JP2011249989A - Directional coupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waveguide type directional coupler which is formed of microstrip lines and has enough directionality.SOLUTION: An interval L between two holes for connection 41 and 42 formed in a planar ground conductor 30 on microstrip lines 10 and 20 arranged contiguously is set to satisfy L=(θ/π+n)λ/2, and θ is set at a value to offset one another among five vectors C1,C2,C3,C4 and C5 which are expressed by C1=Aexp(jθ),C2=AAAexp{j(θ+θ+θ-2θ)},C3=AAAexp{j(θ+θ+θ-2θ)},C4=AAAexp{j(θ+θ+θ-2θ)},C5=AAAexp{j(θ+θ+θ-2θ)}. Therefore, a directional coupler which is formed of microstrip lines and has enough directionality is provided.

Description

  The present invention relates to a directional coupler configured using a microstrip line.

As a directional coupler, a directional coupling having a structure in which two coupling through-holes are formed along the length direction of a waveguide on a tube wall shared by two waveguides arranged adjacent to each other in parallel. The vessel is known. In such a directional coupler, by setting the interval between two coupling through holes to an odd multiple of 1/4 of the guide wavelength, two directional couplers traveling in different directions through different coupling through holes can be used. A phase difference of 180 ° is generated between the signals to cancel each other, thereby functioning as a directional coupler.

  However, in such a conventional directional coupler, the frequency at which the two signals completely cancel in a specific direction deviates from the desired frequency, and at the desired frequency, the two signals sufficiently cancel in the specific direction. There is a problem in that it does not match and sufficient directionality cannot be obtained. Therefore, the cause of this problem is presumed that the phase is shifted in the coupling through-hole portion, and the interval between the two coupling through-holes is set to an odd multiple of 1/4 of the guide wavelength in consideration of this phase shift. There has been proposed a directional coupler that attempts to improve the directionality by shifting (see, for example, Patent Document 1).

JP 2008-35187 A

  However, according to the directional coupler proposed in Patent Document 1, although improved compared to the conventional directional coupler, the frequency at which two signals completely cancel in a specific direction is set to a desired frequency. It did not agree and the effect was not enough. Furthermore, when a directional coupler composed of a waveguide is connected to other mounting components mounted on a substrate, there is a problem that conversion from the waveguide to a microstrip line or the like is necessary. It was.

  The present invention has been devised in view of such problems in the prior art, and an object of the present invention is to provide a directional coupler having sufficient directivity configured using a microstrip line. It is in.

The first directional coupler of the present invention includes a planar ground conductor, dielectric layers disposed on both sides thereof, two microstrip lines composed of two line conductors facing each other, and the planar ground conductor. Two coupling through-holes having the same shape and formed at predetermined positions L in the length direction of the two line conductors at positions facing the two line conductors through the dielectric layer of the conductors And both ends of the one microstrip line serve as first and second ports, respectively, and both ends of the other microstrip line serve as third and fourth ports, respectively, and the first and third ports are on the same side. And the second and fourth ports are arranged on the same side, and are inserted from the first port side in each of the two coupling through-hole portions. The reflection coefficient of the reflection to return to the incident direction signal at the site of the coupling through holes to A _{11 exp} (jθ _11), passes through the coupling through holes from said third port side to the first port side The transmission coefficient of the signal is A ₁₃ exp (jθ ₁₃ ), the transmission coefficient of the signal passing from the first port side to the second port side is A ₂₁ exp (jθ ₂₁ ), and the first through the coupling through hole. A ₃₁ exp (jθ ₃₁ ) is a transmission coefficient of a signal passing from the port side to the third port side, and a transmission coefficient of a signal passing from the second port side to the third port side through a coupling through hole A ₃₂ exp (jθ ₃₂ ), the reflection coefficient of the signal incident from the third port side, reflected from the coupling through hole and returning to the incident direction, is A ₃₃ exp (jθ ₃₃ ), from the fourth port side. Connect to the third port The transmission coefficient of a signal _{A 34} exp _(jθ 34), the transmission coefficient of the signal passing through to the fourth port side from the first port side through the coupling through-hole and _{A 41} exp _(jθ 41), wherein When the wavelength of a signal propagating through two microstrip lines is λ, the predetermined distance L is
L = (θ / π + n) λ / 2 (0 <θ <π, where n is 0 or a natural number)
And θ is
C1 = A ₃₁ exp (jθ ₃₁ )
_{C2 = A 21 A 31 A 34} exp {j (θ 21 + θ 31 + θ 34 -2θ)}
_{C3 = A 21 A 11 A 32} exp {j (θ 21 + θ 11 + θ 32 -2θ)}
_{C4 = A 41 A 33 A 34} exp {j (θ 41 + θ 33 + θ 34 -2θ)}
_{C5 = A 41 A 13 A 32} exp {j (θ 41 + θ 13 + θ 32 -2θ)}
The five vectors C1, C2, C3, C4, and C5 indicated by are set to values that cancel each other.

  The second directional coupler of the present invention is the first directional coupler, wherein the dielectric layer has the same thickness and relative dielectric constant on both sides of the planar ground conductor, and the two lines. The conductors have the same cross-sectional shape.

  In this specification, the interval L between the two coupling through-holes means the interval between the centers of the regions where the respective coupling through-holes are formed in the length direction of the two microstrip lines.

  According to the directional coupler of the present invention, the high-frequency signals that are input from the first port and output from the third port sufficiently cancel each other at a desired frequency. An excellent directional coupler can be obtained.

It is a perspective view which shows typically the directional coupler of the example of embodiment of this invention. It is a longitudinal cross-sectional view which shows typically the 1st signal propagation route in the directional coupler shown in FIG. It is a longitudinal cross-sectional view which shows typically the 2nd signal propagation route in the directional coupler shown in FIG. It is a longitudinal cross-sectional view which shows typically the 3rd signal propagation route in the directional coupler shown in FIG. It is a longitudinal cross-sectional view which shows typically the 4th signal propagation route in the directional coupler shown in FIG. It is a longitudinal cross-sectional view which shows typically the 5th signal propagation route in the directional coupler shown in FIG. It is a schematic diagram for demonstrating an example of the calculation method of a transmission coefficient and a reflection coefficient. It is a graph which shows the simulation result of the electrical property of the directional coupler of the example of embodiment of this invention. It is a graph which shows the simulation result of the electrical property of the directional coupler of a comparative example.

  Hereinafter, a directional coupler according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view schematically showing a directional coupler according to an example of an embodiment of the present invention.

  As shown in FIG. 1, the directional coupler of this example includes first and second microstrip lines 10 and 20, and first and second coupling through holes 41 and 42.

  The first and second microstrip lines 10 and 20 include a planar ground conductor 30, first and second dielectric layers 11 and 21 disposed on both sides thereof, and first and second opposing layers therebetween. Line conductors 12 and 22. That is, the first microstrip line 10 includes a planar ground conductor 30, a first dielectric layer 11 disposed on one main surface thereof, and a first line conductor 12 disposed on the surface thereof. It is configured. The second microstrip line 20 is composed of a planar ground conductor 30, a second dielectric layer 21 disposed on the other main surface, and a second line conductor 22 disposed on the surface thereof. ing. The planar ground conductor 30 is shared by the first and second microstrip lines 10 and 20. The first and second line conductors 12 and 22 are arranged in parallel to each other so as to face each other through the first and second dielectric layers 11 and 21 and the planar ground conductor 30.

  The first and second dielectric layers 11 and 21 have the same thickness and relative dielectric constant, and the first and second line conductors 12 and 22 have the same cross-sectional shape. Yes.

  One end of the first microstrip line is a first port 51, the other end is a second port 52, one end of the second microstrip line is a third port 53, and the other end is a fourth port 54. The first port 51 and the third port 53 are arranged on the same side, and the second port 52 and the fourth port 54 are arranged on the same side.

  The first and second coupling through holes 41 and 42 are opposed to the first and second line conductors 12 and 22 through the first and second dielectric layers 11 and 21 of the planar ground conductor 30. The first and second line conductors 12 and 22 are formed at positions at a predetermined interval L in the length direction. Further, the first coupling through hole 41 is provided at a position separated from the first port 51 and the third port 53 by a distance L1 in the length direction of the first and second line conductors 12 and 22. . The first and second coupling through-holes 41 and 42 have the same shape and are perpendicular to the propagation direction of the high-frequency signal (the widths of the first and second line conductors 12 and 22). (Direction) is a long rectangular slot.

According to the directional coupler of this example, the light enters from the first port 51 side at each of the first and second coupling through holes 41 and 42 and is reflected by the coupling through hole. The reflection coefficient of the signal returning to the incident direction is K ₁₁ = A ₁₁ exp (jθ ₁₁ ), and the transmission coefficient of the signal passing from the third port 53 side to the first port 51 side through the coupling through hole is K ₁₃ = A ₁₃ exp (jθ ₁₃ ), the transmission coefficient of the signal passing from the first port 51 side to the second port 52 side is K ₂₁ = A ₂₁ exp (jθ ₂₁ ), the first port 51 side through the coupling through hole The transmission coefficient of the signal passing from the second port 52 side to the third port 53 side is K ₃₁ = A ₃₁ exp (jθ ₃₁ ), and the transmission coefficient of the signal passing from the second port 52 side to the third port 53 side through the coupling through hole K ₃₂ = A ₃₂ exp (jθ ₃₂ ), 3rd port 53 side The reflection coefficient of the signal that is incident on the reflection beam and reflected at the coupling through hole and returning to the incident direction is K ₃₃ = A ₃₃ exp (jθ ₃₃ ), and the signal passing from the fourth port 54 side to the third port 53 side The transmission coefficient is K ₃₄ = A ₃₄ exp (jθ ₃₄ ), and the transmission coefficient of the signal passing from the first port 51 side to the fourth port 54 side through the coupling through hole is K ₄₁ = A ₄₁ exp (jθ ₄₁ ). And when the wavelength of the signal propagating through the first and second microstrip lines 10 and 20 is λ, the first coupling through hole in the length direction of the first and second line conductors 12 and 22 Area where the first coupling through hole 41 is formed in the distance between the first coupling conductor 41 and the second coupling through hole 42 (the length direction of the first and second line conductors 12, 22 (high-frequency signal propagation direction)) L) and the center of the region where the second coupling through hole 42 is formed)
L = (θ / π + n) λ / 2 (0 <θ <π, where n is 0 or a natural number)
And θ is
C1 = A ₃₁ exp (jθ ₃₁ )
_{C2 = A 21 A 31 A 34} exp {j (θ 21 + θ 31 + θ 34 -2θ)}
_{C3 = A 21 A 11 A 32} exp {j (θ 21 + θ 11 + θ 32 -2θ)}
_{C4 = A 41 A 33 A 34} exp {j (θ 41 + θ 33 + θ 34 -2θ)}
_{C5 = A 41 A 13 A 32} exp {j (θ 41 + θ 13 + θ 32 -2θ)}
Are set to such values that the vectors C1, C2, C3, C4, and C5 cancel each other, so that they are input from the first port 51 and travel to the third port 53 via a plurality of propagation routes. Since the high-frequency signals cancel each other and the high-frequency signal output from the third port 53 becomes sufficiently small, a directional coupler with excellent directivity can be obtained. The reason why this effect is obtained will be described below.

  The inventor of the present application, in a conventional waveguide type directional coupler, has various phenomena regarding the phenomenon that sufficient directivity cannot be obtained when the interval between two coupling through holes is set to an odd multiple of 1/4 of the wavelength. Was examined. As a result, there are a plurality of high-frequency signal propagation routes from the first port 51 to the third port 53 other than the two routes conventionally considered, and the influence of the high-frequency signal passing through these routes is not considered. It was clarified that this was the cause and succeeded in obtaining a waveguide-type directional coupler with excellent directivity considering it. As a result of further studies, it was found that the same method can be applied to a directional coupler using a microstrip line, and the present invention has been achieved.

  2 to 6 show main signal propagation routes to be considered among a plurality of high-frequency signal propagation routes from the first port 51 to the third port 53 in the directional coupler of this example shown in FIG. It is a longitudinal cross-sectional view shown typically. In the conventional directional coupler, only the signal propagation route shown in FIGS. 2 and 3 has been considered, but reflection occurs due to impedance discontinuity at the site where the coupling through hole is formed. It was newly discovered that a signal propagation route as shown in FIGS. At this time, the reflection of the high-frequency signal occurs at both ends of the coupling through hole in the signal propagation direction, but when two reflected waves at both ends are combined, it can be considered that the signal is reflected at the center of the coupling through hole. It is illustrated as in FIG. 4 and FIG. Further, it was newly discovered that a signal propagation route as shown in FIG. 6 exists by passing through the coupling through hole a plurality of times. Although there are signal propagation routes other than the signal propagation routes shown in FIGS. 2 to 6, since the intensity of the high-frequency signal passing through these routes is small, it can be ignored in practice.

  Then, the first coupling through hole 41 and the second coupling so that the five high-frequency signals passing through the five signal propagation routes shown in FIGS. 2 to 6 and going to the third port 53 cancel each other. By setting the distance L from the through hole 42, the high-frequency signal output from the third port 53 becomes sufficiently small, and a directional coupler having excellent directivity can be obtained. Since the high-frequency signals are signals having different sizes from each other, they cannot be canceled out only by considering the mutual phase difference as in the conventional directional coupler. Therefore, the magnitude and phase of each of the five high-frequency signals are calculated, and the interval L between the first coupling through hole 41 and the second coupling through hole 42 is set so that the vector sum of them approaches zero. Thus, the five high-frequency signals can be canceled with each other, and a directional coupler having excellent directivity can be obtained.

First, the magnitude and phase of the high-frequency signal passing through each signal propagation route shown in FIGS. The first signal propagation route shown in FIG. 2 passes through the first coupling through-hole 41 from the first port 51 side to the third port 53 side after entering from the first port 51. It is a route to reach. The magnitude and phase of the high-frequency signal passing through this signal propagation route is determined by the transmission coefficient of the signal passing from the first port 51 side to the third port 53 side via the first coupling through hole 41 as K ₃₁ = A Assuming ₃₁ exp (jθ ₃₁ ), it can be expressed as B1 = A ₃₁ exp {j (θ ₃₁ −2π · 2L1 / λ)}. Here, λ is the wavelength of the signal propagating through the first and second microstrip lines 10 and 20. A ₃₁ indicates a change in the magnitude of the high-frequency signal by passing from the first port 51 side to the third port 53 side through the first coupling through hole 41, and θ ₃₁ is the first coupling. The phase change of the high frequency signal by passing from the 1st port 51 side to the 3rd port 53 side through the through-hole 41 is shown. 2π · 2L1 / λ indicates a phase change caused by a high-frequency signal propagating through the first and second microstrip lines 10 and 20 by a distance L1. Note that the change in the magnitude of the high-frequency signal due to propagation through the first and second microstrip lines 10 and 20 is sufficiently small and ignored.

Similarly, the second signal propagation route shown in FIG. 3 passes through the portion of the first coupling through hole 41 from the first port 51 side to the second port 52 side after entering from the first port 51. After passing through the second coupling through hole 42 from the first port 51 side to the third port 53 side, the first coupling through hole 41 is passed from the fourth port 54 side to the third port 53 side. Then, the route reaches the third port 53. The magnitude and phase of the high-frequency signal passing through this signal propagation route is determined by the transmission coefficient of the signal passing from the first port 51 side to the second port 52 side at the portion of the first coupling through hole 41 as K ₂₁ = A ₂₁ exp (jθ ₂₁ ), the transmission coefficient of the signal passing through the second coupling through hole 42 from the first port 51 side to the third port 53 side, K ₃₁ = A ₃₁ exp (jθ ₃₁ ), Assuming that the transmission coefficient of the signal passing from the fourth port 54 side to the third port 53 side at the part of the coupling through hole 41 is K ₃₄ = A ₃₄ exp (jθ ₃₄ ), B2 = A ₂₁ A ₃₁ A ₃₄ exp {J (θ ₂₁ + θ ₃₁ + θ ₃₄ -2θ-2π · 2L1 / λ)}. Here, 2θ represents a phase change caused by a high-frequency signal propagating through the first and second microstrip lines 10 and 20 by a distance L, respectively.

Similarly, the third signal propagation route shown in FIG. 4 passes through the portion of the first coupling through hole 41 from the first port 51 side to the second port 52 side after entering from the first port 51. The second coupling through hole 42 reflects to the first port 51 side, passes through the first coupling through hole 41 from the second port 52 side to the third port 53 side, and passes through the third port 53. This is the route. The magnitude and phase of the high-frequency signal passing through this signal propagation route is determined by the transmission coefficient of the signal passing from the first port 51 side to the second port 52 side at the portion of the first coupling through hole 41 as K ₂₁ = A ₂₁ exp (jθ ₂₁ ), the reflection coefficient of the signal incident from the first port 51 side, reflected at the second coupling through hole 42 and returning to the incident direction, is expressed as K ₁₁ = A ₁₁ exp (jθ ₁₁ ), Assuming that the transmission coefficient of the signal passing from the second port 52 side to the third port 53 side through the first coupling through hole 41 is K ₃₂ = A ₃₂ exp (jθ ₃₂ ), B3 = A ₂₁ A ₁₁ A ₃₂ exp {j (θ ₂₁ + θ ₁₁ + θ ₃₂ −2θ−2π · 2L1 / λ)}.

Similarly, the fourth signal propagation route shown in FIG. 5 passes through the first coupling through hole 41 from the first port 51 side to the fourth port 54 side after entering from the first port 51, 2 is reflected to the third port 53 side at the portion of the coupling through hole 42, passes through the portion of the first coupling through hole 41 from the fourth port 54 side to the third port 53 side and passes to the third port 53. This is the route. The magnitude and phase of the high-frequency signal passing through this signal propagation route is determined by the transmission coefficient of the signal passing from the first port 51 side to the fourth port 54 side via the first coupling through hole 41 as K ₄₁ = A ₄₁ exp (jθ ₄₁ ), the reflection coefficient of a signal incident from the third port 53 side, reflected from the second coupling through hole 42 and returned to the incident direction, is K ₃₃ = A ₃₃ exp (jθ ₃₃ ), Assuming that the transmission coefficient of the signal passing from the fourth port 54 side to the third port 53 side at the site of the first coupling through hole 41 is K ₃₄ = A ₃₄ exp (jθ ₃₄ ), B4 = A ₄₁ A ₃₃ A ₃₄ exp {j (θ ₄₁ + θ ₃₃ + θ ₃₄ −2θ−2π · 2L1 / λ)}.

Similarly, the fifth signal propagation route shown in FIG. 6 passes through the first coupling through hole 41 from the first port 51 side to the fourth port 54 side after entering from the first port 51, The second coupling through hole 42 passes from the third port 53 side to the first port 51 side, and the first coupling through hole 41 passes from the second port 52 side to the third port 53 side to pass through the third port. The route to 53. The magnitude and phase of the high-frequency signal passing through this signal propagation route is determined by the transmission coefficient of the signal passing from the first port 51 side to the fourth port 54 side via the first coupling through hole 41 as K ₄₁ = A ₄₁ exp (jθ ₄₁ ), the transmission coefficient of the signal passing from the third port 53 side to the first port 51 side through the second coupling through hole 42 is K ₁₃ = A ₁₃ exp (jθ ₁₃ ), first Assuming that the transmission coefficient of the signal passing from the second port 52 side to the third port 53 side through the coupling through hole 41 is K ₃₂ = A ₃₂ exp (jθ ₃₂ ), B5 = A ₄₁ A ₁₃ A ₃₂ exp {J (θ ₄₁ + θ ₁₃ + θ ₃₂ -2θ-2π · 2L1 / λ)}.

Therefore, by bringing the vector sum of B1, B2, B3, B4, and B5 close to 0, the high-frequency signals that have passed through the five propagation routes can be canceled with each other. Here, in all the phase components A1 to B5, 2π · 2L1 / λ indicating a phase change caused by the high-frequency signal propagating through the first and second microstrip lines 10 and 20 by the distance L1, respectively. Since it is included and can be ignored when calculating θ, the value of θ that is obtained by removing this component from A1 to B5, respectively, and the following vector sum of C1 to C5 approaches 0 If you ask for.
C1 = A ₃₁ exp (jθ ₃₁ )
_{C2 = A 21 A 31 A 34} exp {j (θ 21 + θ 31 + θ 34 -2θ)}
_{C3 = A 21 A 11 A 32} exp {j (θ 21 + θ 11 + θ 32 -2θ)}
_{C4 = A 41 A 33 A 34} exp {j (θ 41 + θ 33 + θ 34 -2θ)}
_{C5 = A 41 A 13 A 32} exp {j (θ 41 + θ 13 + θ 32 -2θ)}
Next, an example of a method for calculating each transmission coefficient and reflection coefficient in the first coupling through hole 41 and the second coupling through hole 42 necessary for calculating the above C1 to C5 will be described. FIG. 7 is a longitudinal sectional view schematically showing a structure in which the second coupling through hole 42 is eliminated and only the first coupling through hole 41 is present in the directional coupler shown in FIG. is there. By obtaining S parameters in the first to fourth ports 51 to 54 in such a structure by simulation or experiment, the above transmission coefficients and reflection coefficients can be calculated. In FIG. 7, the same components as those of the directional couplers shown in FIGS. 1 to 6 are denoted by the same reference numerals, and redundant description is omitted.

In the structure shown in FIG. 7, S ₁₁ , which is the reflection coefficient at the first port 51, is the reflection coefficient of the signal reflected at the first coupling through hole 41 and returning to the incident direction, K ₁₁ = A ₁₁ exp (jθ ₁₁ ), it can be expressed as S ₁₁ = A ₁₁ exp {j (θ ₁₁ −2π · 2L2 / λ)}. Here, L2 is the distance from the first port 51 to the center of the first coupling through hole 41, and λ is the wavelength. Since the wavelength can be calculated from the cross-sectional shape of the first and second line conductors 12, 22 and the thickness and dielectric constant of the first and second dielectric layers 11, 21, 2π · 2L2 / λ is obtained by calculation. be able to. _Therefore, by obtaining by simulation or measurement of _{S 11,} it is possible to calculate the _{K 11} from _{S 11.} Since the first and second microstrip lines 10 and 20 have the same structure, and the first and second coupling through holes 41 and 42 have the same structure, K ₃₃ matches K ₁₁ . To do.

Similarly, in the structure shown in FIG. 7, S ₂₁ , which is a transmission coefficient from the first port 51 to the second port 52, is from the first port 51 side to the second port 52 side in the first coupling through hole 41. If the transmission coefficient of the signal passing through is K ₂₁ = A ₂₁ exp (jθ ₂₁ ), then it can be expressed as S ₂₁ = A ₂₁ exp {j (θ ₂₁ −2π · (L2 + L3) / λ)}. Here, L2 + L3 is a distance from the first port 51 to the second port 52, and indicates a phase change caused by a high-frequency signal propagating through the first microstrip line 10 by a distance (L2 + L3). 2π · (L2 + L3 ) / Λ can be calculated. _Therefore, by obtaining by simulation or measurement of _{S 21,} it is possible to calculate the _{K 21} from _{S 21.} K ₃₄ matches K ₂₁ .

Similarly, in the structure shown in FIG. 7, S ₃₁ , which is a transmission coefficient from the first port 51 to the third port 53, is transmitted from the first port 51 side to the third port 53 side via the first coupling through hole 41. If the transmission coefficient of the signal passing through is K ₃₁ = A ₃₁ exp (jθ ₃₁ ), it can be expressed as S ₃₁ = A ₃₁ exp {j (θ ₃₁ −2π · 2L2 / λ)}. Here, 2L2 is a propagation distance from the first port 51 to the third port 53, and indicates a phase change caused by a high-frequency signal propagating through the first microstrip line 10 by a distance 2L2. 2π · 2L2 / λ Can be calculated. _Therefore, by obtaining by simulation or measurement of _{S 31,} kill it is possible to calculate the _{K 31} from _{S 31.}

Similarly, in the structure shown in FIG. 7, S ₄₁ , which is a transmission coefficient from the first port 51 to the fourth port 54, is transmitted from the first port 51 side to the fourth port 54 side via the first coupling through hole 41. Assuming that the transmission coefficient of the signal passing through is K ₄₁ = A ₄₁ exp (jθ ₄₁ ), it can be expressed as S ₄₁ = A ₄₁ exp {j (θ ₄₁ −2π · (L2 + L3) / λ)}. Here, L2 + L3 is a distance from the first port 51 to the fourth port 54, and indicates a phase change caused by a high-frequency signal propagating through the first and second microstrip lines 10 and 20 by a distance (L2 + L3). 2π · (L2 + L3) / λ can be obtained by calculation. _Therefore, by obtaining by simulation or measurement of _{S 41,} it is possible to calculate the _{K 41} from _{S 41.} K ₃₂ matches K ₄₁ .

  In this way, the S in the first to fourth ports 51 to 54 having the same cross-sectional shape as the directional coupler to be created and the structure having only one coupling through hole having the same shape as shown in FIG. By obtaining the parameters by simulation or measurement, all reflection coefficients and transmission coefficients necessary for calculating C1 to C5 can be obtained.

  Further, according to the directional coupler of this example, the first and second dielectric layers 11 and 21 located on both sides of the planar ground conductor 30 have the same thickness and permittivity, and two line conductors. Since the cross-sectional shapes of 12 and 22 are equal, as described above, calculation of each transmission coefficient and reflection coefficient can be simplified, and a directional coupler that can be easily designed can be obtained.

  If the distance L between the first coupling through-hole 41 and the second coupling through-hole 42 is too small, the first and second coupling through-holes 41 and 42 are coupled to each other, which is not preferable. Therefore, it is desirable to set larger than 1/4 of the wavelength.

  In the directional coupler of this example, the materials of the first and second dielectric layers 11 and 21 are not particularly limited as long as they have characteristics that do not hinder the transmission of high-frequency signals. However, it is desirable to use dielectric ceramics from the viewpoint of processing accuracy and ease of manufacture. The relative dielectric constant of the dielectric substrate is set to about 2 to 20, for example.

  The first and second line conductors 12 and 22 and the planar ground conductor 30 can be formed using, for example, a highly conductive metal such as aluminum or copper, and the thickness thereof is, for example, 3 μm to 50 μm. It is said to be about.

The directional coupler of this example can be manufactured as follows, for example. First, using a slurry obtained by adding and mixing a suitable organic solvent and solvent to a ceramic raw material powder mainly composed of glass, alumina, aluminum nitride, etc., a ceramic green sheet is formed by a doctor blade method or a calender roll method. Make it. Next, a paste prepared by adding an appropriate oxide, organic solvent, etc. such as alumina, silica, magnesia, etc. to the metal powder is applied to the surface of the ceramic green sheet by a thick film printing method, and with a conductor paste A ceramic green sheet is produced. Next, the obtained ceramic green sheets with a conductive paste are laminated and pressed using a hot press apparatus to form a laminate. And when the dielectric substrate is made of glass ceramics, the obtained laminate is about 850 ° C. to 1000 ° C., alumina ceramics is about 1500 ° C. to 1700 ° C., and aluminum nitride ceramics is about 1600 ° C. to 1900 ° C. It is produced by firing at a peak temperature of about. As the metal powder, when the first and second dielectric layers 11 and 21 are glass ceramics, copper, gold or silver is used, and the first and second dielectric layers 11 and 21 are alumina ceramics or nitrided. In the case of aluminum ceramics, tungsten or molybdenum is preferred.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the spirit of the present invention.

  For example, in the example of the above-described embodiment, the first and second coupling through holes 41 and 42 are rectangular, but other shapes may be used as long as they function as coupling through holes. An oval coupling through hole may be used.

  In the example of the embodiment described above, an example in which one planar ground conductor 30 is shared by the first and second microstrip lines 10 and 20 is shown, but the present invention is not limited to this. . For example, the planar ground conductors 30 of the respective microstrip lines are arranged adjacent to each other, and the first and second coupling through holes 41 and 42 are formed so as to penetrate the respective planar ground conductors 30. It doesn't matter.

  Furthermore, in the example of the embodiment described above, the thickness and the dielectric constant of the first and second dielectric layers 11 and 21 are equal to each other, and the cross sections of the first and second line conductors 12 and 22 are the same. Although an example in which the shapes are equal to each other is shown, the present invention is not limited to this. If the conditions that the wavelengths of the signals propagating through the first and second microstrip lines 10 and 20 are equal are satisfied, the thickness and the dielectric constant of the first and second dielectric layers 11 and 21 may be different from each other. The cross-sectional shapes of the first and second line conductors 12 and 22 may be different.

  Next, a specific example of the directional coupler of the present invention will be described.

  The electrical characteristics in the directional coupler of the example of the embodiment shown in FIG. 1 were calculated by simulation by electromagnetic field analysis. As a calculation condition, the center frequency was set to 76.5 GHz. The first and second line conductors 12 and 22 had a width of 0.12 mm and a thickness of 0.01 mm. The first and second dielectric layers 11 and 21 had a thickness of 0.15 mm and a relative dielectric constant of 9.75. The thickness of the planar ground conductor 30 was 0.02 mm. The cross-sectional shapes of the first and second coupling through holes 41 and 42 were rectangular shapes each having a length of 1.2 mm and a width of 0.1 mm. The distance L between the first and second coupling through holes 41, 42 was 0.507 mm as a result of calculation by the method described above.

Then, the passage characteristic (S ₃₁ ) from the first port 51 to the third port 53 was calculated. FIG. 8 is a graph showing the results, with the horizontal axis representing frequency and the vertical axis representing attenuation. According to the graph shown in FIG. 8, an attenuation pole is formed at the designed center frequency of 76.5 GHz, and its value exceeds −30 dB, and it can be seen that good directivity is obtained.

Moreover, the simulation result of the directional coupler of the comparative example which set the space | interval L of the 1st and 2nd coupling through-holes 41 and 42 to 0.371 mm which is 1/4 of a wavelength like the conventional directional coupler. Is shown in FIG. In the graph of FIG. 9, the horizontal axis represents frequency and the vertical axis represents attenuation. According to the graph shown in FIG. 9, the attenuation pole is formed at 92 GHz, which is far away from the designed center frequency of 76.5 GHz, and the attenuation at the center frequency of 76.5 GHz is only about −10 dB. It turns out that it is not obtained. From the above results, the effectiveness of the present invention was confirmed.

10: First microstrip line
11: First dielectric layer
12: First line conductor
20: Second microstrip line
21: Second dielectric layer
22: Second line conductor
30: Planar ground conductor
41: First coupling through hole
42: Second coupling through hole
51: First port
52: Second port
53: Third port
54: Port 4

Claims (2)

A planar ground conductor, dielectric layers disposed on both sides thereof, two microstrip lines composed of two line conductors facing each other, and the two ground strips via the dielectric layer of the planar ground conductor Two coupling through-holes having the same shape formed at predetermined positions L in the length direction of the two line conductors at positions facing the line conductors, and both ends of the one microstrip line Are the first and second ports, both ends of the other microstrip line are the third and fourth ports, respectively, the first and third ports are arranged on the same side, and the second and fourth ports are A directional coupler arranged on the same side,
In each of the two coupling through-hole portions, the reflection coefficient of a signal incident from the first port side, reflected from the coupling through-hole portion and returning to the incident direction is represented by A ₁₁ exp (jθ ₁₁ ), A ₁₃ exp (jθ ₁₃ ) is the transmission coefficient of the signal passing from the third port side to the first port side through the through hole for transmission, and the transmission of the signal passing from the first port side to the second port side The coefficient is A ₂₁ exp (jθ ₂₁ ), the transmission coefficient of the signal passing through the coupling through hole from the first port side to the third port side is A ₃₁ exp (jθ ₃₁ ), and the coupling through hole is The transmission coefficient of the signal passing from the second port side to the third port side is A ₃₂ exp (jθ ₃₂ ), is incident from the third port side, is reflected at the portion of the coupling through hole, and is incident in the incident direction. Return signal reflection coefficient A ₃₃ exp (jθ _33), said from the transmission factor of the signal passing through to said third port side from the fourth port side _{A 34} exp _(jθ 34), the first port side via the coupling holes first The transmission coefficient of the signal passing to the 4-port side is A ₄₁ exp (jθ ₄₁ ),
When the wavelength of the signal propagating through the two microstrip lines is λ, the predetermined interval L is
L = (θ / π + n) λ / 2 (0 <θ <π, where n is 0 or a natural number)
And θ is
C1 = A ₃₁ exp (jθ ₃₁ )
_{C2 = A 21 A 31 A 34} exp {j (θ 21 + θ 31 + θ 34 -2θ)}
_{C3 = A 21 A 11 A 32} exp {j (θ 21 + θ 11 + θ 32 -2θ)}
_{C4 = A 41 A 33 A 34} exp {j (θ 41 + θ 33 + θ 34 -2θ)}
_{C5 = A 41 A 13 A 32} exp {j (θ 41 + θ 13 + θ 32 -2θ)}
The directional coupler is characterized in that the five vectors C1, C2, C3, C4 and C5 shown in FIG.   The directional coupler according to claim 1, wherein the thickness and relative dielectric constant of the dielectric layer are equal on both sides of the planar ground conductor, and the cross-sectional shapes of the two line conductors are equal.

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