JP7230089B2 - Connection structure and connection method between coplanar line and connector, and sampling oscilloscope using the same - Google Patents

Description

The present invention relates to a connection structure and connection method between a coplanar line and a connector, and a sampling oscilloscope using the same.

A wideband sampling oscilloscope measures the waveform of a signal under measurement by sampling a plurality of times while shifting sampling points, and includes a sampler circuit for sampling the signal under measurement. The frequency response characteristics of the sampler circuit are required to be flat and favorable in a wide band from direct current to several tens of GHz (eg, 80 GHz). For this reason, when a sampler circuit is provided on a coplanar line substrate, for example, good transmission characteristics are required in a high frequency band of several tens of GHz (eg, 40 GHz) or more at the connection between the coplanar line substrate and the input/output connector. .

Not limited to sampler circuits, in general, at the connection between the coplanar line board and the coaxial input/output connector, the ground line is detoured with respect to the signal line connecting the coplanar line on the board and the central conductor line of the connector. This portion becomes inductive, and the higher the frequency, the worse the return loss (see, for example, Patent Document 1).

In Patent Document 1, a ground layer of the multilayer wiring board is exposed at a connecting portion between the multilayer wiring board and a small connector, and the exposed portion and the external conductor of the connector are electrically connected by soldering, silver paste, or the like. structure is described.

JP 2014-7390 A

However, in the connection structure described in Patent Document 1, a coplanar line board is housed in a metal case, a coaxial input/output connector is attached to the metal case, and the end face of the ground conductor on the board is attached with a conductive adhesive or a gold ribbon. Therefore, it cannot be used in a structure in which it is brought into contact with a metal case due to such reasons, and there is a problem that good transmission characteristics cannot be extended up to a high frequency band such as several tens of GHz.

FIG. 7 shows, as a conventional example, a connection structure in which a coplanar line substrate 1010 having a central conductor line 1013 and ground conductors 1014 on both sides thereof is accommodated in a metal case 1020, and a coaxial input/output connector 1030 is attached to the metal case 1020. It is a figure which shows. In the conventional example shown in FIG. 7, the ground path is detoured with respect to the signal path connecting the central conductor line 1013 of the substrate 1010 and the inner conductor 1031 of the connector 1030. This portion becomes inductive, and the higher the frequency, the higher the return loss. had a problem of exacerbation. Even if the end face of the ground conductor 1014 of the substrate 1010 in the longitudinal direction is brought into contact with the metal case 1020 by a conductive material such as a conductive adhesive or a gold ribbon, the configuration in which the ground path detours around the central signal path does not occur. However, the problem of deterioration of high-frequency transmission characteristics remains unchanged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and provides a connection structure and connection method excellent in high-frequency transmission characteristics at the connection between a coplanar line and a connector, and a sampling oscilloscope using the same. intended to

A connection structure between a coplanar line and a connector (hereinafter also simply referred to as a connection structure) of the present invention comprises a central conductor line (13) and the central conductor line (13) on one surface of a substrate (11) made of a plate-like dielectric material. a substrate (10) formed with a coplanar line (12) comprising a pair of ground conductors (14) spaced apart from the central conductor line on both sides of the central conductor line over the entire longitudinal direction ; a metal case (20) for housing the substrate; an internal conductor (31) electrically connected to the central conductor line of the coplanar line; a connector (30) having an electrically connected outer conductor (32) coaxially attached to the metal case, wherein the inner spacing between the ground conductors is the outer conductor of the connector; and the inner spacing between one ground conductor and the other ground conductor of the pair of ground conductors is equal to the width W of the center conductor line and the center conductor line and the one or the other ground It is equal to the sum of 2G obtained by doubling the distance G between the conductor and satisfies the relationship W+2G=φ, and the end of the ground conductor in the direction along the center conductor line of the coplanar line and the connector An end of the outer conductor is electrically connected .

As described above, in the connection structure of the present invention, since the inner spacing between the ground conductors is equal to the inner diameter of the outer conductor of the connector, the ground path is detoured with respect to the signal path connecting the central conductor of the substrate and the inner conductor of the connector. It is configured to be connected in the shortest possible time. With this configuration, there is no point of impedance discontinuity at the joint between the coplanar line and the connector, and return loss in a high frequency band is also suppressed, making it possible to obtain excellent high frequency transmission characteristics.

In the structure for connecting a coplanar line and a connector according to the present invention, the metal case may include a holding portion (24) for holding the board while floating from the bottom of the metal case inside the metal case. .

With this configuration, in the connection structure of the present invention, since the coplanar line is arranged at a certain distance from the bottom surface of the metal case, the presence of the metal bottom surface does not affect the electric field distribution of the coplanar line, and high frequency transmission is possible. It can function effectively as a coplanar line as intended even in the band.

In the structure for connecting a coplanar line and a connector of the present invention, the end of the ground conductor in the direction in which the coplanar line extends and the end of the outer conductor of the connector are connected via a conductive material (40). An electrically connected configuration may also be used.

With this configuration, in the connection structure of the present invention, the longitudinal ends of the ground conductors of the substrate and the ends of the outer conductors of the connector are electrically connected reliably, so the central conductor of the substrate and the inner conductor of the connector are electrically connected. The ground path does not take a detour to the signal path that connects the With this configuration, the return loss in the high frequency band is also suppressed, and excellent high frequency transmission characteristics can be obtained.

A sampling oscilloscope of the present invention is a sampling oscilloscope comprising a sampler circuit for sampling a signal under measurement, wherein the coplanar line formed on the substrate and the connector attached to the metal case are described in any one of the above. and a bare chip flip-chip mounted on the substrate, wherein the sampler circuit is formed on the bare chip.

With this configuration, the sampling oscilloscope of the present invention has a bare chip flip-chip mounted on a board having a connection structure that can obtain excellent high-frequency transmission characteristics at the connection between the coplanar line and the connector, and the sampler circuit is formed on the bare chip. Therefore, a sampling oscilloscope that has good frequency response characteristics in a wide band from DC to several tens of GHz without deteriorating the high frequency response characteristics of the sampler circuit due to the deterioration of the high frequency transmission characteristics at the connection part. realizable.

In the method of connecting a coplanar line and a connector according to the present invention, a central conductor line (13) is formed on one surface of a substrate (11) made of a plate-shaped dielectric material, and the central conductor line (13) is provided along the entire longitudinal direction of the central conductor line. A substrate (10) is provided with a coplanar line (12) formed with ground conductors (14, 14) spaced apart from the center conductor line on both sides of the center conductor line, and the substrate is placed in a metal case (20 ) and coaxially having an inner conductor (31) and an outer conductor (32) surrounding the inner conductor via an insulating material, is attached to the metal case, and the inner conductor of the connector is electrically connecting to the center conductor line of the coplanar line and electrically connecting the outer conductor to the ground conductor, wherein the inner spacing between the ground conductors is the inner diameter φ of the outer conductor of the connector; and the inner spacing between one ground conductor and the other ground conductor of the pair of ground conductors is equal to the width W of the central conductor line and the width W of the central conductor line and the one or the other ground conductor It is equal to the sum of 2G obtained by doubling the distance G and satisfies the relationship W+2G=φ, and the end portion of the ground conductor in the direction along the center conductor line of the coplanar line and the outer conductor of the connector are electrically connected to each other .

As described above, in the connecting method of the present invention, in the step of attaching the connector to the metal case, since the inner spacing between the ground conductors of the substrate is equal to the inner diameter of the outer conductor of the coaxial connector, the center conductor of the substrate and the connector are separated from each other. The configuration is such that the ground path is connected to the signal path that connects the internal conductors of the internal conductors at the shortest possible distance without detouring. With this configuration, there is no point of impedance discontinuity at the connecting portion between the coplanar line and the connector, and return loss in a high frequency band is suppressed, making it possible to obtain excellent high frequency transmission characteristics.

According to the present invention, it is possible to provide a connection structure, a connection method, and a sampling oscilloscope using the same, which are excellent in high-frequency transmission characteristics at a connection portion between a coplanar line and a connector.

1(a) is a plan view of a substrate on which a coplanar line is formed according to an embodiment of the present invention, and FIG. 1(b) is a cross-sectional view taken along line AA of FIG. 2 is a cross-sectional view showing a state in which the substrate of FIG. 1 is housed in a metal case; FIG. FIG. 3 is a cross-sectional view taken along the line BB of FIG. 2; 4 is a flow chart of a method for connecting a coplanar line and a connector according to one embodiment of the present invention; 1 is a diagram showing a schematic configuration of a sampling oscilloscope according to one embodiment of the present invention; FIG. FIG. 3 is a cross-sectional view showing a bare chip flip-chip mounted on a substrate of a connection structure according to an embodiment of the present invention; 1 is a diagram showing a schematic configuration of a conventional connection structure between a coplanar line and a connector; FIG.

A connection structure 1 between a coplanar line 12 and a coaxial connector 30 according to an embodiment of the present invention will be described with reference to the drawings.

(substrate)
FIG. 1(a) is a plan view of a substrate 10 on which a coplanar line 12 is formed in the connection structure 1 according to the present embodiment, and FIG. 1(b) is a cross-sectional view taken along the line AA in FIG. 1(a). be. As shown in FIG. 1, the substrate 10 includes a plate-shaped dielectric substrate 11 and a coplanar line 12 formed on one surface 11 a of the substrate 11 . The coplanar line 12 is composed of a central conductor line 13 and a pair of ground conductors 14,14. The central conductor line 13 is a conductor pattern with a width W extending in the X-axis direction (longitudinal direction). It is formed with G. The substrate 10 may have various high-frequency circuits formed on the surface 11a of the base material 11 in addition to the coplanar line 12, or may have a semiconductor IC such as a bare chip mounted thereon.

The impedance of the coplanar line 12 is mainly determined by the width W of the central conductor line 13, the gap width G between the central conductor line 13 and the ground conductors 14 on both sides, the thickness t of the substrate 11, and the dielectric constant ε of the substrate 11. determined. By appropriately setting these parameters (that is, W, G, t, and ε), the impedance of the coplanar line 12 can be set to be the same as the impedance of the connector 30, eg, 50Ω.

In this embodiment, no conductor pattern is formed on the back surface 11b of the substrate 10, but a so-called grounded coplanar line may be employed in which a ground conductor layer is also formed on the back surface 11b. In this case, the ground conductor 14 on the front surface 11a of the substrate 10 and the ground conductor layer on the back surface 11b are electrically connected through a plurality of via holes.

(metal case)
FIG. 2 is a cross-sectional view showing a state in which the substrate 10 is accommodated in the metal case 20. As shown in FIG. As shown in FIG. 2 , the metal case 20 includes a metal case body 21 having a hollow portion and a metal lid 22 that covers the opening of the case body 21 . Since the substrate 10 is accommodated in the metal case 20, it is resistant to noise from the outside and does not emit unnecessary noise to the outside. Further, the metal case 20 has a holding portion 24 that holds the substrate 10 floating from the bottom of the metal case 20 inside the metal case 20 . Specifically, a stepped portion or a convex portion serving as the holding portion 24 is formed at an intermediate height between the heights of the case body 21 on the opposing inner walls of the case body 21 . The substrate 10 is placed and held on a stepped portion as a holding portion 24 formed on the opposing inner walls of the case body 21 .

With this configuration, the coplanar line 12 is arranged at a certain distance from the metal bottom surface of the metal case 20, so that the presence of the metal bottom surface does not affect the electric field distribution of the coplanar line even in a high frequency band. It can effectively function as a coplanar line as intended. When a grounded coplanar line is used as the coplanar line 12, the substrate 10 may be arranged on the bottom surface of the metal case 20 or near it.

The outer shape of the metal case 20 is a rectangular parallelepiped shape, but is not limited to this, and any shape may be adopted as long as the board 10 can be accommodated and the connector 30 can be attached. Also, the metal case 20 has a structure that can be divided into two parts, but is not limited to this, and may have a structure that can be divided into three or more parts. For example, the bottom plate may be detachable.

(connector)
The connector 30 includes an inner conductor 31 electrically connected to the center conductor line 13 of the coplanar line 12 and an outer conductor 31 surrounding the inner conductor 31 via an insulating bead 33 and electrically connected to the ground conductor 14 . It is a connector of a coaxial structure having a conductor 32 on the same axis. The connector 30 is screwed into the hole 23 of the metal case 20 with or without airtightness. A coaxial cable can be connected to the side of the connector 30 opposite to the side connected to the coplanar line 12 .

The impedance of the coaxial connector 30 is determined by the outer diameter D of the inner conductor 31, the inner diameter φ of the outer conductor 32, and the dielectric constant ε of the insulating bead 33 provided between the inner conductor 31 and the outer conductor 32. FIG. Therefore, by appropriately setting these parameters D, φ, and ε, the impedance of the connector 30 can be set to the same impedance as the coplanar line 12, eg, 50Ω.

Depending on the frequency band to be handled, the connector 30 is, for example, a so-called "1.85 mm connector" in which the inner diameter of the outer conductor 32 is 1.85 mm, or a so-called "1.0 mm connector" in which the inner diameter of the outer conductor 32 is 1.0 mm. ' may be

As shown in FIG. 3 , the inner spacing (also called gap width) between the ground conductors 14 , 14 is equal to the inner diameter φ of the outer conductor 32 of the connector 30 . The inner spacing between one ground conductor 14 and the other ground conductor 14 is the sum of the width W of the central conductor line 13 and 2G obtained by doubling the spacing G between the central conductor line 13 and the ground conductor 14 . That is, it satisfies W+2G=φ. Since the inner space between the ground conductors 14, 14 is equal to the inner diameter φ of the outer conductor 32 of the connector 30, the ground path detours from the signal path connecting the central conductor line 13 of the substrate 10 and the inner conductor 31 of the connector 30. It is configured to be connected in the shortest possible time. With this configuration, there is no point of impedance discontinuity at the connection between the coplanar line 12 and the connector 30 having the coaxial structure, and return loss in the high frequency band is also suppressed, making it possible to obtain excellent high frequency transmission characteristics.

The end of the ground conductor 14 in the direction along the central conductor line 13 of the coplanar line 12 (also referred to as the longitudinal direction) and the end of the outer conductor 32 of the connector 30 are preferably bonded with a conductive adhesive, a gold ribbon, or the like. They are connected via a conductive material 40 .

As a result, the longitudinal ends of the ground conductors 14 of the board 10 and the ends of the outer conductors 32 of the connector 30 are electrically connected with certainty. 31, the ground path does not take a detour and is more reliably connected to the signal path at the shortest distance. With this configuration, the return loss in the high frequency band is also suppressed, and excellent high frequency transmission characteristics can be obtained.

Although two connectors 30 are attached to the metal case 20 in FIG. 3, the number is not limited to two, and one or more than three connectors 30 may be attached.

(Method of connecting coplanar line and connector)
Next, a method of connecting the coplanar line 12 and the connector 30 according to this embodiment will be described.

FIG. 4 is a flow chart showing an outline of a method of connecting the coplanar line 12 and the connector 30. As shown in FIG. As shown in FIG. 4, the width W of the central conductor line 13 of the coplanar line 12 and the gap width G between each of the ground conductors 14 on both sides and the central conductor line 13 correspond to the inner diameter of the outer conductor 32 of the connector 30. A substrate 10 of a coplanar line 12 that satisfies the relationship φ and φ=W+2G is prepared (step S1).

Next, the substrate 10 of the coplanar line 12 is arranged on the step portion provided as the holding portion 24 inside the metal case 20 (step S2). The substrate 10 is held floating from the bottom surface of the metal case 20 .

Next, the coaxial connector 30 is attached by, for example, screwing into the hole 23 formed in the wall of the metal case 20 (step S3).

Next, the central conductor line 13 of the coplanar line 12 and the inner conductor 31 of the connector 30 are connected by soldering or the like (step S4).

Next, if there is a gap between the longitudinal end of the ground conductor 14 of the substrate 10 and the end of the outer conductor 32 of the connector 30, the gap is filled with a conductive material 40 such as a conductive adhesive or a gold ribbon. to ensure electrical connection between them (step S5). Even if there is no gap, a conductive material such as a conductive adhesive or a gold ribbon is applied to the contact portion between the longitudinal end of the ground conductor 14 and the end of the outer conductor 32 of the connector 30 to Electrical connections may be reinforced.

Finally, the lid 22 of the metal case 20 is closed (step S6). As described above, the connection structure between the coplanar line 12 and the coaxial connector 30, in which the board 10 is accommodated in the metal case 20, is completed.

(sampling oscilloscope)
Next, the sampling oscilloscope 100 will be explained.

The sampling oscilloscope 100 has wideband and low-noise characteristics, and displays waveforms of signals under test transmitted from a device under test (DUT) 200 . As shown in FIG. 5, the sampling oscilloscope 100 includes a trigger generation section 110, a sampler circuit 120, an A/D conversion section 130, a display section 140, and a control section 150.

The trigger generating section 110 generates a sampler drive pulse (strobe signal) for driving the sampler circuit 120 . The trigger generator 110 uses, for example, a step recovery diode or a transistor circuit that operates at high speed, and generates a high-speed pulse strobe signal.

The sampler circuit 120 includes, for example, a diode, and samples an externally input signal under measurement using a strobe signal generated at several hundred kHz to several tens of MHz by the trigger generator 110 as sampling timing. Equivalent time sampling such as random sampling or sequential sampling is adopted for sampling.

The A/D converter 130 converts analog output data sampled by the sampler circuit 120 into digital data.

The display unit 140 is configured by, for example, a liquid crystal display, and displays the waveform of the signal under measurement, statistically processed measurement results, and the like under the control of the control unit 150 .

The control unit 150 controls the trigger generation unit 110, the sampler circuit 120, the A/D conversion unit 130, and the display unit 140 in order to observe a waveform that repeats at a high frequency.

In the sampling oscilloscope 100 of this embodiment, the connection structure 1 between the substrate 10 of the coplanar line 12 housed in the metal case 20 and the coaxial connector 30 is used, and as shown in FIG. Flip chip mounted. In flip chip mounting, the bare chip 160 is pressed against the substrate 10, and the bumps 162 provided on the electrode pads 161 on the bare chip 160 side are joined to the electrode pads 171 on the substrate 10 side. A sampler circuit 120 is formed on this bare chip 160 .

With this configuration, in the sampling oscilloscope 100 of the present embodiment, the bare chip 160 is flip-chip mounted on the substrate 10 of the connection structure 1 that can obtain excellent high-frequency transmission characteristics at the connection between the coplanar line 12 and the connector 30. Since the sampler circuit 120 is formed on the bare chip 160, the high-frequency response characteristics of the sampler circuit 120 are not deteriorated due to the deterioration of the high-frequency transmission characteristics at the connection portion, and the wideband from direct current to several tens of GHz is possible. A sampling oscilloscope with good frequency response characteristics can be realized.

(action/effect)
As described above, in the connection structure 1 according to the present embodiment, the inner spacing (W+2G) between the ground conductors 14, 14 is equal to the inner diameter φ of the outer conductor 32 of the connector 30. The configuration is such that the ground path is connected to the signal path connecting the internal conductors 31 of the connector 30 in the shortest possible manner without detouring. With this configuration, there is no point of impedance discontinuity at the connection between the coplanar line 12 and the connector 30, and return loss in the high frequency band is also suppressed, making it possible to obtain excellent high frequency transmission characteristics.

Further, when the connection structure 1 according to the present embodiment is used in the sampler circuit 120 of the sampling oscilloscope 100, it is possible to suppress the deterioration of the high-frequency transmission characteristics at the connection portion between the coplanar line 12 and the connector 30, thereby improving the frequency response characteristics in a wide band. It can contribute to the realization of a good wideband sampling oscilloscope.

INDUSTRIAL APPLICABILITY As described above, the present invention has an effect that high-frequency transmission characteristics are excellent at the connection portion between the coplanar line and the connector, and provides a connection structure and connection method between the coplanar line and the connector, and sampling using the same. Useful throughout the oscilloscope.

Reference Signs List 1 Connection structure 10 Board 11 Base material 11a Front surface 11b Back surface 12 Coplanar line 13 Central conductor line 14 Ground conductor 20 Metal case 21 Case main body 22 Lid 23 Hole 24 Holding part 30 Connector 31 Internal conductor 32 External conductor 33 Bead (insulating material)
40 conductive material 100 sampling oscilloscope 110 trigger generation unit 120 sampler circuit 130 A/D conversion unit 140 display unit 150 control unit 160 bare chip 161, 171 electrode pad 162 bump 200 DUT

Claims (2)

A sampling oscilloscope comprising a sampler circuit for sampling a signal under measurement,
A central conductor line (13) is provided on one surface of a substrate (11) made of a plate-shaped dielectric material, and a central conductor line (13) is provided on both sides of the central conductor line over the entire longitudinal direction of the central conductor line with a space from the central conductor line. A substrate (10) on which a coplanar line (12) consisting of a pair of arranged ground conductors (14) is formed;
a metal case (20) containing the substrate;
an inner conductor (31) electrically connected to the central conductor line of the coplanar line; and an outer conductor (32) surrounding the inner conductor via an insulating material and electrically connected to the ground conductor. coaxially, and a connector (30) attached to the metal case, a connection structure between the coplanar line formed on the substrate and the connector attached to the metal case, wherein ,
the inner spacing between the ground conductors is equal to the inner diameter φ of the outer conductor of the connector;
The inner spacing between one ground conductor and the other ground conductor of the pair of ground conductors is twice the width W of the central conductor line and the spacing G between the central conductor line and the one or the other ground conductor. is equal to the sum of 2G obtained by
the connection structure in which an end of the ground conductor in the direction along the central conductor line of the coplanar line and a planar end of the outer conductor of the connector are electrically connected;
a bare chip that is flip-chip mounted on the substrate so that bumps provided on electrode pads on the bare chip side are bonded to electrode pads on the substrate side;
with
The sampler circuit is formed on the bare chip,
The sampling oscilloscope, wherein the metal case includes holding portions (24) formed on opposing inner walls of the metal case that hold the substrate floating from the bottom of the metal case inside the metal case. An end of the ground conductor in the direction along the center conductor line of the coplanar line and an end of the outer conductor of the connector are electrically connected via a conductive material (40). Item 1. The sampling oscilloscope according to item 1.

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