JPH06177617A - Wide-band directional coupler - Google Patents

Abstract

(57) [Summary] [Objective] A tightly coupled characteristic is realized by feeding by a microstrip line formed on a dielectric substrate having a relatively low dielectric constant. [Structure] Two parallel lines 2 and 3 having a length of about 1/4 wavelength formed on both surfaces of a dielectric substrate 1 having a relatively low dielectric constant.
And feed lines 4,5, 6, and 7 which are connected to respective ends of the parallel lines 2 and 3 and which are formed from four feed microstrip lines extending from the ends of the parallel lines 2 and 3. , Connecting portions 2a, 2b, 3a, which connect the respective ends of the parallel lines to the respective feeding microstrip lines,
4 metal ground planes 8, 9, 1 formed close to 3b
It consists of 0 and 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband directional coupler, and more particularly, to a wideband incorporated as a power distributor in an integrated circuit having a microstrip line as a main line, or as a combiner, a phase shifter, a matching device, or the like. A tightly coupled directional coupler.

[0002]

2. Description of the Related Art Conventionally, as a wide band directional coupler of this type, there is one shown in FIGS. In the figure, the structure of the directional coupler 100 has a length of about 1/4 wavelength formed by sandwiching an air layer or a dielectric substrate 101 (here, the wavelength is the wavelength of the center frequency of the used frequency band). (Refer to FIG. 3), the coupled lines 102 and 103 made of a metal plate, and the coupled lines 102 and 103 surrounding the coupled lines 102 and 103.
No. 03 of the metal case 104 also serving as the ground plane, and the coupled lines 102, 103 with the metal case 104 as the ground plane.
Coaxial connectors 105, 1 connected to respective ends of the
It is composed of 06, 107 and 108. In this directional coupler 100, for example, when the connector 105 is an input terminal, the output terminal is the connector 106, the coupling output terminal is the connector 108, and the isolation terminal is the connector 107.

Coupling line 10 of the directional coupler 100
Reference numerals 2 and 103 denote transmission lines having the metal case 104 as a ground plane, but they are electrically coupled by being arranged in parallel with each other and operate as coupled transmission lines.

Coupling line 10 of the directional coupler 100
Since the elements 2 and 103 are electrically coupled to each other via the surfaces of the lines, they are so-called surface-coupled coupling lines, and the tight coupling characteristic can be easily obtained.

In the directional coupler 100, the metal case 104 as a ground plane is arranged in a plane different from that of the coupling lines 102 and 103, so that the feeding method uses a coaxial line.

An example of another conventional directional coupler using a surface coupling type coupled line is shown in FIGS. In the figure, the structure of the directional coupler 110 has a length of about ¼ wavelength formed by sandwiching the dielectric substrate 111 (here, the wavelength means the wavelength of the center frequency of the used frequency band). Coupled lines 112, 113 made of metal plates of
3, the feeding strip lines 115, 116, 117, 118 extending from the respective ends, the dielectric layers 119 arranged on both surfaces of the dielectric substrate, and formed outside the dielectric layers. It is composed of a metal ground plane 114.
In this directional coupler 110, for example, when the feeding strip line 115 is the input terminal, the output line is the line 11
6, the coupled output line is the line 118, and the isolation line is the line 117.

Coupling line 11 of the directional coupler 110
Reference numerals 2 and 113 are transmission lines having the metal ground plane 114 as a ground plane, but they are electrically coupled by being arranged in parallel with each other and operate as a coupled transmission line.

Coupling line 11 of the directional coupler 110
Since the lines 2 and 113 are electrically coupled to each other via the planes of the lines, they are so-called plane-coupling type coupled lines, and a tight coupling characteristic can be easily obtained.

[0009] In the directional coupler 110, strip line feeding is performed by forming a plurality of dielectric layers.

On the other hand, FIGS. 12 and 13 show another conventional directional coupler 130. In the figure, the directional coupler 13
In No. 0, the ground plane made of the metal surface 138 is formed on one surface of the dielectric substrate 131, and two microstrip lines are formed on the other surface. The portions of the microstrip lines that are parallel and close to each other are coupled lines 132, 13
It is 3. Further, the other microstrip line portions are feed lines 134, 135, 136, 137.
In this directional coupler 130, for example, the feed line 134
Is the input line, the output line is the line 135, the coupled output line is the line 137, and the isolation line is the line 136.
Becomes

The lines 132, 1 of the directional coupler 130
Reference numeral 33 is a transmission line having the metal surface 138 as a ground plane, but it is electrically coupled by being arranged in parallel with each other and operates as a coupled transmission line.

The coupling line 13 of the directional coupler 130
Since the lines 2 and 133 are electrically coupled to each other through the side faces of the lines, they are so-called side-coupling type coupling lines, and it is difficult to obtain a tight coupling characteristic with a normal dielectric substrate 131. As the dielectric substrate 131, a material having a high dielectric constant (for example, a relative dielectric constant of 10 or more) such as an alumina-based material is used.

As mentioned above, the conventional directional coupler is
This is a structure in which a feed line is connected to the coupled transmission line. When the directional coupler is used alone or is bonded as a component of a circuit, a directional coupler fed by a coaxial line like the directional coupler 100 may be used, but it is integrated. To form on the circuit board as one part of the circuit,
A directional coupler with a stripline or microstripline feed is suitable, such as the directional coupler 110 or the directional coupler 130.

[0014]

However, in a directional coupler such as the directional coupler 110, which is based on strip line feeding, it is necessary to make the dielectric substrate multilayer. Further, in order to obtain a tight coupling characteristic in a directional coupler using a side coupling type coupled line like the directional coupler 130, it is necessary to use a dielectric substrate having a high dielectric constant as the dielectric substrate. There was a problem.

The present invention has been made in view of the above points.
The purpose is to solve the above problems and to provide a tight coupling characteristic (for example, power supply by a microstrip line formed on a one-layer dielectric substrate having a relatively low dielectric constant (for example, relative dielectric constant of 5 or less)). It is to provide a broadband directional coupler having a coupling degree of 3 to 5 dB).

Another object of the present invention is to provide a broadband directional coupler which retains the required degree of coupling.

[0017]

The structure of the present invention for achieving the above object is as follows in a broadband directional coupler formed on both surfaces of a dielectric substrate.

(1) Two parallel lines having a length of about ¼ wavelength formed with the dielectric substrate in between, and connected to each end of the parallel lines and extending from the parallel lines. Is formed so as to be close to a connecting portion to which each of the four feeding microstrip lines, the respective ends of the parallel lines, and each of the feeding microstrip lines are connected, and is electrically connected to each other. And four metal ground planes connected together.

(2) It is characterized in that the metal ground plane is further formed close to the parallel lines to maintain a required degree of coupling.

[0020]

The broadband directional coupler configured as described above is realized by parallel lines without using a coupling line, but is equivalent to a so-called directional coupler using a surface coupling type coupling line. Tight coupling characteristics (for example, coupling degree 3 to 5 dB)
Is easily obtained. Further, since the parallel line does not require a ground plane and the ground plane for the feed line is formed on the same dielectric substrate as the parallel line, it can be formed on a single dielectric substrate. Further, since the ground plane is formed so as to be close to the connecting portion between the parallel line and the power feeding line, the reflection loss characteristic can be maintained well.

The broadband directional coupler has the ground plane formed on the same dielectric substrate as the parallel lines and is formed close to the parallel lines.
The degree of binding of dB can be maintained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. 1 to 4 show an embodiment of a broadband directional coupler according to the present invention, and FIG. 1 is a plan view showing a hybrid circuit having a coupling characteristic of 3 dB.
1 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is a circuit pattern diagram on the front surface in FIG. 1, and FIG. 4 is a circuit pattern diagram on the back surface in FIG. 1, which is the same shape as FIG.

1 to 4, 1 of the broadband directional coupler A is a dielectric substrate having a relative permittivity of 5 or less, for example, about 3 (3.2 to be exact), and 2 and 3 are the dielectrics. Board 1
Parallel lines formed on both sides of the copper foil with a length of about 1/4 wavelength of the center frequency used, and 4, 5, 6, and 7 are feeder lines. The parallel lines 2 and 3 are made of copper foil microstrip lines formed so as to extend in directions substantially perpendicular to each other and in directions different from each other.

Reference numerals 8, 9, 10 and 11 are ground planes of the copper foil, and each of them has the ends of the parallel lines 2 and 3 and the feed lines 4,5, 6 and 7. A uniform minute interval d (about 1 mm in this embodiment) is formed close to the connecting portions 2a, 2b, 3a, 3b to be connected, and is formed, for example, in an obliquely straight line with respect to the parallel lines 2 and 3 described above. The holes are formed close to each other, and the through holes 1
It is electrically connected via 2.

At the same time, the respective ground planes 8, 9, 10, 11
Is formed at a substantially central portion of each of the coupled lines 2 and 3 so as to be close to the coupled lines 2 and 3 with a uniform minute interval e (about 1 mm in this embodiment). The coupling length L of each of the ground planes 8, 9, 10, 11 facing the coupling lines 2 and 3 with a minute gap e therebetween is determined so as to obtain a coupling degree of about 3 dB.

In this embodiment, all of the hybrid circuit is formed on a single layer of dielectric substrate.

In FIG. 1, the feed lines 4, 5, 6,
When the line 4 of 7 is an input line, the output line is the line 5, the coupled output line is the line 7, and the isolation line is the line 6. FIG. 5 shows the return loss characteristic with respect to the frequency of the line 4 (input line), and FIG. 6 shows the directional characteristic with respect to the frequency between the line 4 (input line) and the line 6 (isolation line). Show.

FIG. 7 is a solid line of FIG. 7 showing the passage characteristic to the line 5 (output line) when the signal is input to the line 4 in the present embodiment, and the same coupling characteristic to the line 7 (coupling output line). It is shown by the dotted line in the figure. In the figure, V4, V5 and V7 are the potentials of the lines 4, 5 and 7.

FIGS. 5-7 show the frequency f ₁ (eg,
F ₁ (about 700 MHz) to about 700 MHz)
Over a wide band of 2.4 f ₁ (about 1700 MHz),
In addition to having a coupling degree of 3 ± 1 dB, excellent reflection loss and directional characteristics are obtained.

In particular, according to FIG. 7, there are two intersections of the passage characteristic (solid line portion) and the coupling characteristic (dotted line portion), and there are two frequencies (for example, 900 MHz and 1500 MH).
z) can be applied.

As described above, according to this embodiment, a broadband directional coupler having a coupling degree of about 3 dB is formed on a single dielectric substrate having a relatively low dielectric constant of about 3 relative permittivity. It can be realized by feeding by a microstrip line.

Note that the technique of the present invention is not limited to the technique in the above-described embodiment, and may be implemented by means of another aspect having a similar function, and the technique of the present invention can be variously modified within the scope of the above configuration. Can be changed or added.

[0033]

As is apparent from the above description, according to the broadband directional coupler of the present invention, each end of a parallel line having a length of about ¼ wavelength is formed with a dielectric substrate in between. Since a metal ground plane as a ground plane is formed in the vicinity of a connection portion to which each power feeding microstrip line is connected, by a microstrip line formed on a dielectric plate having a relatively low dielectric constant, It can be fed over a wide band with good coupling, reflection loss and directivity. At the same time, since it can be manufactured with a single-layer dielectric substrate, it can be easily integrally formed with other circuits by using the print printing technique.

Further, according to the present invention, the metal ground planes of the ground planes can be formed further close to the parallel lines of the parallel lines and can be maintained at a required coupling degree.

[Brief description of drawings]

FIG. 1 is a plan view of a hybrid circuit showing an embodiment of a wideband directional coupler according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a circuit pattern diagram of the surface of FIG.

FIG. 4 is a circuit pattern diagram of the back surface of FIG.

FIG. 5 is a reflection loss characteristic diagram with respect to frequency of the input line of the present embodiment.

FIG. 6 is a directional characteristic diagram with respect to frequency between the input line and the isolation line of the present embodiment.

FIG. 7 is a diagram showing a pass characteristic and a coupling characteristic with respect to a frequency according to the present embodiment.

FIG. 8 is a front view showing an example of a conventional wideband directional coupler.

9 is a sectional view taken along line IX-IX in FIG.

10 is a sectional view taken along line XX of FIG. 11, showing another example of a conventional wideband directional coupler.

11 is a sectional view taken along line XI-XI of FIG.

FIG. 12 is a plan view showing another example of a conventional wideband directional coupler.

13 is a sectional view taken along line XIII-XIII in FIG.

[Explanation of symbols]

 A Broadband directional coupler 1 Dielectric substrate 2,3 Parallel line 4,5,6,7 Feed line 8,9,10,11 Ground plane 2a, 2b, 3a, 3b Connection part d, e Minute gap L Coupling length

Front page continuation (72) Inventor Yoshio Ebine 2-10-1 Toranomon, Minato-ku, Tokyo NTT Mobile Communication Network Co., Ltd. (72) Inventor Jun Suganuma 2-10-1 Toranomon, Minato-ku, Tokyo No. NTT Mobile Communication Network Co., Ltd.

Claims (3)

[Claims] 1. A broadband directional coupler formed on both sides of a dielectric substrate, wherein a length of about 1/4 wavelength (wherein the wavelength is a wavelength of a working frequency) formed between the dielectric substrates. 2) parallel feed lines, a feed line made up of four feed microstrip lines extending from the ends of the parallel lines, each end of the parallel line, and each of the feed lines. A wideband directional coupler formed of four metal ground planes of the feed line which are electrically connected to each other and are formed in the vicinity of a connecting portion to which is connected. 2. The broadband directional coupler according to claim 1, wherein the dielectric substrate has a relatively low dielectric constant, for example, a relative dielectric constant of 5 or less. 3. The broadband directional coupler according to claim 1, wherein the metal ground plane is further formed near the parallel lines to maintain a required degree of coupling.