WO2019203170A1 - Directional coupler and microwave heating device provided with same - Google Patents

Abstract

This directional coupler is provided with an opening part and a coupling line. The opening part has a first long hole and a second long hole which, in a planar view, are disposed at positions not intersecting with the tube axis of a waveguide tube but which themselves intersect with each other. The coupling line is provided with a first transmission line and a second transmission line. The first transmission line has a first intersection-line part. The first intersection-line part is formed, in a planar view, from one end of the tubular axis, passes an opening intersection part where the first and second long holes intersect with each other, extends in such a manner as to increasingly separate from the tubular axis with a decrease in distance to a perpendicular line orthogonal to the tubular axis, and intersects with the first long hole at a position further apart from the tubular axis as compared with the opening intersection part. The second transmission line has a second intersection-line part. The second intersection-line part, in a planar view, extends in such a manner as to increasingly separate from the tubular axis with a decrease in distance from the other end of the tubular axis toward the perpendicular line, and intersects with the second long hole at a position further apart from the tubular axis as compared with the opening intersection part. The first transmission line and the second transmission line are connected to each other, in a planar view, at a position outside the range of the opening part.

Description

Directional coupler and microwave heating apparatus including the same

The present disclosure relates to a directional coupler that detects a power level of a microwave propagating through a waveguide, and a microwave heating apparatus including the directional coupler.

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

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

According to the directional coupler of Patent Document 1, the rotational direction of the circularly polarized traveling wave radiated from the opening is opposite to that of the circularly polarized reflected wave. Utilizing such a difference in the rotation direction of the circularly polarized microwave, the traveling wave and the reflected wave can be separated and detected.

Japanese Patent No. 6176540

However, the conventional directional coupler described above still has room for improvement in terms of separating and detecting the traveling wave and the reflected wave more accurately.

Therefore, an object of the present disclosure is to provide a directional coupler that can separate and detect a traveling wave and a reflected wave and a microwave heating apparatus including the directional coupler.

A directional coupler according to an aspect of the present disclosure includes an opening disposed on a wall surface of a waveguide and a coupling line disposed outside the waveguide, and a traveling wave and a reflection propagating through the waveguide Separate and detect waves.

The opening has a first long hole and a second long hole that are arranged at positions not intersecting with the tube axis of the waveguide in plan view. The coupled line includes a first transmission line and a second transmission line.

The first transmission line has a first intersecting line portion. The first intersecting line portion extends from one end of the tube axis in plan view through an opening intersecting portion where the first elongated hole and the second elongated hole intersect, and away from the tube axis as approaching a perpendicular perpendicular to the tube axis. And intersects the first slot at a position farther from the tube axis than the opening intersection.

The second transmission line has a second intersection line portion. The second intersecting line portion extends away from the tube axis as it approaches the perpendicular from the other end of the tube axis in plan view, and intersects the second elongated hole at a position further away from the tube axis than the opening intersecting portion. .

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

According to the directional coupler of this aspect, 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 with the printed board 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 that circularly polarized microwaves are radiated from the cross aperture. FIG. 6 is a diagram for explaining the direction and amount of the microwave propagating through the microstrip line and changing with time. FIG. 7 is a diagram for explaining the direction and amount of the microwave that propagates through the microstrip line and changes with 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 diagram of the microwave heating apparatus according to the embodiment.

The present inventors have earnestly studied to detect and detect traveling waves and reflected waves more accurately, and as a result, have obtained the following knowledge.

In a conventional directional coupler, a coupling line is configured by connecting 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 as a single line. Is done. With this configuration, the influence of the impedance of the load connected to the waveguide can be relaxed, and the traveling wave and the reflected wave can be accurately separated.

The inventors of the present invention concentrate the magnetic field at a point where the coupled line bends at a right angle (or an acute angle), obstructs the flow of current (microwave) in the coupled line, and separates the traveling wave from the reflected wave. It has been found that it affects. The present inventors have found that in the conventional directional coupler, there are many portions where the coupled line is bent at a right angle, which greatly affects the degree of separation between the traveling wave and the reflected wave. The inventors of the present invention have suppressed the current flow in the coupled line from being hindered by moving the portion where the coupled line is bent away from the vertical region of the opening that is strongly affected by the magnetic field. I found out.

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

A directional coupler according to a first aspect of the present disclosure includes an opening disposed on a wall surface of a waveguide, and a traveling wave propagating through the waveguide, including a coupling line disposed outside the waveguide. And the reflected wave are detected separately.

The opening has a first long hole and a second long hole that are arranged at positions not intersecting with the tube axis of the waveguide in plan view. The coupled line includes a first transmission line and a second transmission line.

The first transmission line has a first intersecting line portion. The first intersecting line portion extends from one end of the tube axis in plan view through an opening intersecting portion where the first elongated hole and the second elongated hole intersect, and away from the tube axis as approaching a perpendicular perpendicular to the tube axis. And intersects the first slot at a position farther from the tube axis than the opening intersection.

The second transmission line has a second intersection line portion. The second intersecting line portion extends away from the tube axis as it approaches the perpendicular from the other end of the tube axis in plan view, and intersects the second elongated hole at a position further away from the tube axis than the opening intersecting portion. .

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

In the directional coupler according to the second aspect of the present disclosure, in addition to the first aspect, the first transmission line and the second transmission line are outside a 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 according to the third aspect of the present disclosure, in addition to the first aspect, at least one of the first intersecting line part or the second intersecting line part corresponds to the first long hole or the second corresponding in plan view. It intersects the long hole at a position closer to the opening tip than the opening intersection.

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

In the directional coupler according to the fifth aspect of the present disclosure, in addition to the first aspect, the coupled line includes a plurality of straight line portions including a first intersecting line portion and a second intersecting line portion. Two straight portions adjacent to each other among the plurality of straight portions are connected to form an obtuse angle.

In the directional coupler according to the sixth aspect of the present disclosure, in addition to the fifth aspect, the plurality of linear portions includes a linear portion that connects the other end of the first intersecting line portion and the first output portion, A straight line portion connecting the two intersecting line portions and the second output portion.

In the directional coupler according to the seventh aspect of the present disclosure, in addition to the first aspect, a first coupling point and a second intersecting line portion that are intersections of the first intersecting line portion and the first oblong hole in plan view. The total distance between the first transmission line and the second transmission line that are further away from the tube axis than the virtual straight line that passes through the second coupling point that is the intersection of the second long hole and the second long hole is set to 1/4 of the effective length. The

In the directional coupler according to the eighth aspect of the present disclosure, in addition to the first aspect, the first that is farther from the tube axis than a parallel line that passes through the opening intersection and is parallel to the tube axis in plan view. The total distance between the transmission line and the second transmission line is set to ½ of the effective length.

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

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

FIG. 1 is a perspective view of a directional coupler 5 according to an 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 in the directional coupler 5.

As shown in FIGS. 1 to 3, the directional coupler 5 is disposed on the wall surface of the waveguide 3 that transmits microwaves. The waveguide 3 is a rectangular waveguide. The cross section orthogonal to the tube axis L1 of the waveguide 3 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 board 12, and a support portion 14. The cross opening 11 is an X-shaped opening disposed on the wide surface (Wide Plane) 3 a of the waveguide 3. The printed circuit board 12 is disposed outside the waveguide 3 so as to face the cross opening 11. The support unit 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 disposed at a position that does not intersect the tube axis L1 of the waveguide 3 in plan view. The opening center portion 11c of the cross opening 11 is disposed away from the tube axis L1 of the waveguide 3 by a dimension D1 in plan view. The dimension D1 is, for example, ¼ of the width of the waveguide 3. The cross opening 11 radiates the microwave propagating through the waveguide 3 toward the printed circuit board 12 as a circularly polarized microwave.

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 through the waveguide 3, and the power level of the circularly polarized microwave radiated from the cross opening 11. It is determined according to conditions such as.

For example, the width of the waveguide 3 is 100 mm, the height is 30 mm, the thickness of the wall surface of the waveguide 3 is 0.6 mm, the maximum power level of the microwave propagating through 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 long hole 11e and a second long hole 11f that intersect each other. The opening center part 11c of the cross opening 11 coincides with the opening intersection where the first long hole 11e and the second long hole 11f intersect. The cross opening 11 is formed symmetrically with respect to the perpendicular L2. The perpendicular L2 is orthogonal to the tube axis L1 and passes through the opening center portion 11c.

In the present embodiment, the first long hole 11e and the second long hole 11f intersect at an angle of 90 degrees. However, the present disclosure is not limited to this. The first long hole 11e and the second long 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 opening 11 radiates linearly polarized microwaves.

If the opening center portion 11c is slightly deviated from the tube axis L1, the electric field rotates. However, when the opening center portion 11c is close to the tube axis L1 (as the dimension D1 is close to 0 mm), an distorted electric field is generated. In this case, the cross opening 11 radiates elliptically polarized microwaves.

In the present embodiment, the dimension D1 is set to about ¼ of the width of the waveguide 3. In this case, a substantially circular electric field is generated. The cross opening 11 emits a substantially circularly polarized microwave. For this reason, the rotation direction of the circularly polarized microwave becomes clearer. As a result, the traveling wave and the reflected wave can be separated and detected with high accuracy.

The printed circuit board 12 has a substrate back surface 12b facing the cross opening 11 and a substrate surface 12a opposite to the substrate back surface 12b. The substrate surface 12a has a copper foil (not shown) formed as an example of a microwave reflecting member so as to cover the entire substrate surface 12a. This copper foil prevents the circularly polarized microwave 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 coupled line is disposed on the back surface 12b of the substrate. The microstrip line 13 is constituted by a transmission line having a characteristic impedance of approximately 50Ω, for example. The microstrip line 13 is arranged so as to surround the opening center portion 11 c of the cross opening 11.

Hereinafter, the effective length λ _re of the microstrip line 13 will be described. When 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 dielectric constant of the printed circuit board is ε _r , the effective length λ of the microstrip line 13 _re is expressed by the following equation. The effective length λ _re is the wavelength of the electromagnetic wave propagating through the microstrip line 13.

Specifically, the microstrip line 13 includes a first transmission line 13a and a second transmission line 13b. The 1st transmission line 13a has the 1st straight part 13aa which is an example of the 1st crossing line part. The first straight portion 13aa intersects the first long hole 11e at a position farther from the tube axis L1 than the opening center portion 11c in plan view. The first straight portion 13aa extends away from the tube axis L1 as it approaches the vertical line L2.

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

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

The first straight portion 13aa is orthogonal to the first long hole 11e in plan view. The second straight portion 13ba intersects the second elongated hole 11f at a position closer to the opening tip portion 11fa than the opening center portion 11c in plan view. The second straight portion 13ba is orthogonal to the second long hole 11f in 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 a region overlapping the cross opening 11 in plan view. One end of the first straight portion 13aa is connected to one end of the second straight portion 13ba outside the rectangular region E1 circumscribing the cross opening 11.

The first coupling point P1 is a point where the first straight portion 13aa and the first long hole 11e intersect each other in plan view. The second coupling point P2 is a point where the second straight portion 13ba and the second long hole 11f intersect each other in plan view. A 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 that are further away from the tube axis L1 than the virtual straight line L3 is set to ¼ of the effective length λ _re .

A line passing through the opening center 11c and parallel to the tube axis L1 in plan view 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 that are further from the tube axis L1 than the parallel line L4 is set to ½ of the effective length λ _re .

The first transmission line 13a includes a third straight part 13ab that connects the other end of the first straight part 13aa and the first output part 131. The first straight part 13aa and the third straight part 13ab are connected 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 portion 132. The second straight portion 13ba and the fourth straight portion 13bb are connected to form an obtuse angle (for example, 135 degrees). The third straight portion 13ab and the fourth straight portion 13bb are disposed in parallel to the perpendicular line L2.

The first output part 131 and the second output part 132 are arranged outside the support part 14 (see FIGS. 1 and 2) in 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 level of the microwave signal as a control signal. The 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 level of the microwave signal as a control signal.

In the present embodiment, each of the first detection circuit 15 and the second detection circuit 16 includes a smoothing circuit (not shown) configured by 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 substrate back surface 12b. 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 being screwed to the support portion 14 with screws 201a, 201b, 201c, 201d (see FIG. 1) through the holes 20a, 20b, 20c, 20d.

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

The support portion 14 has conductivity and is disposed 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 microwave 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 portion 13ab and the fourth straight portion 13bb of the microstrip line 13 pass. With this configuration, the first output unit 131 and the second output unit 132 of the microstrip line 13 can be disposed outside the support unit 14. The grooves 141 and 142 function as an extraction unit for extracting the microwave signal propagating through the microstrip line 13 to the outside of the support unit 14. The grooves 141 and 142 can be formed by recessing the flange portion of the support portion 14 so as to be separated from the printed circuit board 12.

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

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

First, the principle of circularly polarized microwaves being radiated from the cross opening 11 will be described with reference to FIG. In FIG. 5, the magnetic field distribution 3d generated in the waveguide 3 is indicated 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 time.

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

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

By repeating these states sequentially, circularly polarized microwaves rotating counterclockwise (microwave rotation direction 32) are radiated from the cross opening 11 to the outside of the waveguide 3.

Here, if 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 microwave rotating counterclockwise is radiated out of the waveguide 3 from the cross opening 11.

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

The circularly polarized microwave radiated out of the waveguide 3 is coupled to the microstrip line 13 facing the cross opening 11. The microstrip line 13 outputs most of the microwave 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 microwave radiated from the cross opening 11 by the reflected wave propagating along the arrow 31 to the second output unit 132. Thereby, a traveling wave and a 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 the microwave that propagates through the microstrip line 13 and changes over 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 the gap. However, for the sake of convenience, it is assumed here that there is no time delay.

Here, a region where the cross opening 11 and the microstrip line 13 intersect in 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 long hole 11e and the microstrip line 13 intersect. The second coupling point P2 is substantially the center of the coupling region where the second long hole 11f and the microstrip line 13 intersect.

In FIG. 6, the amount of microwave propagating through the microstrip line 13 (current flowing through the linkage of magnetic fields) is expressed by the thickness of the solid arrow line. That is, the line is thick when the amount of microwave propagating through the microstrip line 13 is large, and the line is thin when the amount of microwave propagating through the microstrip line 13 is small.

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

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

When the effective propagation time of the microwaves 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. The microwave propagates to the second coupling point P2 at the time shown in FIG. That is, at the time shown in FIG. 6B, the microwave indicated by the solid line arrow M1 and the microwave indicated by the solid line arrow M2 are generated at the second coupling point P2.

Therefore, the two microwaves are added and propagated through the microstrip line 13 toward the second output unit 132, and are output to the second output unit 132 after a predetermined time has elapsed. In the present embodiment, since the effective propagation time is set to time t1, the total distance between the first transmission line 13a and the second transmission line 13b that are further from the tube axis L1 than the virtual straight line L3 is the effective length λ _re Is set to 1/4. With this configuration, the microstrip line 13 can be easily designed.

At time t = t0 + T / 2 shown in FIG. 6C, the magnetic field indicated by the broken line arrow B3 excites the first long hole 11e of the cross opening 11, and the first coupling point P1 has a micro indicated by a thin solid line arrow M3. A wave is generated. The microwave propagates through the microstrip line 13 toward the first output unit 131, and is output to the first output unit 131 after a predetermined time has elapsed.

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

At the time shown in FIG. 6 (a), 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. For this reason, the energy of the microwave indicated by the solid line 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 almost opposite to the rotation direction of the microwave radiated from the cross opening 11. For this reason, the energy of the coupled microwave is reduced. Therefore, the amount of microwave indicated by the solid line arrow M3 is smaller than the amount of microwave indicated by the solid line arrow M1.

At time t = t0 + T / 2 + t1 shown in FIG. 6 (d), the magnetic field indicated by the broken line arrow B4 excites the second long hole 11f of the cross opening 11, and the second coupling point P2 has the micro indicated by the thin solid line arrow M4. A wave is generated. 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, similarly to the time t = t0 shown in FIG. 6A, the magnetic field indicated by the broken-line arrow B1 excites the first long hole 11e of the cross opening 11. In this case, a microwave indicated by a thin solid arrow M4 not described in the case of the time shown in FIG.

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 line arrow M4 propagates in the opposite direction to the microwave indicated by the thick solid line arrow M1. For this reason, the microwave indicated by the solid line arrow M <b> 4 is canceled and disappears, and is not output to the first output unit 131.

Strictly speaking, the amount of microwave propagating from the first coupling point P1 at time t = t0 is the amount obtained by subtracting the amount of microwave indicated by the thin solid arrow M4 from the amount of microwave indicated by the thick solid arrow M1 (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 wave 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 microwave radiated from the cross opening 11 relative to the amount of microwave propagating through the waveguide 3 is determined by the shape and dimensions of the waveguide 3 and the cross opening 11. For example, when the shape and size are set as described above, the amount of microwave radiated from the cross opening 11 with respect to the amount of microwave propagating through the waveguide 3 is about 1/100000 (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 that are further away from the tube axis L1 than the parallel line L4 is set to ½ of the effective length λ _re. explain.

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

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

Here, a region where the perpendicular line L2 and the parallel line L4 intersect with the microstrip line 13 in plan view is referred to as a coupling region. The third coupling point P3 is substantially 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 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 through the microstrip line 13 toward the fifth coupling point P5.

At 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. A microwave indicated by a thick solid arrow M12a is generated at the fifth coupling point P5, and a microwave indicated by a thin solid arrow M12b is generated at the fourth coupling point P4. The reason for reducing the thickness of the solid line arrow M12b is the same as the reason for reducing the thickness of the solid line arrow M3 described above.

When the effective propagation time of the microwaves 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. The microwave propagates to the fifth coupling point P5 at the time shown in FIG. 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 through the microstrip line 13 toward the second output unit 132, and are output to the second output unit 132 after a predetermined time has elapsed. In order to set the effective propagation time to time t1, in the present embodiment, the distance of the first transmission line 13a that is further from the tube axis L1 than the parallel line L4 is set to ¼ of the effective length λ _re. . The microwave indicated by the thin solid arrow M12b generated at the fourth coupling point P4 propagates through the microstrip line 13 toward the first output unit 131, and is output to the first output unit 131 after a predetermined time has elapsed.

At time t = t0 + T / 2 + t1 / 2 shown in FIG. 7 (c), the magnetic field indicated by the broken arrow B34 excites the cross opening 11, and the microwave indicated by the thin solid 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 time t = t0 + T / 2 + t1 + t1 / 2 shown in FIG. 7 (d), the magnetic field indicated by the dashed arrow B41 excites the cross opening 11. A microwave indicated by a thin solid arrow M14b is generated at the fifth connection point P5, and a microwave indicated by a thick solid line arrow M14a is generated at the fourth connection point P4. The microwave indicated by the thin solid arrow M14b propagates through 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 line arrow M14a propagates through the microstrip line 13 toward the third coupling point P3. When the effective propagation time of the microwaves 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. The microwave propagates to the fourth coupling point P4 at the time shown in FIG.

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 time t1, in the present embodiment, the distance of the second transmission line 13b that is further away from the tube axis L1 than the parallel line L4 is set to ¼ of the effective length λ _re. .

That is, the total distance between the first transmission line 13a and the second transmission line 13b that are further away from the tube axis L1 than the parallel line L4 is set to ½ of the effective length _λre . The microwave indicated by the thin solid line arrow M13b propagates in the opposite direction to the microwave indicated by the thick solid line arrow M14a. For this reason, the microwave indicated by the thin solid arrow M13b is canceled and disappears, and is not output to the first output unit 131.

At time t = t0 + T + t1 / 2, similarly to time t = t0 + t1 / 2 shown in FIG. 7A, the magnetic field indicated by the broken line arrow B12 excites the cross opening 11. In this case, a microwave indicated by a thin solid arrow M14b that has not been described in the case of the time shown in FIG.

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 line arrow M14b propagates in the opposite direction to the microwave indicated by the thick solid line arrow M11 and the thick solid line arrow M14a. For this reason, the microwave indicated by the thin solid arrow M <b> 14 b is canceled and disappears, and is not output to the first output unit 131.

Strictly speaking, the amount of microwave propagating from the third coupling point P3 at the time t = t0 + t1 / 2 is the difference between the amount of microwave indicated by the thick solid arrows M11 and M14a and the amount of microwave indicated by the thin solid arrows M14b. (M11 + M14a−M14b). Accordingly, 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.

Considering 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 microwave radiated counterclockwise from the cross opening 11 to the second output unit 132 by the reflected wave propagating in the direction of the arrow 31. 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 radiates a circularly polarized microwave, which is disposed at a position not intersecting with the tube axis L1 of the waveguide 3 in plan view. With this configuration, the rotational direction of the circularly polarized microwave radiated from the cross opening 11 is reversed between the traveling wave and the reflected wave. The traveling wave and the reflected wave can be separated and detected by utilizing the difference in the rotation direction of the circularly polarized microwave.

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 portions 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 location where the microstrip line 13 bends 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 at a position outside the rectangular region E1 and away from the tube axis L1 in plan view. With this configuration, the portion where the microstrip line 13 is bent can be further separated from the vertical region of the cross opening 11. The first straight part 13aa and the second straight part 13ba can be made longer, and the current flow in the microstrip line 13 can be prevented from being hindered. 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 portion 13aa intersects the first long hole 11e at a position closer to the opening tip portion 11ea than the opening center portion 11c in plan view. The second straight portion 13ba intersects the second long hole 11f at a position closer to the opening tip portion 11fa than the opening center portion 11c in plan view. Usually, a stronger magnetic field is generated around the opening tip portions 11ea and 11fa than around the opening center portion 11c. With the above configuration, a stronger magnetic field is coupled to the microstrip line 13. For this reason, more current flows through the microstrip line 13. 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 portion 13aa is orthogonal to the first long hole 11e in plan view. With this configuration, the transmission direction of the microwave indicated by the solid line 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. Thereby, the amount of microwaves indicated by the solid line 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 to the rotation direction 32 of the microwave radiated from the cross opening 11. Thereby, the amount of microwaves indicated by the solid line arrow M3 can be further reduced. 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 portion 13ba is orthogonal to the second long hole 11f in plan view. With this configuration, the transmission direction of the microwave indicated by the solid arrow M <b> 2 generated at the second coupling point P <b> 2 is made the same as the rotation direction 32 of the microwave radiated from the cross opening 11. Thereby, the amount of microwaves indicated by the solid line 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 to the rotation direction 32 of the microwave radiated from the cross opening 11. Thereby, the amount of microwaves indicated by the solid line arrow M4 can be further reduced. 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 includes a first straight portion 13aa, a second straight portion 13ba, a third straight portion 13ab, and a fourth straight portion 13bb. The first straight line portion 13aa and the third straight line portion 13ab that are adjacent to each other are connected to form an obtuse angle. The second straight portion 13ba and the fourth straight portion 13bb adjacent to each other are connected so as to form an obtuse angle.

This configuration can reduce the number of portions that are bent at right angles in the microstrip line 13. Thereby, it can suppress that the flow of the electric current in a coupling line is inhibited. 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 that are further from the tube axis L1 than the virtual straight line L3 is set to ¼ of the effective length λ _re . With this configuration, traveling waves and reflected waves 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 that are further away from the tube axis L1 than the parallel line L4 is set to ½ of the effective length λ _re . With this configuration, traveling waves and reflected waves can be separated and detected with higher accuracy. The total distance is not necessarily set to ½ of the effective length λ _re as long as the total distance is set to approximately ½ of the effective length λ _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 to form a right angle. However, the present disclosure is not limited to this. One end of the first transmission line 13a only needs to be connected to one end of the second transmission line 13b at a position deviated from the region of the cross opening 11 in plan view. In this region, the influence of the magnetic field is large.

8A to 8D are plan views showing first to sixth modified examples 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 away from the opening center portion 11c. You may do 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 center portion 11c. You may do 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 center portion 11c. You may do it.

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

In the present embodiment, the third straight portion 13ab and the fourth straight portion 13bb are parallel to the perpendicular L2. However, the present disclosure is not limited to this. As shown in FIG. 8E, the third straight portion 13ab and the fourth straight 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, the present disclosure is not limited to this. As shown in FIG. 8F, each of 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 symmetrically with respect to the perpendicular L2. The perpendicular L2 is orthogonal to the tube axis L1 and passes through the opening center portion 11c. However, the present disclosure is not limited to this. The cross opening 11 may not be formed symmetrically with respect to the perpendicular L2. For example, the 1st long hole 11e and the 2nd long hole 11f may cross | intersect in the position which shifted | deviated from the center part of each longitudinal direction. The length of the first long hole 11e and the length of the second long 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 center portion 11c. The cross opening 11 may be formed in line symmetry with respect to a straight line slightly inclined with respect to the perpendicular L2 in plan view.

Hereinafter, the configuration of the microwave heating apparatus 10 according to the present embodiment will be described with reference to FIG. As shown in FIG. 9, the microwave heating apparatus 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 an object to be heated. The microwave generator 2 generates a microwave. The waveguide 3 propagates the microwave generated by the microwave generator 2. The microwave radiating unit 4 is disposed below the bottom surface 1 a of the heating chamber 1 and radiates the microwave propagating through the waveguide 3 to the heating chamber 1. A directional coupler 5 is disposed on the wide surface 3 a (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 5 a according to the traveling wave propagating through the waveguide 3 from the microwave generation unit 2 toward the microwave radiation unit 4. The directional coupler 5 detects the detection signal 5 b in accordance with the reflected wave propagating through the waveguide 3 from the microwave radiating unit 4 toward the microwave generating unit 2. The directional coupler 5 transmits detection signals 5 a and 5 b to the control unit 6.

Control unit 6 receives signal 8 in addition to detection signals 5a and 5b. The signal 8 includes a heating condition set by an input unit (not shown) of the microwave heating apparatus 10, a weight of an object to be heated, and an amount of steam detected by a sensor (not shown). The control unit 6 controls the drive power supply 7 and the motor 9 based on the detection signals 5a and 5b and the signal 8. The drive power supply 7 supplies power for generating a microwave to the microwave generation unit 2. The motor 9 rotates the microwave radiation unit 4. Thus, the microwave heating apparatus 10 heats the object to be heated accommodated 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 changes physically. The amount of reflected waves changes according to this physical change. By detecting a change in the amount of the reflected wave using the directional coupler 5, the microwave heating apparatus 10 can grasp the progress of heating of the object to be heated. The microwave heating apparatus 10 can also grasp the state change in the object to be heated and the type and amount of the object to be heated. Therefore, according to the present embodiment, a highly convenient microwave heating apparatus can be provided.

The directional coupler according to the present disclosure can be applied to consumer or commercial microwave heating devices.

DESCRIPTION OF SYMBOLS 1 Heating chamber 1a Bottom surface 2 Microwave generation part 3 Waveguide 3a Wide surface 3d Magnetic field distribution 4 Microwave radiation part 5 Directional coupler 5a, 5b Detection signal 6 Control part 7 Drive power supply 8 Signal 9 Motor 10 Microwave heating apparatus DESCRIPTION OF SYMBOLS 11 Cross opening 11c Opening center part 11d Width 11e 1st long hole 11ea, 11fa Opening front-end | tip part 11f 2nd long hole 11w Length 12 Printed circuit board 12a Board | substrate surface 12b Substrate back surface 13 Microstrip line 13a 1st transmission line 13aa 1st straight Part 13ab Third straight line part 13ac, 13bc Arc-shaped part 13b Second transmission line 13ba Second straight line part 13bb Fourth straight line part 14 Support part 15 First detection circuit 16 Second detection circuit 18 First detection output part 18a, 19a Connector 19 2nd detection output part 20a Hole 30 Arrow 31 Arrow 131 1st Force part 132 Second output part 141, 142 Groove 201a Screw 202a Screw part E1 Rectangular area L1 Pipe axis L2 Perpendicular L3 Virtual straight line L4 Parallel line P1 First connection point P2 Second connection point P3 Third connection point P4 Fourth connection point P5 5th attachment point

Claims (9)

1. Directionality for detecting separately a traveling wave and a reflected wave propagating through the waveguide, comprising an opening disposed on a wall surface of the waveguide and a coupling line disposed outside the waveguide. A combiner,
   The opening has a first elongated hole and a second elongated hole that intersect with each other and are disposed at positions that do not intersect with the tube axis of the waveguide in plan view,
   The coupling line includes a first transmission line and a second transmission line,
   The first transmission line has a first intersecting line portion, and the first intersecting line portion has an opening intersecting portion where the first elongated hole and the second elongated hole intersect from one end of the tube axis in plan view. And extending away from the tube axis as approaching a perpendicular perpendicular to the tube axis, intersecting the first slot at a position farther from the tube axis than the opening intersection,
   The second transmission line has a second intersecting line portion, and the second intersecting line portion extends away from the tube axis as it approaches the perpendicular from the other end of the tube shaft in plan view, and the opening Intersects the second oblong hole at a position farther from the tube axis than the intersection,
   One end of the first transmission line is a directional coupler connected to one end of the second transmission line at a position deviating from the opening region in plan view.
2. 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 farther from the tube axis than the rectangular region. Item 4. A directional coupler according to item 1.
3. At least one of the first intersecting line portion or the second intersecting 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 than the opening intersecting portion. The directional coupler according to claim 1.
4. The directional coupler according to claim 1, wherein at least one of the first intersecting line portion or the second intersecting line portion is orthogonal to the corresponding first elongated hole or the second elongated hole in a plan view.
5. The coupling line has a plurality of linear portions including the first intersecting line portion and the second intersecting line portion, and two adjacent linear portions among the plurality of linear portions form an obtuse angle. The directional coupler according to claim 1, which is connected.
6. The plurality of straight line portions include a straight line portion that connects the other end of the first intersecting line portion and the first output portion, and a straight line portion that connects the second intersecting line portion and the second output portion. The directional coupler according to claim 5.
7. In plan view, it passes through a first coupling point that is an intersection between the first intersecting line portion and the first elongated hole, and a second coupling point that is an intersection between the second intersecting line portion and the second elongated hole. 2. The directional coupler according to claim 1, wherein a total distance between the first transmission line and the second transmission line which are further away from the tube axis than a straight line is set to ¼ of an effective length.
8. The total distance between the first transmission line and the second transmission line that passes through the opening intersection in a plan view and is further away from the tube axis than a parallel line that is parallel to the tube axis is 1 in effective length. The directional coupler according to claim 1, wherein the directional coupler is set to / 2.
9. A microwave heating device comprising the directional coupler according to claim 1.

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