JP3126220B2 - How to measure fringe volume - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fringe suitable for calibrating a one-port open standard or a low-capacity standard, or for calibrating a one-port connector or various adapters (for example, a four-terminal to one-port adapter). It relates to a method for measuring capacity.

[0002]

2. Description of the Related Art For example, measurement devices such as a network analyzer and an impedance analyzer require calibration using a standard device. 1 used for such purpose
Open or low-capacity standards on ports must themselves be properly calibrated. In addition, a four-terminal / one-port adapter is used for the measurement by the measuring device as described above. In this case, it is necessary to accurately calibrate the fringe capacity of the port part of the adapter.

When calibrating a capacitance standard or an open standard, the uncertainty is limited by the uncertainty of the fringe capacitance. Therefore, if the fringe volume can be measured with higher accuracy, the calibration accuracy of the standard device can be increased. For example, when calibrating a standard device of 10 pF, the fringe capacitance of the fixture having the test port structure is ± 0.0%.
If only the uncertainty of 1 pF is known, the calibration uncertainty is limited to 0.1%, but the fringe capacitance is ±
If the uncertainty of 0.001 pF is known, the uncertainty of the calibration of the above standard is improved to 0.01%.

Hereinafter, a conventional example of a method for measuring the fringe capacity will be described. FIG. 5 is a diagram illustrating an example of a method of measuring the fringe capacity. In the figure, the low pressure side port L of the capacity meter 1
A T-type adapter 4 for port-2 port conversion is connected. 2 on the side of the T-shaped adapter 4 which is different from the capacity meter 1
Connectors 6A and 6B are connected to the ports P _4A and P _4B via a coaxial cable 5, respectively. The coaxial cable 5 is a special one in which the end of the jacket is in an open state, and is not connected to the external conductor of each of the connectors 6A and 6B. Further, wires w _h and w _g are drawn out from the internal conductor h of the high-pressure side port H of the capacitance meter 1 and from the ground terminal g, respectively.

[0005] In this way, the outer conductor of the connector 6A of the wire w _h as first shown in the figure, the measurement of the electrostatic capacitance of the wire w _g while connected to the outer conductor of the connector 6B. The measurement result at this time is C ₁ , connector 6A
Let C _{f1 be} the fringe capacitance of C and C _A be the capacitance not including this fringe capacitance C _f1 .

## EQU2 ## The relationship C ₁ = C _A + C _f1 holds. Then, the connector wire w _h 6
The outer conductor of the B, to measure the capacitance of the wire w _g while connected to the outer conductor of the connector 6A. The measurement result at this time is C ₂ , the fringe capacitance of the connector 6B is C _f2 , and the capacitance not including the fringe capacitance C _f2 is C _B.
Then

## EQU3 ## The relationship C ₂ = C _B + C _f2 holds.

Further, measurement is performed by fitting the connectors 6A and 6B together. In this case, there is no fringe capacity. If the measurement result at this time is C ₃ , C ₃ is

## EQU4 ## It is expressed by C ₃ = C _A + C _B. From the above [Equation 2] to [Equation 4],

## _EQU5 ## C _f1 + C _f2 = C ₁ + C ₂ −C ₃ is derived, and the sum of the fringe capacities can be obtained.

However, in this method, although the sum of the fringe capacities can be obtained as described above, the value of each fringe capacity cannot be known. Therefore, both connectors 6
A and 6B have the same mechanical dimensions, and C _f1 = C _f2 (=
Assuming that C _f ), the above equation becomes

[6] can be modified as _{C f = (C 1 + C} 2 -C 3) / 2.

However, since this fringe capacitance C _f is an average of the fringe capacitances C _f1 and C _f2 for the connectors 6A and 6B, the uncertainty is on the order of 10 ^-3 pF (for example, ± 0.008 pF). Has a disadvantage that the value becomes considerably large. Also, there is a problem that the method described with reference to FIG. 5 cannot be used as it is for an adapter having a four-terminal-one-port configuration.

FIGS. 6A to 6C are diagrams showing another fringe capacitance measuring method. As shown in FIG.
The capacitance meter 1 has high and low voltage terminals H and L and a guard terminal guar.
d. The outer conductor and the inner conductor of the adapter 7 having one port are connected to H and L. Here, capacitance meter 1 is capacitive bridge is constituted by (a variable capacitor C _V, and galvanometer G, consisting of a transformer T having a signal source V _S to the primary side), galvanometer G is a low-voltage terminal L One end of the secondary side of the transformer T is connected to the high voltage terminal H, and the other end is connected to the low voltage terminal L via C _V. I have. When measuring the fringe capacitance port of the adapter 7, first, as shown in FIG. (B), connecting a coaxial connector 8 to the port P _7. Here, between the inner conductor 8a of the inner conductor 7a and the connector 8 port P ₇ is interposed the insulating disc 9, the guard terminal guard ground potential is connected to the inner conductor 8a of the connector 8 ing.

Here, a uniform electric field is formed in the space between the inner conductor and the outer conductor near the connection portion 10 between the port 7a and the connector 8. Therefore, the capacitance measured in this state is not affected by the fringe capacitance.

Next, as shown in FIG. 1C, with the connector 8 removed, the capacitance of the adapter 7 is measured. In this case, the measurement results may include fringe capacitance C _f. Therefore, from the capacitance measured when the connector 8 is connected shown in FIG. 6B, the measurement result of the capacitance measured when the connector 8 is removed shown in FIG. is subtracted, it is possible to determine the fringe capacitance C _f of the port P _7.

In the measuring methods shown in FIGS. 6A to 6C, when it is assumed that there is no influence of the fixture,
Although it can be measured at a stability of about ± 0.002 pF, there is a difference of 0.004 pF between the individual fringe capacitances, and the influence of the fixture is said to be 0.002 pF.

However, in this method, the influence of the insulating disk 9 is not clear, and this is an obstacle to obtaining the fringe capacitance. In addition, the measurement method of FIG. 6A has a disadvantage that it cannot be applied to a commercially available 4-port to 1-port adapter as in the case of FIG.
Further, in the specified state, the value is ± 0.002 pF (the actual measurement has a difference of 0.004 pF). However, in the case of an arbitrary fixture structure, it is considered that the stray capacity between the fixture and the connector is affected. There is also a problem that the uncertainty has not been clarified. Although details are omitted, as another method for obtaining the fringe capacity, a method of theoretically calculating by a finite element method or the like has also been proposed. Cannot be applied directly.

[0014]

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve the above-mentioned problems, and can reduce uncertainty and can be used for various types of terminal devices such as adapters. It is an object of the present invention to provide a method for measuring a fringe volume that is high.

[0015]

SUMMARY OF THE INVENTION The present invention has at least two coaxial terminal pairs and one port, wherein the inner conductor of one terminal pair of the coaxial terminal pair becomes the inner conductor of the port and the inner conductor of the other terminal pair. There are those used in the method of measuring the fringe capacitance C _f of the measured terminal device comprising respectively connected to the outer conductor of the port, in the measurement, and at least two coaxial terminal pair and one port, The inner conductor of one of the terminal pairs is connected to the inner conductor of the port, and the inner conductor of the other terminal pair is connected to the outer conductor of the port.
One terminal device for measuring capacitance is used.

The terminal device to be measured (for convenience, D
The following measurement is performed for all pairs selected from three terminal devices in total of UT) and two terminal devices for capacitance measurement (referred to as A and B for convenience).

(1) The following measurements are performed on the terminal devices A and B. (A) First, the ports are disconnected from each other, the inner conductors of each pair of shaft terminals connected to the outer conductor of each port are connected to each other, and the pair of shaft terminals connected to the inner conductor of each port are connected. Connect the internal conductors to each other to
The outer conductor between the capacitance C ₁₁ is measured. Here, the capacitance C ₁₁ is included fringe capacitance both ports. That is, the terminal device A, respectively C _fA the fringe capacitance ports B, C _fB, respectively the capacity excluding the fringe capacitance C _A, when the C _B,

## _EQU7 ## C ₁₁ = C _A + C _B + C _fA + C _fB

(B) Next, the ports are connected to each other, the inner conductors of the pair of coaxial terminals connected to the outer conductor of each port are connected to each other, and the coaxial terminals connected to the inner conductor of each port are connected. connect each inner conductor between the pair of measuring the inner conductor / outer conductor between the capacitance C ₁₂ of the port. Here, the capacitance C ₁₂ is fringe capacitance C _fA of the ports, C _fB is not included. That is,

## EQU8 ## The relationship of C ₁₂ = C _A + C _B holds.

(C) From these measurement results, C ₁₁ -C ₁₂
, The sum of the fringe capacitance of each port of the terminal device for capacitance measurement,

## _EQU9 ## C ₁ = C _fA + C _fB can be obtained.

(2) The same measurement as in (1) is performed for the pair of terminal devices A and DUT. In the same manner as (a) (1) (a ), to measure the inner conductor / outer conductor between the electrostatic capacitance C ₂₁ in a case where the port between a non-connected state. Here, the capacitance C ₂₁ is included fringe capacitance both ports. When the fringe capacitance of the terminal device DUT is C _fX and the capacitance excluding the fringe capacitance is C _X ,

## _EQU10 ## C ₂₁ = C _A + C _X + C _fA + C _fX

[0021] (b) Next, in the same manner as in (1) (b), measuring the inner conductor / outer conductor between the capacitance C ₂₂ of the port when the port together with the connection state. Here, the fringe capacitances C _fA and C _{fX of} both ports are included in the capacitance C _22.
Is not included. That is,

## EQU11 ## C ₂₂ = C _A + C _X

(C) From these measurement results, C ₂₁ -C _{22
Is obtained} , the sum of the fringe capacitance C _fA of the port of the terminal device for capacitance measurement and the fringe capacitance C _fX of the terminal device to be measured,

Equation 12] can be obtained _{C 2 = C fA + C fX} .

(3) The same measurement as in (2) is performed for the pair of terminal devices B and DUT. In the same manner as (a) (2) (a ), to measure the capacitance C ₃₁ between the inner conductor / outer conductor when the port together disconnected. here,

## EQU13 ## C ₃₁ = C _B + C _X + C _fB + C _fX

Next (b), (2) ( b) and in the same manner, to measure the inner conductor / outer conductor between the capacitance C ₃₂ of the port when the port together with the connection state. That is,

## EQU14 ## C ₃₂ = C _B + C _X

(C) From these measurement results, C ₃₁ -C _{32
Is obtained} , the sum of the fringe capacitance C _fB of the port of the terminal device for capacitance measurement and the fringe capacitance C _fX of the terminal device to be measured,

## _EQU15 ## C ₃ = C _fB + C _fx can be obtained.

(4) C ₁ , C ₂ ,
From C _3,

## _EQU16 ## C _fx is obtained from C _fx = (C ₂ + C ₃ -C ₁ ) / 2.

[0027]

FIG. 1 is a schematic diagram showing a fringe capacitance (measurement surface is indicated by Sm) measuring system used in the measuring method of the present invention. The measurement system shown in FIG. 1 includes a capacitance meter 1 and two terminal devices 2A and 2B for measuring capacitance. As the capacitance meter 1, one having sufficient accuracy (particularly linearity) at the measurement frequency is used. The measurement signal from the voltage signal source 11 is output from the high-voltage measurement port H, and the current is supplied to the low-voltage measurement port L. A total of 12 are connected. The high-pressure side measurement port H and the low-pressure side measurement port L of the capacity meter 1 are connected via a cable (indicated by a broken line in the figure).
It is connected to the terminal device 2A, 2B for capacitance measurement or the terminal device 3 to be measured.

In FIG. 1, a two-port capacity meter is used as the capacity meter 1, but a four-port capacity meter can also be used. That is, when the capacity meter 1 has four ports (that is, four terminal pairs) of the high voltage side and the low voltage side voltage measurement ports H _pot and L _pot and the high voltage side and the low voltage side current measurement ports H _cur and L _cur. H _pot and H _cur and L _pot and L _cur can be connected to use the capacity meter as a two-port capacity meter. It should be noted that although a one-port capacity meter can be used in theory, it is actually necessary to bend the cable. Therefore, it is preferable to use a capacity meter with a guard in consideration of stability.

The capacitance measuring terminal device 2A of FIG, 2B and the measured terminal device 3 are both a 4 pin-on-1 port adapter, four coaxial terminals pair _{H c, H p, L p} , L c And 1
And two ports P _2A , P _2B , and P ₃ , respectively, and one of the coaxial terminal pairs (in the figure, the high-voltage side voltage terminal pair H
_p ) is the internal conductor of each of the ports P _2A , P _2B , P ₃ , and the internal conductor of the other terminal pair (the low-voltage side voltage terminal pair L _p ) is the port P _2A , P _2B , P ₃ external conductors.

[0030] In this embodiment, although the terminal voltage measuring terminal pair vs. H _p and L _p of terminal devices connected to the capacitance meter 1, high-pressure side, the low-pressure-side current measuring terminal H _c, using L _c You can also. Although FIG. 1 illustrates a 4-terminal pair to 1-port adapter, the present invention is not limited to this. For example, at least a 2-terminal pair and a 1-port adapter such as an adapter having a 3-terminal structure (a 2-terminal pair structure). It can be used if it has

Further, as shown in FIG. 2, by connecting a 1-port to 1-port adapter 3 'to be measured to the terminal device 3 to be measured, the fringe capacitance at the tip of the adapter 3' ( The measurement surface is indicated by Sm '). In FIG. 1, in order to minimize the influence of external induction, the high-voltage side measurement port H of the capacitance meter 1 and the low-voltage side terminal L _{p of the} terminal device (the terminal to which the external conductor of the port of the terminal device is connected) ) connects the, and connects the high-voltage side terminal H _p of the low-pressure side measuring port L and the terminal device capacity meter (terminal internal conductor is connected to the port terminal device).

Hereinafter, a procedure for measuring the fringe capacitance of the terminal device 3 to be measured by the system shown in FIG. 1 will be described. First, as shown in FIG. 3, terminal devices 2A and 2
Select B together in pairs, the port P _2A, a P _2B together is disconnected, measures the inner conductor / outer conductor between the capacitance C ₁₁ of the port. The capacitance C11 is the sum of the fringe capacitances C _fA and C _{fB of} both ports and the capacitances C _A and C _B not including the fringe capacitances C _fA and C _fB , that is,

## _EQU17 ## Measured (indicated) by a capacitance meter as C ₁₁ = C _A + C _B + C _fA + C _fB .

[0033] Then, then as shown in FIG. 4, the port together with the connection state, measures an inner conductor / outer conductor between the capacitance C ₁₂ of the port. In this measurement, since fringe capacitances C _fA and C _fB do not exist, C ₁₂ is the capacitance C _A , C _B
The sum of

(18) Measured (indicated) by a capacitance meter as C ₁₂ = C _A + C _B. By taking the difference between these measurements C _11, C _12, the sum C ₁ of fringe capacitance of each port of the terminal device paired are determined _{(i.e., C 1 = C 11 -C 12} = C fA + C _fB ).

Next, although not shown, a terminal device 2A for capacitance measurement and a terminal device 3 to be measured are selected as a pair, and a connection state similar to FIG. to measure the C _21. Port P _{3 of the} terminal device to be measured
_Let C _{fX be} the fringe capacitance of C _fx , and C _X be the capacitance not containing the fringe capacitance C _fX , C ₂₁ is

## _EQU19 ## Measured (indicated) by a capacitance meter as C ₂₁ = C _A + C _X + C _fA + C _fX . Then, the terminal device 2A for capacitance measurement and the terminal device 3 to be measured are
In the same connection state as to measure the capacitance C ₂₂ without the fringe capacitance C _fA, C _fX. Where C ₂₂ is

## EQU20 ## Measured (indicated) by a capacitance meter as C ₂₂ = C _A + C _X. As above,
By taking the difference between these measurement results C ₂₁ and C ₂₂ , the sum C ₂ of the fringe capacitances of the ports of the paired terminal devices is obtained (that is, C ₂ = C ₂₁ −C ₂₁ = C _fA +).
_CfX ).

Further, although not shown, the terminal device 2B for capacitance measurement and the terminal device 3 to be measured are selected as a pair, and in the same manner as described above, the electrostatic capacitance C ₃₁ including the fringe capacitances C _fB and C _fX.
And the capacitance C not including the fringe capacitances C _fB and C _fX.
32 were measured, by taking these differences, each port P _2B terminal device 2B, 3 were paired, the sum C ₃ of fringe capacitance P ₃ are determined (i.e., C ₃ = C ₃₂ -C ₃₁ = C _fB
+ _CfX ).

The C ₁ , C ₂ and C determined as described above
_{From 3} ,

## _EQU21 ## C _fx = (C ₂ + C ₃ -C ₁ ) / 2 is obtained. As the uncertainty of the fringe capacitance calibration, the GR900 connector ((General Radio Catalo
g)), an uncertainty of ± 0.002 pF was realized at the 99.7% confidence level with RSS error accumulation.

[0037]

As described above, the measuring method of the present invention
The following effects can be obtained. (1) The uncertainty of the fringe capacitance measurement can be improved by about one digit as compared with the related art. In addition, since the fringe capacity of each port can be individually obtained, highly accurate calibration can be performed. (2) The fringe capacitance can be measured for any type of terminal pair device such as a commercially available adapter, and a highly versatile measurement method can be provided. At the same time, calibration with an arbitrary fixture becomes possible. (3) Since the insulating disk is not used in the measurement, the measurement accuracy does not deteriorate when the disk is used.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a system used for a measurement method of the present invention.

FIG. 2 is a diagram showing a case where a connector to be measured is connected to the terminal device to be measured shown in FIG. 1;

FIG. 3 is a diagram for explaining the measurement method of the present invention using the system of FIG. 1, and is an explanatory diagram showing a state where capacitance is measured with a port of a terminal-to-device disconnected.

FIG. 4 is a diagram for explaining a measurement method of the present invention using the system of FIG. 1, and is an explanatory diagram showing a state where capacitance is measured with a port of a terminal-to-device connected.

FIG. 5 is a diagram showing a conventional fringe capacitance measuring method.

6A and 6B are views showing a conventional fringe capacitance measuring method, wherein FIG. 6A is an overall view of a measuring apparatus, FIG. 6B is a view showing a state where a connector is connected to a port of an adapter, and FIG. It is a figure showing signs that a connector was removed.

[Explanation of symbols]

1 capacity meter 2A, 2B capacitance measuring terminal apparatus 3 under test terminal device L, H capacity meter measurement ports P _2A, P _2B port _{H c, H p, L c} , the measurement surface of the L _p terminal pair Sm fringe capacitance

Claims (1)

(57) [Claims] At least two coaxial terminal pairs and one port are provided. An inner conductor of one terminal pair of the two terminal pairs is an inner conductor of the port, and an inner conductor of the other terminal pair is an outer conductor of the port. A method for measuring a fringe capacitance of a terminal device connected to a conductor, comprising: at least two coaxial terminal pairs and one port;
Using two terminal devices for measuring capacitance, the inner conductor of one terminal pair of the two terminal pairs is connected to the inner conductor of the port, and the inner conductor of the other terminal pair is connected to the outer conductor of the port. For all pairs selected from the three terminal devices, the terminal device to be used and the terminal device for measuring both capacitances, the ports are disconnected from each other, and the inner conductors of the terminal pair connected to the outer conductor of each port are connected. Connect and connect the internal conductors of the terminal pair connected to the internal conductor of each port to connect the internal conductor / external conductor capacitance of the port to the external conductor of each port. While connecting the internal conductors of the terminal pair
The internal conductor of the terminal pair connected to the internal conductor of each port is connected to each other to obtain the capacitance between the internal conductor / external conductor of the port,
Each of them is measured, and by taking the difference between these measurement results, the sum of the fringe capacitance of each port of the paired terminal devices is obtained, and the fringe capacitance of the terminal device to be measured is obtained by the following equation. How to measure fringe capacity. ## EQU1 ## C _fx = (C ₂ + C ₃ -C ₁ ) / 2 C _fx : Fringe capacitance of the terminal device to be measured C ₁ : Sum of the fringe capacitance of each port performed for a pair of two capacitance measuring terminal devices C ₂ : Sum of the fringe capacitance of each port performed for one pair of the capacitance measuring terminal device and the terminal device to be measured C ₃ : The sum of the fringe capacitance of each port performed for the other pair of the capacitance measuring terminal device and the measured terminal device Sum of fringe capacity