KR920010844B1 - Transformer for high frequency - Google Patents

Abstract

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Description

High frequency transformer for power distributor

1 is an external view showing one embodiment of the present invention.

2 and 3 are diagrams for explaining the action of the winding in the ferrite core of FIG.

4 is a diagram showing a high frequency transformer formed by winding the winding of FIG. 2 and the winding of FIG. 3 in the same core.

5a, b to 7a, b show a structural example of a transformer according to the present invention.

8A and 8B show a distributor and a circuit thereof constituted by using two high-frequency transformers shown in FIG.

9 is a diagram showing the signal transmission characteristics of the distributor used in the present invention.

10 is a view showing a state in which a distributor constructed using a high frequency transformer according to the present invention is mounted on a printed board.

11 shows signal transmission characteristics of a distributor according to the present invention.

12 is a view showing another example of the core used in the embodiment of the present invention.

FIG. 13 is a view showing a state in which a power distributor using a conventional high frequency transformer is mounted on a printed board. FIG.

14 is a circuit diagram of a general high frequency power divider.

15 is a diagram showing signal transmission characteristics of a conventional high frequency power divider.

* Explanation of symbols for main parts of the drawings

1 ferrite core 2 center through hole

3: surrounding through hole 4: conductive layer

5, 6: lead T: transformer

R: Absorption Resistance

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high frequency transformers, and more particularly, to transformers used in power dividers in TV frequency bands.

Although the frequency handled by the conventional power divider for TV broadcast reception includes CATV and UHF, the transformer used after 5 to 860 MHz is formed by winding a lead wire using a through hole in a columnar ferrite core having a through hole.

FIG. 13 shows a state in which a power divider is constructed by installing a high frequency transformer constructed using a conventional toroidal Herrite core on a printed board, and the input terminal (IN), output terminal (OUT), and distribution terminal formed on the printed board. The terminals of the transformers T1 and T2 are connected to the TAP and the absorption terminal, and the other grounded resistor R is connected to the absorption terminal.

FIG. 14 shows a circuit configuration of such a power divider, and is configured using two identical transformers T1 and T2. When the winding ratio of these transformers is N, each negative voltage in this transformer has the following relationship as described, for example in TV Communications, April 1967, p.80.

If the input voltage is E _i , the output voltage is E _o , and the transformer primary winding voltage is E _k ,

therefore,

Here, when the voltage E _R = 0 between both ends of the absorption resistance R in the figure is set to

Becomes

Substituting equation (4) into equation (1),

If you substitute equation (5) into equation (2),

Becomes Also, from the drawings

Becomes Substituting equation (2) into this equation (7),

It becomes Here, if Ei = 1 and substituted into Formulas (5), (6) and (7),

The characteristics of the transformer are determined by the ratio of the primary to the secondary turns of the transformer.

Compared to the ideal transformer described above, the actual transformer is inferior in characteristics. That is, as shown in FIG. 14, since the secondary winding of the transformer T1 is inserted in parallel between the input and the output, a simple setting of the winding ratio does not provide sufficient electrical characteristics. Failure to increase the secondary winding's impedance sufficiently will result in increased insertion loss or deterioration in input impedance. For this reason, although the number of turns of the secondary winding must be increased, the line capacitance increases, the actual impedance does not increase, and resonance occurs due to stray capacitance and inductance, thereby determining the upper limit of the use frequency.

FIG. 15 uses the toroidal ferrite core having a thickness of 3 mm, a length of 5 mm, a hole diameter of 1 mm, and an initial permeability of 3000 as the primary transformer 0.5 and the secondary winding 5.5 (winding ratio 1:11). The electrical characteristics of one case are shown. That is, due to the above-described reasons for the signal transmission characteristics between the input terminal IN, the output terminal OUT, and the distribution terminal TAP, characteristic degradation occurs at a frequency of about 1200 MHz or more. In particular, the deterioration of the isolation characteristics between the output terminal OUT and the distribution terminal TAP is remarkable.

Here, in recent years, with the onset of satellite broadcasting, the distribution at the intermediate frequency is required, so that the power divider for receiving TV broadcasts needs to handle higher frequencies, and especially in Europe, the band characteristics up to 1750 MHz Came to be required.

Such a high frequency is insufficient for a conventional power divider by a high frequency transformer. In other words, in a transformer made by winding a conventional conductor wire in a peri-core, the floating capacity between the windings is not only large, but also constant, so that it is necessary to adjust the difference of characteristics of each product. More results in deterioration of properties.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a power divider transformer whose characteristics do not deteriorate to a frequency band beyond the conventional TV broadcasting frequency band.

A pillar-shaped ferrite core having a center through hole and a plurality of peripheral through holes arranged at substantially concentric positions with respect to the central through hole, and at least one wire is inserted into the peripheral through hole. The present invention provides a high frequency transformer for a power divider having a winding made by inserting all the conductive wires of the peripheral through hole, and a conductive element connected to the ground by surrounding the entire outer circumferential surface of the ferrite core.

In the ferrite core, a plurality of peripheral through-holes are arranged in a substantially concentric position around the central through-hole and the central through-hole, and at least one wire is inserted into the plurality of peripheral through-holes. Then, all the conductors pass through the center through hole. When the conductor is inserted through, the guide grooves formed in the inner wall of the through hole not only guide the conductor but also maintain it at a predetermined position. The magnetic flux generated by the conducting wire inserted through each through hole does not leak to the outside because it passes through the closed magnetic path in the ferrite core, and the characteristic impedance is not affected by the leakage magnetic flux. Therefore, the characteristic impedance of the high frequency transformer is a predetermined value determined by the appearance of the conductive element and the conducting wire, the distance between the two, the permeability of the core interposed therebetween, and the dielectric constant. Moreover, the floating capacity is stable and there are fewer uncertainties due to the floating capacity.

According to the present invention, the winding is almost contained in the ferrite core, and since the outer circumferential surface of the ferrite core is covered by the conductive element, the leakage magnetic flux from the winding is small, so that the characteristic impedance is constant. In addition, since each winding is precisely arranged in a separate position by using the winding recommended through-hole of the ferrite core, the floating capacity between the windings can be reduced, and the use frequency band can be greatly expanded. In addition, if there is no variation in the floating capacity between the windings and the characteristic due to the floating capacity is constant, it is suitable for mass production. Moreover, since the winding only penetrates one line through each through hole, workability is good and it is optimal for mass production.

EXAMPLE

FIG. 1 shows the appearance of one embodiment of the present invention. In FIG. 1, (1) is a cylindrical ferrite core, with one through hole (2) in the center, and six (6) at its periphery. The through hole 3 is formed, and the conductor layer 4 is formed in the outer periphery. The primary winding is inserted into the central through hole 2, and the secondary winding is wound radially between the central through hole 2 and the surrounding through hole 3. Therefore, the first through wire of the primary winding and the seven through wire of the secondary winding pass through the center through hole 2.

2a, b and 3a, b show the signal source SG at one end thereof by passing the conductor 5 or 6 through the center through hole 2 or the peripheral through hole 3 of the ferrite core. The magnetic circuit behavior in the ferrite core in the case of connecting and terminating resistor (R) connected to the other end is examined. First, in the case of FIG. 2, when the electric wire i flows through the conducting wire 5 in the center through-hole 2, magnetic flux as shown by a broken line in FIG. 2b flows. On the other hand, in the case of FIG. 3, when the conducting wire 6 is inserted between the center through hole 2 and the peripheral through hole 3, current flows through the magnetic flux represented by the broken line in FIG. 3b. As a result, the magnetic flux by the conducting wire 5 and the magnetic flux by the conducting wire 6 are common to each other.

FIG. 4 shows a high frequency transformer formed by winding the winding of FIG. 2 and the winding of FIG. 3 in the same core. As shown in FIG. 4, the conductive wires 5 and 6 are inserted into the peripheral through holes 2 and 3 formed in the ferrite core 1, and the outer circumferential surface of the ferrite core 1 is wrapped with the conductive coating layer 4 have.

5a, b, 6a, b and 7a, b show an equalization circuit and an external view of a transformer according to the present invention.

5A and 5B show examples of high-frequency transformers for polarity inversion, and are used as components of a bal-un transformer or a hybrid circuit in the CATV field. The winding usually uses parallel two wires or coaxial wires.

6A and 6B show high-frequency transformers for impedance conversion configured in an autotrans form, and FIG. 7A-B show high-frequency transformers for impedance conversion configured as secondary winding transformers. In the field of CATV, it is widely used as a 2: 1 impedance converter of 75 ohms to 37.5 ohms.

8A and 8B show the distributor and its circuit which constitute the distributor using two high frequency transformers shown in FIG. As shown in FIG. 8A, one end a1 of the primary winding of one transformer T1 is connected to the input terminal IN, and the other end a1 'is connected to the output terminal OUT. One end b1 of the secondary winding is connected to the conductive layer 4, and the other end b1 ′ is connected to the absorption terminal DUM, and the absorption terminal DUM is grounded through the resistor R. One end (a2 ') of the primary winding to another transformer (T2) is grounded through the absorption resistor (R), the other end (a2) is connected to the distribution terminal (TAP), and one end of the secondary winding (b2). ′) Is connected to the output terminal (OUT), and the other end (b2) is grounded. In this way, the distributor as shown in FIG. 8B is comprised.

9 shows an example of a core used in another embodiment of the present invention, in which a six-conductor wire is inserted at a center position of the ferrite core 1 so that a planar shape is in the form of a six-wire bundle. Through holes are made, and each of the peripheral through holes 3 is made of six for one strand.

10 shows an embodiment of the present invention, in which two transformers T1 and T2 are connected to an input terminal IN, an output terminal OUT, and a distribution terminal TAP made on a printed board, and to an absorption terminal. It is made by connecting resistor R.

11 shows signal transmission characteristics of the power splitter using the high frequency transformer according to the present invention, wherein the diameter of the center through hole is 1.5 mm, the diameter of the peripheral through hole is 1.0 mm, μi = 3000 The 0.18mm diameter wound around the ferrite core constituted a high frequency transformer made by winding a polyurethane wire. Although the characteristic of FIG. 11 becomes clear compared with the characteristic of FIG. 15 already described, the transmission characteristic between the output terminal OUT and the distribution terminal TAP is flat to 2000 MHz, and the isolation characteristic is improved.

FIG. 12 shows another example of the core used in the embodiment of the present invention. The center through hole 2 is formed at the eccentric position of the ferrite core 1, and the wedge shape is centered around the center through hole 2. As shown in FIG. The peripheral through hole 3 is arrange | positioned so that it may be made.

Claims (4)

A pillar-shaped ferrite core 1 having a plurality of peripheral through-holes 3 arranged in a substantially concentric position with respect to the central through-hole 2 and the central through-hole 2, and a peripheral through-hole 3 to 1 Wires of more than one line are inserted, and the center through-hole 2 has a winding wound so as to insert all the conductors of the peripheral through-hole 3, and a conductive element surrounding the entire outer circumferential surface of the ferrite core 1 to be grounded. High frequency transformer for power distributor. 2. The high frequency transformer of claim 1, wherein the conductive element is a metal pipe. 2. The high frequency transformer of claim 1, wherein the conductive element is a metal plate or foil. The high frequency transformer of claim 1, wherein the conductive element is formed by printing or depositing a conductive material.

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