SURGE PROTECTOR HAVING IMPROVED I-SHAPED LOAD STRUCTURE

Provided is a surge protector having an improved I-shaped load structure. The surge protector includes an outside conductor provided with input and output terminals on both sides thereof, an input terminal configured such that a high frequency signal is input from the outside thereto, an output terminal configured such that a high frequency signal is output therefrom, an inside conductor disposed inside the outside conductor to electrically connect the input and output terminals to each other, and an I-shaped load configured such that a lower end thereof is connected from a center of the outside conductor to the inside conductor and an upper end thereof is connected to the outside conductor. A dielectric partition is formed to have a predetermined height in a direction from the bottom of the I-shaped load to the top thereof.

CROSS REFERENCE

Applicant claims foreign priority under Paris Convention and 35 U.S.C. §119 to Korean Patent Application No. 10-2013-0122456, filed 15 Oct. 2013, with the Korean Intellectual Property Office, where the entire contents are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a surge protector and, more particularly, to a technology that is capable of considerably reducing the length of an I-shaped short-circuit load that is connected to the inside conductor of a surge protector for a coaxial cable and discharges a surge frequency signal through a grounded outside conductor.

2. Description of the Related Art

Generally, in balanced lines, the characteristic impedances of two lines are the same, and thus the amounts of energy induced to the two lines are the same even when they are exposed to a lightning surge. Accordingly, damage attributable to a lightning surge acting between the lines is not great, but a lightning surge voltage acting between the lines and ground is problematic.

In contrast, in unbalanced lines such as a coaxial cable, the characteristic impedances of an inside conductor and an outside conductor are not the same, and thus the amounts of energy induced to the two lines are not the same when they are exposed to a lightning surge. Accordingly, damage attributable to a lightning surge acting between the lines is relatively great.

Therefore, surge protective devices (SPDs) that limit an excessive voltage attributable to a lightning surge and discharge a surge current are widely used.

In RF theory, L-shaped resonant filters are known as filters for blocking specific frequency components. Two types of L-shaped resonant filters are illustrated inFIG. 1AandFIG. 1B.

L-shaped resonant filters are filters that include a primary line100and an L-shaped load110spaced apart from the primary line100by a predetermined distance and configured such that a vertical line111and a lateral line112are connected in an L shape.FIG. 1Aillustrates an L-shaped resonant filter in which the upper end of the vertical line111of an L-shaped load110is open and a vertical line111and a lateral line112are each formed to have a length of ½λ. In contrast,FIG. 1billustrates an L-shaped resonant filter in which the upper end of the vertical line111of an L-shaped load110is short-circuited and a vertical line111and a lateral line112are formed to have a length of ¼λ and a length of ½λ, respectively.

Such an L-shaped resonant filter is a kind of band stop filter, and may be configured to allow an L-shaped load to have a length that causes resonance in conjunction with a frequency required to be filtered out and to thereby attenuate a signal of the frequency required to be filtered out.

Meanwhile, such L-shaped resonant filters are known to be excellent in terms of filter performance with respect to signals having general strengths.

Since a surge is composed of specific frequency components, the use of an L-shaped resonant filter as a surge protector may be taken into consideration. However, a surge has the characteristic of a large amount of energy, and thus sufficient attenuation cannot be achieved only with resonance, with the result that the problem in which surge frequencies of 20 KHz to 20 MHz cannot be filtered out, occurs, unlike in theory.

Furthermore, assuming that the center frequency of a surge is 1 MHz, λ=c/f=3×108/106=300 m in order to resonate with the center frequency of the surge. Even when the vertical line111of the L-shaped load has a length of ¼λ, the length thereof is 75 m, which is very long. Accordingly, the problem of actual implementation being difficult occurs.

Therefore, a surge protector has been proposed that has the characteristic of a band pass filter that only passes a signal in a desired frequency band because an I-shaped load composed of only a vertical line is used in an L-shaped resonant filter.

FIG. 2illustrates an example of a surge protector using a conventional I-shaped load structure. Referring toFIG. 2, the surge protector using a conventional I-shaped load structure includes input and output terminals101and102disposed on both sides of a housing105and configured to connect with a coaxial cable, equipment or the like, a primary line103configured to electrically connect the input and output terminals to each other, and an I-shaped load104connected to the housing105at an end thereof and configured to pass through the center of the housing105. A space around the I-shaped load104is filled with air.

The surge protector using a conventional I-shaped load structure has the characteristic of resonating with a desired frequency and thus passing only the corresponding frequency and suppressing signals in the other frequency bands. If the desired frequency band is 100 MHz and the length of the I-shaped load104is λ, λ=c/f=3×108/108=3 m. Accordingly, the surge protector has the advantage of achieving a shorter load length than that of the L-shaped resonant filter, but has the disadvantage of the length being still too long to be applied to actual surge protectors.

In order to reduce the length of the I-shaped load104, the length of the I-shaped load104can be shortened using the characteristics of achieving a 1 wavelength effect with a ¼ wavelength and achieving a ½ wavelength effect with a ⅛ wavelength.

When the I-shaped load104has a length of ¼λ, a length of ⅛λ and a length of 1/16λ, the length thereof can be reduced to 75 cm, 37.5 cm, and 18.75 cm, respectively.

However, when the I-shaped load104is implemented based on a short wavelength, the disadvantage of insertion loss occurs.

In another conventional technology, in order to reduce the protruding height of an I-shaped load while reducing insertion loss, the I-shaped load is configured in a coil form, but it is limited in the reduction of the protruding height of the I-shaped load to a sufficient length.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to considerably reduce the length of an I-shaped load by filling a space between the end of the I-shaped load and a ground with a ferroelectric substance, thereby providing the effect of extending the load, which is proportional to a dielectric constant.

In accordance with an aspect of the present invention, there is provided a surge protector having an improved I-shaped load structure, including an outside conductor provided with input and output terminals on both sides thereof; an input terminal configured such that a high frequency signal is input from the outside thereto; an output terminal configured such that a high frequency signal is output therefrom; an inside conductor disposed inside the outside conductor to electrically connect the input and output terminals to each other; and an I-shaped load configured such that a lower end thereof is connected from a center of the outside conductor to the inside conductor and an upper end thereof is connected to the outside conductor; wherein a dielectric partition is formed to have a predetermined height in a direction from the bottom of the I-shaped load to the top thereof.

As the height of the dielectric partition increases, the length of the I-shaped load may decrease.

The dielectric partition may be formed to have a height that can be achieved at a point of saturation at which the length of the I-shaped load does not decrease even when the height of the dielectric partition increases.

A space around the inside conductor may be filled with a first dielectric having a first dielectric constant, and a space between the first dielectric and the I-shaped load may be filled with a second dielectric having a second dielectric constant larger than the first dielectric constant.

The surge protector may further include a frequency characteristic compensation unit, the frequency characteristic compensation unit being formed of a conductor and including a first connection coupled with the outside conductor, and a second connection coupled between the first connection and the I-shaped load and coupled with the I-shaped load so that the coupling depth of the second connection with the I-shaped load can be adjusted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be embodied in many different forms without departing from the spirit and significant characteristics of the invention. Therefore, the embodiments of the present invention are disclosed only for illustrative purposes and should not be construed as limiting the present invention.

These terms are only used to distinguish one element, from another element. For instance, a first element discussed below could be termed a second element without departing from the teachings of the present invention. Similarly, the second element could also be termed the first element.

It will be understood that when an element is referred to as being “coupled” or “connected” to another element, it can be directly coupled or connected to the other element or intervening elements may be present therebetween.

In contrast, it should be understood that when an element is referred to as being “directly coupled” or “directly connected” to another element, there are no intervening elements present.

It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The same reference numerals will be used throughout the different drawings to designate the same or similar components, and the repetition of the same explanation for these components will be skipped.

If in the specification, detailed descriptions of well-known functions or configurations would unnecessarily obscure the gist of the present invention, the detailed descriptions will be omitted.

FIG. 3is a sectional view illustrating the configuration of a surge protector having an improved I-shaped load structure according to a first embodiment of the present invention, andFIG. 4is a graph illustrating the relationship between the height a dielectric and the length of an I-shaped load.

As illustrated inFIG. 3, the surge protector having an improved I-shaped load structure according to the first embodiment includes an outside conductor14provided with input and output terminals on both sides thereof, an input terminal11configured such that a high frequency signal is input from the outside thereto, an output terminal12configured such that a high frequency signal is output therefrom, an inside conductor13disposed inside the outside conductor14to electrically connect the input and output terminals to each other, and an I-shaped load15configured such that the lower end thereof is connected from the center of the outside conductor14to the inside conductor13and the upper end thereof is connected to the outside conductor14.

A space around the inside conductor13is filled with a first dielectric16having a first dielectric constant, and a dielectric partition17filled with a second dielectric is formed around the I-shaped load15above the first dielectric16.

The dielectric partition17is formed to have a predetermined height in a direction from the bottom of the I-shaped load15to the top thereof.

Based on the results of a plurality of experiments, the inventor became aware of the fact that as the height of the dielectric partition17was increased, the effect of extending the I-shaped load15became higher. This means that as the height of the dielectric partition17is increased, the length of the I-shaped load15can be decreased.

That is, for example, if the I-shaped load15is formed to have a length of a ¼ wavelength, it is possible to achieve the effect of a 1 wavelength almost without any insertion loss.

However, as can be seen from the graph ofFIG. 4illustrating the relationship between the height of the dielectric and the length of the I-shaped load, a point of saturation at which the effect of extending the I-shaped load15is not increased even when the height of the dielectric partition17is increased is generated. Accordingly, if the dielectric partition17is formed to have height h corresponding to the point of saturation and the I-shaped load15is formed to have corresponding length L, an optimum effect can be achieved.

The graph ofFIG. 4may vary depending on the dielectric constant of the dielectric partition17. As the dielectric constant of the dielectric partition17increases, the curve of the graph moves further downward.

That is, as the dielectric constant of the dielectric partition17becomes higher, the length L of the I-shaped load15corresponding to the height of the dielectric partition17at a point of saturation becomes shorter. Accordingly, a surge protector having excellent surge frequency blocking performance can be implemented even using a very short I-shaped load15.

As a result of experiments, when the dielectric constants of the first and second dielectrics were set to the same value of 2.2 and the dielectric partition17was formed to a height corresponding to a point of saturation, the effect of a 1 wavelength could be achieved using an I-shaped load15having a length of a ¼ wavelength almost without any insertion loss.

Furthermore, when dielectrics in which the dielectric constant of a second dielectric is higher than the dielectric constant of the first dielectric are used using the characteristics of the graph ofFIG. 4, a surge protector having excellent performance can be implemented even using an I-shaped load15having a very short length.

FIG. 5is a sectional view illustrating the configuration of a surge protector having an improved I-shaped load structure according to a second embodiment of the present invention.

The effect of the extension of an I-shaped load15can be achieved by means of a dielectric partition17as in the first embodiment. However, if the length of the I-shaped load15is reduced even when the dielectric partition17is formed, resonance characteristics are weakened and thus the bandwidth is widened.

Accordingly, the second embodiment is characterized in that a frequency characteristic compensation unit20for compensating for the weakened frequency characteristics is further included.

The frequency characteristic compensation unit20is formed of a conductor. The frequency characteristic compensation unit20includes a first connection21coupled with an outside conductor14, and a second connection22coupled between the first connection21and an I-shaped load15and configured to extend the length of the I-shaped load15.

In the second embodiment, coupling means that are used to be coupled with the first and second connections21and22are formed on an outside conductor14and the I-shaped load15. In the following description, screw coupling means will be illustrated as an example of the coupling means.

The first connection21is configured in the form of a cap having an open bottom. Screw threads21aare formed on the inner circumferential surface of the first connection21, and are engaged with screw threads14athat are formed on the outer circumferential surface of the center protrusion of the outside conductor14.

The second connection22protrudes from the center of the bottom of the first connection21. Screw threads22aare formed on the outer circumferential surface of the second connection22, and are engaged with screw threads15athat are formed on the inner circumferential surface of the I-shaped load15.

Accordingly, the coupling depth of the second connection22and the I-shaped load15varies depending on the direction in which the first connection21is rotated, thereby varying the height of the I-shaped load15. That is, the weakened resonance characteristics can be compensated for by minutely adjusting the coupling depth of the second connection22and the I-shaped load15.

Furthermore, the resonance frequency may be varied through the adjustment of the coupling depth of the frequency characteristic compensation unit20. The surge protector according to the second embodiment is advantageous in that it may be used as a surge protector for a plurality of frequency bands by adjusting the coupling depth of the frequency characteristic compensation unit20in accordance with a desired frequency band.

Although the screw coupling means has been described as coupling depth adjusting means in the above description, it will be apparent that other various types of coupling depth adjusting means may be employed.

The present invention has the advantage of achieving compactness of the surge protector because the surge protector having almost no insertion loss and high surge blocking performance can be implemented using the short-circuit load having a very short length.

Furthermore, the prevent invention has the advantage of compensating for resonance frequency characteristics because the length of the short-circuit load can be minutely adjusted.

Furthermore, the prevent invention has the advantage of being applied to a pulse current injection (PCI) protector that also functions as a surge protector because it can be applied to high frequency signals in various frequency bands through the adjustment of the length of the short-circuit load.