JPH0560789A - Coaxial probe - Google Patents

Abstract

PURPOSE:To make it possible to perform highly accurate measurement in a broad range by expanding applicability for bodies under tests with respect to the constitution of a coaxial cable. CONSTITUTION:A connecting pin 5 is connected to an inner conductor 16 of a coaxial cable 2 and brought into contact with the first signal terminal of a body under test. The connecting pin 5 is made to protrude to the outside. A connecting plate 19 is connected to an outer conductor 17 of the coaxial cable 2 and brought into contact with the grounding terminal or the second signal terminal of the body under test. The connecting plate 19 is made to extend to the outside of the connecting pin 5. This probe is constituted in this way. The connecting plate 19 is formed in a disk shape, which is coaxial with the connecting pin 5. The connecting plate 19 is slid in the longitudinal direction of the connecting pin 5, and the surface of the plate 19 is in contact with the grounding terminal or the second signal terminal. A rubber-state buffer material for backing up the contact is provided at the rear surface of the connecting plate 19 in this constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial probe which is brought into contact with a device under test when measuring the transmission characteristics of a transmission path and the characteristics of electronic circuit components.

[0002]

2. Description of the Related Art FIG. 8 (a) is an external view showing a conventional coaxial probe, in which a signal probe 3 is connected to the other end of a coaxial cable 2 in which a coaxial connector 1 is connected to one end, and a terminal 7 is used. The ground probe 4 is connected to the signal probe 3.

A connecting pin 5 for connecting to the inner conductor of the coaxial cable 2 projects at the tip of the signal probe 3 and an outer cylindrical portion 6 of the signal probe 3 for connecting to the outer conductor of the coaxial cable 2.
To the connection pin 8 of the earth probe 4 via the terminal 7. The connection pins 5 and 8 are slidable in the length direction of the probe 3 or 4.

Reference numeral 9 denotes a handle portion of the signal probe 3, 10 denotes a handle portion of the earth probe 4, and the signal probe 3 and the earth probe 4 hold those handle portions 9 or 10 in their hands.
It comes into contact with the connection partner terminal of the DUT.

FIG. 8B is an external view showing a conventional coaxial probe. The coaxial probe 11 is connected to the other end of the coaxial cable 2 having the coaxial connector 1 connected to one end. The connection pin 5 connected to the inner conductor of the coaxial cable 2 and the ground connection pin 12 connected to the outer conductor of the coaxial cable 2 are slidable in the length direction of the coaxial probe 11.

In order to secure contact with the ground terminal of the device under test, a part of the tip of the connecting pin 12 is provided with sawtooth-shaped irregularities (jagged). Hold it in your hand and make contact with the mating terminal of the DUT.

[0007]

In the conventional probe separated into the signal probe 3 and the earth probe 4, the contact between the connection pins 5 and 8 is independent of the distance between the signal terminal of the DUT and the earth terminal. It will be possible. However, both hands are required for the manual operation, and since the grounding connection pin 8 is connected to the outer conductor of the coaxial cable 2 through the terminal 7, the impedance becomes unbalanced and precision measurement cannot be performed. there were.

On the other hand, the coaxial probe 11 can be operated by one hand to connect the contact pins 5 and 12 to the signal terminal and the ground terminal of the device under test, and the balanced impedance will be secured. Since the distance between the signal terminal and the ground terminal must be constant, and it is dedicated for the DUTs having different distances, there is a problem in that a plurality of them must be prepared.

[0009]

FIG. 1 is a basic configuration diagram of the present invention, in which an inner conductor 16 and an outer conductor 17 are coaxially connected to one end of an coaxial cable 2 through an insulator (dielectric body) 15. The coaxial probe 21 includes a connection pin 5 that contacts the signal terminal (first terminal) of the DUT, and a connection plate that contacts the ground terminal or another signal terminal (second terminal) of the DUT. Has 19.

The connection pin 5 is an inner conductor of the coaxial cable 2.
Connect to 16. The connection plate 19 connects to the outer conductor 17 of the coaxial cable 2 and extends outside at least one of the connection pins 5.

[0011]

In general, a coaxial line is formed by connecting parallel plane conductors 21 and 22 in an annular shape as shown in FIG. 2 (a), and as shown in FIG. 2 (b), a cylindrical inner conductor 16 and outer conductor 17 It is thought that they are coaxially opposed to each other. Therefore, if the orthogonal X, Y, and Z axes are selected as shown in FIG. 2, the plane wave transmitted between the conductors 21 and 22 in the Z axis direction (the length direction of the inner conductor 16 and the outer conductor 17) is Where the electric field in the direction is Ey, the magnetic field in the Z-axis direction is Hz, the permittivity between conductors (insulators) is ε, and the permeability between conductors (insulators) is μ, Ey = E ₀ · exp [jwt− γZ] −Hz = H ₀ · exp [jwt−γZ] E ₀ / H ₀ = (μ / ε) ^1/2 , γ = jw (εμ) ^1/2

From this, the standing wave (transmitted wave) electric fields Er and Eθ satisfying the Maxwell equation and the boundary condition of the conductor surface.
Is a ^{Er = (μ / ε) 1/2} · H 0 / r · exp [jwt-γZ] Eθ = H 0 / r · exp [jwt-γZ].

Therefore, from FIG. 2B, the potential difference V between the conductors is
Is V = ∫Er dr = (μ / ε) ^1/2 · H ₀ · log (D / d) · exp [jwt-γZ] (However, the integral is from d / 2 to D / 2) The total current I flowing through the conductor 16 is I = 2πrH ₀ = 2πrH ₀ · exp [jwt-γZ], where d is the diameter of the inner conductor 16 and D is the inner diameter of the outer conductor 17.

As a result, the characteristic impedance Z ₀ of the coaxial line is Z ₀ = V / I = (1 / 2π)  (μ / ε) ¹ / 2log (D / d) = 60 (μ _s / ε _s ) ^1/2 · log (D / d).

On the basis of the above principle, the impedance of the coaxial line is determined by the dielectric constant of the insulator between the inner conductor 16 and the outer conductor 17 and the distance from the inner conductor 16 to the outer conductor 17. Therefore, if the coaxial state is not broken, the impedance becomes balanced, and the flat connecting plate 19 extending outward is connected to the outer conductor 17.
Even if it is provided, the portion satisfies the above-mentioned principle, so that the balanced impedance is maintained.

The coaxial probe 21 of the present invention is basically configured as shown in FIG. 1 and includes a connecting pin for connecting the inner conductor of the coaxial cable to the conductor and the plate for grounding the ground, and has a balanced impedance. It is possible to operate with one hand by ensuring that the distance between the signal terminal and the ground terminal (other signal terminal) is different for the DUT.

[0017]

FIG. 3 is a side view (a) and a front view (b) of a coaxial probe according to a first embodiment of the present invention, and FIG. 4 is a side view (a) of a coaxial probe according to a second embodiment of the present invention. ) And an explanatory view (B) in which it is brought into contact with the device under test, and FIG. 5 is a side view (A) in which a part of the coaxial probe according to the third embodiment of the present invention is cut away and (A) its arrow view. And perspective view of the earth plate (C), Fig. 6
FIG. 6 is a side view of a coaxial probe according to a fourth embodiment of the present invention.
FIG. 7B is a side view of the coaxial probe according to the fifth embodiment of the present invention.

In FIG. 3, the coaxial probe 25 to which the coaxial cable 2 is connected has a structure in which a disk-shaped ground plate (connection plate) 26 is provided at the tip of the grounding connection terminal 12 of the conventional coaxial probe 11. A connecting pin 5 protruding from the right end and contacting the signal terminal (first signal terminal) of the device under test;
The ground plate 26 that contacts the ground terminal of the DUT or another signal terminal (second signal terminal) can slide in the length direction of the coaxial probe 25, like the conventional connection pin 5 and the connection terminal 12. Is.

The coaxial probe 25 is operated by fixing the handle portion 9 to an appropriate holder or holding it in the hand and operating it.
Is brought into contact with a predetermined signal terminal of the device under test, and the earth plate 26 is brought into contact with the earth terminal of the device under test or another signal terminal.

As shown in FIG. 4, in the coaxial probe 30 to which the coaxial cable 2 is connected, 31 is a handle portion extending upward and bent at an appropriate angle, 32 is a main body portion, and 33 is a buffer plate made of rubber or the like. , 34 are backup members that are joined to the main body 32 and back up the earth plate 26 via the buffer plate 33, and the connecting pin 5 projects from the center of the disk-shaped earth plate 26 connected to the outer conductor of the coaxial cable 2. To do.

The connecting pin 5 and the earth plate 26 are the main body
It is slidable in the length direction of 32, and while holding the grip portion 31 in the hand, the connecting pin 5 is brought into contact with the signal terminal 36 of the DUT 35 and the earth plate 26 is held as shown in FIG. 4B. Contact the ground terminal 37 of the DUT 35. At this time, the cushioning material 33 made of rubber, for example, connects the earth plate 26 to the earth terminal.
Press toward 37. As a result, the ground plate 26 corresponds to the unevenness of the ground terminal 37 and comes into uniform contact with the ground terminal 37.

5, in the coaxial probe 40 to which the coaxial cable 2 is connected, the connection pin 5 connected to the inner conductor of the coaxial cable 2 projects from the lower end of the main body 41. The connection pin 5 is slidable in the longitudinal direction of the main body 41 as in the conventional case, and the grip 42 is fixed to the middle of the main body 41.

The buffer plate 43 is adhered to the upper surface of the ground plate 44 and is used to back up the ground plate 44.
A plurality of coil springs 46 are inserted between the backup member 45 adhered to the upper surface of the and the grip portion 42, and the pair of pins 47 planted in the backup member 45 suspended by the coil springs 46 are grips. It is slidably fitted in a through hole provided in the portion 42.

The earth plate 44, which is connected to the outer conductor of the coaxial cable 2 and is slidable in the longitudinal direction of the main body 41 in the same manner as the conventional earth connecting terminal 12, has two directions toward the outside of the connecting pin 5. Is a rectangular shape that extends to the base plate, and the buffer plate 43 and the backup member 45 are also square shapes adapted to the ground plate 44, and the coaxial probe 40 is brought into contact with the DUT by holding the grip portion 42.

In FIG. 6, the coaxial probe 50 to which the coaxial cable 2 is connected is configured to be mounted on an automatic inspecting machine of the DUT, and the holder 51 to which the middle portion of the probe main body 41 is fixed is L-shaped. Is. The buffer plate 43 is adhered to the upper surface of the earth plate 44, and the backup member 45 adhered to the upper surface of the buffer plate 43 for backing up the earth plate 44.
And a plurality of coil springs 46 are inserted between the handle portion 42 and the handle portion 42,
The pair of pins 47 planted in the backup member 45 suspended by the coil spring 46 is slidably fitted in the through hole provided in the horizontal piece of the holder 51 having the hole 52 for mounting in the vertical piece. To meet.

The connecting pin 5 connected to the inner conductor of the coaxial cable 2 and the earth plate 44 connected to the outer conductor of the coaxial cable 2 are slidable in the length direction of the probe main body 41, and are connected to the backup member 45. A plurality of coil springs 46 are inserted between the holder 51 and the backup member.
The pair of pins 47 planted in the 45 are slidably fitted into the through holes provided in the holder 51.

In the coaxial probe 50, the holder 51 is moved up and down to connect the connecting pin 5 and the earth plate.
44 contacts a predetermined portion of the DUT. FIG. 7 shows a structure of a coaxial probe 55 that simultaneously measures at a plurality of locations (seven locations in the figure), and is a holder which is mounted on an appropriate component and moves up and down.
Attach multiple probe body parts 41 (seven in the figure) to 56,
The coaxial cable 2 is connected to each probe body 41.

A connecting pin 5 for connecting to the inner conductor of the coaxial cable 2 projects from each probe body 41, and a common ground plate 57 for a plurality of probe bodies 41 connects to the outer conductor of each coaxial cable 2. A pair of pins 47 are planted in the backup member 59 that backs up the ground plate 57 via a buffer plate 58 having the same shape as the ground plate 57, and the pair of pins 47 are provided in the holder 56. It fits into the through hole and can slide up and down.
Between 56 and backup member 59, backup member
A plurality of coil springs 46 for hanging 59 are inserted.

[0029]

The coaxial probe of the present invention configured as described above can be commonly used for DUTs having different distances between the signal terminal and the ground terminal without damaging the balanced impedance. It has a wide range of applications from manual measurement of level to automatic measurement system, and it is possible to measure resistance, capacitance, inductance, and impedance with high precision, which is an excellent application.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a diagram for explaining a characteristic impedance of a coaxial cable.

FIG. 3 is an explanatory diagram of a coaxial probe according to a first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a coaxial probe according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a coaxial probe according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a coaxial probe according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a coaxial probe according to a fifth embodiment of the present invention.

FIG. 8 is an external view of a conventional coaxial probe.

[Explanation of symbols]

 2 is a coaxial cable 5 is a contact pin that contacts the first signal terminal 16 is an inner conductor of the coaxial cable 17 is an outer conductor of the coaxial cable 19,26,44,57 is a connection plate (earth plate) 21,25,30, 40 and 50 are coaxial probes 33, 43 and 58 are rubber-like cushioning materials 36 are first signal terminals 37 are ground terminals (or second signal terminals)

Claims (3)

[Claims] 1. A connecting pin (5), which is connected to the inner conductor of the coaxial cable (2) and is in contact with the first signal terminal (36) of the device under test, projects and is connected to the outer conductor of the coaxial cable (2). A coaxial probe characterized in that a connection plate (19) contacting the ground terminal (37) or the second signal terminal of the device under test extends outside the connection pin (5). 2. The connection plate (19) is the connection pin.
The coaxial probe according to claim 1, wherein the coaxial probe has a disk shape coaxial with (5). 3. The contact pin is backed up on the back surface of the connection plate (19) whose surface slides in the length direction of the connection pin (5) and contacts the ground terminal (37) or the second signal terminal. The coaxial probe according to claim 1, further comprising a rubber-like cushioning material (33, 43, 58) which is provided.