JP2015133580A - plane transmission line waveguide converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plane transmission line waveguide converter capable of outputting a signal propagating in a plane line to a waveguide with low loss without being affected by an electromagnetic wave leaking outside the waveguide.SOLUTION: A plane transmission line waveguide converter comprises: a multilayer substrate 2 on which a plane transmission line 21 for propagating a high frequency signal is created; and a waveguide 3 created by processing a metal frame 10. A probe 22 projecting inside the waveguide 3 to couple with an electromagnetic field inside the waveguide 3 is formed on the plane transmission line 21. A metal thin film 24 is formed on a side face along the probe 22 of the multilayer substrate 2. The probe 22 is inserted in parallel with a waveguide 3's E plane 3E perpendicular to its H plane 3H. When the multilayer substrate 2 is fitted to the waveguide 3, an electromagnetic wave leaking from a gap 14 formed between the metal frame 10 and a side face 23 along the probe 22 is reflected or intercepted by the metal thin film 24 to be prohibited from leaking in a dielectric layer 2a. Thereby, a signal propagating in the plane transmission line 21 is output to the waveguide with low loss.

Description

  The present invention relates to a planar transmission line waveguide converter that mutually converts a propagation mode of an electromagnetic wave propagating through a planar transmission line and a propagation mode of an electromagnetic wave propagating inside the waveguide.

  Conventionally, in order to realize a waveguide-fed planar antenna such as a millimeter wave radar antenna, the propagation mode of the electromagnetic wave propagating through the planar transmission line is converted to the propagation mode of the electromagnetic wave propagating inside the waveguide. Planar transmission line waveguide converters are used. As a specific example of a planar transmission line waveguide converter, Patent Document 1 discloses a waveguide probe pattern provided on the surface of a multilayer substrate and a through formed at a sufficiently narrow interval around the waveguide cavity. A microstrip line-waveguide converter having a hole is described.

  In the microstrip line-waveguide converter described in Patent Document 1, many through-through holes are formed at positions corresponding to the tube wall of the waveguide around the waveguide probe pattern. Specifically, the through holes are formed at sufficiently narrow intervals with respect to the wavelength of the high-frequency signal, and suppress leakage of electromagnetic waves from the inside of the waveguide to the multilayer substrate other than the high-frequency substrate.

  Further, in the microstrip line-waveguide converter described in Patent Document 1, many similar through holes are formed around the microstrip line. As a result, the microstrip line is protected and shielded together with the shield groove of the upper housing, and unnecessary radiation from the microstrip line to the outside and unnecessary resonance are suppressed (see paragraph 0004 of Patent Document 2). ).

  In Patent Document 3, the first and second waveguide main bodies divided into two by a plane perpendicular to the H plane at the center position of the H plane of the waveguide hold the printed circuit board. A bonded waveguide microstrip transducer is described.

JP 2004-320460 A JP 2011-120155 A JP 2003-318613 A

  In the microstrip line-waveguide converter described in Patent Document 1, even if through holes are installed at a sufficiently narrow interval with respect to the wavelength, there is a limit to reducing the interval due to processing restrictions. . For this reason, in the case of a high-frequency signal having a short wavelength such as a millimeter wave band, there is a problem that the radio wave passes through the through holes and leaks into the multilayer substrate. In addition, in the waveguide microstrip converter described in Patent Document 3, when a multilayer substrate is used as a printed circuit board, electromagnetic waves enter the multilayer substrate through a gap between the waveguide and the side surface of the substrate. There is. That is, in the conventional planar transmission line waveguide converter, there is a problem that unnecessary resonance and loss occur due to the influence of electromagnetic waves leaking into the multilayer substrate.

  The object of the present invention has been made in view of the above-described problems, and can output a signal propagating through a planar line to a waveguide with low loss without being affected by electromagnetic waves leaking into the multilayer substrate. An object is to provide a possible planar transmission line waveguide converter.

(First aspect)
The planar transmission line waveguide converter according to the first aspect of the present invention includes a multilayer substrate on which a planar transmission line for propagating a high-frequency signal is fabricated, the waveguide fabricated by processing a metal casing, The planar transmission line is formed with a probe that protrudes into the waveguide and couples with the electromagnetic field inside the waveguide, and the multilayer substrate has a metal thin film formed on a side surface along the probe. It is characterized by being.

  According to the first aspect, for example, when the multilayer substrate is assembled to the waveguide, the electromagnetic wave leaking from the gap formed between the metal housing and the multilayer substrate causes the side surface of the multilayer substrate along the probe. Since it is reflected or cut off by the metal thin film formed on the substrate and does not leak into the multilayer substrate, a signal propagating through the planar line with low loss can be output to the waveguide.

(Second aspect)
The planar transmission line waveguide converter according to the second aspect of the present invention is characterized in that the probe is inserted in parallel with an E plane perpendicular to the H plane of the waveguide.

  According to the second aspect, since the probe is inserted in parallel with the E surface, the waveguide can be formed in parallel with the substrate surface of the multilayer substrate. Therefore, according to the second aspect, the degree of freedom in circuit design to be mounted on the multilayer substrate can be increased as compared with the case where the waveguide is formed perpendicular to the substrate surface of the multilayer substrate. Thus, the converter can be simplified and downsized. Furthermore, since the waveguide is formed in parallel with the substrate surface of the multilayer substrate, the shape of the waveguide can be easily processed from the viewpoint of cutting out the metal casing.

(Third aspect)
In the planar transmission line waveguide converter according to the third aspect of the present invention, a ground layer is formed on the multilayer substrate, and the metal thin film is formed from the side surface of the multilayer substrate along the probe. And is integrally formed over the surface of the high-frequency substrate and is electrically connected to the ground layer through a through hole provided on the surface of the high-frequency substrate.

  According to the third aspect, the metal thin film formed from both sides of the multilayer substrate to the high frequency substrate is physically connected to the ground layer formed on the multilayer substrate through the through hole. The ground effect of the through hole can be further strengthened, and the blocking effect of the pseudo waveguide formed by the multilayer substrate, the through hole, and the ground layer can be further strengthened. Thereby, the electromagnetic wave leaking into the multilayer substrate can be more effectively suppressed, and a signal propagating through the planar line with low loss can be output to the waveguide.

  According to the present invention, a signal propagating through a planar line with low loss can be output to a waveguide.

It is a figure for demonstrating the planar transmission line waveguide converter to which this invention was applied. It is a figure for demonstrating the laminated structure of a multilayer substrate. It is a figure for demonstrating the multilayer substrate of the planar transmission line waveguide converter to which this invention was applied, and the multilayer substrate of the planar transmission line waveguide converter which concerns on a comparative example. It is a figure for demonstrating about sectional drawing of the planar transmission line waveguide converter to which this invention was applied. It is a figure which shows the electric field strength of the planar transmission line waveguide converter to which this invention was applied, and the electric field strength of the planar transmission line waveguide converter which concerns on a comparative example. It is a figure for demonstrating the frequency characteristic of the filter which concerns on this embodiment, and the filter which concerns on a comparative example.

  A mode for carrying out the present invention (hereinafter referred to as the present embodiment) will be described with a specific example. The present embodiment relates to a planar transmission line waveguide converter that mutually converts a propagation mode of electromagnetic waves propagating through a planar transmission line and a propagation mode of electromagnetic waves propagating inside the waveguide. As a specific example of such a planar transmission line waveguide converter, a configuration of a planar transmission line waveguide converter 1 as shown in FIG. 1 will be described.

(1) Overall Configuration FIG. 1A is a perspective view showing an outline of a planar transmission line waveguide converter 1. As shown in FIG. 1A, the planar transmission line waveguide converter 1 processes a high-frequency substrate 20 on which a planar transmission line 21 for propagating a high-frequency signal, a multilayer substrate 2, and a metal housing 10 are processed. And a waveguide 3 manufactured as described above.

  FIG. 1B and FIG. 1C are diagrams showing a cross-sectional shape that appears when the planar transmission line waveguide converter 1 is cut along the same plane as the multilayer substrate 2.

  As shown in FIG. 1B, the waveguide 3 is a cavity formed by cutting out the side surface 11 of the metal housing 10. Specifically, the waveguide 3 is a rectangular waveguide determined by an E plane 3E parallel to the electric field generated in the waveguide 3 and an H plane 3H perpendicular to the electric field. The waveguide 3 having such a shape functions as a waveguide from the opening 3 </ b> C to the transmitting antenna that converts the propagation mode of a high-frequency signal propagating through the planar transmission line 21 described later. Alternatively, the waveguide 3 functions as a waveguide from the receiving antenna that converts the propagation mode of the electromagnetic wave introduced from the opening 3 </ b> C and propagates to the planar transmission line 21.

  Further, for example, as shown in FIG. 1A, the metal housing 10 has a substrate installation surface 12 on which the multilayer substrate 2 is installed at a position parallel to the waveguide 3. Further, the metal housing 10 is formed with a hole 13 c that protrudes into the waveguide 3 in a part of the side surface 13 perpendicular to the substrate installation surface 12.

  The multilayer substrate 2 is a substrate installed on the substrate installation surface 12 as shown in FIG. The multilayer substrate 2 has a multilayer structure in which a dielectric layer 2a is sandwiched between ground layers 2b and 2c as shown in FIG. The multilayer substrate 2 includes, for example, a metal layer 201, a dielectric layer 202, a metal layer 203, a dielectric layer 204, a metal layer 205, a dielectric layer 206, and a metal layer 207 in this order, as shown in FIG. A structure in which each layer is stacked, or a structure in which each layer is stacked in the order of a metal layer 211, a dielectric layer 212, a metal layer 213, a dielectric layer 214, and a metal layer 215 as shown in FIG. .

  Further, the high frequency substrate 20 is arranged on the surface of the multilayer substrate 2 as shown in FIGS. 2A to 2C, and is a planar transmission made of a metal layer laminated on the surface 20a of the high frequency substrate 20. The track 21 is configured. Further, as shown in FIGS. 1B and 1C, the planar transmission line 21 is disposed at a position protruding into the waveguide 3 through a hole 13 </ b> C formed in the metal housing 10. A probe 22 is formed.

  The probe 22 is arranged at a position protruding into the waveguide 3 through such a hole 13c. With this arrangement, the probe 22 is inserted into the waveguide 3 so that the plane transmission line 21 is inserted in the direction perpendicular to the H plane and parallel to the E plane, and coupled to the electromagnetic field inside the waveguide 3. To do.

  In the planar transmission line waveguide converter 1 configured as described above, when the planar transmission line 21 is inserted into the waveguide 3 through the hole 13c, that is, the multilayer substrate 2 is assembled to the waveguide 3. 1C, a gap 14 is formed between the side surface 13c1 of the hole 13c and the side surface 23 of the multilayer board 2 along the probe 22, as shown in FIG. It becomes.

  In the planar transmission line waveguide converter 1 according to the present embodiment, in order to prevent the leaked electromagnetic waves from entering the multilayer substrate 2, as shown in FIG. A metal thin film 24 is formed on the side surface 23 along. Specifically, the metal thin film 24 is plated over the surface 20a of the high frequency substrate 20 from the side surface 23 perpendicular to the planar transmission line 21 so as to surround the probe 22 as shown in FIG. Thus, the thin film is integrally formed. Further, the metal thin film 24 is electrically connected to at least one of the ground layer 2b and the ground layer 2b of the multilayer substrate 2 shown in FIG. 2A through four through holes 25 provided in the high frequency substrate 20, for example. It is connected to the. In FIG. 3A, the metal thin film 24 is provided on both side surfaces of the multilayer substrate 2 and the high-frequency substrate 20, but the metal thin film 24 may be provided on at least the side surface 23 of the multilayer substrate 2. .

  By forming the metal thin film 24 on the side surface 23 along the probe 22 in this way, the side surface 13c1 of the metal housing 10 and the side surface 23 along the probe 22 when the multilayer substrate 2 is assembled to the waveguide 3 are formed. Electromagnetic waves leaking from the gaps 14 formed therebetween are reflected or blocked by the metal thin film 24. That is, by preventing the electromagnetic wave leaking from the gap 14 from leaking to the multilayer substrate 2, a signal propagating through the planar line with low loss can be output to the waveguide 3.

  Further, the metal thin film 24 formed from the side surface 23 of the multilayer substrate 2 to the surface 20a of the high frequency substrate 20 is physically applied to the ground layers 2b and 2c formed on the multilayer substrate 2 through the through holes 25. As a result, the ground effect of the through hole 25 is further strengthened, and the blocking effect of the pseudo waveguide formed by the multilayer substrate 2, the through hole 25, and the ground layers 2b and 2c is further strengthened. it can. For this reason, leakage of the electromagnetic wave to the multilayer substrate 2 can be effectively suppressed, and a signal propagating through the planar transmission line 21 with low loss can be output to the waveguide. As shown in FIG. 3A, it is desirable not to provide the metal thin film 24 in the portion 26 disposed in the waveguide 3 of the probe 22 from the viewpoint of not reducing the coupling efficiency.

(2) Evaluation of planar transmission line waveguide converter according to this embodiment As a comparison target for evaluating the transmission characteristics of the planar transmission line waveguide converter 1 according to this embodiment, a multilayer in which a metal thin film 24 is formed Instead of the substrate 2, a planar transmission line waveguide converter 40 including a multilayer substrate 4 in which a metal thin film is not formed on the side surface 41 as shown in FIG. 3B is used.

  First, the electric field strength distribution of the planar transmission line waveguide converter 1 of this embodiment and the planar transmission line waveguide converter 40 according to the comparative example when viewed from a cross-sectional view as shown in FIG. 4 is evaluated. FIG. 4 shows a cross-sectional view that appears when the multilayer substrate 2 is cut in a direction perpendicular to the electromagnetic wave traveling direction of the waveguide 3, and FIG. 5A shows the planar transmission line waveguide of this embodiment. The electric field strength distribution of the converter 1 is schematically shown, and FIG. 5B schematically shows the electric field strength distribution of the planar transmission line waveguide converter 40 according to the comparative example. Note that in FIGS. 5A and 5B, a portion where the electric field is strong is expressed by a high-density dot, and a portion where the electric field is weak is expressed by a low-density dot.

  As is clear from FIGS. 5A and 5B, in the planar transmission line waveguide converter 40 according to the comparative example, an electric field is generated inside the dielectric layer 2a as shown in FIG. 5B. While the presence, that is, electromagnetic waves are leaking, the planar transmission line waveguide converter 1 according to the present embodiment suppresses the leakage of electromagnetic waves into the dielectric layer 2a. As is apparent from the difference in electric field strength, the planar transmission line waveguide converter 1 according to the present embodiment has the side surface 13c1 of the metal housing 10 and the probe when the multilayer substrate 2 is assembled to the waveguide 3. Electromagnetic waves leaking from the gaps 14 formed between the side surfaces 23 along 22 are reflected or blocked by the metal thin film 24, so that they do not leak into the dielectric layer 2a.

  Next, the pass characteristics of the planar transmission line waveguide converter according to this embodiment and the planar transmission line waveguide converter according to the comparative example are evaluated with reference to FIG.

  FIG. 6A shows a simulation result in which the horizontal axis represents the signal transmission frequency and the vertical axis represents the pass gain between the planar transmission line 21 and the waveguide 3. FIG. 6B shows the actual measurement result in which the horizontal axis represents the signal transmission frequency and the vertical axis represents the pass gain between the planar transmission line 21 and the waveguide 3. Here, in FIG. 6 (A) and FIG. 6 (B), the frequency characteristics of the planar transmission line waveguide converter according to the present embodiment are shown by solid lines, and the planar transmission line waveguide converter according to the comparative example is shown. The frequency characteristic is indicated by a broken line.

  As is clear from FIGS. 6A and 6B, the planar transmission line waveguide converter according to this embodiment is a planar transmission line waveguide according to a comparative example over the entire frequency band. As a result, the pass gain is higher than that of the converter. As is apparent from the results of FIG. 5, when the multilayer substrate 2 is assembled to the waveguide 3 in the planar transmission line waveguide converter 1 of the present embodiment, this is shown in FIG. Since electromagnetic waves leaking to the dielectric layer 2a from the gap 14 formed between the side surface 13c1 and the side surface 23 are reflected or blocked by the metal thin film 24, the electromagnetic waves leaking to the dielectric layer 2a disappear, This is because the passage gain is increased accordingly.

(3) Effect As described above, the planar transmission line waveguide converter 1 according to the present embodiment is as shown in FIG. 1C described above when the multilayer substrate 2 is assembled to the waveguide 3. Electromagnetic waves leaking from the gap 14 formed between the side surface 13c1 and the side surface 23 may be reflected or blocked by the metal thin film 24 formed on the side surface 23 along the probe 22 and leak to the dielectric layer 2a. Therefore, a signal propagating through the planar transmission line 21 with low loss can be output to the waveguide 3.

  Preferably, in the planar transmission line waveguide converter 1 according to the present embodiment, since the probe 22 is inserted in parallel with the E surface 3E, the waveguide 3 is formed in parallel with the substrate surface of the multilayer substrate 2. can do. Therefore, the planar transmission line waveguide converter 1 increases the degree of freedom of circuit design mounted on the multilayer substrate 2 as compared with the case where the waveguide 3 is formed perpendicular to the substrate surface of the multilayer substrate 2. As a result, the converter can be simplified and downsized. Furthermore, since the waveguide 3 is formed in parallel with the substrate surface of the multilayer substrate 2, the shape of the waveguide 3 can be easily processed from the viewpoint of cutting out the metal housing 10.

  Preferably, a metal thin film 24 formed over the surface 20a of the high frequency substrate 20 so as to surround the probe 22 from both side surfaces 23 of the multilayer substrate 2 is formed on the multilayer substrate 2 through the through holes 25. Since the ground effect of the through-hole 25 is further strengthened, the pseudo-waveguide formed by the multilayer substrate 2, the through-hole 25, and the ground layers 2b and 2c is physically connected to the ground layers 2b and 2c. The blocking effect can be further strengthened. Thereby, leakage of the electromagnetic wave to the dielectric layer 2a can be effectively suppressed, and a signal propagating through the planar transmission line 21 with low loss can be output to the waveguide 3.

  In the planar transmission line waveguide converter 1 according to this embodiment, the passband is not limited to the frequency band as shown in FIG. 6, and the dimensions of each member may be adjusted according to the application example. .

DESCRIPTION OF SYMBOLS 1 Planar transmission line waveguide converter 2 Multilayer substrate 3 Waveguide 20 High frequency board 21 Planar transmission line 22 Probe 24 Metal thin film

Claims (3)

A multilayer substrate;
A high-frequency substrate on which the planar transmission line that is disposed on the multilayer substrate and propagates a high-frequency signal is manufactured;
A waveguide produced by processing a metal housing,
The planar transmission line is formed with a probe that protrudes into the waveguide and couples with an electromagnetic field inside the waveguide,
A planar transmission line waveguide converter, wherein the multilayer substrate has a metal thin film formed on a side surface along the probe.   2. The planar transmission line waveguide conversion according to claim 1, wherein the probe is inserted in a direction in which the planar transmission line is inserted into the waveguide perpendicular to the H plane and parallel to the E plane. vessel. A ground layer is formed on the multilayer substrate,
The metal thin film is integrally formed over the surface of the high-frequency substrate so as to surround the probe from a side surface along the probe of the multilayer substrate, and through a through hole provided on the surface of the high-frequency substrate. 3. The planar transmission line waveguide converter according to claim 1, wherein the planar transmission line waveguide converter is electrically connected to the ground layer.