JPS6147001B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a directional coupler that is constructed of slot lines and strip lines and is capable of achieving any degree of coupling, particularly strong coupling.

In a conventional directional coupler, as shown in FIGS. 1 and 2, a conductor layer 12 is formed on the entire surface of an insulating substrate 11, and two parallel conductors are formed close to each other on the other surface of the insulating substrate 12. The two microstrip lines 13 and 14 are arranged close to each other. Microstrip lines are continuously formed at both ends of each microstrip line 13, 14 at substantially right angles to each other on the outside, and these are used as input/output ports _P1 to _P4, respectively. Input from port P ₁ is input to the port at any rate
It is divided into P ₂ and P ₃ and does not appear on port P ₄ . The division ratio is microstrip line 13,1
It is determined by the line width and line spacing of 4. The narrower the line spacing, the more microstrip line 1
The coupling between 3 and 14 becomes stronger, and the output from port _P2 increases. However, in manufacturing, there is a limit to accuracy in achieving narrow line spacing, which is 3 to 4 dB.
It has been difficult to obtain a tightly coupled coupled line.
Therefore, the conventional type shown in FIG. 1 is generally used as a directional coupler with a weak coupling degree, and has the disadvantage that it cannot be used with a directional coupler that requires close coupling.

In order to solve these drawbacks, the present invention uses a slot line and a microstrip line to make it possible to have a structure with strong coupling.

FIGS. 3 and 4 show an example of a directional coupler according to the present invention, in which a conductor layer 12 is formed on the entire surface of an insulating substrate 11, and a coupling slot line 16 is formed on the conductor layer 12. Slot lines 1 are connected to both ends of the coupling slot line 16 so as to be on the outside of each other and perpendicular to the coupling slot line 16.
7, 18, 19 and 20 are formed, and these slot lines 17 to 20 are connected to input/output ports P1 to _P1 , respectively.
It is said to be P ₄ . A microstrip line 21 is formed by forming parallel conductors on the other surface of the substrate 11, facing the coupling slot line 16 via the substrate 11. The microstrip line 21 has a microstrip line with a length of 1/4 of the wavelength used, which is connected to the outer side of the branch part 22 of the slot lines 16, 17, 18 and the branch part 23 of the slot lines 16, 19, 20. Extension parts 24 and 25 are formed, and both ends of the microstrip line 21, ie, the branch parts 22 and 23, are short-circuited to the conductor layer 12 at high frequency.

In the configuration shown in FIGS. 3 and 4, the input signal from port P ₁ is branched to port P ₂ and the coupling slot line 16 at the branch section 22, and is also branched to the microstrip line 21. The opposing portions 26 and 27 of the conductor layer 12 on one side and the other side of the slit and the conductor of the microstrip line 21 to constitute the slot line 16 are two wires connected in parallel and close to each other. It acts as a railway line. The input signal from port P ₁ is branched to the opposing portion 26 at the branching section 22 and the branched signal is coupled to the opposing portion 27 . Therefore, the same effect as the directional coupler shown in FIGS. 1 and 2 is performed, and the input signal from port P ₁ is routed to ports P ₂ and P ₃ .
It is divided at an arbitrary ratio based on the degree phase difference and does not appear at port _P4 . In this case, the degree of coupling is the slot line 1
By changing the slot width W ₁ of the microstrip line 21 and the conductor width W ₂ of the microstrip line 21, it can be determined arbitrarily, and a tightly coupled line can be easily constructed.

FIG. 5 also shows an embodiment of the present invention, in which instead of shorting both ends of the microstrip line 21 with the extensions 24 and 25 of the microstrip line, shorting ground conductors 28 and 29 are used to short-circuit the microstrip line 21. Both ends of the line 21 are connected to the conductor layer 12 through the substrate 11.
It is connected to short circuit.

For example, to achieve a coupling degree of 3 dB, when the load impedance is 50 Ω, the thickness of the substrate 11 is 300 μm, and the dielectric constant is 9.6, the gap between the microstrip lines 13 and 14 is The width is approximately several μm, which is difficult to achieve. On the other hand, in the directional coupling of the present invention, the slot width _W1 is 30 μm under the same conditions, which can be easily realized.

As described above, according to the directional coupler of the present invention, the slot width and the width of the microstrip line 21 are
By changing the width W ₂ and the width W ₁ of the slot line 16, it is possible to realize a coupled line from coarse coupling to close coupling, and even a 3 bB hybrid with a degree of close coupling of 3 bB can be easily realized.

As explained above, according to the present invention, a microstrip line and a slot line are provided on one side of the board and are coupled to each other, so that coupling lines ranging from coarse coupling to close coupling can be realized. This has the advantage that 3bB hybrids can be easily realized.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a conventional microstrip coupled line, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a plan view showing an embodiment of a directional coupler according to the present invention. FIG. 4 is a sectional view taken along the line BB, and FIG. 5 is a plan view showing another embodiment of the present invention. P ₁ , P ₂ , P ₃ , and P ₄ : input/output port, 11: insulating substrate, 12: conductor layer, 16: coupling slot line, 21: microstrip line, 24, 2
5: Extension of quarter-wavelength microstrip line, 28, 29: Short-circuit conductor.

Claims (1)

[Claims] 1. A conductor layer is formed on one surface of an insulating substrate, a coupling slot line is formed on the conductor layer, and a first and second slot line and a third and fourth slot line are provided at both ends of the coupling slot line, respectively. two are connected, the first, second, third and fourth
A slot line is used as an input/output port, and a microstrip line is formed on the other surface of the insulating substrate, facing the coupling slot line via the substrate, and parallel to the slot line. Both ends of the line are the first, second, third and fourth lines.
When looking outside from the branch point with the slot line, the slot line that is short-circuited to the above conductor layer at the operating frequency.
Microstrip directional coupler.