JP4944708B2 - Loop antenna - Google Patents

Description

  The present invention relates to a loop antenna that receives radio waves in, for example, a mobile phone or a small communication device.

  In recent years, mobile phones and small communication terminals (hereinafter referred to as “mobile terminals and the like”) have been downsized, and the mobile terminals have been widely used as highly portable wireless communication devices. Mobile terminals and the like have also been equipped with a function for receiving one-segment broadcasting started in April 2006. Since 1Seg broadcasting is a service using radio waves of 470 to 770 [MHz] in the UHF band, it is necessary to mount an antenna capable of receiving UHF band radio waves on a mobile terminal or the like in order to receive the 1Seg broadcast on a mobile terminal or the like. is there.

  However, the lowest frequency used in one-segment broadcasting is 470 [MHz] and its wavelength is 64 [cm]. Therefore, in order to construct a loop antenna that resonates with radio waves of that frequency, one loop antenna is required. Therefore, a loop antenna obtained by simply winding a conducting wire part once in a loop cannot be built in a portable terminal or the like.

  Therefore, downsizing of an antenna for receiving one-segment broadcasting is required due to size restrictions of portable terminals and the like. In particular, a cellular phone often uses a rectangular loop antenna because its outer shape is rectangular.

  2. Description of the Related Art Conventionally, in order to incorporate a rectangular loop antenna in a portable terminal or the like, a technique has been proposed in which the resonance frequency is lowered by increasing the path length of the conducting wire portion to reduce the size of the loop antenna (for example, Patent Document 1). To 4).

  First, as described in Patent Document 1, as shown in FIG. 13, a card-type wireless receiver case is used as a lower plate (not shown) as an antenna element. The lower plate is made of resin, and a wire is printed or embedded on the lower plate on the case. The shape of the wire is such that the edge of the lower plate is folded over the case and is orthogonal to each other.

  Next, as described in Patent Document 2, as shown in FIG. 14, an antenna element 2 made of a metal foil pattern is formed on a printed circuit board 1, and the antenna element 2 has a required electrical length. Therefore, the shape of the antenna element 2 is a meander shape (continuous folding pattern), one end 3 of the antenna element 2 is connected to an internal receiving circuit as a feeding point, and the other end 4 of the antenna element 2 is open. .

  Next, what is described in Patent Document 3 is provided with a loop antenna element 5 formed in a zigzag shape as shown in FIG. 15, and is intended to reduce the size of the loop antenna.

Next, as described in Patent Document 4, as shown in FIG. 16, first and second loop conductor portions 7 and 8 formed as folded multiple loop conductor portions on a dielectric substrate 6, and a power supply Lines 7a and 7b are provided, so that it is possible to suppress deterioration of the antenna characteristics caused by the radiation of radio waves caused by the currents of the two loop conductor portions 7 and 8 canceling each other.
JP-A-10-56313 JP 2000-216612 A JP 2000-244219 A JP 2004-215061 A

  However, the conventional ones described in Patent Documents 1 to 4 have the following problems when trying to reduce the resonance frequency so that, for example, UHF band radio waves can be received.

  First, what is described in Patent Document 1 is such that the shape of the antenna wire is such that the upper and lower portions of the antenna face each other because the edges of the lower and upper plates of the case are folded back and orthogonal to each other. Therefore, when it is intended to be built in a portable terminal or the like, it is necessary to secure a space in a direction in which the upper and lower portions of the antenna face each other, and there is a problem that it is difficult to reduce the thickness of the portable terminal or the like.

  Next, the problem described in Patent Document 2 is that if the metal foil pattern length is made longer and the resonance frequency is lowered, the whole antenna becomes larger, and it becomes difficult to reduce the size of the portable terminal or the like. was there. Moreover, since the thing described in patent document 2 needed refinement | miniaturization of a metal foil pattern when trying to miniaturize an antenna, there existed a subject that miniaturization of an antenna became difficult.

  Next, what is described in Patent Document 3 is a configuration in which the conducting wire portion is folded not in the circumferential direction of the loop antenna but in a direction perpendicular to the circumferential direction. There is a problem that it is necessary to increase the length and it is difficult to lower the resonance frequency.

  Next, what is described in Patent Document 4 is a configuration in which the loop conductor portions 7 and 8 are folded only once, and it is difficult to further increase the path length of the loop conductor portions 7 and 8, so There was a problem that it was difficult to reduce.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a loop antenna that can be made smaller than the conventional one.

  The loop antenna of the present invention is a loop antenna that is formed in a loop shape and outputs a received radio wave signal to a receiving circuit, the first and second feeding parts connected to the receiving circuit, and the first antenna A linear conductor connecting the power feeding unit and the second power feeding unit along the loop shape, and the linear conductor has a configuration including a folded portion that is folded back in the circumferential direction of the loop shape. is doing.

  With this configuration, the loop antenna according to the present invention can be reduced in length compared to the conventional one because a plurality of linear conductors can be bent back to have a length that resonates with a radio wave having a desired frequency.

  In the loop antenna of the present invention, the loop shape is a rectangular shape, and the linear conductor includes the folded portion on at least one side of the rectangle.

  With this configuration, the loop antenna of the present invention can be made smaller in length than the conventional one in a rectangular shape because the linear conductor can be folded back an arbitrary number of times to resonate with a radio wave of a desired frequency. Can be planned.

  Furthermore, the loop antenna of the present invention has a configuration in which the length of the linear conductor including the folded portion on at least one side of the rectangle is determined based on a desired resonance frequency.

  With this configuration, the loop antenna of the present invention can suitably receive radio waves of a desired frequency by determining the length of the linear conductor on at least one side of the rectangle based on the desired resonance frequency. it can.

  Furthermore, the loop antenna of the present invention has a configuration in which the linear conductor is sandwiched between film-like insulators.

  With this configuration, the loop antenna of the present invention can reduce the size and thickness of the antenna itself, and can maintain its three-dimensional shape. Can be achieved.

  The present invention can provide a loop antenna having an effect that the size can be reduced as compared with the conventional one.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. An example in which the loop antenna of the present invention is applied to an antenna having a rectangular shape and receiving one-segment broadcasting will be described.

  First, the configuration of the loop antenna in this embodiment will be described with reference to FIG. FIG. 1A is a perspective view of a loop antenna in the present embodiment. FIG. 1B is a cross-sectional view taken along line AA in FIG.

  As shown to Fig.1 (a), the loop antenna 100 in this Embodiment is comprised by the rectangular shape, the 1st edge | side 10, the 2nd edge | side 20, the 3rd edge | side 30, and the 4th edge | side 40. In FIG. 1A, each length of the first side 10 and the third side 30 is indicated by W, each length of the second side 20 and the fourth side 40 is indicated by D, and the height of each side is indicated by H. Yes. On the first side 10, power supply units 11 and 12 to which a receiving circuit is connected are formed. The power feeding units 11 and 12 correspond to the first and second power feeding units of the present invention, respectively.

  As shown in FIG. 1B, the loop antenna 100 in this embodiment includes an insulator 101 and a conductor foil 102, and the insulator 101 sandwiches the conductor foil 102. The insulator 101 is made of a film material such as polyimide. The conductor foil 102 is made of, for example, copper foil.

  As shown in FIG. 1A, the conductor foil 102 is connected as a single linear conductor from the power supply unit 11 to the power supply unit 12 while being folded back in the circumferential direction on each side of the rectangle. Hereinafter, a detailed configuration of each side will be described with reference to FIGS.

  First, the configuration of the first side 10 of the loop antenna 100 will be described. 2 shows the configuration of the first side 10, FIG. 2 (a) is a perspective view thereof, FIG. 2 (b) is a diagram showing the pattern shape of the conductor foil 102, and FIG. 2 (c) is the conductor foil 102. It is a figure which shows the direction of the electric current which flows into.

  2B, on the first side 10 of the loop antenna 100, the conductor foil 102 extends in the rectangular circumferential direction (indicated by the arrow of the W dimension) with the power feeding portions 11 and 12, and the power feeding portion. 5 or 5 circumferentially extending portions 10a connected to the left or right, and 4 left and right folded portions that fold the circumferentially extending portion 10a in a direction orthogonal to the circumferential direction (the direction indicated by the arrow H). 10b, an end portion 10c connected to the conductive foil 102 on the second side 20, and an end portion 10d connected to the conductive foil 102 on the fourth side 40. With this configuration, when the loop antenna 100 receives radio waves, if the power supply unit 11 is a positive electrode and the power supply unit 12 is a negative electrode, current flows through the first side 10 as shown in FIG.

  Next, the configuration of the second side 20 of the loop antenna 100 will be described. 3 shows the configuration of the second side 20, FIG. 3 (a) is a perspective view thereof, FIG. 3 (b) is a diagram showing the pattern shape of the conductor foil 102, and FIG. 3 (c) is the conductor foil 102. It is a figure which shows the direction of the electric current which flows into.

  As shown in FIG. 3 (b), on the second side 20 of the loop antenna 100, the conductor foil 102 includes five circumferentially extending portions 20a extending in a rectangular circumferential direction (indicated by an arrow in the D dimension). , Four folded portions 20b that fold the circumferentially extending portion 20a in a direction orthogonal to the circumferential direction, an end portion 20c connected to the conductive foil 102 on the first side 10, and a conductive foil 102 on the third side 30 And an end portion 20d. With this configuration, when the loop antenna 100 receives radio waves, a current flows through the second side 20 as shown in FIG.

  Next, the configuration of the third side 30 of the loop antenna 100 will be described. 4 shows the configuration of the third side 30, FIG. 4 (a) is a perspective view thereof, FIG. 4 (b) is a diagram showing the pattern shape of the conductor foil 102, and FIG. 4 (c) is the conductor foil 102. It is a figure which shows the direction of the electric current which flows into.

  As shown in FIG. 4 (b), on the third side 30 of the loop antenna 100, the conductor foil 102 has five circumferentially extending portions 30a extending in the circumferential direction of the rectangle and in a direction orthogonal to the circumferential direction. Four folded portions 30b that fold the circumferentially extending portion 30a, an end portion 30c connected to the conductive foil 102 on the second side 20, and an end portion 30d connected to the conductive foil 102 on the fourth side 40 are provided. ing. With this configuration, when the loop antenna 100 receives radio waves, a current flows through the third side 30 as shown in FIG.

  Note that the configuration of the fourth side 40 of the loop antenna 100 is the same as the configuration of the second side 20, and thus the description of the configuration is omitted.

  Next, the results of confirming the prototype of the characteristics of the loop antenna 100 according to the present embodiment will be described as first to third examples.

[First embodiment]
FIG. 5 is a perspective view of the loop antenna 100 in the first embodiment. As shown in FIG. 5, in this embodiment, the ratio of the long side to the short side of the rectangle is 2: 1, and D = 80 [mm] and W = 40 [mm]. It is. Therefore, the perimeter in the present embodiment is 24 [cm]. In addition, the dimension H in the height direction is 8 [mm], and this dimension H corresponds to the width of the insulator 101.

  Furthermore, specific dimensions in this embodiment are as follows: the thickness of the insulator 101 = 125 [μm], the width of the conductor foil 102 = 320 [μm], the thickness of the conductor foil 102 = 35 [μm], and the conductor foil 102. Pattern interval = about 2 [mm].

  Next, the VSWR (Voltage Standing Wave Ratio) characteristic and the radiation pattern during resonance in the present embodiment will be described. FIG. 6 is a diagram showing the VSWR characteristics in this embodiment. FIG. 7 is a diagram showing a radiation pattern at the time of resonance in the present embodiment.

  As shown in FIG. 6, the present embodiment has a characteristic that resonates in the vicinity of 470 [MHz], which is the lowest frequency of one-segment broadcasting, and the band where the VSWR characteristic is 3 or less is about 10 [MHz]. .

  Moreover, the thing of a present Example has a characteristic as shown in FIG. 7 as a radiation pattern at the time of resonance. FIG. 7A is a diagram showing a radiation pattern at the time of resonance in the zy plane (φ = 90 °) shown in FIG. FIG. 7B is a diagram showing a radiation pattern at the time of resonance in the xy plane (θ = 90 °) shown in FIG. FIG. 7C is a diagram showing a radiation pattern at the time of resonance in the zx plane (φ = 0 °) shown in FIG.

  As shown in FIG. 7A, the present embodiment has a characteristic indicating omnidirectionality (omnidirectionality) in the zy plane. Further, as shown in FIGS. 7B and 7C, the present embodiment has a characteristic of showing an 8-shaped directivity in the xy plane and the zx plane. That is, the thing of a present Example has the directivity that the electromagnetic wave which advances to the y-axis direction and z-axis direction shown in FIG. 5 can be received stronger than the electromagnetic wave which advances to an x-axis direction.

  The above-described results show that the present example has the same characteristics as those of the one-wavelength loop antenna (the loop length is one wavelength) at the time of resonance. With a one-wavelength loop antenna, if one attempts to receive a 470 MHz radio wave, one wavelength of the 470 MHz radio wave is 64 [cm], so the perimeter must be 64 [cm]. On the other hand, as shown in FIG. 5, the peripheral length of this example is 24 [cm]. Therefore, since the thing of a present Example can be made into about 1/3 with respect to the perimeter of a 1 wavelength loop antenna, it can achieve large size reduction.

[Second Embodiment]
FIG. 8 is a perspective view of the loop antenna 100 according to the second embodiment. As shown in FIG. 8, in this embodiment, the antenna shape is a square shape, and D = W = 60 [mm]. Therefore, the perimeter in the present embodiment is 24 [cm]. The dimension H in the height direction, the thickness and width of the insulator 101, and the thickness and pattern spacing of the conductor foil 102 are the same as in the first embodiment.

  Next, the VSWR characteristics and the radiation pattern at the time of resonance in this embodiment will be described. FIG. 9 is a diagram showing the VSWR characteristics in the present embodiment. FIG. 10 is a diagram showing a radiation pattern during resonance in this example.

  As shown in FIG. 9, the present embodiment has a characteristic of resonating at a frequency in the vicinity of 500 [MHz], and the band where the VSWR characteristic is 3 or less is about 10 [MHz].

  Moreover, the thing of a present Example has a characteristic as shown in FIG. 10 as a radiation pattern at the time of resonance. FIG. 10A is a diagram showing a radiation pattern at the time of resonance in the zy plane (φ = 90 °) shown in FIG. FIG. 10B is a diagram showing a radiation pattern at the time of resonance in the xy plane (θ = 90 °) shown in FIG. FIG. 10C is a diagram showing a radiation pattern at the time of resonance in the zx plane (φ = 0 °) shown in FIG.

  As shown in FIG. 10 (a), the present embodiment has a characteristic indicating omnidirectionality (omnidirectionality) in the zy plane. Further, as shown in FIGS. 10B and 10C, the present embodiment has a characteristic showing the 8-shaped directivity in the xy plane and the zx plane. That is, the thing of a present Example has the directivity that the electromagnetic wave which advances to the y-axis direction and z-axis direction shown in FIG. 8 can be received more strongly than the electromagnetic wave which advances to an x-axis direction.

  The above results show that the present example has the same characteristics as the one-wavelength loop antenna at the time of resonance. With a one-wavelength loop antenna, when trying to receive a 500 [MHz] radio wave, one wavelength of the 500 [MHz] radio wave is 60 [cm], so the perimeter must be 60 [cm]. On the other hand, as shown in FIG. 5, the peripheral length of this example is 24 [cm]. Therefore, since the thing of a present Example can be made into about 1/3 with respect to the perimeter of a 1 wavelength loop antenna, it can achieve large size reduction.

  Further, comparing the characteristics of the present embodiment with those of the first embodiment, the resonance frequency changes by changing the ratio of the side lengths, but the radiation pattern does not change at each resonance frequency. I understand that. This result shows that the present embodiment has the same characteristics as the one-wavelength loop antenna while lowering the resonance frequency so as to correspond to the frequency of the one-segment broadcasting.

[Third embodiment]
FIG. 11A is a perspective view of the loop antenna 100 according to the third embodiment. FIG.11 (b) is a figure which shows the pattern shape of the conductor foil 102 in the 3rd edge | side 50 of a present Example. FIG.11 (c) is a figure which shows the direction of the electric current which flows into the conductor foil 102 in the 3rd edge | side 50 of a present Example.

  As shown in FIG. 11A, in this embodiment, the antenna shape has a rectangular ratio similar to that of the first embodiment (see FIG. 5), and the conductor foil 102 on the third side 50 is formed. The shape is changed to a shape different from that of the first embodiment.

  As shown in FIG. 11 (b), in the third side 50 of the loop antenna 100 in the present embodiment, the conductor foil 102 includes two sets of circumferentially extending portions 50a extending in the circumferential direction of the rectangle, Each of the four folded portions 50b that fold the circumferentially extending portion 50a in the direction orthogonal to the direction, the connecting portion 50c that connects the two sets of circumferentially extending portions 50a in the direction orthogonal to the circumferential direction, and the second side An end portion 50d connected to the 20 conductor foils 102 and an end portion 50e connected to the conductor foils 102 on the fourth side 40 are provided. With this configuration, when the loop antenna 100 receives radio waves, a current flows in the second side 50 as shown in FIG.

  In the present embodiment, the entire length of the conductor foil 102 is made larger than that of the first embodiment (see FIG. 5) by separating the circumferentially extending portion 50a into two left and right sets and providing the connecting portion 50c. Slightly shorter. Therefore, the resonance frequency of the present embodiment is slightly higher than that of the first embodiment.

  Next, the VSWR characteristics in this embodiment will be described in comparison with those in the first embodiment. In FIG. 12, a broken line graph 201 indicates the VSWR characteristics (see FIG. 6) of the first embodiment, and a solid line graph 202 indicates the VSWR characteristics of the present embodiment.

  As described above, in this embodiment, the circumferentially extending portion 50a is divided into two sets on the left and right sides, and the connection portion 50c is provided, so that the total length of the conductive foil 102 is slightly shorter than that in the first embodiment. Therefore, the resonance frequency is about 474 [MHz], which is about 16 [MHz] higher than that of the first embodiment (about 458 [MHz]).

  This result indicates that a desired resonance frequency can be obtained by determining the length of the conductive foil 102 on the third side 50. In the present embodiment, the length of the conductor foil 102 is changed on the third side 50, but is not limited to this, and the length of the conductor foil 102 is changed on a side other than the third side 50. The same effect can be obtained with the configuration.

  Therefore, loop antenna 100 according to the present embodiment determines the length of conductive foil 102 on at least one side of a rectangle based on a desired resonance frequency, thereby receiving radio waves having the resonance frequency with a predetermined VSWR value. be able to.

  As described above, according to the loop antenna 100 in the present embodiment, the conductor foil 102 is folded back in the circumferential direction on at least one side of the rectangle, and the length of the linear conductor can be determined based on a desired resonance frequency. Therefore, the size can be reduced as compared with the conventional one.

  Further, according to the loop antenna 100 in the present embodiment, since the insulator 101 sandwiches the conductor foil 102, the antenna itself can be reduced in size and thickness, and its three-dimensional shape is maintained. Therefore, the mobile terminal or the like can be thinned by being incorporated in the mobile terminal or the like.

  In the above-described embodiment, the shape of the loop antenna 100 is exemplified as a rectangle, but the present invention is not limited to this, and for example, a polygon such as a triangle or a pentagon, a circle, an ellipse, or these The shape etc. which synthesize | combined may be sufficient. For example, in the case of a circular shape, the same effect as described above can be obtained by providing the folded portion every ½ or ¼ of the circumference.

  In the above-described embodiment, the insulator 101 sandwiches the conductor foil 102. However, the present invention is not limited to this. For example, the conductor foil 102 may be formed on one side of polyimide. Good.

  As described above, the loop antenna according to the present invention has an effect that it can be made smaller than the conventional one, and is useful as a loop antenna that receives radio waves in a mobile phone or a small communication device.

The figure which shows the structure in one Embodiment of the loop antenna which concerns on this invention The figure which shows the structure of the 1st edge in one Embodiment of the loop antenna based on this invention. The figure which shows the structure of the 2nd edge in one Embodiment of the loop antenna which concerns on this invention The figure which shows the structure of the 3rd side in one Embodiment of the loop antenna which concerns on this invention The perspective view of the loop antenna in a 1st Example in one Embodiment of the loop antenna which concerns on this invention The figure which shows the VSWR characteristic of the loop antenna in 1st Example in one Embodiment of the loop antenna which concerns on this invention The figure which shows the radiation pattern at the time of the resonance of the loop antenna in 1st Example in one Embodiment of the loop antenna which concerns on this invention The perspective view of the loop antenna in the 2nd example in one embodiment of the loop antenna concerning the present invention The figure which shows the VSWR characteristic of the loop antenna in 2nd Example in one Embodiment of the loop antenna which concerns on this invention The figure which shows the radiation pattern at the time of the resonance of the loop antenna in 2nd Example in one Embodiment of the loop antenna which concerns on this invention Explanatory drawing of the loop antenna in 3rd Example in one Embodiment of the loop antenna which concerns on this invention The figure which shows the VSWR characteristic of the loop antenna in the 1st and 3rd Example in one Embodiment of the loop antenna which concerns on this invention Diagram showing a conventional loop antenna Diagram showing a conventional loop antenna Diagram showing a conventional loop antenna Diagram showing a conventional loop antenna

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st edge | side 10a Circumferential extension part 10b of 1st edge | side 10b Folded part 10c of 10th edge | side 10d of 1st edge | side 11 Feed part (1st feeder part)
12 Power supply unit (second power supply unit)
20 2nd side 20a Circumferential extension part 20b of 2nd side 20b Folding part 20c, 20d End part of 2nd side 30, 50 3rd side 30a, 50a Circumferential extension part 30b of 3rd side, 50b Folded part on the third side 30c, 30d, 50d, 50e End part on the third side 40 Fourth side 50c Connection part 100 Loop antenna 101 Insulator 102 Conductive foil (linear conductor)

Claims (6)

It has four surfaces of the first to fourth surfaces on which the linear conductors constituting one loop antenna are formed, and the x, y, and z coordinates form a three-dimensional orthogonal coordinate system. And the first surface and the third surface extend parallel to each other along the xz plane, and the second surface and the fourth surface face each other along the yz plane. Extending in parallel,
The linear conductor includes a plurality of circumferentially extending portions arranged in the z direction and extending in the x direction on the first surface and the third surface, and extending in the z direction. A plurality of folded portions, and a plurality of circumferentially extending portions extending in the y direction and arranged in the z direction at predetermined intervals on the second surface and the fourth surface, and extending in the z direction. Having a plurality of folded portions,
In the first to fourth surfaces, the folded portion is disposed so as to interconnect ends of two circumferentially extending portions adjacent to each other,
The circumferentially extending portion and the folded portion formed on the first to fourth surfaces are interconnected so as to form a single loop antenna having a pair of feeding points. Loop antenna. 2. The loop antenna according to claim 1, wherein the pair of feeding points are formed on the first surface, a length in a x direction of a circumferentially extending portion of the third surface is W, and the second The loop antenna is characterized in that W <D, where D is the length in the y direction of the circumferentially extending portion of the surface and the fourth surface . 2. The loop antenna according to claim 1, wherein the pair of feeding points are formed on the first surface, a length in a x direction of a circumferentially extending portion of the third surface is W, and the second A loop antenna characterized in that W = D, where D is the length in the y direction of the circumferentially extending portion of the fourth surface and the fourth surface . The loop antenna according to claim 2, wherein the loop antenna has a resonance frequency in a frequency band of one-segment broadcasting . 5. The loop antenna according to claim 1, wherein the loop antenna includes a film-like insulator that forms the first to the fourth surfaces, and constitutes the loop antenna. A loop antenna , wherein the linear conductor is formed as a conductor foil on the film-like insulator . 6. The loop antenna according to claim 5, wherein the loop antenna is mounted on a mobile terminal and receives one-segment broadcasting .

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