Radio apparatus including no less than two housings

A radio apparatus includes a first housing containing a first printed circuit board, second housing containing a second printed circuit board and being connected so as to be opened and closed to the first housing, an unbalanced-fed type antenna configured to be fed from one of the first printed circuit board and the second printed circuit board, and a magnetic material layer arranged to be located between the first printed circuit board and the second printed circuit board if the second housing is closed to the first housing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-352421 filed on Dec. 27, 2006;

the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radio apparatus, and in particular to a radio apparatus including no less than two housings connected to each other.

2. Description of the Related Art

Portable radio apparatus configured to have no less than two housings which are connected so as to be opened and closed to each other, such as mobile phones, are widely used these days. Such a radio apparatus may be used for voice communication while the housings are opened to each other. The radio apparatus may be used for transmitting and receiving radio waves for data communication, watching television programs and so forth while the housings are closed to each other.

If the housings are closed to each other, an antenna provided in one of the housings and a printed circuit board contained in another one of the housings may be arranged to be close to each other, thus causing impedance of the antenna to be lowered and radiation efficiency of the antenna to be degraded.

Such a problem shall be carefully considered particularly for radio apparatus having a built-in antenna in one of the housings for downsizing, down-weighting and design reasons.

Apart from the above, electromagnetic shielding by using magnetic material has been studied to be applied to radio apparatus like mobile phones so as to suppress unnecessary radiation of radio waves toward human bodies, as disclosed in Japanese Patent Publications of Unexamined Applications (Kokai), No. 2004-304440 and No. 2005-124043.

More specifically, JP 2004-304440 discloses a radio apparatus configured to have a key sheet forming an input device (a key operation portion) and to have radio wave absorbing material formed by a keypad base or keypad buttons for which magnetic material has been mixed. It is mentioned that the above configuration of the radio apparatus may contribute to suppressing radio wave radiation toward human bodies.

Meanwhile, JP 2005-124043 discloses a radio apparatus configured to be provided with a dump sheet containing magnetic material around a display. It is mentioned that the dump sheet containing magnetic material may concentrate magnetic fields of radio frequencies around the display so as to absorb the magnetic fields, thus contributing to suppressing radio wave radiation toward human bodies.

The radio apparatus disclosed in JP 2004-304440 is configured to have the key operation portion near a spot (often called a hotspot) of a housing of the radio apparatus to which radio frequency currents are concentrated so as to control the radio frequency currents.

If the radio apparatus disclosed in JP 2004-304440 is configured to have no less than two housings which are connected so as to be opened and closed to each other, radiation efficiency of an antenna of the radio apparatus may hardly be improved while the two housings are closed depending on a design of the radio apparatus, particularly an arrangement of the key operation portion and a positional relationship with the antenna.

The radio apparatus disclosed in JP 2005-124043 may be considered a same as the radio apparatus disclosed in JP 2004-304440 except that a portion formed by containing magnetic material is arranged not in the key operation portion but around the display.

Thus, if the radio apparatus disclosed in JP 2005-124043 is configured to have no less than two housings which are connected so as to be opened and closed to each other, radiation efficiency of an antenna of the radio apparatus may hardly be improved while the two housings are closed depending on a design of the radio apparatus, particularly an arrangement of the display and a positional relationship with the antenna.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to improve radiation efficiency of a radio apparatus configured to have no less than two housings which are connected so as to be opened and closed to each other while the two housings are closed, independently of an arrangement or a design of each portion of the radio apparatus.

To achieve the above object, according to one aspect of the present invention a radio apparatus includes a first housing containing a first printed circuit board, a second housing containing a second printed circuit board and being connected so as to be opened and closed to the first housing, an unbalanced-fed type antenna configured to be fed from the first printed circuit board or from the second printed circuit board, and a magnetic material layer arranged to be located between the first printed circuit board and the second printed circuit board if the second housing is closed to the first housing.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail. In following descriptions, terms such as upper, lower, left, right, horizontal or vertical used while referring to a drawing shall be interpreted on a page of the drawing unless otherwise noted. Besides, a same reference numeral given in no less than two drawings shall represent a same member or a same portion.

A first embodiment of the present invention will be described with reference toFIGS. 1-5.FIG. 1is an external view of a radio apparatus1of the first embodiment of the present invention to show a configuration and a shape of the radio apparatus1. The radio apparatus1has a first housing11and a second housing12. The first housing11and the second housing12may be folded to each other as indicated by a curved line on a right-hand side ofFIG. 1, and the second housing12is rotatably connected so as to be opened and closed to the first housing11thereby.

The first housing11and the second housing12have a first printed circuit board (PCB)13and a second PCB14, each of which is indicated by a dashed line inFIG. 1, respectively. The first PCB13and the second PCB14are electrically connected by a connection member15, which is shown by hatching surrounded by a dashed outline.

The PCB13includes a feed portion16arranged near an upper short side of the PCB13. The feed portion16is connected to a radio circuit which is not shown but is provided on the first PCB13or on the second PCB14.

The first housing11contains an antenna17arranged near an upper end of the first housing11(indicated by a dashed line inFIG. 1). In spite of the above arrangement, the antenna17may not be placed on an upper side of the radio apparatus1while being used. The antenna17may be, e.g., but not limited to, an inverted-L shaped monopole type antenna as shown inFIG. 1. The antenna17may be of any kind of unbalanced-fed type antennas. The antenna17is connected to the radio circuit which is not shown via the feed portion16.

In addition to the above, the radio apparatus1has a magnetic material layer18formed by containing magnetic material. A shape and an arrangement of the magnetic material layer18will be described with reference toFIG. 2, a perspective view of main portions of the radio apparatus1to show shapes of and positional relationships among the first PCB13, the second PCB14and the magnetic material layer18while the second housing12is closed to the first housing11.

As shown inFIG. 2, the first PCB13, the second PCB14and the magnetic material layer18have almost a same shape and a same size each. If the second housing12is closed to the first housing11, the magnetic material layer18is located between, and almost parallel to, the first PCB13and the second PCB14.

For the above positional relationship shown inFIG. 2, it may be thought that the magnetic material layer18is arranged on a face of the first housing11or of the first PCB13directed to a user during a voice call (called a front face, which is opposite the second housing12or the second PCB14inFIG. 2). It may also be thought that the magnetic material layer18is arranged on a face of the second housing12or of the second PCB14directed to a user during a voice call (called a front face, which is opposite the first housing11or the first PCB13inFIG. 2).

Above difference of the arrangement of the magnetic material layer18may affect radiation efficiency of the antenna17as described with reference toFIGS. 3A-3HandFIGS. 4-5.FIGS. 3A-3Hare side views of plural arrangements of the magnetic material layer18classified depending on whether or not and how the magnetic material layer18is arranged between the first PCB13and the second PCB14. InFIGS. 3A-3H, the antenna17is omitted to be shown. Besides, as the arrangements shown inFIGS. 3A-3Hhave been theoretically given to estimate an influence on the radiation efficiency, practical implementation or feasibility as radio apparatus of some of the arrangements may not have been considered.

FIG. 3A(indicated as “OPEN”) is a side view of one of the arrangements without the magnetic material layer18while the second housing12is opened to the first housing11, as viewed from a direction indicated by a block arrow shown on a right-hand side ofFIG. 2.

FIG. 3B(indicated as “CLOSE”) is a side view of the same arrangement without the magnetic material layer18as shown inFIG. 3Abut while the second housing12is closed to the first housing11as viewed from the direction indicated by the block arrow shown inFIG.2.

FIG. 3C(indicated as “BOTH”) is a side view of another one of the arrangements where the magnetic material layer18is arranged on both of the front faces of the first PCB13and the second PCB14.

FIGS. 3D-3Hshow variations of the arrangement shown inFIG. 3C, where the magnetic material layer18is variably arranged. Reference numerals are common toFIGS. 3C-3H, and thus are omitted to be shown inFIGS. 3D-3H.

FIG. 3D(indicated as “UPPER”) is a side view of an arrangement where the magnetic material layer18is arranged on the front face of the first PCB13. As the first PCB13is located on an upper side inFIG. 2, the arrangement shown inFIG. 3Dis indicated as “UPPER” for convenience.

FIG. 3E(indicated as “LOWER”) is a side view of an arrangement where the magnetic material layer18is arranged on the front face of the second PCB14. As the second PCB14is located on an lower side inFIG. 2, the arrangement shown inFIG. 3Eis indicated as “LOWER” for convenience.

FIG. 3F(indicated as “CENTER”) is a side view of an arrangement where the magnetic material layer18is arranged at a center between the first PCB13and the second PCB14.

FIG. 3G(indicated as “ALL”) is a side view of an arrangement where the magnetic material layer18is arranged to fill up between the first PCB13and the second PCB14.

FIG. 3H(indicated as “OUTER”) is a side view of an arrangement where the magnetic material layer18is arranged both on a face back to the front face of the first PCB13and on a face back to the front face of the second PCB14.

Radiation efficiency of the antenna17has been calculated by simulation for each of the arrangements shown inFIGS. 3A-3H, and influence of the difference of the arrangements has been estimated. It has been assumed for the simulation that a frequency of 620 megahertz (MHz) is given, and that a long side and a short side of the first PCB13or of the second PCB14shown inFIG. 2are 80 millimeters (mm) and 40 mm long, respectively.

It has been assumed for the simulation that the antenna17is a half wavelength long as a whole including a value of loaded inductance, and is quasi-loop like shaped by being arranged parallel to the short side of the first PCB13and folded back. It has been assumed that relative magnetic permeability and dielectric loss tangent of the magnetic material layer18value 40 and 0, respectively.

FIG. 4is a bar chart to show the radiation efficiency estimated by the above simulation for each of the arrangements shown in FIGS.3A-3H.FIG. 4has a horizontal axis corresponding to each of the arrangements shown inFIGS. 3A-3H, and a vertical axis representing radiation efficiency in percent normalized to radiation efficiency of the antenna17assumed to be in free space.

As shown inFIG. 4, the radiation efficiency values around89percent and around 37 percent for the arrangements of “OPEN” and “CLOSE”, respectively. That is, if the second housing12has been opened and then is closed to the first housing11by operation of folding the two housings to each other, e.g., the radiation efficiency is degraded by a ratio of 37 to 89 (around 3.8 decibel (dB)).

Then, the radiation efficiency for the arrangement of “BOTH” values 48 percent. That is, while the second housing12is closed to the first housing11, the radiation efficiency is improved by a ratio of 48 to 37 (around 1.1 dB) by an effect of the magnetic material layer18arranged on the front faces of the first PCB13and the second PCB14each.

As shown inFIG. 4, the radiation efficiency values around 51-53 percent and has no much difference for the arrangements of “UPPER”, “LOWER”, “CENTER” and “ALL”. Among the above, as the arrangement of “ALL” may expect difficulty in implementation or feasibility of a radio apparatus, the arrangements of “UPPER”, “LOWER” and “CENTER” may be left as options.

FIG. 5is a line chart of variation of the radiation efficiency against a separation of the magnetic material18from the second PCB14for the arrangements of “UPPER”, “LOWER” or “CENTER”.FIG. 4has a horizontal axis representing the separation of the magnetic material18from the second PCB14in millimeters (mm), and a vertical axis representing the radiation efficiency in percent normalized to the radiation efficiency of the antenna17assumed to be in free space.

As shown inFIG. 5, the radiation efficiency tends to be higher in a case where the separation of the magnetic material layer18from the second PCB14is no greater than 1 mm than in a case where the above separation is greater than 1 mm. Difference in the radiation efficiency shown inFIG. 5is, however, only 1.8 percent (around 0.15 dB).

From the mentioned above, the arrangement of “UPPER” or “LOWER” where the magnetic material layer18is arranged somewhere between the first PCB13and the second PCB14is suitable in order that the radiation efficiency of the antenna17is improved while the second housing12is closed to the first housing11(it can be said, however, that the arrangement of “CENTER” is less practical than “UPPER” or “LOWER”).

More specifically, it is suitable to arrange the magnetic material layer18on the front face of the second PCB14(corresponding to “LOWER” shown inFIG. 3E) or on the front face of the first PCB13(corresponding to “UPPER” shown inFIG. 3D).

According to the first embodiment of the present invention described above, the radio apparatus including no less than two housings connected so as to be opened and closed to each other may improve antenna's radiation efficiency while the housings are closed by having the magnetic material layer arranged between the PCBs of the housings while the housings are closed.

A second embodiment of the present invention will be described with reference toFIGS. 6A,6B and7. In a same way as the radio apparatus1of the first embodiment, a radio apparatus2of the second embodiment has the first housing11and the second housing12and is configured and shaped as shown inFIG. 1. In addition to the portions shown inFIG. 1, the radio apparatus2has a magnetic material layer28formed by containing magnetic material.

A shape and an arrangement of the magnetic material layer28will be described with reference toFIGS. 6A and 6B.FIG. 6Ais a perspective view of main portions of the radio apparatus2to show shapes of and positional relationships among the first PCB13, the second PCB14and the magnetic material layer28while the second housing12is closed to the first housing11.

FIG. 6Bis a perspective view of the magnetic material layer28extracted as shown by a block arrow inFIG. 6Ato show a shape of the magnetic material layer28.

As shown inFIG. 6B, the magnetic material layer28is shaped to leave a fringe portion shaped almost same as an outline of the first PCB13or of the second PCB14, and to cut off an area inside the fringe portion. That is, the magnetic material layer28is arranged like a picture frame formed by a belt with a width of “d” along a fringe portion of the front face of the first PCB13or along a fringe portion of the front face of the second PCB14.

The magnetic material layer28is frame-shaped with the width of “d” along the fringe portion of the first PCB13or of the second PCB14, so as to be arranged without interrupting arrangement of, e.g., a display, user controls and other circuits in an internal area of the first PCB13or of the second PCB14.

It is expected that the width of “d” of the magnetic material layer28may affect the radiation efficiency of the antenna17while the second housing12is closed to the first housing11. Thus, influence of the width of “d” has been estimated by simulation done in a same way as the simulation of the first embodiment.

A result of the simulation will be explained with reference toFIG. 7, a line chart of variation of the radiation efficiency of the antenna17against values of the width of “d”.FIG. 7has a horizontal axis representing the values of the width of “d” (in mm) and a vertical axis representing the radiation efficiency in percent normalized to the radiation efficiency of the antenna17assumed to be in free space.

Conditions of the simulation (a frequency, sizes of the first PCB13and the second PCB14, a shape of the antenna17, relative magnetic permeability and dielectric loss tangent of the magnetic material layer28) have been assumed to be same as the conditions of the simulation of the first embodiment.

Although being quite low to be 10 percent (−10 dB) for d=1 mm, as shown inFIG. 7, the radiation efficiency is rapidly improved for d≧2 mm and is saturated at 53 percent for d≧8 mm. That is, even if the magnetic material layer28is not arranged on the whole front face of the first PCB13or of the second PCB14, the radiation efficiency may be by no means inferior.

If the radiation efficiency of 45 percent (around −3.5 dB) is given as a reasonable criterion, as shown inFIG. 7, the width of the magnetic material layer28must be d≧3 mm. As the frequency of the simulation has been assumed to be 620 MHz, the width of d=3 mm generally corresponds to around six thousandth wavelength.

A modification of the second embodiment will be explained with reference toFIG. 8. This modification has a magnetic material layer29deformed from the magnetic material layer28of the radio apparatus2.FIG. 8is a perspective view of the magnetic material layer29to show the shape of the magnetic material layer29.

The magnetic material layer29has a portion arranged along the fringe portion of the front face of the first PCB13or of the second PCB14as the magnetic material layer28has, as well as a portion covering an edge face of the first PCB13or of the second PCB14as continued from the front face. In the above description, the edge face is a section of a material base which has been cut to form the first PCB13or the second PCB14, and has a width equal to a thickness of the PCBs.

The magnetic material layer29may be arranged on the front face and on a side face (either inner or outer) of the first housing11, instead of the fringe portion of the front face and the edge face of the first PCB13. The magnetic material layer29may be arranged on the front face and on a side face (either inner or outer) of the second housing12, instead of the fringe portion of the front face and the edge face of the second PCB14.

As shown inFIG. 7, the radiation efficiency has been estimated to be 35 percent for d=2 mm by the simulation on the assumption that the magnetic material layer28is used. Another simulation done in a similar manner but on an assumption that the magnetic material layer29is used instead of the magnetic material layer28has produced a result that the radiation efficiency improves to 47 percent.

Why the radiation efficiency improves will be explained as follows. If the antenna17is excited, radio frequency currents of relatively large values are distributed along the edge faces of the first PCB13or of the second PCB14. Thus, the shape of the magnetic material layer29covering the edge faces may contribute to improving the radiation efficiency.

According to the second embodiment of the present invention described above, an additional effect may be obtained that the magnetic material layer covering only the fringe portion of the PCB may contribute to improving the radiation efficiency.

A third embodiment of the present invention will be described with reference toFIG. 9. In a same way as the radio apparatus1of the first embodiment, a radio apparatus3of the third embodiment has the first housing11and the second housing12and is configured and shaped as shown inFIG. 1. In addition to the portions shown inFIG. 1, the radio apparatus3has a magnetic material layer38formed by containing magnetic material.

A shape and an arrangement of the magnetic material layer38will be described with reference toFIG. 9, a perspective view of a main portion of the radio apparatus3to show shapes of and positional relationships among the first PCB13, the second PCB14and the magnetic material layer38while the second housing12is closed to the first housing11.

As shown inFIG. 9, the magnetic material layer28is shaped to leave an area corresponding to portions along upper and lower short sides of the first PCB13or of the second PCB14. That is, the magnetic material layer28is arranged like a belt with a width of “D” along both the short sides of the front face of the first PCB13or along both the short sides of the front face of the second PCB14.

The magnetic material layer28is shaped like a belt with the width of “D” along both the short sides of the front face of the first PCB13or of the second PCB14, so as to be arranged without interrupting arrangement of, e.g., a display, user controls and other circuits in an internal area of the first PCB13or of the second PCB14.

It is expected that the width of “D” of the magnetic material layer38may affect the radiation efficiency of the antenna17while the second housing12is closed to the first housing11. Thus, influence of the width of “D” has been estimated by simulation done in a same way as the simulation of the first embodiment.

As shown inFIG. 7, the radiation efficiency has been estimated to be 53 percent for d=8 mm by the simulation on the assumption that the magnetic material layer28is used. Another simulation done in a similar manner but on an assumption that the magnetic material layer38is used instead of the magnetic material layer28has produced a result that the radiation efficiency is 52 percent, and there is not much difference with the case where the magnetic material layer28is used.

Why the radiation efficiency does not make much difference will be explained as follows. If the antenna17is excited, radio frequency currents of relatively large values are distributed along the short sides of the first PCB13or of the second PCB14. Thus, the shape of the magnetic material layer38covering the areas along the PCB short sides may contribute to keeping an effect of the improved radiation efficiency.

According to the third embodiment of the present invention described above, another additional effect may be obtained that the magnetic material layer covering only the areas along the PCB short sides may contribute to improving the radiation efficiency.

In the above description of the embodiments, the shapes, the configurations, the sizes, etc. are considered as exemplary only, and thus may be variously modified within the scope of the present invention. For example, connection structure between the two housings forming the radio apparatus is not limited to the foldable type, but may be so called a sliding type or a double swivel type.

If the connection structure is of the sliding type, the first housing11and the second housing12are connected so as to slide against each other. If the connection structure is of the double swivel type, the first housing11and the second housing12are connected so as to rotate around two axes which are perpendicular to each other.

In a case of the double swivel type, the magnetic material layer should be arranged between the first housing11and the second housing12while the housings are closed, based upon consideration that there are plural pairs of faces of the housings which are opposite to each other.

The particular hardware or software implementation of the present invention may be varied while still remaining within the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.