JP2017135465A - Single-ended microstrip line, differential microstrip line, and balanced unbalanced conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a single-ended microstrip line and a differential microstrip line having a smaller transmission loss than before while easily reducing the manufacturing cost as compared with the prior art.SOLUTION: In a single-ended microstrip line 1, a bridge conductor 14 connected to a first ground pad 13a and a second ground pad 13b is formed on a surface of a dielectric substrate 11, and the bridge conductor 14 is short-circuited to a ground conductor 15 through a through-via 11a.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a single-ended microstrip line that performs unbalanced transmission of a single-ended signal and a differential microstrip line that performs balanced transmission of a differential signal. The present invention also relates to a balance-unbalance conversion element including these microstrip lines.

  In order to increase the capacity of wireless communication, the frequency band to be used has been widened and increased in frequency. In recent years, not only the microwave band (0.3 GHz or more and 30 GHz or less) but also the millimeter wave band (30 GHz or more and 300 GHz or less) has been used for wireless communication. In order to transmit such high-frequency signals with low loss, (1) a dielectric substrate, (2) one or two strip conductors formed on the surface of the dielectric substrate, and (3) the dielectric substrate A microstrip line having a grounding conductor formed on the back surface of the substrate is widely used.

  A microstrip line with one strip conductor is used for unbalanced transmission of a single-ended signal. In the present specification, this is called a “single-end type microstrip line”. On the other hand, a microstrip line with two strip conductors is used for balanced transmission of differential signals. In the present specification, this is called a “differential microstrip line”.

  For connection between the single-ended microstrip line and the differential microstrip line, a balance-unbalance conversion element is used. The balance-unbalance conversion element includes (1) a dielectric substrate, (2) a first strip conductor formed on the surface of the dielectric substrate, and (2-1) a first strip conductor functioning as a single-ended microstrip line, (2 -2) Second and third strip conductors functioning as differential microstrip lines; (2-3) A distributor interposed between the first strip conductor and the second and third strip conductors; 3) It is constituted by a ground conductor formed on the back surface of the dielectric substrate. As the distributor, a Wilkinson type, distributed coupling type, branch line type, rat race type, or the like is used.

  In Patent Document 1, a part of a ring line constituting a rat race type distributor is a distributed coupled line comprising a conductor line formed on the surface of a dielectric substrate and a conductor line formed on the inner layer of the dielectric substrate. A balanced / unbalanced conversion element in which the electrical length of the ring line is shortened is disclosed.

JP 2014-216914 A (publication date: November 17, 2014)

  By the way, an electrode pad formed on the surface of a dielectric substrate constituting the microstrip line is used to connect the microstrip line and the IC. A typical electrode pad configuration in the conventional single-ended microstrip line 5 is shown in FIG. 12A, and a typical electrode pad configuration in the conventional differential microstrip line 6 is shown in FIG. ).

  In the conventional single-ended microstrip line 5, the end 52a of one strip conductor 52 formed on the surface of the dielectric substrate 51 is used as a signal pad (electrode pad for connecting an IC signal terminal). . Also, a conductor piece facing the first side 52b1 of the strip conductor 52 in the vicinity of the end 52a of the strip conductor 52 is used as a first ground pad (electrode pad for connecting the ground terminal of the IC) 53a. Further, a conductor piece facing the second side 52b2 of the strip conductor 52 in the vicinity of the end 52a of the strip conductor 52 is used as the second ground pad 53b. These two ground pads 53 a to 53 b are short-circuited to a ground conductor (not shown) formed on the back surface of the dielectric substrate 51 by through vias 51 a to 51 b penetrating the dielectric substrate 51, respectively. This is for maintaining the potentials of these two ground pads 53a to 53b at the ground potential. In the single-ended microstrip line constituting the balun, the same connection structure is employed at the end opposite to the distributor side.

  In the conventional differential microstrip line 6, the end portions 621 a and 622 a of the two strip conductors 621 and 622 formed on the surface of the dielectric substrate 61 are used as signal pads. Further, a conductor piece facing the second side 621b2 of the strip conductor 621 in the vicinity of the end 621a of the strip conductor 621 is used as the first ground pad 63a. Further, a conductor piece facing the second side 622b2 of the strip conductor 622 in the vicinity of the end 622a of the strip conductor 622 is used as the second ground pad 63b. Further, a conductor piece sandwiched between the end portion 621a of the strip conductor 621 and the end portion 622a of the strip conductor 622 and facing the first side 621b1 of the strip conductor 621 and the first side 622b1 of the strip conductor 622 Used as 3 ground pads 63c. These three ground pads 63a to 63c are short-circuited to ground conductors (not shown) formed on the back surface of the dielectric substrate 61 by through vias 61a to 61c penetrating the dielectric substrate 61, respectively. This is for maintaining these three ground pads 63a to 63c at the ground potential. In the differential microstrip line constituting the balance-unbalance conversion element, the same connection structure is adopted at the end opposite to the distributor side.

  When the connection structure shown in FIG. 12A is adopted in the single-ended microstrip line 5, it is necessary to form at least two through vias 51a to 51b in the dielectric substrate 51, which is a manufacturing cost. It was a factor that hindered the reduction. In order to form the through vias 51a to 51b, costly processes such as a process of drilling a through hole in the dielectric substrate 51 and a process of forming a metal thin film on the wall of the through hole by sputtering and / or plating are performed. This is because it is necessary to implement. Further, the connection structure shown in FIG. 12A leaves room for optimization in order to minimize transmission loss.

  Even in the case of adopting the connection structure shown in FIG. 12B in the differential microstrip line 6, it is necessary to form at least three through vias 61a to 61c in the dielectric substrate 61, which is a manufacturing cost. It was a factor that hindered the reduction. Also, the connection structure shown in FIG. 12B leaves room for optimization in order to minimize transmission loss.

  A similar problem may exist in the balanced / unbalanced conversion element including the single-ended microstrip line shown in FIG. 12A and the differential microstrip line shown in FIG. It will be clear.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a single-ended type microstrip line having a transmission loss smaller than that of the conventional one and a difference in the manufacturing cost while being easier to reduce the manufacturing cost than the conventional one. This is to realize a dynamic microstrip line. Another object of the present invention is to realize a balanced / unbalanced conversion element having a conversion loss smaller than that of the prior art, although the manufacturing cost can be easily reduced as compared with the prior art.

  In order to solve the above-described problems, a single-ended microstrip line according to the present invention includes a dielectric substrate, (1) a strip conductor formed on the surface of the dielectric substrate, and (2) an end of the strip conductor. A first ground pad that opposes the first side of the strip conductor in the vicinity of the portion; and (3) a second ground pad that opposes the second side of the strip conductor in the vicinity of the end of the strip conductor; A ground conductor formed on the back surface of the dielectric substrate, and a bridge conductor connected to the first ground pad and the second ground pad is formed on the front surface of the dielectric substrate. The bridge conductor is short-circuited to the ground conductor through a through via.

  According to the above configuration, since the first ground pad and the second ground pad are short-circuited by the bridge conductor, the first ground pad and the second ground pad can be short-circuited to the ground conductor by one through via. It is. For this reason, the manufacturing cost is lower than that of a conventional single-ended microstrip line (see FIG. 12A) that requires two or more through vias to short-circuit the first ground pad and the second ground pad with the ground conductor. Can be kept low. Further, according to numerical experiments conducted by the inventors, it is possible to reduce transmission loss as compared with a conventional single-ended microstrip line.

  In the single-ended microstrip line according to the present invention, the bridge conductor is connected to the ground conductor through one through via, and a short circuit that short-circuits the first ground pad and the ground conductor; The short circuit that short-circuits the second ground pad and the ground conductor is preferably only the short circuit including the one through via.

  According to said structure, the single end microstrip line | wire which suppressed the manufacturing cost lower than before can be implement | achieved.

  In order to solve the above problems, a differential microstrip line according to the present invention comprises (1) a first strip conductor and a second strip conductor formed on a dielectric substrate and the surface of the dielectric substrate. A pair of strip conductors, wherein the first side edges of the first strip conductor and the second strip conductor are opposed to each other in the vicinity of the end portions of the first strip conductor and the second strip conductor; (2) A first ground pad facing the second side of the first strip conductor in the vicinity of the end of the first strip conductor; and (3) a second ground conductor of the second strip conductor in the vicinity of the end of the second strip conductor. A second ground pad facing two side edges; and (4) the first strip conductor and the end portion of the second strip conductor in the vicinity of the end portion. A third ground pad facing the first side of the first strip conductor and the second strip conductor, and a ground conductor formed on the back surface of the dielectric substrate, and the surface of the dielectric substrate. Are formed with a bridge conductor connected to the first ground pad, the second ground pad, and the third ground pad, and the bridge conductor is connected to the first via the through via that penetrates the dielectric substrate. It is short-circuited to the ground conductor.

  According to the above configuration, since the first ground pad, the second ground pad, and the third ground pad are short-circuited by the bridge conductor, two first ground pads, second ground pads, and third ground pads are provided. It is possible to short-circuit with the ground conductor by the following through via. Therefore, a conventional differential microstrip line that requires three or more through vias to short-circuit the first ground pad, the second ground pad, and the third ground pad with the ground conductor (see FIG. 12B). Compared with, it is possible to keep the manufacturing cost low. Further, according to numerical experiments conducted by the inventors, it is possible to suppress transmission loss as compared with a conventional differential microstrip line.

  In the differential microstrip line according to the present invention, the bridge conductor is connected to the ground conductor through two or less through vias, and a short circuit that short-circuits the first ground pad and the ground conductor, The short circuit that short-circuits the second ground pad and the ground conductor and the short circuit that short-circuits the third ground pad and the ground conductor are preferably only short circuits including the two or less through vias. .

  According to said structure, the single end microstrip line | wire which suppressed the manufacturing cost lower than before can be implement | achieved.

  In order to solve the above-described problems, a balanced-unbalanced conversion element according to the present invention is connected to the single-ended microstrip line via the single-ended microstrip line, the distributor, and the distributor. In addition, the above-described differential microstrip line is provided.

  According to said structure, compared with the conventional balance-unbalance conversion element, it is possible to hold down manufacturing cost low. Further, according to a numerical experiment conducted by the inventors, it is possible to suppress the conversion loss to be smaller than that of a conventional balanced / unbalanced converting element.

  In the balanced-unbalanced conversion element according to the present invention, the distributor is connected to the strip of the single-ended microstrip line at a first connection point, and the first of the differential microstrip line at a second connection point. A ring line connected to the first strip conductor and connected to the second strip conductor of the differential microstrip line at a third connection point; and in the distributor, from the second connection point to the first connection point. The electrical length L21 of the path to the connection point and the electrical length L31 of the path from the third connection point to the first connection point are the absolute values of the differences, where λ is the wavelength of the signal to be balanced / unbalanced. | L31−L21 | is set to coincide with λ / 2 + nλ (where n is an arbitrary integer equal to or greater than 0), and the differential microstrip line includes Te, by providing the folded portion to the second strip conductor, to match the length of the length of the first strip conductor and the second strip conductor, it is preferable.

  According to said structure, the area | region required for arrangement | positioning of a 1st strip conductor and a 2nd strip conductor is expanded easily for the conversion from a single end signal to a differential signal, and the conversion from a differential signal to a single end signal. Without having to do so.

  In the balanced / unbalanced conversion element according to the present invention, the distributor includes (1) a first straight line portion including the first connection point, and (2) a terminal point of the first straight line portion as a start point. A second straight portion extending in a direction orthogonal to the extending direction of the straight portion, the second straight portion including the second connection point, and (3) a terminal point of the second straight portion as a start point, A third straight line portion extending in a direction opposite to the extending direction of the one straight line portion, the third straight line portion including the third connection point, and (4) a termination point of the third straight line portion as a start point, It is preferable that a ring line including a fourth linear portion extending in a direction opposite to the extending direction of the second linear portion is provided.

  According to the above configuration, conversion from a single-end signal to a differential signal and conversion from a differential signal to a single-end signal can be realized with a simple configuration.

  In the unbalanced / balanced conversion element according to the present invention, the distributor includes a first stub projecting from the second straight line portion toward the inside of the ring line, and a fourth straight line portion toward the inside of the ring line. And a second stub projecting out.

  According to the above configuration, the conversion loss can be further reduced.

  According to the present invention, it is possible to realize a single-ended microstrip line and a differential microstrip line that are easier to reduce the manufacturing cost than the conventional one and have a smaller transmission loss than the conventional one. Further, according to the present invention, it is possible to realize a balanced / unbalanced conversion element having a conversion loss smaller than that of the prior art, while it is easier to reduce the manufacturing cost than the conventional one.

(A) is a top view of the single end type microstrip line concerning one embodiment of the present invention. FIG. 2B is a sectional view of the single-ended microstrip line. FIG. 3A is a plan view of a differential microstrip line according to an embodiment of the present invention. (B) is sectional drawing of the differential type microstrip line. FIG. 3 is a plan view of a balanced / unbalanced conversion element including the single-ended microstrip line shown in FIG. 1 and the differential microstrip line shown in FIG. 2. (A) is an enlarged plan view of the balance-unbalance conversion element shown in FIG. 3, (b) is an enlarged plan view of the balance-unbalance conversion element according to the first comparative example, and (c) is It is an enlarged plan view of the balance-unbalance conversion element according to the second comparative example. It is a graph which shows the frequency dependence of the conversion loss of each balance-unbalance conversion element shown in FIG. (A) is an enlarged plan view of the balance-unbalance conversion element shown in FIG. 3, and (b) is an enlarged plan view of the balance-unbalance conversion element according to the first modification. It is a graph which shows the frequency dependence of the conversion loss of each balance-unbalance conversion element shown in FIG. (A) is an enlarged plan view of the balance-unbalance conversion element shown in FIG. 3, and (b) is an enlarged plan view of the balance-unbalance conversion element according to the second modification. It is a graph which shows the frequency dependence of the conversion loss of each balance-unbalance conversion element shown in FIG. (A) is an enlarged plan view of the balance-unbalance conversion element shown in FIG. 3, and (b) is an enlarged plan view of the balance-unbalance conversion element according to the third modification. It is a graph which shows the frequency dependence of the conversion loss of each balance-unbalance conversion element shown in FIG. (A) is a plan view of a conventional single-ended microstrip line, and (b) is a plan view of a conventional differential microstrip line.

[Configuration of single-ended microstrip line]
A single-ended microstrip line 1 according to an embodiment of the present invention will be described with reference to FIG. 1A is a plan view of a single-ended microstrip line 1 and FIG. 1B is a cross-sectional view (AA ′ cross-section) of the single-ended microstrip line 1.

  As shown in FIG. 1, the single-ended microstrip line 1 includes a dielectric substrate 11, a strip conductor 12, a first ground pad 13 a, a second ground pad 13 b, a bridge conductor 14, and a ground conductor 15. The strip conductor 12, the first ground pad 13a, the second ground pad 13b, and the bridge conductor 14 are formed on the surface of the dielectric substrate 11, and the ground conductor 15 is formed on the back surface of the dielectric substrate 11. . The names “front surface” and “back surface” are merely convenient names for distinguishing the two main surfaces of the dielectric substrate 11, and regarding the arrangement method and mounting method of the single-ended microstrip line 1, There are no restrictions.

  The dielectric substrate 11 is a plate-like member whose front and back surfaces are rectangular and is made of a dielectric material. In this embodiment, a liquid crystal polymer substrate (dielectric constant 2.9, dielectric loss tangent 0.003) having a thickness of 50 μm is used as the dielectric substrate 11.

  The strip conductor 12 is a linear or strip-like conductor pattern, and is arranged in parallel with the long side of the surface of the dielectric substrate 11. The end 12a of the strip conductor 12 functions as an electrode pad for connecting a signal terminal of the IC.

  The first ground pad 13a is an electrode pad for connecting the ground terminal of the IC. The first ground pad 13 a is disposed in the vicinity of the end 12 a of the strip conductor 12 so as to face the first side 12 b 1 of the strip conductor 12. In the present embodiment, a rectangular conductor piece arranged so that the long side faces the first side 12b1 of the strip conductor 12 is used as the first ground pad 13a.

  Similar to the first ground pad 13a, the second ground pad 13b is an electrode pad for connecting the ground terminal of the IC. The second ground pad 13 b is disposed in the vicinity of the end 12 a of the strip conductor 12 so as to face the second side 12 b 2 of the strip conductor 12. In the present embodiment, a rectangular conductor piece arranged so that the long side faces the second side 12b2 of the strip conductor 12 is used as the second ground pad 13b.

  The bridge conductor 14 is a conductor for short-circuiting (directly conducting) the first ground pad 13a and the second ground pad 13b. In the present embodiment, the long side faces the end side 12c of the strip conductor 12, and the short side of the first ground pad 13a and the short side of the second ground pad 13b are respectively provided at both ends of the long side. The connected rectangular conductor piece is used as the bridge conductor 14. In the present embodiment, the bridge conductor 14 is integrally formed as one conductor pattern together with the first ground pad 13a and the second ground pad 13b.

  The ground conductor 15 is a planar conductor that covers at least a region facing the strip conductor 12 and a region facing the bridge conductor 14 on the back surface of the dielectric substrate 11. In the present embodiment, a planar conductor that covers the entire back surface of the dielectric substrate 11 is used as the ground conductor 15.

  As described above, in the single-ended microstrip line 1 according to the present embodiment, a configuration in which the first ground pad 13a and the second ground pad 13b are short-circuited via the bridge conductor 14 is employed. Therefore, both the first ground pad 13a and the second ground pad 13b can be kept at the same potential as the ground conductor 15 only by short-circuiting the bridge conductor 14 and the ground conductor 15 through one through via. For this reason, in order to keep both the first ground pad 53a and the second ground pad 53b at the same potential as the ground conductor, the conventional single-ended microstrip line 5 that requires two or more through vias 51a to 51b (see FIG. 12). Compared to (a), the manufacturing cost can be kept low.

  Actually, in the single-ended microstrip line 1 shown in FIG. 1, one through via 11a is provided in a region sandwiched between the bridge conductor 14 and the ground conductor 15 in the dielectric substrate 11, and the bridge conductor 14 is connected to the through via 11a. The ground conductor 15 is short-circuited. Therefore, the single-ended microstrip line 1 shown in FIG. 1 can be manufactured at a lower cost than the conventional single-ended microstrip line 5 shown in FIG. For example, as shown in FIG. 1B, the through via 11a is formed by forming a conductive thin film such as a metal thin film on the hole wall of the through hole penetrating the dielectric substrate 11 using a sputtering method and / or a plating method. It can be formed by forming a film. You may form by filling conductors, such as a metal, in the hole of the through-hole which penetrates the dielectric substrate 11. FIG.

  Although the number of through vias is preferably one from the viewpoint of keeping the manufacturing cost lower than before, the present invention is not limited to this. That is, when the number of through vias is two or more, the above-described effect of suppressing the manufacturing cost as compared with the conventional one cannot be obtained, but the effect described later of suppressing the transmission loss can be obtained.

[Configuration of differential microstrip line]
A differential microstrip line 2 according to an embodiment of the present invention will be described with reference to FIG. 2A is a plan view of the differential microstrip line 2, and FIG. 2B is a cross-sectional view of the differential microstrip line 2.

  As shown in FIG. 2, the differential microstrip line 2 includes a dielectric substrate 21, a strip conductor pair 22, a first ground pad 23a, a second ground pad 23b, a third ground pad 23c, a bridge conductor 24, and a ground. A conductor 25 is provided. The strip conductor pair 22, the first ground pad 23a, the second ground pad 23b, the third ground pad 23c, and the bridge conductor 24 are formed on the surface of the dielectric substrate 21, and the ground conductor 25 is the dielectric substrate 21. It is formed on the back surface. Note that the names “front surface” and “back surface” are merely convenient names for distinguishing the two main surfaces of the dielectric substrate 21, and regarding the arrangement method and mounting method of the differential microstrip line 2, There are no restrictions.

  The dielectric substrate 21 is a plate-like member whose front and back surfaces are rectangular and is made of a dielectric material. In this embodiment, like the dielectric substrate 11, a liquid crystal polymer substrate (dielectric constant 2.9, dielectric loss tangent 0.003) having a thickness of 50 μm is used as the dielectric substrate 21.

  The strip conductor pair 22 includes a first strip conductor 221 and a second strip conductor 222 that form a pair. The first strip conductor 221 and the second strip conductor 222 are each a linear or strip-shaped conductor pattern. The first strip conductor 221 and the second strip conductor 222 are arranged so as to be parallel to the long side of the surface of the dielectric substrate 21, and the first side 221 b 1 of the first strip conductor 221 and the second strip conductor 222. The first side 222b1 faces each other. The end portion 221a of the first strip conductor 221 and the end portion 222a of the second strip conductor 222 each function as an electrode pad for connecting a signal terminal of the IC. When the first strip conductor 221 and the second strip conductor 222 are divided into a first section I1 functioning as an electrode pad, a second section I2 adjacent to the first section I1, and a third section I3 adjacent to the second section I2, The distance between the first strip conductor 221 and the second strip conductor 222 is constant in the first section I1 (same as the distance between the IC signal terminals), and gradually decreases in the second section I2 as the distance from the first section I1 increases. Thus, it is constant in the third section I3 (interval optimized to minimize transmission loss, which is narrower than the interval in the first section I1).

  The first ground pad 23a is an electrode pad for connecting an IC ground terminal. The first ground pad 23 a is disposed in the vicinity of the end 221 a of the first strip conductor 221 so as to face the second side 221 b 2 of the first strip conductor 221. In the present embodiment, a rectangular conductor piece arranged so that its long side faces the second side 221b2 of the first strip conductor 221 is used as the first ground pad 23a.

  Similar to the first ground pad 23a, the second ground pad 23b is an electrode pad for connecting the ground terminal of the IC. The second ground pad 23 b is disposed in the vicinity of the end 222 a of the second strip conductor 222 so as to face the second side 222 b 2 of the second strip conductor 222. In the present embodiment, a rectangular conductor piece arranged so that its long side faces the second side 222b2 of the second strip conductor 222 is used as the second ground pad 23b.

  The third ground pad 23c is an electrode pad for connecting the ground terminal of the IC, like the first ground pad 23a and the second ground pad 23b. The third ground pad 23 is located in the vicinity of the end 221 a of the first strip conductor 221 and the end 222 a of the second strip conductor 222, and the first side 221 b 1 of the first strip conductor 221 and the second strip conductor 222. It arrange | positions so that 1 side 222b1 may be opposed. In the present embodiment, one long side is arranged to face the first side 221b1 of the first strip conductor 221, and the other long side is arranged to face the first side 222b1 of the second strip conductor 222. A rectangular conductor piece is used as the third ground pad 23c.

  The bridge conductor 24 is a conductor for short-circuiting (directly conducting) the first ground pad 23a, the second ground pad 23b, and the third ground pad 23c. In the present embodiment, one long side opposes the end side 221c of the strip conductor 221 and the end side 222c of the strip conductor 222, and both ends of the long side are short sides of the first ground pad 23a. A rectangular conductor piece in which the short side of the third ground pad 23c is connected to the center of the long side is used as the bridge conductor 24. In the present embodiment, the bridge conductor 24 is integrally formed as one conductor pattern together with the first ground pad 23a, the second ground pad 23b, and the third ground pad 23c.

  The ground conductor 25 is a planar conductor that covers at least a region facing the strip conductor pair 22 and a region facing the bridge conductor 24 on the back surface of the dielectric substrate 21. In the present embodiment, a planar conductor that covers the entire back surface of the dielectric substrate 21 is used as the ground conductor 25.

  As described above, in the differential microstrip line 2 according to the present embodiment, the first ground pad 23a, the second ground pad 23b, and the third ground pad 23c are short-circuited via the bridge conductor 24. It has been adopted. Therefore, the first ground pad 23a, the second ground pad 23b, and the third ground pad 23c are connected to the ground conductor 25 only by short-circuiting the bridge conductor 24 and the ground conductor 25 through one or two through vias. The same potential can be maintained. Therefore, in order to keep the first ground pad 63a, the second ground pad 63b, and the third ground pad 63c at the same potential as the ground conductor, a conventional differential microstrip line that requires three or more through vias 61a to 61c. Compared to 6 (see FIG. 12B), the manufacturing cost can be kept low.

  Actually, in the differential microstrip line 2 shown in FIG. 2, one through via 21a is provided in a region sandwiched between the bridge conductor 24 and the ground conductor 25 in the dielectric substrate 21, and the bridge is formed by the one through via 21a. The conductor 24 and the ground conductor 25 are short-circuited. Therefore, the manufacturing cost of the differential microstrip line 2 can be manufactured at a lower cost than the conventional differential microstrip line 6 shown in FIG. The through via 21a is formed in the same manner as the through via 11a in the single-ended microstrip line 1 shown in FIG.

  Although the number of through vias is preferably one or two from the viewpoint of keeping the manufacturing cost lower than before, the present invention is not limited to this. That is, when the number of through vias is three or more, the above-described effect of reducing the manufacturing cost as compared with the conventional case cannot be obtained, but the effect described later of suppressing the transmission loss can be obtained.

[Configuration of balanced / unbalanced conversion element]
A balanced-unbalanced conversion element 3 according to an embodiment of the present invention will be described with reference to FIG. FIG. 3 is a plan view of the balance-unbalance conversion element 3.

  The balance-unbalance conversion element 3 is obtained by connecting a single-ended microstrip line 1 and a differential microstrip line 2 having three through vias via a distributor 33. In the balance-unbalance conversion element 3, a common dielectric substrate 31 is used as the dielectric substrate 11 constituting the single-ended microstrip line 1 and the dielectric substrate 21 constituting the differential microstrip line 2. . A common ground conductor (not shown) is used as the ground conductor 15 constituting the single-ended microstrip line 1 and the ground conductor 25 constituting the differential microstrip line 2.

  The differential microstrip line 2 employs a configuration in which the electrical length of the first strip conductor 221 and the electrical length of the second strip conductor 222 are matched. This is because the differential signal input to the differential microstrip line 2 is input to the distributor 33 while maintaining the phase difference between the positive phase signal and the negative phase signal. Further, the differential microstrip line 2 employs a configuration in which the second strip conductor 222 is provided with a folded portion 222d. This is because the electrical length of the first strip conductor 221 and the electrical length of the second strip conductor 222 are made to coincide with each other without expanding the area required for the arrangement of the second strip conductor 222.

  The distributor 33 is configured by a conductor pattern formed on the surface of the dielectric substrate 11 as well as the ground conductor 15 constituting the single-ended microstrip line 1 and the ground conductor 25 constituting the differential microstrip line 2. ing. In the present embodiment, a rat race type distributor including a ring line 33 a is used as the distributor 33.

  The ring line 33a includes four linear portions 33a1 to 33a4 formed on the upper surface of the dielectric substrate 31. The first straight portion 33a1 is a linear or strip-shaped conductor pattern, and is connected to the strip conductor 12 of the single-ended microstrip line 1 at a connection point P1 provided in the middle thereof. The second straight portion 33a2 is a linear or strip-like conductor pattern that starts from the end point of the first straight portion 33a1 and extends in a direction orthogonal to the extending direction of the first straight portion 33a1, and is provided in the middle thereof. The connection point P2 is connected to the first strip conductor 221 of the differential microstrip line 2. The third straight portion 33a3 is a linear or strip-like conductor pattern that starts from the end point of the second straight portion 33a2 and extends in a direction opposite to the extending direction of the first straight portion 33a1, and is provided in the middle thereof. The connection point P3 is connected to the second strip conductor 222 of the differential microstrip line 2. The fourth straight line portion 33a4 is a linear shape extending from the end point of the third straight line portion 33a3 as a start point and starting from the start point of the first straight line portion 33a1 and extending in a direction opposite to the extending direction of the second straight line portion 33a2. It is a strip-shaped conductor pattern.

  In the ring line 33a, the electrical length L21 of the path from the connection point P2 to the connection point P1 and the electrical length L31 of the path from the connection point P3 to the connection point P1 are the wavelength λ of the signal to be balanced / unbalanced conversion. The absolute value | L31−L21 | of the difference is set to coincide with λ / 2 + nλ (n is an arbitrary integer equal to or greater than 0). In particular, in the present embodiment, the difference L31-L21 is set to coincide with λ / 2. As a result, signals having opposite phases input from the connection point P2 and the connection point P3 are output from the connection point P1 as signals having the same phase (conversion from a differential signal to a single-ended signal). Conversely, a signal input from the connection point P1 is output from the connection point P2 and the connection point P3 as a signal having an opposite phase (conversion from a single end signal to a differential signal).

  In the ring line 33a, the electrical length L213 = L21 + L31 of the path from the connection point P2 to the connection point P3 via the connection point P1, and the electrical path of the path from the connection point P2 to the connection point P3 without passing through the connection point P1. The length L23 is set so that the wavelength of the signal to be balanced / unbalanced conversion is λ, and the absolute value | L213−L23 | of the difference coincides with λ / 2 + nλ (n is an arbitrary integer of 0 or more). Is done. In particular, in the present embodiment, the difference L213-L23 is set to coincide with λ / 2. Thereby, it is possible to avoid the problem that the signal input from the connection point P2 is output from the connection point P3 and the problem that the signal input from the connection point P3 is output from the connection point P2. . The former problem can be avoided when a signal is input from the connection point P2 and a signal component that reaches the connection point P3 via the connection point P1 and a signal component that reaches the connection point P3 without passing through the connection point P1. This is because they are opposite to each other and cancel each other. Further, the latter problem can be avoided when a signal is input from the connection point P3 and reaches the connection point P2 without passing through the connection point P1 via the connection point P1 and the signal component reaching the connection point P2. This is because the signal components have opposite phases and cancel each other.

  The distributor 33 further includes a first stub 33b and a second stub 33c. The first stub 33b is a strip-like conductor protruding from the second straight portion 33a2 toward the inside of the ring line 33a, and the second stub 33c is a strip-like shape protruding from the fourth straight portion 33a4 toward the inside of the ring line 33a. It is a conductor. The first stub 33 b and the second stub 33 c generate a reflected wave that cancels the reflected wave generated in the distributor 33.

  As described above, the balanced / unbalanced conversion element 3 according to the present embodiment uses the single-ended microstrip line 1 shown in FIG. 1 and the differential microstrip line 2 shown in FIG. Compared with the conventional balance-unbalance conversion element, the manufacturing cost can be kept low. Further, as will be described later, it is possible to suppress the conversion loss as compared with the conventional balance-unbalance conversion element.

[Effect of bridge conductor in single-ended microstrip line]
The effect of the bridge conductor 14 in the single-ended microstrip line 1 will be supplemented with reference to FIGS. 4 and 5.

  4A is an enlarged plan view of the balanced / unbalanced conversion element 3 (with a bridge conductor and with a through via) according to the present embodiment, and FIG. 4B is a balanced unbalanced according to the first comparative example. It is an enlarged plan view of a conversion element (with a bridge conductor and no through via), and (c) is an enlarged plan view of a balanced / unbalanced conversion element (without a bridge conductor and no through via) according to a second comparative example.

  Here, the balance-unbalance conversion element according to the first comparative example is the same as the balance-unbalance conversion element 3 according to this embodiment shown in FIG. The configuration shown in b) is changed, that is, the bridge conductor 14 and the through via 11a of the single-ended microstrip line 1 are omitted. Further, the single-ended microstrip line according to the second comparative example is different from the balanced-unbalanced conversion element 3 according to the present embodiment shown in FIG. The configuration shown in b) is changed, that is, the through via 11a of the single-ended microstrip line 1 is omitted.

  FIG. 5 shows a balance-unbalance conversion element 3 according to the present embodiment (see FIG. 4A), a balance-unbalance conversion element according to the first comparative example (see FIG. 4B), and It is a graph which shows the frequency dependence of conversion loss about the balance unbalance conversion element (refer (c) of Drawing 4) concerning the comparative example of 2. The conversion loss is an amount defined by | S12 × S13 + S21 × S31 | / 2√2, and is also referred to as a differential mode gain. Here, S12 is output from the distributor 33 to the strip conductor 12 of the single-ended microstrip line 1 among the signals input from the first strip conductor 221 of the differential microstrip line 2 to the distributor 33. This is an S parameter that represents the proportion of the component. S13 is a signal input from the second strip conductor 222 of the differential microstrip line 2 to the distributor 33, and the component output from the distributor 33 to the strip conductor 12 of the single-ended microstrip line 1 This is an S parameter representing the proportion of the occupancy. In S21, a component output from the distributor 33 to the first strip conductor 221 of the differential microstrip line 2 among the signals input to the distributor 33 from the strip conductor 12 of the single-ended microstrip line 1 This is an S parameter representing the proportion of the occupancy. S31 is a component of the signal output from the distributor 33 to the second strip conductor 222 of the differential microstrip line 2 among the signals input from the strip conductor 12 of the single-ended microstrip line 1 to the distributor 33. This is an S parameter indicating the ratio.

  From the graph of FIG. 5, the conversion loss of the balanced / unbalanced conversion element 3 according to this embodiment is the conversion loss of the balanced / unbalanced conversion element according to the first comparative example at all illustrated frequencies (50 GHz to 70 GHz). And it turns out that it is smaller than the conversion loss of the balance-unbalance conversion element which concerns on a 2nd comparative example. This is because the transmission loss of the single-ended microstrip line 1 including the bridge conductor 14 and the through via 11a is from the comparative example in which the through via 11a is omitted from the single-ended microstrip line 1 and the single-ended microstrip line 1. This means that the transmission loss is smaller than that of the comparative example in which the through via 11a and the bridge conductor 14 are omitted.

  Further, from the graph of FIG. 5, the conversion loss of the balanced / unbalanced conversion element according to the first comparative example is smaller than the conversion loss of the balanced / unbalanced conversion element according to the second comparative example at all illustrated frequencies. I understand that. This means that the effect of reducing the transmission loss is not an effect obtained only from the bridge conductor 14, but an effect obtained only by combining the bridge conductor 14 and the through via 11a.

[Number of through vias in single-ended microstrip lines]
The number of through vias in the single-ended microstrip line 1 will be described with reference to FIGS.

  6A is an enlarged plan view of the balanced / unbalanced conversion element 3 according to the present embodiment, and FIG. 6B is an enlarged sectional view of the balanced / unbalanced conversion element 3 according to the first modification. is there.

  Here, the balanced-unbalanced conversion element 3 according to the first modification is the same as the balanced-unbalanced conversion element 3 according to this embodiment shown in FIG. The configuration shown in (b) is changed, that is, the number of through vias is changed from one to two.

  FIG. 7 shows the balance-unbalance conversion element 3 (see FIG. 6A) according to the present embodiment and the balance-unbalance conversion element 3 according to the first modification (see FIG. 6B). It is a graph which shows the frequency dependence of conversion loss.

  As long as the graph shown in FIG. 7 is referred to, the conversion loss of the balanced / unbalanced conversion element 3 (one through via) according to the present embodiment and the conversion of the balanced / unbalanced conversion element 3 (two through vias) according to the first modified example. There is no significant difference between the loss. From this, it is understood that the transmission loss of the single-ended microstrip line 1 does not depend on the number of through vias. Therefore, in the single-ended microstrip line 1 according to the present embodiment, the number of through vias can be reduced without causing a significant increase in transmission loss.

[Number of through vias in differential microstrip line]
The number of through vias in the differential microstrip line 2 will be described with reference to FIGS.

  8A is an enlarged plan view of the balanced / unbalanced conversion element 3 according to the present embodiment, and FIG. 8B is an enlarged sectional view of the balanced / unbalanced conversion element 3 according to the second modification. is there.

  Here, the balanced / unbalanced conversion element 3 according to the second modification is the same as the balanced / unbalanced conversion element 3 according to the present embodiment shown in FIG. The configuration shown in (b) is changed, that is, the number of through vias is changed from three (through vias 21a to 21c) to six (through vias 21a to 21f).

  FIG. 9 shows the balance-unbalance conversion element 3 (see FIG. 8A) according to the present embodiment and the balance-unbalance conversion element 3 according to the second modification (see FIG. 8B). It is a graph which shows the frequency dependence of conversion loss.

  As long as the graph shown in FIG. 9 is referred to, the conversion loss of the balanced / unbalanced conversion element 3 (three through vias) according to the present embodiment and the conversion of the balanced / unbalanced conversion element 3 (six through vias) according to the second modification example There is no significant difference between the loss. From this, it is understood that the transmission loss of the differential microstrip line 2 does not depend on the number of through vias. Therefore, in the differential microstrip line 2 of the present embodiment, the number of through vias can be reduced without causing a significant increase in transmission loss.

[Bending of strip conductor in differential microstrip line]
The bending of the strip conductor 222 in the differential microstrip line 2 will be described with reference to FIGS.

  10A is an enlarged plan view of the balanced / unbalanced conversion element 3 according to the present embodiment, and FIG. 10B is an enlarged sectional view of the balanced / unbalanced conversion element 3 according to the third modification. is there.

  As shown in FIG. 8A, in the balanced / unbalanced conversion element 3 according to the present embodiment, the second strip conductor 222 of the differential microstrip line 2 is provided with a folded portion 222d, whereby the second strip. A configuration is adopted in which the electrical length of the conductor 222 matches the electrical length of the first strip conductor 221 of the differential microstrip line 2. On the other hand, as shown in FIG. 8B, in the balanced / unbalanced conversion element 3 according to the third modification, the electric length of the second strip conductor 222 is changed to the differential type by omitting the folded portion 222d. A configuration is adopted in which the electrical length of the first strip conductor 221 of the microstrip line 2 is made shorter.

  FIG. 11 shows the balance-unbalance conversion element 3 (see FIG. 10A) according to the present embodiment and the balance-unbalance conversion element 3 according to the third modification (see FIG. 10B). The end portions of the first strip conductor 221 and the second strip conductor 222 constituting the differential microstrip line 2 when a signal is inputted to the end portion 12a of the strip conductor 12 constituting the single-end type microstrip line 1. It is a graph which shows the frequency dependence of the phase difference of the signal output from 221a, 222a.

  From the graph shown in FIG. 11, in the balanced / unbalanced conversion element 3 according to the present embodiment, the above phase difference falls within the range of 180 ° ± 10 ° in the illustrated band (from 50 GHz to 70 GHz). In the balanced / unbalanced conversion element 3 according to the third modification, it can be seen that the above phase difference does not fall within the range of 180 ° ± 10 ° in the illustrated band. That is, in the balanced / unbalanced conversion element 3 according to the present embodiment, a single-ended signal can be correctly converted into a differential signal, whereas in the balanced / unbalanced conversion element 3 according to the third modification, It can be seen that the single-ended signal cannot be correctly converted into the differential signal.

  In the differential microstrip line 2, it is preferable to adopt a configuration in which the electrical length of the first strip conductor 221 and the electrical length of the second strip conductor 222 are the same in the distributor 33. This is a case where a configuration is adopted in which the difference between the electrical length of the path from the conductor connection point P1 to the electrical length of the path from the conductor connection point P3 to the connection point P1 is λ / 2 + nλ (see FIG. 3). This is because in this case, the difference between the electrical length of the path from the end 221a of the first strip conductor 221 to the connection point P1 and the electrical length of the path from the end 222a of the second strip conductor 222 to the connection point P1 is λ. This is because / 2 + nλ, and the input signal from the connection point P1 is correctly reversed in phase at the end 221a of the first strip conductor 221 and the end 222a of the second strip conductor 222. That is, the electrical lengths of the first strip conductor 221 and the second strip conductor 222 are the electrical length of the path from the end 221a of the first strip conductor 221 to the connection point P1, and the connection point from the end 222a of the second strip conductor 222. What is necessary is just to determine so that the difference with the electrical length of the path | route which reaches to P1 may be set to (lambda) / 2 + n (lambda).

[Additional Notes]
The present invention is not limited to the above-described embodiments (examples), and various modifications are possible within the scope shown in the claims, and technical means disclosed in different embodiments are appropriately combined. The obtained embodiment is also included in the technical scope of the present invention.

  The present invention can be suitably used in a technical field in which a single-ended microstrip line that performs unbalanced transmission of a single-ended signal and a differential microstrip line that performs balanced transmission of a differential signal are used.

1, 5 Single-ended microstrip line 2, 6 Differential microstrip line 3 Balance-unbalance conversion element 11, 21, 31 Dielectric substrate 11a, 21a, 51a, 61a Through via 12, 221, 222 Strip conductor 13a, 23a , 53a, 63a First ground pad 13b, 23b, 53b, 63b Second ground pad 14, 24 Bridge conductor 15, 25 Ground conductor 22 Strip conductor pair 23, 23c, 63c Third ground pad 33 Distributor 33a Ring line 33b First 1 stub 33c 2nd stub 221 1st strip conductor 222 2nd strip conductor

Claims (8)

Dielectric substrate,
(1) a strip conductor formed on the surface of the dielectric substrate; (2) a first ground pad facing the first side of the strip conductor in the vicinity of an end of the strip conductor; and (3) the above A second ground pad facing the second side of the strip conductor in the vicinity of the end of the strip conductor; and
A ground conductor formed on the back surface of the dielectric substrate,
A bridge conductor connected to the first ground pad and the second ground pad is formed on the surface of the dielectric substrate, and the bridge conductor is short-circuited to the ground conductor via a through via. ,
A single-ended microstrip line characterized by that. The bridge conductor is connected to the ground conductor through one through via,
The short circuit that short-circuits the first ground pad and the ground conductor and the short circuit that short-circuits the second ground pad and the ground conductor are only short circuits including the one through via.
The single-ended microstrip line according to claim 1. Dielectric substrate,
(1) A strip conductor pair formed on the surface of the dielectric substrate, the strip conductor pair including a first strip conductor and a second strip conductor, in the vicinity of the end portions of the first strip conductor and the second strip conductor. A pair of strip conductors in which the first side of the first strip conductor and the second strip conductor face each other; and (2) a second side of the first strip conductor that opposes the second side in the vicinity of the end of the first strip conductor. 1 ground pad, (3) a second ground pad facing the second side of the second strip conductor in the vicinity of the end of the second strip conductor, and (4) the first strip conductor and the second In the vicinity of the end of the strip conductor, a third ground pad facing the first side of the first strip conductor and the second strip conductor. , As well as,
A ground conductor formed on the back surface of the dielectric substrate,
A bridge conductor connected to the first ground pad, the second ground pad, and the third ground pad is formed on the surface of the dielectric substrate, and the bridge conductor is connected to the dielectric substrate. Shorted to the ground conductor through a through via that penetrates,
A differential microstrip line characterized by that. The bridge conductor is connected to the ground conductor through two or less through vias,
The short circuit that short-circuits the first ground pad and the ground conductor, the short circuit that short-circuits the second ground pad and the ground conductor, and the short circuit that short-circuits the third ground pad and the ground conductor, It is only a short circuit including two or less through vias.
The differential microstrip line according to claim 3.   The differential type microstrip according to claim 3 or 4 connected to the single end type microstrip line via the single end type microstrip line according to claim 1 or 2, a distributor, and the distributor. Balance-unbalance conversion element with stripline. The distributor is connected to the strip of the single-ended microstrip line at a first connection point, is connected to the first strip conductor of the differential microstrip line at a second connection point, and is connected to a third connection point. And a ring line connected to the second strip conductor of the differential microstrip line,
In the distributor, the electrical length L21 of the path from the second connection point to the first connection point and the electrical length L31 of the path from the third connection point to the first connection point are objects of balance-unbalance conversion. Is set so that the absolute value of the difference | L31−L21 | coincides with λ / 2 + nλ (where n is an arbitrary integer equal to or greater than 0).
In the differential microstrip line, by providing a folded portion in the second strip conductor, the length of the first strip conductor and the length of the second strip conductor are matched.
The balance-unbalance conversion element according to claim 5, wherein The distributor includes (1) a first straight line portion including the first connection point, and (2) a terminal point of the first straight line portion as a start point, and extending in a direction perpendicular to the extending direction of the first straight line portion. A second straight line portion including the second connection point, and (3) extending in a direction opposite to the extending direction of the first straight line portion, with the end point of the second straight line portion being a start point. A third straight line portion including the third connection point, and (4) an end point of the third straight line portion as a start point, and in a direction opposite to the extending direction of the second straight line portion. It has a ring line consisting of a fourth straight part that extends,
The balanced-unbalanced conversion element according to claim 6. The distributor further includes a first stub protruding from the second straight line portion toward the inside of the ring line, and a second stub protruding from the fourth straight line portion toward the inside of the ring line. Yes,
The balance-unbalance conversion element according to claim 7, wherein

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