GB2435549A

GB2435549A - Liquid antenna including a feed connector with leak prevention

Info

Publication number: GB2435549A
Application number: GB0700692A
Authority: GB
Inventors: Gi Tae Do; Hyun Hak Kim; Jae Chan Lee
Original assignee: Samsung Electro Mechanics Co Ltd
Current assignee: Samsung Electro Mechanics Co Ltd
Priority date: 2006-02-28
Filing date: 2007-01-15
Publication date: 2007-08-29
Anticipated expiration: 2027-01-15
Also published as: FI20075046A0; GB2435549B; GB0700692D0; FI20075046A; KR100735355B1; DE102007002023A1

Abstract

A liquid antenna comprises solid 120 and polar liquid 124 radiators housed in a body 110 with a mechanical and electrical connector 130 to a feed cable 150. The feed cable 150 provides an inner core conductor 152 which connects to a solid radiator 120 via abutting contact members 154, 122 and an outer conductor 158 which is connected to a liquid radiator 124. The connector 130 also includes liquid leakage prevention means 170 located between the antenna body 110 and the feeding cable 150. The connector 130 may comprise a conductive body 132 which connects to the outer conductor 158 of the feed cable 150 and has an integral ground pillar 140 extending into the antenna body 110 to contact the polar liquid radiator 124. The connector 130 and feed cable 150 may have corresponding female and male threads for engaging with one another. A solder joint may be formed between the body of the connector and the outer conductor of the feed cable. The feed cable may have insulating material 156 between the inner and outer conductive members 152, 158. The connector 130 is securely attached to the antenna body 110 by inserting a pin 146 into a pin hole 136 and a pin groove 114. The antenna may provide a compact antenna which is adjustable to operate in a broadband and/or low frequency band with a uniform gain.

Description

LIQUID ANTENNA HAVING LEMCAGE PREVENTION STRUCTURE

CLAIM OF PRIORITY

(â0O1] This application claims the benefit of Korean Patent Application No. 2006-19632 filed on February 28, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

HACKGROUND OF THE INVENTION

Field of the Invention

[0002] The present invention relates to a liquid antenna, more particularly, which has a leak-proof structure capable of preventing a liquid radiator from leaking, while providing a ground.

Description of the Related Art

(0003] In general, an antenna uses as a radiator a conductor which resonates at a predetermined frequency bandwidth. For example, a chip antenna has a conductor patterned uniformly on a dielectric or magnetic body.

(0004] Such an antenna has a unique resonant frequency determined by a conductor structure and/or a dielectric constant of the dielectric body. Accordingly, with the conductor or dielectric material determined to specific properties, the resonant frequency cannot be adjusted until the conductor boy is geometrically changed.

[0005] Notably, a recent mobile communication terminal needs a compact chip antenna in which a resonant frequency can be adjusted to a low band. Lately, attempts have been made to fabricate a compact antenna of a low bandwidth with specific magnetic materials. However, a conventional chip antenna hardly secures a sufficient resonant length due to its spatial limitation in the terminal.

(0006] The conventional antenna, which usually covers merely a narrow bandwidth, preferably needs to cover a wide bandwidth despite a slight decline in gain. Ideally, the antenna would be most advantageous if it covers all bandwidths with uniform gain. But this is hardly achievable from the conventional antenna that adopts a conductive radiator.

(0007] The conventional antenna like the chip antenna described above employs a conductive radiator of a specific structure. This renders the resonant frequency of the antenna hardly adjustable, for example, in a wide band and/or to a low band.

(0008] To overcome the problem, a novel concept of a liquid antenna using a polar liquid as a radiator is being developed.

In order to variously design antenna characteristics in the liquid antenna, liquids of various compositions are employed, concentration and types of electrolytes are adjusted and contents and types of a conductive powder are regulated. This allows the resonant frequency to be easily adjusted, for example, in a wide band and/or to a low band.

[0009] Yet, the liquid antenna utilizes liquid as a radiator, thereby critically necessitating a hermetical sealing structure for preventing leakage of the liquid. Also, the liquid, which functions as a radiator, should be preferably grounded.

STJMHARY OF THE INVENTION

[00101 The present invention has been made to solve the foregoing problems of the prior art and therefore an aspect of the present invention is to provide a liquid antenna of a leak-proof structure for preventing leakage of a polar liquid constituting a liquid radiator.

[0011] Another aspect of the invention is to provide a liquid antenna which has a ground path formed in a liquid radiator to improve resonance characteristics.

[002.2] According to an aspect of the invention, the invention provides a liquid antenna. The liquid antenna includes an antenna body having solid and liquid radiators housed therein, and having a feeding part connected to the solid radiator and exposed at one end thereof; a feeding cable having one end disposed in abutment with the one end of the antenna body, the feeding cable including a conductive core electrically connected to the feeding part of the solid radiator and an outer conductor electrically connected to the liquid radiator; a connector for keeping the feeding cable in abutment with the antenna body and electrically connecting the liquid radiator of the antenna body with the outer conductor of the feeding cable; and a leakage prevention member provided between one end edge portion of the feeding cable and the one end of the antenna body to prevent leakage of the liquid radiator.

[0013] The connector includes a connector body made of a conductor, and having a lower part attached around the outer conductor of the feeding cable; and a ground pillar formed integral with the connector body and extending into the antenna body to contact the liquid radiator.

[0014) The connector body has a female thread formed in an inner lower part thereof and the feeding cable has a male thread formed around the outer conductor thereof to mesh with the female thread.

(0015] The ground pillar of the connector, the connector body and the outer conductor of the feeding cable cooperate together to form a ground path.

(0016] The connector body has a female thread formed in an inner lower part thereof, and the liquid antenna further comprises a conductive fastener formed around the outer conductor of the feeding cable, the conductive fastener having a male thread configured to mesh with the female thread. Here, the ground pillar of the connector, the connector body, the fastener and the outer conductor of the feeding cable cooperate together to form a ground path.

[0017] The connector is configured to accommodate the one end of the antenna body, and the antenna body further comprises a pin extending through the connector and fixed to the one end of the antenna body.

(0018] The connector has a tubular structure so as to accommodate the one end of the antenna body, and the liquid antenna further comprises a second leakage prevention member disposed between an inner wall of the connector and one end edge portion of the antenna body.

(0019j The feeding part of the antenna body has a width greater than that of the solid radiator, and the feeding cable further comprises a joint formed at the one end thereof to abut on the feeding part at a width greater than that of the conductive core so that the conductive core is electrically connected to the feeding part.

[0020] Also, the liquid antenna further includes a solder joint disposed on a portion connecting a lower end of the connector with the outer conductor of the feeding cable.

BRIEF DESCRIPTION OF TBE DRAWINGS

(00211 The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: (0022] FIG. 3. is a schematic perspective view illustrating a liquid antenna according to an embodiment of the invention; (0023] FIG. 2 is a schematic perspective view illustrating a liquid antenna according to another embodiment of the invention; (0024] FIG. 3 is a schematic perspective view illustrating a helical liquid antenna with a helical radiator according to the invention; [0025] FIG. 4 is a schematic perspective view illustrating a chip liquid antenna employing a resonance frequency adjuster; (0026] FIG. 5 is a partially broken front view illustrating a liquid antenna according to the invention; (0027] FIG. 6 is an enlarged cross-sectional view illustrating an A portion of FIG. 5; (0028] FIG. 6 is an enlarged cross-sectional view illustrating an A portion of FIG. 5; (0029] FIG. 7 is an exploded view of FIG. 6; (0030] FIG. 8 is a plan view illustrating a connector of FIG. 7; (0031] FIG. 9 is an exploded view of FIG. 6; [0032] FIG. lOis a modified view illustrating a liquid antenna according to the invention, corresponding to a configuration in which a container and a connector are attached; 10033] FIG. 11 is a modified view illustrating the connector of FIG. 7; and (0034] FIG. 12 is a graph illustrating effects of adjusting a resonance frequency of a liquid antenna according to the invention.

DETAILED DESCRIPTION OP THE PREPERBED EMBODI)NT

(0035) Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0036] FIG. 1 is a schematic perspective view illustrating a liquid antenna according to the invention.

(0037] Referring to FIG. 1, the antenna 10 includes a polar liquid 15, a liquid container 11 for housing the polar liquid therein, and a feeding part 17 extending through one end of the container 1]. into the polar liquid 15.

[0038] The polar liquid 15 of the invention is employed as a novel radiator. The polar liquid 15 exhibits uniform conductivity through ionic combination or molecular combination and also high dielectric constant. This as a result obtains various current distributions. Therefore, the polar liquid 15 functions as a radiator having a resonance frequency specified by a current fed through the feeding part 17. For example, water as the polar liquid 15 is known to demonstrate a dielectric constant of about 80 and a conductivity of about 3 S/rn. As just described, the polar liquid 15 differs from typical dielectrics and metal conductor materials in terms of electromagnetic characteristics. This enables the resonance frequency of the antenna to be adjusted in a wide band and/or to a low band, which however cannot be expected from the typical antennas.

(0039] Presumably, the polar liquid is conducive to adjusting the resonant frequency of the antenna for following reasons.

(0040] First, the polar liquid, if exposed to a wave of a specific frequency, is altered in its polarity to resonate, as exemplified by functions of a microwave oven. That is, for the microwave oven, an ultra-short wave is applied to food and fluid of food (chiefly water) resonates to heat food. Here, the resonating polar Liquid may interfere with the wave traveling therethrough.

(0041] Second, the polar liquid, if exposed to a wave, forms a closed path of current, thereby interfering with the wave.

[0042] Third, generally, the polar liquid such as water extends the wavelength of a wave, thereby causing loss tothewave. This change in wavelength of the wave also may bring about the above effects.

(0043] Examples of the polar liquid 15 include water, SAR solution, electrolytic fluid, synthetic liquid and etc. Especially, the polar liquid 15 dissolves a different electrolyte and alters conductivity through dissociated ions, thereby ensuring low band or wide band performance which cannot

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be expected from the conventional antenna. Alternatively, in place of electrolyte, magnetically attractable conductive powder, e.g., metal powder such as iron may be mixed into the liquid to achieve similar effects: (0044] This liquid antenna can be designed to demonstrate broad antenna characteristics by varying composition of the liquid, concentration and type of the electrolyte and content and type of the conductive powder. This is disclosed in I(orean Patent Application No. 10-2005-0062352 (entitled "Antenna Using L.iguid Radiator," assigned to the applicant of this application), entire contents of which are incorporated herein by reference.

(0045] FIG. 2 is a schematic perspective view illustrating a liquid antenna 20 according to another embodiment of the invention.

(0046] FIG. 2 depicts a rnonopol antenna 20 having an'L' -shaped radiator 25. The radiator 25 has one end connected to an external circuit to act as a feeding part 25a. The radiator of the monopol antenna 20 is disposed inside a liquid container 27, which is filled with a polar liquid 29.

(0047] Moreover, examples of the polar liquid 29 applicable to the invention include but not limited to water, alcohol and SAR. The polar liquid 29 exhibits uniform conductivity and high dielectric constant through ionic combination or molecular combination, thereby ensuring diversity in current

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distribution that affects antenna characteristics. This adjusts a unique resonance frequency of the radiator 25. In general, the polar liquid is higher in dielectric constant and lower in conductivity than typical dielectric materials or conductive materials such as metal. As a result, the polar liquid ensures the resonance frequency to be adjusted in a wide band contrary to the dielectric materials or metal.

10048] In the conventional monopol antenna, the resonance frequency is adjusted by lengthening or geometrically changing the conductive radiator 25. Yet, the polar liquid 29 allows the resonance frequency to be adjusted in a wide band and modified as desired.

[0049] In this configuration, a major portion of the radiator is accommodated in the liquid container 27 so that an overall radiation area is electromagnetically influenced by the polar liquid 29. However, it is structurally fulfilling if the polar liquid 29 housed in the liquid container 27 electromagnetically affects only at least a portion of the radiator 25. Thus, alternatively, Only a portion of the radiator is disposed inside the liquid container or the liquid container is located in the vicinity of the radiator.

(0050] Here, in order to effect a change in additional electromagnetic properties, an electrolytic or conductive powder may be added to the polar liquid 29 which is employed to adjust the resonance frequency. Typically, the conductive powder or electrolyte added tends to raise conductivity, thereby further adjusting the resonance frequency.

Accordingly, the electrolyte and/or conductive powder added to the polar liquid 29 are varied in concentration (content) and composition thereof to adjust the resonance frequency variously.

The electrolyte is exemplified by NaC1, and other various electrolytes may be adopted. The conductive powder utilizes magnetically attractable metal such as iron (Fe) and nickel (Ni).

(0053.] In this fashion, the polar liquid allows the resonance frequency of the antenna to be adjusted in a wide band and/or to a low/high band depending on the antenna structure. For example, the L'-shaped monopol wire antenna of FIG. 2 tends to have a resonance frequency adjusted to a low band while a helical antenna of FIG. 3 tends to have a resonance frequency adjusted to a high band.

[0052] FIG. 3 depicts a helical antenna 30 having a helical radiator 35. The radiator 35 has one end connected to an external circuit to act as a feeding part 35a. Similarly to FIG. 2, the radiator of the helical antenna 30 is disposed inside a liquid container 37, which is filled with a polar liquid 39.

Examples of the polar liquid 39 include but not limited to water, alcohol and SAR. The polar liquid 39 serves as a novel current distribution source to adjust a unique resonance frequency of the radiator 35.

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(0053] As stated above, the helical antenna 30 has the resonance frequency adjusted according to a gap between loops of the helical radiator. These structural characteristics allow the polar liquid 39 to exert an electromagnetic influence between the loops, thereby adjusting the resonance frequency in a wide band and/or to a high band.

(0054] The antenna assembly utilizing this resonance frequency adjuster is applicable to a chip antenna. FIG. 4 illustrates a chip antenna where a resonance frequency adjusting mechanism is applied according to another embodiment of the invention.

The chip antenna 40 of a Planar Inverted F Antenna (PIFA) structure is formed on a ground plate 44.

(0055] Referring to FIG. 4, the chip antenna 40 is connected to a feeding part 42 and provided with a radiation electrode 45 having a short-circuit part 43 at one end thereof. The short-circuit part 43 may be of a PIFA structure connected to the ground plate 44. In this structure, the liquid container 47 is filled with the polar liquid 49 and substitutable for a conventional dielectric block. That is, a conductor pattern including the radiation electrode 45 is formed on a surface of the liquid container 47.

(0056] As described above, the polar liquid 49 exhibits uniform conductivity and high dielectric constant through ionic combination or molecular combination. This changes current distribution of the radiation electrode 45, thereby adjusting a unique resonance frequency by virtue of the radiation electrode 45.

[0057] As described above, in the chip antenna, the dielectric block itself can be substituted by the liquid container 47 filled with the polar liquid 49. Alternatively, with the dielectric block employed, the liquid container 47 can be positioned in the vicinity of the radiation electrode 45 to adjust the resonance frequency as desired.

(0058) The resonance frequency can be tuned through configurations shown in FIGs. 2 to 4. Details thereof are disclosed in Korean Patent Application No. 10-2005-0070730 (entitled "Broad Antenna Using Liquid Medium," assigned to the applicant of this application), entire contents of which are incorporated herein by reference.

(0059] A liquid antenna will be explained hereunder with reference to FIGs. 5 to 9 according to a preferred embodiment of the invention. In the drawings, FIG. 5 is a partially broken front view illustrating the liquid antenna according to the invention. FIG. 6 is an enlarged cross-sectional view illustrating an A portion of FIG. 5. FIG. 7 is an exploded view of FIG. 6. FIG. B is a plan view illustrating a connector of FIG. 7. FIG. 9 is a partial exploded view of FIG. 6.

[0060] As shown in FIGs. 5 to 9, the liquid antenna 100 of the invention includes an antenna body 110, a connector 130 and an RF cable 150.

(0061] The antenna body 110 is an insulating container having a polar liquid 124 housed therein. The antenna body 110 is constructed of a tubular side wall 112, an upper end and a lower end 116:. Here, a helical radiator 120 is disposed inside the container 112 through an opening in the lower end 116. A lower end of the radiator 120 extends through the lower end 116 of the antenna body to connect to a feeding part 122 attached underneath the lower end 116 of the antenna body 110. The lower end of the radiator 120 is preferably fitted to the opening of the lower end 116 of the antenna body so that the polar liquid 124 inside the antenna body 110 is not leaked through a gap between the radiator 120 and the lower end 116 of the antenna body 110. Meanwhile, a pin groove 114 is formed in the vicinity of the lower end 116 of the side wall 112 to accommodate a pin 146, which will be stated later.

[0062] Here, as described above, to distinguish the polar liquid 124, which acts as a radiator, from the radiator 120, the former may be termed a liquid radiator while the latter may be termed a solid radiator.

[0063] The connector 130 is made of a conductor, and hasa lower part of the antenna body 110 and an upper end of the RF cable housed therein to be connected each other.

(0064] Specifically, the connector 130 is configured as a tubular body 132 having an inner space 144 opened vertically.

Moreover, a groove 138 is formed between an outer wall 134 of

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the upper end of the antenna body 132 and a ground pillar 140 to accommodate a lower part of the side wall 122 of the antenna body 110 and the lower end 116 of the antenna body is inserted into the ground pillar 140. The ground pillar 140, as shown in FIG. 8, is extended as a pair of opposing circular arcs.

Therefore, the lower part of the antenna body 110 is attached to the connector 130 such that the ground pillar 140 is protruded into the container 112 through the opening 118 formed in the lower end 116 of the container. Furthermore, the pin 146 is engagingly inserted into a pin hole 136 of the connector 130 and the pin groove 114 of the container 112, thereby ensuring connector 130 and the container 112 to be more solidly attached.

Meanwhile, female threads 142 are formed in a lower part of the inner space 144 to mesh with male threads 162 of a fastener 160 disposed in an upper part of an RF cable 150, which will be stated later.

[0065] The RF cable 150 is structured such that an inner conductor, i.e., a conductive core is surrounded by an insulator 156, which is then surrounded by an outer conductor 150. A conductive feeding contact part 154 is formed in an upper end of the RF cable 150 to connect to the underlying conductive core 152. Also, the conductive fastener 160 is disposed around an upper end portion of the outer conductor 150. The male threads 162 are formed in the outer periphery of the fastener 160. The male threads 162 of the fastener 160 mesh with the female threads 15' 142 of the connector 130 to engage the RF cable 150 with the connector 130. Accordingly, the contact part 154 of the RF cable 150 abuts the feeding part 122 of the antenna 120 to be electrically connected each other, thereby allowing the antenna 120 to be powered by the RF cable 150. Moreover, the fastener is made of a conductor to be electrically connected to the connector body 132.

(00663 Through this structure shown in FIGS. 5 and 6, the ground pillar 140, the connector body 132, the fastener 160 and the outer conductor 158 are sequentially electrically connected to thereby form a ground path through which overvoltage arising inside the antenna 110 is extracted out.

[0067] Meanwhile, a packing 170 is installed around the contact part 154. The packing 170, preferably, is made of a non-transparent material having elasticity such as rubber.

The packing 170 blocks the polar liquid 124 from leaking over the antenna 120 and the feeding part 122 when the RF cable 150 is engaged with the connector 130.

[0068] As described above, when the antenna body 110, the connector 130 and the RF cable 150 are engaged with one another, a solder joint is disposed on a portion connecting a lower end of the connector 130 and the RF cable 150 to ensure the connector andthe RFcable 150 tobemore solidly attached. The solder joint 180 also serves to block any polar liquid 124 that may leak through the packing.

(0069] The liquid antenna 100 as just described is free from a leakage problem in utilizing the polar liquid 124 as a frequency adjuster. Furthermore, the liquid antenna 100 is provided with a ground path through which overvoltage can be extracted out, thereby enhancing stability.

(0070] FIG. lOis a modified view illustrating a liquid antenna of the invention, corresponding to a configuration view of FIG. 9 in which the container and the connector are attached.

(0071] The antenna of FIG. 10 is identically configured to the liquid antenna 100 of FIGs. 5 to 9 except that a second packing 172 is disposed around a lower end portion of the antenna body 112. Therefore, like parts will be represented by like reference numerals and will be explained in no more detail.

0072) As described above, a groove is formed inside the outer wall 134 of the connector 130 and a second packing 172 made of a non-transparent and elastic material is installed therein.

This prevents the polar liquid 124 from leaking toward an upper end of the outer wall 134 through a gap between the ground pillar inserted into the opening 118 formed in the lower end 116 of the antenna body and the lower end of the antenna body 16.

(0073] FIG. 1]. is a modified view illustrating a connector of FIG. 7.

(0074] A connector 130a of FIG. 1]. is structured the same as the connector 130 of FIG. 7 except that a ground pillar 138a is altered in its configuration. Therefore, like parts are represented by the like reference numerals and will be explained in no more detail.

(0075] While the ground pillar 138 shown in FIG. 7 is extended vertically in a circular. arc and the ground pillar 138a shown in FIG. 11 is extended vertically into the shape of a pin. This further reduces a gap between the ground pillar 138 and the lower end 116 of the antenna body, thereby more advantageously preventing leakage of the polar liquid 124.

(0076] FIG. 12 is a graph illustrating effects of adjusting JO a resonance frequency of a liquid antenna according to the invention.

(0077] Referringto FIG. 12, Voltage Standing Wave Ratio (VSWR) or Standing Wave Ratio (SWR) (A) of the conventional liquid antenna is compared with that (B) of the liquid antenna of the invention. Here, the liquid antenna of the invention is found tobe increased in bandwidth and output. Therefore, the liquid antenna grounded according to the invention. is advantageous in terms of leak prevention and grounding, and also characteristic of wide bandwidth and high output.

(0078] As set forth above, according to exemplary embodiments of the invention, a liquid antenna has a leak-proof structure for preventing leakage of a polar liquid constituting a liquid radiator. Also, the liquid antenna of the invention provides a ground path to the liquid radiator to enhance radiation properties.

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(0079] For example, an explanation is given chiefly based on a helical liquid antenna structure shown in FIG. 3 but the invention is applicable to various structures of liquid antennas shown in FIGs. 1, 2 and 4.

(0080] While the present invention has been shown and described in connection with the preferred embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

What Is Claimed Is: 1. A liquid antenna comprising: an antenna body

having solid and liquid radiators housed therein, and having a feeding part connected to the solid radiator and exposed at one end thereof; a feeding cable having one end disposed in abutment with the one end of the antenna body, the feeding cable including a conductive core electrically connected to the feeding part of the solid radiator and an outer conductor electrically connected to the liquid radiator; a connector for keeping the feeding cable in abutment with the antenna body and electrically connecting the liquid radiator of the antenna body with the outer conductor of the feeding cable; and a leakage prevention member provided between one end edge portion of the feeding cable and the one end of the antenna body to prevent leakage of the liquid radiator.

2. The liquid antenna according to claim 1, wherein the connector comprises: a connector body made of a conductor, and having a lower part attached around the outer conductor of the feeding cable; and a ground pillar formed integral with the connector body and extending into the antenna body to contact the liquid radiator.

3. The liquid antenna according to claim 2, wherein the connector body has a female thread formed in an inner lower part thereof and the feeding cable has a male thread formed around the outer conductor thereof to mesh with the.female thread.

4. The liquid antenna according to claim 1, wherein the ground pillar of the connector, the connector body and the outer conductor of the feeding cable cooperate together to form a ground path.

5. The liquid antenna according to claim 1, wherein the connector body has a female thread formed in an inner lower part thereof, and the liquid antenna further comprises a conductive fastener formed around the outer conductor of the feeding cable, the conductive fastener having a male thread configured to mesh with the female thread.

6. The liquid antenna according to claim 5, wherein the ground pillar of the connector, the connector body, the fastener and the outer conductor of the feeding cable cooperate together to form a ground path.

7. The liquid antenna according to claim 1, wherein the

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connector is configured to accommodate the one end of the antenna body, and the antenna body further comprises a pin extending through the connector and fixed to the one end of the antenna body.

8. The liquid antenna according to claim 1, wherein the connector has a tubular structure so as to accommodate the one end of the antenna body, and the liquid antenna further comprises a second leakage prevention member disposed between an inner wall of the connector and one end edge portion of the antenna body.

9. The liquid antenna according to claim 1, wherein the feeding part of the antenna body has a width greater than that of the solid radiator, and the feeding cable further comprises a joint formed at the one end thereof to abut on the feeding part at a width greater than that of the conductive core so that the conductive core is electrically connected to the feeding part.

10. The liquid antenna according to claim 1, further comprising: a solder joint disposed on a portion connecting a lower end of the connector with the outer conductor of the feeding cable.