Converter for radio wave reception and antenna apparatus

A radio wave reception converter receives a radio wave and converts the radio wave into an electric signal, and includes a horn introducing a radio wave, and a waveguide arranged at the rear of the horn for guiding a radio wave introduced by the horn. An insulation sheet is located between the waveguide and the horn to seal hermetically the interior of the waveguide and the horn. The connecting part between the waveguide and the horn is covered with an exterior cabinet. The front opening of the horn is covered with a feedome. The structure facilitates the connecting work between the waveguide and the horn, and can ensure airtightness at the connecting part.

This nonprovisional application is based on Japanese Patent Application No. 2003-189431 filed with the Japan Patent Office on Jul. 1, 2003, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radio wave reception converter (LNB: Low Noise Block down Converter) receiving radio waves such as those of satellite broadcasting and converting the radio wave into an electric signal, and an antenna apparatus including such a radio wave reception converter.

2. Description of the Background Art

FIG. 7is a sectional view of a structure of a conventional radio wave reception converter.

As shown inFIG. 7, the conventional radio wave reception converter has a horn102secured by a screw109ato a chassis main unit101having a waveguide110. Connection between horn102arid an exterior cabinet105is established by attaching a nut124to the screw portion of an output terminal108provided at chassis main unit101. Accordingly, exterior cabinet105is urged against and secured to horn102: At the front of horn102, a feedome104(also called horn cap) is secured by a screw109b.

An O ring111is located at the connection between horn102and exterior cabinet105. Additionally, an O ring113is located at the connection between exterior cabinet105and output terminal108. These O rings function to establish hermetic sealing of the interior of exterior cabinet105against outside air. Furthermore, an O ring112is located at the connection between feedome104and horn102. This O ring functions to establish hermetic sealing of the interior of horn102and the interior of waveguide110against outside air.

FIG. 8is a sectional view of a structure of another conventional radio wave reception converter.

As shown inFIG. 8, this another conventional radio wave reception converter has a horn202press-fitted and secured at the front end of a waveguide210formed of a cylindrical metal pipe. At the rear of waveguide210, a circuit board207having a converter circuit formed is attached. Waveguide210, horn202and circuit board207are covered with bisected exterior cabinets205a,205band feedome204. Connection of the bisected exterior cabinets205aand205bis established through press-fitting or adhesion-fixing. Additionally, connection between exterior cabinet205aand feedome204is established by press-fitting or adhesion-fixing. Thus, the interior of the radio wave reception converter is maintained in an airtight manner.

The structure of other conventional radio wave reception converters is disclosed in, for example, Japanese Utility Model Laying-Open No. 64-5501, Japanese Utility Model Laying-Open No. 64-15410, Japanese Patent Laying-Open No. 2-75226, Japanese Utility Model Laying-Open No. 62-100710, Japanese Utility Model. Laying-Open No. 4-57927, and the like.

The radio wave reception converter of the structure shown inFIG. 7has the problem that extremely strict accuracy is required in the surface roughness of respective faces of feedome104, horn102, exterior cabinet105and the like brought into contact with O rings111–113as well as the dimension of the groove in which O rings111–113are fitted since airtightness is ensured by O rings111–113. If the accuracy of such elements are not maintained at a high level, moist air will flow into the radio wave reception converter to significantly degrade the product lifetime. It is therefore necessary to realize the high accuracy set forth above, imposing constraints on the fabrication cost.

The radio wave reception converter of the structure shown inFIG. 8is absent of O rings, and maintains airtightness by press-fitting or adhesion-fixing. This imposes the problem that strict dimension accuracy is required. However, exterior cabinets205aand205bas well as feedome204are generally resin-formed components, relatively harder to achieve critical dimension accuracy as compared to metal. Therefore, when the press-fitting process is employed, airtightness of a level that can prevent intrusion of rain can be ensured. However, it is extremely difficult to prevent intrusion of moist air. In the case where adhesion-fixing is employed, the working process becomes tedious since the adhesive must be applied evenly over the entire face of connection. Furthermore, overflow of the adhesion will become the cause of deterioration in appearance.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a radio wave reception converter that has the connecting work between a waveguide and a horn facilitated, and that can ensure airtightness at the connection thereof, and an antenna apparatus including such a radio wave reception converter.

A radio wave reception converter according to an aspect of the present invention receives a radio wave and converts the radio wave into an electric signal. The radio wave reception converter includes a horn for introducing a radio wave, and a waveguide arranged at the rear of the horn for guiding the radio wave introduced by the horn. An insulation sheet is located between the waveguide and the horn. The interior of the waveguide and the interior of the horn are sealed in an airtight manner by the insulation sheet. By the structure of providing and sandwiching the insulation sheet between the waveguide and the horn, the interior of the waveguide can be sealed hermetically against outside air. Since intrusion of moist air can be prevented thereby, the reliability of the apparatus is improved.

In the radio wave reception converter according to the aspect set forth above of the present invention, the connecting part between the horn and the waveguide is covered with a casing, and the opening at the front of the horn is preferably covered with a feedome. Since intrusion of air into the casing and the horn can be prevented by such a structure, the reliability of the apparatus is improved.

In the radio wave reception converter according to the aspect set forth above of the present invention, the inner diameter of the feedome is set smaller than the outer diameter of the horn to press-fit and secure the feedome into the horn. By such a structure, connection between the feedome and the horn is facilitated.

The radio wave reception converter according to the aspect set forth above of the present invention preferably has a structure in which a salient is formed at an end plane of the horn facing the waveguide, a reentrant is formed at an end plane of the waveguide facing the horn to receive the salient, and the circumferential edge of the insulation sheet is sandwiched by the salient and reentrant. In the radio wave reception converter according to the aspect set forth above of the present invention, a structure may be employed in which a salient is formed at an end plane of the waveguide facing the horn, a reentrant is formed at an end plane of the horn facing the waveguide to receive the salient, and the circumferential edge of the insulation sheet is sandwiched by the salient and reentrant. By such a structure, connection between the horn and the waveguide can be facilitated, and airtightness can be ensured by the insulation sheet.

In the radio wave reception converter according to the aspect set forth above of the present invention, preferably a structure is employed in which a horn side flange is provided at the rear end of the horn, and a waveguide side flange is provided at the front end of the waveguide. The horn side flange and the waveguide side flange are fastened by fastening means. By such a structure, the insulation sheet can be sandwiched reliably by the horn and the waveguide through a simple working process.

In the radio wave reception converter according to the aspect of the present invention set forth above, the insulation sheet is preferably a plastic sheet having an adhesive applied on the main surface. Application of an adhesive on the main surface of the insulation sheet allows one of the horn or waveguide to be attached to the insulation sheet, followed by connection between the horn and the waveguide. Therefore, the work is facilitated. The problem of the insulation sheet being shifted in position can also be eliminated. Hermetic sealing can be maintained reliably.

An antenna apparatus according to the present invention includes any of the radio wave reception converter set forth above, and a parabola reflecting and introducing into the radio wave reception converter a radio wave. By such a structure, an antenna apparatus of high reliability can be provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A structure of a radio wave reception converter according to a first embodiment of the present invention will be described hereinafter with reference toFIG. 1.

Referring toFIG. 1, the radio wave reception converter of the present embodiment mainly includes a chassis main unit1, a horn2, an insulation sheet3, a feedome4, and exterior cabinets5aand5b.

Chassis main unit1includes a cylindrical waveguide10for guiding a radio wave, high frequency circuitry7in which is sealed a high frequency circuit substrate (not shown) incorporated with a low noise amplifier and the like, and an F type attachment8that is a connection terminal. Waveguide10is formed of, for example, a metal pipe, or a resin pipe having metal plating on the inner circumferential face. A substrate antenna (not shown) extending from the high frequency circuit substrate is located at the rear of waveguide10to receive a radio wave guided by waveguide10. The received signal is frequency-converted by the high frequency circuit, amplified, and then output to an external source via F type attachment8.

Horn2is the part where a radio wave reflected at the parabola of the antenna apparatus is introduced. The radio wave passing through a front opening21is guided towards the rear. Horn2is a metal shaped piece formed by, for example, press working, or a resin molded piece having metal plating applied on the inner face.

Insulation sheet3is a disk member formed of, for example, PET (polyethylene terephthalate) resin, PP (polypropylene) resin, polyimide resin, Teflon (registered trademark) resin or the like, having its thickness adjusted to several 10 μm. Insulation sheet3is formed in a desired shape by, for example, die-cutting a rectangular sheet. Insulation sheet3preferably has an adhesive (tenacious material) applied on one or both sides of the main surface.

Feedome4is a member attached to horn2so as to occlude front opening21of horn2. Feedome4is a formed piece such as a resin member.

Exterior cabinets5aand5bidentified as the casing are divided into two, covering chassis main unit1. Exterior cabinets5aand5bare formed pieces of resin.

Assembly of respective components are carried out by the procedures set forth below.

First, insulation sheet3is attached at the front end side of waveguide10of chassis main unit1. Horn2is attached to the front end of waveguide10by means of a screw9which is a fastening means. Insulation sheet3is located between the front end plane of waveguide10and the back end plane of horn2.

Then, feedome4is attached to horn2so as to cover front opening21of horn2. Finally, bisected exterior cabinets5aand5bare fitted so as to cover the connecting part between waveguide10of chassis main unit1and horn2. Thus, the radio wave reception converter is assembled.

As shown inFIGS. 2 and 3, the radio wave reception converter of the present embodiment has insulation sheet3located and sandwiched between waveguide10and horn2.

Specifically, a salient24is provided at the end plane of horn2facing waveguide10, and a reentrant14is formed at the end plane of waveguide10facing horn2. Reentrant14of waveguide10receives salient24formed in horn2. Insulation sheet3is located between salient24and reentrant14. The circumferential edge of insulation sheet3is sandwiched between salient24and reentrant14.

A waveguide side flange12is provided at the front end of waveguide10. A horn side flange22provided at the rear end of horn2. A through hole13is formed in waveguide side flange12. A screw hole23is formed at horn side flange22at a position corresponding to through hole13. Screw9is inserted through through hole13. Waveguide10and horn2are secured by screw9fixed in screw hole23. By adjusting insulation sheet3to a predetermined thickness, insulation sheet3is compressed and deformed to be sandwiched between waveguide10and horn2. Therefore, hermetic sealing is ensured at this portion.

At the bottom of reentrant14provided at the end plane of waveguide10, a reentrant15of a size corresponding to the configuration of insulation sheet3is formed. By setting the depth of this reentrant15equal to or slightly smaller than the thickness of insulation sheet3, the gap between waveguide10and horn2can be reduced even if insulation sheet3is made thicker. Therefore, leakage of radio wave can be prevented. Since a thick insulation sheet3can be used by such a structure, hermetic sealing can be achieved more ensurely.

As shown inFIG. 2, feedome4is press-fitted and fixed at the front end of horn2. Specifically, the inner diameter of feedome4is set slightly smaller than the outer diameter of horn2. Press-fit fixation can be established by fitting feedome4to horn2. A claw41is provided at the rear end of feedome4to prevent feedome4from being detached from horn2. Fitting is established to engage claw41with projection28located at a predetermined position at the outer circumferential plane of horn2. This prevents rain from intruding through front opening21of horn2.

By the radio wave reception converter of the above structure, intrusion of rain through the connecting part of bisected exterior cabinets5aand5band the connecting part between horn2and feedome4is prevented. Furthermore, the moist air introduced through the gaps thereof is prevented from flowing into waveguide10by insulation sheet3. Therefore, various electronic components such as the high frequency circuit substrate and the like arranged in high frequency circuitry7is protected from moisture. As a result, a radio wave reception converter of high reliability can be provided.

Since the connection structure set forth above can be realized by the simple working steps of attaching insulation sheet3to the end plane of waveguide10, and fastening waveguide10with horn2by means of screw9, the assembly work will not become tedious. Furthermore, the fabrication cost can be reduced significantly since critical surface roughness or dimension accuracy are not required.

Furthermore, since the connection between bisected exterior cabinets5aand5band the connection between horn2and feedome4are conducted by press-fitting, it is no longer necessary to use an adhesive. The problem of deterioration in the outer appearance caused by overflow of the adhesive can be eliminated.

Complete blocking of the path of waveguide10and the path of horn2by means of insulation sheet3in the radio wave reception converter of the present embodiment allows the interior of waveguide10to be sealed hermetically against outside air. By virtue of insulation sheet3having the thickness of several 10 μm as set forth above, most of the radio waves introduced into horn2will pass through insulation sheet3and reach the interior of waveguide10. There is little, if any, loss in radio wave by such arrangement of an insulation sheet3.

By the structure of dividing the feed horn that guides a radio wave into waveguide10and horn2as in the present embodiment, most of the components of a radio wave reception converter having a different angular aperture depending upon the specification can be used in common. Specifically, a horn2′ having an angular aperture differing from that ofFIG. 2is additionally prepared, as shown inFIG. 4. By setting the configuration of the connecting part between horn2′ and waveguide10identical to that of horn2shown inFIG. 2, the components of chassis main unit1including waveguide10and external cabinets5aand5bcan be used in common. Versatility can be improved. Accordingly, a radio wave reception converter differing in angular aperture can be produced economically.

Second Embodiment

The connection structure of the waveguide and horn of a radio wave reception converter according to a second embodiment of the present invention will be described with reference toFIG. 5. Elements similar to those of the first embodiment have the same reference characters allotted in the drawings, and description thereof will not be repeated.

As shown inFIG. 5, the radio wave reception converter of the present embodiment has insulation sheet3located and sandwiched between waveguide10and horn2.

Specifically, a salient16is formed at the end plane of waveguide10facing horn2, and a reentrant26is formed at the end plane of horn2facing waveguide10. Reentrant26of horn2receives salient16of waveguide10. Insulation sheet3is located between salient16and reentrant26. The circumferential edge of insulation sheet3is sandwiched between salient16and reentrant26.

Waveguide side flange12is provided at the front end of waveguide10. Horn side flange22is provided at the rear end of horn2. Through hole13is formed at waveguide side flange12. Screw hole23is formed at horn side flange22at a position corresponding to through hole13. Screw9is inserted through through hole13. Waveguide10is secured with horn2by screw9being fixed in screw hole23. By adjusting insulation sheet3to a predetermined thickness, insulation sheet3is compressed and deformed by waveguide10and horn2to be sandwiched therebetween. Therefore, hermetic sealing at this region can be ensured.

A reentrant27of a size corresponding to the configuration of insulation sheet3is formed at the bottom of reentrant26provided at the end plane of horn2. By setting the depth of reentrant27equal to or slightly smaller than the thickness of insulation sheet3, the gap between waveguide10and horn2can be reduced even if insulation sheet3is made thicker. Therefore, radio wave leakage can be prevented. Since a thick insulation sheet3can be used by such a structure, hermetic sealing can be achieved more ensurely.

The structure set forth above has an advantage similar to that of the first embodiment.

Third Embodiment

A structure of an antenna apparatus according to a third embodiment of the present invention will be described with reference toFIG. 6.

Referring toFIG. 6, the antenna apparatus of the present embodiment includes a radio wave reception converter50and a parabola52. Radio wave reception converter50corresponds to the radio wave reception converter of the first or second embodiment set forth above.

The radio wave from a satellite is reflected and concentrated by parabola52to be introduced into the horn of radio wave reception converter50arranged in front of parabola52. The radio wave from a satellite is a circularly polarized wave, including a right-handed polarized wave and a left-handed polarized wave. Radio wave reception converter50separates these two components, amplifies respective components, and converts the radio wave in a band of ten several GHz to a signal of the frequency band of 1 GHz. The converted signal passes through a cable connected to the F type attachment of radio wave reception converter50and an indoor receiver (for example, a satellite receiver) to be send to a television.

By the above-described structure, an antenna apparatus maintaining high reliability can be provided.