JPH10200311A - Coplanar waveguide line with back ground conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain impedance matching of input and output terminals, and to improve reflection characteristics in a high frequency range in a coplanar waveguide line with a back ground conductor. SOLUTION: A signal line conductor 13 and first and second ground conductors 11 and 12 are formed on the upper face side of a dielectric substrate 15, a third ground conductor 16 is formed on the lower face side, and a CPW line is formed of those conductors. The first and second ground conductors 11 and 12 are formed so as to be separated in an equal distance with the signal line conductor 13 interposed between them. The first, second, and third ground conductors 11, 12, and 16 are electrically connected through a first through hole 14 so that their potentials can be made equal. Moreover, the first and second ground conductors 11 and 12 and the third ground conductor 16 are electrically connected through a second through hole 17 formed like a long groove from input and output edge faces 15a and 15b of the dielectric substrate 15 to the neighborhood of the edge faces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coplanar waveguide with a grounded backside conductor, and more particularly to an improved input / output reflection characteristic in a high frequency range.

[0002]

2. Description of the Related Art Conventionally, as a line for transmitting a high-frequency electric signal, a coplanar wave guide line (hereinafter referred to as a coplanar wave guide line) has been used because of its low dispersion characteristics, low radiation loss, low impedance, and little influence from variations in substrate thickness. , CPW lines). The CPW line is generally formed by forming a signal line conductor on a dielectric substrate and forming a ground conductor at a predetermined interval on both sides of the signal line conductor.However, since it is easy to ground when packaged, for example, "June 1982, Electronics Letters, Vol. 18, No. 12, 53
8-540 pages, (ELECTRONICS LETTERS, VOL.18, NO.12, PP.53
8-540, JUNE, 1982] and 1991, I.E.M.T.T.S.T.T.I.S., p. 1063-1066 (IEEE MTT-SDIGEST, P.
P.1063-1066], a ground conductor is also formed on the back side of the CPW line, and a CPW line with a back side ground conductor electrically connected to the ground conductor on the front side is often used. I have.

FIGS. 19 to 21 show an example of a conventional CPW line with a back ground conductor. In these figures, this C
The PW line includes a dielectric substrate 75 made of alumina or the like,
A circuit pattern is formed on the front and back surfaces by a printed wiring technique. That is, this circuit pattern is formed by the CPW by the signal line conductor 73 and the first and second ground conductors 71 and 72 formed on the front surface side of the dielectric substrate 75 and the third ground conductor 76 formed on the back surface side. The line is formed. The first, second, and third ground conductors 71, 72, and 76 are generally electrically connected to each other by through holes 74 in which conductors 77 are filled in through holes of a dielectric substrate 75 so as to make the potentials equal. In addition, in order to make the electromagnetic field distribution of a transmitted signal symmetrical, as shown in FIG. 19, through holes 74 are formed symmetrically at equal intervals along the line as shown in FIG.

[0004]

However, in the conventional CPW line with the back surface ground conductor having the above-described structure, the first and second ground conductors 7 are formed by the through holes 74.
There are places where the first and second conductors 72 and the third ground conductor 76 are electrically connected (FIG. 21) and where there is no ground (FIG. 20) along the line. For this reason, when the signal to be transmitted is in a high frequency range, the first and second ground conductors 71 and 7
2, a potential distribution occurs, and the potential gradually displaces along the line. As a result, the characteristic impedance of the line also changes gradually along the line, and when the line is electrically grounded by the through hole 74 located on the NN line in FIG. However, between the through-holes 74 on the line MM in FIG. 19, in other words, at a portion that is not electrically connected by the through-holes, the value is the most deviated from the desired characteristic impedance. As a result, reflection occurs at every part of the line in the high frequency range. In particular, if the first ground conductor 71 or the second ground conductor 72 and the third ground conductor 76 are not electrically connected in the vicinity of the input and output, the impedance of the input / output end face with the external circuit may be low. There is a problem that matching occurs and the reflection loss in a high frequency region is larger than that in a low frequency region.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a coplanar wave guide line with a grounded back conductor having excellent input and output reflection characteristics in a high frequency range. Is to do.

[0006]

According to a first aspect of the present invention, a signal line conductor formed on one surface of a dielectric substrate and a predetermined distance between both sides of the signal line conductor with the signal line conductor interposed therebetween. A first and second ground conductors formed only apart from each other, and a coplanar waveguide guide line with a back ground conductor having a third ground conductor formed on the other surface of the dielectric substrate; At least one of the second ground conductors is electrically connected to the third ground conductor at an input end face of the dielectric substrate, and the at least one of the first and second ground conductors is connected to the input end face of the dielectric substrate. The third ground conductor is electrically connected to an output end face of the dielectric substrate. In a second aspect based on the first aspect, the means for electrically connecting at least one of the first and second ground conductors and the third ground conductor includes an input of the dielectric substrate. It is a through hole reaching the end face or the output end face. Also, the third
The invention according to the first aspect, wherein the means for electrically connecting at least one of the first and second ground conductors and the third ground conductor includes an input end face of the dielectric substrate or an output end. It is a plating layer formed on an end face. According to a fourth aspect of the present invention, there is provided a signal line conductor formed on one surface of a dielectric substrate, and first and second signal line conductors formed on both sides of the signal line conductor with a predetermined distance therebetween.
In a coplanar waveguide guide line with a back ground conductor having a second ground conductor and a third ground conductor formed on the other surface of the dielectric substrate,
By forming a plating layer on a side surface orthogonal to the output end surface, the first and second ground conductors and the third ground conductor are electrically connected from the input end to the output end, respectively.
The width of the first and second ground conductors is substantially equal to the width of the signal line conductor. In a fifth aspect based on the fourth aspect, the two side surfaces orthogonal to the input and output end faces of the dielectric substrate and opposed to each other are sandwiched by two conductive substrates, and the first and second conductive substrates are sandwiched by these conductive substrates.
And the third ground conductor are electrically connected from the input end to the output end.

At least one of the first and second ground conductors is electrically connected to the third ground conductor at the input end face of the dielectric substrate, and at least one of the first and second ground conductors is connected. If one of them is electrically connected to the third ground conductor at the output end face of the dielectric substrate, the characteristic impedance value at the input and output end faces can be kept constant over a wide frequency range. The impedance mismatch at the input and output end faces is eliminated, and the return loss can be reduced. In this case, it is more preferable that the first and second ground conductors and the third ground conductor are electrically connected at the input and output terminals. Further, the conductor widths of the first and second ground conductors are reduced to about the signal line width, and the first and second ground conductors are electrically connected to the third ground conductor from the input end to the output end. In this way, as described above, the impedance mismatch can be eliminated, and the return loss can be reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a perspective view showing a first embodiment of a coplanar wave guide line with a grounded back conductor according to the present invention, FIG. 2 is a sectional view taken along line AA of FIG.
3 is a sectional view taken along line BB of FIG. 1, and FIG. 4 is a sectional view taken along line CC of FIG. In these figures, a signal line conductor 13 and first and second ground conductors 11 and 12 are formed on an upper surface side of a dielectric substrate 15, and a third ground conductor 1 and 12 are formed on a lower surface side.
6 are formed, and these conductors form a CPW line. The first and second ground conductors 11 and 12 are formed on both sides of the signal line conductor 13 at equal distances.

The dielectric substrate 15 has a thickness of 250 μm.
m alumina thin plate is used, and the signal line width is 240 μm.
m, the signal line conductor 13, the first ground conductor 11, and the second
The distance from the ground conductor 12 is 400 μm, and the line length is 900
μm. Also, the first, second, and third ground conductors 11,
In order to make the potentials of 12 and 16 equal, they were electrically connected by the first through hole 14. Here, the first through hole 14 (the same applies to a second through hole 17 to be described later) is formed by plating the wall surface of a through hole formed in the dielectric substrate 15 or a conductor is provided inside the through hole. Defined as filled. The hole diameter of the first through hole 14 is 15 μm, and the interval between adjacent through holes in the longitudinal direction of the line is 450 μm. And the dielectric substrate 1
5 at the input and output end faces 15a, 15b.
The ground conductors 11 and 12 are electrically connected to the third ground conductor 16 by second through holes 17 formed in a long groove shape from the end face to the vicinity of the end face. Second
Are open to the upper and lower surfaces of the dielectric substrate 15 and three surfaces of the input end surface or the output end surface. The shape is not limited to a U-shape, but may be any shape such as a V-shape.

In the coplanar wave guide line with the back surface ground conductor having such a configuration, the first and second end faces 15a and 15b of the dielectric substrate 15 are provided.
Are electrically connected to the third ground conductors 16 through the second through holes 17.
The characteristic impedance value at the input and output end faces can be made constant over a wide frequency range. As a result, impedance mismatch at the input and output end faces with an external circuit can be eliminated, and the return loss can be reduced. .

[0011] Figure 22 is a diagram showing the S ₁₁ characteristics obtained as a result of performing an electromagnetic field analysis (input reflection characteristic) for line according to the present invention shown in the conventional line and Figure 1 shown in FIG. 19, From this figure, it can be seen that the effect of the improvement according to the present invention is remarkably exhibited in a high frequency range.

FIG. 5 is a perspective view of a coplanar wave guide line with a grounded back conductor showing a second embodiment of the present invention, FIG. 6 is a sectional view taken along line DD of FIG. 5, and FIG. E
8 is a sectional view taken along line FF of FIG. In these figures, 25 is a dielectric substrate, 23 is a signal line conductor, 21, 22, and 26 are first, second, and third ground conductors. These conductors form a CPW line, and the first and second ground conductors are formed. In order to make the potentials of the second and third ground conductors 21, 22, 26 equal, they are electrically connected by the first through hole 24. The through hole 24 formed on the first ground conductor 21 side and the through hole 24 formed on the second ground conductor 22 side are shifted by a half pitch in the longitudinal direction of the line. The first grounding conductor 21 is electrically connected to the third grounding conductor 26 at the output end face of the dielectric substrate 25, and the second grounding conductor 22 is electrically connected to the third grounding conductor 26 by the second through hole 27 formed in the input end face. It is connected to the.

[0013] In the coplanar waveguide line with the grounded back conductor having such a configuration, the characteristic impedance value at the input and output end faces is kept constant over a wide frequency range, similarly to the line shown in the first embodiment. Value, the impedance mismatch at the input / output end face with the external circuit is eliminated, and the reflection loss can be reduced.

[0014] Figure 23 is a diagram showing the S ₁₁ characteristics obtained as a result of performing electromagnetic field analysis on the line according to the present invention shown in the conventional line and 5 shown in FIG. 19, in the high frequency range, The effect of the improvement according to the present invention is remarkably exhibited.

FIG. 9 is a perspective view of a coplanar wave guide line with a grounded back conductor showing a third embodiment of the present invention, FIG. 10 is a sectional view taken along line GG of FIG. 9, and FIG.
FIG. 4 is a sectional view taken along line -H. In these figures, 35 is a dielectric substrate, 33 is a signal line conductor, 31, 32, and 36 are first, second, and third ground conductors. These conductors form a CPW line. Second and third ground conductors 3
In order to make the potentials of 1, 32 and 36 equal, they are electrically connected by through holes 34. Particularly, in order to electrically connect the first and second ground conductors 31 and 32 and the third ground conductor 36 at the input and output ends, a plating layer 37 is formed on the input and output end faces of the dielectric substrate 35, respectively. Has formed. Even in such a configuration, the same effects as those of the first and second embodiments can be obtained.

FIG. 12 is a perspective view of a coplanar wave guide line with a grounded back conductor showing a fourth embodiment of the present invention, FIG. 13 is a sectional view taken along the line II of FIG. 12, and FIG.
FIG. 7 is a sectional view taken along line JJ of FIG. In these figures, 45 is a dielectric substrate, 43 is a signal line conductor, 41, 42, and 46 are first, second, and third ground conductors. These conductors form a CPW line. In order to equalize the potentials of the second and third ground conductors 41, 42, 46, they are electrically connected by through holes 44. In particular, a plating layer 47 for electrically connecting the first ground conductor 41 and the third ground conductor 46 at the input end, and a plating layer 47 for electrically connecting the second ground conductor 42 and the third ground conductor 46 at the output end, respectively. Dielectric substrate 45
Are formed on the input and output end faces, respectively. Even in such a configuration, it is possible to reduce the reflection loss in a high-frequency range as in the above-described embodiment.

FIG. 15 is a perspective view of a coplanar wave guide line with a back surface ground conductor showing a fifth embodiment of the present invention, and FIG. 16 is a sectional view taken along the line KK of FIG. In these figures, 55 is a dielectric substrate, 53 is a signal line conductor,
Reference numerals 51, 52, and 56 denote first, second, and third ground conductors. These conductors form a CPW line.
In order to equalize the potentials of the second and third ground conductors 51, 52, and 56, the plating layer 54 is formed on two side surfaces orthogonal to the input and output end faces of the dielectric substrate 55 and opposed to each other. , The second ground conductors 51 and 52 and the third ground conductor 56 are electrically connected from the input terminal to the output terminal. Also, the first and second ground conductors 51 and 52
Is made as narrow as the width of the signal line conductor 53. Specifically, the width of the first and second ground conductors 51 and 52 is set to 10
It was set to 0 μm. Even in such a configuration, it is possible to reduce the reflection loss in a high-frequency range as in the above-described embodiment.

FIG. 17 is a perspective view of a coplanar wave guide line with a back surface ground conductor showing a sixth embodiment of the present invention, and FIG. 18 is a sectional view taken along line LL of FIG. In these figures, 65 is a dielectric substrate, 63 is a signal line conductor,
61, 62 and 66 are first, second and third ground conductors, which form a CPW line.
The widths of the first and second ground conductors 61 and 62 are set to be as narrow as the width of the signal line conductor 63. Further, two side surfaces orthogonal to the input and output end surfaces of the dielectric substrate 65 are sandwiched between two metal substrates 64 having the same thickness as the dielectric substrate 65, and the first and second ground conductors 61, 62 and the third ground conductor 66 are electrically connected from the input end to the output end. Even in such a configuration, it is possible to reduce the reflection loss in a high-frequency range as in the above-described embodiment.

In the above-described embodiments, all of the dielectric substrates 15, 25, 35, 45, 55, 65
Although alumina was used as the material of the above, the present invention is not limited to this, and any dielectric material may be used. Further, the signal line width, the distance between the signal line and the first and second ground conductors, the diameter of the through-hole, and the distance between adjacent through-holes are not limited to the above numerical values.

[0020]

As described above, the coplanar wave guide line with the back surface grounding conductor according to the present invention has a signal line conductor formed on one surface of a dielectric substrate and predetermined portions on both sides of the signal line conductor. And a third ground conductor formed on the other surface of the dielectric substrate, wherein the first and second ground conductors are formed apart from each other by a distance of At least one of the first and second ground conductors is electrically connected to the third ground conductor at an input end face of the dielectric substrate, and at least one of the first and second ground conductors is connected. Since one and the third ground conductor are electrically connected at the output end face of the dielectric substrate, the characteristic impedance value at the input and output ends can be kept constant over a wide frequency range. Can, as a result, the input of an external circuit,
The impedance mismatch at the output end is eliminated, and the input and output reflection characteristics can be improved.

According to the present invention, there is provided a signal line conductor formed on one surface of a dielectric substrate, and first and second grounds formed on both sides of the signal line conductor with a predetermined distance therebetween. In a coplanar waveguide line having a conductor and a third ground conductor formed on the other surface of the dielectric substrate, a plating layer is provided on a side surface orthogonal to the input and output end surfaces of the dielectric substrate. By forming the first and second ground conductors, the first and second ground conductors are electrically connected from the input end to the output end, respectively.
Since the widths of the first and second ground conductors are made substantially equal to the width of the signal line conductor, the characteristic impedance value can be made constant over a wide frequency range as in the above invention. And the impedance mismatch at the input and output terminals is eliminated, and the input and output reflection characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a coplanar waveguide line with a grounded back conductor according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a sectional view taken along line CC of FIG. 1;

FIG. 5 is a perspective view of a coplanar wave guide line with a grounded back surface according to a second embodiment of the present invention.

FIG. 6 is a sectional view taken along line DD of FIG. 5;

FIG. 7 is a sectional view taken along line EE of FIG. 5;

FIG. 8 is a sectional view taken along line FF of FIG. 5;

FIG. 9 is a perspective view of a coplanar wave guide line with a grounded back surface according to a third embodiment of the present invention.

FIG. 10 is a sectional view taken along line GG of FIG. 9;

FIG. 11 is a sectional view taken along line HH of FIG. 9;

FIG. 12 is a perspective view of a coplanar wave guide line with a grounded back conductor according to a fourth embodiment of the present invention.

13 is a sectional view taken along line II of FIG.

FIG. 14 is a sectional view taken along line JJ of FIG.

FIG. 15 is a perspective view of a coplanar wave guide line with a grounded back conductor according to a fifth embodiment of the present invention.

16 is a sectional view taken along line KK of FIG.

FIG. 17 is a perspective view of a coplanar waveguide line with a grounded back surface according to a sixth embodiment of the present invention.

18 is a sectional view taken along line LL of FIG. 17;

FIG. 19 is a perspective view showing a conventional coplanar wave guide line with a back ground conductor.

FIG. 20 is a sectional view taken along line MM of FIG. 19;

FIG. 21 is a sectional view taken along line NN of FIG. 19;

22 is a diagram showing the S ₁₁ characteristics of the first embodiment of the prior art and the present invention.

23 is a diagram showing the S ₁₁ characteristic of the second embodiment of the prior art and the present invention.

[Explanation of symbols]

11, 21, 31, 41, 51, 61 ... first ground conductor, 12, 22, 32, 42, 52, 62 ... second ground conductor, 13, 23, 33, 43, 53, 63 ... signal line Conductor, 14... First through hole, 15, 25, 35,
45, 55, 65: dielectric substrate, 16, 26, 36, 4
6, 56, 66 ... third ground conductor, 14, 24 ... first through hole, 17, 27 ... second through hole, 3
7, 47, 54: plating layer; 64: metal substrate.

Claims (5)

[Claims] 1. A signal line conductor formed on one surface of a dielectric substrate, and first and second ground conductors formed on both sides of the signal line conductor and separated by a predetermined distance, and A coplanar wave guide line with a back ground conductor having a third ground conductor formed on the other surface of the dielectric substrate, wherein at least one of the first and second ground conductors and the third ground conductor are provided. A conductor is electrically connected at an input end face of the dielectric substrate, and at least one of the first and second ground conductors and the third ground conductor are electrically connected at an output end face of the dielectric substrate. A coplanar wave guide line with a grounded back surface conductor, characterized by being electrically connected. 2. The coplanar waveguide with a back ground conductor according to claim 1, wherein the means for electrically connecting at least one of the first and second ground conductors to the third ground conductor comprises: A coplanar wave guide line with a grounded back conductor, characterized in that the through hole extends to the input end face or the output end face of the dielectric substrate. 3. The coplanar waveguide with a back ground conductor according to claim 1, wherein the means for electrically connecting at least one of the first and second ground conductors to the third ground conductor is provided. A coplanar waveguide line with a grounded back conductor, characterized in that it is a plating layer formed on an input end face or an output end face of a dielectric substrate. 4. A signal line conductor formed on one surface of a dielectric substrate, and first and second ground conductors formed on both sides of the signal line conductor and separated by a predetermined distance, and In a coplanar wave guide line with a back surface ground conductor having a third ground conductor formed on the other surface of the dielectric substrate, a plating layer is formed on a side surface orthogonal to the input and output end surfaces of the dielectric substrate. The first and second ground conductors and the third ground conductor are electrically connected from the input end to the output end, respectively, and the width of the first and second ground conductors is set to the width of the signal line conductor. A coplanar wave guide line with a conductor grounded on the back side, characterized by being substantially equal to the above. 5. The coplanar waveguide with a grounded back conductor according to claim 4, wherein two side surfaces orthogonal to and opposite to the input and output end faces of the dielectric substrate are sandwiched between the two conductive substrates. A coplanar wave guide line with a back surface ground conductor, wherein the first, second and third ground conductors are electrically connected from the input terminal to the output terminal, respectively.