JP2565127B2 - 3dB 90 ° hybrid directional coupler - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a 3 dB 90 ° hybrid directional coupler used in high frequency circuits.

[0002]

2. Description of the Related Art A conventionally known 1/4 wavelength distribution coupling type hybrid directional coupler has a 1 / th layer on a first layer surface (front surface) of a printed circuit board P2 having a thickness h as shown in FIGS. Parallel strip lines 20 and 21 of four wavelengths are formed, and a ground pattern (ground plane) 2 is formed on the second layer surface (back surface).
2 is formed, and two line conductors are in electric field coupling and magnetic field coupling. Here, the directional coupling condition is that the electrical length of the even-mode and odd-mode distributed lines is θ.
_{When e} , θ _o , the characteristic impedances of the even mode and the odd mode are Z _e , Z _o , and the terminal impedance is Z, Given in.

In the conventional structure, in order to obtain the coupling degree of 3 dB, the line spacing S between the parallel strip lines 20 and 21 must be made very small. Note that W is the width of the strip lines 20 and 21. However, the line spacing S
As shown in FIGS. 11A and 11B, the electric field distribution in the air in the odd mode becomes larger than that in the even mode as θ becomes smaller as θ _e > θ _o , as shown in FIGS. And the directional condition of the above equation is not satisfied. Actually 3d
In order to realize the coupling degree of B, the line spacing S becomes a dimension that is difficult to manufacture.

An overlay method is known as one of the solutions. In the hybrid directional coupler having this structure, as shown in FIG.
1, a dielectric layer 23 is added on top of the dielectric layer 2
A coupling line 24 is formed on the wiring 3. In this structure, since the electric field is in the dielectric layer 23 in both even and odd modes, θ _e = θ _o holds as near equality,
The directional condition of the above formula can be satisfied. At the same time, the coupling line 24
With the addition of, the degree of coupling can be increased and the degree of coupling of 3 dB can be realized.

[0005]

However, in the above-mentioned overlay method, the dielectric layer 23 is provided on the parallel strip lines 20 and 21 as shown in FIG.
Since the coupling line 24 is further formed on the structure 3, there is a problem that the structure is complicated and the manufacturing cost is high, and a hybrid directional coupler which has a simple structure and can be configured only by a printed circuit board is desired. It was rare.

Japanese Patent Laid-Open No. 60-116202 discloses a connection method in which a through hole is not used to connect the slot line on the lower surface side of the printed board and the strip line on the upper surface side, but 3 dB 90 °. The hybrid directional coupler is formed only on the upper surface side of the printed circuit board, and there is no description about improvement of this hybrid directional coupler.

Further, Japanese Patent Application Laid-Open No. 1-190014 describes an improvement of a microwave balanced modulator in which all of a microslip line circuit and a nonlinear element for balanced modulation are provided on the surface of a dielectric substrate. However, there is no description about the improvement of the coupling degree of the 3 dB 90 ° hybrid directional coupler.

The present invention has been proposed to solve the problems of the prior art, and an object thereof is to provide a 3 dB 90 ° hybrid directional coupler which can be realized with a simple structure using only a printed circuit board. To do.

[0009]

To achieve this object, a 3 dB 90 ° hybrid directional coupler according to the present invention is symmetrically formed on both front and back surfaces of a printed circuit board and has four line ends of each strip line. Is a configuration including a coplanar line serving as an input / output port and an open stub line provided in each of the input / output ports for impedance matching.

In addition, the 3 dB 90 ° hybrid directional coupler according to the present invention is formed symmetrically on both front and back surfaces of a printed circuit board, and four line ends of each strip line serve as input / output ports and coplanar lines. An open stub line provided for each of the input / output ports for impedance matching, and an open stub line provided at the center position of the strip line for adjusting the coupling degree of the strip lines on both surfaces of the printed circuit board is there.

[0011]

According to the above-mentioned structure, since the strip lines on both sides of the printed circuit board are opposed to each other, the degree of coupling can be increased and the degree of coupling of 3 dB can be realized. Further, in this structure, since there is no difference in the propagation velocities in the even mode and the odd mode, the condition of θ _e = θ _o can be satisfied.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a 3 dB 90 ° hybrid directional coupler according to the present invention will be described in detail below with reference to the drawings. FIG. 1A shows a first layer surface pattern diagram of this hybrid directional coupler, and FIG. 1B shows a second layer surface pattern diagram. Further, FIG. 2 shows a sectional view taken along the line AA. FIG. 3 is an equivalent circuit diagram. In this equivalent circuit, C is capacitance and L is inductance. In these figures, strip lines 5 and 8 having line lengths of ¼ wavelength and ground patterns 6 and 9 are provided on both the first layer surface (front surface) and the second layer surface (back surface) of the printed board P1 having a thickness h.
Symmetrical coplanar lines 7 and 10 are formed, and the four line ends are the input / output port 1 and
It is 2, 3, and 4. By the strip lines 5 and 8 and the ground patterns 6 and 9, electric field coupling and magnetic field coupling,
A coupling degree of 3 dB is realized.

In practice, since the input / output ports 1, 2, 3, 4 need to be arranged on the first layer surface, the input / output ports 1, 2 connected to the strip line 8 on the second layer surface side are the first layer surface. Are formed on the strip line 8 and the input / output port 1,
2 are connected by through holes 11 and 12. Open stub lines 13, 14, 15, and 16 for impedance matching and setting the port impedance to 50Ω are formed on the input / output ports 1, 2, 3, and 4, respectively.

Further, open stub lines 17 and 18 are formed at the central positions of the strip lines 5 and 8 for adjusting the coupling degree of the lines on both sides. The open stub lines 17 and 18 have a space S between the strip lines 5 and 8 and the ground patterns 6 and 9,
It is used when the degree of coupling cannot be adjusted only by the line width W.

In the 3 dB 90 ° hybrid directional coupler constructed as described above, there is no difference in the propagation velocities in the even mode and the odd mode as shown in the electric field distributions in FIGS. 4 (a) and 4 (b). The condition of θ _e = θ _o can be satisfied.

Further, since the strip lines 5 and 8 on both sides of the printed circuit board are opposed to each other with the substrate interposed therebetween, a high degree of coupling can be obtained and a coupling degree of 3 dB can be realized.

5 to 8 show, for example, the center frequency 650.
It is the actual measurement data considering the band in MH. In this hybrid directional coupler, when a signal is input to port 1 as shown in FIG. 5, the signals are equally divided and output to symmetrical ports 2 and 3, and the phase difference is 90 ° as shown in FIG. . Also, as shown in FIG. 7, port 1 which is a diagonal port
, 4 and ports 2 and 3 are isolated from each other,
There is no communication, and adjacent ports have communication with each other. Each port is symmetrical and there is no distinction between input and output ports.
FIG. 8 shows the return loss. In FIG. 5, S
₂₁ is the output characteristic from the port 2 when the input is put into the port 1, and S ₃₁ is the output characteristic when the input is put into the port 1.
This is the output characteristic from port 3.

In the above-described embodiment, the open stub lines 17 and 18 are provided at the central positions of the strip lines 5 and 8, respectively, but only the space S between the strip lines 5 and 8 and the ground patterns 6 and 9 and the line width W are provided. If the degree of coupling can be adjusted with, open stub lines 17, 18
It is also possible to have an embodiment in which no is provided.

Further, the pattern shape is not limited to the above-mentioned embodiment, and it can be freely set within a range in which the interval S between the strip lines 5 and 8 and the ground patterns 6 and 9 and the line length of ¼ wavelength can be maintained. You can change the layout.

[0020]

As described above, according to the present invention, the structure in which the symmetrical coplanar lines are arranged on both surfaces of the printed circuit board is simpler than the conventional parallel strip line structure. 90 dB with a simple structure
Realize the characteristics of a hybrid directional coupler. As a result, manufacturing can be performed only by printing the pattern on the printed circuit board, and the manufacturing cost can be kept low. Also,
Since both sides of the printed circuit board are used, the area occupied by the printed circuit board can be reduced and the size can be reduced. Further, there is an advantage that the shape can be changed within a range in which the distance between the strip line and the ground pattern and the line length of the strip line are maintained, and the degree of freedom of layout is high.

[Brief description of drawings]

1 shows an embodiment of a 3 dB 90 ° hybrid directional coupler according to the present invention, (a) is a plan view of the hybrid directional coupler, and (b) is a rear view thereof.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an equivalent circuit diagram of the hybrid directional coupler.

FIG. 4 is an explanatory view showing an electric field distribution of the hybrid directional coupler, where (a) shows an even mode and (b) shows an odd mode.

FIG. 5 is a measured characteristic diagram showing the output characteristic of the hybrid directional coupler.

FIG. 6 is a measured characteristic diagram showing a phase difference characteristic of the hybrid directional coupler.

FIG. 7 is a measured characteristic diagram showing isolation characteristics of the hybrid directional coupler.

FIG. 8 is a measured characteristic diagram showing a return loss characteristic of the hybrid directional coupler.

FIG. 9 is a plan view showing a conventional 1/4 wavelength distributed coupling type hybrid directional coupler.

10 is a cross-sectional view taken along the line BB of FIG.

FIG. 11 is an explanatory diagram showing an electric field distribution of a conventional hybrid directional coupler, where (a) is an even mode and (b) is a diagram.
Indicates the case of odd mode.

FIG. 12 is a cross-sectional view showing a hybrid directional coupler according to a conventional overlay method.

[Explanation of symbols]

 1,2,3,4 I / O ports 5,8 Strip line 6,9 Ground pattern 7,10 Coplanar line 11,12 Through hole 13,14,15,16 Open stub line 17,18 Open stub line

Claims (2)

(57) [Claims] 1. A coplanar line, which is symmetrically formed on both front and back surfaces of a printed circuit board and has four line ends of each stripline as input / output ports, and the above-mentioned input / output ports for impedance matching. 3 with an open stub line
dB 90 ° hybrid directional coupler. 2. A coplanar line, which is formed symmetrically on both front and back surfaces of a printed circuit board and has four line ends of each strip line as input / output ports, and the above-mentioned input / output ports for impedance matching. A 3 dB 90 ° hybrid directional coupler comprising an open stub line and an open stub line provided at a central position of the strip line for adjusting a coupling degree of the strip lines on both surfaces of the printed circuit board.