JPWO2009048095A1 - Circuit device having transmission line and printed circuit board - Google Patents

Abstract

In a circuit device having a transmission line, a circuit device that suppresses the influence of an unnecessary mode with a simple structure and suppresses deterioration of propagation characteristics is provided. The circuit device includes a conductive strip that forms a transmission line, and a conductive plane that is disposed opposite to and parallel to the conductive strip. At least a part of the outer periphery of the conductive plane is formed in a continuous uneven shape including a recess and a protrusion. Preferably, when the wavelength of the propagation mode that is not desired to be generated in the conductive plane is λ, the interval between adjacent concave portions of the concave and convex shape of the conductive plane is n / 4 times λ (n is an odd number). Regarding the length of the concave portion of the conductive plane, n / 4 times the mode wavelength when the component of λ propagates in the length direction of the concave portion (n is an odd number), or about the length of the convex portion of the conductive plane, λ Is n / 4 times (n is an odd number) of the mode wavelength in the case where the above component propagates in the length direction of the convex portion.

Description

  The present invention relates to a circuit device having a transmission line, and more particularly to a structure for suppressing unnecessary mode propagation in a strip line in a circuit device having a strip line used in a high-frequency printed circuit board or the like.

  In a circuit device having a transmission line, if the frequency of the line propagation component increases, the propagation characteristics of a desired mode may be deteriorated due to the influence of unnecessary modes. For example, when the transmission line is a microstrip line, the basic mode is a quasi-TEM (Transverse Electric and Magnetic) mode. In this case, when the propagation frequency increases, unnecessary modes other than the TEM mode such as the TE (Transverse Electric) mode and the TM (Transverse Magnetic) mode easily propagate. As a result, it is known that the propagation characteristics of the quasi-TEM mode easily deteriorate due to the electromagnetic interference of the quasi-TEM mode with those unnecessary modes.

  In relation to this, Patent Document 1 discloses that in order to reduce undue electromagnetic coupling of electromagnetic waves outside and inside a communication device in which circuit elements constituting a transmission / reception circuit are mounted in the case, A structure in which a periodic structure in which the material or mechanical shape is periodically changed is added is described.

Patent Document 2 discloses that a waveguide having a corrugated groove on the inner surface has good impedance and low loss characteristics over a wide band with respect to a pass band, and is also good with respect to a stop band. As a band rejection filter having attenuation characteristics, a corrugated structure having an appropriately designed size is described.
JP 2000-307305 A JP-A-52-24057

  However, in Patent Documents 1 and 2 described above, in a circuit device having a transmission line, a complicated structure such as a periodic structure having a specific structure or a corrugated structure is used to suppress the influence of unnecessary modes so that desired propagation characteristics do not deteriorate. It was necessary to adopt a simple structure.

  An object of the present invention is to provide a circuit device having a transmission line that solves the above-described problems, suppresses the influence of unnecessary modes with a simple structure, and hardly deteriorates desired propagation characteristics.

  In order to achieve the above object, a circuit device according to the present invention is a circuit device having a conductive strip constituting a transmission line and a conductive plane disposed in parallel and opposed to the conductive strip, wherein At least a part of the outer contour of the conductive plane is formed in a continuous uneven shape including a recess and a protrusion.

  According to the present invention, since at least a part of the outer periphery of the conductor plane has a continuous concave / convex shape including a concave portion and a convex portion, the influence of unnecessary modes is suppressed with a simple structure, and desired propagation characteristics are deteriorated. A circuit device having a difficult transmission line can be provided.

1 is an exploded perspective view showing a circuit device according to a first embodiment of the present invention. FIG. 5 is a diagram illustrating a circuit device according to a second embodiment of the present invention, in which (a) is a perspective view of a main part showing the structure of a conductor plane, and (b) is an equivalent circuit diagram of the structure shown in (a). It is a figure which shows the circuit apparatus based on the 3rd Example of this invention. It is a figure which shows the circuit apparatus which concerns on the 4th Example of this invention, (a) is a perspective view of a conductor plane, (b) is the principal part which shows the case where the recessed part of a conductor plane is not bent, and the case where a recessed part is bent It is a perspective view. It is a figure which shows the circuit apparatus based on the 5th Example of this invention. It is a figure which shows the circuit apparatus based on the 6th Example of this invention, (a) is a disassembled perspective view, (b) is a lamination | stacking sectional drawing. It is a figure which shows the circuit apparatus based on the 7th Example of this invention. It is a figure which shows the circuit apparatus based on the 8th Example of this invention, and is a principal part perspective view which shows the structure of a conductor plane, (b) is an equivalent circuit schematic of the structure shown to (a). It is a figure which shows the circuit apparatus based on the 9th Example of this invention. It is a figure which shows the circuit apparatus based on the 10th Example of this invention, Comprising: The principal part perspective view which shows the structure of a conductor plane, (b) is an equivalent circuit schematic of the structure shown to (a). It is a figure which shows the TEM mode in a microstrip line, (a) is sectional drawing of a transverse direction, (b) is sectional drawing of a transmission direction. It is a figure which shows TM0 mode in a microstrip line, (a) is sectional drawing of a transverse direction, (b) is sectional drawing of a transmission direction. It is sectional drawing of the transverse direction which shows TM0 mode in a microstrip line. It is a figure which shows TE and TM mode in a microstrip line, (a) is sectional drawing which shows the electric field component of the transverse direction of each mode, (b) is sectional drawing which shows the electric field component of the transmission direction of each mode. It is a figure explaining the effect of the circuit device which concerns on this Embodiment, (a) is a figure which shows the analysis result at the time of using a conductor plane with an uneven shape, (b) used the conductor plane without an uneven shape It is a figure which shows the electric field distribution analysis result in a case. It is a figure which shows the circuit apparatus which concerns on related technology.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Strip conductor 2 Conductor plane 3 Insulator layer 11 Strip conductor 12 Conductor plane 12a Concavity 12b Convex part 12c Short-circuit termination 13 Conductor plane 14 Strip conductor 21, 22, 23 Insulator layer 31 Circuit component 41 Strip conductor 42 Conductor plane 43 Strip conductor 44 Conductive housing or heat sink 51, 52 Insulator layer 61 Circuit component 71 Strip conductor 72 Conductor plane 72a Concavity 72b Convex portion 72c Short-circuit termination 73 Conductor plane 81 Insulator layer

Embodiments of a circuit device according to the present invention will be described below with reference to the drawings.
(Embodiment)
The present embodiment provides a circuit device having a transmission line that suppresses the influence of an unnecessary mode with a simple structure and hardly deteriorates the propagation characteristics of a desired mode. In particular, in the present embodiment, in a circuit device having a strip line, a TEM mode transmission line in which the influence of an unnecessary mode such as a TE mode or a TM mode is suppressed as a structure for suppressing unnecessary mode propagation in the strip line. A circuit device having

  Hereinafter, for the circuit device having the transmission line according to the present embodiment, refer to the circuit device having the microstrip line according to the related art shown in FIG. 16 and the propagation modes of the microstrip line shown in FIGS. While explaining.

  A printed circuit board constituting the related art circuit device shown in FIG. 16 is provided with a microstrip line including a strip conductor 111 of the first conductor layer and a conductor plane 112 of the second conductor layer as a transmission line.

  FIGS. 11 to 14 illustrate propagation modes of the microstrip line. The microstrip line has a structure in which an insulator layer 3 is sandwiched between a conductor strip 1 and a conductor plane 2 as shown in FIGS. The basic mode of the microstrip line is a quasi-TEM mode having a line section electromagnetic field distribution as shown in FIGS. 11A and 11B, and an electromagnetic field exists only in the vicinity of the strip conductor 1. In the microstrip line, when the frequency is increased, the TM0 mode having the line cross-sectional electromagnetic field distribution as shown in FIGS. 12A and 12B and the propagation become easier, and the quasi-TEM mode is converted into this unnecessary TM0 mode. It is known that the propagation characteristics of the quasi-TEM mode are likely to deteriorate. The TM0 mode is a mode when the conductor plane 2 is theoretically infinitely wide, but it is almost the same mode when the size of the conductor plane 2 is finite and sufficiently wider than the width of the strip conductor 1 as in the actual structure. Here, this is called TM0 mode for convenience. FIG. 13 shows the magnetic field distribution in the unnecessary mode when the conductor plane 2 has a finite size, and the conductor plane 2 exists so as to wrap around the conductor plane 2. Unlike the quasi-TEM mode, the unnecessary mode has an electromagnetic field over the entire conductor plane 2.

  On the other hand, as shown in FIG. 1 described later, the circuit device according to the present embodiment has a structure that suppresses the unnecessary mode without degrading the quasi-TEM mode, and the side of the conductor plane parallel to the strip conductor ( The edge) is an uneven pattern composed of a concave portion and a convex portion. In this structure, the concavo-convex recess acts as a slot line for short-circuit termination, and the depth of the concavo-convex recess is made most effective by setting it to 1/4 of the slot line wavelength corresponding to the frequency to be suppressed (described later). (See FIG. 2 (a)). This is not limited to 1/4 of the slot line wavelength, and is the same for 3/4 and 5/4. In short, the same effect can be obtained if n / 4 times (n is an odd number). In addition, the effect is most enhanced by setting the interval between adjacent concave and convex portions to ¼ of the unnecessary mode wavelength. This is not limited to ¼ of the unnecessary mode wavelength, and is the same for 3/4 and 5/4. In short, the same effect can be obtained if it is n / 4 times (n is an odd number).

  An equivalent circuit of this structure is shown in FIG. 2B to be described later. Unnecessary mode lines having a length (λu / 4) of ¼ of the unnecessary mode wavelength λu are connected in multiple stages, and a slot line is connected to the connection portion. A short-circuit termination slot line having a length (λs / 4) of ¼ of the wavelength λs is inserted.

  Since the impedance of the slot line seen from this connection part is very large, the impedance at the connection part of the unnecessary mode line becomes very large. As a result, unnecessary mode propagation is suppressed. Further, by setting the interval between the connection portions to ¼ wavelength of the unnecessary mode, an effect can be obtained regardless of the propagation direction distribution of the unnecessary mode. If the distance between the connection portions is ½ wavelength of the unnecessary mode, and if the electric field maximum (impedance maximum) position in the distribution in the propagation direction of the unnecessary mode coincides with the connection point, the unnecessary mode suppression effect is sufficiently obtained. It may not be possible. By setting the interval between the connection portions to ¼ of the unnecessary mode wavelength, it is possible to obtain an unnecessary mode suppression effect regardless of the propagation direction distribution of the unnecessary mode. This is not limited to ¼ of the unnecessary mode wavelength, and is the same for 3/4 and 5/4. In short, the same effect can be obtained if it is n / 4 times (n is an odd number).

  In order to show the effect of the above means, a three-dimensional electromagnetic field analysis (FDTD method) of the microstrip line was performed based on the presence or absence of the uneven shape of the conductor plane 2. This analysis model and the analysis result are shown in FIG. 15A (when the conductor plane 2 with uneven shape is used) and FIG. 15B (when the conductor plane 2 without uneven shape is used).

Here, as common conditions for the two analyzes based on the presence or absence of the concavo-convex shape of the conductor plane 2, the analysis region (x: 50 mm, y: 19 mm, z: 50 mm), cell size (dx = dy = dz = 1 mm), boundary (Mur primary), frequency (20 GHz), conductivity of the conductor (5.8 × 10 ⁸ S / m), and dielectric constant of the insulator (4.3) were set. Further, as for the dimensions of the microstrip line, the width of the strip conductor (2 mm), the width of the conductor plane (30 mm), and the insulator thickness (1 mm) were set. The length (depth) of the concave portion is a quarter length (λs / 4) of the wavelength λs of the slot line having a gap of 1 mm in width, and the interval between the concave portions adjacent to the concave and convex shape is 1 / the unnecessary mode wavelength λu. The length is 4 (λu / 4). Regarding the excitation of the microstrip line, delta gap feeding is performed between the strip conductor 1 and the conductor plane 2 on the left side of the line.

  From the above analysis results, when the conductor plane 2 does not have an uneven shape, as shown in FIG. 15 (b), the electric field strength is strong (dark color) in a wide range of the region deviated from the upper and lower lines. confirmed. That is, it is considered that the TM0 mode is propagated. On the other hand, when the conductor plane 2 has a concavo-convex shape, as shown in FIG. 15A, a portion having a slightly strong electric field strength on the left side of the region deviated from the upper and lower lines (close to the excitation source of the microstrip line) However, the electric field strength on the right side was confirmed to be weak. From this analysis result, the effect of suppressing the propagation of the TM0 mode by the conductor plane 1 having an uneven shape was recognized.

  Further, it is known that a TE mode and a TM mode having main electric field components as shown in the cross-sectional views of FIGS. 14A and 14B propagate through the microstrip line. Here, the TE mode and the TM mode are referred to as unnecessary modes. Unlike the quasi-TEM mode, the unnecessary mode has a main electric field component on a plane parallel to these conductor patterns between the strip conductor 1 and the conductor plane 2.

  On the other hand, the main electric field component of the quasi-TEM mode is perpendicular to this plane. Therefore, by using the structure shown in FIG. 6 described later, the unnecessary mode can be suppressed without degrading the quasi-TEM mode. That is, by disposing a conductor pattern in parallel between the strip conductor and the conductor plane, the unnecessary mode approaches a cutoff state and propagation is suppressed.

  However, an unnecessary mode (TM mode) having a main electric field component in the microstrip line propagation direction is converted into a TEM mode that propagates through the transmission line having the conductor pattern, the strip conductor, and the conductor plane. Since it is converted to an unnecessary mode, there is a possibility that a sufficient unnecessary mode suppression effect cannot be obtained.

  Therefore, in order to suppress the unnecessary propagation of the TEM mode, the side (edge) of the conductor pattern is a concavo-convex pattern composed of a concave portion and a convex portion. In this case, the concavo-convex concave portion serves as a slot line for short-circuit termination. By setting the depth (length) of the concave portion to ¼ of the slot line wavelength corresponding to the frequency to be suppressed, the effect is highest (see FIG. 7 described later). Further, the effect is most enhanced by setting the interval between the concave and convex adjacent concave portions to ¼ of the unnecessary TEM mode wavelength propagating through the conductor pattern. For example, when the width of the conductor pattern is smaller than the width of the strip conductor, it can be considered as a three-layer strip line having the conductor pattern as a central conductor and a strip conductor and a conductor plane as a ground plane.

  An equivalent circuit (equivalent model) of this structure is represented in FIG. In this equivalent model, unnecessary TEM mode transmission lines having a quarter length (λu / 4) of the unnecessary TEM mode wavelength λu are connected in multiple stages, and a 1/4 length (λs of the slot line wavelength λs is connected to the connection portion. / 4) The short-circuit termination slot line is inserted. Since the impedance when the slot line is seen from this connection portion is very large, the impedance at the connection portion of the unnecessary TEM mode line becomes very large. For this reason, the propagation of the unnecessary TEM mode is suppressed, and eventually the propagation of the unnecessary TM mode that excites the unnecessary TEM mode is suppressed. This is because an unnecessary TEM mode transmission line having a length n / 4 times (n is an odd number) of the unnecessary TEM mode wavelength λu is connected in multiple stages, and the connection portion is n / 4 times the slot line wavelength λs (n is an odd number). The same applies when a short-circuiting termination slot line having a length of is inserted.

  Further, by setting the interval between the connection portions to ¼ wavelength of the unnecessary TEM mode, an effect can be obtained regardless of the propagation direction distribution of the unnecessary TEM mode. If the interval between the connection portions is ½ wavelength of the unnecessary TEM mode, and the electric field maximum (impedance maximum) position in the distribution in the propagation direction of the unnecessary TEM mode coincides with the connection point, the unnecessary TEM mode suppression effect is obtained. It may not be enough. Therefore, by setting the interval between the connection portions to ¼ of the unnecessary TEM mode wavelength, it is possible to suppress the unnecessary TEM mode and the unnecessary TM mode exciting the unnecessary TEM mode regardless of the distribution of the propagation direction of the unnecessary TEM mode. An effect can be obtained. This is not limited to ¼ of the unnecessary TEM mode wavelength, and is the same for 3/4 and 5/4. In short, the same effect can be obtained if it is n / 4 times (n is an odd number).

  As described above, in the present embodiment, by adopting a simple structure in which at least a part of the outer shape of the conductor plane is a continuous concave / convex shape including a concave portion and a convex portion, a circuit having a high unnecessary mode suppression effect is obtained. An apparatus can be provided.

  The present embodiment may be configured as follows.

  1) When the wavelength of the propagation mode that is not desired to be generated in the conductive plane is λ, the interval between the adjacent concave portions of the concave and convex shape of the conductive plane may be n / 4 times λ (n is an odd number).

  2) When the wavelength of the propagation mode that is not desired to be generated in the conductive plane is λ, n / 4 of the mode wavelength when the component of λ propagates in the length direction of the recess with respect to the length of the recess of the conductive plane. The length of the convex portion of the conductive plane is twice (n is an odd number) or n / 4 times the mode wavelength (n is an odd number) when the component of λ propagates in the length direction of the convex portion. Good.

  3) The wavelength of the propagation mode that is not desired to be generated in the conductive plane may coincide with the wavelength of the signal propagation mode used in the circuit device.

  4) The concave portion of the conductive plane may be bent.

  5) The conductive plane may be a casing covering the circuit device, a heat sink, or a conductive material deposited or plated on a resin.

  6) The conductive plane may be arranged in parallel between two conductive patterns arranged opposite to each other in parallel.

  7) The conductive plane is n / 4 times λ when the wavelength of the propagation mode that can be generated is λ along the propagation direction in the transmission line having two conductive planes arranged in parallel and facing each other ( The width may be changed with a period of n).

  8) The concave and convex portions of the conductive plane may not be electrically connected to other conductor portions of the circuit device.

  The first to tenth embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 is a schematic diagram showing a circuit device according to a first embodiment of the present invention.

  The circuit device shown in FIG. 1 comprises four conductor layers: a first conductor layer comprising strip conductors 11, a second conductor layer comprising conductor planes 12, a third conductor layer comprising conductor planes 13, and strip conductors 14. A printed circuit board having a fourth conductor layer with three insulating layers 21, 22, and 23 interposed therebetween, and a circuit component 31 such as an LSI (Large Scale Integrated circuit) is mounted thereon.

  The printed circuit board constituting this circuit device has a microstrip line comprising a strip conductor 11 of a first conductor layer and a conductor plane 12 of a second conductor layer as a transmission line. As another configuration example of the transmission line, there may be a plurality of microstrip lines using the conductor plane 12 in common. The conductor plane 12 in the microstrip line is connected to a circuit ground (not shown) or a power source of the circuit device.

  In this embodiment, the plurality of microstrip lines are provided not only in one direction but also in various directions. For this reason, as shown in FIG. 1, by forming the edges of the four sides forming the peripheral outline of the conductor plane 12 into a concavo-convex pattern composed of a concave portion and a convex portion, an unnecessary mode (eg, TM0 mode) that propagates through the conductor plane 12 ) Is further enhanced. That is, with respect to the microstrip line propagating in the x-axis direction shown in the drawing, the unnecessary mode is mainly suppressed by the concave and convex portions and the convex portions provided in the x-axis direction shown in the drawing of the conductor plane 12. Further, with respect to the microstrip line propagating in the y-axis direction shown in the drawing, the unnecessary mode is mainly suppressed by the concave and convex portions and the convex portions provided in the y-axis direction shown in the drawing of the conductor plane 12.

  As a modification, another conductor plane, for example, the conductor plane 13 of the third conductor layer shown in FIG. By using the uneven pattern, it contributes to improving the characteristics of the circuit device.

  FIG. 2A is a perspective view showing a main part of a conductor plane of a circuit device according to a second embodiment of the present invention, and is a schematic view of another example of the conductor plane 12 having the concavo-convex shape of FIG.

  In the conductor plane 12 in the circuit device of this embodiment shown in FIG. 2A, of the concave and convex concave portions 12a and 12b, the concave portion 12a constitutes a slot line having a short-circuit termination 12c, and the line length is slot. It is 1/4 of the line mode wavelength λs. Further, the concave-convex adjacent concave portions 12a, that is, the interval between the slot lines is ¼ of the wavelength λu in the unnecessary mode propagating through the conductor plane 12.

  FIG. 2B shows an equivalent circuit (equivalent model) of the structure of the present embodiment shown in FIG. FIG. 2B shows that the impedance when the right side is viewed from the leftmost port in the figure is very large. Therefore, in this embodiment, the effect of suppressing the unnecessary mode is further enhanced by adopting this structure.

  FIG. 3 is a schematic graph of the dispersion characteristic (phase constant frequency characteristic) of the microstrip line used for designing the circuit device according to the third embodiment of the present invention.

  In general, in the low frequency band, the TEM mode is dominant, and it is known that the unnecessary TM0 mode is very small. However, as the frequency increases, the unnecessary TM0 mode cannot be ignored and approaches the phase constant (wavelength) of the TEM mode. Therefore, the interference between different modes increases as the phase constants are closer, and the interference increases in the vicinity of the frequency at which the curves of both modes intersect in the graph of FIG. Therefore, in this embodiment, it is a more effective design to suppress the propagation of unnecessary modes at the intersecting frequency (wavelength).

  FIG. 4A is a schematic diagram of a circuit device according to a fourth embodiment of the present invention.

  The circuit device of the present embodiment shown in FIG. 4A has a configuration in which a concave and convex portion 12a is bent in the conductor plane 12 of the second conductor layer of the printed circuit board of FIG. Thereby, in the present embodiment, the concave and convex portion 12a can be brought close to the edge of the conductor plane 12, and the design freedom of other signal wiring and component mounting can be improved.

  For example, as shown in FIG. 4B, when the strip conductor 11 of the first conductor layer in the vicinity of the edge of the conductor plane 12 forms a microstrip line, if the concave portion 12a is not bent, the strip conductor 11 becomes the concave portion 12a. The propagation characteristics may deteriorate due to crossing. However, if the strip conductor 11 does not cross the recess 12a by bending the recess 12a and such a deterioration factor can be avoided, it contributes to the improvement of characteristics as a circuit device.

  FIG. 5 is a schematic diagram showing a circuit device according to a fifth embodiment of the present invention.

  The circuit device of this embodiment shown in FIG. 5 has three conductor layers, that is, a first conductor layer composed of strip conductors 41, a second conductor layer composed of a common conductor plane 42, and a third conductor layer composed of strip conductors 43. Is a printed circuit board having two insulator layers 51 and 52 sandwiched therebetween, and a circuit component 61 such as an LSI is mounted thereon.

  This circuit device is provided with a conductive housing having a flat surface portion or a heat sink 44. This conductive casing or heat sink 44 is disposed opposite to and parallel to the strip conductor 43 of the third conductor layer, and constitutes a microstrip line with the strip conductor 43.

  In the present embodiment, the conductor plane 12 having the concavo-convex shape of FIG. 1 is constituted by a conductive casing having a flat portion or a heat sink 44 instead of the conductor layer of the printed circuit board. Thus, when the strip conductor 43 of the conductor layer of the printed circuit board and the flat portion of the housing or the heat sink 44 constitute a microstrip line, the concave and convex portions of the concave or convex shape of the housing or the heat sink 44 are formed. The unnecessary mode propagating through the casing can be suppressed by the unit, which contributes to improvement of characteristics as a circuit device.

  Note that the housing may be made of a resin to which a conductive material is attached by vapor deposition or plating.

  FIG. 6 is a schematic diagram showing a circuit device according to a sixth embodiment of the present invention.

  The circuit device of the present embodiment shown in FIG. 6 has a conductor plane of the second conductor layer of the printed circuit board shown in the first embodiment between the strip conductor 71 of the microstrip line and the conductor plane 73 in parallel therewith. 12, that is, a conductor plane 72 having a concave and convex shape whose peripheral outer shape is formed by a concave portion and a convex portion. The conductor plane 72 is not conducted to any circuit and is in a floating state in the insulator layer 81.

  As a result, propagation of unnecessary modes such as TE and TM modes as shown in FIGS. 14A and 14B propagating through the microstrip line is suppressed, which contributes to improvement in propagation characteristics of the TEM mode, which is the basic mode. .

  FIG. 7 is a perspective view showing a principal part of a conductor plane of a circuit device according to a seventh embodiment of the present invention, which is another example of the conductor plane 72 having the concavo-convex shape of FIG.

  In the conductor plane 72 shown in FIG. 7, the concave-convex recess 72a is a slot line having a short-circuit termination 72c, and the line length is ¼ of the slot line mode wavelength λs. The interval between adjacent slot lines is ¼ of the wavelength λu in the unnecessary mode propagating through the conductive plane. This unnecessary mode is a basic mode of a three-layer strip line using two upper and lower conductor patterns as a ground plane.

  Unnecessary modes such as TE and TM modes propagating through the microstrip line cause this unnecessary three-layer stripline mode. Therefore, in this embodiment, by suppressing this three-layer stripline mode, it contributes to the improvement of the propagation characteristics of the microstrip line.

  The equivalent circuit (equivalent model) having the structure shown in FIG. 7 is obtained by replacing λu with the wavelength of the three-layer stripline mode and λs with the wavelength of the slotline mode in FIG.

  FIG. 8A is a perspective view of a main part showing a conductor plane of a circuit device according to an eighth embodiment of the present invention, which is another example of the conductor plane 72 having the concavo-convex shape of FIG.

  In the conductor plane 72 shown in FIG. 8A, the concavo-convex convex portion 72b is an open-terminated three-layer strip line, and the line length is ¼ of the three-layer strip line mode wavelength λs. The interval between adjacent three-layer strip lines is 1/4 of the wavelength λu in the unnecessary mode propagating through the conductor plane. This unnecessary mode is a basic mode of a three-layer strip line using two upper and lower conductor patterns as a ground plane. The three-layer strip line has a wavelength different from that of the convex three-layer strip line because the width of the strip conductor does not match.

  The equivalent circuit (equivalent model) having the structure shown in FIG. 8A is a three-layer stripline mode in which λu is unnecessary and λs is a convex portion, as shown in FIG. 8B. Is the wavelength. As shown in FIG. 8B, since the impedance when the right side is viewed from the left end port is very small, the unnecessary mode component is reflected due to mismatching, and this mode enhances the effect of suppressing the unnecessary mode.

  Unnecessary modes such as TE and TM modes propagating through the microstrip line cause this unnecessary three-layer stripline mode. Therefore, in this embodiment, by suppressing this unnecessary three-layer stripline mode, it contributes to the improvement of the propagation characteristics of the microstrip line.

  FIG. 9 is a perspective view showing a principal part of a conductor plane of a circuit device according to a ninth embodiment of the present invention, which is another example of the conductor plane 72 having the concavo-convex shape of FIG.

  The conductor plane 72 shown in FIG. 9 has an uneven shape that is symmetrical with respect to the propagation direction of the microstrip line. The concave and convex concave portions 72a and 72b have a width that is larger or smaller in the propagation direction of the microstrip line. That is, this corresponds to the characteristic impedance of the three-layer strip line composed of the conductor plane and the upper and lower conductors being small or large, and contributes to suppressing the mode propagating to the three-layer strip line. Unnecessary modes such as the TE and TM modes propagating through the microstrip line cause this unnecessary three-layer stripline mode. Therefore, by suppressing this three-layer stripline mode, the propagation characteristics of the microstrip line can be reduced. Contributes to improvement.

  FIG. 10A is a perspective view of a main part showing a conductor plane of a circuit device according to the tenth embodiment of the present invention, which is another example of the conductor plane 72 having the concavo-convex shape of FIG.

  In the conductive plane 72 shown in FIG. 10A, the wavelength of the three-layer strip line propagating through the narrow portion is λu1, and the wavelength of the three-layer strip line propagating through the wide portion is λu2. At this time, the length in the propagation direction of the microstrip line is set to λu1 / 4 and λu2 / 4, respectively, which contributes to suppressing the mode propagating to the three-layer stripline. Unnecessary modes such as the TE and TM modes propagating through the microstrip line cause this unnecessary three-layer stripline mode. Therefore, by suppressing this three-layer stripline mode, the propagation characteristics of the microstrip line can be reduced. Contributes to improvement.

  An equivalent circuit (equivalent model) having the structure shown in FIG. 10A is represented by FIG. FIG. 19B shows that a large reflection coefficient is obtained at a point where the thickness of the conductor plane having an uneven shape changes, so that the impedance when the right side is viewed from the left end port is very large. The suppression effect of increases.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2007-263484 for which it applied on October 9, 2007, and takes in those the indications of all here.

  The present invention is applicable to a circuit device having a transmission line. In particular, the present invention can be used in a structure for suppressing unnecessary mode propagation in a strip line in a circuit device having a strip line.

Claims (10)

A circuit device comprising a conductive strip constituting a transmission line, and a conductive plane disposed opposite to and parallel to the conductive strip,
The circuit device according to claim 1, wherein at least a part of a peripheral shape of the conductive plane is formed in a continuous uneven shape including a concave portion and a convex portion.   When the wavelength of a propagation mode that is not desired to be generated in the conductive plane is λ, the interval between adjacent concave portions of the concave and convex shape of the conductive plane is n / 4 times (λ is an odd number) of λ. The circuit device according to claim 1.   Assuming that λ is a wavelength of a propagation mode that is not desired to be generated in the conductive plane, n is a mode wavelength when the component of λ propagates in the length direction of the recess with respect to the length of the recess of the conductive plane. / 4 times (n is an odd number), or the length of the convex portion of the conductive plane is n / 4 times the mode wavelength when the component of λ propagates in the length direction of the convex portion (n is an odd number) The circuit device according to claim 1, wherein:   4. The circuit device according to claim 2, wherein a wavelength of a propagation mode that is not desired to be generated in the conductive plane matches a wavelength of a signal propagation mode that is used in the circuit device.   The circuit device according to claim 1, wherein a concave portion of the conductive plane is bent.   The circuit device according to claim 1, wherein the conductive plane is a casing covering the circuit device, a heat sink, or a conductive material deposited or plated on a resin. .   6. The circuit device according to claim 1, wherein the conductive plane is disposed in parallel between two conductive patterns disposed opposite to each other in parallel.   The conductive plane is n / 4 times the λ when the wavelength of a propagation mode that can be generated along the propagation direction in a transmission line having two conductive planes arranged opposite to each other in parallel is λ ( 8. The circuit device according to claim 7, wherein the width is changed in a cycle of n being an odd number).   9. The circuit device according to claim 1, wherein the concave portion and the convex portion of the conductive plane are not electrically connected to another conductor portion of the circuit device. A high-frequency printed circuit board having a conductive strip constituting a transmission line and a conductive plane disposed opposite to and parallel to the conductive strip,
The high-frequency printed circuit board according to claim 1, wherein at least a part of a peripheral shape of the conductive plane is formed in a continuous uneven shape including a concave portion and a convex portion.

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