JP3512668B2 - Electromagnetic field coupling structure and electric circuit device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for electrical connection between layers in a multilayer electric circuit board, and particularly to a microwave band.
The present invention relates to an electromagnetic field coupling structure called slot coupling used in a high frequency band of the millimeter wave band. Further, the present invention relates to an electric circuit device using the same.

[0002]

2. Description of the Related Art As a method of electrically connecting layers of a multilayer electric circuit board, a VIA hole is usually used in a low frequency band. On the other hand, in the high frequency band from the microwave band to the millimeter wave band, a method using electromagnetic field coupling has been proposed as a new interlayer connection method. There are various possibilities as a concrete structure using electromagnetic field coupling, and among them, the so-called “slot coupling” is known to have high practicality. For general slot coupling, see, for example, the document IEEE1993.
International Microwave
Symposium, pp. 1321-1324, "S
lot-Coupled Double-Sided
Microstrip Interconnects
AndCouplers "and the like.

FIG. 6 shows a slot coupling according to the prior art.
It is a schematic diagram of a typical structure. FIG. 6A is a cross-sectional view of the multilayer substrate viewed from the side, and FIG. 6B is a plan view in which the metal patterns on each layer of the multilayer substrate are separately taken out and arranged. In the figure, 1a and 1b are substrates made of an insulating material such as ceramics. A total of two layers 1a and 1b are laminated to form a multilayer substrate. 2a and 2b are high-frequency transmission lines to be electrically connected. Reference numeral 3a is a solid pattern inside the multilayer substrate, which functions as a ground layer. Reference numeral 4 denotes a slot-shaped opening formed in the ground layer 3a, through which the high-frequency transmission lines 2a and 2b are electromagnetically coupled. 5a and 5b are open ends of the tips of the high-frequency transmission lines 2a and 2b. Slot 4
To the open ends 5a and 5b is approximately λ / 4.

In this specification, the millimeter wave band (6
Several graphs of measurement results of slot coupling prototyped in the 0 GHz band) are shown. At that time, as a measuring method, reference IE
EE1998 International Micro
owave Symposium, pp. 1087-1
090, "Development Of A Pac
Kage Utilizing An Electro
magneticCoupling Structur
The method shown in e ”was used. That is, since the slot coupling has separate wiring on both the front and back sides of the substrate, it is difficult to perform high-frequency measurement using a wafer prober or the like as it is. Therefore, by connecting two slot couplings in series, as shown in the schematic diagram of FIG.
Allowed measurement by probing. Therefore, it should be noted that all the characteristics shown in the graphs below are characteristics of two slot combinations. The original insertion loss for one slot coupling is about half of the insertion loss in the graph described later.

[0005]

However, in the conventional slot-coupling structure, further improvement in insertion loss has been desired.

Particularly, when the slot coupling is designed on a multi-layer substrate having a large number of layers, the insertion loss is significantly deteriorated in the conventional slot coupling. Particularly in the case of a high frequency band such as a millimeter wave band, it is not uncommon to use a multilayer substrate having a large number of layers for the following reasons. That is, the thickness of each layer of the substrate needs to be sufficiently small with respect to the wavelength λ in order to avoid undesired phenomena such as higher-order modes and radiation. Therefore, it is as thin as about 0.1 mm in the millimeter wave band. It is not uncommon to become On the other hand, if the thickness of the entire multilayer substrate is thin, even if it is thin, about 0.3 mm, the mechanical strength is weak and the multilayer substrate is easily damaged.
Therefore, for example, a method is adopted in which three substrates having a thickness of 0.1 mm are laminated to make the total thickness 0.3 mm. As a result, slot coupling is also required to be able to sufficiently reduce the insertion loss even in a laminated substrate having three or more layers.

FIG. 7 shows a slot coupling according to the prior art.
As described above, it is a schematic diagram of a typical structure when applied to a multilayer substrate having a three-layer laminated structure. FIG. 7A shows
FIG. 7B is a cross-sectional view of the multilayer substrate viewed from the side, and FIG. 7B is a plan view in which the metal patterns on each layer of the multilayer substrate are separately taken out and arranged. In the figure, 3a and 3b are ground layers hidden inside the multilayer substrate, and 4a and 4b are slot-like openings provided on the ground layers. Figure 8
Is the result of actual trial manufacture of the structure of FIG. 7 (S21
Parameter) graph. In the measurement, as described above, the experimental method shown in the above literature was used. That is, the characteristic shown in the graph of FIG. 7 is the characteristic of two slot couplings. Although the slot coupling is designed around the 60 GHz band, it can be seen from FIG. 8 that the insertion loss is 5 to 6 dB.

Design values of the structure of FIG. 7 in the experiment of FIG. 8 will be described. The substrate material was an alumina ceramic material having a relative dielectric constant of about 9, and three layers each having a thickness of 0.15 mm were laminated. Transmission lines 2a and 2b are 50Ω
It is a microstrip line designed for. Slot 4
The dimensions of a and 4b are about 0.8 mm × 0.1 mm.

As described above, in the conventional slot coupling,
In particular, there are two major causes for the deterioration of the insertion loss in a multi-layer substrate having three or more layers. The first reason is that loss due to the resistance component of the metal films of the ground layers 3a and 3b occurs due to the current concentration in the end portions 6a and 6b of the slot coupling in FIG. When there are two ground layers as in the structure of FIG. 7, a loss occurs in each layer, so that the loss of the resistance component due to the current concentration is doubled. The second reason is that in the structure of FIG. 7, the electromagnetic field coupling between the transmission lines 2a and 2b is weakened. There are two additional reasons for weakening electromagnetic coupling. First
This is because the distance between the transmission lines 2a and 2b is increased by the thickness of the multilayer substrate. Secondly, in the structure of FIG. 7, a design method for strengthening electromagnetic field coupling by utilizing the “mirror image” relationship cannot be taken. That is, in the normal slot coupling as shown in FIG. 6, the electromagnetic field modes on the transmission lines 2a and 2b are in a mirror image relationship with the ground layer 3 interposed therebetween, and are stable, and strong mode coupling is obtained. On the other hand, in the structure of FIG. 7, since there is no ground layer at the central position of the mirror image relationship between the transmission lines 2a and 2b (the center in the thickness direction of the multilayer substrate), mode coupling cannot be strengthened by the mirror image principle. is there.

An object of the present invention is to reduce the insertion loss in the slot coupling structure as described above, and particularly to 3
It is to obtain a good electromagnetic field coupling even in a multi-layer substrate having more layers.

[0011]

The electromagnetic field coupling structure of the present invention uses a slot coupling type electromagnetic field coupling method as means for electrically connecting the layers of a multi-layer substrate forming a high frequency electric circuit, and the shape of the slot. As a ring-shaped slot, a plurality of ring-shaped slots are used in the ring-shaped slot.
-Shaped slots, inside one ring and another
It is characterized in that they are arranged in a nested manner .

The ring shape referred to here is characterized by closing a slot, which is usually in the form of a band, by connecting the ends of both ends and closing all the slots. Including shape. For example, a ring shape close to an ellipse and a ring shape close to a rectangle are all included.

[0013]

[0014]

The term " nested" means that it has a similar shape inside. When the shape is circular, not only concentric circles but also the inner circle may be deviated as long as it does not protrude from the outer circle. Further, each shape is not limited to a circle, and may be an ellipse or various deformed shapes.

By arranging a plurality of ring-shaped slots having different circumferential lengths in a nested manner, resonance can be caused at different wavelengths λ, thereby improving the insertion loss in a plurality of different frequency bands.

Further, the electric circuit device of the present invention is characterized in that the above-mentioned slot-coupling type electromagnetic field coupling structure is used as an electrical connecting means between layers of a multilayer electric circuit board.

Particularly, in an electric circuit device such as a radio communication circuit or a radar used in a high frequency band from a microwave band to a millimeter wave band, it is effective to use it for electrical connection between layers of a multi-layer substrate.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 shows an embodiment of the present invention.
FIG. 1A is a cross-sectional view of the multilayer substrate viewed from the side, FIG.
(B) is a plan view in which the metal patterns on each layer of the multilayer substrate are separately taken out and arranged. In the figure, 1a and 1
b is a substrate made of an insulating material such as ceramic.
A total of two layers 1a and 1b are laminated to form a multilayer substrate. 2a and 2b are high-frequency transmission lines to be electrically connected. Reference numeral 3 is a solid pattern inside the multilayer substrate, which functions as a ground layer. Reference numeral 4 denotes a slot-shaped opening formed in the ground layer 3, and the high frequency transmission lines 2a and 2b are electromagnetically coupled to each other through the opening.
5a and 5b are open ends of the tips of the high-frequency transmission lines 2a and 2b. The distance L from the slot 4 to the open ends 5a and 5b is approximately λ / 4, but the method of designing this distance may be the same as the prior art described in the literature and the like.

The ring-shaped slot of FIG. 1 is more than the rectangular-shaped slot used in the prior art structure of FIG.
Generally, the Q value is high. The main reason for this is that the ring-shaped inner conductor and outer conductor are not electrically short-circuited.
There is no end where current concentration occurs like 6a and 6b in FIG. Therefore, the loss due to the resistance component is small, and the insertion loss can be reduced. (Embodiment 2) FIG. 2 shows an embodiment of a multi-layer substrate having three or more layers. FIG. 2A is a cross-sectional view of the multilayer substrate viewed from the side, and FIG. 2B is a plan view in which the metal patterns on each layer of the multilayer substrate are separately taken out and arranged. In FIG. 2, reference numerals 1a, 1b, and 1c are three-layer substrates constituting a multilayer substrate. 3a and 3b are ground layers inside the multilayer substrate. Ring-shaped slots 4a and 4b are opened in the ground layers 3a and 3b, respectively. The electric signals on the high frequency transmission lines 2a and 2b are coupled in the thickness direction of the multilayer substrate through the two slots 4a and 4b.

Design values of the structure of FIG. 2 will be described. The substrate material is an alumina ceramic material having the same relative dielectric constant of about 9 as in the structure of FIG. 7, and three layers each having a thickness of 0.15 mm are laminated. The transmission lines 2a and 2b are microstrip lines designed to have 50Ω. The dimensions of the ring-shaped slots 4a and 4b are 0.1 mm in width and 0.27 mm in inner diameter.

FIG. 3 shows the result of experimental confirmation of the effect of the slot structure of FIG. The horizontal axis represents frequency and the vertical axis represents S21 (transmission) parameter. In the measurement,
As already mentioned, the experimental method given in said document was used. That is, the characteristic shown in the graph of FIG.
It is the characteristic of each piece. This slot structure is a slot coupling designed mainly in the 60 GHz band.
The insertion loss in the 0 GHz band is about 3 to 4 dB. It can be seen that the insertion loss is improved as compared with FIG. 8 using the conventional slot.

By positively utilizing the resonance of the slot itself as in this embodiment, as shown in FIG.
Strong electromagnetic field coupling can be obtained even when the number of stacked multilayer substrates is large. The slot coupling according to the conventional technique utilizes the electromagnetic field coupling based on the mirror image principle through the slot as described above, and does not necessarily utilize the resonance phenomenon of the slot itself. However, in the structure of the present invention shown in FIG. 1, since the resonance phenomenon of the ring-shaped slot itself having a high Q value as described above can be effectively utilized, the mode coupling due to the mirror image relationship does not occur.
Even in such a multi-layer substrate structure, since the electromagnetic field energy is strongly coupled between layers due to the resonance phenomenon of the slot itself, the insertion loss can be improved as compared with the prior art. (Embodiment 3) FIG. 4 shows another embodiment of the present invention, which is an example of a ring-shaped slot in accordance with the gist of the present invention. FIG. 4A is a cross-sectional view of the multilayer substrate viewed from the side, and FIG. 4B is a plan view in which the metal patterns on each layer of the multilayer substrate are separately taken out and arranged.

As described above, the present invention includes not only a perfect circular ring shape, but also a shape obtained by deforming the ring shape. (Embodiment 4) FIG. 5 shows another embodiment of the present invention in which a plurality of ring-shaped slots are provided. By changing the perimeter of each ring, the ring-shaped slot is made to resonate in a plurality of different frequency bands, and as a result, the insertion loss of slot coupling can be improved in a plurality of different frequency bands.

[0025]

By using the ring-shaped slot of the present invention, the insertion loss of slot coupling can be reduced.

Also, according to the present invention, by providing a plurality of ring-shaped slots, it is possible to improve the insertion loss of slot coupling in a plurality of different frequency bands.

By using the slot of the present invention in an electric circuit device, signals can be efficiently transmitted.

[Brief description of drawings]

FIG. 1 is a first embodiment of slot coupling according to the present invention.

FIG. 2 is a second embodiment of slot coupling according to the present invention.

FIG. 3 is an experimental result showing the characteristics of the embodiment of FIG.

FIG. 4 is a third example of slot coupling according to the present invention.

FIG. 5 is a fourth example of slot coupling according to the present invention.

FIG. 6 is a first example of slot coupling according to the prior art.

FIG. 7 is a second example of slot coupling according to the prior art.

FIG. 8 is an experimental result showing the characteristics of the example of FIG.

FIG. 9 is a schematic diagram showing the conditions of the experiment of FIGS. 3 and 8.

[Explanation of symbols]

1a, 1b, 1c Substrates 2a, 2b made of an insulating material such as ceramics High-frequency transmission lines 3, 3a, 3b Ground layer 4 inside a multilayer substrate Slot-shaped (rectangular) openings 4a, 4b Slot-shaped (ring-shaped) openings Parts 5a, 5b Open ends 6a, 6b of high-frequency transmission line Slot-shaped (rectangular) ends

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-4-233802 (JP, A) JP-A-9-293826 (JP, A) JP-A-11-261308 (JP, A) JP-A-52-1 144946 (JP, A) US Patent 3974462 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01P 5/02 603 JISST file (JOIS)

Claims (2)

(57) [Claims] 1. A slot-coupling type electromagnetic field coupling system is used as a means for electrically connecting layers of a multi-layer substrate constituting a high-frequency electric circuit, and a ring-shaped slot is used as the shape of the slot. At
Multiple ring-shaped slots separate inside one ring
The electromagnetic field coupling structure is characterized in that the rings are arranged, and the whole is arranged in a nested manner . 2. An electric circuit device using the slot coupling type electromagnetic field coupling structure according to claim 1 as means for electrically connecting layers of a multilayer electrical circuit board.