JP2001281282A - Probe for impedance measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a probe for impedance measurement which can reduce reflection at a signal input point by having its impedance matched with a coaxial cable connected to an impedance measuring instrument. SOLUTION: This probe is equipped with a printed wiring board 3 which has a signal conductor 1 and a ground conductor 2 formed, a signal input pin 6 which is electrically connected to the signal conductor 1 and can be brought into contact with a measured circuit 5 on a circuit board 4, and a ground contact pin 8 which is electrically connected to the ground conductor 2 and can be brought into contact with a ground circuit 7 of the circuit board 4. This is concerned with a probe A for impedance measurement which is electrically connected to the impedance measuring instrument by a coaxial cable 9. The probe is formed matching the impedance of the coaxial cable 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe for measuring impedance used for measuring the impedance of a circuit board such as a multilayer printed wiring board.

[0002]

2. Description of the Related Art In a circuit board used for electronic equipment, etc.,
The impedance matching between a circuit provided on a circuit board and a signal transmitted through the circuit is performed. Particularly, in the case of a circuit for transmitting a high-frequency signal (high-speed signal), this impedance matching is important. is there. Therefore, the circuit of the circuit board is designed so that impedance matching with a signal to be transmitted can be obtained, and the circuit board is checked whether the impedance (value) of the circuit is within an allowable range from the design value. Products that have been commercialized and whose circuit impedance falls outside a certain allowable range are discarded as defective products.

Conventionally, when measuring the impedance of a circuit on a circuit board, mainly TDR (Time Domain Ref) is used.
rectrometry) method is used. In this method, a pulse or step signal is transmitted to a transmission circuit including a signal circuit (circuit under test) whose impedance is to be measured and a reference ground circuit, and a reflection signal in the transmission circuit is detected and a reflection signal is detected. The impedance value of the transmission circuit (circuit under test) is obtained by using the reflection coefficient obtained from the above.

For measuring the impedance of a circuit board, an SMA
A method of directly soldering a coaxial connector such as a connector to a circuit to be measured and a method of using a contact-type coaxial probe are generally practiced. The former can reduce the measurement error due to the reflection of the signal input point, but it is a so-called destructive test because there is contamination due to soldering of the coaxial connector. In the latter case, the impedance is matched using a coaxial cable and a coaxial pin, and the pitch between the signal conductor and the ground conductor and the position of the tip of the coaxial pin are fixed.

[0005]

In the method of measuring the impedance as described above, the method of directly soldering a coaxial connector to a circuit to be measured requires the circuit board to be broken or stained by soldering. May reduce the value of the product. Further, in the method using a coaxial probe using a coaxial pin extended from a coaxial cable, the distance (pitch) between the signal conductor and the ground conductor is fixed, and the coaxial pin has no spring function and has large reflection at the time of signal input. In addition, there was a problem in terms of technical and usage methods, such as high price.

The present invention has been made in view of the above points, and an impedance measuring probe capable of reducing reflection at a signal input point by matching impedance with a coaxial cable connected to an impedance measuring device. It is intended to provide.

[0007]

A probe A for impedance measurement according to a first aspect of the present invention is electrically connected to a printed wiring board 3 on which a signal conductor 1 and a ground conductor 2 are formed, and to the signal conductor 1. And the circuit under test 5 on the circuit board 4
And a ground contact pin 8 that is electrically connected to the ground conductor 2 and can contact the ground circuit 7 of the circuit board 4. Measuring impedance probe A connected to the coaxial cable 9
Characterized by being formed so as to match the impedance of.

A probe A for impedance measurement according to a second aspect of the present invention, in addition to the configuration of the first aspect, comprises a signal input pin 6 and a ground contact pin 8 formed by spring-type contact pins. Signal input pin 6 to circuit under test 5
The contact pins can be extended and retracted so that the tips of the signal input pins 6 and the ground contact pins 8 recede to the end surface of the printed wiring board 3 when the contact is made and when the ground contact pins 8 contact the ground circuit 7 of the circuit board 4. It is characterized by being formed in.

According to a third aspect of the present invention, there is provided an impedance measuring probe A in which the printed wiring board 3 is formed in any one of a microstrip structure, a strip structure and a coplanar structure in addition to the structure of the first or second aspect. It is characterized by becoming.

According to a fourth aspect of the present invention, there is provided an impedance measuring probe according to any one of the first to third aspects, wherein the printed wiring board is formed by using a material having a low dielectric constant and a low dielectric loss tangent. It is characterized by comprising.

According to a fifth aspect of the present invention, there is provided an impedance measuring probe A according to the first aspect of the present invention, further comprising an insulating layer of the printed wiring board 3 which is matched with the impedance of the coaxial cable 9. The thickness and the position of the ground contact pin 8 are formed so as to be adjustable.

The impedance measuring probe A according to a sixth aspect of the present invention, in addition to the configuration according to any one of the first to fifth aspects, controls the length of the wiring of the signal conductor 1 so as to change the resonance frequency and pass therethrough. The frequency characteristic of the signal to be controlled is formed so as to be controllable.

According to a seventh aspect of the present invention, there is provided an impedance measuring probe A according to any one of the first to sixth aspects, wherein a signal conductor 1, a ground conductor 2, a signal input pin 6, and a ground contact pin 8 are provided. It is characterized by being plated with gold.

[0014]

Embodiments of the present invention will be described below.

FIGS. 1A to 1C show an example of the present invention. The printed wiring board 3 is formed by providing the signal conductor 1 on one surface of the insulating layer 10 and the ground conductor 2 on the other surface. The signal conductor 1 is formed in an elongated line in the front-rear direction of the printed wiring board 3, and the ground conductor 2 is formed on a solid surface covering the entire surface of one surface of the printed wiring board 3. That is, the printed wiring board 3
Are formed in a microstrip (line) structure. By forming the printed wiring board 3 in a microstrip structure in this way, the upper side (surface side) of the signal input pins 6 arranged on the surface of the signal conductor 1 becomes an air layer, and the effective dielectric constant of the probe A itself. As a result, the transmission delay and transmission loss of the impedance measurement signal passing through the probe A can be reduced, and the measurement accuracy can be improved.

The insulating layer 10 between the signal conductor 1 and the ground conductor 2 is formed of a cured resin material. The resin material used to form the insulating layer 10 has a low dielectric constant and a low dielectric loss tangent. It is preferable to use a fluororesin material such as PTEF (polytetrafluoroethylene), which is a material for the above. By thus forming the insulating layer 10 of the printed wiring board 3 with a material having a low dielectric constant and a low dielectric loss tangent, it is possible to reduce delay and dielectric loss of a high-frequency signal passing through the signal conductor 1. When the insulating layer 10 is formed of a fluororesin material, the effective dielectric constant becomes 1.8 due to a synergistic effect with the effect of the air layer, which is a characteristic of the printed wiring board 3 having the microstrip structure. The signal speed passing through A is 2 compared to a conventional coaxial probe.
Can be increased by 0%.

A signal input pin 6 is provided on the surface of the signal conductor 1, and a ground contact pin 8 is provided on the surface of the ground conductor 2. The signal input pin 6 and the ground contact pin 8 can be formed by spring-type contact pins as shown in FIG. The contact pin is formed of a conductive metal such as copper or nickel, and has a needle-shaped pin body 21 having a sharp tip, a cylindrical socket 22 having an open front surface and a closed rear surface, and a coil spring. A spring 23 is provided, and these are formed integrally. The pin body 21 is inserted into the socket 22 with its tip protruding from the front opening of the socket 22.
The socket 22 is formed in a state where the socket 22 covers other than the front end portion. The spring 23 is provided between the rear end of the pin body 21 and the bottom of the socket 22. Further, the pin body 21 is formed so as to be slidable in the front-rear direction with respect to the socket 22. The pin body 21 is connected to the socket 2
2 is formed so as to be removable. In addition, when the outer peripheral surface of the pin main body 21 and the inner peripheral surface of the socket 22 come into contact with each other, the pin main body 21 and the socket 22 are electrically connected.

The above-mentioned contact pins are formed such that the pin body 21 is slidably movable in the front-rear direction with respect to the socket 22. Is formed so as to be able to expand and contract with a state in which it is inserted into the socket 22 deeply against the elastic force of the above. Further, since the spring 23 is provided between the rear end of the pin body 21 and the bottom surface of the socket 22, the contact pin has a cushioning property. It can be brought into close contact with the measurement circuit 5 and the ground circuit 7 to be elastically contacted. As a result, the circuit under test 5 and the ground circuit 7 by the contact of the signal input pin 6 and the ground contact pin 8
This can reduce the damage (damage) and improve the contact of the signal input pin 6 and the ground contact pin 8 with the circuit under test 5 and the ground circuit 7.

The signal input pins 6 are arranged along the surface of the signal conductor 1 and the sockets 22 of the signal input pins 6 are fixed to the surface of the signal conductor 1 by soldering. 1 is attached to the surface. The ground contact pins 8 are arranged along the surface of the ground conductor 2 and the sockets 22 of the ground contact pins 8 are fixed to the surface of the ground conductor 2 by soldering, so that the ground contact pins 8 Attached to. The distal ends of the pin bodies 21 of the signal input pins 6 and the ground contact pins 8 attached to the printed wiring board 3 in this manner are arranged so as to protrude forward from the front end of the printed wiring board 3. In addition, the tips of the pin body 21 of the signal input pin 6 and the ground contact pin 8 protruding forward from the front end of the printed wiring board 3 come into contact with the circuit under test 5 or the ground circuit 7 of the circuit board 4 and are pressed. Thereby, it is formed so as to retreat to the front end of the printed wiring board 3. Further, the pin body 2 of the signal input pin 6 and the ground contact pin 8 retreated to the front end of the printed wiring board 3
The leading end of the printed wiring board 1 is advanced by the elastic force of the spring 23 to a position protruding forward from the front end of the printed wiring board 3 by releasing the pressing of the circuit board 4 due to the contact with the circuit to be measured 5 or the ground circuit 7. I do.

1 (a) to 1 (c), the signal input pins 6 are arranged substantially at the center of the printed wiring board 3 in the width direction, and the ground contact pins 8 are shifted from the center of the printed wiring board 3 in the width direction. However, the arrangement is not limited to this, and FIG.
As shown in (c), both the signal input pin 6 and the ground contact pin 8 may be arranged substantially at the center of the printed wiring board 3 in the width direction.

At the rear end of the printed wiring board 3, a coaxial connector 30 such as an SMA connector is provided. The inner conductor 31 of the coaxial connector 30 is electrically connected to the signal conductor 1 of the printed wiring board 3, and the outer conductor 32 of the coaxial connector 30 is electrically connected to the ground conductor 2 of the printed wiring board 3. Further, it is preferable that the signal conductor 1, the ground conductor 2, the signal input pin 6, and the ground contact pin 8 are covered with gold plating so that even if the number of times of impedance measurement is about 10,000, the signal input pin 6
In addition, the wear of the tip of the ground contact pin 8 can be reduced and the generation of rust can be prevented.
Further, the printed wiring board 3 can be covered with a cover made of ABS resin or the like.

The impedance measuring probe A of the present invention formed as described above is electrically connected via a coaxial cable 9 to an impedance measuring instrument provided with an oscilloscope and an input signal generator. When connecting the coaxial cable 9 to the impedance measuring probe A, as shown in FIG. 4, one end of the coaxial cable 9 is connected to the coaxial connector 30 and the center conductor at one end of the coaxial cable 9 is connected to the internal conductor of the coaxial connector 30. 31 and an outer conductor at one end of the coaxial cable 9 is electrically connected to an outer conductor 32 of the coaxial connector 30.

The present invention is formed so that the impedance is matched with the coaxial cable 9 to be connected, so that a stable impedance measurement can be performed. The present invention uses the coaxial cable 9
Printed circuit board 3
The thickness of the insulating layer 10 (shown by t in the drawing), the width of the signal conductor 1, the diameter of the signal input pin 6 and the ground contact pin 8, and the material of the insulating layer 10 are taken into consideration. For example, since the impedance of the coaxial cable 9 is usually 50Ω, the impedance of the present invention is also designed to be 50Ω (± 5%). In this case, the thickness of the insulating layer 10 of the printed wiring board 3 is 0.5 mm, The width of the conductor 1 is 1.2 mm,
The diameter of the signal input pin 6 and the ground contact pin 8 is 0.45
mm, and the material of the insulating layer 10 can be formed of a fluororesin material (relative permittivity εr = 2.6 at 1 MHz). Of course, it is also possible to design an impedance other than 50Ω as necessary.

Probe A for Impedance Measurement of the Present Invention
Can be used for characteristic impedance measurement by the TDR method or the like. In this case, a circuit-under-measurement contact portion 35 electrically connected to an end of the circuit-under-measurement 5 and a ground circuit contact portion 36 electrically connected to an end of the ground circuit 7 are provided on the surface of the circuit board 4. As shown in FIG. 5, the tip of the signal input pin 6 is brought into contact with the contact portion 35 to be measured, and the tip of the ground contact pin 8 is brought into contact with the ground circuit contact portion 36.
The end of the circuit under test 5 and the contact section 35 to be measured, and the end of the ground circuit 7 and the ground circuit contact section 36
Are connected by through-hole plating 37 or the like.
The circuit under test 5 may be a signal circuit to which a signal is actually transmitted, or may be a test pattern for measuring impedance.

In the present invention, the signal for impedance measurement generated by the impedance measuring device is applied to the signal input pin 6 through the center conductor of the coaxial cable 9, the inner conductor 31 of the coaxial connector 30, and the signal conductor 1 of the printed wiring board 3. A signal for impedance measurement is supplied to the circuit under test 5 from the distal end of the signal input pin 6. As described above, the impedance measurement probe A of the present invention matches the impedance of the coaxial cable 9 with the impedance measurement probe A. Therefore, reflection at a signal input point, which is a contact point between the tip of the signal input pin 6 and the circuit-under-test contact portion 35 of the circuit-under-test 5, can be reduced. The method can improve the measurement performance of impedance as compared with the soldering method or the probe having the coaxial structure. Further, the impedance measuring probe of the present invention can be formed using existing materials, and can be manufactured at low cost in a short time.

As described above, when the signal input pin 6 is pressed to make contact with the circuit contact portion 35 to be measured and the ground contact pin 8 is brought into contact with the ground circuit contact portion 36, the tip of the signal input pin 6 and the ground contact pin 8 are pressed. Is retracted to the front end of the printed wiring board 3, but the signal input pin 6 and the ground contact pin 8 have springs 23.
, The tip of the signal input pin 6 and the tip of the ground contact pin 8 are elastically adhered to the measured circuit contact portion 35 and the ground circuit contact portion 36 with cushioning properties. As a result, the tip of the signal input pin 6 and the ground contact pin 8 do not leave a scratch on the circuit board 4 as a product during impedance measurement and have sufficient pressure.
The impedance controlled portion at the tip of the contact can be brought into contact with the circuit contact portion 35 to be measured or the ground circuit contact portion 36 to reduce input reflection due to the presence of a discontinuity in impedance when a signal for impedance measurement is input. Thus, the disturbance of the waveform obtained by the measurement can be reduced.

FIG. 6A shows a waveform obtained when impedance is measured using the present invention, and FIG. 6B shows a waveform obtained when impedance is measured using a conventional probe. The vertical axis has a voltage scale, and the horizontal axis has a time scale. As is clear from FIG. 6A, the impedance measuring probe A of the present invention hardly causes reflection at the time of signal input (portion B in the graph), but the conventional probe of FIG. Reflection occurs at the time of input (portion C in the graph). As described above, in the present invention, the stability of the waveform obtained when measuring the impedance is excellent. The peak impedance of the reflection point at the signal input portion in the conventional probe shown in FIG. 6B was 112Ω, but the reflection point at the signal input portion of the probe A of the present invention shown in FIG. Had a peak impedance of 53.3Ω, and the reflection was reduced.

The distance (pitch) between the tip of the signal input pin 6 and the tip of the ground contact pin 8 is determined by the distance between the measured circuit contact 35 provided on the circuit board 4 and the ground circuit contact 36. Although the distance is set, the distance between the circuit contact portion 35 to be measured and the ground circuit contact portion 36 is different for each circuit board 4, so that the distance between the tip of the signal input pin 6 and the tip of the ground contact pin 8 for each circuit board 4 However, a conventional probe having a fixed pin pitch cannot correspond to various circuit boards 4 having different distances between the circuit contact portion 35 to be measured and the ground circuit contact portion 36. Therefore, in the present invention, the thickness of the insulating layer 10 of the printed wiring board 3 is selected, and the position of the ground contact pin 8 is finely adjusted.
In this state, the distance between the tip of the signal input pin 6 and the tip of the ground contact pin 8 can be changed in a state of matching with the impedance of the circuit contact part 3 to be measured.
5 can be flexibly adapted to various (multi-pitch) circuit boards 4 having different distances from the ground circuit contact portion 36. In FIGS. 1A to 1C, the distance P between the tip of the signal input pin 6 and the tip of the ground contact pin 8 is set to 2.54 mm, but the printed wiring board 3 having a microstrip structure is used. The distance P between the tip of the signal input pin 6 and the tip of the ground contact pin 8
Can be set to 1.27 mm or more.

In general, a signal transmission line having a length causes a reduction in a passing signal due to its resonance and transmission loss.
In the present invention, the resonance and the transmission loss
Is determined by the length (wiring length) of the signal conductor 1 and the inner conductor 31 of the coaxial connector 30. By controlling these wiring lengths, the frequency band of the impedance measurement signal passing through the probe A of the present invention is controlled. can do.
In the present invention, by controlling the length (wiring length) of the signal conductor 1 of the printed wiring board 3 and the internal conductor 31 of the coaxial connector 30, the influence of resonance and transmission loss is reduced to a level at which impedance can be measured. Is what it is.
For example, the wiring length from the coaxial connector 30 to the front end of the signal input pin 6 retreated to the front end of the printed wiring board 3 is 2
When the distance is set to 5 mm, when a signal for impedance measurement of 12 GHz is used, as shown in the graph of FIG.
Although the attenuation characteristic of 5 dB is confirmed, since the input signal for impedance measurement is usually set to about 10 GHz,
It is not affected by resonance and transmission loss, and has a signal passing characteristic that allows sufficient impedance measurement.

FIGS. 8A to 8C show another embodiment. The probe A for impedance measurement uses a printed wiring board 3 having a strip (line) structure. That is, the signal conductor 1 of the printed wiring board 3
Are the internal signal conductors 1a arranged inside the insulating layer 10.
And a front signal conductor 1b disposed at the front of one surface of the insulating layer 10 and a rear signal conductor 1c disposed at the rear of the one surface of the insulating layer 10. The front end of the first signal conductor 1a, the rear end of the front signal conductor 1b, and the rear end of the internal signal conductor 1a and the front end of the rear signal conductor 1c are connected by through holes (plating) 40 such as BVH. The signal input pins 6 are fixedly provided on the surface of the front signal conductor 1b. Other configurations are formed in the same manner as in the above embodiment.

As described above, by using the printed wiring board 3 having a strip structure, the area of the signal conductor 1 exposed on the surface of the printed wiring board 3 is reduced so that the signal conductor 1 is not directly touched by hand. It is possible,
It can prevent destruction due to static electricity.

FIGS. 9A to 9C show another embodiment. The probe A for impedance measurement uses a printed wiring board 3 having a coplanar (coplanar) structure. That is, the printed wiring board 3 shown in FIGS. 3A to 3C is formed by further providing a surface-side ground conductor 2a on one surface of the insulating layer 10 on which the signal conductor 1 is formed. The surface-side ground conductor 2a is formed on both sides of the signal conductor 1, and is connected to the ground conductor 2 on the other surface of the insulating layer 10 by through holes (plating) 40 such as BVH. The ground contact pin 8 is fixedly provided on the surface of the front-side ground conductor 2a. Other configurations are formed in the same manner as in the above embodiment.

As described above, by using the coplanar structure as the printed wiring board 3, the signal input pins 6 are provided.
The distance between the tip of the ground contact pin 8 and the tip of
The pitch can be set to a narrow pitch of 5 mm. As a result, if the distance between the circuit contact portion 35 to be measured provided on the circuit board 4 and the ground circuit contact portion 36 is 0.5 mm or more, impedance measurement becomes possible. It can be sufficiently applied to inspection of a general circuit board 4.

[0034]

As described above, according to the first aspect of the present invention, the printed wiring board on which the signal conductor and the ground conductor are formed is electrically connected to the signal conductor and is in contact with the circuit to be measured on the circuit board. An impedance measuring probe, comprising a signal input pin capable of being connected to the ground measuring circuit and a ground contact pin electrically connected to a ground conductor and capable of contacting a ground circuit of a circuit board. Since the impedance is matched to the impedance of the coaxial cable, the impedance is matched with the coaxial cable connected to the impedance measuring device, and the reflection at the signal input point can be reduced. It can be performed with high accuracy.

Further, according to a second aspect of the present invention, the signal input pin and the ground contact pin are formed by spring-type contact pins, and when the signal input pin contacts the circuit to be measured on the circuit board and when the ground of the circuit board is grounded. The contact pins are formed to be extendable so that the tips of the signal input pins and the ground contact pins recede to the end surface of the printed wiring board when the circuit contacts the ground contact pins, so that the reflection at the signal input point is further reduced. Thus, the impedance can be measured with higher accuracy. Further, the circuit board can be prevented from being damaged by the cushioning property of the signal input pin and the ground contact pin by the spring type.

According to the invention of claim 3 of the present invention, the printed wiring board is formed by any one of a microstrip structure, a strip structure, and a coplanar structure.
It is capable of transmitting an input signal at high speed and of a low loss type. In addition, by using a printed wiring board having a strip structure, it is possible to prevent electrostatic destruction. By using the printed wiring board, the interval between the signal input pin and the ground contact pin can be made narrower.

According to the invention of claim 4 of the present invention, since the printed wiring board is formed by using a material having a low dielectric constant and a low dielectric loss tangent, an input signal can be transmitted at a high speed.

According to the invention of claim 5 of the present invention, the thickness of the insulating layer of the printed wiring board and the position of the ground contact pin are formed so as to be adjustable while matching the impedance of the coaxial cable. The distance between the tip of the ground contact pin and the tip of the ground contact pin can be changed, and it can be flexibly adapted to various circuit boards where the distance between the part where the tip of the signal input pin contacts and the part where the tip of the ground contact pin contacts is different. Can be done.

According to the invention of claim 6 of the present invention, by controlling the wiring length of the signal conductor to change the resonance frequency so as to control the frequency characteristic of the signal passing therethrough, the influence of resonance and transmission loss is obtained. Can be reduced to a level at which impedance measurement can be performed, and stable impedance measurement can be performed.

According to the seventh aspect of the present invention, the signal conductor, the ground conductor, the signal input pin, and the ground contact pin are plated with gold, so that wear of the tips of the signal input pin and the ground contact pin is reduced. And rust can be prevented.

[Brief description of the drawings]

1 shows an example of an embodiment of the present invention, wherein (a) is a front view, (b) is a left side view, and (c) is a right side view.

FIG. 2 is a cross-sectional view showing the same contact pin.

3A and 3B schematically show the above, wherein FIG. 3A is a front view, FIG. 3B is a rear view, and FIG. 3C is a plan view.

FIG. 4 is a schematic diagram showing a state where the coaxial cable is connected thereto.

FIG. 5 is a schematic diagram showing a use state of the above.

6A is a graph showing a result of impedance measurement using one example of the present invention, and FIG. 6B is a graph showing a result of impedance measurement using a conventional example.

FIG. 7 is a graph showing the attenuation characteristics of an example of the present invention.

FIG. 8 schematically shows an example of another embodiment of the present invention;
(A) is a front view, (b) is a rear view, and (c) is a plan view.

FIG. 9 schematically shows an example of another embodiment of the present invention;
(A) is a front view, (b) is a rear view, and (c) is a plan view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Signal conductor 2 Ground conductor 3 Printed wiring board 4 Circuit board 5 Circuit under test 6 Signal input pin 7 Ground circuit 8 Ground contact pin 9 Coaxial cable 10 Insulation layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kaneo Kagami 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Works, Ltd. BC01 BF05 BF08 CG08 DH06 FK05 HM05 HN01 HN09 KQ02 LR20

Claims (7)

[Claims] 1. A printed wiring board on which a signal conductor and a ground conductor are formed, a signal input pin electrically connected to the signal conductor and capable of contacting a circuit to be measured on the circuit board, and electrically connected to the ground conductor. A ground contact pin capable of contacting a ground circuit of a circuit board, and an impedance measuring probe electrically connected to an impedance measuring device by a coaxial cable, formed so as to match the impedance of the coaxial cable. A probe for measuring impedance, comprising: The signal input pin and the ground contact pin are formed by spring-type contact pins, and the signal is input when the signal input pin contacts the circuit to be measured on the circuit board and when the ground contact pin contacts the ground circuit on the circuit board. 2. The impedance measuring probe according to claim 1, wherein the contact pins are formed to extend and contract so that the tips of the input pins and the ground contact pins recede to the end surface of the printed wiring board. 3. The probe according to claim 1, wherein the printed wiring board is formed of any one of a microstrip structure, a strip structure, and a coplanar structure. 4. The printed wiring board is formed by using a material having a low dielectric constant and a low dielectric loss tangent.
The probe for measuring impedance according to any one of claims 1 to 3. 5. The printed wiring board according to claim 1, wherein the thickness of the insulating layer and the position of the ground contact pin are adjusted so as to match the impedance of the coaxial cable. The probe for measuring impedance described in 1. 6. The signal processing method according to claim 1, wherein the frequency characteristic of a signal passing therethrough by changing the resonance frequency by controlling the wiring length of the signal conductor is formed so as to be controllable. Probe for impedance measurement. 7. The impedance measuring probe according to claim 1, wherein the signal conductor, the ground conductor, the signal input pin, and the ground contact pin are plated with gold.