WO2020179476A1 - Circuit board and antenna module - Google Patents

Abstract

On a circuit board (150), a branch circuit for branching a high-frequency signal is formed. The circuit board (150) comprises: a dielectric substrate (130); a ground electrode (GND) placed on the dielectric substrate (130); and a line conductor (400) that is placed on a dielectric substrate (105) so as to face the ground electrode (GND) and is configured to transmit the high-frequency signal. The line conductor (400) comprises: a first conductor (410A) that receives the high-frequency signal; a second conductor (420A) and a third conductor (421A) that branch the high-frequency signal that is input to the first conductor (410A) and output the branched signal; and a matching conductor (430) connected between the first conductor (410A) and the second conductor (420A) or the third conductor (421A). The line conductor (400) has an equal line width around a fork (CP). An effective dielectric constant between the matching conductor (430) and the ground electrode (GND) is different from an effective dielectric constant between the first to third conductors and the ground electrode (GND).

Description

Circuit board and antenna module

The present disclosure relates to a circuit board and an antenna module, and more specifically to a technique for reducing the loss of a circuit board including a branch circuit for a high frequency signal.

In a communication device such as a smartphone, an array antenna having a plurality of antenna elements (radiating elements) may be adopted. In such an array antenna, a branch circuit for distributing the high frequency signal supplied from the feeding circuit to a plurality of antenna elements is used.

Japanese Unexamined Patent Publication No. 2001-196849 (Patent Document 1) discloses an array antenna provided with a branch circuit for distributing a high frequency signal from a power feeding circuit. In the branch circuit of JP-A-2001-196849 (Patent Document 1), when the wavelength of the high-frequency signal to be transmitted is λ, an impedance matching transmission line having a line length of λ / 4 is provided. , The impedance at the input end and the output end of the branch circuit is configured to match.

Japanese Unexamined Patent Publication No. 2001-196849

Generally, the impedance of the transmission line for impedance matching in the branch circuit is different from the impedance at the input end and the output end of the branch circuit. In the branch circuit disclosed in Japanese Patent Application Laid-Open No. 2001-196849 (Patent Document 1), the impedance of the transmission line for impedance matching is adjusted by changing the line width of the transmission line.

However, if there is a part where the line width is different in the line conductor (transmission line) of the branch circuit, signal reflection occurs in that part, which may increase the reflection loss.

The present disclosure has been made to solve the above-mentioned problems, and an object thereof is to match impedance and reduce loss in a circuit board in which a branch circuit is formed.

A branch circuit for branching a high frequency signal is formed on a circuit board according to a certain aspect of the present disclosure. The circuit board includes a dielectric substrate, a ground electrode arranged on the dielectric substrate, and a line conductor arranged on the dielectric substrate facing the ground electrode and configured to transmit a high frequency signal. The line conductors are a first conductor to which a high-frequency signal is input, a second conductor and a third conductor for branching and outputting a high-frequency signal input to the first conductor, and a first conductor, a second conductor, and a third conductor. Includes matching conductors connected between and. The line widths before and after the branch point in the line conductor are equal. The effective permittivity between the matching conductor and the ground electrode is different from the effective permittivity between the first to third conductors and the ground electrode.

According to the present disclosure, in a circuit board on which a branch circuit is formed, the effective dielectric constant between the matching conductor for impedance matching and the ground electrode, the input conductor (first conductor), and the output conductor after branching (second conductor). By making the effective dielectric constant between the conductor (conductor, third conductor) and the ground electrode different, the line width of the line conductor before and after the branch point can be made equal while matching the impedance. As a result, the reflection loss caused by the change in the line width can be suppressed, so that the loss of the entire circuit board can be reduced. Therefore, in the circuit board on which the branch circuit is formed, the impedance before and after the branch point can be matched and the loss can be reduced.

FIG. 5 is a block diagram of a communication device equipped with an antenna module to which a circuit board according to the first embodiment is applied. FIG. 3 is a partial cross-sectional view of the circuit board according to the first embodiment. FIG. 3 is a diagram for explaining a two-branch type branch circuit in the first embodiment. FIG. 3 is a diagram for explaining a three-branch type branch circuit in the first embodiment. It is a figure which shows an example of the perspective view of the circuit board which formed the 2 branch type branch circuit. It is a figure for demonstrating the comparison between the insertion loss of the circuit board according to Embodiment 1 and the insertion loss of the comparative example. It is a figure for demonstrating the 1st example of the branch circuit at the time of performing the phase adjustment of an output signal. It is a figure for demonstrating the 2nd example of the branch circuit at the time of performing the phase adjustment of an output signal. FIG. 9 is a partial cross-sectional view of the circuit board according to the second embodiment. FIG. 9 is a diagram for explaining a two-branch type branch circuit in the second embodiment. It is a figure for demonstrating the 3 branch type branch circuit in Embodiment 2. FIG. FIG. 10 is a diagram showing an example of a perspective view of a circuit board in which a two-branch type branch circuit is formed in the second embodiment. It is a figure for demonstrating the 1st example of the branch circuit at the time of adjusting the phase of an output signal. It is a figure for demonstrating the 2nd example of the branch circuit at the time of performing the phase adjustment of an output signal.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. It should be noted that the same or corresponding parts in the drawings are designated by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
(Basic configuration of communication device)
FIG. 1 is an example of a block diagram of a communication device 10 equipped with an antenna module 100 to which the circuit board according to the first embodiment is applied. The communication device 10 is, for example, a mobile terminal such as a mobile phone, a smartphone or a tablet, or a personal computer having a communication function. An example of the frequency band of the radio wave used for the antenna module 100 according to the present embodiment is a radio wave in the millimeter wave band having a center frequency of, for example, 28 GHz, 39 GHz, 60 GHz, etc., but radio waves in frequency bands other than the above are also available. Applicable.

Referring to FIG. 1, the communication device 10 includes an antenna module 100 and a BBIC 200 forming a baseband signal processing circuit. The antenna module 100 includes an RFIC 110, which is an example of a power feeding circuit, and an antenna device 120. The communication device 10 up-converts the signal transmitted from the BBIC 200 to the antenna module 100 into a high-frequency signal and radiates it from the antenna device 120, and down-converts the high-frequency signal received by the antenna device 120 to process the signal in the BBIC 200. To do.

The antenna device 120 is an array antenna in which a plurality of antenna elements 121 are arranged in an array. FIG. 1 shows an example in which 16 antenna elements 121 are arranged in a 4 × 4 two-dimensional manner. The antenna device 120 may be a one-dimensional array in which a plurality of antenna elements 121 are arranged in a row. Further, in the present embodiment, an example in which the antenna element 121 is a patch antenna having a substantially square flat plate shape will be described, but the antenna element 121 is a linear antenna such as a monopole antenna or a dipole antenna, or It may be a slot antenna or the like.

The RFIC 110 includes switches 111A to 111D, 113A to 113D and 117, power amplifiers 112AT to 112DT, low noise amplifiers 112AR to 112DR, attenuators 114A to 114D, phase shifters 115A to 115D, and signal combiner/splitters. 116, a mixer 118, and an amplifier circuit 119.

When transmitting a high frequency signal, the switches 111A to 111D and 113A to 113D are switched to the power amplifiers 112AT to 112DT side, and the switch 117 is connected to the transmitting side amplifier of the amplifier circuit 119. When receiving a high frequency signal, the switches 111A to 111D and 113A to 113D are switched to the low noise amplifiers 112AR to 112DR side, and the switch 117 is connected to the receiving side amplifier of the amplifier circuit 119.

The signal transmitted from the BBIC 200 is amplified by the amplifier circuit 119 and up-converted by the mixer 118. The up-converted transmission signal, which is a high-frequency signal, is divided into four by the signal combiner/splitter 116, passes through four signal paths, and is fed to the antenna element 121. At this time, the directivity of the antenna device 120 can be adjusted by individually adjusting the degree of phase shift of the phase shifters 115A to 115D arranged in each signal path.

The received signal, which is a high-frequency signal received by each antenna element 121, passes through four different signal paths and is combined by the signal synthesizer / demultiplexer 116. The received signals thus combined are down-converted by mixer 118, amplified by amplifier circuit 119, and transmitted to BBIC 200.

The RFIC 110 is formed as, for example, a one-chip integrated circuit component including the above circuit configuration. Alternatively, the devices (switch, power amplifier, low noise amplifier, attenuator, phase shifter) corresponding to each antenna element 121 in the RFIC 110 may be formed as an integrated circuit component of one chip for each corresponding antenna element 121. ..

In the antenna device 120 of the first embodiment, four antenna elements 121 arranged in a row are grouped into one group (hereinafter, also referred to as “antenna group”), and the antenna elements 121 of the same antenna group are combined. Is supplied with a common high frequency signal from the RFIC 110. For example, in the antenna device 120 of FIG. 1, a high frequency signal via the switch 111A is supplied to the uppermost stage (first stage) antenna group via the circuit board 150A in which the branch circuit is formed. Similarly, a high frequency signal via the switch 111B is supplied to the second stage antenna group via the circuit board 150B. A high frequency signal via the switch 111C is supplied to the third stage antenna group via the circuit board 150C, and a high frequency signal via the switch 111D is supplied to the lowest stage (fourth stage) antenna group via the circuit board 150D. Supplied via. In the following description, the circuit boards 150A to 150D on which these branch circuits are formed are also collectively referred to as "circuit board 150".

(Explanation of branch circuit)
In equipment that transmits high-frequency signals, in general, the input impedance or output impedance of each circuit connected to the signal transmission path should be close to the impedance of the transmission line connected to the input end or output end of each circuit. This suppresses the loss due to impedance mismatch. The impedance of the transmission line is, for example, 50Ω, and is also referred to as “characteristic impedance”.

Even in the branch circuit that distributes the signal from the RFIC 110 to the plurality of antenna elements 121 as described above, it is necessary to match the impedance at the input end of the branch circuit or the output end after branching in order to reduce the loss. Become.

When a branch circuit is formed by a strip line or a microstrip line in which a line conductor is formed in a substrate, a plurality of output conductors are connected in parallel to the input conductor before and after the branch point of the line conductor. Therefore, when a plurality of output conductors are simply connected to the input conductor, the impedance at the branch point when viewed from the input conductor becomes smaller than the desired characteristic impedance. In order to eliminate this impedance mismatch, the branch circuit generally includes a matching circuit for matching the impedance before and after the branch point on the input conductor side of the branch point or on the output conductor side of the branch point. It is formed.

As such a matching circuit, a matching circuit formed of a line conductor having a line length of λ / 4 is known when the wavelength of the transmitted high frequency signal in the substrate is λ. Assuming that the impedances of the two lines connected to the matching circuit are Z _a and Z _c , respectively, the impedance Z _{b of the} matching circuit can be generally expressed by the following equation (1).

Z _b = √ (Z _a Z _c )… (1)
When a branch circuit is formed using line conductors, if the line conductors have the same thickness and the same line length, the impedance of the line conductor is basically determined by the line width. Therefore, when a matching circuit is provided for impedance matching before and after the branch point in the branch circuit, the line width changes discontinuously at the connection portion between the input conductor or the output conductor and the matching circuit. Then, the difference in the line width may cause signal reflection, resulting in an increase in reflection loss.

In the first embodiment, in a circuit board in which a branch circuit is formed by a strip line or a microstrip line, between the input conductor and / or the output conductor before and after the matching circuit and the ground electrode, or between the matching circuit and the ground electrode. By forming a space in the dielectric layer between and reducing the effective dielectric constant, the input conductor and the output conductor and the matching circuit have the same line width. With such a configuration, in the circuit board on which the branch circuit is formed, the impedance can be matched and the loss due to reflection can be reduced.

The detailed configuration of the circuit board according to the first embodiment will be described below. FIG. 2 is a partial cross-sectional view of the circuit board according to the first embodiment.

Referring to FIG. 2, the circuit board 150 includes a dielectric substrate 130, a ground electrode GND, and a line conductor 160 for forming a branch circuit. In the example of FIG. 2, the circuit board 150 is formed as a strip line. That is, the ground electrode GND is arranged to face the front surface side layer and the back surface side layer of the dielectric substrate 130, and the line conductor 160 is arranged in the layer between the two ground electrode GNDs.

Here, impedance Z of the line conductor 160, if the effective dielectric constant between the line conductor 160 and the ground electrode GND and epsilon _r, inversely proportional to the square root of the effective dielectric constant epsilon _r as in the following equation (2) Is known to do.

Z∝1/√ε _r (2)
Therefore, when the space 170 is formed between the line conductor 160 and the ground electrode GND to reduce the effective permittivity, the impedance of the line conductor 160 in that portion increases. Then, by increasing the line width of the line conductor 160, the increased impedance can be reduced to match the impedance when there is no space 170. In this way, by forming a space of an appropriate size in the portion of the dielectric substrate corresponding to the line conductor whose line width is relatively narrow, the line width of the entire line conductor can be made relatively wide. Can be matched to the part.

FIG. 3 is a diagram for explaining a two-branch type branch circuit that outputs a high frequency signal received at an input end to two output ends. Further, FIG. 4 is a diagram for explaining a three-branch type branch circuit that outputs a high-frequency signal to three output ends.

In FIGS. 3 and 4, a comparative example in which a branch circuit is formed on a substrate having a uniform effective dielectric constant is shown in the left column, and the branch circuit of the first embodiment is shown in the right column. Further, in FIGS. 3 and 4, the upper row shows the case where the matching circuit is formed on the input conductor side (trunk side) of the branch point CP, and the lower row shows the case where the output conductor side (trunk side) of the branch point CP is formed. The case where a matching circuit is formed on the branch side is shown.

<In the case of 2 branches>
First, a case where a matching circuit is formed on the trunk side of the upper stage will be described with reference to FIG. In the comparative example, the line conductor 300 forming the branch circuit includes an input conductor (first conductor) 310 having an input end IN, an output conductor (second conductor) 320 having an output end OUT1, and an output conductor having an output end OUT2. It includes a (third conductor) 321 and a matching conductor 330 that functions as a matching circuit. The matching conductor 330 has a line length of λ/4, and is connected between the branch point CP to which the output conductor 320 and the output conductor 321 are connected and the input conductor 310.

If the impedance at the input conductor 310 and two output conductors 320 and 321 to the characteristic impedance of _{Z 0,} the impedance becomes _Z 0/2 at the branch point CP, the impedance of the matching conductor 330, the above equation (1) Therefore, Z ₁ = Z ₀ / √2. That is, since the impedance Z ₁ of the matching conductor 330 needs to be smaller than the characteristic impedance of the input conductor 310 and the output conductors 320 and 321 (Z ₁ <Z ₀ ), as a result, the line width of the matching conductor 330 is increased. It is necessary to make the line width of the input conductor 310 and the output conductors 320 and 321 twice the line width. In this case, a step is generated in the line width at the connecting portion between the input conductor 310 and the matching conductor 330, and reflection loss may occur at the step.

On the other hand, in the line conductor 400 forming the branch circuit of the first embodiment, in the circuit board 150, the dielectric between the input conductor 410A and the ground electrode GND and between the output conductors 420A and 421A and the ground electrode GND. A space 450 and a space 451 are formed in the substrate 130, respectively. This space reduces the effective permittivity between the input conductors 410A and the output conductors 420A, 421A and the ground electrode GND, and increases the impedance of the input conductors 410A and the output conductors 420A, 421A. Correspondingly, the line widths of the input conductors 410A and the output conductors 420A and 421A are widened so that the impedances of the input conductors 410A and the output conductors 420A and 421A match the characteristic impedance. With such a configuration, it is possible to eliminate a step in the line width that occurs at the connecting portion between the input conductor 410A and the matching conductor 430, so that the reflection loss caused by the step can be reduced.

Next, the case where a matching circuit is formed on the lower branch side of FIG. 3 will be described. In the comparative example, the line conductor 301 forming the branch circuit includes an input conductor 310, output conductors 320 and 321 and a matching conductor 335 that functions as a matching circuit. The matching conductor 335 has a line length of λ/4, and is connected between the branch point CP and the output conductor 320 and between the branch point CP and the output conductor 321.

In this line conductors 301, since the impedance of the output terminals OUT1, OUT2 relative impedance _Z 0/2 of the branch point CP is _{Z 0,} the impedance of the matching conductor 335, _{Z 1} from the above equation (1) =√2Z ₀ . Since the impedance Z ₁ of the matching conductor 335 is larger than the impedance Z ₀ of the output conductors 320 and 321 (Z ₁ > Z ₀ ), the line width of the matching conductor 335 is narrower than the line widths of the output conductors 320 and 321. .. Therefore, a step of the line width is generated between the matching conductor 335 and the output conductors 320 and 321 and reflection loss occurs.

On the other hand, in the line conductor 401 forming the branch circuit of the first embodiment, the space 453 is formed between the matching conductor 435 and the ground electrode GND. In other words, in the line conductor 401, spaces are formed between the portion from the branch point CP to the output conductor 420 and the ground electrode GND, and between the portion from the branch point CP to the output conductor 421 and the ground electrode GND. ing. Correspondingly, the line width of the matching conductor 435 is set to be the same as that of the input conductor 410 and the output conductors 420 and 421. As a result, it is possible to eliminate a step in the line width between the matching conductor 435 and the output conductors 420 and 421, and it is possible to reduce the reflection loss generated at the step.

<In the case of 3 branches>
Next, an example in the case of a three-branch type branch circuit will be described with reference to FIG. First, a case where a matching circuit is formed on the trunk side in the upper part of FIG. 4 will be described. In the comparative example, the line conductor 500 forming the branch circuit includes an input conductor 510 having an input end IN, an output conductor 520 having an output end OUT1, an output conductor 521 having an output end OUT2, and an output conductor having an output end OUT3. It includes 522 and a matching conductor 530 that functions as a matching circuit. The matching conductor 530 has a line length of λ/4 and is connected between the branch point CP to which the output conductors 520 to 522 are connected and the input conductor 510.

If the impedance at the input conductor 510 and three output conductors 520-522 to the characteristic impedance of _{Z 0,} the impedance becomes _Z 0/3 at the branch point CP, the impedance of the matching conductor 530, the above equation (1) Therefore, Z ₁ =Z ₀ /√3 (Z ₁ <Z ₀ ). Therefore, the line width of the matching conductor 330 needs to be √3 times the line width of the input conductor 510 and the output conductors 520 to 522. In this case, a step is generated in the line width at the connecting portion between the input conductor 510 and the matching conductor 530, and reflection loss may occur at the step.

In the line conductor 600 forming the branch circuit of the first embodiment, in the circuit board 150, the dielectric substrate 130 between the input conductor 610A and the ground electrode GND and between the output conductors 620A to 622A and the ground electrode GND. In, space 650 and space 651 are formed, respectively. As a result, the effective permittivity between the input conductor 610A and the output conductors 620A to 622A and the ground electrode GND decreases, and the impedance of the input conductor 610A and the output conductors 620A to 622A increases. Correspondingly, the line widths of the input conductors 610A and the output conductors 620A to 622A are widened so that the impedances of the input conductors 610A and the output conductors 620A to 622A match the characteristic impedance. With such a configuration, it is possible to eliminate a step in the line width that occurs at the connecting portion between the input conductor 610A and the matching conductor 630, so that the reflection loss caused by the step can be reduced.

Next, the case where a matching circuit is formed on the lower branch side of FIG. 4 will be described. In the comparative example, the line conductor 501 forming a branch circuit includes an input conductor 510, output conductors 520 to 522, and a matching conductor 535 that functions as a matching circuit. The matching conductor 535 has a line length of λ / 4, and is connected between the branch point CP and the output conductor 520, between the branch point CP and the output conductor 521, and between the branch point CP and the output conductor 522. ing.

In this line conductors 501, since the impedance of the output terminals OUT1 ~ OUT3 relative impedance _Z 0/3 of the branch point CP is _{Z 0,} the impedance of the matching conductor 535, _{Z 1} from the above equation (1) =√3Z ₀ . Since the impedance Z ₁ of the matching conductor 535 is larger than the impedance Z ₀ of the output conductors 520 to 522 (Z ₁ > Z ₀ ), the line width of the matching conductor 535 is narrower than each line width of the output conductors 520 to 522. .. Therefore, a step of the line width is generated between the matching conductor 535 and the output conductors 520 to 522, which causes a reflection loss.

On the other hand, in the line conductor 601 forming the branch circuit of the first embodiment, the space 652 is formed between the matching conductor 635A and the ground electrode GND, and the line width of the matching conductor 635A is correspondingly formed. Have the same line width as the input conductor 610 and the output conductors 620 to 622. As a result, it is possible to eliminate the step of the line width at the connecting portion between the matching conductor 635A and the output conductors 620 to 622, and it is possible to reduce the reflection loss generated at the step.

FIG. 5 is a diagram showing an example of a perspective view of a circuit board in which a two-branch type branch circuit having a matching conductor on the trunk side is formed, which is shown in the upper part of FIG. FIG. 5 (a) in the upper row shows the circuit board 150 # on which the line conductor 300 of the comparative example is formed, and FIG. 5 (b) in the lower row shows the line conductor 400 of the first embodiment. The circuit board 150 is shown. Note that in FIG. 5, the ground electrode GND and the dielectric substrate 130 on the front surface side are transparently drawn for ease of description.

With reference to FIG. 5A, the branch circuit is formed by the line conductors 300 arranged in the inner layer of the dielectric substrate 130, as shown in FIG. The line conductor 300 has a substantially T-shape. The input end IN of the input conductor 310 functions as an input port to which an external transmission line is connected. A matching conductor 330 is connected to the other end of the input conductor 310. The output conductors 320 and 321 are connected to the other end of the matching conductor 330 (that is, the branch point CP).

A plurality of vias 180 are formed around the line conductor 300 along each conductor of the line conductor 300. The via 180 is connected to the ground electrode GND formed on the upper surface and the lower surface of the circuit board 150 #. The plurality of vias 180 function as a shielding wall inside the dielectric substrate 130 for suppressing electromagnetic coupling with other wiring patterns (not shown).

As shown in FIG. 5A, in the circuit board 150 # of the comparative example, the dielectric constant of the dielectric substrate 130 is substantially uniform, and the line widths of the matching conductor 330 are the input conductor 310 and the output conductor 320, It is wider than the line width of 321.

On the other hand, in the circuit board 150 of the first embodiment shown in FIG. 5 (b), the spaces 450,451 (FIG. 5 (FIG. 5)) are provided between the portion of the line conductor 400 excluding the matching conductor 430 and the ground electrode GND. The broken line portion) of b) is formed. The line widths of the input conductors 410A and the output conductors 420A and 421A corresponding to the input conductors 310 and the output conductors 320 and 321 are the same as those of the matching conductor 430.

FIG. 6 is a diagram for comparing the insertion loss of the circuit board on which the two-branch type branch circuit shown in FIG. 5 is formed. In FIG. 6, the horizontal axis represents frequency and the vertical axis represents insertion loss. The solid line LN10 in FIG. 6 shows the insertion loss in the case of the circuit board 150 of the first embodiment, and the broken line LN11 shows the insertion loss in the case of the circuit board 150 # of the comparative example.

As shown in FIG. 6, it can be seen that the insertion loss of the circuit board 150 of the first embodiment is improved over the entire frequency range as compared with the insertion loss of the circuit board 150 # of the comparative example. In other words, the frequency bandwidth capable of realizing the predetermined insertion loss is expanded.

As described above, in a circuit board in which a branch circuit for branching a high-frequency signal is formed, a dielectric substrate between a portion of the line conductor forming the branch circuit having a relatively narrow line width and a ground electrode A space is formed to reduce the effective dielectric constant, and the line width of the portion forming the space is widened so that the line width is the same over the entire line conductor. As a result, it is possible to prevent reflection of high-frequency signals caused by a step in the line width, so that impedance matching and loss can be reduced.

When a common high-frequency signal is branched into four antenna elements as shown in FIG. 1, a two-branch type branch circuit is further formed at each output end of the above-mentioned two-branch type branch circuit. Alternatively, the bi-branch type branch circuit may be formed at the output end of any one of the above-mentioned two-branch type branch circuits. Alternatively, although not shown in the figure, the high frequency signal may be branched from one input conductor to four output conductors.

Further, in the first embodiment, an example in which the effective dielectric constant is lowered by forming a space in the dielectric layer has been described, but the portion where the space is formed is more than the dielectric of another portion. Also, a dielectric having a low dielectric constant may be arranged.

(Modification: Output signal phase adjustment)
In the above-described circuit board of the first embodiment, the description has been made on the assumption that the line lengths of the output conductors from the branch point of the branch circuit to each output end are the same.

However, when mounting the circuit board in an actual device, it may be necessary to make the line length of the output conductor different. In the above example, since the portions of each output conductor are set to the same effective dielectric constant, the wavelengths of the high frequency signals propagating through each output conductor are basically the same. In that case, if the line length (physical length) of the output conductor is different, the wave number of the high frequency signal propagating through each output conductor is different, so that the phase of the high frequency signal at the output end is different. Then, the directivity and efficiency of the array antenna as a whole may be deteriorated.

Therefore, in the modified example, for the output conductor whose line length is relatively long, a space is newly formed between the output conductor and the ground electrode, or the height of the formed space is made higher than that of other space portions. As a result, a configuration is adopted in which the effective permittivity of the output conductor portion is further reduced. As a result, the wavelength of the high-frequency signal propagating through the output conductor, which has a relatively long line length, can be lengthened. Therefore, even if the line lengths of the output conductors are different, the phases of the high-frequency signals at the output ends can be matched by appropriately adjusting the effective permittivity for each output conductor.

7 and 8 are diagrams for explaining the first example and the second example of the branch circuit when the phase adjustment of the output signal is performed, respectively. The circuit board shown in FIGS. 7 and 8 has the line length D2 of the output conductor that transmits a high frequency signal to the output terminals OUT1 and OUT2 in the circuit board in which the three-branch type branch circuit described in FIG. 4 is formed. This corresponds to a configuration in which the line length D1 of the output conductor that transmits a high frequency signal to the output end OUT3 is longer than D1 (D2> D1). FIG. 7 is an example when a matching conductor is formed on the trunk side, and FIG. 8 is an example when a matching conductor is formed on the branch side.

With reference to FIG. 7, FIG. 7A is a comparative example in the case where the effective dielectric constant of the dielectric substrate is uniform. In the line conductor 500A of this comparative example, the line width of the matching conductor 530 is wider than the line widths of the input conductor 510 and the output conductors 522, 525, 526. In the case of FIG. 7A, since the effective dielectric constant is uniform and the wavelength of the high-frequency signal propagating through each output conductor is the same, the output of the output conductors 525 and 526 having a relatively long line length The phase of the high frequency signal at the ends OUT1 and OUT2 is different from the phase of the high frequency signal at the output end OUT3 of the output conductor 522 having a relatively short line length.

In the line conductor 600A of FIG. 7B, as described in the first embodiment, the spaces 650 and 651 are formed between the input conductors 610A and the output conductors 622A, 625A and 626A and the ground electrode GND. As a result, the line widths of the input conductor 610A and the output conductors 622A, 625A, and 626A are set to be the same as the line width of the matching conductor 630. However, in the line conductor 600A, since the effective dielectric constant for each output conductor is the same, the reflection loss due to the step in the line width is reduced, but the phase of the high frequency signal at the output ends OUT1 and OUT2 and the output end are still present. It remains out of phase with the high frequency signal at OUT3.

In the line conductor 600B according to the modification shown in FIG. 7 (c), the dimension of the space 655,656 formed corresponding to the output conductors 625B and 626B having a relatively long line length in the height direction is , It is made higher than the height dimension of the spaces 650A and 651A formed corresponding to the input conductor 610A and the output conductor 627A. As a result, the effective dielectric constant of the output conductors 625B and 626B is further smaller than the effective dielectric constant of the output conductors 627A. It will be longer than the wavelength of the signal. Therefore, by appropriately setting the dimensions of the spaces 650A and 651A in the height direction, the phase of the high frequency signal at the output ends OUT1 and OUT2 can be matched with the phase of the high frequency signal at the output ends OUT3. Further, in this way, even if the lengths of the output conductors are different, the phases of the high frequency signals can be matched, and it is not necessary to unify the lengths of the output conductors for phase adjustment, so that it is not possible in the circuit board. It is possible to prevent the arrangement of necessary wiring patterns and contribute to the miniaturization of the circuit board.

In the line conductor 600B in FIG. 7 (c), the output conductor 625B, since the effective dielectric constant is reduced for 626B, the impedance at the output end OUT1, OUT2 becomes greater than the characteristic impedance _{Z 0.} Therefore, in order to the impedance at the output terminals OUT1, OUT2 and characteristic impedance Z _0, the output conductor 625B, the line width of 626B and wider than the line conductor of the other part, necessary to lower the impedance It becomes. If the line width is changed in order to reduce the impedance, a step is generated in the line width at the connection portion with the output conductors 625B and 626B, and a slight reflection loss occurs in this portion. However, since the connection portion between the input conductor 610A and the matching conductor 630 and the line width before and after the branch point CP are the same line width, the reflection loss is reduced as compared with the line conductor 500A of the comparative example.

Next, the case where a high dielectric constant layer is formed on the branch side will be described. With reference to FIG. 8, FIG. 8A is a comparative example in the case where the effective dielectric constant of the dielectric substrate is uniform. In the line conductor 501A of this comparative example, the matching conductor 535 formed on the branch side is used. The line width is narrower than the line widths of the input conductor 510 and the output conductors 522,525,526. Also in this comparative example, the phase of the high frequency signal at the output terminals OUT1 and OUT2 is different from the phase of the high frequency signal at the output terminal OUT3.

In the line conductor 601A of FIG. 8B, the line width of the matching conductor 635A is increased to the input conductor 610 and the output conductor 622 by forming a space 652 between the matching conductor 635A including the branch point CP and the ground electrode GND. , 625, 626 and the same line width. However, in the line conductor 601A, although the reflection loss due to the step of the line width is reduced, the phase of the high frequency signal at the output ends OUT1 and OUT2 and the phase of the high frequency signal at the output end OUT3 remain different.

In the line conductor 601B according to the modified example shown in FIG. 8C, a space 657 is formed between the output conductors 625C and 626C and the ground electrode GND. Note that in FIG. 8C, the space 657 also includes a portion of the space 652 formed corresponding to the matching conductor 635A in FIG. 8B. Correspondingly, the line widths of the output conductors 625C and 626C are expanded.

Since the effective dielectric constant of the output conductors 625C and 626C is reduced by forming such a space 657, the wavelength of the high frequency signal propagating through the output conductors 625C and 626C propagates through the output conductor 627. It becomes longer than the wavelength of the high frequency signal. Thereby, the phase of the high frequency signal at the output ends OUT1 and OUT2 can be matched with the phase of the high frequency signal at the output ends OUT3.

7 and 8, the case of a three-branch type branch circuit has been described. However, even when two output conductors have different lengths in the two-branch type branch circuit, the configuration of the above-described modified example is used. It can be applied to adjust the phase at the output end.

[Second Embodiment]
In the first embodiment, in the line conductor forming the branch circuit, the line conductor of the portion is formed by forming a space or a low dielectric constant layer between the portion where the line width is relatively narrow and the ground electrode. The configuration has been described in which the line width is expanded and the reflection loss due to the step of the line width is reduced.

In the second embodiment, contrary to the first embodiment, the effective dielectric constant is increased by forming a high dielectric constant layer between the portion of the line conductor where the line width is relatively wide and the ground electrode. Then, a configuration will be described in which the line width of the portion is narrowed accordingly, and the reflection loss due to the step of the line width is reduced as well as the impedance matching.

FIG. 9 is a partial cross-sectional view of the circuit board 151 according to the second embodiment. With reference to FIG. 9, the circuit board 151 includes a dielectric substrate 130, a ground electrode GND, and a line conductor 160 for forming a branch circuit. The circuit board 151 is formed as a strip line like the circuit board 150 of the first embodiment.

In the circuit board 151 of FIG. 9, a high dielectric constant layer 175 having a dielectric constant higher than that of the dielectric substrate 130 is provided between a portion of the line conductor 160 having a relatively wide line width and the ground electrode GND. It is formed. The high dielectric constant layer 175 increases the effective dielectric constant of the portion where the line width is relatively wide, so that the impedance of the portion is reduced from the above equation (2). Then, by narrowing the line width of the line conductor 160 of the relevant portion, the impedance is made to match the impedance of the line conductor 160 of the other portion. In this way, by forming a high dielectric constant layer on the portion of the dielectric substrate corresponding to the line conductor having a relatively wide line width, the line width of the entire line conductor can be made into a relatively narrow line width portion. Can be matched. As a result, the reflection loss caused by the step difference in the line width can be reduced.

Next, a two-branch type branch circuit and a three-branch type branch circuit will be described with reference to FIGS. 10 and 11 as in the first embodiment.

10 and 11, a comparative example in which a branch circuit is formed on a substrate having a uniform effective dielectric constant is shown in the left column, and a branch circuit of the second embodiment is shown in the right column. .. Further, in FIGS. 10 and 11, the case where the matching circuit is formed on the trunk side is shown in the upper stage, and the case where the matching circuit is formed on the branch side is shown in the lower stage.

Since the comparative examples in FIGS. 10 and 11 are the same as the comparative examples in FIGS. 3 and 4, detailed description will not be repeated.

<In the case of 2 branches>
With reference to FIG. 10, first, a case where a matching circuit is formed on the trunk side in the upper part of FIG. 10 will be described. In the line conductor 700 forming the branch circuit of the second embodiment, the high dielectric constant layer 750 is provided between the matching conductor 730A corresponding to the matching conductor 330 having a relatively wide line width in the comparative example and the ground electrode GND. It is formed. As a result, the effective permittivity between the matching conductor 730A and the ground electrode GND increases, and the impedance of the matching conductor 730A decreases. Correspondingly, by narrowing the line width of the matching conductor 730A, the impedance of the matching conductor 730A is made to match the impedance of the comparative example. With such a configuration, it is possible to eliminate the step of the line width generated at the connecting portion between the input conductor 710 and the matching conductor 730A, and thus it is possible to reduce the reflection loss caused by the step.

Next, the case where a matching circuit is formed on the lower branch side of FIG. 10 will be described. In the line conductor 701 forming the branch circuit of the second embodiment, the input conductors 710A and the output conductors 720A and 721A corresponding to the input conductors 310 and the output conductors 320 and 321 having relatively wide line widths in the comparative example are used. High dielectric constant layers 751 to 753 are formed between the ground electrode and the GND. As a result, the effective permittivity between the input conductor 710A and the output conductors 720A and 721A and the ground electrode GND increases, and the impedance of the input conductor 710A and the output conductors 720A and 721A decreases. Correspondingly, the line widths of the input conductors 710A and the output conductors 720A and 721A are narrowed so that the impedances of the input conductors 710A and the output conductors 720A and 721A match the characteristic impedance. As a result, the step of the line width between the matching conductor 735 and the output conductors 720A and 721A can be eliminated, and the reflection loss generated at the step can be reduced.

<In the case of 3 branches>
An example in the case of a three-branch type branch circuit will be described with reference to FIG. When a matching circuit is formed on the trunk side of the upper stage of FIG. 11, the line conductor 800 forming the branch circuit of the second embodiment is a line in a comparative example as in the case of the two-branch type branch circuit of FIG. A high dielectric constant layer 850 is formed between the matching conductor 830A corresponding to the matching conductor 530 having a relatively wide width and the ground electrode GND. As a result, the effective dielectric constant between the matching conductor 830A and the ground electrode GND increases, and the impedance of the matching conductor 830A decreases. Correspondingly, the impedance of the matching conductor 830A is made to match the impedance of the comparative example by narrowing the line width of the matching conductor 830A. With such a configuration, it is possible to eliminate a step in the line width that occurs at the connecting portion between the input conductor 810 and the matching conductor 830A, so that the reflection loss caused by the step can be reduced.

Next, a case where a matching circuit is formed on the lower branch side of FIG. 11 will be described. In the line conductor 801 forming the branch circuit of the second embodiment, the input conductors 810A and the output conductors 820A to 822A corresponding to the input conductors 510 and the output conductors 520 to 522 having a relatively wide line width in the comparative example are used. High dielectric constant layers 851 to 854 are formed between the ground electrode and GND. As a result, the effective permittivity between the input conductor 810A and the output conductors 820A to 822A and the ground electrode GND increases, and the impedance of the input conductor 810A and the output conductors 820A to 822A decreases. Correspondingly, the line widths of the input conductors 810A and the output conductors 820A to 822A are narrowed so that the impedances of the input conductors 810A and the output conductors 820A to 822A match the characteristic impedance. As a result, the step of the line width between the matching conductor 835 and the output conductors 820A to 822A can be eliminated, and the reflection loss generated at the step can be reduced.

FIG. 12 is a diagram showing an example of a perspective view of a circuit board 151 in which a two-branch type branch circuit having a matching conductor on the trunk side is formed, which is shown in the upper part of FIG. FIG. 12 (a) in the upper row shows the circuit board 151 # on which the line conductor 300 of the comparative example is formed, and FIG. 12 (b) in the lower row shows the line conductor 700 of the second embodiment. The circuit board 151 is shown. Note that in FIG. 12, the ground electrode GND on the front surface side and the dielectric substrate 130 are transparently drawn for ease of description.

Referring to FIG. 12A, the branch circuit is formed by the line conductor 300 arranged in a layer inside the dielectric substrate 130, as shown in FIG. The line conductor 300 has a substantially T-shape. The input end IN of the input conductor 310 functions as an input port to which an external transmission line is connected. A matching conductor 330 is connected to the other end of the input conductor 310. The output conductors 320 and 321 are connected to the other end of the matching conductor 330 (that is, the branch point CP).

Around the line conductor 300, a plurality of vias 180 functioning as shielding walls are formed along each conductor of the line conductor 300.

As shown in FIG. 12A, in the circuit board 151 # of the comparative example, the dielectric constant of the dielectric substrate 130 is substantially uniform, and the line widths of the matching conductor 330 are the input conductor 310 and the output conductor 320, It is wider than the line width of 321.

On the other hand, in the circuit board 151 of the second embodiment shown in FIG. 12B, the high dielectric layer 750 (FIG. 12B is formed between the matching conductor 730A portion of the line conductor 700 and the ground electrode GND). ) Is formed. The line width of the matching conductor 730A corresponding to the matching conductor 330 is the same as that of the input conductor 710 and the output conductors 720 and 721.

(Modification: Output signal phase adjustment)
A configuration for adjusting the phase of the output signal when the lengths of the output conductors are different in the circuit board according to the second embodiment will be described with reference to FIGS. 13 and 14.

In the modified example of the first embodiment, the effective dielectric constant of the output conductor having a relatively long line length is lowered by forming a space on the dielectric substrate or arranging the low dielectric constant layer to propagate the output conductor. The wavelength of the high-frequency signal to be used was lengthened, thereby matching the phases of the high-frequency signal at the output end.

As described in the second embodiment described above, as the effective permittivity of the line conductor increases, the wavelength of the high frequency signal propagating through the line conductor becomes shorter. Therefore, in the modified example of the second embodiment, a new high dielectric constant layer is arranged between the output conductor having a relatively short line length and the ground electrode, or a dielectric material using a higher dielectric constant. By arranging the layers, the wavelength of the high frequency signal propagating through the output conductor is shortened, and the phases of the high frequency signals at the respective output ends are matched.

13 and 14 are diagrams for explaining the first example and the second example of the branch circuit when the phase adjustment of the output signal is performed, respectively. The circuit board shown in FIGS. 13 and 14 has the line length D2 of the output conductor that transmits a high frequency signal to the output terminals OUT1 and OUT2 in the circuit board on which the three-branch type branch circuit described with reference to FIG. 11 is formed. This corresponds to a configuration in which the line length of the output conductor that transmits a high frequency signal to the output end OUT3 is made longer than D1 (D2>D1). 13 shows an example in which a matching conductor is formed on the trunk side, and FIG. 14 shows an example in which a matching conductor is formed on the branch side.

Note that FIGS. 13 (a) and 14 (a) correspond to FIGS. 7 (a) and 8 (a) of the modified examples of the first embodiment, and the effective dielectric constant of the dielectric substrate is uniform. Line conductors 500A and 501A which are comparative examples of the case are shown. In the line conductors 500A and 501A, the phase of the high frequency signal at the output ends OUT1 and OUT2 and the phase of the high frequency signal at the output end OUT3 are different due to the difference in the line length of the output conductor.

In the line conductor 800A of FIG. 13B, as described in the second embodiment, by forming the high dielectric constant layer 850 between the matching conductor 830A and the ground electrode GND, the line width of the input conductor 810 is increased. And the line width of the matching conductor 830A have the same line width. However, in the line conductor 800A, since the effective dielectric constant for each output conductor is the same, the reflection loss due to the step in the line width is reduced, but the phase of the high frequency signal at the output ends OUT1 and OUT2 and the output end are still present. It remains out of phase with the high frequency signal at OUT3.

On the other hand, in the line conductor 800B according to the modification shown in FIG. 13C, a high dielectric constant layer 850A is newly formed between the output conductor 822A having a relatively short line length and the ground electrode GND. There is. As a result, the effective permittivity of the output conductor 822A becomes larger than the effective permittivity of the output conductors 825 and 826, so that the wavelength of the high frequency signal propagating through the output conductor 822A is high. It becomes shorter than the wavelength of. Therefore, by appropriately setting the dielectric constant of the high dielectric constant layer, the phase of the high frequency signal at the output terminals OUT1 and OUT2 can be matched with the phase of the high frequency signal at the output terminal OUT3.

In the line conductor 800B in FIG. 13 (c), since the effective dielectric constant of the output conductor 822A is increased, the impedance at the output terminal OUT3 is smaller than the characteristic impedance _{Z 0.} Therefore, in order to set the impedance at the output end OUT3 to the characteristic impedance Z ₀ , it is necessary to make the line width of the output conductor 822A narrower than the line width of the line conductors of other parts to increase the impedance. Become. When the line width is changed, a step is generated in the line width at the connection portion between the output conductor 822A and the branch point CP, and a slight reflection loss occurs in this portion. However, the input conductor 810 and the matching conductor 830A Since the line width before and after the connecting portion and the branch point CP is the same, the reflection loss is reduced as compared with the line conductor 500A of the comparative example.

Next, referring to FIG. 14, in the line conductor 801A of FIG. 14B, the line conductors (that is, the input conductors 810A and the output conductors 822A, 825A, 826A) excluding the matching conductor 835 and the ground electrode GND are used. By forming the high dielectric constant layers 851 to 854 between them, the line widths of the input conductor 810A and the output conductors 822A, 825A, and 826A are made the same as the line width of the matching conductor 835. However, in the line conductor 801A, although the reflection loss due to the step of the line width is reduced, the phase of the high frequency signal at the output ends OUT1 and OUT2 and the phase of the high frequency signal at the output end OUT3 remain different.

In the line conductor 801B according to the modification shown in FIG. 14 (c), between the output conductor 822B having a relatively short line length and the ground electrode GND, and between the output conductors 825A and 826A and the ground electrode GND. A high dielectric constant layer 853A having a higher dielectric constant than the high dielectric constant layers 851 and 852 to be formed is formed. With such a configuration, the effective permittivity of the output conductor 822B becomes large, so that the wavelength of the high frequency signal propagating through the output conductor 822B becomes shorter than the wavelength of the high frequency signal propagating through the output conductors 825A and 826A. .. Thereby, the phase of the high frequency signal at the output ends OUT1 and OUT2 can be matched with the phase of the high frequency signal at the output ends OUT3.

In addition, in FIGS. 13 and 14, the case of the three-branch type branch circuit has been described, but even when the lengths of the two output conductors are different in the two-branch type branch circuit, the configuration of the above modified example is configured. It can be applied to adjust the phase at the output end.

In the above description, the case where the matching conductor has a line length of λ/4 has been described, but the matching conductor has a line length of {(2n+1) such as 3λ/4, 5λ/4, etc. The length may be /4}λ (n: natural number).

Also, in the above description, “the line width is the same” includes not only the case where the line widths are completely the same, but also the case where the line widths are substantially the same. That is, if it is within the range of variation in dimensional accuracy in manufacturing (for example, within ±10%), it can be regarded as “substantially the same”.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present disclosure is shown not by the above description of the embodiments but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

10 communication device, 100 antenna module, 110 RFIC, 111A to 111D, 113A to 113D, 117 switch, 112AR to 112DR low noise amplifier, 112AT to 112DT power amplifier, 114A to 114D attenuator, 115A to 115D phase shifter, 116 signal synthesis /Demultiplexer, 118 mixer, 119 amplifier circuit, 120 antenna device, 121 antenna element, 130 dielectric substrate, 150, 150A to 150D, 150#, 151, 151# circuit board, 160, 300, 301, 400, 401 , 500, 500A, 501, 501A, 600, 600A, 600B, 601, 601A, 601B, 700, 701, 800, 800A, 800B, 801, 801A, 801B line conductors, 170, 450, 451, 453, 650, 650A , 651, 651A, 652, 655, 656, 657 space, 175, 750, 751, 753, 850, 850A, 851 to 854, 853A high dielectric constant layer, 180 via, 200 BBIC, 310, 410, 410A, 510, 610,610A, 710,710A, 810,810A Input conductor, 320,321,420,420A,421,421A,520,521,522,525,526,620,620A,622,622A,625,625A,625B, 625C, 626,626A, 626B, 626C, 627, 627A, 720, 720A, 721,721A, 820A, 822A, 822B, 825,825A, 926,826A Output conductor, 330,335,430,435,530,535 630, 635, 635A, 730A, 735, 830A, 835 Matching conductor, CP branch point, GND ground electrode, IN input end, OUT1 to OUT3 output end.

Claims (16)

A circuit board on which a branch circuit for branching a high-frequency signal is formed.
Dielectric substrate and
A ground electrode disposed on the dielectric substrate,
A line conductor arranged to face the ground electrode and disposed on the dielectric substrate and configured to transmit the high frequency signal;
The line conductor
A first conductor to which the high frequency signal is input;
A second conductor and a third conductor for branching and outputting the high-frequency signal input to the first conductor;
Including a first conductor and a matching conductor connected between the second conductor and the third conductor,
The line width before and after the branch point in the line conductor is equal,
A circuit board, wherein an effective permittivity between the matching conductor and the ground electrode is different from an effective permittivity between the first to third conductors and the ground electrode. The circuit board according to claim 1, wherein the line length of the matching conductor is set to λ/4, where λ is a wavelength of the high-frequency signal. The matching conductor is connected between a branch point in the line conductor and the first conductor,
The circuit board according to claim 1 or 2, wherein the effective permittivity between the matching conductor and the ground electrode is larger than the effective permittivity between the first to third conductors and the ground electrode. The circuit board according to claim 3, wherein in the dielectric substrate, a space is formed between the first to third conductors and the ground electrode. In the dielectric substrate, a dielectric having a dielectric constant lower than that of the dielectric between the matching conductor and the ground electrode is arranged between the first to third conductors and the ground electrode. The circuit board according to claim 3. In the dielectric substrate, a dielectric having a higher dielectric constant than the dielectric between the first to third conductors and the ground electrode is arranged between the matching conductor and the ground electrode. The circuit board according to claim 3. The matching conductor is connected between a branch point in the line conductor and the second conductor and the third conductor,
The circuit board according to claim 1 or 2, wherein the effective permittivity between the matching conductor and the ground electrode is smaller than the effective permittivity between the first to third conductors and the ground electrode. The circuit board according to claim 7, wherein in the dielectric board, a space is formed between the matching conductor and the ground electrode. In the dielectric substrate, a dielectric having a dielectric constant lower than that of the dielectric between the first to third conductors and the ground electrode is arranged between the matching conductor and the ground electrode. The circuit board according to claim 7. In the dielectric substrate, a dielectric having a higher dielectric constant than the dielectric between the matching conductor and the ground electrode is arranged between the first to third conductors and the ground electrode. , The circuit board according to claim 7. The line length of the second conductor is equal to the line length of the third conductor,
The line width of the second conductor is equal to the line width of the third conductor.
The circuit board according to any one of claims 1 to 10, wherein the effective permittivity between the second conductor and the ground electrode is equal to the effective permittivity between the third conductor and the ground electrode. .. The line length of the second conductor is longer than the line length of the third conductor.
The second conductor includes a first portion having a wider line width than the third conductor.
The circuit according to any one of claims 1 to 10, wherein the effective permittivity between the first portion and the ground electrode is smaller than the effective permittivity between the third conductor and the ground electrode. substrate. The line length of the second conductor is longer than the line length of the third conductor.
The third conductor includes a second portion having a narrower line width than the second conductor.
The circuit according to any one of claims 1 to 10, wherein the effective permittivity between the second portion and the ground electrode is larger than the effective permittivity between the second conductor and the ground electrode. substrate. With multiple radiating elements
An antenna module comprising the circuit board according to any one of claims 1 to 13. The antenna module according to claim 14, further comprising a power supply circuit that supplies the high-frequency signal to the plurality of radiating elements via the circuit board. A circuit board on which a branch circuit for branching a high-frequency signal is formed.
Dielectric substrate and
A ground electrode disposed on the dielectric substrate,
A line conductor arranged to face the ground electrode and disposed on the dielectric substrate and configured to transmit the high frequency signal;
The line conductor
A first conductor to which the high frequency signal is input;
A second conductor and a third conductor for branching and outputting the high-frequency signal input to the first conductor,
The line width before and after the branch point in the line conductor is equal,
When the circuit board is viewed in a plan view, the portion of the line conductor from the branch point to the second conductor and the ground electrode, and the portion from the branch point to the third conductor and the ground electrode A circuit board that has a space formed between it and.

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