JP2007123972A - Directional coupler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a directional coupler whose directivity is broad and which can be made small-sized. <P>SOLUTION: The directional coupler is provided with: a main line 3 through which a signal is propagated; a first coupling section 4 arranged closely to the main line 3; a second coupling section 5 apart from the first coupling section 4 by a prescribed distance L3 in a signal traveling direction and arranged closely to the main line 3; a composite section 8 connected to the first coupling section 4 via a first delay lien 6 and connected to the second coupling section 5 via a second delay line 7; and an output line 9 connected to the composite section 8, the coupling sections 4, 5 are terminated at ends 4a, 5a in the traveling direction, connected to the delay lines 6, 7 at ends 4b, 5b in a direction opposite to the traveling direction, respectively, and when L1 is defined as the length of the first delay line 6, L2 is defined as the length of the second delay line 7, L3 is defined as the prescribed distance, and λ is defined as the wavelength of the signal, relation of respective lengths L1, L2 and the prescribed distance L3 is specified in expression: L1-L2+L3=λ/2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a directional coupling including a main line for propagating a signal, a pair of coupling parts spaced apart in the signal traveling direction, and a synthesis part connected to each coupling part via a delay line. It is about a vessel.

As this type of directional coupler, a directional coupler disclosed in Japanese Patent Laid-Open No. 2-189005 is known. The basic configuration of this directional coupler will be described with reference to FIG. As described in the prior art of the above publication, the directional coupler 51 has one end formed as a first port (input port Pa) and the other end formed as a second port (output port Pb). A straight main line 53 and a sub-line 54 formed in a substantially H shape are provided. In this case, the two vertical sides 55 and 56 in the sub-line 54 are arranged at positions where one end side (the upper end side in FIG. 7) is formed as a stub and is separated from the main line 53 by a minute distance. Each of the other ends is formed as a third port (coupled output port Pd) and a fourth port (coupled output port Pc), respectively, so as to be inductively coupled to the main line 53. The distance between the sides 55 and 56 is defined as λ / 4, where λ is the wavelength of the signal propagating through the main line 53. In the directional coupler 51 configured as described above, in the state where the signal propagates from the first port to the second port on the main line 53, first, a signal output from the third port (the main line 53). (Traveling wave component of the signal propagating through the line), the line length of one of the two signals input from one end of each of the sides 55 and 56 to the sub-line 54 by inductive coupling is that of the other signal. It is longer by λ / 2 with respect to the line length. For this reason, the two signals cancel each other out of phase. Next, focusing on the signal output from the fourth port (the traveling wave component of the signal propagating through the main line 53), the line length of one of the two signals and the line length of the other signal Are the same. Therefore, the two signals are added with the same phase. Therefore, directionality occurs between the third port and the fourth port.
Japanese Patent Laid-Open No. 2-189005 (page 2, FIG. 4)

  However, the conventional directional coupler described above has the following problems. That is, in this directional coupler, it is necessary to form the sub-line 54 in an H shape and accurately define the distance between the sides 55 and 56 in the sub-line 54 to λ / 4. For this reason, there is a problem that the directivity deteriorates even if the signal wavelength slightly deviates from this λ, that is, the frequency band indicating the directivity is narrow. In addition, since the distance between the sides 55 and 56 cannot be made smaller than λ / 4, the dimension along the signal traveling direction (the length direction of the main line 53) cannot be further shortened. Existing.

  The present invention has been made in view of such problems, and a main object of the present invention is to provide a directional coupler that has a wide directionality and can be miniaturized.

In order to achieve the above object, the directional coupler according to claim 1 includes a main line for propagating a signal, a first coupling portion disposed in proximity to the main line, and the first coupling portion. A second coupling portion that is spaced apart by a predetermined distance on the signal traveling direction side and disposed close to the main line; and is connected to the first coupling portion via a first delay line and A synthesis unit connected to the second coupling unit via a second delay line; and an output line connected to the synthesis unit, wherein the first coupling unit and the second coupling unit are It is terminated at the end on the traveling direction side and is connected to the first delay line and the second delay line at the end opposite to the traveling direction, respectively, and the length of the first delay line is L1, the length L2 of the second delay line, the predetermined distance L3, the wave of the signal When was the lambda, the respective lengths L1, L2 and the predetermined distance L3, are defined in relation represented by the following formula.
L1-L2 + L3 = λ / 2 + n × λ
(N is an integer greater than or equal to zero)

  Further, in the directional coupler according to claim 2, in the directional coupler according to claim 1, the predetermined distance L3 is defined to be equal to or less than a length obtained by subtracting the length L2 from the length L1. .

According to the directional coupler according to claim 1, the main line for propagating the signal, the first coupling portion disposed in the vicinity of the main line, and the signal traveling direction side from the first coupling portion. A second coupling portion disposed close to the main line at a predetermined distance and connected to the first coupling portion via the first delay line and a second delay to the second coupling portion A synthesis unit connected via a line; and an output line connected to the synthesis unit, and the first coupling unit and the second coupling unit are respectively terminated at end portions on the signal traveling direction side. In addition, the first delay line and the second delay line are respectively connected to the first delay line and the second delay line at the end opposite to the traveling direction, and the length of the first delay line is L1, the length of the second delay line is L2, When the predetermined distance is L3 and the signal wavelength is λ,
L1-L2 + L3 = λ / 2 + n × λ
(N is an integer greater than or equal to zero)
Since the lengths L1, L2 and the predetermined distance L3 are respectively defined so as to satisfy the relationship expressed by the following expression, each coupling portion itself can be given directionality. Sufficient directionality can be ensured over a wide frequency band while avoiding the situation of leaking to the outside.

  In the directional coupler according to claim 2, the predetermined distance L3 is defined to be equal to or less than a length obtained by subtracting the length L2 from the length L1. Therefore, according to this directional coupler, the dimension along the length direction of the main line can be shortened by defining the predetermined distance L3 to be shorter than the length L1 minus the length L2. Therefore, it is possible to reduce the size of the coupler.

  Hereinafter, the best mode of a directional coupler according to the present invention will be described with reference to the accompanying drawings. As an example, a directional coupler used for a signal having a frequency of 2.45 GHz will be described as an example.

  First, the configuration of the directional coupler 1 will be described with reference to FIGS. The directional coupler 1 includes a substrate 2, a main line 3, a first coupling unit 4, a second coupling unit 5, a first delay line 6, a second delay line 7, a synthesis unit 8, an output line 9, A pair of lands 10 and 11, a ground pattern 12, and termination resistors 13 and 14 are provided. In this case, the board | substrate 2 is comprised using the double-sided board | substrate made from the dielectric material of a predetermined dielectric constant as an example. The main line 3, the first coupling unit 4, the second coupling unit 5, the first delay line 6, the second delay line 7, the synthesis unit 8, the output line 9, and the pair of lands 10, 11 are formed on this substrate. 1 is formed with a wiring pattern (a conductor pattern made of a metal such as copper) on one surface (the front surface in FIG. 1; the upper surface in FIG. 2). On the other hand, the ground pattern 12 is formed by a wiring pattern on the other surface (the back surface in FIG. 1, the lower surface in FIG. 2) of the substrate 2.

  In this case, as an example, the main line 3 is formed in a straight line so as to span between one opposing side 2a, 2b in the substrate 2, as shown in FIG. In the present example, the main line 3 has one end side (left end side in the figure) defined as an input port Pa and the other end side (right end side in the figure) defined as an output port Pb. The signal input from the input port Pa is output from the output port Pb.

  The first coupling portion 4 is formed in a straight line as an example, and is disposed in the vicinity of the main line 3. Further, the first coupling portion 4 is separated from the main line 3 by a minute distance and is disposed in parallel with the main line 3. The second coupling portion 5 is formed in the same shape as the first coupling portion 4 and is a predetermined distance L3 from the first coupling portion 4 to the signal traveling direction side (the output port Pb side of the main line 3). They are spaced apart. The second coupling portion 5 is separated from the main line 3 by the same distance as the first coupling portion 4 and is disposed in parallel with the main line 3. Further, the first coupling portion 4 and the second coupling portion 5 are formed so that their characteristic impedances are predetermined impedances (100Ω as an example). The first coupling portion 4 and the second coupling portion 5 are terminated by termination resistors 13 and 14 at the respective end portions 4a and 5a on the signal traveling direction side (input port Pa side). Specifically, in this termination structure, the lands 10 and 11 are provided at the end portions on the opposite side of the main line 3 across the end portions 4a and 5a of the first coupling portion 4 and the second coupling portion 5, respectively. They are arranged equidistant from 4a and 5a, respectively. The lands 10 and 11 are connected to the ground pattern 12 through through holes 15 and 16 formed in the substrate 2 as shown in FIG. A termination resistor 13 having a predetermined impedance (100Ω as an example) is connected between the end 4 a of the first coupling portion 4 and the land 10 thus arranged, and the end of the second coupling portion 5 is connected. By connecting a termination resistor 14 having a predetermined impedance (100Ω as an example) between the portion 5a and the land 11, the first coupling portion 4 and the second coupling portion 5 are connected to each other at the end portions 4a and 5a. Termination resistors 13 and 14 respectively terminate.

One end side of the first delay line 6 is connected to an end portion (end portion on the input port Pa side) 4 b opposite to the signal traveling direction in the first coupling portion 4, and the other end side is a combining portion. 8 is connected. One end side of the second delay line 7 is connected to an end portion (end portion on the input port Pa side) 5 b opposite to the signal traveling direction in the second coupling portion 5, and the other end side is a combining portion. 8 is connected. In this case, when the length of the first delay line 6 is L1, the length of the second delay line 7 is L2, and the wavelength of the signal propagating through the main line 3 is λ, each length L1, L2 and The predetermined distance L3 is defined by the relationship expressed by the following formulas (1) and (2).
L1-L2 + L3 = λ / 2 + n × λ (1)
L1-L2> L3 (2)
Here, n is an integer greater than or equal to zero (zero in this example as an example). In addition, the characteristic impedance of each of the delay lines 6 and 7 is defined as a predetermined impedance (100Ω as an example).

  The output line 9 is formed in a straight line from one side (lower side in the figure) 2c sandwiched between a pair of opposite sides 2a and 2b in the substrate 2 toward the main line 3 side, and its characteristic impedance is predetermined. It is defined as impedance (50Ω as an example). Further, the end portion on the main line 3 side in the output line 9 is configured as a combining portion 8, and the end portion on the side 2 c side is defined as a combined output port Pc.

  Next, the operation of the directional coupler 1 will be described.

  In a state where a signal is input from the input port Pa of the main line 3 and this signal propagates through the main line 3 and is output from the output port Pb of the main line 3, the signal is disposed close to the main line 3. The first coupling portion 4 and the second coupling portion 5 are inductively coupled to the main line 3. For this reason, the first coupling unit 4 has a traveling wave component in phase with the traveling wave signal propagating through the main line 3, and a reflected wave in phase with the signal propagating through the main line 3. The reflected wave component of is induced. Similarly, the traveling wave component having the same phase as that of the traveling wave propagating through the main line 3 and the reflected wave of the signal propagating through the main line 3 are also applied to the second coupling unit 5. A reflected wave component of the phase is induced. Next, the traveling wave component and the reflected wave component induced in the first coupling unit 4 propagate to the synthesis unit 8 via the first delay line 6. Further, the traveling wave component and the reflected wave component induced in the second coupling unit 5 propagate to the synthesis unit 8 through the second delay line 7. The combining unit 8 combines the traveling wave component and the reflected wave component propagated from the first coupling unit 4 and the traveling wave component and the reflected wave component propagated from the second coupling unit 5. In this case, for each reflected wave component induced in each coupling part 4, 5, the lengths L 1, L 2 of each delay line 6, 7 and the predetermined distance L 3 of each coupling part 4, 5 are expressed by the above equation (1). Since the relationship is defined by the notation, both phases are shifted by λ / 2 when propagating to the combining unit 8. Therefore, by combining by the combining unit 8, the reflected wave components respectively induced in the coupling units 4 and 5 cancel each other.

On the other hand, for the traveling wave components induced in the coupling portions 4 and 5, the difference L4 in the distance between the propagation paths is expressed by the following equation (3).
L4 = L1-L2-L3 (3)
In this case, since the lengths L1 and L2 of the delay lines 6 and 7 and the predetermined distance L3 between the coupling portions 4 and 5 are defined by the relationship expressed by the above equation (1), the difference L4 between the distances. Is further expressed by the following equation (4).
L4 = L1-L2 + L3-2 × L3
= Λ / 2-2 × L3 (4)
Further, the predetermined distance L3 between the coupling portions 4 and 5 is not zero. Therefore, the propagation path distance difference L4 is always a value different from λ / 2. Accordingly, the traveling wave components induced in the coupling parts 4 and 5 are not canceled out even when synthesized in the synthesis part 8. Therefore, the combined traveling wave component generated by combining the traveling wave components by the combining unit 8 propagates through the output line 9 and is output from the combined output port Pc.

  As described above, according to the directional coupler 1, the first coupling portion 4 is disposed in the vicinity of the main line 3, and only a predetermined distance L3 extends from the first coupling portion 4 to the signal traveling direction side. A second coupling portion 5 is disposed in the vicinity of the main line 3 so as to be spaced apart, and the first coupling portion 4 is connected to the combining portion 8 via the first delay line 6 (length L1) and the first 2 connecting the second delay line 7 (length L2) to the synthesizing unit 8, and for the first coupling unit 4 and the second coupling unit 5, the traveling direction side end 4a, 5a is terminated with termination resistors 13 and 14, respectively, and connected to the first delay line 6 and the second delay line 7 at end portions 4b and 5b opposite to the traveling direction, respectively, and L1-L2 + L3 = λ / Each length L1, L2 and a predetermined distance L3 are defined so as to be represented by 2. Thus, since each coupling part 4, 5 itself can have directionality, while avoiding a situation where a reflected wave component of the signal is output from the coupling output port Pc (a situation where it leaks to the output line 9), Sufficient directionality can be ensured over a wide frequency band.

  Further, according to the directional coupler 1, as shown in the above formula (2), the length L1 of the second delay line 7 is subtracted from the length L1 of the first delay line 6 as shown in the above formula (2). By defining the predetermined distance L3 to be short, in this example in which n in the above formula (1) is zero, the predetermined distance L3 can be made less than λ / 4. As a result, the dimension of the substrate 2 along the signal traveling direction (mainly The dimension along the length direction of the line 3) can be shortened compared to the conventional configuration.

  In addition, this invention is not limited to said structure. For example, a configuration using a resistance synthesizer as in the directional coupler 21 shown in FIG. The directional coupler 21 includes a substrate 2, a main line 3, a first coupling unit 24, a second coupling unit 25, a first delay line 26, a second delay line 27, a combining unit 28, and an output line 29. , A pair of lands 10 and 11, a ground pattern 12, and termination resistors 33 and 34 are provided. In addition, about the structure same as the directional coupler 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted. In this case, the main line 3, the first coupling unit 24, the second coupling unit 25, the first delay line 26, the second delay line 27, the coupling pattern 28a in the synthesis unit 28 described later, the output line 29, and The pair of lands 10 and 11 are formed on one surface of the substrate 2 by a wiring pattern.

  The first coupling portion 24 and the second coupling portion 25 are configured so that the characteristic impedance is 50Ω as an example, and the end portions 24a and 25a on the signal traveling direction side are termination resistors 33 and 34 (50Ω). Except for being terminated at, each of the coupling portions 4 and 5 of the directional coupler 1 has the same configuration. One end side of the first delay line 26 is connected to an end portion (end portion on the input port Pa side) 24 b opposite to the signal traveling direction in the first coupling portion 24, and the second delay line 27 is The one end side of the second coupling portion 25 is connected to an end portion (end portion on the input port Pa side) 25b opposite to the signal traveling direction. Further, the first delay line 26 and the second delay line 27 are configured so that their characteristic impedance is 50Ω as an example. The synthesizer 28 includes a coupling pattern 28a and three resistors 28b, 28c, and 28d, and is configured as a resistor synthesizer. In this case, the coupling pattern 28a is connected to the first delay line 26, the second delay line 27, and the output line 29 through the resistors 28b, 28c, and 28d. With this configuration, the synthesizer 28 synthesizes the traveling wave components and the reflected wave components of the signals propagating through the delay lines 26 and 27, and outputs a signal obtained by the synthesis to the output line 29. The output line 29 is configured such that its characteristic impedance is 50Ω as an example, and outputs the signal synthesized in the synthesis unit 28 from the combined output port Pc. Also in the directional coupler 21, the length of the first delay line 26 is L1, the length of the second delay line 27 is L2, the distance between the coupling parts 4 and 5 is a predetermined distance L3, and the main line 3 The lengths L1 and L2 and the predetermined distance L3 are defined in the relationship expressed by the above formulas (1) and (2), where λ is the wavelength of the signal propagating through.

  This directional coupler 21 also functions in the same manner as the directional coupler 1 and outputs only the traveling wave component of the signal from the combined output port Pc. Also, with this directional coupler 21, since the coupling portions 24 and 25 are terminated at the end portions 24 a and 25 a on the traveling direction side of the signal, in the same manner as the directional coupler 1, Sufficient directivity can be ensured over a wide frequency band while avoiding a situation where the reflected wave component is output from the coupled output port Pc (a situation where the reflected wave component leaks to the output line 29). Furthermore, as shown in the above formula (2), by defining the lengths L1 and L2 and the predetermined distance L3, the dimensions of the substrate 2 along the signal traveling direction (as in the directional coupler 1) ( Since the dimension along the length direction of the main line 3 can be shortened compared to the conventional configuration, the size of the coupler can be reduced.

  Further, although the directional couplers 1 and 21 having the frequency of the signal propagating through the main line 3 of 2.45 GHz have been described above, the directional couplers used for signals of various frequencies are not limited to the signals of this frequency. Of course, the present invention can also be applied to the above. Further, in the above formula (1), an example in which n is 0 has been described. However, by configuring the directional coupler so as to satisfy the above formula (1) even when n is an integer of 1 or more, Similar to the directional couplers 1 and 21, sufficient directivity over a wide frequency band is avoided while avoiding a situation where a reflected wave component of the signal is output from the coupling output port (a situation where the reflected wave component leaks to the output line). Of course, it can be ensured. Further, the example in which the predetermined distance L3 is defined below the length obtained by subtracting the length L2 from the length L1 has been described above. However, the predetermined distance L3 and the length obtained by subtracting the length L2 from the length L1 should be defined equally. You can also.

  Specific examples will be given to explain the present invention in detail. As an example, an example of the directional coupler 1 will be described. As an example, a directional coupler having a usage frequency of 2.45 GHz will be described as an example.

  As shown in FIGS. 1 and 2, a substrate made of Teflon (registered trademark) having a relative dielectric constant of about 2.6, a width of 25.86 mm, a length of 28.34 mm, and a thickness of 0.8 mm (double-sided substrate). 2, the main line 3, the first coupling unit 4, the second coupling unit 5, the first delay line 6, the second delay line 7, the combining unit 8, and the output line 9 are provided on one surface thereof. The pair of lands 10 and 11 are formed by a wiring pattern, the ground pattern 12 is formed on the other surface, and the pair of lands 10 and 11 and the ground pattern 12 are connected to the through holes 15 as shown in FIG. , 16 connected. Further, the lengths of the first coupling part 4 and the second coupling part 5 were each formed to 2 mm, and the mutual distance was defined to be 11 mm (predetermined distance L3). The first delay line 6 was formed to a length of 34.5 mm, and the second delay line 7 was formed to a length of 5.5 mm. In addition, a termination resistor 13 having a predetermined impedance (100Ω as an example) is attached between the end 4 a of the first coupling portion 4 and the land 10 to terminate the end 4 a of the first coupling portion 4. Similarly, a termination resistor 14 having a predetermined impedance (100Ω as an example) is attached between the end 5a of the second coupling portion 5 and the land 11, and the end 5a of the second coupling portion 5 is terminated. did. In this way, a sample of a directional coupler was prepared and used as an example. In this embodiment, since the lengths L1 and L2 are 34.5 mm and 5.5 mm, respectively, and the predetermined distance L3 is 11 mm, L1−L2 + L3 = 34.5−5.5 + 11 = 40. Further, since the relative dielectric constant of the substrate 2 is 2.6, the signal wavelength λ is shortened from 122.4 mm to 76 mm. Therefore, 40 mm calculated as described above is substantially equal to λ / 2, and this embodiment satisfies the above formula (1) when n = 0.

  Further, as shown in FIG. 7, a substrate made of Teflon (registered trademark) having a relative dielectric constant of about 2.6, a width of 34.12 mm, a length of 55.42 mm, and a thickness of 0.8 mm (double-sided substrate). 52, a linear main line 53 having one end formed as an input port Pa and the other end formed as an output port Pb on one surface thereof, and a sub-line 54 formed substantially in an H shape Was formed as a comparative example by forming a sample of a directional coupler. In this case, each of the two vertical sides 55 and 56 in the sub-line 54 is formed as a stub at each one end side (upper end side in FIG. 7), and when the signal propagates to the main line 3, the main line 3. It functions as a coupling part that is inductively coupled with. Each side 55, 56 functions as the first combined output port Pd and the second combined output port Pc at the other end side (lower end side in FIG. 7). Further, when the wavelength of the signal propagating through the main line 52 is λ, the distance between the sides 55 and 56 is defined as approximately λ / 4 (= 20 mm). Moreover, the length of each side 55 and 56 was prescribed | regulated to 41 mm.

  Next, the directionality, matching, and degree of coupling of the directional couplers according to Examples and Comparative Examples were measured. Note that a signal of 2.45 GHz was used as a signal propagated to the main line 3. The measurement results are shown in FIGS. In each of FIGS. 4, 5, and 6, a region where a plurality of points are scattered indicates a region that can be used as a directional coupler. Moreover, in each FIG.4,5,6, a continuous line shows the characteristic of an Example and a broken line shows the characteristic of a comparative example.

  According to the directional characteristic diagram shown in FIG. 4, in the directional coupler according to the comparative example, a directivity of −30 dB or more is ensured only in a narrow frequency band (about 0.4 GHz) centered on 2.45 GHz. Yes. On the other hand, in the directional coupler according to the embodiment, sufficient directivity of −30 dB or more is ensured in an extremely wide frequency band (2.26 GHz to 2.64 GHz) centering on 2.45 GHz. . This is because, in the directional coupler according to the comparative example, the two coupling portions do not have directional characteristics. However, in the directional coupler according to the embodiment, each coupling portion 4, 5 has an end portion 4 a on the traveling direction side, By being terminated at 5a, each coupling part 4, 5 itself has a configuration having directionality. For this reason, due to a synergistic effect between the point that each coupling part 4, 5 itself has directionality and the reflected wave component of the signal propagating through the main line 3 cancel each other by the synthesis in the synthesis unit 8, It is considered that the performance has been greatly improved.

  Further, according to the matching characteristic diagram shown in FIG. 5, in the directional coupler according to the comparative example, the frequency band where the matching can be taken (frequency band where −30 dB or more) is centered around 2.45 GHz (about 2.34 GHz or more and 2.58 GHz or less). On the other hand, in the directional coupler according to the embodiment, matching is achieved in an extremely wide frequency band centering on 2.45 GHz. This is because, in the directional coupler according to the comparative example, the tip portions of the two vertical sides 55 and 56 in the sub line 54 functioning as a coupling portion function as a stub, and therefore matching can be achieved only at a specific frequency. On the other hand, in the directional coupler according to the embodiment, the coupling portions 4 and 5 are terminated with a predetermined impedance, and the characteristic impedances of the coupling portions 4 and 5 and the delay lines 6 and 7 are the predetermined impedance. Since it is defined as the same impedance as the impedance, unlike the comparative example, it is considered that it does not have a frequency characteristic that can be matched only in a specific frequency band.

  Further, according to the degree of coupling characteristic diagram shown in FIG. 6, in the directional coupler according to the comparative example, the degree of coupling largely varies in a curve according to the frequency, and the degree of coupling is −− at frequencies of 2.70 GHz or higher. Decreases to less than 31 dB. In contrast, the directional coupler according to the embodiment shows a frequency characteristic that changes linearly and gently, and a required degree of coupling is ensured in a wider frequency band (from 2.00 GHz to 3.00 GHz). Has been.

  Further, in the directional coupler according to the comparative example, the distance between the two vertical sides 55 and 56 in the sub-line 54 functioning as a coupling portion needs to be regulated to 1/4 of the signal wavelength λ. It is limited to shorten the dimensions of On the other hand, in the directional coupler according to the embodiment, the predetermined distance L3 that is the interval between the coupling portions 4 and 5 can be changed within a range that satisfies the above formula (1). Specifically, the predetermined distance L3 can be defined to be less than λ / 4 by defining as in the above formula (2). For this reason, in the directional coupler which concerns on an Example, the distance between the two coupling parts 4 and 5 is prescribed | regulated to the predetermined distance L3 shorter than the directional coupler which concerns on a comparative example. As a result, the dimension in the width direction of the substrate 2 is defined to be shorter than the substrate 52 of the directional coupler according to the comparative example.

1 is a configuration diagram of a directional coupler 1. FIG. It is the XX sectional view taken on the line in FIG. 3 is a configuration diagram of another directional coupler 21. FIG. It is a frequency characteristic figure of directionality. It is a frequency characteristic figure of matching. It is a frequency characteristic figure of coupling degree. It is a block diagram of the directional coupler 51 as a comparative example.

Explanation of symbols

1,21 Directional coupler 3 Main line 4,24 First coupling unit 5,25 Second coupling unit 6,26 First delay line 7,27 Second delay line 8,28 Combining unit 9,29 Output line L3 Predetermined distance

Claims (2)

A main line for propagating a signal, a first coupling portion disposed in the vicinity of the main line, a predetermined distance away from the first coupling portion in the signal traveling direction side, and the proximity to the main line And a second coupling portion disposed in the first coupling portion and a first delay line connected to the first coupling portion and a second delay line connected to the second coupling portion. A synthesis unit and an output line connected to the synthesis unit;
The first coupling portion and the second coupling portion are terminated at the end portion on the traveling direction side, and the first delay line and the second delay are disposed at the end portion in the direction opposite to the traveling direction. Connected to each track,
When the length of the first delay line is L1, the length of the second delay line is L2, the predetermined distance is L3, and the wavelength of the signal is λ, the lengths L1, L2 and the predetermined A directional coupler in which the distance L3 is defined by the relationship represented by the following formula.
L1-L2 + L3 = λ / 2 + n × λ
(N is an integer greater than or equal to zero)   The directional coupler according to claim 1, wherein the predetermined distance L3 is defined to be equal to or less than a length obtained by subtracting the length L2 from the length L1.

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