JP2002076724A - Waveguide-flat cable converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waveguide-flat cable converter that is low in loss, has a simple structure and can reduce the number of parts, the number of assembling steps and costs. SOLUTION: An upper end of a rectangular waveguide 11 is covered with a substrate 12 of a trip-plate structure. Top and bottom surfaces of the substrate are ground layers 13, 14, and a transmission cable 17 is arranged on an intermediate layer 16. The transmission line 17 faces a rectangular opening of the waveguide 11 and extends to a central position of the opening in the direction of the shorter side. A slot 18 is arranged on a central part of the ground layer 14 of the bottom surface, and makes a slot exciter. In a trip-plate feed slot antenna, a radio wave is radiated in the direction of the slot. The edge of the transmission cable is opened and excited to the slot by electromagnetic coupling. Then, a current becomes almost zero at the edge. The maximum value of the current flows at a position apart λ/4 of electric length from the edge by a standing wave. When the slot is excited at this position, the radio wave can be easily radiated. A termination block of the waveguide is not required in this converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide-to-plane line converter, for example, a waveguide-to-plane line converter used in a waveguide-fed flat antenna such as a BS antenna or an antenna for a millimeter-wave radar. .

[0002]

2. Description of the Related Art Microwaves and millimeter waves transmitted through a waveguide are amplified and frequency-converted in a planar line circuit.
Conventionally, a waveguide-
A plane line converter is provided. As this waveguide-plane line converter, one described in JP-A-10-126114 has been known. That is, as schematically shown in FIG. 11, this is a waveguide-to-plane line converter used in a waveguide-fed planar antenna,
The dielectric film 2 on which the planar line 1 is formed is replaced with a rectangular waveguide 3
And the end block 4. At this time, the dielectric film 2 is sandwiched and positioned between the concave portion 5 formed at the opening end of the rectangular waveguide 3 and the corresponding convex portion 6 formed on the end block 4. Reference numeral 7 denotes a probe at the tip of the flat line 1. 8 is a dielectric film 2
The end face of the waveguide 3 is electrically connected to that of the end block 4 by the notch 8.

[0003]

However, in the conventional waveguide-to-plane line converter, it is necessary to provide a terminal block for closing the opening of the waveguide. In addition, concave portions, convex portions, and the like have to be formed in both the waveguide and the terminal block. Therefore, there is a problem that the structure becomes complicated, the number of parts and the number of assembling steps increase, and the manufacturing cost increases.

[0004]

Accordingly, an object of the present invention is to provide a low-loss,
An object of the present invention is to provide a waveguide-to-plane line converter that has a simple structure, can reduce the number of parts and the number of assembling steps, and is low in cost. Another object of the present invention is to provide a waveguide-to-plane line converter in which a planar antenna and its transmitting / receiving circuit section are compactly mounted with a metal plate interposed therebetween.

[0005]

According to a first aspect of the present invention, there is provided a waveguide-to-plane line converter comprising a waveguide and a substrate covering an opening of the waveguide. A transmission line extending layer disposed in a predetermined direction, and a ground layer disposed on both sides of the transmission line arrangement layer so as to sandwich the transmission line arrangement layer. This is a waveguide-plane line converter in which a slot exciter is formed by providing a slot extending in a direction substantially perpendicular to the line and facing the opening of the waveguide.

According to a second aspect of the present invention, there is provided a waveguide-to-plane line converter comprising a waveguide and two substrates respectively covering openings at both ends of the waveguide. Each of the substrates has a transmission line arrangement layer in which transmission lines extending in a predetermined direction are arranged, and ground layers are arranged on both sides of the transmission line arrangement layer so as to sandwich the transmission line arrangement layer. A waveguide-to-plane line converter comprising a slot exciter formed by providing a slot extending in a direction substantially orthogonal to the transmission line and facing the opening of the waveguide.

As the substrate, for example, a three-layer printed circuit board can be used. In this case, it is also possible to form a triplate structure by forming two layers on the front and back sides of a three-layer printed circuit board as ground planes and forming transmission lines in an intermediate layer. Also,
A printed circuit board having four or more layers can be used. Also,
The length of the slot (notch) can be shorter than the long side of the opening of the rectangular waveguide. Further, this slot is provided on the ground surface of the printed circuit board facing the opening of the waveguide. The long axis direction of the slot in this slot exciter is arranged parallel to the long side direction of the rectangular waveguide.

Further, the waveguide may be formed by forming a rectangular through hole in a metal plate having a predetermined thickness. This makes it easy to dispose the printed circuit boards on both the front and back surfaces of the metal plate. As mentioned above, these printed circuit boards have the front and back surfaces as ground surfaces,
A triplate line structure in which strip lines are formed in the dielectric layer between them can be provided. One of the printed circuit boards may be provided with a planar antenna such as a patch antenna, and the other may be provided with a transmitting and receiving circuit.

According to the first aspect of the present invention, in the waveguide-to-plane line converter, a microwave or millimeter output from inside the waveguide is formed by forming a slot exciter on the substrate on which the plane line is provided. The wave is converted into an electric signal on a transmission line serving as a signal conductor through the slot. Then, the converted signal is processed by, for example, a signal processing unit. Or, conversely, millimeter waves can be output from the transmission line to the waveguide. In addition, since both the front and back surfaces of this substrate are ground layers, radiation loss during power supply can be reduced.

According to the second aspect of the present invention, since the slot exciters are respectively formed on the two planar line substrates covering the openings at both ends of the waveguide, power can be supplied from the planar line of one substrate to the other. it can. For example, a configuration in which a planar antenna is provided on one substrate and a transmission / reception circuit therefor is provided on the other substrate.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a waveguide-to-plane line converter according to the present invention will be described below with reference to FIGS. This embodiment shows a case where the waveguide-to-plane line converter according to the present invention is applied to an electromagnetic coupling type slot antenna. 1 to 3, reference numeral 11 denotes a rectangular waveguide, and the rectangular waveguide 11 has a waveguide having a rectangular cross section. The upper end opening of the rectangular waveguide 11 is covered with a three-layer printed circuit board 12. That is, the three-layer printed circuit board 12 is placed at the opening edge of the rectangular waveguide 11.
Are fixed with an adhesive or the like. This printed circuit board 1
Reference numeral 2 denotes a three-layer triplate line structure. That is, the upper and lower front and back layers 13 and 14 are used as ground layers, and transmission lines 17 are provided in intermediate layers (dielectric layers) 15 and 16 sandwiched between them. The transmission line 17 is provided by printing or the like on the upper surface of the intermediate layer 16 made of a dielectric film or the like. In addition, the transmission line 17 is formed at a center position with respect to the long side direction of the opening and extends in the short side direction by a predetermined length so as to face the rectangular opening of the waveguide 11. . This transmission line 17 functions as a power supply unit. A predetermined length SL and a predetermined width SW are provided at the center of the back layer 14.
Slot 18 is formed. The slot 18 is provided at the center of the opening and extends in the long side direction. Therefore, the slot 18 has a twisted positional relationship so as to be orthogonal to the transmission line 17. Therefore, a slot exciter is configured to include the slot 18. It is preferable that the distance between the slot 18 and the end of the transmission line 17 be an electrical length λ / 4. In addition, such a triplate structure,
Lower radiation loss compared to microstrip lines. This is because the ground layer 1 is on both sides of the printed circuit board 12.
This is because it is covered with 3,14. In order to make the upper and lower ground layers 13 and 14 have the same potential, a plurality of vias (via hos) are formed in the dielectric substrates 15 and 16 serving as the intermediate layers.
le) 19 is formed to penetrate at a predetermined position. The inner surfaces of these vias 19 are, for example, plated with metal. Further, the ground layers 13 and 14 and the dielectric layers 15 and 16 are connected by a pair of screws. The printed circuit board 12 has two holes for screwing. Further, a female screw is cut at the opening edge of the waveguide 11 and the female screw is fixed together, so that the printed circuit board 12 and the metal waveguide 11 can be fixed.

Next, details of the electromagnetically coupled slot antenna according to this embodiment will be described. In this embodiment, a design example in the case of targeting a microwave having a frequency around 26 GHz will be described. In this frequency band, the interval between the upper and lower ground layer substrates 13 and 14 must be about 0.6 mm at the maximum. This is based on the result of the simulation. Therefore, the thickness of the dielectric substrates 15 and 16 is set to 0.1.
4 mm (layer spacing 0.2 mm). In addition, Teflon (registered trademark) is used as a substrate material (material of the dielectric layers 15 and 16). The relative dielectric constant (ε _γ ) of this Teflon is
2.15. Here, the line width W of the transmission line 17
Is given by the following equation. W = b ^{_{[{30π / (ε γ) 1/2}} · Z 0} -0.441 ] [mm] where, W is a line width [mm], b is the substrate thickness [m
m] and Z ₀ indicate characteristic impedance [Ω].
This equation is applicable when ^{_{(ε γ) 1/2 · Z 0}} <120. That is, when Z ₀ = 50 [Ω], ε _γ <5.
76 is the upper limit of application. Here, ε _γ = 2.15, b =
By substituting 0.4 and Z ₀ = 50, W = 0.34 [m
m].

The end of the transmission line 17 designed as described above is opened to excite the slot 18 by electromagnetic coupling.
Since the tip is open, the impedance becomes high at this tip. That is, the current becomes almost zero. Due to the standing wave, the position shifted from the tip by the electrical length λ / 4 takes the maximum value of the current. Therefore, when the slot 18 is excited at this portion, the radio waves are most easily emitted. 26GH
In z, λ / 4 ≒ 2.9 [mm], but SO = 2.5 [mm] in consideration of the shortening rate due to the dielectric. It is known that the largest high-frequency current is induced when the slot length SL to be coupled is λ / 2 (relative type of λ / 2 long dipole antenna). Here, SL = 3.8 [mm] in consideration of the shortening rate.
Also, the slot width SW is selected to be a value sufficiently smaller than its length. Here, it is assumed that SW = 0.2 [mm]. FIG. 4 shows a simulation result with the above parameters as “slot ant alone”. Looking at this return loss curve, it can be seen that the frequency is slightly deviated from 26 GHz as compared with “slot + waveguide”, but the curve is well matched. Here, the frequency can be freely adjusted by changing the slot length SL and the slot position SO.

The triplate-fed slot antenna having such a configuration emits radio waves only in the slot direction. Therefore, the waveguide 11 is connected in this direction, and the printed circuit board 12 and the waveguide 11 are connected by this. The inner diameter of the opening of the waveguide 11 is a × b = 11.8.
× 5.9. The return loss characteristic in this case is shown as "slot + waveguide" in FIG. It can be seen that the tuning frequency is slightly deviated from the case of the above “slot ant alone”. The frequency adjustment in this case is affected not only by the slot length SL and the slot position SO, but also by the inner dimensions a × b of the waveguide 11. In this example,
Instead of simply connecting the slot antenna 12 and the waveguide 11, the inside dimensions of the waveguide 11 are also optimized and tuned to a desired frequency. Here, WRI-
At 220 (inner dimension: a × b = 10.668 × 4.318), the tuning frequency becomes about 27.7 GHz. WRI-18
At 0 (a × b = 12.954 × 6.477), the tuning frequency becomes about 24.7 GHz. That is, the frequency can be adjusted to a desired frequency by tuning the approximate frequency of the slot antenna alone and optimizing the inner dimensions of the waveguide. In order to connect this waveguide to a standard-sized waveguide, it is preferable to use a tapered tube or the like.

The printed circuit board may have a multilayer structure of four or more layers. In this case, three layers on the waveguide side of the printed circuit board are used as slot exciters. Further, the transmission line (triplate line) can be led out to a layer on the side opposite to the waveguide by a via or the like. This way,
The waveguide can be connected to an electronic circuit component mounted on the extracted layer or an electromagnetic coupling type (inner layer feeding type) planar antenna.

Next, another embodiment of the present invention will be described with reference to FIGS. In this embodiment, a rectangular through hole 22 having a size of a × b is formed in a rectangular metal plate 21 having a thickness t. The through hole 22 functions as a waveguide. The three-layer printed circuit board 2 having the same configuration as that of the above embodiment is provided on both the front and back surfaces of the metal plate 21.
3 and 24 are configured to be bonded by screwing. Other bonding methods include thermocompression bonding, soldering, and a conductive adhesive. In each of the printed circuit boards 23 and 24, a slot 2 is provided in the ground layer of the substrate on the metal plate 21 side.
5, 26, and transmission lines 27, 28 are formed in the dielectric layer, respectively. Reference numerals 29 and 30 denote respective vias, and reference numeral 31 denotes a screw insertion hole penetrating vertically. Note that screw insertion holes are also formed at corresponding positions of the metal plate 21. This embodiment is an effective method for connecting a high-frequency circuit formed by a printed circuit board and a planar antenna formed by a printed circuit board or the like with the metal plate 21 interposed therebetween. in this case,
Since the aperture size of the rectangular waveguide can be changed arbitrarily, there is no need to interface with a standard waveguide. Therefore, it is not necessary to attach a conversion part such as a tapered tube part to the converter. Here, each parameter (a, b, SL, SW, SO, printed circuit board constant, etc.)
FIG. 7 and FIG. 8 show the return loss and the insertion loss when the thickness t of the metal plate is changed, respectively. Metal plate thickness t from 1 mm to 10
mm, the characteristics are not significantly changed in any case, and it can be seen that any thickness can be used sufficiently. However, the tuning frequency is slightly deviated from 26 GHz, but this is the same as in the above-described embodiment.
By optimizing × b or the like, it is possible to adapt to a desired frequency. Further, as the thickness t of the metal plate becomes thinner, the screw holes cannot be shared by the upper and lower printed circuit boards. In this case, the screw holes dedicated to each printed circuit board need only be shifted to the metal plate. . The other configuration, operation and effect are the same as those in the above embodiment.

The two printed circuit boards 23, 24
One or both of them may have a multilayer structure of four or more layers, and the three layers on the waveguide side may be slot exciters. And
The transmission line (triplate line) can be drawn out to the layer on the opposite side of the waveguide by a via or the like, and can be connected to circuit components mounted on this layer or an electromagnetic coupling type (inner layer feeding type) planar antenna.

9 and 10 show another embodiment of the waveguide-to-plane line converter according to the present invention. In this embodiment, the layout is the same as the embodiment shown in FIG. 8 except that the upper and lower printed boards 32 and 33 sandwiching the metal plate 31 face in opposite directions. That is, the transmission line 34 formed on the upper printed circuit board 32 is
6 extends from one end in the direction orthogonal to 6 and is open at the other end. On the other hand, the transmission line 37 provided on the lower printed circuit board 33 extends from the other end. One end is an open end. Thereby, the degree of freedom of the circuit layout can be increased. The metal plate (for example, aluminum plate) 31 has rectangular holes 38 corresponding to the slots 35 and 36.
Is formed, and this rectangular hole 38 functions as a waveguide.
Other configurations are the same as those in the above embodiment. Further, the point that one or both of the two printed boards can have a multilayer structure of four or more layers is also the same as that of the above embodiment.

[0019]

According to the waveguide-to-plane line converter of the present invention, the end block (cover) of the waveguide is not required. Therefore, the number of parts can be significantly reduced. In addition, the number of assembling steps in manufacturing the converter can be reduced. Therefore, the cost can be significantly reduced as compared with the related art. Also, a low-loss converter can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a waveguide-to-plane line converter according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a printed circuit board portion of the waveguide-plane line converter according to one embodiment of the present invention.

FIG. 3 is a bottom view showing a printed circuit board portion of the waveguide-plane line converter according to one embodiment of the present invention.

FIG. 4 is a graph showing return loss in a design example of the waveguide-plane line converter according to one embodiment of the present invention.

FIG. 5 is a perspective view showing a waveguide-to-plane line converter according to another embodiment of the present invention.

FIG. 6 is a plan view showing a printed circuit board portion of a waveguide-to-plane line converter according to another embodiment of the present invention.

FIG. 7 is a graph showing a return loss in a design example of a waveguide-to-plane line converter according to another embodiment of the present invention.

FIG. 8 is a graph showing an insertion loss in a design example of a waveguide-plane line converter according to another embodiment of the present invention.

FIG. 9 is a perspective view showing a waveguide-to-plane line converter according to another embodiment of the present invention.

FIG. 10 is a plan view showing a waveguide-to-plane line converter according to another embodiment of the present invention.

FIG. 11 is an exploded view showing a conventional waveguide-to-plane line converter.

[Explanation of symbols]

 11: Waveguide, 12: Substrate, 13, 14: Ground layer, 16: Dielectric layer (transmission line arrangement layer), 17: Transmission line, 18: Slot.

Claims (2)

[Claims] 1. A waveguide-to-plane line converter comprising a waveguide and a substrate covering an opening of the waveguide, wherein the substrate has a transmission line provided with a transmission line extending in a predetermined direction. A line layer is provided, and ground layers are respectively disposed on both sides of the transmission line layer so as to sandwich the transmission line layer. The waveguide extends on one side of the ground layer in a direction substantially orthogonal to the transmission line. 3. A waveguide-to-plane line converter, wherein a slot exciter is formed by providing a slot facing an opening of the waveguide. 2. A waveguide-to-plane line converter comprising a waveguide and two substrates respectively covering openings at both ends of the waveguide, wherein each of these substrates has a predetermined direction. A transmission line extending on the transmission line, and ground layers on both sides of the transmission line arrangement layer. A waveguide-to-plane line converter, wherein a slot exciter is formed by providing a slot extending in a direction orthogonal to the opening of the waveguide.