JPH10145114A - Penetration-type line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the impedance non-matching part of an overall circuit and to provide the transmission line of wide band width by providing a ground conductor along the peripheral surface of a via hole, through which a central conductor passes and operating it as a distribution constant circuit element. SOLUTION: In a coaxial connector 10, the central conductor 12 is arranged at shaft center of a cylindrical external shell 11 and an insulating body 13 having a prescribed dielectric constant is inserted with the external shell 11. The central conductor 12 of the coaxial connector 10 passes through the via hole 35, formed on a shielding base 20 and the printed board 30. The conductor is electrically connected to the via hole 35 by solder 36, and it is derived to the surface of the printed board 30. A cylindrical ground conductor 39 is provided along the peripheral face of the via hole 35. Thus, specified impedance is regulated by the diameter D of the via hole 35, an interval (g) between the via hole and the ground conductor 39, the diameter (d) of a ground conductor 39 and the ratio relative permittivity of the insulating board 32. The part of the via hole 35 operates as the distribution constant circuit element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedthrough line formed on a printed circuit board on which a circuit for handling a high-frequency signal is mounted.

[0002]

2. Description of the Related Art In a circuit for handling a high-frequency signal, a signal transmission line uses a transmission line with uniform impedance matching.
Generally, a microstrip line or a coaxial transmission line is used. FIG. 5 shows a structure of a circuit in which a coaxial line and a microstrip line are combined. In the figure, 10 is a coaxial connector, 20 is a shield case, and 30 is a printed circuit board. In the coaxial connector 10, a cylindrical outer shell 11 functions as an outer conductor, and a center conductor 12
Are arranged, and an insulator 13 having a predetermined dielectric constant is interposed between the center conductor 12 and the outer shell 11 so that the impedance between the outer shell 11 and the center conductor 12 is maintained at a predetermined value, for example, 50Ω. .

[0003] The center conductor 12 of the coaxial connector 10 is led out to the front surface of the printed circuit board 30 through a hole formed in the shield case 20 and the printed circuit board 30. The microstrip line 31 is formed on the front surface of the printed circuit board 30. The microstrip line 31 is, for example, an earth conductor 33 formed on the surface opposite to the insulating plate 32 or an earth conductor 3 formed surrounding the microstrip line 31.
4 and the dielectric constant of the insulating plate 32 to match a predetermined impedance.

[0004] The center conductor 12 of the coaxial connector 10 penetrates a via hole (through hole) 35 formed in an insulating plate 32 constituting the printed circuit board 30, and is electrically and mechanically connected to the via hole 35 by solder 36 to form a microstrip. It is electrically connected to line 31. FIGS. 6 and 7 show that microstrip lines 31A and 31B whose impedance is matched are formed on both sides of printed circuit board 30, and these microstrip lines 31A and 31B are electrically connected to each other by through holes 37 formed in insulating plate 32. It shows the state where it was done.

[0005]

According to the structure shown in FIG. 5, the center conductor 12 of the coaxial connector 10 is maintained in the impedance-matched state up to the portion facing the shield case 20, but the insulating plate 32 In the portion penetrating through, ie, the portion penetrating the via hole 35, the conductor functions as an inductance component, and the impedance is in a mismatched state. Due to the presence of the impedance mismatched portion, reflection occurs at the impedance mismatched portion, which causes a transmission loss, and has a disadvantage that transmission of a frequency that can be transmitted, particularly a high frequency signal, is restricted.

[0006] In the case shown in FIGS.
There is a disadvantage that the impedance becomes mismatched at the portion 7 and the transmittable frequency is limited as in the case of FIG. For this reason, for example, the method shown in FIG. 8 may be adopted. In the example of FIG. 8, the center conductor 12 of the coaxial connector 10 is electrically connected to the microstrip line 31 formed on the front surface of the printed circuit board 30, and the conductor is extended from the connection point. A capacitance is formed, and an inductance component generated in a portion penetrating the insulating plate 32 is canceled by the capacitance. Generally, the portion of the capacitance formed by the conductor 38 is called a matching circuit. In this matching circuit, the inductance value of the center conductor 12 also changes according to the value of the thickness t of the insulating plate 32. Therefore, the area of the conductor 38 must be determined according to the thickness t of the insulating plate 32. .

FIG. 9 shows the structure of FIG. 5 and FIGS.
The return loss characteristics in the case of the structure of FIG. The return loss characteristic means that the larger the numerical value in the vertical axis direction, the smaller the reflection. Generally, to transmit a signal with high quality, the return loss is required to be 20 dB or more. Therefore, the return loss characteristic shown in FIG.
The transmission frequency is up to about GHz, and a signal having a frequency higher than the transmission frequency suffers an obstacle such as waveform distortion.

FIG. 10 shows a return loss characteristic in the case of FIG. 8 to which a matching circuit is added. In this case, 20 dB
The following can be guaranteed at most about 2.5 GHz. As described above, conventionally, the frequency that can be transmitted has a limit value of about 3 GHz, and the transmission band is insufficient for handling signals higher than that. SUMMARY OF THE INVENTION It is an object of the present invention to provide a structure of a penetration type line in which impedance mismatch does not occur even in a portion penetrating through an insulating plate, and therefore a broadband transmission characteristic can be obtained.

[0009]

According to the present invention, a ground conductor is disposed in parallel with a signal conductor penetrating the insulating plate, and the signal conductor penetrating the insulating plate is operated as a distributed constant circuit element by the ground conductor. It is to let. That is, an operation equivalent to that of the microstrip line is performed.

Therefore, according to the present invention, the impedance of the portion of the signal conductor penetrating the insulating plate can be matched, and the advantage is obtained that the transmission band of the entire device can be expanded.

[0011]

FIG. 1 shows an embodiment of the present invention. This embodiment shows a case where the present invention is applied to a structure having the coaxial connector 10 shown in FIG. In the present invention, the signal conductor at the portion penetrating the insulating plate 32, in this example, the structure in which the ground conductor 39 is provided so as to face the peripheral surface of the via hole 35 is provided. The ground conductor 39 can have a columnar shape, for example, like a through hole, and one or more ground conductors can be formed along the peripheral surface of the via hole 35.

By arranging the ground conductor 39 so as to face the via hole 35, the diameter D of the via hole 35 is reduced.
When ground to the diameter d of the conductor 39, a via hole 35 and the gap g and the dielectric constant epsilon _r and the characteristic impedance Z _o of the dielectric material of the insulating plate 32 between the grounding conductor 39
Is defined, and the portion of the via hole 35 operates as a distributed constant circuit element.

FIG. 2 shows a case where the present invention is applied to the structure shown in FIGS. Also in this case, a plurality of ground conductors 39 are formed facing the peripheral surface of the through hole 37, and the portion of the through hole 37 is operated as a distributed constant circuit element. FIG. 3 shows an example of a return loss characteristic of a signal transmission line to which the feedthrough line according to the present invention is applied. As shown, according to the present invention, a return loss of 20 dB or more can be obtained up to about 7 GHz.
Therefore, the practical bandwidth could be expanded to about twice or more the bandwidth of the conventional one.

FIG. 4 shows a modified embodiment of FIG. This embodiment shows a case where the via hole 35 is removed from the embodiment shown in FIG. 1 and the center conductor 12 of the coaxial connector 10 is passed through the insulating plate 32 as it is. Even with such a configuration, return loss characteristics equivalent to those shown in FIG. 3 could be obtained.

[0015]

As described above, according to the present invention, since the portion of the signal conductor penetrating the insulating plate 32 is also operated as a distributed constant circuit element, the impedance mismatching portion can be eliminated in the entire circuit. . Therefore, a transmission line having a wide bandwidth can be obtained without occurrence of reflection. Further, since the ground conductor 39 is arranged in parallel with the signal conductor, the impedance can be matched to a constant value regardless of the thickness t of the insulating plate 32. Therefore, there is an advantage that the manufacturing can be easily performed as compared with the case where the matching circuit shown in FIG. 8 is provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a graph showing return loss characteristics of the feedthrough line according to the present invention.

FIG. 4 is a sectional view showing a modified example of the embodiment shown in FIG. 1;

FIG. 5 is a sectional view for explaining a conventional technique.

FIG. 6 is a sectional view showing another example of the conventional technique.

FIG. 7 is a plan view of FIG. 6;

FIG. 8 is a sectional view showing still another example of the conventional technique.

FIG. 9 is a graph showing a return loss characteristic obtained by the structure shown in FIGS. 5 and 6;

FIG. 10 is a graph showing return loss characteristics obtained by the structure shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Coaxial connector 11 Outer shell 12 Center conductor 13 Insulator 20 Shield case 30 Printed circuit board 31 Microstrip line 32 Insulating plate 33, 34 Ground conductor 35 Via hole (through hole) 36 Solder 37 Through hole 39 Ground conductor

Claims (3)

[Claims] 1. A through line in which a signal conductor penetrates through a hole formed in an insulating plate and electrically connects between one surface and the other surface of the insulating plate. An earth conductor is arranged in parallel with a signal conductor that is inserted and penetrates through a dielectric constituting the insulating plate, and the thickness portion of the insulating plate is configured to operate as a distributed constant circuit. Through type line. 2. A feed-through line according to claim 1, wherein a coaxial connector is mounted on one of said insulating plates, and a center conductor of said coaxial connector passes through said insulating plate and is led out to the other surface. A ground conductor connected to the microstrip line formed on the surface of the insulating plate and parallel to the center conductor penetrating the thickness portion of the insulating plate, and the central conductor of the portion penetrating the insulating plate operates as a distributed constant circuit A penetrating type line characterized by having a configuration in which a line is formed. 3. The feedthrough line according to claim 1, wherein microstrip lines are formed on both sides of the insulating plate, and the microstrip lines are electrically connected to each other by through holes formed through the insulating plate. And a ground conductor is placed in parallel with this through hole.
A through line having a configuration in which the through hole operates as a distributed constant circuit.