JP3630285B2 - High frequency transformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency transformer in which a high-frequency amplifying element is made to perform a push-pull operation using a balun transformer made of a coaxial cable.
[0002]
[Prior art]
Conventionally, when a push-pull operation of an amplifying element is performed in a high frequency band (particularly, UHF to microwave), a balun transformer as shown in FIG. 1 is used.
That is, in FIG. 3, 1a and 1b are amplification elements, 2Aa, 2Ab, 2Ba, and 2Bb are matching circuits provided at both ends of the amplification elements 1a and 1b, respectively, and the matching circuit 2Aa is a coaxial cable used as a balun transformer. The matching circuit 2Ab is similarly connected to the outer conductor side of the coaxial cable 3A, the matching circuit 2Ba is connected to the outer conductor side of the coaxial cable 3B used as a balun transformer, and the matching circuit 2Bb is connected to the core wire side of 3A. Similarly, it is connected to the core wire side of the coaxial cable 3B.
[0003]
Normally, the coaxial cables 3A and 3B used as balun transformers have a length of a quarter wavelength of the frequency to be used. As shown by an equivalent circuit in FIG. 3, the outer conductor side and the core wire side have reactance. As shown in FIG. 4, the balun transformer in the ideal state is such that the outer conductor on the input end side or output end side of the coaxial cable is grounded, and the amplifying element side is connected to the opposite terminal. .
[0004]
[Problems to be solved by the invention]
However, when the coaxial cable 3A (3B) shown in FIG. 5A is used for the balun transformer as in the conventional example, in reality, as shown in FIG. 5B, between the outer conductor of the coaxial cable and the ground. The short stub 4 is formed, an unnecessary impedance is generated, the matching band is limited, and the original daily balance is lost.
[0005]
Therefore, generally, as shown in FIG. 5C, the core wire of the coaxial cable 3A (3B) using the coaxial cable 5 having the same unnecessary impedance as the balun transformer formed between the outer conductor of the balun transformer and the ground. Connected to the side for good matching and balance.
[0006]
However, in this case, another expensive coaxial cable 5 is required in addition to the original balun transformer, and there is a problem that the cost is doubled.
[0007]
The present invention was made to solve the problems associated with the conventional example described above, and provides a high-frequency transformer that can ensure matching and balance of a balun transformer with an inexpensive configuration without using an expensive coaxial cable. With the goal.
[0008]
[Means for Solving the Problems]
The high-frequency transformer of the present invention is a high-frequency transformer in which a high-frequency amplifying element is pushed and pulled using a balun transformer formed of a coaxial cable, and the outer conductor of the balun transformer is interposed between the core wire of the balun transformer and the ground. A single wire having an impedance equivalent to the impedance between the ground and the ground is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a block diagram showing a main part of a balun transformer portion of a high-frequency transformer according to Embodiment 1 of the present invention.
In the high-frequency transformer shown in FIG. 1, although not shown, amplification elements 1a and 1b similar to the conventional example shown in FIG. 3 and matching circuits 2Aa, 2Ab provided at both ends of the amplification elements 1a and 1b, 2Ba, 2Bb, coaxial cables 3A, 3B used as balun transformers are provided, and a short stub 4 is formed between the outer conductor of the coaxial cable 3A (3B) and the ground, and an unnecessary impedance ZX is generated. However, this is a factor that the matching band is limited or that the original balance of the day is lost.
[0010]
As a new code, 6 is a single wire such as an annealed copper wire having the same impedance as the impedance ZX of the short stub 4 and provided between the core wire of the coaxial cable 3A (3B) and the ground. By providing this single wire 6, The balun transformer can be matched and balanced with an inexpensive configuration without using an expensive coaxial cable.
[0011]
That is, in the first embodiment, as in the conventional example shown in FIG. 5C, the same coaxial cable 5 as the coaxial cable 3A (3B) serving as a balun transformer having good matching and balance is used. If the impedance generated between the outer conductor of 3A (3B) and the ground is the same, there is no need to use the same coaxial cable as the balun transformer, as shown in FIG. It is noted that a good alignment state and balance can be realized even when the single wire 6 is used.
[0012]
In this way, in the high-frequency transformer in which the high-frequency amplifying element is operated to push-pull using the balun transformer formed of the coaxial cable 3A (3B), the outer conductor of the balun transformer is interposed between the core wire of the balun transformer and the ground. By providing a single wire 6 such as an annealed copper wire having an impedance equivalent to the impedance between the ground and the ground, it is possible to ensure the matching and balance of the balun transformer with an inexpensive configuration without using an expensive coaxial cable. Since it can be realized with an inexpensive single wire without using a semi-rigid cable, the component cost can be reduced to about 1/10 or less.
[0013]
Embodiment 2. FIG.
In the first embodiment described above, an impedance equivalent to the impedance of the short stub 4 between the outer conductor of the coaxial cable and the ground is provided between the core wire of the coaxial cable 3A (3B) as the balun transformer and the ground. In this embodiment 2, as shown in FIG. 2, a microstrip line 7 having an impedance equivalent to the impedance of the short stub 4 is used as a balun transformer. It is provided between the core wire of the coaxial cable 3A (3B) and the ground.
[0014]
In the second embodiment, similarly to the first embodiment, it is possible to provide a high-frequency transformer that can ensure the matching and balance of the balun transformer with an inexpensive configuration without using an expensive coaxial cable. The cost can be reduced to about 1/10 or less.
[0015]
【The invention's effect】
As described above, according to the present invention, in the high frequency transformer in which the high frequency amplifying element is operated to perform the push-pull operation using the balun transformer formed of the coaxial cable, the balun transformer is interposed between the core wire of the balun transformer and the ground. Since a single wire with an impedance equivalent to the impedance between the transformer's outer conductor and ground is provided, a high-frequency transformer that can ensure matching and balance of the balun transformer with an inexpensive configuration without using an expensive coaxial cable is provided. can do.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a main part of a balun transformer part of a high-frequency transformer according to Embodiment 1 of the present invention;
FIG. 2 is a configuration diagram showing a main part of a balun transformer part of a high-frequency transformer according to Embodiment 2 of the present invention;
FIG. 3 is a configuration diagram showing a high-frequency transformer according to a conventional example.
FIG. 4 is an explanatory view showing a balun transformer in an ideal state.
FIG. 5 is an explanatory diagram showing unnecessary impedance of the balun transformer and a means for eliminating it.
[Explanation of symbols]
1a, 1b Amplifying elements 3A, 3B Coaxial cable as balun transformer 4 Short stub 6 having impedance ZX Single wire 7 such as an annealed copper wire Microstrip

Claims (1)

In a high-frequency transformer that uses a balun transformer made of coaxial cable to push-pull the high-frequency amplifier,
A high-frequency transformer, wherein a single wire having an impedance equivalent to an impedance between an outer conductor of the balun transformer and the ground is provided between the core wire of the balun transformer and the ground.

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