JPH0225281B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] By coupling a pair of distributed coupling type strip conductors with a length equivalent to a quarter wavelength of the transmission frequency through a rectangular dielectric substrate, the degree of coupling can be improved. To provide a directional coupler with high efficiency and low cost.

[Industrial application field]

The present invention relates to improvements in distributed coupling type directional couplers using microstrip lines.

A directional coupler in the microwave or millimeter wave band, which has a desired combination of strip conductors with a length equivalent to a quarter wavelength of the transmission frequency, is significantly more efficient than a directional coupler made of a waveguide. It is widely used because it has the advantage of being small.

There are two types of directional couplers using microstrip lines: direct coupling type and distributed coupling type, but the former direct coupling type has the disadvantages of occupying a large area and having a small fractional bandwidth. , the latter distributed combination type, which eliminates these disadvantages, is being used more often.

Such a directional coupler is required to have a high degree of coupling and be low in cost.

[Prior art] Figure 4 shows one of the conventional distributed coupling type directional couplers.
FIG. 3 is a perspective view of an example.

Figure 4 shows an example of a distributed coupling type, which is a small, broadband directional coupler.It is an interdigitated type distributed coupler with a high coupling degree of approximately -3 dB. A lower conductor layer 6 is formed on the entire lower surface of the ceramic substrate 5.

On the top surface of the ceramic substrate 5, three strip conductors 7, 9, and 8, each having a length of approximately a quarter wavelength of the transmission frequency, are arranged in parallel in this order and very close to each other (for example, with a spacing of 1 to 2 μm). It is provided.

A first port 1 is connected to one terminal of the strip conductor 7, and a fourth terminal is connected to the terminal of the strip conductor 8 diagonally to the first port 1.
The port 4 is connected to the port 4.

Furthermore, a second port 2 parallel to the fourth port 4 is connected to a terminal of the strip conductor 9 provided between the strip conductors 7 and 8, which is opposite to the first port 1, and the strip conductor 9
A third port 3 which is parallel to the first port 1 and is connected to the other terminal of the port 4 is provided at the other end of the port 4 .

Such a circuit is formed by depositing a nichrome film on the entire surface of the ceramic substrate 5 and a gold film on top of it.
It was formed by photolithography.

Then, a bridge wire 10 such as a gold ribbon spanning the strip conductor 9 is wire-bonded at two locations, one near the first port 1 and the other near the fourth port 4, to connect the strip conductor 7 and the strip conductor. 8 is connected.

Since they are coupled as described above, for example, an input signal from the first port 1 is output from the second port 2 and the fourth port 4, and almost no signal is emitted from the third port 3. It has this direction. Note that when an input signal is input from the fourth port 4, the input signal is input from the first port 1 and the third port 3.
Of course, it will be output more.

[Problem that the invention seeks to solve]

However, in the conventional directional coupler described above, in order to increase the degree of coupling, it is necessary to use a ceramic substrate with a high dielectric constant and to provide strip conductors extremely close to each other.

For this purpose, an expensive ceramic substrate is used,
There is a problem in that the strip conductor is formed of a thin film with complicated processing steps, resulting in high cost.

[Means for solving problems]

In order to solve the above conventional problems, the present invention
As illustrated in FIG. 1, it is formed on the surface of a dielectric substrate 15, and has a first port 1 at one terminal and a third port 3 at the other terminal. The first one with a length that is an odd multiple of 4 wavelengths
A strip conductor 16 of length is formed adjacent to and parallel to the first strip conductor 16, with a second port 2 formed at one end and a fourth port 4 formed at the other end. A second strip conductor 17 equal in length to the first strip conductor 16
and a first conductor layer 18 on one side of the rectangular shape,
A second conductor layer 19 is provided on the other side, and a second conductor layer 19 is provided on the other side.
A length of the first strip conductor 16 is mounted on the dielectric substrate 15 such that the conductor layer 18 is connected to the first strip conductor 16 and the second conductor layer 19 is connected to the second strip conductor 17. The structure consists of a rectangular dielectric substrate 20 whose length is equal to .

[Effect]

According to the means of the present invention, the first strip conductor 16 and the second strip conductor 17 are the first conductor layer 18 and the second conductor layer formed on both sides of the rectangular dielectric substrate 20, respectively. Since they are connected to layer 19, first strip conductor 16 and second strip conductor 17 are coupled with a high degree of coupling even if the strip conductor spacing is relatively large.

Therefore, it is not necessary to form the first and second strip conductors using thin films that require complicated processing steps, and can be formed using other inexpensive methods such as etching copper foil. Further, even if the relative dielectric constant of the dielectric substrate 15 is low, it does not affect the degree of coupling, so a low-cost dielectric substrate that is easy to process can be used.

〔Example〕

The present invention will be specifically explained below with reference to illustrated examples. Note that the same reference numerals indicate the same objects throughout the figures.

FIG. 1 is a perspective view of one embodiment of the present invention, FIG. 2 is a perspective view of another embodiment, and FIG. 3 is a perspective view of a rectangular dielectric substrate of another embodiment.

In Figure 1, for example, Teflon (registered trademark)
Like glass, it has a small dielectric constant and is easy to process.
A lower conductor layer 6 made of copper foil or the like is provided on the entire lower surface of the inexpensive dielectric substrate 15.

A first strip conductor 16 having a length of approximately λg/4 (λg is the effective wavelength determined by the dielectric constant of the rectangular dielectric substrate) is disposed on the upper surface of the dielectric substrate 15.
is formed. Further, a second strip conductor 17 having the same length is formed close to the first strip conductor 16 (for example, at a spacing of 0.5 mm) and parallel to the first strip conductor 16.

At one end of the first strip conductor 16,
A first port 1 is connected at a right angle, and at the other end, parallel to the first port 1, a third port 3 is connected at a right angle to a first strip conductor 16.

Further, at the terminal of the second strip conductor 17 opposite to the terminal provided with the first port 1, a second strip conductor 17 is provided.
A second port 2 is connected at right angles, and at the other end, parallel to the second port 2, a second strip conductor 17 is connected at right angles.

The above circuit pattern can be easily formed by etching a copper foil layer formed on the surface of the dielectric substrate 15.

Reference numeral 20 denotes an elongated rectangular dielectric substrate having a desired dielectric constant, a desired width, and a length of λg/4.

A first conductor layer 18 is provided on the entire surface of one side surface in the longitudinal direction of the rectangular dielectric substrate 20.
A second conductor layer 19 is provided on the other side facing the conductor layer 18 .

The rectangular dielectric substrate 20 includes a first conductor layer 18,
A second conductor layer 19 is placed on the dielectric substrate 15 perpendicularly to the dielectric substrate 15 and parallel to and straddles the first strip conductor 16 and the second strip conductor 17. 18 is connected to the first strip conductor 16, and a second conductor layer 19 is connected to the second strip conductor 17 by soldering or the like and mounted.

As described above, the first strip conductor 16 and the second conductor layer 18 and the second conductor layer 19 are formed on both sides of the rectangular dielectric substrate 20 to face each other.
Since the strip conductors 17 are connected to each other, the first strip conductor 16 and the second strip conductor 17 can be connected to each other with a desired high degree of coupling (for example, -
3dB).

Therefore, for example, an input signal from the first port 1 is input to the third port 3 and the second port 2.
The light is output from the fourth port 4, and almost no light is emitted from the fourth port 4.

Incidentally, since the interval between the first and second strip conductors is relatively large and there is a margin, they can be formed by etching using inexpensive means. Also,
Even if the relative dielectric constant of the dielectric substrate 15 is low, it does not affect the degree of coupling, so a dielectric substrate that is easy to process can be used, resulting in low cost.

The ones in FIGS. 2 and 3 are directional couplers that output an input signal from a first port 1 from a second port 2 and a fourth port 4. In FIG.

In FIG. 2, the first strip conductor 16 and the second strip conductor 17 formed in parallel to the dielectric substrate 15 are cut approximately at the center, and the first strip conductor 16 is connected to the first port. It is separated into a strip conductor 16A on the port 1 side and a strip conductor 16B on the third port 3 side. Also, the second
The strip conductor 17 is separated into a strip conductor 17A on the second port 2 side and a strip conductor 17B on the fourth port 4 side.

The strip conductor 16B and the strip conductor 17A are connected by a connecting conductor pattern 31 that diagonally crosses the cut portion.

The first electrodes formed on both sides of the rectangular dielectric substrate 20
The conductor layer 18 and the second conductor layer 19 are both cut approximately at the center, and the first conductor layer 18 is cut into the conductor layer 18A on the first port 1 side and the conductor layer 18B on the third port 3 side. The second conductor layer 19 is separated from the conductor layer 19A on the second port 2 side and the fourth port 4 side.
It is separated into a side conductor layer 19B.

The conductor layer 18A and the conductor layer 19B are connected by a connecting conductor pattern 32 that diagonally crosses the center of the upper surface on the side opposite to the side in close contact with the dielectric substrate 15.

Therefore, for example, an input signal from the first port 1 is output from the second port 2 and the fourth port 4, and almost no signal is emitted from the third port 3.

In FIG. 3, the first conductor layer 18 formed on one side of the rectangular dielectric substrate 20 is cut approximately in the center into a key shape when viewed from the side.
A and a conductor layer 18B.

In addition, a second conductor layer 19 formed on the other surface
is cut into a key shape that is opposite to the first conductor layer 18 when viewed from the side, and is separated into a conductor layer 19A and a conductor layer 19B.

The conductor layer 18A and the conductor layer 19B are formed by through-hole conductors 4 passing through the rectangular dielectric substrate 20.
2, the conductor layer 18B and the conductor layer 19A
are connected to each other by a through-hole conductor 41.

The strip conductor on which such a rectangular dielectric substrate 20 is mounted is cut at the center to form strip conductors 16A, 16B and strip conductors 17A, 17B, as shown in FIG. The difference from the one in Figure 2 is that the connection conductor layer 31
and strip conductor 16B and strip conductor 17A
and are not connected.

A directional coupler with such a structure also has a second
It has the same directional function as the one shown.

〔Effect of the invention〕

As explained above, the present invention combines a first strip conductor and a second strip conductor provided in parallel on a dielectric substrate via another rectangular dielectric substrate. It not only has broadband and high coupling characteristics, but also has excellent practical effects such as the dielectric substrate material is inexpensive and easy to process, and the strip conductor is easy to process and low cost. .

[Brief explanation of drawings]

Fig. 1 is a perspective view of one embodiment of the present invention, Fig. 2 is a perspective view of another embodiment, Fig. 3 is a perspective view of a rectangular dielectric substrate of another embodiment, and Fig. 4 is a perspective view of a conventional rectangular dielectric substrate. FIG. 2 is a perspective view of a directional coupler. In the figure, 1 is the first port, 2 is the second port, 3 is the third port, 4 is the fourth port, 5
1 is a ceramic substrate, 6 is a lower conductor layer, 15 is a dielectric substrate, 16 is a first strip conductor, 17 is a second strip conductor, 18 is a first conductor layer, 19
are the second conductor layers, 18A, 18B, 19A, 19
B is a conductor layer, 20 is a rectangular dielectric substrate, 31, 3
Reference numeral 2 indicates a connection conductor pattern, and 41 and 42 indicate through-hole conductors.

Claims (1)

[Claims] 1. A device having a wavelength of 1/4 of the transmission frequency, which is formed on the surface of the dielectric substrate 15, and has a first port 1 at one terminal and a third port 3 at the other terminal. A first strip conductor 16 having an odd number of lengths, and a second port 2 formed in parallel with the first strip conductor 16, with a second port 2 at one end and a fourth port 4 at the other end. a second strip conductor 17 having a length equal to the length of the first strip conductor 16; a first conductor layer 18 on one side of the rectangular shape and a second conductor layer 18 on the other side; A conductor layer 19 is provided, the first
a conductor layer 18 on the first strip conductor 16;
The second conductor layer 19 is connected to the second strip conductor 1
The length of the first strip conductor 16 is mounted on the dielectric substrate 15 to connect to the first strip conductor 16, respectively.
1. A directional coupler comprising: a rectangular dielectric substrate 20 having a length equal to . 2 The first and second strip conductors 16,1
7, and the first and second conductor layers 18 and 19,
The first strip conductor 16A on the first port side connects to the strip conductor 17B on the fourth port side directly or through the cut conductor layer, and the third port side is cut approximately at the center of each conductor. side first
The directionality according to claim 1, characterized in that the strip conductors 16B are connected to the strip conductors 17A on the second port side directly or through cut conductor layers. combiner.