JPH03171901A - Directional coupler of center frequency variable type - Google Patents

Abstract

PURPOSE:To adjust the center frequency without changing the length of a coupling line by connecting conjugate terminals of two pieces of directional couplers by a pair of connecting lines, and also, making the length of at least one connecting line variable. CONSTITUTION:A pair of directional couplers 1, 2 are constituted of balanced coupling lines. Also, these directional couplers 1, 2 are constituted so that conjugate terminals are connected mutually by connecting lines 3, 4, and also, one line, in this case, line length of the connecting line 3 is variable. That is, terminals 9, 11 of each directional coupler 1, 2 are connected mutually by the variable length connecting line 3 whose line length is variable, and also, terminals 10, 12 are connected mutually by the fixed length connecting line 4 whose line length is fixed. In such a way, its center frequency can be varied and adjusted arbitrarily, and the directional coupler which can be applied to a wide frequency range is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a directional coupler used in a power combiner or power divider of a communication device, and in particular to a directional coupler that can adjust changes in center frequency. Concerning vessels.

[Conventional technology]

Conventionally, this type of directional coupler has been constructed as a directional coupler 20 consisting of a pair of quarter-wave balanced coupled lines, as shown in FIG. [Problems to be Solved by the Invention] In the conventional directional coupler described above, the length of the balanced coupling line is 1/4 wavelength, so the frequency is limited and it is necessary to balance each required frequency. There is a problem in that the length of the coupled line must be selected.

An object of the present invention is to provide a directional coupler whose center frequency can be adjusted without changing the length of the coupling line.

[Means to solve the problem]

In the directional coupler of the present invention, the conjugate terminals of two directional couplers are connected by a pair of connection lines, and the length of at least one of the connection lines is configured to be variable.

[Effect]

With this structure, it is possible to adjust the center frequency of the directional coupler by adjusting the electrical length of the variable length connection line. [Example] Next, the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of one embodiment of the present invention.
An example in which the present invention is applied to a dB directional coupler is shown.

In the figure, 1 and 2 are a pair of directional couplers, each consisting of a balanced coupling line of 1/4 wavelength for the required frequency. These directional couplers 1 and 2
has a coupling amount of 0.688 dB or less at the center frequency, which is tighter than 3 dB. These directional couplers 1 and 2 have their conjugate terminals connected to each other by a connection line 3.4, and the line length of one line, here the connection line 3, is configured to be variable. That is, the terminals 9 and 11 of each directional coupler 1.2 are connected to each other by a variable-length connection line 3 whose line length is variable, and the terminals 10 and 12 are connected to each other by a fixed-length connection line 4 whose line length is constant. is connected to.

As a result, the directional coupler 1.2 and the connection lines 3, 4
As a result, a signal input from terminal 5 is equally distributed to terminal 6 and terminal 7, and no signal appears at terminal 8, forming a 3 dB directional coupler.

Next, the operation will be explained. First, the input/output voltage of a directional coupler is expressed by the following equation, as is well known.

E9 jCsinθ E A E1. (1 c2) I/2 where,
A is (1 − e ”)”” cosθ+j s
inθ, E is the human power voltage, E, is the output voltage of terminal 9 when terminal 5 is human power, EIO is the output voltage to terminal 10,
θ is the electrical length of the balanced coupled line, and C is the coupling coefficient.

The voltage of E is outputted to the terminal 9 as a voltage E69 according to the following equation.

E69=E9 e-”' (j C sinθ) /A
Here, θ1 is the electrical length of the connection line 3.

Similarly, the voltage of E, outputted to terminal 7 as voltage El9 is E,q = E,e - Jol (l -
C2) l/Z/A also E,. Similarly, the voltage at terminal 6 is E&lO=E+o6-j" (I
C2)""/A terminal 7 has E, +o = E1(1e-"z (j C sin θ)
/A? Here, θ2 is the electrical length of the connection line 4.

The voltage E6 finally output to the terminal 6 and the voltage E output to the terminal 7 are E b = E bq + E 61.

E? =ET? +E■.

It is. For example, if θ=90° and θ1=θ2, then E
& = (2C”-1)E E, =2C (1-C”)”ZE, IE
&l=lEtl condition is C=0.9238
8 or C = 0.38268. C=0.9
2388 has a coupling amount of 0.688 dB, and the input/output characteristics of a single directional coupler are shown in Figure 2. Also, C
= 0.38268 is a coupling amount of 8.343dB, and in the range from 0.688dB to 8.343dB, θ is 1
The range is from 0 degrees to 170 degrees. As is well known, all signals input from terminal 5 are output to terminals 6 and 7, so by selecting θ1 to an appropriate length, IE &
+=lEtl.

However, E6 and E? Since the phase difference of changes with θ1,
In order to keep the phase difference constant like in the conventional 3 dB directional coupler, it is necessary to match the phases at the line lengths on the output side of terminals 6 and 7.

In addition, in the present invention, the connection line 4 may also be configured as a variable length line.

〔Effect of the invention〕

As explained above, the present invention has a structure in which the length of at least one of a pair of connection lines connecting between the conjugate terminals of two directional couplers is varied, so that the center frequency can be adjusted at an arbitrary value. This has the effect of making it possible to obtain a directional coupler that can be used over a wide frequency range.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of the directional coupler of the present invention, Fig. 2 is a diagram showing an example of the human output characteristics of the directional coupler of Fig. 1, and Fig. 3 is a circuit diagram of a conventional directional coupler. It is a diagram. 1, 2... Directional coupler, 3... Variable length coupled line,
4...Fixed length coupled line, 5~l2...Terminal, 20.
...Conventional directional coupler.

Claims (1)

[Claims] 1. Two directional couplers configured with a pair of balanced coupling lines are provided, the conjugate terminals of each directional coupler are connected by a pair of connection lines, and the length of at least one of the connection lines is variable. A variable center frequency type directional coupler.