JPWO2019203170A1 - Directional coupler and microwave heating device with it - Google Patents

Abstract

The directional coupler comprises an opening and a coupling line. The opening has a first elongated hole and a second elongated hole that intersect each other and are arranged at positions that do not intersect the tube axis of the waveguide in a plan view. The coupling line includes a first transmission line and a second transmission line. The first transmission line has a first crossing line portion. The first crossing line passes through the opening crossing where the first and second long holes intersect from one end of the pipe axis in a plan view, and extends away from the pipe axis as it approaches the perpendicular line orthogonal to the pipe axis. It exists and intersects the first elongated hole at a position farther from the pipe axis than the opening intersection. The second transmission line has a second crossing line portion. The second crossing line extends away from the pipe axis as it approaches the vertical line from the other end of the pipe shaft in a plan view, and intersects the second elongated hole at a position farther from the pipe shaft than the opening intersection. .. The first transmission line and the second transmission line are connected to each other at a position outside the region of the opening in a plan view.

Description

The present disclosure relates to a directional coupler for detecting the power level of microwaves propagating in a waveguide and a microwave heating device including the directional coupler.

A directional coupler is known as a device for detecting the power level of microwaves propagating in a waveguide. The directional coupler separates the traveling wave and the reflected wave propagating in the waveguide and detects each of them.

As a conventional directional coupler, for example, the directional coupler described in Patent Document 1 is known. The directional coupler of Patent Document 1 includes an opening arranged on the wall surface of the waveguide and a coupling line arranged outside the waveguide. The opening is arranged at a position that does not intersect the tube axis of the waveguide in a plan view, and is formed so as to radiate a circularly polarized microwave. The coupling line includes a first transmission line and a second transmission line that cross the opening in a plan view. The first transmission line and the second transmission line are arranged so as to face each other with the central portion of the opening interposed therebetween, and are connected to each other at a position outside the region vertically above the opening.

According to the directional coupler of Patent Document 1, the rotation direction of the circularly polarized wave traveling wave radiated from the opening is opposite to that of the circularly polarized wave reflected wave. By utilizing the difference in the rotation direction of the circularly polarized microwaves, the traveling wave and the reflected wave can be separated and detected.

Japanese Patent No. 6176540

However, in the above-mentioned conventional directional coupler, there is still room for improvement from the viewpoint of detecting the traveling wave and the reflected wave by separating them with higher accuracy.

Therefore, it is an object of the present disclosure to provide a directional coupler capable of more accurately separating and detecting a traveling wave and a reflected wave, and a microwave heating device including the directional coupler.

The directional coupler of one aspect of the present disclosure comprises an opening located on the wall surface of the waveguide and a coupling line located outside the waveguide, with traveling waves and reflections propagating through the waveguide. Detects separately from the wave.

The opening has a first elongated hole and a second elongated hole that intersect each other and are arranged at positions that do not intersect the tube axis of the waveguide in a plan view. The coupling line includes a first transmission line and a second transmission line.

The first transmission line has a first crossing line portion. The first crossing line passes through the opening crossing where the first and second long holes intersect from one end of the pipe axis in a plan view, and extends away from the pipe axis as it approaches the perpendicular line orthogonal to the pipe axis. It exists and intersects the first elongated hole at a position farther from the pipe axis than the opening intersection.

The second transmission line has a second crossing line portion. The second crossing line extends away from the pipe axis as it approaches the vertical line from the other end of the pipe shaft in a plan view, and intersects the second elongated hole at a position farther from the pipe shaft than the opening intersection. ..

One end of the first transmission line is connected to one end of the second transmission line at a position outside the region of the opening in a plan view.

According to the directional coupler of this embodiment, the traveling wave and the reflected wave can be separated and detected with higher accuracy.

FIG. 1 is a perspective view of a directional coupler according to an embodiment of the present disclosure. FIG. 2 is a perspective view of the directional coupler according to the embodiment in a state where the printed circuit board is removed. FIG. 3 is a plan view of the waveguide according to the embodiment. FIG. 4 is a circuit configuration diagram of a printed circuit board provided in the directional coupler according to the embodiment. FIG. 5 is a diagram for explaining the principle of radiating circularly polarized microwaves from the cross aperture. FIG. 6 is a diagram for explaining the direction and amount of microwaves propagating through a microstrip line and changing over time. FIG. 7 is a diagram for explaining the direction and amount of microwaves propagating through a microstrip line and changing over time. FIG. 8A is a plan view showing a first modification of the microstrip line. FIG. 8B is a plan view showing a second modification of the microstrip line. FIG. 8C is a plan view showing a third modification of the microstrip line. FIG. 8D is a plan view showing a fourth modification of the microstrip line. FIG. 8E is a plan view showing a fifth modification of the microstrip line. FIG. 8F is a plan view showing a sixth modification of the microstrip line. FIG. 9 is a schematic view of the microwave heating device according to the embodiment.

The present inventors have obtained the following findings as a result of diligent studies in order to separate and detect the traveling wave and the reflected wave with higher accuracy.

In the conventional directional coupler, the coupling line is composed of a plurality of lines parallel to the tube axis in a plan view and a plurality of lines perpendicular to the tube axis in a plan view connected at right angles as one line. Will be done. With this configuration, the influence of the impedance of the load connected to the waveguide can be mitigated, and the traveling wave and the reflected wave can be separated accurately.

The present inventors concentrate the magnetic field at a position where the coupled line bends at a right angle (or an acute angle), obstruct the flow of the current (microwave) in the coupled line, and separate the traveling wave from the reflected wave. It was found that it affects. The present inventors have found that in the conventional directional coupler, there are many places where the coupling line bends at a right angle, and these have a great influence on the degree of separation between the traveling wave and the reflected wave. The present inventors have stated that by keeping the bent portion of the coupling line away from the vertical region of the opening that is strongly affected by the magnetic field, it is possible to suppress the obstruction of the current flow in the coupling line. I found out.

Based on these findings, the present inventors have found the following inventions. The present inventors have confirmed that these inventions improve the directional (separation degree between the traveling wave and the reflected wave) by 5 dB or more (about 3 times or more) as compared with the conventional directional coupler.

The directional coupler of the first aspect of the present disclosure includes an opening arranged on the wall surface of the waveguide and a coupling line arranged outside the waveguide, and a traveling wave propagating in the waveguide. And the reflected wave are detected separately.

The opening has a first elongated hole and a second elongated hole that intersect each other and are arranged at positions that do not intersect the tube axis of the waveguide in a plan view. The coupling line includes a first transmission line and a second transmission line.

The first transmission line has a first crossing line portion. The first crossing line passes through the opening crossing where the first and second long holes intersect from one end of the pipe axis in a plan view, and extends away from the pipe axis as it approaches the perpendicular line orthogonal to the pipe axis. It exists and intersects the first elongated hole at a position farther from the pipe axis than the opening intersection.

The second transmission line has a second crossing line portion. The second crossing line extends away from the pipe axis as it approaches the vertical line from the other end of the pipe shaft in a plan view, and intersects the second elongated hole at a position farther from the pipe shaft than the opening intersection. ..

One end of the first transmission line is connected to one end of the second transmission line at a position outside the region of the opening in a plan view.

In the directional coupler of the second aspect of the present disclosure, in addition to the first aspect, the first transmission line and the second transmission line are outside the rectangular region circumscribing the opening in a plan view, and They are connected to each other at a position farther from the tube axis than the rectangular area.

In the directional coupler of the third aspect of the present disclosure, in addition to the first aspect, at least one of the first crossing line portion and the second crossing line portion corresponds to the corresponding first elongated hole or the second in plan view. The long hole intersects the opening at a position closer to the tip of the opening than the intersection.

In the directional coupler of the fourth aspect of the present disclosure, in addition to the first aspect, at least one of the first crossing line portion and the second crossing line portion corresponds to the corresponding first elongated hole or the second in plan view. Orthogonal to the long hole.

In the directional coupler of the fifth aspect of the present disclosure, in addition to the first aspect, the coupling line has a plurality of straight sections including a first crossing line portion and a second crossing line portion. Two straight portions adjacent to each other among the plurality of straight portions are connected so as to form an obtuse angle.

In the directional coupler of the sixth aspect of the present disclosure, in addition to the fifth aspect, a plurality of straight portions are a linear portion connecting the other end of the first crossing line portion and the first output portion, and a third. 2 Includes a straight line portion connecting the crossing line portion and the second output portion.

In the directional coupler of the seventh aspect of the present disclosure, in addition to the first aspect, the first intersection and the second intersection, which are the intersections of the first intersection and the first elongated hole in a plan view, The total distance between the first transmission line and the second transmission line, which is farther from the tube axis than the virtual straight line passing through the second coupling point, which is the intersection of the second long hole, is set to 1/4 of the effective length. To.

In the directional coupler of the eighth aspect of the present disclosure, in addition to the first aspect, a first aspect that passes through the opening intersection in a plan view and is farther from the tube axis than a parallel line parallel to the tube axis. The total distance between the transmission line and the second transmission line is set to 1/2 of the effective length.

The microwave heating device of the ninth aspect of the present disclosure includes the directional coupler of the first aspect.

Hereinafter, a directional coupler and a microwave heating device including the directional coupler according to the embodiment of the present disclosure will be described with reference to the drawings.

FIG. 1 is a perspective view of the directional coupler 5 according to the embodiment of the present disclosure. FIG. 2 is a perspective view of the directional coupler 5 with the printed circuit board 12 removed. FIG. 3 is a plan view of the waveguide 3. FIG. 4 is a circuit configuration diagram of the printed circuit board 12 provided on the directional coupler 5.

As shown in FIGS. 1 to 3, the directional coupler 5 is arranged on the wall surface of the waveguide 3 that transmits microwaves. The waveguide 3 is a rectangular waveguide. The cross section of the waveguide 3 orthogonal to the tube axis L1 has a rectangular shape. The tube axis L1 is the central axis of the waveguide 3 in the width direction.

The directional coupler 5 includes a cross opening 11, a printed circuit board 12, and a support portion 14. The cross opening 11 is an X-shaped opening arranged on the wide surface (Wide Plane) 3a of the waveguide 3. The printed circuit board 12 is arranged outside the waveguide 3 so as to face the cross opening 11. The support portion 14 supports the printed circuit board 12 on the outer surface of the waveguide 3.

As shown in FIG. 3, the cross opening 11 is arranged at a position that does not intersect the tube axis L1 of the waveguide 3 in a plan view. The opening central portion 11c of the cross opening 11 is arranged apart from the tube axis L1 of the waveguide 3 by the dimension D1 in a plan view. The dimension D1 is, for example, 1/4 of the width of the waveguide 3. The cross opening 11 radiates the microwave propagating in the waveguide 3 as a circularly polarized microwave toward the printed circuit board 12.

The opening shape of the cross opening 11 includes the width and height of the waveguide 3, the power level and frequency band of the microwave propagating in the waveguide 3, and the power level of the circularly polarized microwave radiated from the cross opening 11. It is decided according to the conditions such as.

For example, the width of the waveguide 3 is 100 mm, the height is 30 mm, the wall surface thickness of the waveguide 3 is 0.6 mm, the maximum power level of the microwave propagating in the waveguide 3 is 1000 W, and the frequency band is 2450 MHz. When the maximum power level of the circularly polarized microwave radiated from the cross opening 11 is about 10 mW, the length 11w and the width 11d of the cross opening 11 are set to 20 mm and 2 mm, respectively.

As shown in FIG. 4, the cross opening 11 includes a first elongated hole 11e and a second elongated hole 11f that intersect each other. The opening central portion 11c of the cross opening 11 coincides with the opening intersection where the first elongated hole 11e and the second elongated hole 11f intersect. The cross opening 11 is formed line-symmetrically with respect to the perpendicular line L2. The perpendicular line L2 is orthogonal to the pipe axis L1 and passes through the central portion 11c of the opening.

In the present embodiment, the first elongated hole 11e and the second elongated hole 11f intersect at an angle of 90 degrees. However, the present disclosure is not limited to this. The first elongated hole 11e and the second elongated hole 11f may intersect at an angle of 60 degrees or 120 degrees.

When the opening central portion 11c of the cross opening 11 is arranged at a position overlapping the tube axis L1 in a plan view, the electric field reciprocates along the microwave transmission direction without rotating. In this case, the cross aperture 11 emits linearly polarized microwaves.

If the central portion 11c of the opening deviates from the tube axis L1 even a little, the electric field rotates. However, when the opening central portion 11c is closer to the tube shaft L1 (the closer the dimension D1 is to 0 mm), a distorted rotating electric field is generated. In this case, the cross aperture 11 emits elliptically polarized microwaves.

In this embodiment, the dimension D1 is set to about 1/4 of the width of the waveguide 3. In this case, an electric field of rotation that is almost perfectly circular is generated. The cross opening 11 radiates microwaves having a substantially circularly polarized wave. Therefore, the rotation direction of the circularly polarized microwave becomes clearer. As a result, the traveling wave and the reflected wave can be accurately separated and detected.

The printed circuit board 12 has a substrate back surface 12b facing the cross opening 11 and a substrate surface 12a on the side opposite to the substrate back surface 12b. The substrate surface 12a has a copper foil (not shown) formed so as to cover the entire substrate surface 12a as an example of the microwave reflecting member. This copper foil prevents the circularly polarized microwaves radiated from the cross opening 11 from passing through the printed circuit board 12.

As shown in FIG. 4, a microstrip line 13 which is an example of a coupling line is arranged on the back surface 12b of the substrate. The microstrip line 13 is composed of, for example, a transmission line having a characteristic impedance of approximately 50Ω. The microstrip line 13 is arranged so as to surround the opening central portion 11c of the cross opening 11.

Hereinafter, the effective length λ _re of the microstrip line 13 will be described. Assuming that the width of the microstrip line 13 is w, the thickness of the printed circuit board 12 is h, the speed of light is c, the frequency of electromagnetic waves is f, and the relative permittivity of the printed circuit board is ε _r , the effective length of the microstrip line 13 is λ. _re is expressed by the following equation. The effective length λ _re is the wavelength of the electromagnetic wave propagating in the microstrip line 13.

Specifically, the microstrip line 13 includes a first transmission line 13a and a second transmission line 13b. The first transmission line 13a has a first straight line portion 13aa which is an example of the first crossing line portion. The first straight line portion 13aa intersects the first elongated hole 11e at a position farther from the pipe axis L1 than the opening central portion 11c in a plan view. The first straight line portion 13aa extends away from the pipe axis L1 as it approaches the perpendicular line L2.

The second transmission line 13b has a second straight line portion 13ba, which is an example of the second crossing line portion. The second straight line portion 13ba intersects the second elongated hole 11f at a position farther from the pipe axis L1 than the opening central portion 11c in a plan view. The second straight line portion 13ba extends away from the pipe axis L1 as it approaches the perpendicular line L2. The first straight line portion 13aa and the second straight line portion 13ba are arranged line-symmetrically with respect to the perpendicular line L2.

The first transmission line 13a and the second transmission line 13b are connected to each other in a plan view outside the rectangular region E1 and at a position farther from the pipe axis L1 than the rectangular region E1. The first straight line portion 13aa intersects the first elongated hole 11e at a position closer to the opening tip portion 11ea than the opening central portion 11c in a plan view.

The first straight line portion 13aa is orthogonal to the first elongated hole 11e in a plan view. The second straight line portion 13ba intersects the second elongated hole 11f at a position closer to the opening tip portion 11fa than the opening central portion 11c in a plan view. The second straight line portion 13ba is orthogonal to the second elongated hole 11f in a plan view.

One end of the first transmission line 13a and one end of the second transmission line 13b are connected to each other outside the region overlapping the cross opening 11 in a plan view. One end of the first straight line portion 13aa is connected to one end of the second straight line portion 13ba outside the rectangular region E1 circumscribing the cross opening 11.

The first coupling point P1 is a point where the first straight line portion 13aa and the first elongated hole 11e intersect each other in a plan view. The second coupling point P2 is a point where the second straight line portion 13ba and the second elongated hole 11f intersect each other in a plan view. The straight line connecting the first coupling point P1 and the second coupling point P2 is defined as a virtual straight line L3. In the present embodiment, the total distance between the first transmission line 13a and the second transmission line 13b, which are farther from the tube axis L1 than the virtual straight line L3, is set to 1/4 of the _{effective length λ re.}

In a plan view, a line that passes through the central portion 11c of the opening and is parallel to the tube axis L1 is defined as a parallel line L4. In the present embodiment, the total distance between the first transmission line 13a and the second transmission line 13b, which are farther from the pipe axis L1 than the parallel line L4, is set to 1/2 of the _{effective length λ re.}

The first transmission line 13a includes a third straight line portion 13ab that connects the other end of the first straight line portion 13aa and the first output section 131. The first straight line portion 13aa and the third straight line portion 13ab are connected so as to form an obtuse angle (for example, 135 degrees).

The second transmission line 13b includes a fourth straight line portion 13bb that connects the other end of the second straight line portion 13ba and the second output section 132. The second straight line portion 13ba and the fourth straight line portion 13bb are connected so as to form an obtuse angle (for example, 135 degrees). The third straight line portion 13ab and the fourth straight line portion 13bb are arranged in parallel with the perpendicular line L2.

The first output unit 131 and the second output unit 132 are arranged outside the support unit 14 (see FIGS. 1 and 2) in a plan view. The first detection circuit 15 is connected to the first output unit 131. The first detection circuit 15 detects the level of the microwave signal and outputs the detected microwave signal level as a control signal. A second detection circuit 16 is connected to the second output unit 132. The second detection circuit 16 detects the level of the microwave signal and outputs the detected microwave signal level as a control signal.

In the present embodiment, the first detection circuit 15 and the second detection circuit 16 both include a smoothing circuit (not shown) composed of a chip resistor and a Schottky diode. The first detection circuit 15 rectifies the microwave signal from the first output unit 131 and converts the rectified microwave signal into a DC voltage. The converted DC voltage is output to the first detection output unit 18.

Similarly, the second detection circuit 16 rectifies the microwave signal from the second output unit 132 and converts the rectified microwave signal into a DC voltage. The converted DC voltage is output to the second detection output unit 19.

The printed circuit board 12 has four holes (holes 20a, 20b, 20c, 20d) for attaching the printed circuit board 12 to the waveguide 3. A copper foil serving as a ground is formed around the holes 20a, 20b, 20c, and 20d on the back surface 12b of the substrate. The portion where the copper foil is formed has the same potential as the substrate surface 12a.

The printed circuit board 12 is fixed to the waveguide 3 by screwing it through the holes 20a, 20b, 20c, 20d to the support portion 14 with screws 201a, 201b, 201c, 201d (see FIG. 1).

As shown in FIG. 2, the support portion 14 has screw portions 202a, 202b, 202c, 202d for screwing the screws 201a, 201b, 201c, and 201d, respectively. The screw portions 202a, 202b, 202c, and 202d are formed on the flange portion provided on the support portion 14.

The support portion 14 has conductivity and is arranged so as to surround the cross opening 11 in a plan view. The support portion 14 functions as a shield that prevents the circularly polarized microwaves radiated from the cross opening 11 from leaking out of the support portion 14.

The support portion 14 has a groove 141 and a groove 142 through which the third straight line portion 13ab and the fourth straight line portion 13bb of the microstrip line 13 pass. With this configuration, the first output section 131 and the second output section 132 of the microstrip line 13 can be arranged outside the support section 14. The grooves 141 and 142 function as an extraction unit for taking out the microwave signal propagating in the microstrip line 13 to the outside of the support unit 14. The grooves 141 and 142 can be formed by denting the flange portion of the support portion 14 so as to be separated from the printed circuit board 12.

1 and 2 show a connector 18a and a connector 19a connected to the first detection output unit 18 and the second detection output unit 19 shown in FIG. 4, respectively.

Next, the operation and operation of the directional coupler 5 will be described.

First, with reference to FIG. 5, the principle of radiating circularly polarized microwaves from the cross aperture 11 will be described. In FIG. 5, the magnetic field distribution 3d generated in the waveguide 3 is shown by a dotted concentric ellipse. The direction of the magnetic field of the magnetic field distribution 3d is indicated by an arrow. The magnetic field distribution 3d moves in the waveguide 3 in the microwave transmission direction A1 with the passage of time.

At time t = t0 shown in FIG. 5A, the magnetic field distribution 3d is formed. At this time, the magnetic field indicated by the broken line arrow B1 excites the first elongated hole 11e of the cross opening 11. At the time t = t0 + t1 shown in FIG. 5B, the magnetic field indicated by the broken line arrow B2 excites the second elongated hole 11f of the cross opening 11.

At the time t = t0 + T / 2 (T is the period of the in-tube wavelength of the microwave) shown in FIG. 5 (c), the magnetic field indicated by the broken line arrow B3 excites the first elongated hole 11e of the cross opening 11. At the time t = t0 + T / 2 + t1 shown in FIG. 5D, the magnetic field indicated by the broken line arrow B4 excites the second elongated hole 11f of the cross opening 11. At time t = t0 + T, similarly to time t = t0, the magnetic field indicated by the broken line arrow B1 excites the first elongated hole 11e of the cross opening 11.

By repeating these states in sequence, a circularly polarized microwave rotating counterclockwise (microwave rotation direction 32) is radiated from the cross opening 11 to the outside of the waveguide 3.

Here, assuming that the microwave propagating along the arrow 30 shown in FIG. 3 is a traveling wave and the microwave propagating along the arrow 31 is a reflected wave, the traveling wave is in the same direction as the transmission direction A1 shown in FIG. Propagate. Therefore, as described above, the circularly polarized microwaves rotating counterclockwise are radiated from the cross opening 11 to the outside of the waveguide 3.

On the other hand, the reflected wave propagates in the direction opposite to the transmission direction A1 shown in FIG. Therefore, a circularly polarized microwave rotating clockwise is radiated from the cross opening 11 to the outside of the waveguide 3.

Circularly polarized microwaves radiated out of the waveguide 3 couple to the microstrip line 13 facing the cross aperture 11. The microstrip line 13 outputs most of the microwaves radiated from the cross opening 11 by the traveling wave propagating along the arrow 30 to the first output unit 131.

On the other hand, the microstrip line 13 outputs most of the microwaves radiated from the cross opening 11 by the reflected waves propagating along the arrow 31 to the second output unit 132. As a result, the traveling wave and the reflected wave can be separated and detected with higher accuracy. This will be described in more detail with reference to FIG.

FIG. 6 is a diagram for explaining the direction and amount of microwaves propagating through the microstrip line 13 and changing with the passage of time. There is a gap between the microstrip line 13 and the cross opening 11. Originally, the time required for the microwave to reach the microstrip line 13 is delayed by the time for the microwave to propagate through this gap. However, for convenience, it is assumed that there is no time delay here.

Here, the region where the cross opening 11 and the microstrip line 13 intersect in a plan view is referred to as a coupling region. The first coupling point P1 is substantially the center of the coupling region where the first elongated hole 11e and the microstrip line 13 intersect. The second coupling point P2 is approximately the center of the coupling region where the second elongated hole 11f and the microstrip line 13 intersect.

In FIG. 6, the amount of microwaves propagating through the microstrip line 13 (current flowing due to the interlinking of magnetic fields) is represented by the thickness of the line indicated by the solid arrow. That is, when the amount of microwaves propagating in the microstrip line 13 is large, the line is thick, and when the amount of microwaves propagating in the microstrip line 13 is small, the line is thin.

At time t = t0 shown in FIG. 6A, the magnetic field indicated by the broken line arrow B1 excites the first elongated hole 11e of the cross opening 11, and the microwave indicated by the thick solid arrow M1 is present at the first coupling point P1. Occurs. This microwave propagates on the microstrip line 13 toward the second coupling point P2.

At the time t = t0 + t1 shown in FIG. 6B, the magnetic field indicated by the broken line arrow B2 excites the second elongated hole 11f of the cross opening 11, and the microwave indicated by the thick solid line arrow M2 is present at the second coupling point P2. Occurs.

When the effective propagation time of the microwave by the microstrip line 13 between the first coupling point P1 and the second coupling point P2 is set to time t1, it occurs at the first coupling point P1 at the time shown in FIG. 6A. The microwave propagates to the second coupling point P2 at the time shown in FIG. 6 (b). That is, at the time shown in 6 (b) of the figure, the microwave indicated by the solid arrow M1 and the microwave indicated by the solid arrow M2 are generated at the second coupling point P2.

Therefore, the two microwaves are added and propagated along the microstrip line 13 toward the second output unit 132, and are output to the second output unit 132 after a lapse of a predetermined time. In the present embodiment, since the effective propagation time is set to the time t1, the total distance between the first transmission line 13a and the second transmission line 13b, which are farther from the tube axis L1 than the virtual straight line L3, is the effective length λ _re. It is set to 1/4 of. With this configuration, the design of the microstrip line 13 can be easily performed.

At the time t = t0 + T / 2 shown in FIG. 6 (c), the magnetic field indicated by the broken line arrow B3 excites the first elongated hole 11e of the cross opening 11, and the first coupling point P1 is the micro indicated by the thin solid arrow M3. Waves occur. This microwave propagates through the microstrip line 13 toward the first output unit 131, and is output to the first output unit 131 after a lapse of a predetermined time.

The reason why the thickness of the solid arrow M3 is made thinner than the thickness of the solid arrow M1 is as follows. Circularly polarized microwaves rotating counterclockwise (microwave rotation direction 32) are radiated from the cross opening 11 as described above.

At the time shown in FIG. 6A, the microwave indicated by the solid arrow M1 generated at the first coupling point P1 propagates in substantially the same direction as the rotation direction of the microwave radiated from the cross opening 11. Therefore, the energy of the microwave indicated by the solid arrow M1 is not reduced.

On the other hand, at the time shown in FIG. 6C, the microwave indicated by the solid arrow M3 generated at the first coupling point P1 propagates in a direction substantially opposite to the rotation direction of the microwave radiated from the cross opening 11. Therefore, the energy of the combined microwave is reduced. Therefore, the amount of microwaves indicated by the solid arrow M3 is smaller than the amount of microwaves indicated by the solid arrow M1.

At the time t = t0 + T / 2 + t1 shown in FIG. 6 (d), the magnetic field indicated by the broken line arrow B4 excites the second elongated hole 11f of the cross opening 11, and the second coupling point P2 is the micro indicated by the thin solid arrow M4. Waves occur. This microwave propagates toward the first coupling point P1. The reason for reducing the thickness of the solid line arrow M4 is the same as the reason for reducing the thickness of the solid line arrow M3 described above.

At time t = t0 + T, the magnetic field indicated by the broken line arrow B1 excites the first elongated hole 11e of the cross opening 11 as at time t = t0 shown in FIG. 6A. In this case, the microwave indicated by the thin solid arrow M4, which was not described in the case of the time shown in FIG. 6A, exists on the microstrip line 13.

The microwave indicated by the thin solid arrow M4 propagates to the first coupling point P1 at time t = t0 + T (that is, t = t0). The microwave indicated by the thin solid arrow M4 propagates in the opposite direction to the microwave indicated by the thick solid arrow M1. Therefore, the microwave indicated by the solid arrow M4 is canceled and disappears, and is not output to the first output unit 131.

Strictly speaking, the amount of microwaves propagating from the first coupling point P1 at time t = t0 is the amount obtained by subtracting the amount of microwaves indicated by the thick solid arrow M1 from the amount of microwaves indicated by the thin solid arrow M4 (M1). -M4). Therefore, the amount of microwaves output to the second output unit 132 is the amount (M1 + M2-M4) obtained by adding the amount of microwaves indicated by the thick solid arrow M2 to the amount of microwaves propagating from the second coupling point P2. Become.

Even in consideration of this, the amount of microwaves (M1 + M2-M4) output to the second output unit 132 is much larger than the amount of microwaves (M3) output to the first output unit 131. Therefore, the microstrip line 13 outputs most of the microwaves radiated counterclockwise from the cross opening 11 by the reflected waves propagating along the arrow 31 to the second output unit 132. On the other hand, the microstrip line 13 outputs most of the microwaves radiated clockwise from the cross opening 11 by the traveling wave propagating along the arrow 30 to the first output unit 131.

The amount of microwaves radiated from the cross opening 11 relative to the amount of microwaves propagating through the waveguide 3 is determined by the shape and dimensions of the waveguide 3 and the cross opening 11. For example, when set to the above shape and dimensions, the amount of microwaves radiated from the cross opening 11 relative to the amount of microwaves propagating through the waveguide 3 is about 1/10000 (about −50 dB).

Next, in the present embodiment, the reason why the total distance between the first transmission line 13a and the second transmission line 13b, which are farther from the pipe axis L1 than the parallel line L4, is set to 1/2 of the _{effective length λ re.} explain.

FIG. 7 is a diagram for explaining the direction and amount of microwaves propagating through the microstrip line 13 and changing with the passage of time. 7 (a) to 7 (d) are diagrams showing a state in which a time of t1 / 2 has elapsed from (a) to (d) of FIG. 6, respectively.

Although the description is omitted above, the magnetic field distribution 3d moves in the waveguide 3 in the microwave transmission direction A1 with the passage of time. Therefore, as shown in FIGS. 7A to 7D, the magnetic fields indicated by the broken line arrows B12, B23, B34, and B41 excite the first elongated hole 11e and the second elongated hole 11f. As a result, the circularly polarized microwaves radiated outside the waveguide 3 are coupled to the microstrip line 13.

Here, the region where the perpendicular line L2 and the parallel line L4 intersect with the microstrip line 13 in a plan view is referred to as a coupling region. The third coupling point P3 is approximately the center of the coupling region where the perpendicular line L2 and the microstrip line 13 intersect. The fourth coupling point P4 is substantially the center of the coupling region where the parallel line L4 and the first transmission line 13a intersect. The fifth coupling point P5 is substantially the center of the coupling region where the parallel line L4 and the second transmission line 13b intersect.

At the time t = t0 + t1 / 2 shown in FIG. 7A, the magnetic field indicated by the broken line arrow B12 excites the cross opening 11, and the microwave indicated by the thick solid line arrow M11 is generated at the third coupling point P3. This microwave propagates on the microstrip line 13 toward the fifth coupling point P5.

At the time t = t0 + t1 + t1 / 2 shown in FIG. 7B, the magnetic field indicated by the broken line arrow B23 excites the cross opening 11. At the fifth coupling point P5, the microwave indicated by the thick solid arrow M12a is generated, and at the fourth coupling point P4, the microwave indicated by the thin solid arrow M12b is generated. The reason for reducing the thickness of the solid arrow M12b is the same as the reason for reducing the thickness of the solid arrow M3 described above.

When the effective propagation time of the microwave by the microstrip line 13 between the third coupling point P3 and the fifth coupling point P5 is set to time t1, it occurs at the third coupling point P3 at the time shown in FIG. 7A. The microwave propagates to the fifth coupling point P5 at the time shown in FIG. 7 (b). That is, at the time shown in FIG. 7B, the microwave indicated by the thick solid arrow M11 and the microwave indicated by the thick solid arrow M12a are generated at the fifth coupling point P5.

Therefore, the two microwaves are added and propagated along the microstrip line 13 toward the second output unit 132, and are output to the second output unit 132 after a lapse of a predetermined time. In order to set the effective propagation time to the time t1, in the present embodiment, the distance of the first transmission line 13a farther from the pipe axis L1 than the parallel line L4 is set to 1/4 of the _{effective length λ re.} .. The microwave indicated by the thin solid arrow M12b generated at the fourth coupling point P4 propagates along the microstrip line 13 toward the first output unit 131, and is output to the first output unit 131 after a lapse of a predetermined time.

At the time t = t0 + T / 2 + t1 / 2 shown in FIG. 7 (c), the magnetic field indicated by the broken line arrow B34 excites the cross opening 11, and the microwave indicated by the thin solid line arrow M13b is generated at the third coupling point P3. This microwave propagates along the microstrip line 13 toward the first output unit 131. The reason for reducing the thickness of the solid line arrow M13b is the same as the reason for reducing the thickness of the solid line arrow M3 described above.

At the time t = t0 + T / 2 + t1 + t1 / 2 shown in FIG. 7D, the magnetic field indicated by the broken line arrow B41 excites the cross opening 11. At the fifth coupling point P5, the microwave indicated by the thin solid arrow M14b is generated, and at the fourth coupling point P4, the microwave indicated by the thick solid arrow M14a is generated. The microwave indicated by the thin solid arrow M14b propagates on the microstrip line 13 toward the third coupling point P3. The reason for reducing the thickness of the solid line arrow M14b is the same as the reason for reducing the thickness of the solid line arrow M3 described above.

The microwave indicated by the thick solid arrow M14a propagates on the microstrip line 13 toward the third coupling point P3. When the effective propagation time of the microwave by the microstrip line 13 between the third coupling point P3 and the fourth coupling point P4 is set to time t1, it occurs at the third coupling point P3 at the time shown in FIG. 7 (c). The microwave propagates to the fourth coupling point P4 at the time shown in FIG. 7 (d).

That is, at the time shown in FIG. 7D, the microwave indicated by the thin solid arrow M13b and the microwave indicated by the thick solid arrow M14a are generated at the fourth coupling point P4. In order to set the effective propagation time to the time t1, in the present embodiment, the distance of the second transmission line 13b farther from the pipe axis L1 than the parallel line L4 is set to 1/4 of the _{effective length λ re.} ..

That is, the total distance between the first transmission line 13a and the second transmission line 13b, which are farther from the pipe axis L1 than the parallel line L4, is set to 1/2 of the _{effective length λ re.} The microwave indicated by the thin solid arrow M13b propagates in the opposite direction to the microwave indicated by the thick solid arrow M14a. Therefore, the microwave indicated by the thin solid line arrow M13b is canceled and disappears, and is not output to the first output unit 131.

At time t = t0 + T + t1 / 2, the magnetic field indicated by the broken line arrow B12 excites the cross opening 11 as at time t = t0 + t1 / 2 shown in FIG. 7A. In this case, the microwave indicated by the thin solid arrow M14b, which was not described in the case of the time shown in FIG. 7A, exists on the microstrip line 13.

The microwave indicated by the thin solid arrow M14b propagates to the third coupling point P3 at time t = t0 + T + t1 / 2. The microwave indicated by the thin solid arrow M14b propagates in the opposite direction to the microwave indicated by the thick solid arrow M11 and the thick solid arrow M14a. Therefore, the microwave indicated by the thin solid line arrow M14b is canceled and disappears, and is not output to the first output unit 131.

Strictly speaking, the amount of microwaves propagating from the third coupling point P3 at time t = t0 + t1 / 2 is the difference between the amount of microwaves indicated by the thick solid arrows M11 and M14a and the amount of microwaves indicated by the thin solid arrow M14b. (M11 + M14a-M14b). Therefore, the amount of microwaves output to the second output unit 132 is the amount obtained by adding the amount of microwaves indicated by the thick solid arrow M12a to the amount of microwaves propagating from the third coupling point P3 (M11 + M12a + M14a-M14b). Become.

Even in consideration of this, the amount of microwaves (M11 + M12a + M14a-M14b) output to the second output unit 132 is much larger than the amount of microwaves (M12b) output to the first output unit 131. Therefore, the microstrip line 13 outputs most of the microwaves radiated counterclockwise from the cross opening 11 by the reflected waves propagating in the direction of the arrow 31 to the second output unit 132. On the other hand, the microstrip line 13 outputs most of the microwaves radiated clockwise from the cross opening 11 by the traveling wave propagating in the direction of the arrow 30 to the first output unit 131.

The directional coupler 5 has a cross opening 11 that emits circularly polarized microwaves and is arranged at a position that does not intersect the tube axis L1 of the waveguide 3 in a plan view. With this configuration, the rotation directions of the circularly polarized microwaves radiated from the cross opening 11 are opposite to each other for the traveling wave and the reflected wave. By utilizing the difference in the rotation direction of the circularly polarized microwaves, the traveling wave and the reflected wave can be detected separately.

In the directional coupler 5, the first transmission line 13a includes a first straight line portion 13aa, and the second transmission line 13b includes a second straight line portion 13ba. With this configuration, the number of places where the microstrip line 13 bends can be reduced as compared with the conventional case. The need to bend the microstrip line 13 at a right angle can be eliminated. The bent portion of the microstrip line 13 can be separated from the vertical region of the cross opening 11. As a result, the traveling wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 5, the first transmission line 13a and the second transmission line 13b are connected to each other outside the rectangular region E1 in a plan view and at a position away from the pipe axis L1. With this configuration, the bent portion of the microstrip line 13 can be further separated from the vertical region of the cross opening 11. The first straight line portion 13aa and the second straight line portion 13ba can be made longer, and the current flow in the microstrip line 13 can be suppressed from being obstructed. As a result, the traveling wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 5, the first straight line portion 13aa intersects the first elongated hole 11e at a position closer to the opening tip portion 11ea than the opening central portion 11c in a plan view. The second straight line portion 13ba intersects the second elongated hole 11f at a position closer to the opening tip portion 11fa than the opening central portion 11c in a plan view. Usually, a stronger magnetic field is generated around the opening tips 11ea and 11fa than around the opening center 11c. With the above configuration, a stronger magnetic field is coupled to the microstrip line 13. Therefore, the current flowing through the microstrip line 13 becomes larger. As a result, the traveling wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 5, the first straight line portion 13aa is orthogonal to the first elongated hole 11e in a plan view. With this configuration, the transmission direction of the microwave indicated by the solid arrow M1 generated at the first coupling point P1 is made the same as the rotation direction 32 of the microwave radiated from the cross opening 11. As a result, the amount of microwaves indicated by the solid arrow M1 can be further increased.

The transmission direction of the microwave indicated by the solid arrow M3 generated at the first coupling point P1 is reversed from the rotation direction 32 of the microwave radiated from the cross opening 11. As a result, the amount of microwaves indicated by the solid arrow M3 can be made smaller. As a result, the traveling wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 5, the second straight line portion 13ba is orthogonal to the second elongated hole 11f in a plan view. With this configuration, the transmission direction of the microwave indicated by the solid arrow M2 generated at the second coupling point P2 is made the same as the rotation direction 32 of the microwave radiated from the cross opening 11. As a result, the amount of microwaves indicated by the solid arrow M2 can be further increased.

The transmission direction of the microwave indicated by the solid arrow M4 generated at the second coupling point P2 is reversed from the rotation direction 32 of the microwave radiated from the cross opening 11. As a result, the amount of microwaves indicated by the solid arrow M4 can be made smaller. As a result, the traveling wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 5, the microstrip line 13 has a first straight line portion 13aa, a second straight line portion 13ba, a third straight line portion 13ab, and a fourth straight line portion 13bb. The first straight line portion 13aa and the third straight line portion 13ab adjacent to each other are connected so as to form an obtuse angle. The second straight line portion 13ba and the fourth straight line portion 13bb adjacent to each other are connected so as to form an obtuse angle.

With this configuration, it is possible to reduce the number of places where the microstrip line 13 bends at a right angle. As a result, it is possible to suppress the obstruction of the current flow in the coupling line. As a result, the traveling wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 5, the total distance between the first transmission line 13a and the second transmission line 13b, which are farther from the tube axis L1 than the virtual straight line L3, is set to 1/4 of the _{effective length λ re.} With this configuration, the traveling wave and the reflected wave can be separated and detected with higher accuracy. The total distance, if it is set to approximately 1/4 of the effective length lambda _re, need not necessarily be set to 1/4 of the effective length lambda _re.

In the directional coupler 5, the total distance between the first transmission line 13a and the second transmission line 13b, which are farther from the pipe axis L1 than the parallel line L4, is set to 1/2 of the _{effective length λ re.} With this configuration, the traveling wave and the reflected wave can be separated and detected with higher accuracy. The total distance, if it is set to approximately 1/2 of the effective length lambda _re, need not necessarily be set to 1/2 of the effective length lambda _re.

As shown in FIG. 4, in the present embodiment, one end of the first transmission line 13a and one end of the second transmission line 13b are connected so as to form a right angle. However, this disclosure is not limited to this. It suffices that one end of the first transmission line 13a is connected to one end of the second transmission line 13b at a position outside the region of the cross opening 11 in a plan view. In this region, the influence of the magnetic field is large.

8A to 8D are plan views showing first modification to sixth modification of the microstrip line 13, respectively. As shown in FIG. 8A, the first transmission line 13a and the second transmission line 13b are bent so that the connection point between one end of the first transmission line 13a and one end of the second transmission line 13b is separated from the opening central portion 11c. You may be doing it.

As shown in FIG. 8B, the first transmission line 13a and the second transmission line 13b are bent so that the connection point between one end of the first transmission line 13a and one end of the second transmission line 13b approaches the opening central portion 11c. You may be doing it. As shown in FIG. 8C, the first transmission line 13a and the second transmission line 13b are curved so that the connection point between one end of the first transmission line 13a and one end of the second transmission line 13b approaches the opening central portion 11c. You may be doing it.

In the present embodiment, the first straight line portion 13aa and the second straight line portion 13ba correspond to the first crossing line portion and the second crossing line portion, respectively. However, this disclosure is not limited to this. As shown in FIG. 8D, the first crossing line portion and the second crossing line portion may be the arc-shaped portion 13ac and the arc-shaped portion 13bc, respectively.

In the present embodiment, the third straight line portion 13ab and the fourth straight line portion 13bb are parallel to the perpendicular line L2. However, this disclosure is not limited to this. As shown in FIG. 8E, the third straight line portion 13ab and the fourth straight line portion 13bb may be parallel to the parallel line L4.

In the present embodiment, the first transmission line 13a and the second transmission line 13b have a plurality of linear portions. However, this disclosure is not limited to this. As shown in FIG. 8F, both the first transmission line 13a and the second transmission line 13b may be composed of a single straight line portion.

In the present embodiment, the cross opening 11 is formed line-symmetrically with respect to the perpendicular line L2. The perpendicular line L2 is orthogonal to the pipe axis L1 and passes through the central portion 11c of the opening. However, this disclosure is not limited to this. The cross opening 11 does not have to be formed line-symmetrically with respect to the perpendicular line L2. For example, the first elongated hole 11e and the second elongated hole 11f may intersect at positions deviated from the central portion in the longitudinal direction of each. The length of the first elongated hole 11e and the length of the second elongated hole 11f may be different from each other.

In these cases, the opening intersection where the first elongated hole 11e and the second elongated hole 11f intersect is displaced from the opening central portion 11c. The cross opening 11 may be formed line-symmetrically with respect to a straight line slightly inclined with respect to the perpendicular line L2 in a plan view.

Hereinafter, the configuration of the microwave heating device 10 according to the present embodiment will be described with reference to FIG. 9. As shown in FIG. 9, the microwave heating device 10 includes a heating chamber 1, a microwave generation unit 2, a waveguide 3, and a microwave radiation unit 4.

The heating chamber 1 accommodates the object to be heated. The microwave generation unit 2 generates microwaves. The waveguide 3 propagates the microwave generated by the microwave generating unit 2. The microwave emitting unit 4 is arranged below the bottom surface 1a of the heating chamber 1 and radiates the microwave propagating in the waveguide 3 to the heating chamber 1. The directional coupler 5 is arranged on the wide surface 3a (see FIGS. 1 and 2) of the waveguide 3 between the microwave generation unit 2 and the microwave radiation unit 4.

The directional coupler 5 detects the detection signal 5a according to the traveling wave propagating in the waveguide 3 from the microwave generation unit 2 toward the microwave radiation unit 4. The directional coupler 5 detects the detection signal 5b according to the reflected wave propagating in the waveguide 3 from the microwave emitting unit 4 toward the microwave generating unit 2. The directional coupler 5 transmits the detection signals 5a and 5b to the control unit 6.

The control unit 6 receives the signal 8 in addition to the detection signals 5a and 5b. The signal 8 includes the heating conditions set by the input unit (not shown) of the microwave heating device 10, the weight of the object to be heated detected by the sensor (not shown), and the amount of steam. The control unit 6 controls the drive power source 7 and the motor 9 based on the detection signals 5a and 5b and the signal 8. The drive power source 7 supplies electric power for generating microwaves to the microwave generation unit 2. The motor 9 rotates the microwave radiation unit 4. In this way, the microwave heating device 10 heats the object to be heated housed in the heating chamber 1 by the microwave supplied to the heating chamber 1.

As the object to be heated is heated, the object to be heated physically changes. The amount of reflected waves changes according to this physical change. By detecting the change in the amount of reflected waves using the directional coupler 5, the microwave heating device 10 can grasp the progress of heating of the object to be heated. The microwave heating device 10 can also grasp the change in the state in the object to be heated and the type and amount of the object to be heated. Therefore, according to the present embodiment, it is possible to provide a highly convenient microwave heating device.

The directional coupler according to the present disclosure is applicable to a consumer or commercial microwave heating device.

1 Heating chamber 1a Bottom surface 2 Microwave generator 3 Waveguide tube 3a Wide surface 3d Magnetic field distribution 4 Microwave radiator 5 Directional coupler 5a, 5b Detection signal 6 Control unit 7 Drive power supply 8 Signal 9 Motor 10 Microwave heating device 11 Cross opening 11c Opening center 11d Width 11e 1st slot 11ea, 11fa Opening tip 11f 2nd slot 11w Length 12 Printed circuit board 12a Board surface 12b Board back side 13 Microstrip line 13a 1st transmission line 13aa 1st straight line Part 13ab 3rd straight part 13ac, 13bc Arc-shaped part 13b 2nd transmission line 13ba 2nd straight part 13bb 4th straight part 14 Support part 15 1st detection circuit 16 2nd detection circuit 18 1st detection output part 18a, 19a Connector 19 2nd detection output part 20a Hole 30 Arrow 31 Arrow 131 1st output part 132 2nd output part 141, 142 Groove 201a Screw 202a Thread part E1 Rectangular area L1 Pipe axis L2 Vertical line L3 Virtual straight line L4 Parallel line P1 First connection point P2 2nd connection point P3 3rd connection point P4 4th connection point P5 5th connection point

Claims (9)

A directionality in which an opening arranged on the wall surface of the waveguide and a coupling line arranged outside the waveguide are provided to separate and detect a traveling wave and a reflected wave propagating in the waveguide. It ’s a coupler,
The opening has a first elongated hole and a second elongated hole that intersect each other and are arranged at positions that do not intersect the tube axis of the waveguide in a plan view.
The coupling line includes a first transmission line and a second transmission line.
The first transmission line has a first crossing line portion, and the first crossing line portion has an opening crossing portion where the first elongated hole and the second elongated hole intersect from one end of the pipe shaft in a plan view. As it approaches the vertical line orthogonal to the pipe axis, it extends away from the pipe axis and intersects the first elongated hole at a position farther from the pipe axis than the opening intersection.
The second transmission line has a second crossing line portion, and the second crossing line portion extends away from the pipe shaft as it approaches the perpendicular line from the other end of the pipe shaft in a plan view, and the opening thereof. It intersects with the second elongated hole at a position farther from the pipe axis than the intersection,
A directional coupler in which one end of the first transmission line is connected to one end of the second transmission line at a position outside the region of the opening in a plan view. A claim in which the first transmission line and the second transmission line are connected to each other outside a rectangular region circumscribing the opening in a plan view and at a position distant from the tube axis from the rectangular region. Item 2. The directional coupler according to item 1. At least one of the first crossing line portion and the second crossing line portion intersects the corresponding first elongated hole or the second elongated hole in a plan view at a position closer to the opening tip portion than the opening intersection. , The directional coupler according to claim 1. The directional coupler according to claim 1, wherein at least one of the first crossing line portion or the second crossing line portion is orthogonal to the corresponding first elongated hole or the second elongated hole in a plan view. The coupling line has a plurality of straight line portions including the first crossing line portion and the second crossing line portion, and two straight portions adjacent to each other among the plurality of straight line portions form an obtuse angle. The directional coupler according to claim 1, which is connected. The plurality of straight line portions include a straight line portion connecting the other end of the first crossing line portion and the first output portion, and a straight line portion connecting the second crossing line portion and the second output portion. The directional coupler according to claim 5. Virtually passing through a first connection point which is an intersection of the first intersection line portion and the first elongated hole and a second coupling point which is an intersection of the second intersection line portion and the second elongated hole in a plan view. The directional coupler according to claim 1, wherein the total distance between the first transmission line and the second transmission line, which is farther from the pipe axis than the straight line, is set to 1/4 of the effective length. The total distance between the first transmission line and the second transmission line, which passes through the opening intersection in a plan view and is farther from the pipe axis than the parallel line parallel to the pipe axis, is 1 of the effective length. The directional coupler according to claim 1, which is set to / 2. A microwave heating device including the directional coupler according to claim 1.

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