JP2008160751A - Microwave circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave circuit board that maintains impedance matching with an electronic component without increasing the width of a metal conductor section on a microwave substrate, reduces the increase in resistance by a skin effect, while suppressing the increase in DC resistance, and can reduce the power loss, reflection energy, and electromagnetic radiation. <P>SOLUTION: The metal conductor section is formed at least on the main surface of the substrate or in the substrate and transmits microwave electrical signals. In the metal conductor section, when the height of the metal conductor section, the skin depth associated with the skin effect of the microwaves flowing in the metal conductor section, the distance between adjacent portions at a plurality of groove sections, each width of the plurality of groove sections, and each depth of the plurality of groove sections are set to ch, δ, w, t, and h, respectively, relational expressions w=2×δ, t=δ, and h=ch-2×δ (1) are satisfied, the microwave circuit board is constituted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a microwave circuit board for transmitting an electrical signal having a frequency in the microwave region.

  In a conventional microwave circuit board, a metal conductor portion through which an electric signal flows is usually formed as a metal conductor having a rectangular or trapezoidal cross section, and a predetermined microwave electric signal is transmitted through the metal conductor. Since the microwave electrical signal is a high-frequency electrical signal in the so-called microwave frequency range, when the microwave electrical signal is transmitted into the metal conductor portion, a so-called skin effect occurs, and the surface of the metal conductor portion It is known that current concentrates in the vicinity (skin depth), the effective resistance of the metal conductor portion with respect to the microwave electrical signal increases, and the power loss also increases.

  The essence of the skin effect described above is electromagnetic induction generated at the metal interface. When the skin effect as described above occurs, the electromagnetic wave entering the metal conductor portion is canceled with the microwave electrical signal. An induced current flows on the surface of the metal conductor portion so as to cancel the electromagnetic wave.

ここで，d は表皮深さ，f は（マイクロ波の）周波数，m は金属導体部の透磁率，s は金属導体部の導電率を表す。 The skin depth in the skin effect is a value that is uniquely determined by the electric conductivity / permeability of the metal conductor portion and the frequency of the AC electric signal (microwave), and this value is an electromagnetic field that has entered the metal conductor portion. The attenuation distance is 1 / e ≒ 1/3 of the original intensity. This is easily derived from the telegraph equation (wave equation) obtained by eliminating the magnetic field from the so-called Maxwell equation. The skin depth is expressed by the following formula.

Where d is the skin depth, f is the frequency (of the microwave), m is the permeability of the metal conductor, and s is the conductivity of the metal conductor.

  As described above, when the skin effect occurs in the metal conductor portion, the effective resistance to the microwave signal transmitted through the metal conductor portion increases, and the power loss also increases. In particular, up to about 1 [GHz]. In a microwave circuit board that transmits a microwave electric signal having a relatively low frequency, the surface area is increased by increasing the width of the metal conductor portion in order to reduce the effective resistance due to the skin effect.

ここで，L は単位長さあたりのインダクタンス，C は単位長さあたりのキャパシタンスを表す。 However, this method increases the so-called characteristic impedance of the line and impedance also exists in electronic components such as ICs and termination resistors that are electrically connected by the substrate, so the line characteristic impedance matches these impedances. If not (more precisely, the complex impedance has a conjugate complex number relationship between the electronic component and the line), not only will the power transfer be performed efficiently, but also the reflection of electromagnetic waves between the electronic component and the line and unnecessary electromagnetic waves. Causes radiation. The characteristic impedance (Z _o ) of the line is expressed by the following equation.

Where L is the inductance per unit length and C is the capacitance per unit length.

  On the other hand, for example, electronic components on boards are being mounted with higher density, and boards are also becoming more multilayered and flexible. However, when the line width increases, high-density mounted boards, multilayer boards, flexible boards, etc. , The mounting area of electronic components is reduced, the degree of freedom of restrictions on the wiring of the line is reduced, and it becomes a limiting condition for downsizing of the entire board, and in turn, downsizing of today's electronic devices using these boards in general It becomes an obstacle.

From such a viewpoint, for example, in Patent Documents 1 and 2, the metal conductor portion as described above is formed in a strip shape along the transmission direction of the microwave electric signal, and the surface area of the metal conductor portion is increased to increase the surface area. The effective resistance is reduced to suppress power loss. In Patent Document 3, a groove portion is provided in the side wall portion of the metal conductor portion as described above along the transmission direction of the microwave electric signal, and the surface area of the metal conductor portion is increased to reduce its effective resistance. To reduce power loss.
JP-A-8-321706 JP-A-6-283910 JP-A-8-288463

  However, in any of the methods described above, a sufficient reduction in effective resistance has not yet been realized. In particular, in the technique for forming the metal conductor portion as described in Patent Documents 1 and 2 in a strip shape, the area of the cross section of the metal conductor portion itself is perpendicular to the transmission direction of the microwave electric signal. As a result, the DC resistance increases, causing a problem of power loss with respect to the original low-frequency electric signal.

  In view of the above-described problems, the present invention is based on the skin effect while maintaining impedance matching with an electronic component and further suppressing an increase in DC resistance without increasing the width of the metal conductor portion of the microwave substrate. An object of the present invention is to provide a microwave circuit board capable of reducing an increase in resistance and reducing power loss, reflected energy, and electromagnetic radiation.

In order to achieve the above object, one embodiment of the present invention provides:
A substrate made of an insulator;
A metal conductor portion for transmitting a microwave electrical signal, formed on at least one of the main surface on the substrate or in the substrate;
A power supply layer formed on at least one of the back surface of the substrate and the substrate,
The metal conductor portion has a plurality of groove portions at least in part, the height of the metal conductor portion is ch, the skin depth associated with the skin effect of the microwave flowing in the metal conductor portion is δ, When the distance between adjacent grooves is w, the width of each of the grooves is t, and the depth of each of the grooves is h,
w = 2 × δ
t = δ (4)
h = ch-2 × δ
It is related with the microwave circuit board characterized by satisfying the following relational expression.

  The present inventor has intensively studied to achieve the above-mentioned problems, and accordingly, a vast amount of experiments are performed, and a vast amount of experimental data obtained thereby is analyzed to find the following facts. That is, in the microwave circuit board in which the metal conductor portion and the power supply layer are arranged at predetermined positions with respect to the insulator substrate, a plurality of groove portions are formed with respect to the metal conductor portion, and the groove portions are (4) By satisfying the relationship such as the expression, the effective resistance due to the skin effect of the microwave electric signal can be sufficiently reduced by increasing the surface area by forming the groove without reducing the DC resistance of the metal conductor. I found it.

  Therefore, according to one embodiment of the present invention, an increase in DC resistance can suppress power loss with respect to an original low-frequency electrical signal, and a high-frequency electrical signal such as a microwave electrical signal. It is also possible to realize a power loss for Furthermore, since the width of the metal conductor portion is not enlarged, it is not necessary to perform complicated design such as impedance matching with the electronic component. Therefore, the problem of an increase in electromagnetic radiation due to impedance mismatching and an accompanying increase in reflected energy does not occur.

  In another aspect of the invention, the plurality of groove portions are formed along the transmission direction of the microwave of the metal conductor portion. In this case, since the groove portion is formed over substantially the entire transmission direction of the microwave electric signal of the metal conductor portion, the above-described effects can be achieved by the microwave electric signal passing through the metal conductor portion. It can be enjoyed throughout the transmission.

  The microwave circuit board can be configured in various ways. For example, the metal conductor portion can be formed as a microstrip line (MSL) on the main surface of the substrate. Further, the metal conductor portion can be formed as a strip line (SL) in the substrate. Further, a pair of ground electrode layers are formed so as to sandwich the metal conductor portion along the length direction thereof substantially parallel to the metal conductor portion, and a coplanar waveguide (by the metal conductor portion and the ground electrode layer). CPW) can be configured.

  In addition, although not specifically illustrated, it can be set as the microwave circuit board of all kinds of aspects which can be conceived by those skilled in the art.

  As described above, according to the above aspect of the present invention, the impedance matching with the electronic component is maintained without increasing the width of the metal conductor portion of the microwave substrate, and further the increase in the DC resistance is suppressed. Thus, it is possible to provide a microwave circuit board capable of reducing an increase in resistance due to the skin effect and reducing power loss, reflected energy, and electromagnetic radiation.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a perspective view showing an example of the microwave circuit board of the present invention, and FIG. 2 is a front view of the microwave circuit board shown in FIG. 1 cut along a plane perpendicular to the length direction. 3 is an enlarged cross-sectional view of the metal conductor portion of the microwave circuit board shown in FIG.

  A microwave circuit substrate 10 shown in FIGS. 1 and 2 includes a substrate 11 made of an insulator, a metal conductor portion 13 for transmitting a microwave electrical signal formed on the main surface of the substrate 11, and a substrate 11. And a power supply layer 15 formed on the back side. The power supply layer 15 serves as a reference electrode for the metal conductor portion 13, is maintained at a constant potential with respect to the metal conductor portion 13, and the microwave electrical signal can be transmitted through the metal conductor portion 13 in a good state. It is for doing so. The power supply layer 15 can be grounded, but is not particularly limited as long as the microwave electric signal can be transmitted through the metal conductor portion 13 satisfactorily, and can be held at an arbitrary potential as described above. .

  In this example, the metal conductor portion 13 is formed as a microstrip line (MSL). A plurality of groove portions 17 are formed in the metal conductor portion 13 along the length direction of the metal conductor portion 13, that is, the transmission direction of the microwave electric signal.

As shown in FIG. 3, when the height of the metal conductor portion 13 is ch, the plurality of groove portions 17 are set such that the interval w, the width t, and the depth h satisfy the following relational expression.
w = 2 × δ
t = δ (5)
h = ch-2 × δ

  Thus, the effective resistance due to the skin effect of the microwave electric signal can be sufficiently reduced by increasing the surface area by forming the groove portion 17 without reducing the DC resistance of the metal conductor portion 13. Actually, if the metal conductor portion 13 is made of copper and a 1 GHz microwave electric signal is transmitted, the skin depth δ in that case is about 2 μm. Therefore, assuming that the height ch = 40 [mm] of the metal conductor portion 13, w = 4 [mm], t = 2 [mm], and h = 36 [mm] from the equation (4). In fact, the DC resistance in such a case was 0.11Ω, and the power loss due to transmission of a 1 GHz microwave electrical signal was 0.11 dB.

  On the other hand, without satisfying the above equation (4), when ch = 40 [mm], w = 2 [mm], t = 87 [mm], h = 38 [mm], the DC resistance is The power loss due to transmission of a 1 GHz microwave electric signal was 0.16 dB. Therefore, it can be seen that satisfying the equation (4) makes it possible to suppress the high-order transmission mode and minimize the power loss due to the skin effect while minimizing the decrease in the DC resistance.

  Further, in this example, since the width of the metal conductor portion 13 is not particularly enlarged, it is not necessary to perform complicated design such as impedance matching with the electronic component. Therefore, the problem of an increase in electromagnetic radiation due to impedance mismatching and an accompanying increase in reflected energy does not occur.

  Furthermore, in this example, since the plurality of groove portions 17 are formed along the length direction of the metal conductor portion 13, that is, the transmission direction of the microwave electric signal, with respect to the metal conductor portion 13, the above-described effects are obtained. It can be enjoyed over the entire transmission range of the microwave electrical signal of the metal conductor portion 13.

  The substrate 11 can be made of a predetermined insulator. Specifically, paper base materials (FR-1, FR-2, XXXpc, Xpc, FR-3, etc.), glass base materials (FR-4, G-10, FR-5, G-11, GPY, etc.) , Epoxy / polyester composite substrates (CEM-1, CEM-3, FR-6, etc.), polyester base / polyimide base / glass epoxy flexible substrate, polysulfone / polyetherimide / polyether Examples thereof include resin heat-resistant plastic substrates, alumina-based / alumina nitride-based / carbon silicon-based / low-temperature sintered ceramic substrates, and liquid crystal substrates.

  Examples of the metal conductor portion 13 and the power supply layer 15 include a good electrical conductor such as copper, silver, gold, aluminum, or an alloy thereof.

  Further, the overall configuration of the microwave circuit board 10 may be a rigid board or a flexible board.

  FIG. 4 is a cross-sectional view showing a modification of the microwave circuit board shown in FIGS. In this example, the configuration shown in FIGS. 1 and 2 is different from the example shown in FIGS. 1 and 2 only in the form of the groove formed in the metal conductor, and the other configurations are the same. Note that the same reference numerals are used for the same or similar components.

  In the example shown in FIGS. 1 and 2, the groove portion 17 is formed from the upper side to the lower side of the metal conductor portion 13, but in this example, as shown in FIG. 4, the side surface of the metal conductor portion 13 is formed. In this case, the outer side is formed from the outside toward the center side. Also in this case, when the height of the metal conductor portion 13 is ch, the plurality of groove portions 17 are set such that the interval w, the width t, and the depth h satisfy the above formula (5).

  Thus, the effective resistance due to the skin effect of the microwave electric signal can be sufficiently reduced by increasing the surface area by forming the groove portion 17 without reducing the DC resistance of the metal conductor portion 13. Further, since the width of the metal conductor portion 13 is not enlarged, it is not necessary to perform complicated design such as impedance matching with the electronic component. Therefore, the problem of an increase in electromagnetic radiation due to impedance mismatching and an accompanying increase in reflected energy does not occur.

  Furthermore, also in this example, if the plurality of groove portions 17 are formed in the metal conductor portion 13 along the length direction of the metal conductor portion 13, that is, the transmission direction of the microwave electric signal, the above-described effects are obtained. Can be enjoyed over the entire transmission range of the microwave electrical signal of the metal conductor portion 13.

  Other requirements such as the constituent materials of the substrate and the metal conductor are the same as those in the above-described specific example, and thus the description thereof is omitted.

  FIG. 5 is a cross-sectional view showing another modification of the microwave circuit board shown in FIGS. In this example, the configuration shown in FIGS. 1 and 2 is different from the example shown in FIGS. 1 and 2 only in the form of the groove formed in the metal conductor, and the other configurations are the same. Note that the same reference numerals are used for the same or similar components.

  In the example shown in FIGS. 1 and 2, the groove portion 17 is formed from the upper side to the lower side of the metal conductor portion 13, but in this example, as shown in FIG. In addition to such vertical grooves, lateral grooves are additionally formed on the side surfaces of the metal conductor 13 from the outside toward the center. Also in this case, when the height of the metal conductor portion 13 is ch, such a plurality of groove portions 17 are set such that the interval w, the width t, and the depth h satisfy the above formula (5). .

Thus, the effective resistance due to the skin effect of the microwave electric signal can be sufficiently reduced by increasing the surface area by forming the groove portion 17 without reducing the DC resistance of the metal conductor portion 13. Further, since the width of the metal conductor portion 13 is not enlarged, it is not necessary to perform complicated design such as impedance matching with the electronic component. Therefore, the problem of an increase in electromagnetic radiation due to impedance mismatching and an accompanying increase in reflected energy does not occur.
Furthermore, also in this example, if the plurality of groove portions 17 are formed in the metal conductor portion 13 along the length direction of the metal conductor portion 13, that is, the transmission direction of the microwave electric signal, the above-described effects are obtained. Can be enjoyed over the entire transmission range of the microwave electrical signal of the metal conductor portion 13.

  FIG. 6 is a perspective view showing another example of the microwave circuit board of the present invention. Note that the same reference numerals as those in the above specific examples are used for the same or similar components.

  A microwave circuit board 10 shown in FIG. 6 is formed in the length direction of the substrate 11 substantially parallel to the main surface and the back surface of the substrate 11 at a substantially central portion in the thickness direction of the substrate 11 made of an insulator. It includes a metal conductor portion 13 for transmitting an extended microwave electrical signal, and a power supply layer 15 formed on the main surface and the back surface side of the substrate 11. The power supply layer 15 serves as a reference electrode for the metal conductor portion 13, is maintained at a constant potential with respect to the metal conductor portion 13, and the microwave electrical signal can be transmitted through the metal conductor portion 13 in a good state. It is for doing so. The power supply layer 15 can be grounded, but is not particularly limited as long as the microwave electric signal can be transmitted through the metal conductor portion 13 satisfactorily, and can be held at an arbitrary potential as described above. .

  In this example, the metal conductor portion 13 is formed as a strip line (SL). Although not particularly shown, the metal conductor portion 13 has a plurality of grooves. Although the structure of this groove part is not specifically limited, For example, a form as shown to FIGS. 3-5 can be taken. Also in this case, when the height of the metal conductor portion 13 is ch, the plurality of groove portions are set such that the interval w, the width t, and the depth h satisfy the above formula (5).

  Thus, the effective resistance due to the skin effect of the microwave electric signal can be sufficiently reduced by increasing the surface area by forming the groove without reducing the DC resistance of the metal conductor portion 13. Further, since the width of the metal conductor portion 13 is not enlarged, it is not necessary to perform complicated design such as impedance matching with the electronic component. Therefore, the problem of an increase in electromagnetic radiation due to impedance mismatching and an accompanying increase in reflected energy does not occur.

  Furthermore, also in this example, if the plurality of groove portions are formed along the length direction of the metal conductor portion 13, that is, the transmission direction of the microwave electric signal, with respect to the metal conductor portion 13, the above-described effects can be obtained. It can be enjoyed over the entire transmission range of the microwave electrical signal of the metal conductor portion 13.

  Other requirements such as the constituent materials of the substrate and the metal conductor are the same as those in the above-described specific example, and thus the description thereof is omitted.

  FIG. 7 is a perspective view showing another example of the microwave circuit board of the present invention. Note that the same reference numerals as those in the above specific examples are used for the same or similar components.

  A microwave circuit board 10 shown in FIG. 7 includes a substrate 11 made of an insulator, a metal conductor 13 for transmitting a microwave electrical signal formed on the main surface of the substrate 11, and a back surface of the substrate 11. And a power supply layer 15 formed on the side. The power supply layer 15 serves as a reference electrode for the metal conductor portion 13, is maintained at a constant potential with respect to the metal conductor portion 13, and the microwave electrical signal can be transmitted through the metal conductor portion 13 in a good state. It is for doing so. The power supply layer 15 can be grounded, but is not particularly limited as long as the microwave electric signal can be transmitted through the metal conductor portion 13 satisfactorily, and can be held at an arbitrary potential as described above. .

  In this example, a pair of ground electrode layers 19 are formed on both sides of the metal conductor portion 13 so as to sandwich the metal conductor portion 13, and the coplanar wave is formed by the metal conductor portion 13 and the ground electrode layer 19. It constitutes a guide (CPW).

  Although not particularly shown, the metal conductor portion 13 has a plurality of grooves. Although the structure of this groove part is not specifically limited, For example, a form as shown to FIGS. 3-5 can be taken. Also in this case, when the height of the metal conductor portion 13 is ch, the plurality of groove portions are set such that the interval w, the width t, and the depth h satisfy the above formula (5).

  Thus, the effective resistance due to the skin effect of the microwave electric signal can be sufficiently reduced by increasing the surface area by forming the groove without reducing the DC resistance of the metal conductor portion 13. Further, since the width of the metal conductor portion 13 is not enlarged, it is not necessary to perform complicated design such as impedance matching with the electronic component. Therefore, the problem of an increase in electromagnetic radiation due to impedance mismatching and an accompanying increase in reflected energy does not occur.

  Furthermore, also in this example, if the plurality of groove portions are formed along the length direction of the metal conductor portion 13, that is, the transmission direction of the microwave electric signal, with respect to the metal conductor portion 13, the above-described effects can be obtained. It can be enjoyed over the entire transmission range of the microwave electrical signal of the metal conductor portion 13.

  Other requirements such as the constituent materials of the substrate and the metal conductor are the same as those in the above-described specific example, and thus the description thereof is omitted.

  The present invention has been described in detail based on the above specific examples. However, the present invention is not limited to the above specific examples, and various modifications and changes can be made without departing from the scope of the present invention.

It is a perspective view which shows an example of the microwave circuit board of this invention. FIG. 2 is a front view of the microwave circuit board shown in FIG. 1 when cut by a plane perpendicular to the length direction. It is sectional drawing which expands and shows the metal conductor part of the microwave circuit board shown in FIG. It is sectional drawing which shows the modification of the metal conductor part of the microwave circuit board shown in FIG. It is sectional drawing which shows the other modification of the metal conductor part of the microwave circuit board shown in FIG. It is a perspective view which shows the other example of the microwave circuit board of this invention. It is a perspective view which shows the other example of the microwave circuit board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Microwave circuit board 11 (Insulator) board | substrate 13 Metal conductor part 15 Power supply layer 17 Groove part 19 Ground electrode

Claims (5)

A substrate made of an insulator;
A metal conductor portion for transmitting a microwave electrical signal, formed on at least one of the main surface on the substrate or in the substrate;
A power supply layer formed on at least one of the back surface of the substrate and the substrate,
The metal conductor portion has a plurality of groove portions at least in part, the height of the metal conductor portion is ch, the skin depth associated with the skin effect of the microwave flowing in the metal conductor portion is δ, When the distance between adjacent grooves is w, the width of each of the grooves is t, and the depth of each of the grooves is h,
w = 2 × δ
t = δ (1)
h = ch-2 × δ
A microwave circuit board characterized by satisfying the following relational expression:   The microwave circuit board according to claim 1, wherein the plurality of groove portions are formed along a transmission direction of the microwave of the metal conductor portion.   The microwave circuit board according to claim 1, wherein the metal conductor portion is formed as a microstrip line (MSL) on a main surface of the substrate.   3. The micro circuit board according to claim 1, wherein the metal conductor portion is formed as a strip line (SL) in the substrate.   A pair of ground electrode layers are formed so as to sandwich the metal conductor portion along the length direction thereof substantially parallel to the metal conductor portion, and a coplanar waveguide (CPW) is formed by the metal conductor portion and the ground electrode layer. The microwave circuit board according to claim 1, wherein the microwave circuit board is configured as follows.

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