JP2010081507A - Directional coupler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact directional coupler capable of making high power pass therethrough. <P>SOLUTION: There are provided a main line 2 including a microstrip line formed on a first dielectric substrate 1 and a sub line 4 including a microstrip line formed on a second dielectric substrate 3 arranged with a gap between from the main line 2, and a projection is formed at the sub line 4, and coupling by an electric field and coupling by a magnetic field can be adjusted by the projection, and therefore, it is possible to obtain a compact directional coupler having a sufficient directive property. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a directional coupler for detecting microwave power, and more particularly to a directional coupler formed by a microstrip line.

  In the past, electronic circuits have become smaller and more integrated, and it has been desired to reduce the size of each component. Directional couplers are also known as one of the component components that are also desired to be reduced in size. ing.

  The directional coupler is used as a power detector for microwaves or the like, and is required to have sufficient directivity to be able to detect traveling wave power and reflected wave power separately.

  In general, a directional coupler using a microstrip line is well known to have a configuration using a quarter wavelength coupled line as shown in FIG. 10, but the length of the quarter wavelength of a signal detected by the coupled line part is known. Therefore, the size is limited by the frequency of the signal to be detected.

Further, for example, Patent Document 1 discloses a CM type directional coupler in which a main line and a sub line are covered with a glass substrate for miniaturization. In the directional coupler of Patent Document 1, a CM-type directional coupler is formed by glass that is a dielectric, and the conventional ¼-wavelength coupled line-type directional coupler is not mounted. The occupied area can be reduced to 1/10.
JP-A-6-45811

  However, the directional coupler having the configuration described in the above-mentioned Patent Document 1 has an insertion loss, so that it is very difficult to reduce the size in order to pass a large power of, for example, several hundred watts. In this case, the loss increases exponentially, and a special heat dissipation structure is required. Also, in the 1/4 wavelength coupled line type directional coupler, the structure is limited to the detection wavelength, and sufficient miniaturization is not achieved, or the corner mode mode is used because the main line and the sub line are arranged on the same dielectric substrate. There is a problem that it is difficult to obtain sufficient directionality because the phase speeds of excitation and odd mode excitation are different.

  In view of such problems, an object of the present invention is to provide a directional coupler that can obtain a large amount of passing power and can be miniaturized.

  In order to solve the above-described conventional problems, a directional coupler according to the present invention includes a main line made of a microstrip line formed on a first dielectric substrate, and a first line disposed with a gap in the main line. And a sub-line made of a microstrip line formed on a dielectric substrate, and the sub-line is provided with a convex portion.

  Accordingly, since the coupling by the electric field and the coupling by the magnetic field can be adjusted by the convex portion, it is possible to realize a small directional coupler having sufficient directivity.

  Since the directional coupler of the present invention can adjust the coupling by the electric field and the coupling by the magnetic field by the convex portion, it is possible to realize a small directional coupler having sufficient directionality.

  According to a first aspect of the present invention, there is provided a main line composed of a microstrip line formed on a first dielectric substrate, and a microstrip line formed on a second dielectric substrate disposed on the main line with a gap. The sub-line is provided with a convex portion on the sub-line so that the coupling by the electric field and the coupling by the magnetic field can be adjusted by the convex portion, so that the direction has sufficient directionality. A sex coupler can be realized.

  In the second invention, in particular, a part of the convex portion provided in the sub-line of the first invention has an overlapping portion in the vertical direction of the main line and the substrate, so that the coupling by the electric field and the magnetic field by the convex portion. Therefore, the directional coupler having sufficient directivity can be realized.

  According to the third aspect of the invention, in particular, the convex portion provided on the sub-line of the first aspect of the invention has a configuration in which there is no overlapping portion in the vertical direction of the main line and the substrate, so that the convex portion is coupled by an electric field and a magnetic field. The coupling can be adjusted, and the coupling degree can be adjusted by adjusting the distance between the main and sub lines so that there is no overlapping part, and a directional coupler with sufficient directionality is realized. be able to.

  According to a fourth aspect of the invention, in particular, the gap between the sub-line and the main line of the first to third aspects is set to 2 mm or more, so that the coupling by the electric field and the coupling by the magnetic field is adjusted by the convex portion with a small size. Since the distance between the main line and the sub line is 2 mm or more, a directional coupler that does not greatly affect the characteristic impedance of the main line can be realized.

  In the fifth aspect of the invention, in particular, the convex portion of the fourth aspect of the invention has a sufficient directionality since the coupling by the electric field and the coupling by the magnetic field can be made the best state by setting the convex portion to 5 mm to 8 mm. A directional coupler can be realized.

  In the sixth aspect of the invention, in particular, the distance between the patterns of the convex portions of the fifth invention is 0.5 mm or less, so that the coupling by the electric field and the coupling by the magnetic field can be brought to the best state by the convex portions, so that sufficient directivity is achieved. A directional coupler having the following can be realized.

  According to the seventh aspect of the invention, in particular, by providing a metal shield member around the second dielectric substrate of the first to fourth aspects, the influence of an external electric field and magnetic field can be cut off. A directional coupler with high detection accuracy can be provided.

  In an eighth aspect of the invention, in particular, the second dielectric substrate is held by the metal shield member of the seventh aspect of the invention, and the distance from the first dielectric substrate is secured, so that an electric field from the outside can be obtained. Further, the influence of the magnetic field is cut off to improve the detection accuracy, and the distance between the substrates can be fixed by the shield member, so that it is possible to provide a directional coupler that suppresses variations during manufacturing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 and 2 are configuration diagrams of a directional coupler according to the first embodiment of the present invention. FIG. 1 is a plan view of the present embodiment, and FIG. 2 is a cross-sectional view taken along lines A1-A2 and B1-B2 of FIG. The present embodiment is configured to be used in the case of handling several hundred W of passing power at a frequency of about 2 GHz to 3 GHz.

  1 and 2, the directional coupler is disposed on the main line 2 configured on the first dielectric substrate 1 and on the second dielectric substrate 3 disposed to face the main line 2. And a metal shield 5 that covers the second dielectric substrate 3 including the sub line 4. The main line 2 has a back surface covered with a conductor surface having a ground potential, and has a characteristic impedance of a line width of approximately 50Ω. The sub-line 4 is arranged on the second dielectric substrate 3 and a part of the sub-line 4 protrudes, and the protruding part has a gap that partially overlaps the main line 2 in the vertical direction. Are arranged.

  About the directional coupler comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  When the high frequency power passes through the main line 2, an electric field and a magnetic field corresponding to the high frequency power are generated around it. The generated electric field and magnetic field are combined with the sub line 4 to generate signals at the A end and the B end of the sub line 4. The electromotive force generated in the convex portion of the sub-line 4 by the electric field is proportional to the electric field generated by the main line 2, and the electromotive force generated by this electric field becomes as shown in FIG. A voltage is generated at the A and B terminals. If these voltages are VA1 and VB1, respectively, the relationship of VA1 = VB1 is established.

  Next, since a magnetic field is generated between A and B by a magnetic field interlinking the convex portions, if a predetermined impedance is connected to the A and B ends, it can be observed as a voltage at the A and B ends. . FIG. 4 shows an equivalent circuit at this time, and assuming that the voltages at this time are VA2 and VB2, the relationship of VA2 = −VB2 is established. By superimposing the above relations, when VA1 and VA2 are in the direction of adding, VB1 and VB2 are in the direction of subtraction, so the shape of the convex portion and the first dielectric substrate 1 so that VB1 = −VB2. By arranging the distance between the second dielectric substrate 3 and the second dielectric substrate 3 in the best condition, a directional coupler that outputs a signal to one of the sub-lines 4 and does not output a signal to the other can be formed.

  FIG. 5 is a characteristic diagram showing an example of actual measurement of characteristics in the first embodiment. In the figure, the horizontal axis represents frequency, and the vertical axis represents traveling wave power Pf, reflected wave power Pr, and insertion loss in decibels. The frequency in the actual measurement is 2 GHz to 3 GHz. The insertion loss is approximately −0.2 dB or less over the measurement frequency band, and almost no loss occurs even when several hundreds of watts of power is passed. For example, even when 200 W of electric power is passed, only a loss of about 9 W or less is generated, and it is a value that can sufficiently dissipate heat and can be put to practical use. Further, the degree of coupling indicating the detection sensitivity for detecting the traveling wave power Pf and the degree of separation for detecting the reflected wave power Pr are approximately −30 dB and approximately −60 dB, respectively. As a result, the directionality is always 20 dB or more. Therefore, the traveling wave power and the reflected wave power can be sufficiently separated, and the directionality is good.

  The characteristics shown in FIG. 5 are that the first dielectric substrate 1 is a Teflon (registered trademark) substrate, the second dielectric substrate 3 is a CEM3 substrate, the distance between the two substrates is 2 mm, and the sub-line 4 is provided. The interval between the parallel portions of the convex portions is 0.5 mm. Since the line width of the sub line 4 is 1.5 mm in order to make its characteristic impedance approximately 50Ω, the width of the directional coupler can be configured to be 10 mm or less. Compared to a directional coupler using a sexual coupler, the size can be significantly reduced. Moreover, since it is not the structure which inserts and adds components to the main line 2, the heat_generation | fever by passing electric power does not become a problem, and a very small and directional coupler with good directivity can be obtained.

FIG. 6 shows a change in impedance of the main line 2 when the distance between the first dielectric substrate 1 and the second dielectric substrate 3 is changed. From this figure, when the distance between the two substrates is close to less than 2 mm, the influence of the second dielectric substrate 3 appears in the main line 2 and the impedance changes greatly. When impedance mismatching occurs on the microwave line, power is reflected at the impedance mismatching point, which may cause adverse effects on surrounding components due to the reflected power. For this reason, in the directional coupler of the present invention, it is desirable that the distance between the substrates is 2 mm or more in order to suppress fluctuations in the characteristic impedance of the main line to several ohms or less.

  FIG. 7 shows an actual measurement characteristic diagram of the directional coupler when the inter-pattern distance d of the parallel portion 4a of the convex portion is changed. This figure shows the difference between the degree of coupling indicating the sensitivity for detecting the traveling wave power Pf and the degree of separation for detecting the reflected wave power Pr, and this figure can represent the directional characteristics of the directional coupler. From this figure, it is shown that the directionality deteriorates when the inter-pattern distance d is increased. This is because by increasing the inter-pattern distance d, a phase difference occurs in the induced electromotive force due to the electric field generated in the convex portion in this portion, and the equivalent circuit shown in FIGS. 3 and 4 simply cannot be established. It can be considered that the directionality has deteriorated. For this reason, it is desirable that the distance between adjacent patterns in the convex portion be as close as possible. Generally, in the pattern design of a printed circuit board, a good finished state can be obtained relatively easily when the distance between patterns is 0.25 mm or more. It is desirable to be 25 mm or more and 0.5 mm or less.

  Moreover, in the directional coupler of this structure, since it has the structure which can add the subline 4 which detects the electric power which transmits the main line 2 to the main line 2 which transmits electric power later, it transmits by the subline 4. The second dielectric substrate 3 including the sub line 4 can be disposed at an arbitrary position of the main line 2 having a length sufficient to detect electric power, and the installation position of the directional coupler can be set at an arbitrary position. The degree of freedom of mounting the board can be improved.

(Embodiment 2)
8 and 9 are configuration diagrams of a directional coupler according to the second embodiment of the present invention. 8 is a plan view of the present embodiment, and FIG. 9 is a cross-sectional view taken along lines A1-A2 and B1-B2 of FIG. The present embodiment is configured to be used in the case of handling several hundred W of passing power at a frequency of about 2 GHz to 3 GHz.

  8 and 9, the directional coupler is disposed on the main line 2 configured on the first dielectric substrate 1 and on the second dielectric substrate 3 disposed to face the main line 2. And a metal shield 5 configured to cover the second dielectric substrate 3 including the sub line 4. The main line 2 has a back surface covered with a conductor surface having a ground potential, and has a characteristic impedance of a line width of approximately 50Ω. The sub-line 4 is disposed on the second dielectric substrate 3 and has a configuration in which part of the sub-line 4 protrudes, and the protruding part has a gap so as not to overlap with the main line 2 in the vertical direction. It is arranged.

  The operation and action of the directional coupler configured as described above will be described below.

  When the high frequency power passes through the main line 2, an electric field and a magnetic field corresponding to the high frequency power are generated around it. The generated electric field and magnetic field are combined with the sub line 4 to generate signals at the A end and the B end of the sub line 4. The electromotive force generated in the convex portion of the sub-line 4 by the electric field is proportional to the electric field generated by the main line 2, and the electromotive force generated by this electric field is the same as that in the above-described embodiment in terms of an equivalent circuit. A voltage is generated at the A and B ends of the sub line 4. If these voltages are VA1 and VB1, respectively, the relationship of VA1 = VB1 is established.

Next, since a current due to the magnetic field is generated between A and B by the magnetic field interlinking the convex portions, when a predetermined impedance is connected to the A and B ends, the voltage is observed at the A and B ends. Can do. The equivalent circuit at this time is similarly as shown in FIG. 4 as in the above-described embodiment. If the voltages at this time are VA2 and VB2, the relationship of VA2 = −VB2 is established. By superimposing the above relations, when VA1 and VA2 are in the direction of adding, VB1 and VB2 are in the direction of subtraction, so the shape of the convex portion and the first dielectric substrate 1 so that VB1 = −VB2. By arranging the distance between the second dielectric substrate 3 and the second dielectric substrate 3 in the best state, it is possible to form a directional coupler that outputs a signal to one of the sub-lines 4 and outputs no signal to the other.

  Further, by changing the horizontal distance H1 between the main line 2 and the sub line 4, the degree of coupling and the directionality can be adjusted, and a directional coupler having arbitrary characteristics can be easily formed.

  Moreover, in the directional coupler of this structure, since it has the structure which can add the subline 4 which detects the electric power which transmits the main line 2 to the main line 2 which transmits electric power later, it transmits by the subline 4. The second dielectric substrate 3 including the sub line 4 can be disposed at an arbitrary position of the main line 2 having a length sufficient to detect electric power, and the installation position of the directional coupler can be set at an arbitrary position. The degree of freedom of mounting the board can be improved.

  As described above, since the directional coupler according to the present invention is small and can handle large passing electric power, a heating device, a garbage disposal machine, or a semiconductor using dielectric heating as represented by a microwave oven is used. The present invention can also be applied to a power detector of a power amplifier used for applications such as a microwave power source of a plasma power source as a manufacturing apparatus.

The top view of the directional coupler of the 1st Embodiment of this invention (A) Cross-sectional view taken along line A1-A2 of the directional coupler (b) Cross-sectional view taken along line B1-B2 of the directional coupler Equivalent circuit diagram of electric field coupling of the directional coupler Equivalent circuit diagram of magnetic coupling of directional coupler Characteristic diagram showing the measured characteristics of the directional coupler Characteristic diagram showing changes in distance between dielectric substrates and characteristic impedance of main line Characteristic diagram showing the measured characteristics of the directional coupler when the distance between the patterns of the parallel part of the convex part is changed The top view of the directional coupler of the 2nd Embodiment of this invention (A) Cross-sectional view taken along line A1-A2 of the directional coupler, (b) Cross-sectional view taken along line B1-B2 of the directional coupler. Plan view of conventional directional coupler using microstrip line

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st dielectric substrate 2 Main line 3 2nd dielectric substrate 4 Subline 5 Metal shield

Claims (8)

A main line made of a microstrip line formed on a first dielectric substrate, and a sub-line made of a microstrip line formed on a second dielectric substrate arranged on the main line with a gap. A directional coupler provided with a convex portion on the sub-line. The directional coupler according to claim 1, wherein a part of the convex portion provided on the sub line has an overlapping portion in a vertical direction of the main line and the substrate. The directional coupler according to claim 1, wherein the convex portion provided on the sub-line has a configuration in which there is no overlapping portion in a direction perpendicular to the main line and the substrate. The directional coupler according to any one of claims 1 to 3, wherein a gap between the sub line and the main line is 2 mm or more. The directional coupler according to claim 4, wherein the convex portion is configured to be 5 mm or more and 8 mm or less. The directional coupler according to claim 5, wherein a distance between patterns of the convex portions is set to 0.5 mm or less. The directional coupler according to any one of claims 1 to 4, wherein a metal shield member is provided around the second dielectric substrate. The directional coupler according to claim 7, wherein the second dielectric substrate is held by a metal shield member to secure a distance from the first dielectric substrate.