center frequency of 2 GHz, and calculates the electrical length (θ) of the coupled line group (20) with a quarter wavelength of the highest test frequency, and the electrical length (θ ) is 90 degrees.

The measuring device uses the impedance matrix of the coupled line group (20) and the odd and even mode analysis method to obtain the scattering parameter, and the line width and the line spacing of the coupled line group (20) are the even mode impedance (Zoe) and the odd mode. The impedance (Zoo) and the relative dielectric constant of the circuit substrate (10) are determined, and may affect the reflection coefficient of the signal output end (211) and the signal intensity of the signal input end (210).

Analysis of the electrical characteristics of the circuit structure

Referring to FIG. 1(a) and FIG. 5, the high-frequency capacitance tester of the present invention has left-right symmetry characteristics, and the circuit can be directly cut to perform odd and even mode analysis, as shown in FIG. 1(b) and (c). Show. Z _oo and _Zoe are the odd and even mode impedances of the coupled line group (20) (Z _oe =1/Y _oe , Z _oo =1/Y _oo ), θ is the electrical length of the coupled line group (20), C For the capacitor to be tested.

First, analyze the even-mode circuit. As shown in Figure 1(b), using the coupled-line impedance matrix, as shown in equation (1), perform circuit analysis. The boundary conditions can be observed as I ₃ = I ₄ =0 and V ₁ = 0

After entering the boundary conditions, the integrated input impedance of the even mode circuit is obtained. As in equation (2)

Then analyze the odd-mode circuit, as shown in Figure 1 (c), using the coupling line group (20) admittance matrix, as shown in equation (3), perform circuit analysis [11-13], and observe that the boundary condition is V. ₁ =V ₃ =0, Zc=1/Yc=1/jω2C

After entering the boundary conditions, the overall odd-mode circuit input impedance can be obtained. As shown in equation (4)

After calculating the odd-mode and even-mode circuit impedances, the reflection coefficients 奇偶_o and Γ _{e of the} odd-even mode can be derived separately as shown below.

After finishing, the reflection coefficient Γ _o and Γ _{e of} the odd-even mode can be obtained as shown in equations (5) and (6).

Since the reflection coefficient conversion scattering parameter formula [13] is as shown in equations (7) and (8)

The available scattering parameters |S ₁₁ | and |S ₂₁ | are expressed as shown in equations (9) and (10), respectively.

Wherein the Z of the impedance matrix and the admittance matrix Y formula are as shown in equations (11)-(18)

肆. Circuit characteristics simulation analysis

Please refer to Figure 2 (a), (b), first simulate with the high-frequency simulation software Microwave Office, set the circuit center frequency to 2GHz, the coupling line group (20) gas length θ is 90 °, freely given capacitance C is 6.8 pF value, to change the different odd and even mode characteristic impedance Z _oo, Z _oe, changes observed case, two results are shown in (a), (b) shown in FIG. Z _oo =25Ω, _Zoe =100 (diamond mark), Z _oo =50Ω, _Zoe =100 (square mark), Z _oo =50Ω, _Zoe =150 (triangle mark), Z _oo =50Ω, _Zoe = 200 (cross mark), and it can be observed from the figure that if the given odd model impedance Z _{oo is} smaller, its |S ₂₁ | resonance frequency will move to high frequency; and the given even model impedance Z _oe The larger, the |S ₂₁ | resonance frequency will move to the low frequency. The results show that changing the odd and even model impedances Z _oo and _Zoe does not have a significant impact on the circuit characteristics. Therefore, it is easier to select the odd model impedance of the engraving machine, Z _oo = 50Ω, and the even model impedance, _Zoe = 100Ω. .

It can be seen from the simulation results that the structure has a rejection characteristic, so |S ₂₁ | needs to be 0. It can be known from equation (8) that if |S ₂₁ | is 0, Γ _e needs to be equal to Γ _o , and . Derivation of the following

Electrical length of the coupling line After finishing into the above equation can be obtained by the measured capacitance C | S ₂₁ | resonant frequency relationship, formula (19) shown in FIG. Where β is the propagation constant (β=2π/λ, λ is the wavelength), For the actual length of the coupled line group (20), f ₀ and f are the circuit center frequency and |S ₂₁ | resonance frequency point, respectively, and m is the ratio value.

Please refer to Figure 3, set the circuit center frequency to 2GHz, odd and even model impedance Z _oo = 50Ω, _Zoe = 100Ω and the coupling line group (20) electrical length θ is 90°, bring the above derivation After the formula (19), the numerical analysis software Matlab is used for calculation and drawing, and the relationship between the capacitance value to be measured and the |S ₂₁ | resonance frequency point can be plotted, for example. When the capacitance value to be measured is 0 pF, the |S ₂₁ | resonance frequency point is 2 GHz. When the frequency is 1 to 2 GHz, it changes linearly; when the frequency is less than 1 GHz, it changes exponentially, that is, when the value of the capacitor to be measured is large enough, the influence of the change of |S ₂₁ | resonance frequency point is also better. small. It can be observed that when the capacitor C to be tested is large, the |S ₂₁ | resonance frequency point moves to the low frequency; conversely, if the capacitor C to be tested is small, the |S ₂₁ | resonance frequency point moves to the high frequency.

Wu. Simulation and implementation results

Referring to FIG. 4(a) and (b), the circuit simulation of the present invention is performed using the electromagnetic simulation software IE3D, the given center frequency is 2 GHz, the odd and even model impedances Z _oo = 50 Ω, Zo _oe = 100 Ω, and coupling. The line electrical length θ is 90°, and then simulate different capacitance values C to be measured as 0.3pF (diamond mark), 0.7pF (square mark), 1.5pF (triangle mark), 3pF (cross mark) and 6.8pF (star). Mark) Five capacitance values, as shown in Figure 4 (a), (b). It can be observed that when the capacitance values C are 0.3, 0.7, 1.5, 3, and 6.8 pF, the |S ₂₁ | resonance frequencies are 1.513, 1.169, 0.868, 0.637, and 0.431 GHz, respectively.

Referring to Figure 5 and Figure 2, the substrate (10) used for the circuit is FR-4 double-sided. The substrate (10) has a thickness of 1.6 mm and a relative dielectric constant of 4.3. Bring the above values into the Line Gauge contained in the electromagnetic simulation software IE3D, and calculate the microstrip line structure size, and obtain W ₁ =3.1mm, W ₂ = 1.36mm, W ₃ =0.43mm, L ₁ =5mm, L ₂ = 2 mm, L ₃ = 21.42 mm, L ₄ = 1 mm, the characteristic impedance of the input and output 埠 (31) is 50 ohms, the line width is W ₁ = 3.1 mm, and any given length L ₁ = 5 mm is convenient for fabrication. The circuit structure is shown in Figure 5. The actual circuit is shown in Annex 2. The circuit size is 5.784cm × 0.402cm and measured by the vector network analyzer Anritsu-37269D.

Please refer to Figure 6 (a) and (b), where Figure 6 (a) (b) is the scattering parameter |S ₁₁ | and |S ₂₁ | actual measurement results of the circuit, respectively, measuring different capacitances to be tested The value C is five capacitance values of 0.3 pF (diamond mark), 0.7 pF (square mark), 1.5 pF (triangle mark), 3 pF (cross mark), and 6.8 pF (star mark). It can be observed that when the capacitance values C are 0.3, 0.7, 1.5, 3, and 6.8 pF, the |S ₂₁ | resonance frequencies are 1.388, 1.086, 0.833, 0.621, and 0.416 GHz, respectively.

Please refer to Figure 7. In order to change the actual measurement of different capacitance values and the IE3D simulation comparison chart, it can be observed that the simulation and the measured results have a fairly high consistency. The numerical comparison is shown in Table 1. When the capacitance to be measured is 0.3pF, the resonant frequency points of theoretical calculation, IE3D simulation and actual measurement are 1.491, 1.513, 1.388GHz, respectively. The capacitance error between simulation and actual measurement, theory and actual measurement. They were 0.153 and 0.098 pF, respectively (the error percentages were 0.51% and 0.326%, respectively). When the capacitance to be measured is 0.7pF, the resonance frequency points of theoretical calculation, IE3D simulation and actual measurement are 1.165, 1.169, 1.086GHz, respectively. The capacitance errors of simulation and actual measurement, theoretical and actual measurement are 0.194 and 0.153pF respectively (error percentage They were 0.277% and 0.218%, respectively. When the capacitance to be measured is 1.5pF, the resonance frequency points of theoretical calculation, IE3D simulation and actual measurement are 0.87, 0.868, and 0.833GHz, respectively. The capacitance errors of simulation and actual measurement, theoretical and measured are 0.277 and 0.161pF, respectively. They are 0.185% and 0.107%, respectively. When the capacitance to be measured is 3pF, the resonance frequency points of theoretical calculation, IE3D simulation and actual measurement are 0.641, 0.637, and 0.621GHz, respectively. The capacitance errors of simulation and actual measurement, theoretical and measured are 0.208 and 0.221pF, respectively. It is 0.069%, 0.074%). When the capacitance to be measured is 6.8pF, the resonant frequency points of theoretical calculation, IE3D simulation and actual measurement are 0.437, 0.431, and 0.416GHz, respectively. The capacitance errors of simulation and actual measurement, theoretical and measured are 0.725 and 0.726pF, respectively. They are 0.106% and 0.107%, respectively.

Conclusion

With the above technical features, the present invention can indeed measure the high-frequency capacitance value by using the planar circuit structure and the network analyzer. After the actual circuit measurement and simulation results show that the analog value and the measured value are quite consistent. Therefore, the industry can be fully applied to the production line, and thus has the characteristics of simple structure, convenient design, quick and convenient measurement, and easy production to greatly reduce production cost.

The above is only one of the possible embodiments of the present invention, and is not intended to limit the scope of the patents of the present invention, and the equivalents of other variations of the contents, the features and the spirit of the following claims. All should be included in the scope of the patent of the present invention. The invention is specifically defined in the structural features of the scope of the patent application, is not found in the same kind of articles, and has practicality and progress, has met the requirements of the invention patents, and has applied for the law according to law, and invites the bureau to approve the patents according to law to maintain The legal rights of the applicant.

(C). . . Capacitor

(10). . . Substrate

(20). . . Coupled line set

(twenty one). . . First coupling line

(210). . . Signal input

(211). . . Signal output

(212) (213). . . Trapezoidal segment

(214) (215). . . Rectangular segment

(216) (217). . . Stud

(twenty two). . . Second coupling line

(220). . . Void

Figure 1 (a) is a schematic diagram of an equivalent circuit of the capacitance tester of the present invention.

Figure 1 (b) is a schematic diagram of an even mode circuit of the present invention.

Figure 1 (c) is a schematic diagram of the odd-mode circuit of the present invention

Figure 2 (a) is a graph of the different odd (Z _oo ) and even (Z _oe ) mode impedances of the present invention, and the scattering parameter |S ₁₁ | of the MWO simulation.

Fig. 2(b) is a graph showing the scattering parameters of the different odd (Z _oo ) and even (Z _oe ) mode impedances of the present invention and the MWO simulation.

Figure 3 shows the relationship between the capacitance value and |S ₂₁ | resonance frequency point (0.5 to 2 GHz).

Figure 4 (a) is an IE3D simulated scattering parameter |S ₁₁ | relationship diagram of different capacitance values of the present invention.

Figure 4 (b) is an IE3D simulated scattering parameter |S ₂₁ | relationship diagram of different capacitance values of the present invention.

Figure 5 is a schematic diagram of the circuit structure of the high frequency capacitance tester.

Figure 6 (a) is a graph showing the actual measurement of the scattering parameter |S ₁₁ |

Figure 6(b) is a graph showing the actual measurement of the scattering parameter |S ₂₁ | of different capacitance values of the present invention.

Figure 7 is a schematic diagram of actual measurement of different capacitance values and IE3D simulation of the present invention.

Annex 1 capacitance difference and |S ₂₁ | resonance frequency point relationship table.

Attachment 2 photo of the high frequency capacitance tester.

(C). . . Capacitor

(10). . . Substrate

(20). . . Coupled line set

(twenty one). . . First coupling line

(210). . . Signal input

(211). . . Signal output

(212) (213). . . Trapezoidal segment

(214) (215). . . Rectangular segment

(216) (217). . . Stud

(twenty two). . . Second coupling line

(220). . . Void

Claims (21)

A high-frequency capacitance tester with a coupled line structure includes a substrate and a coupling line group disposed on the substrate, and the coupling line group is composed of the following components: a first coupling line extending in a straight line, having a first One end and a second end, the first end is a signal input end, the second end is a signal output end; and the two positions are on the substrate and on the same line, and are parallel to the first coupling line and can a second coupling line, wherein each of the second coupling lines has a first end and a second end, the first ends of each of the second coupling lines are respectively grounded, and the second coupling line is respectively The second end is opposite to each other and has a gap for the capacitor to be tested, and the second end of the second coupling line is electrically connected to the two ends of the capacitor respectively; A vector network analyzer is connected to the signal input end and the signal output end to measure a scattering parameter data, and then the capacitance value of the capacitor to be tested is obtained from the resonance frequency of the scattering parameter data. The high frequency capacitance tester of claim 1, wherein the vector network analyzer includes an output port connected to the signal input terminal, and a signal connected to the signal output terminal. Receiving, the vector network analyzer outputs a measured signal from the output port to the second coupled line via the first coupled line, and receives the signal from the receiving port to measure the scattering parameter. The high frequency capacitance tester according to claim 1, wherein the circuit substrate has a thickness of 1.6 mm and a relative dielectric constant of 4.3, and is measured by the vector network analyzer, and then embedded in the One of the vector network analyzers, the LineGauge included in the electromagnetic simulation software IE3D, performs the impedance and electrical length (θ) of the coupled line group on the microstrip line structure ruler. Inch calculation. The high frequency capacitance tester according to claim 3, wherein the vector network analyzer performs circuit simulation with the electromagnetic simulation software IE3D, and the circuit simulates setting a center frequency of 2 GHz and the highest test frequency. The electrical length (θ) of the coupled line group is calculated by a quarter wavelength, and the electrical length (θ) is 90 degrees. The high frequency capacitance tester of claim 1, wherein a line width of the first coupling line and the second coupling line of the coupling line group is 1.36 mm, respectively, the first coupling line and the first The spacing of the two coupling lines is 0.43 mm, the lengths of the first coupling lines and the second coupling lines are respectively 21.42 mm, and the spacing of the second ends of the second coupling lines is 1 mm. The high frequency capacitance tester of claim 1, wherein the first end and the second end of the first coupling line respectively have an outwardly enlarged trapezoidal segment and have one at each of the enlarged ends A rectangular segment has a rectangular segment as the signal input end and another rectangular segment as the signal output terminal. The high frequency capacitance tester of claim 6, wherein each of the trapezoidal segments has a length of 2 mm, each of the rectangular segments has a length of 5 mm, and each of the rectangular segments has a line width of It is 3.1mm. The high frequency capacitance tester according to claim 1 or 6, wherein the signal input end and the signal output end are respectively connected with a conductive stud with an external thread for the measuring device screw Pick up. The high frequency capacitance tester according to claim 1, wherein the measuring device obtains the scattering parameter by using an impedance matrix of the coupled line and an odd and even mode analysis method, and the line of the coupled line group Width and line spacing from even mode impedance (Zoe), odd mode impedance (Zoo), the circuit base The relative dielectric constant of the board is determined by adjusting the reflection coefficient of the signal output end and the signal intensity of the signal input end. The high frequency capacitance tester according to claim 9, wherein the even mode impedance is 100 ohms, the odd mode impedance is 50 ohms, and the characteristic impedance of the signal input end and the signal output end are both 50 ohms. The high frequency capacitance tester of claim 1, wherein the two coupling lines are formed on the circuit substrate by printing or etching. A high frequency capacitance testing method for a coupled line structure, comprising the steps of: providing a coupling line group on a substrate, wherein a first coupling line extending in a straight line and two bits are in the same straight line and parallel to the first coupling line And a second coupling line capable of generating a coupling, the first coupling line has a first end and a second end, the first end is a signal input end, and the second end is a signal output end, each Each of the second coupling lines has a first end and a second end, the first ends of each of the second coupling lines are respectively grounded, and the second ends of the second coupling lines are opposite each other and have a gap Placing a capacitor to be tested in the gap, and electrically connecting the two ends of the capacitor to the second ends of the second coupling lines; and connecting a vector network analyzer to the signal input The end and the signal output end measure a scattering parameter data, and then obtain the capacitance value of the capacitor to be tested from the resonance frequency of the scattering parameter data. The high frequency capacitance test method of claim 12, wherein the vector network analyzer includes an output port connected to the signal input terminal, and a signal connected to the signal output terminal. Receiver, the vector network analyzer from the output埠 A signal for outputting a measurement is coupled to the second coupling line via the first coupling line, and the signal is received by the receiving port to measure the scattering parameter. The high frequency capacitance testing method according to claim 12, wherein the circuit substrate has a thickness of 1.6 mm and a relative dielectric constant of 4.3, and is measured by the vector network analyzer, and then embedded in the One of the vector network analyzers, the LineGauge included in the electromagnetic simulation software IE3D, calculates the impedance and electrical length (θ) of the coupled line group for the microstrip line structure size. The method for testing a high frequency capacitor according to claim 14, wherein the vector network analyzer performs circuit simulation using the electromagnetic simulation software IE3D, and the circuit simulates setting a center frequency of 2 GHz and the highest test frequency. The electrical length (θ) of the coupled line group is calculated by a quarter wavelength, and the electrical length (θ) is 90 degrees. The high frequency capacitance test method of claim 12, wherein a line width of the first coupling line and the second coupling line of the coupling line group is 1.36 mm, respectively, the first coupling line and the first The spacing of the two coupling lines is 0.43 mm, the lengths of the first coupling lines and the second coupling lines are respectively 21.42 mm, and the spacing of the second ends of the second coupling lines is 1 mm. The high frequency capacitance test method of claim 12, wherein the first end and the second end of the first coupling line respectively have an outwardly enlarged trapezoidal segment and have one at each of the enlarged ends A rectangular segment has a rectangular segment as the signal input end and another rectangular segment as the signal output terminal. The high frequency capacitance testing method of claim 17, wherein each of the trapezoidal segments has a length of 2 mm, each of the rectangular segments has a length of 5 mm, and each of the rectangular segments has a line width of It is 3.1mm. The high frequency capacitance test method of claim 12 or 17, wherein the signal input end and the signal output end are respectively connected with a conductive stud with a external thread for the measuring device screw Pick up. The high frequency capacitance testing method according to claim 12, wherein the measuring device determines the scattering parameter by using an impedance matrix of the coupled line and an odd and even mode analysis method, the line of the coupling line group The width and the line spacing are determined by the even mode impedance (Zoe), the odd mode impedance (Zoo), and the relative dielectric constant of the circuit board, thereby adjusting the reflection coefficient of the signal output end and the signal intensity of the signal input end. The high frequency capacitance test method according to claim 20, wherein the even mode impedance is 100 ohms, the odd mode impedance is 50 ohms, and the characteristic impedance of the signal input end and the signal output end are both 50 ohms.