JP2789165B2 - Small antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small antenna used for a portable small radio device and the like, and more particularly to a small antenna used as a case of a radio device.

[0002]

2. Description of the Related Art Conventionally, a loop antenna or a monopole antenna is often used as an antenna used in a portable small radio device or the like, and the used polarization plane is inevitably operated mainly with vertical polarization. A part of the radio wave transmitted from the transmitting station as a vertically polarized wave changes to a horizontally polarized component due to the influence of the surroundings and reaches the receiver, but the vertical polarized component is generally several times larger than the horizontal polarized component. Reach strongly. Depending on whether the antenna polarization plane of the receiver is vertical or horizontal with respect to the incoming radio wave, there is a large difference in communication communication distance.

[0003] As a portable small radio, for example, in a radio paging receiver, a configuration of a small antenna which also serves as a radio case (housing) for miniaturizing the antenna is known. FIG. 5 is a perspective view (A) and a sectional view (B) showing the outline of the configuration example. In FIG. 5, 11 and 12 are rectangular conductor plates, 13 is an insulating frame (frame), and 14 is a short-circuit element. The two conductor plates 11 and 12 are arranged and fixed in parallel with an insulating frame 13 having a thickness h therebetween to accommodate a receiver circuit therein, thereby forming a case. On the other hand, the conductor plate 1
The opposite corners A and A 'of 1 and 12 are set as feeding points, and the other opposite corners B and B' are short-circuited by a short-circuit element 14 to be a short-circuit point. In this way, as shown in FIG. 5B, a planar loop antenna having a U-shaped cross section is formed. The short-circuit element 14 is also provided at the other corners C, C ', D, D', and the short-circuit element 14 having the highest reception sensitivity is selected and short-circuited depending on the attitude of the receiver.

FIG. 6 is a view showing a special case of the sensitivity of a receiver using a planar loop antenna which also serves as a case to the vertical polarization, when the receiver is placed vertically (a) and horizontally (c). The difference in reception sensitivity is remarkably large. The fact that this is due to the directional characteristics of the antenna itself is apparent from the measured data of the directional characteristics of the flat plate loop antenna which also serves as the case of the receiver shown in FIG. Until now,
As a countermeasure, a configuration has been proposed in which the short-circuit position of the two conductor plates constituting the antenna is always changed in the best direction by using the gravity of the earth to keep the sensitivity at an optimum level (Japanese Patent Application No. 63-63). 277328). According to this configuration, a gravitational direction detector and a control circuit are required to change the position of the short-circuit point of the antenna, and there is a problem in maintaining the same miniaturization as in the related art.

[0005]

The above-mentioned radio paging receiver which combines the use of an antenna and a case as described above is constructed so that the reception sensitivity becomes the best when it is placed vertically in a breast pocket, Often used in pockets, bags, handbags, etc. In such a case, the receiver is often laid down as shown in FIGS. 6C and 7C, and the directional characteristics of the antenna are in the worst direction, which impairs the communication notification performance. Therefore, improvement is required. SUMMARY OF THE INVENTION An object of the present invention is to provide a small-sized antenna in which the problem that the difference in the directional characteristics of the gain between the vertical and horizontal installations of the flat loop antenna also serving as the receiver case is remarkably large is improved.

[0006]

A small antenna according to a first aspect of the present invention includes the first to fourth embodiments of the present invention, and has a parallel antenna at an interval sufficiently smaller than a wavelength. A rectangular plate-shaped two conductor plates arranged in the same manner are fixed with an insulating frame to also serve as a case, and one of the two corners of the two conductor plates is short-circuited at a high frequency to form a short-circuit point,
In a small antenna with another corner as a feeding point,
At least one of the two conductor plates is provided with a slit at a right angle from an edge of a side near the short-circuit point. As described above, by providing the slit near the short-circuit point having a high current density, an inductance component is added and the antenna efficiency can be improved.

A small antenna according to a second embodiment of the present invention is directed to the first embodiment, and comprises two rectangular plate-shaped conductor plates arranged in parallel at a sufficiently small interval compared to the wavelength. In a small antenna which is fixed by an insulating frame and also serves as a case, and one of the two conductor plates is short-circuited at a high frequency to a short-circuit point and the other one is a feed point, The corner of the short-circuit point and the corner of the power supply point are located at both ends of one of the long sides of the two conductor plates facing each other, and the corner of one of the conductor plates on the long side is near the short-circuit point. A slit is provided from the edge in parallel with the short side of the conductor plate. As described above, when the short-circuit point and the feeding point are located at both ends of the long side, and the long side is made horizontal and the short side is made vertical by the slit provided from the edge of the long side near the short-circuit point, Is significantly improved.

Further, as described in the third and fourth aspects, the length of the slit is one of the length of the short side of the conductor plate.
/ 2 or more, and the distance of the slit from the corner of the short-circuit point is 1/10 or less of the length of the long side.

A small antenna according to a fifth aspect of the present invention is directed to a second embodiment. One of the conductor plates according to the second aspect is formed of a copper-clad laminate, and the slit is The conductor is formed by etching a conductor of the copper-clad laminate.

A small antenna according to a sixth embodiment of the present invention is directed to a fourth embodiment, in which two rectangular plate-shaped conductors are arranged in parallel at sufficiently small intervals as compared with the wavelength. A small antenna in which the plates are fixed by an insulating frame and also serve as a case, and one of the two corners of the two conductor plates is short-circuited at a high frequency as a short-circuit point, and the other corner is a feeding point. Wherein the corner of the short-circuit point and the corner of the feed point are located at both ends of one of the opposite short sides of the two conductor plates, and the short-circuit point of one of the conductor plates on the short side is A slit is provided from an adjacent edge portion in parallel with a long side of the conductor plate.

[0011]

FIG. 1 is a perspective view showing a first embodiment of the present invention. This small antenna has been verified experimentally during the improvement work of the prior art. FIG. 3 is an exploded perspective view of FIG. 1, and FIG. 4 is an example diagram of measured characteristics of the directivity characteristics of the antenna of the present invention. 1 and 3, reference numerals 1 and 2 denote rectangular conductor plates having a long side length of L and a short side length of W. Reference numeral 3 denotes an insulating frame having a thickness h sufficiently smaller than the wavelength. Reference numeral 4 denotes a slit provided on one conductor plate 1. When the respective parts in FIG. 3 are assembled, as shown in FIG. 1, the conductor plates 1 and 2 are fixed with the insulating frame 3 interposed therebetween at an interval h, thereby forming a case of the receiver. In order to use this case as an antenna, opposing corners A and A ′ of conductor plates 1 and 2 are used.
Is a feeding point, and the other end of the long side of the conductor plate including the feeding points A and A 'is short-circuited by a conductor at the other end, and a portion near the short-circuit point of the conductor plate 1 is parallel to the short side. A slit 4 is provided. FIG. 4 is an example of actual measurement of the directional characteristics of the antenna gain of FIG. Comparing the characteristic example of FIG. 7 of the conventional product of FIG. 5 with the characteristic example of the present invention of FIG.

[0012]

[Table 1]

As is clear from Table 1, the gain difference between the arrangements (a) and (c) was 11.4 dB in the conventional product, but was reduced to 1.6 dB in the product of the present invention. The direction of the maximum value of the directivity characteristic of the product of the present invention is shifted by about 40 degrees as compared with the conventional product, but since the direction of arrival of the radio wave is generally not determined arbitrarily, it is preferable that the gain in all directions is uniformly high. Not a big problem.

The reason why the directivity characteristics when the antenna of the present invention is placed (c) is improved with reproducibility is that the slit 4
Is provided near the short-circuit point between the two conductor plates, it can be considered that the flow of the antenna current flowing through the conductor plates has changed. Therefore, in the present invention, since the gain in all directions is uniformly high, it is not necessary to provide a plurality of short-circuit points and perform a selective operation as in the conventional example. Since the size of the width w of the slit 4 does not affect the directivity, it is preferable that the width w be as small as possible. For example, as shown in FIG. The mechanical strength is maintained by a nameplate such as a decorative seal attached to the upper surface of the case after completion.

The distance d of the slit 4 from the corners of the short-circuit points B and B 'is desirably 1/10 or less of the length L of the long side of the conductor plate 1 including the corners of the feeding points A and A'. When the length s of the slit 4 is set to be at least half the length W of the short side of the conductor plate 1, the gain improving effect is increased. The expression is as follows.

## EQU1 ## (9/10) W ≧ s ≧ (1/2) W

FIG. 2 is a perspective view showing a second embodiment of the present invention. In place of the upper conductor plate 1 provided with the slits 4 of the first embodiment of FIG. This is an example using No. 10. The slits 4 are formed by etching the conductors of the copper clad laminate 10 and are fixed to the insulating frame 3 with the conductor surfaces facing inward. In the figure, the conductor surface faces inward, but may be attached outward.

As shown in Table 1 above, in the comparison between the measured values of the present invention and the measured values of the conventional product, the gain is improved by 0.7 dB in both methods (a) and (b). This is because the inductance (L) component of the plate-shaped loop antenna increases due to the provision of the slit, and the value of the additional capacitance connected between the feeding points AA ′ decreases in order to tune to a predetermined frequency. This is because the loss has been reduced and the efficiency has increased as a whole.

FIG. 8 is a plan view showing a third embodiment of the present invention. In this embodiment, a diagonal C of the feeding points A and A ',
When C ′ is a short-circuit point, slit 4 is connected to short-circuit points C and C ′.
It is provided in a portion close to. As described in the first and second embodiments, the slit 4 has an effect of inserting an inductance component into a portion (short-circuit point) where the current is most concentrated. The efficiency of the antenna can be increased.

FIG. 9 is a plan view showing a fourth embodiment of the present invention. In this embodiment, a portion near the corners D and D 'at the other end of the short side including the feeding points A and A' is a short-circuit point, and a slit 4 is provided near the short-circuit point on the short side. The same effects as those of the third embodiment can be obtained.

[0020]

According to the present invention, the following effects can be obtained. (1) The characteristics at the time of horizontal installation are remarkably improved as compared with the conventional case. (2) The antenna efficiency has been improved overall. This makes it possible to provide an antenna for a wireless device that has high sensitivity regardless of the direction in which the wireless device is placed or the orientation of the wireless device.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the present invention.

FIG. 3 is an assembly explanatory view of the first embodiment of the present invention.

FIG. 4 is a characteristic example diagram of the present invention.

FIG. 5 is a perspective view and a sectional view showing a conventional configuration example.

FIG. 6 is an example of reception sensitivity characteristics of a conventional receiver.

FIG. 7 is a diagram illustrating an example of directivity characteristics of a conventional antenna.

FIG. 8 is a plan view showing a third embodiment of the present invention.

FIG. 9 is a plan view showing a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 2 Conductive plate 3 Insulating frame 4 Slit 10 Copper-clad laminated board 11, 12 Conductive plate 13 Insulating frame 14 Short-circuit element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-125503 (JP, A) JP-A-5-129824 (JP, A) JP-A-2-126702 (JP, A) JP-A-58- 104504 (JP, A) JP-A-1-272303 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01Q 7/00 H01Q 1/24

Claims (6)

(57) [Claims] 1. Two rectangular plate-like conductor plates arranged in parallel at a sufficiently small interval compared to the wavelength are fixed by an insulating frame to serve also as a case, and one of the two conductor plates facing each other is fixed. In a small antenna in which a corner is short-circuited at high frequency to be a short-circuit point and another corner is a feeding point, at least one of the two conductor plates has a short side near the short-circuit point. A small antenna, wherein a slit is provided at a right angle from an edge to the side. 2. Two rectangular plate-shaped conductor plates arranged in parallel at a sufficiently small interval compared to the wavelength are fixed by an insulating frame to serve also as a case, and one of the two conductor plates facing each other is fixed. In a small antenna in which a corner is short-circuited at high frequency to form a short-circuit point and another corner is used as a feed point, the corner of the short-circuit point and the corner of the feed point are formed of the two conductor plates. A small slit which is provided at both ends of one of the opposed long sides and is provided in parallel with a short side of the conductor plate from an edge of the one conductor plate on the long side near the short-circuit point; antenna. 3. The small antenna according to claim 2, wherein the length of the slit according to claim 2 is at least half the length of the short side of the conductor plate. 4. The small antenna according to claim 2, wherein a distance from the corner of the short-circuit point of the slit according to claim 2 is 1/10 or less of a length of the long side. 5. The conductor plate according to claim 2, wherein the one conductor plate is formed of a copper-clad laminate, and the slit is formed by etching a conductor of the copper-clad laminate. Small antenna. 6. Two rectangular plate-shaped conductor plates arranged in parallel at a sufficiently small interval compared to the wavelength are fixed by an insulating frame to serve also as a case, and one of the two conductor plates is opposed to one another. In a small antenna in which a corner is short-circuited at high frequency to form a short-circuit point and another corner is used as a feed point, the corner of the short-circuit point and the corner of the feed point are formed of the two conductor plates. A small slit provided at both ends of one of the opposite short sides, and slits provided from an edge of the one conductive plate on the short side near the short-circuit point and in parallel with the long side of the conductive plate; antenna.