JP6914471B2 - Signal transmission circuit - Google Patents

Description

The present invention relates to a signal transmission circuit.

Reducing the electromagnetic noise radiated from an electronic device and strengthening the electromagnetic noise immunity of the electric circuit of the electronic device are collectively referred to as electromagnetic compatibility (hereinafter referred to as EMC). Is called. Since the signal transmission circuit can be a noise source of electromagnetic noise and is also affected by electromagnetic noise from the outside, it is necessary to take EMC measures.

As a structure used for EMC countermeasures, an electromagnetic band gap (hereinafter referred to as EBG) structure is known. For example, Patent Document 1 discloses a structure that functions as an EBG structure by periodically arranging a plurality of unit cells each having the same specific conductor pattern.

International Publication No. 2011/070763

Similar to the structure disclosed in Patent Document 1, the conventional EBG structure has a structure in which a specific shape is spatially and periodically arranged (hereinafter, referred to as a spatial periodic structure). In order to enhance the blocking ability of electromagnetic noise by using this conventional EBG structure, it is necessary to increase the number of unit cells to be arranged. Increasing the number of unit cells means that the area occupied by the EBG structure increases. Therefore, for example, when a signal transmission circuit is formed on a substrate having a limited area, it is difficult to arrange a conventional EBG structure on the substrate and take EMC countermeasures.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to apply EMC countermeasures to a signal transmission circuit by using an EBG structure that does not require a spatial periodic structure.

The signal transmission circuit according to the present invention is a signal transmission circuit including a band rejection filter and an electromagnetic band gap structure, and includes a signal path for transmitting a functional signal from a transmission side terminal to a reception side terminal. A bandliger implemented between the return path of the signal path, the ground for designing the electromagnetic band gap structure, the reference ground which is the reference potential of the entire signal transmission circuit, and the ground for designing the signal path and the electromagnetic band gap structure. It is provided with a signal filter and an electromagnetic bandgap structure that is electrically connected to the return path and is mounted between a ground for designing an electromagnetic bandgap structure and a reference ground.

According to the present invention, an EMC countermeasure can be applied to a signal transmission circuit by using an EBG structure that does not require a spatial periodic structure.

FIG. 1A is a diagram showing a circuit block on which an EBG structure is mounted. FIG. 1B is a diagram showing a frequency characteristic curve of a circuit block on which an EBG structure is mounted. FIG. 2A is a diagram showing a circuit block on which a band rejection filter (hereinafter referred to as BRF) is mounted. FIG. 2B is a diagram showing a frequency characteristic curve of a circuit block on which BRF is mounted. It is a figure which showed the signal transmission circuit which concerns on Embodiment 1. FIG. It is a figure which showed the whole structure of the specific example of the signal transmission circuit which concerns on Embodiment 1. FIG. It is an enlarged view of a signal path and a return path. It is an enlarged view of the EBG structure. It is a top view of the transmitting side terminal and the receiving side terminal. It is a top view of the 1st layer in a signal transmission circuit. It is a top view of the 2nd layer in a signal transmission circuit. It is a top view of the 3rd layer in a signal transmission circuit. It is a top view of the 4th layer in a signal transmission circuit. It is a top view of the 5th layer in a signal transmission circuit. It is a figure which showed the contrast of the frequency characteristic curve. It is a figure which showed the state which the ground for the EBG structure is also used as the return path of the path for transmitting another kind of functional signal. It is an enlarged view of the main part of the signal transmission circuit provided with the ground plane.

Hereinafter, in order to explain the present invention in more detail, a mode for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1.
The signal transmission circuit according to the first embodiment is applied to a small electronic device having a limited substrate area, such as an in-vehicle navigation device or an in-vehicle audio device. This electronic device operates by flowing a functional signal in a signal transmission circuit. The functional signal flowing in the signal transmission circuit is a signal for operating an electronic device. Further, the signal transmission circuit has an EBG structure 21 and a BRF 22 which will be described later as a measure against EMC.

First, referring to Akira Shida, "Transistor Technology SPECIAL", CQ Publishing Co., Ltd., October 1, 2014, No128, Chapter 3, Fig. 1-1 (hereinafter referred to as "references"), electromagnetic waves of electric current. I will explain using theory.

In the cited document, it is assumed that a high-frequency current and an electromagnetic wave flow normally and stably inside the dielectric of the conductor and the substrate.

The circuit shown in the cited document includes a signal line SIG, a microstrip line MSL, a switch SW1, a power supply V, and a resistor R. The signal line SIG sends a signal. The microstrip line MSL serves as a reference potential for the signal. The switch SW1 is for generating a signal.

As shown in the cited document, at the moment when the switch SW1 is closed, the naturally scattered positive charges move to the vicinity of the switch SW1 and the negative charges move to the microstrip line MSL directly below. In this description, it is assumed that the switch SW1 is closed only for a moment and opened immediately.

As shown in the cited document, the positive charge is on the side of the load (not shown) of the signal line SIG, while retaining the high frequency component generated at the moment when the switch SW1 is closed, even when the switch SW1 is opened. Continue to move to the right side of). Even when the switch SW1 is opened, the negative charge moves to the side of the load (on the right side of the figure) of the microstrip line MSL while retaining the high-frequency component generated at the moment when the switch SW1 is closed. .. That is, in the state of the circuit shown in the cited document, the same high frequency component as the high frequency component held by the positive charge also exists in the negative charge.

The state of the circuit shown in the cited document can also be explained by using Coulomb's law. A Coulomb force, which is a powerful attractive force, acts between the positive charge and the corresponding negative charge. For example, if a positive charge starts a motion including vibration at a certain time, the motion is transmitted to a negative charge as well. Further, since the positive charges existing in the signal line SIG have strong repulsive forces with each other, the high frequency components held by them are propagated to the positive charges existing in the vicinity thereof. Then, the high-frequency component propagated to the positive charge propagates to the negative charge corresponding to the positive charge, and finally propagates to the load side of the microstrip line MSL.

In the circuit shown in the cited document, when both the positive charge and the negative charge generated on the transmitting side propagate the same high frequency component to the load side at the same time, the high frequency component is propagated. That is, assuming a state in which only the high-frequency component held by one of the electric charges is propagated to the load side, that state is not electromagnetically established. In other words, if the propagation of the motion of either the positive charge or the negative charge is blocked, the high frequency component is blocked.

Next, the concept of the signal transmission circuit according to the first embodiment will be described with reference to FIGS. 1 to 3 based on the principle of the electromagnetic wave theory.

FIG. 1A is a diagram showing a circuit block (hereinafter, referred to as an EBG block) on which an EBG structure is mounted. FIG. 1B is a diagram showing a frequency characteristic curve of the EBG block.

The circuit block shown in FIG. 1A includes a path A, a path B, a resistor R1, and an EBG structure 21. Path A is a reference ground that serves as a potential reference for path B. Pass B is a ground for EBG structural design. The resistor R1 indicates that the impedance between the path A and the path B is high impedance in terms of distribution constant.

The EBG structure 21 does not have a periodic structure. This EBG structure 21 is mainly implemented between the path A and the path B.

The frequency characteristic curve in the path B is the curve shown in FIG. 1B, assuming that the path A is an ideal reference ground. The EBG structure 21 blocks electromagnetic noise corresponding to a frequency band having a frequency of f1 or higher. The range of the shaded area shown in FIG. 1B is the frequency band in which the functional design circuit described later in FIG. 3A operates. As is clear from FIG. 1B, the EBG structure 21 is not included in the functional design circuit.

FIG. 2A is a diagram showing a circuit block on which a BRF is mounted (hereinafter referred to as a BRF block) and a circuit block constituting a functional design circuit (hereinafter referred to as a functional design circuit block). FIG. 2B is a diagram showing a frequency characteristic curve of the BRF block.

The circuit block shown in FIG. 2A includes a pass B, a pass C, a pass D, a resistor R2, a BRF 22, a transmitting side terminal 31, and a receiving side terminal 32. Path C is a signal path. Path D is a return path. Paths C and D are paths for transmitting a functional signal.

The resistor R2 indicates that the impedance between the path B and the path D is high impedance in terms of distribution constant. One end of the path C and one end of the path D are connected via a transmission side terminal 31. The other end of the path C and the other end of the path D are connected via the receiving terminal 32. Therefore, the functional signal input from the transmitting side terminal 31 is transmitted in the signal transmission circuit, and finally is transmitted from the receiving side terminal 32 to an external device (not shown).

The BRF 22 is implemented between the path B and the path C. The BRF block is composed of pass B, pass C, and BRF 22. In the BRF block, pass B serves as a potential reference for pass C.

The frequency characteristic curve in the path C is the curve shown in FIG. 2B, assuming that the path B is an ideal reference ground. The BRF 22 blocks electromagnetic noise corresponding to the frequency band f2.

The functional design circuit block is composed of a path C, a path D, a transmitting side terminal 31, and a receiving side terminal 32. In other words, the path C, the path D, the transmitting side terminal 31, and the receiving side terminal 32 form a functional design circuit. The functional design circuit is a circuit that transmits a functional signal such as a clock signal. In the functional design circuit, the path D is a reference ground that serves as a potential reference for the path C. That is, the path D has a role of a ground for a functional signal. The frequency band in which the functional design circuit operates is the range of the shaded area shown in FIG. 2B. As is clear from FIG. 2B, the BRF 22 is not included in the functional design circuit.

The absolute amount of charge having a high frequency component in the frequency band blocked by the EBG structure 21 and BRF 22 is considered to be extremely small as compared with the absolute amount of charge having a high frequency component in the frequency band when not blocked. On the other hand, it is considered that the absolute amount of the charge having the high frequency component in the frequency band other than the frequency band blocked by the EBG structure 21 and the BRF 22 is the same regardless of the blocking.

FIG. 3 is a diagram showing the concept of the signal transmission circuit according to the first embodiment. The signal transmission circuit 100 shown in FIG. 3 is a circuit in which the circuit block shown in FIG. 1A and the circuit block shown in FIG. 2A are combined. In the signal transmission circuit 100 according to the first embodiment, the EBG structure 21 and the BRF 22 are used in combination for the purpose of EMC countermeasures.

The signal transmission circuit 100 according to the first embodiment has the path A, the path B, the path C, the path D, the EBG structure 21, the BRF 22, the transmitting side terminal 31 and the receiving side terminal 32 shown in FIGS. 1A and 2A. In addition, the resistor R3 and the resistor R4 are provided.

The resistor R3 indicates that the impedance between the path A and the path D is high impedance in terms of distribution constant. The resistor R4 indicates that the impedance between the path B and the path D is high impedance in terms of distribution constant. The resistors R3 and R4 also indicate that the impedance between the path A and the path B is high impedance in terms of distribution constant.

In the signal transmission circuit 100 according to the first embodiment, the path A is a reference ground that serves as a potential reference for the entire signal transmission circuit 100. Pass B is a ground for BRF structural design, which is a potential reference for BRF22. Path C is a signal path. The path D is a functional signal ground that serves as a potential reference for the path C in the functional design circuit, and is a return path dedicated to the signal path.

When evaluating EMC countermeasures in a device, it is necessary to evaluate the electromagnetic noise propagating in the circuit and the electromagnetic noise radiated from the circuit. The electromagnetic noise propagating in the circuit is measured, for example, between the power supply terminal of the device to be evaluated and the reference ground. The electromagnetic noise radiated from the circuit is measured between the infinity antenna and the infinity ground.

Therefore, also in the signal transmission circuit 100 according to the first embodiment, the measurement point E for measuring the electromagnetic noise propagating in the circuit and the measurement point F for measuring the electromagnetic noise radiated from the circuit are set. Has been done. The measurement point E is set between the path A and the receiving terminal 32. The measurement point F is set at one point in the space between the infinity antenna and the infinity ground G.

Note that FIG. 3 shows the frequency characteristic curve in the path B shown in FIG. 1B and the frequency characteristic curve in the path C shown in FIG. 2B, and the frequency characteristic curve at the measurement point E and the measurement point. The frequency characteristic curve in F is also shown.

The reference ground of the measurement point E is a reference ground equivalent to the path A. The charge contained in the path A has a flat frequency characteristic over the entire band. The frequency characteristic curve at the measurement point E is the frequency characteristic at the receiving terminal 32 with reference to the reference ground equivalent to the path A.

The charge measured at the measurement point E is affected by the frequency characteristics of the charge contained in the path C. Further, the path B is the reference potential of the BRF 22 as a distributed constant circuit. Therefore, the charge measured at the measurement point E is affected by the frequency characteristics of the charge contained in the path B.

Further, path A is a reference potential of the EBG block as a distributed constant circuit, path B is a reference potential of BRF22 as a distributed constant circuit, and path D is a functional design circuit block as a lumped constant circuit. It is a reference potential, and the connection points between the blocks are far from the measurement point E. Therefore, for signals in the high frequency region, each of the paths A, B, and D and the measurement point E have high impedance. That is, it can be said that the signal transmission circuit 100 shown in FIG. 3 is composed of a plurality of circuit blocks that are electrically independent of each other. Therefore, the frequency characteristic curve of the charge output between the measurement point E and the path A is the sum of the frequency characteristic curve in the path B and the frequency characteristic curve in the path C, and is shown in FIG. It can be considered to correspond to the frequency characteristic curve at the measurement point E.

The reference ground of the measurement point F is the infinity ground G.

The conventional EBG structure has a spatial periodic structure. In the EMC countermeasure using the conventional EBG structure, the EBG structure is used in such a manner that it is arranged so as to surround the electromagnetic noise source. In this aspect, since the EBG structure is arranged at a position spatially separated from the electromagnetic noise source, it can be said that the EBG structure indirectly suppresses the electromagnetic noise. In order to enhance the blocking ability of electromagnetic noise by the conventional EBG structure used in such an embodiment, it is necessary to increase the number of cycles. Therefore, the conventional EBG structure used for EMC countermeasures is difficult to miniaturize, and cannot be arranged on a substrate having a limited area, for example. Further, the frequency band cut off by the conventional EBG structure is, for example, a band of 2 GHz or more, and it is difficult to cut off a low frequency band of about several hundred MHz.

On the other hand, in the signal transmission circuit 100 according to the first embodiment, the EBG structure 21 directly connected to the path D through which the functional signal serving as the electromagnetic noise source passes and the BRF 22 controlling the several hundred MHz band are provided. , Are electrically independent of each other. In the signal transmission circuit 100 according to the first embodiment, the EBG structure 21 and the BRF 22 are used in combination in the embodiment shown in FIG. 3, so that the EBG structure 21 has the electrical periodicity required to function as the EBG structure. BRF22 is partly responsible. Therefore, the EBG structure 21 of the signal transmission circuit 100 according to the first embodiment does not require a spatial periodic structure. Further, the BRF 22 can be more specifically configured as a distributed constant circuit.

As described above, in the signal transmission circuit 100 according to the first embodiment, the paths C and D for functional design, the EBG structure 21 which does not require a spatial periodic structure, and the BRF 22 are used in combination, so that the size is reduced. Is possible. Therefore, the signal transmission circuit can be applied to a small electronic device having a limited substrate area, such as an in-vehicle navigation device and an in-vehicle audio device.

Further, in the signal transmission circuit 100 according to the first embodiment, since the EBG structure 21 and the BRF 22 are used in combination, it is possible to block electromagnetic noise in a plurality of frequency bands including a low frequency band. In general, for example, when two filter circuits having different cutoff frequencies are used, if the two filter circuits are simply connected, an anti-resonance state may occur and desired characteristics may not be obtained. Therefore, usually, an isolation amplifier or the like is placed between the two filter circuits to separate the two filter circuits. On the other hand, in the signal transmission circuit 100 according to the first embodiment, the EBG block and the BRF block can be electrically independent of each other according to the embodiment shown in FIG. Therefore, in the signal transmission circuit 100 according to the first embodiment, the filter function of the EBG structure 21 and the filter function of the BRF 22 are not affected by each other, and the frequency characteristics of the entire signal transmission circuit 100 are the same as the frequency characteristics of both. It will be the sum.

Further, in the signal transmission circuit 100 according to the first embodiment, the EBG structure 21 is directly connected to the path D which is a signal path, and the BRF 22 can be configured as a distributed constant circuit. Therefore, the signal transmission circuit 100 according to the first embodiment does not require mounting components and can be an inexpensive circuit.

Next, the configuration when the signal transmission circuit according to the first embodiment is simulated in a three-dimensional electromagnetic field based on the principle of electromagnetic wave theory will be described with reference to FIGS. 4 to 15.

FIG. 4 is a diagram showing an overall configuration of a specific example of the signal transmission circuit 100 according to the first embodiment. FIG. 5 is an enlarged view of a signal path and a return path. FIG. 6 is an enlarged view of the EBG structure. FIG. 7 is a plan view of the transmitting side terminal and the receiving side terminal. FIG. 8 is a plan view of the first layer in the signal transmission circuit 100. FIG. 9 is a plan view of the second layer in the signal transmission circuit 100. FIG. 10 is a plan view of the third layer in the signal transmission circuit 100. FIG. 11 is a plan view of the fourth layer in the signal transmission circuit 100. FIG. 12 is a plan view of the fifth layer in the signal transmission circuit 100.

The signal transmission circuit 100 has a five-layer structure. The signal transmission circuit 100 includes a reference ground 11, a signal path 12, a return path 13, a guard pattern 14, a ground 15 for EBG structure design, a reference ground 16, a via connection line 17, an EBG structure 21, a BRF 22, and a transmission terminal 31. It includes a receiving terminal 32 and vias 41 to 52.

The reference ground 11 constitutes the first layer of the signal transmission circuit. The return path 13 and the via connection line 17 form the second layer of the signal transmission circuit. The signal path 12 and the guard pattern 14 form a third layer of the signal transmission circuit. The ground 15 for EBG structural design constitutes the fourth layer of the signal transmission circuit. The reference ground 16 constitutes the fifth layer of the signal transmission circuit. A dielectric layer (not shown) is formed between the layers adjacent to each other in the first to fifth layers. The vias 41 to 52 are arranged so as to penetrate from the first layer to the fifth layer, and electrically connect two or more layers of the first layer to the fifth layer, respectively. ..

The reference ground 11 is connected to vias 41, 42, 45, 46, 48, 50, 52 and not to vias 43, 44, 47, 49, 51.

The return path 13 is connected to the vias 48, 50, 52 and not to the vias 41-47, 49, 51. The via connection line 17 is connected to the vias 43 and 47 and not to the vias 41, 42, 44 to 46, 48 to 52.

The signal path 12 is connected to the vias 49 and 51 and not to the vias 41 to 48, 50 and 52. The guard pattern 14 is connected to the vias 48 and 52, and is not connected to the vias 41 to 47, 49 to 51.

The ground 15 for EBG structural design is connected to vias 41, 42, 44 to 46, 48, 50, 52 and not to vias 43, 47, 49, 51.

The reference ground 16 is connected to vias 41, 42, 46 to 50, 52 and not to vias 43 to 45, 51.

The transmitting side terminal 31 is connected to one end of the via 43. One end of the via 43 is an end portion of the two ends of the via 43 that is arranged on the reference ground 11 side constituting the first layer. The receiving terminal 32 is connected to one end of the via 51. One end of the via 51 is an end portion of the two ends of the via 51 that is arranged on the reference ground 11 side that constitutes the first layer.

The signal path 12 corresponds to the path C shown in FIGS. 2A and 3. The signal path 12 transmits the functional signal input to the transmitting side terminal 31 toward the receiving side terminal 32. The return path 13 is formed as a microstrip line. The return path 13 corresponds to the path D shown in FIGS. 2A and 3.

The guard pattern 14 is formed so as to surround the outer circumference of the signal path 12. The length shape of the return path 13 substantially matches the length shape of the guard pattern 14, and the return path 13 is arranged so as to cover the guard pattern 14 from the first layer side. The path route formed by the signal path 12, the return path 13, and the guard pattern 14 has a function for transmitting a functional signal, which is the original purpose of the signal transmission circuit 100.

The ground 15 for EBG structural design corresponds to the path B shown in FIGS. 1 to 3. The ground 15 for EBG structural design is formed according to the length shape of the signal path 12, the return path 13, and the guard pattern 14. As a result, the signal transmission circuit 100 can reduce the installation range of the ground 15 for EBG structural design.

The reference ground 16 corresponds to the path A shown in FIGS. 1 to 3. The reference ground 16 has the same potential as the reference ground 11.

The EBG structure 21 is provided over the ground 15, the reference ground 16, and the via 44 for the EBG structure design, and is connected to the return path 13 and the guard pattern 14. The connection position between the EBG structure 21, the return path 13 and the guard pattern 14 is set closer to the transmitting side terminal 31 than to the receiving side terminal 32, and is as close as possible to the transmitting side terminal 31. ..

Further, the EBG structure 21 has a return path connecting portion 21a, an EBG structure design ground connecting portion 21b, a reference ground connecting portion 21c, and a via connecting portion 21d.

The return path connection portion 21a constitutes a third layer of the signal transmission circuit. The return path connecting portion 21a is connected to the vias 42, 44, 45 and is not connected to the vias 41, 43, 44, 47 to 52. The return path connecting portion 21a is connected to the return path 13 and the guard pattern 14 via vias 42, 46, 48 and the reference ground 11.

The ground connection portion 21b for EBG structural design constitutes a part of the ground 15 for EBG structural design. The ground connection portion 21b for EBG structural design is connected to the vias 44 and 45, and is not connected to the vias 41 to 43, 46 to 52. The ground connecting portion 21b for EBG structural design is connected to the via connecting portion 21d via the via 44. Further, the EBG structural design ground connection portion 21b is connected to the signal path 12 and the EBG structural design ground 15 via the vias 45, 48, the reference ground 11, and the reference ground 16. The ground connection portion 21b for EBG structure design configured in this way has a role of an inductor component (coil) in the EBG structure 21.

The reference ground connection portion 21c constitutes a part of the reference ground 16. The reference ground connection portion 21c is connected to the vias 42 and 46, and is not connected to the vias 41, 43 to 45, 47 to 52.

The via connection portion 21d is arranged inside the return path connection portion 21a forming an annular shape. The via connection portion 21d is connected only to the via 44 among the vias 41 to 52. The via connecting portion 21d is connected to the ground connecting portion 21b for EBG structural design via the via 44. The via connection portion 21d configured in this way has a role of a capacitor component (capacitor) in the EBG structure 21.

The BRF 22 is composed of a signal path 12, a guard pattern 14, and a ground 15 for EBG structural design. The function of the BRF 22 in the ground 15 for the EBG structural design is carried out by a portion other than the ground connection portion 21b for the EBG structural design in the ground 15 for the EBG structural design. As a result, the ground 15 for the EBG structure design plays a part of the functions of both the EBG structure 21 and the BRF 22.

The functional signal input to the transmission side terminal 31 is transmitted to the signal path at the reference ground 16 via the via 43, the via connection line 17, and the via 47. Next, the functional signal transmitted from the signal path is transmitted to the receiving terminal 32 via the via 49, the signal path 12, and the via 51. Of the frequency components of the electric charge of the functional signal flowing in the outward path, the positive charge (negative charge) of the unnecessary frequency component is cut off in the cutoff frequency band controlled by the BRF22.

Further, the functional signal output from the receiving side terminal 32 is mainly transmitted to the return path 13 and the guard pattern 14 via the via 52. Next, the functional signal transmitted to the return path 13 and the functional signal transmitted to the guard pattern 14 are transmitted to the reference ground connection portion 21c via the via 48 and the reference ground 16. Then, the functional signal transmitted to the reference ground connection unit 21c is transmitted to the transmission side terminal 31 via the via 42. Of the frequency components of the electric charge of the functional signal flowing through the return path, the negative charge (positive charge) of the unnecessary frequency component is cut off in the cutoff frequency band controlled by the EBG structure 21.

FIG. 13 is a diagram showing a comparison of frequency characteristic curves. The solid line shown in FIG. 13 shows the frequency characteristic curve of the signal transmission circuit according to the first embodiment, and the two-dot chain line shown in FIG. 13 shows the frequency characteristic curve of the conventional electronic circuit. This conventional electronic circuit does not have a structure corresponding to the EBG structure 21. As shown in FIG. 13, the signal transmission circuit blocks electromagnetic noise in the entire frequency range as compared with the conventional electronic circuit.

FIG. 14 is a diagram showing a state in which the ground for EBG structural design is also used as a return path of a path for passing a different type of functional signal. The ground 15 for EBG structural design also serves as the return path of the path 18. The path 18 is arranged in an opening formed in the reference ground 16. This path 18 transmits a functional signal of a type different from the functional signal transmitted between the transmitting side terminal 31 and the receiving side terminal 32. When the ground 15 for EBG structural design is also used as the return path of the path 18 for transmitting another type of functional signal in this way, the signal transmission circuit 100 can improve the efficiency of layout design. When the path 18 is provided, it is desirable that the ground 15 for the EBG structural design and the path 18 have their vibration frequencies set to integral multiples of each other in order to maintain the quality of the functional signal.

FIG. 15 is an enlarged view of a main part of a signal transmission circuit provided with a ground plane. The signal transmission circuit shown in FIG. 15 includes a ground plane 15A instead of the ground 15 for EBG structural design.

The ground 15 for EBG structural design is formed according to the length and shape of the signal path 12, the return path 13, and the guard pattern 14, so that the installation range thereof is reduced. Further, the ground 15 for EBG structure design is a portion used in combination with both the EBG structure 21 and the BRF 22. The signal transmission circuit 100 can reduce the size of the EBG structure 21 and the BRF 22 by providing the ground 15 for the EBG structure design.

On the other hand, the ground plane 15A is formed in a flat plate shape. As a result, the signal transmission circuit 100 can increase the installation range of the ground plane 15A, so that the quality of the functional signal can be improved.

From the above, the signal transmission circuit 100 according to the first embodiment is a signal transmission circuit including the BRF 22 and the EBG structure 21 for transmitting a functional signal from the transmission side terminal 31 to the reception side terminal 32. The signal path 12, the return path 13 of the signal path 12, the ground 15 for EBG structure design, the reference grounds 11 and 16 which are the reference potentials of the entire signal transmission circuit 100, and the signal path 12 and the ground for EBG structure design. It includes a BRF 22 mounted between the 15 and an EBG structure 21 electrically connected to the return path 13 and mounted between the ground 15 for EBG structure design and the reference ground 16. As a result, the signal transmission circuit 100 can take EMC measures on the signal transmission circuit 100 by using the EBG structure 21 that does not require a spatial periodic structure.

Since the signal transmission circuit 100 uses the EBG structure 21 and the BRF 22 together, it is possible to block electromagnetic noise in a plurality of frequency bands including a low frequency band.

In the signal transmission circuit 100, the EBG structure 21 can be directly connected to the path D which is a signal path, and the BRF 22 can be configured as a distributed constant circuit. As a result, the signal transmission circuit 100 does not require mounting components and can be an inexpensive circuit.

In the present invention, within the scope of the invention, any combination of the embodiments, modification of any component in each embodiment, or omission of any component in each embodiment can be omitted. It is possible.

The signal transmission circuit according to the present invention can block electromagnetic noise by using the EBG structure and the BRF together in a part of the functional signal path, and is suitable for use in a signal transmission circuit or the like.

A to D paths, E, F measurement points, G infinity ground, R1 to R4 resistance, 11 reference ground, 12 signal paths, 13 return paths, 14 guard patterns, 15 grounds for EBG structural design, 15A ground planes, 16 Reference ground, 17 via connection line, 18 paths, 21 EBG structure, 21a return path connection, 21b EBG structure design ground connection, 21c reference ground connection, 21d via connection, 22 BRF, 31 transmitter terminal, 32 Receiving terminal, 41-52 vias.

Claims (8)

A signal transmission circuit having a band rejection filter and an electromagnetic bandgap structure.
A signal path for transmitting a functional signal from the transmitting terminal to the receiving terminal,
The return path of the signal path and
Ground for electromagnetic bandgap structural design and
The reference ground, which is the reference potential of the entire signal transmission circuit, and
A band rejection filter mounted between the signal path and the ground for designing the electromagnetic bandgap structure,
A signal transmission circuit comprising an electromagnetic bandgap structure electrically connected to the return path and mounted between the ground for designing the electromagnetic bandgap structure and the reference ground. The signal transmission circuit according to claim 1, wherein the electromagnetic bandgap structure does not have a spatial periodic structure. The signal transmission circuit according to claim 1, wherein the band rejection filter is configured as a distributed constant circuit. The impedance between the band rejection filter and the electromagnetic bandgap structure is high impedance in terms of distribution constant, and the band rejection filter and the electromagnetic bandgap structure are electrically independent. The signal transmission circuit according to claim 1. The signal transmission circuit according to claim 1, wherein the connection position between the electromagnetic bandgap structure and the return path is set to a position closer to the transmitting side terminal than to the receiving side terminal. The signal transmission circuit according to claim 1, wherein the ground for designing the electromagnetic bandgap structure is formed in accordance with the length shapes of the signal path and the return path. The signal transmission circuit according to claim 1, wherein the ground for designing the electromagnetic bandgap structure is formed in a flat plate shape. An electronic device comprising the signal transmission circuit according to any one of claims 1 to 7.

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