JP2011049936A - Antenna, and antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna and an antenna device having proper communication performance, capable of saving a space. <P>SOLUTION: The antenna device includes a base body 3, a coil 30 formed of a conductor 4 wound on the base body 3, and a plurality of terminals 5 connected to the conductor 4. An exposed base body section 31, where the conductor does not exist, is formed on the base body 3, except for a winding start part and a winding end part of the coil 30. It is characterized in that a terminal 5 is arranged at the side of a surface parallel to the coil axis of the coil 30 and arranged at the side of the exposed base body section 31. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an RF-ID, that is, a wireless communication medium processing device that performs communication with a wireless communication medium such as an IC card or an IC tag, or an antenna and an antenna device that are used for the wireless communication medium itself.

  In recent years, mobile terminals such as mobile phones with built-in RF-ID wireless tags and non-contact type IC cards and IC tag reading functions have become widespread. Many antenna devices are used in which body sheets are bonded together (the coil axis of the loop antenna is perpendicular to the magnetic sheet).

JP 2009-182902 A

  In order to attach a conventional antenna, it is necessary to secure an attachment place having almost the same area as the antenna inside the portable terminal, which has been a factor that hinders the reduction in size and thickness of the portable terminal.

  In view of the above problems, an object of the present invention is to provide an antenna and an antenna device that can save space and have good communication performance.

  The present invention includes a base body, a coil portion formed by a conductor wound around the base body, and a plurality of terminals connected to the conductor. The base body includes a conductor except for the start and end of winding of the coil portion. The antenna is characterized in that a base exposed portion, which is a portion where no is present, is formed, the terminal is disposed on the surface side parallel to the coil axis of the coil portion, and is disposed on the base exposed portion side.

  ADVANTAGE OF THE INVENTION According to this invention, space saving is possible and the antenna and antenna apparatus which have favorable communication performance can be provided.

The perspective view of the antenna of the Example of this invention The top view of the antenna of the Example of this invention Plan view of another antenna according to an embodiment of the present invention 1 is a block diagram of a first antenna device using an antenna according to an embodiment of the present invention. The block diagram of the antenna apparatus using another antenna of the Example of this invention The block diagram of the 2nd antenna apparatus using the antenna of the Example of this invention The block diagram of the 3rd antenna apparatus using the antenna of the Example of this invention Conceptual diagram of the present invention Plan view of antenna when implemented with normal chip component structure Explanatory drawing of Experiment 1 Explanatory drawing of Experiment 2 and Experiment 3 Explanatory drawing of Experiment 4 Explanatory drawing of Experiment 5 Explanatory drawing of Experiment 6 Explanatory drawing of Experiment 7 Result graph of Experiments 1-7 The perspective view of the antenna of the Example of this invention Configuration diagram of the winding number experiment Result graph of winding number experiment The exploded perspective view of the portable terminal using the antenna of the example of the present invention FIG. 20 is a perspective view of the back side of the substrate. Circuit diagram of antenna circuit of the present invention The exploded perspective view of the portable terminal using the antenna of the example of the present invention The top view of another antenna of the Example of this invention

  According to the first aspect of the present invention, the substrate includes a base, a coil portion formed by a conductor wound around the base, and a plurality of terminals connected to the conductor. Except for the start and end of winding, a base exposed portion, which is a portion where no conductor exists, is formed, the terminal is arranged on the surface side parallel to the coil axis of the coil portion, and is on the base exposed portion side By using the antenna, it is possible to efficiently use the metal body inside the portable terminal equipped with this antenna as an antenna, so that it is possible to make an antenna having a large opening area with a small antenna. Therefore, space can be saved and an antenna having good communication performance can be provided.

  According to the invention described in claim 2 of the present invention, the number of turns of the coil portion of the antenna is approximately half a turn larger than an integer multiple, so that the antenna is mounted by using the antenna according to claim 1. It is preferable because the current flowing on the metal body can be used efficiently.

  According to the invention described in claim 3 of the present invention, the base exposed portion is formed at both ends of the base, and the magnetic field passing through the inside of the coil portion is obtained by the antenna according to claim 1. Current can be efficiently induced because it can be made parallel to the coil axis.

  According to the invention described in claim 4 of the present invention, the plurality of terminals connected to the coil part are on the same base body exposed part side, whereby the antenna has the metal body. It is possible to obtain a state with the best communication performance when mounted on the.

  According to the invention described in claim 5 of the present invention, at least one base bare portion in the antenna according to any one of claims 1 to 4 is more than the outer periphery of the metal body on which the antenna is mounted. By using the antenna device that is mounted so as to be located on the outside, the current flowing on the metal body can be efficiently used, and an antenna device having good communication performance can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view of an antenna according to an embodiment of the present invention.

  The antenna 1 is configured as follows. The conductor 4 is wound around the base 3 to form a coil portion 30, the coil portion 30 is covered with the protective material 2, and the terminal 5 to which the conductor 4 is connected and the vibration resistance not connected to the conductor 4. And a fixing terminal 6 for the purpose of improving the mounting strength.

  The terminal 5 is provided on the surface side parallel to the coil axis A of the coil portion 30 and on the base exposed portion 31 side where the coil portion 30 does not exist.

  The arrangement of the terminals 5 will be described in detail. In this embodiment, the coil portion 30 is provided on the surface side parallel to the coil axis A, and is viewed from a direction B perpendicular to the surface on which the terminals 5 are provided. At least a part of the input / output terminal 5 is located within the surface of the base body exposed portion 31, that is, when viewed from the direction B, at least a part of the terminal 5 overlaps the surface of the base body exposed portion 31. It is configured.

  The terminal 5 is on the surface side parallel to the coil axis A and in the vicinity of the base body exposed portion 31, that is, around the coil portion 30 or around the base body exposed portion 31 excluding the surface perpendicular to the coil axis A. What is necessary is just to arrange | position and when it sees from the direction B like a present Example, at least one part of the terminal 5 does not need to overlap the surface of the base | substrate exposed part 31. FIG.

  Here, it is preferable that a magnetic material such as ferrite is used for the base 3, whereby the magnetic flux passing through the coil portion 30 is increased and communication performance can be improved. However, the base 3 is not limited to a magnetic material, and may be made of, for example, ceramic or resin.

  The conductor 4 is preferably a wire such as a coated copper wire, a tape such as a thin copper foil, or a ribbon-like metal, but the metal is attached to the surface of the magnetic core 3 by plating or vapor deposition, A method may be used in which only the necessary part is left and the coil part 30 is formed.

  The terminal 5 is preferably formed by punching or bending a copper or iron alloy or the like, and the surface is preferably plated with a metal such as tin so that soldering can be easily performed.

  The fixing terminal 6 is also configured in the same manner as the input / output terminal 5, but it may not be provided depending on the size of the antenna 1 and the usage situation, and any number may be provided.

  Further, the protective material 2 uses a mold such as an epoxy resin, a tape, a paint, or the like, and has the purpose of preventing the conductor 4 from being disconnected, the base 3 from being damaged, and forming an adsorption portion for an automatic mounting machine. Can be made. In addition, it is preferable that an input / output pin mark or a product number is printed on the protective material 2 on the top surface of the antenna 1 in order to prevent mounting errors. In the present embodiment, the protective material 2 is used, but the protective material 2 may not be provided.

  In FIG. 1, the coil unit 30 is wound about 7.5 turns. However, since the coil unit 30 is about half a turn larger than an integral multiple, input / output terminals are arranged on both sides of the coil unit 30. This is preferable because the terminals 5 are arranged at both ends of the antenna 1 when a plurality of antennas are connected or when connecting to be inserted into a part of the loop-shaped conductor.

  Moreover, in FIG. 1, since the terminal 5 when connecting to the substrate is on the lower side and the number of turns of the conductor 4 is 7.5 turns, the number of the conductors 4 wound on the base 3 is higher than the lower surface. It is increasing.

  This is because when the antenna 1 is mounted on a metal body, the conductor 4 on the lower surface is close to the metal body, so that it is easy to receive a magnetic field in a direction that cancels a signal from the eddy current of the metal body, and the conductor 4 on the upper surface is difficult to receive. For this reason, the characteristics of the coil portion 30 are improved when the number of the conductors 4 on the upper surface that is not easily affected by the eddy current is larger.

  FIG. 2 is a plan view of the antenna according to the embodiment of the present invention.

  It is a feature of the present invention that the terminal 5 connected to the conductor 4 is located beside the base exposed portion 31. In the antenna shown in FIG. 2, the fixing terminal 6 is provided beside the other base bare portion 31 like the terminal 5. However, the position of the fixing terminal 6 is not particularly limited.

  In addition, the base | substrate exposed part 31 in FIG. 1 points out the part in which the conductor 4 does not exist on the base | substrate 3, instead of the coil part 30 wound by the conductor 4 closely.

  Further, in the present embodiment, the base body exposed portions 31 are provided at both ends of the base body 3. By doing so, for example, when a magnetic field comes from the outside, the magnetic field passing through the inside of the coil portion 30 is made close to the coil axis. Therefore, it is preferable because the current induced in the coil portion 30 increases. In addition, although the two terminals 5 are configured to exist in the plane of the same base body exposed portion 31, the arrangement with the best performance can be obtained when the antenna 1 is mounted on a metal body. Moreover, although the overall shape is substantially square, the shape is not limited to this.

  FIG. 3 is a plan view of another antenna according to the embodiment of the present invention.

  The difference from the antenna of FIG. Terminals 5 are arranged diagonally. When this antenna 1 is mounted on a metal body, although the performance is slightly inferior to that of the antenna shown in FIG. 1, it is not a great influence. Therefore, the terminal arrangement as in this embodiment can be selected according to the situation in which this antenna is used.

  FIG. 24 is a plan view of still another antenna according to the embodiment of the present invention.

  In FIG. 24, the winding start and the winding end of the conductor 4 are slanted, and the conductor 4 is present in the base uncovered portion 31. The definition of the base unexposed portion 31 in the present invention is as follows: The antenna shown in FIG. 24 is also included in the scope of the present invention because the conductor 4 except for the winding end is not provided. The start and end of winding are considered to be approximately 0.5 turns.

  In the antenna of the present invention, when the antenna is disposed on the metal body, by providing the base body exposed portion, the base body exposed portion is disposed inside the metal body and the case where the antenna body is disposed at the end of the metal body. It has the effect of.

  When a magnetic body is used as the base, if the base exposed portion is placed inside the metal body, the magnetic field inside the coil approaches parallel to the coil axis, compared to when there is no base exposed portion, so that transmission and reception can be performed efficiently. And the efficiency of the antenna can be improved.

  Further, in the case where the base exposed portion is disposed outside the metal body, and an antenna having terminals connected to both ends of the base exposed portion is used, an efficient antenna can be obtained with a minimum number of coil turns. it can.

  When the coil part is wound to the end of the base body without providing the base bare part as in the past, the coil part located outside the metal body cannot supplement the magnetic field due to the current on the metal body, contributing to the characteristics. Not efficient. If the base does not protrude from the metal body and the coil is wound to the end of the base, the magnetic field inside the coil near the end will not be parallel to the coil axis even if the base is a magnetic body. The antenna characteristics deteriorate.

  For this reason, in this embodiment, in order to improve the characteristics of the antenna, the base exposed portions are provided at both ends of the antenna.

  FIG. 4 is a configuration diagram of a first antenna device using the antenna according to the embodiment of the present invention. The structure at the time of mounting the antenna 1 of FIG. 2 on the board | substrate 7 is represented. Since the end portion of the substrate 7 is shown in an enlarged view, the left and right and lower directions of the substrate 7 are not shown.

  On the outer periphery of the conductor pattern 8 constituting the ground, there is provided a ground extraction portion 11 without a conductor, and an input / output terminal land 9 is provided so that the base exposed portion 31 and the terminal 5 of the antenna 1 are located there. .

  Here, the length of the base exposed portion and the length of the ground removal portion 11 in the coil axis direction are substantially the same.

  The conductor pattern 8 is provided with a fixed terminal land 10 for fixing the fixing terminal 6, and the fixed terminal land is electrically connected to the conductor pattern 8.

  The ground removal portion 11 preferably has no ground electrode on the inner layer of the substrate in terms of performance. However, when the substrate 7 is thick, the ground removal portion 11 may be provided only in the layer near the antenna 1.

  Moreover, a glass epoxy base material etc. are normally used for the board | substrate 7, and although copper is often used as the conductor pattern 8, it is not restricted to this but can be used. The surface is usually coated with solder resist or silk. Although the conductor pattern 8 is assumed to be the ground here, a pattern floating from the ground may be used. At this time, the conductor pattern should have a large area. For example, when a magnetic field is applied from the outside, the eddy current generated in the conductor pattern is large, and as a result, the communication performance is improved.

  Although FIG. 4 shows an example in which the antenna 1 is mounted on the substrate 7, the mounting location is not limited to the substrate, and for example, the antenna 1 may be mounted on a metal body such as a battery or a frame of a liquid crystal panel. With the configuration as shown in FIG. 4, the portion with the highest density of current generated on the conductor pattern 8 can be used in the coil portion 30, and therefore the performance of the antenna 1 can be best.

  FIG. 5 is a configuration diagram of an antenna device using another antenna according to the embodiment of the present invention. The structure at the time of mounting the antenna of FIG. 3 on the board | substrate 7 is represented. On the outer periphery of the conductor pattern 8 constituting the ground, a ground-extracted portion 11 without a conductor is provided, and for the input / output terminal such that the base body exposed portion 31 of the antenna 1, the terminal 5 and the fixing terminal 6 are located there. Lands 9 and fixed terminal lands 10 are provided. The other input / output terminal land 9 and fixed terminal land 10 are provided in the conductor pattern 8. With this configuration, although the portion having the highest density of current generated on the conductor pattern 8 can be used in the coil unit 30 although it is slightly inferior to the configuration of FIG. 4, good communication performance can be obtained. .

  FIG. 6 is a configuration diagram of a second antenna device using the antenna of the embodiment of the present invention. Although the arrangement configuration is the same as in FIG. 4, the shapes of the ground removal portion 11, the input / output terminal land 9, and the fixed terminal land 10 are different. It is preferable to round the edge portion of the pattern as shown in FIG. 6 because current flowing along the vicinity of the outer periphery of the conductor pattern 8 can be prevented from being concentrated and lost to the edge portion. The terminal arrangement is illustrated in the state of the antenna of FIG. 2, but is not limited thereto.

  FIG. 7 is a configuration diagram of a third antenna device using the antenna of the embodiment of the present invention. The difference from FIGS. 4 to 6 is that the ground exposed portion 11 is not provided under the base exposed portion 31 but the base exposed portion 31 is arranged outside the outer periphery of the conductor pattern 8. The land 9 has just been formed. Even in this way, a portion with the highest density of the current generated on the conductor pattern 8 can be used in the coil portion 30, so that good communication performance can be obtained. Although the terminal arrangement is illustrated in the state of the antenna of FIG. 2, the present invention is not limited to this, and the antenna arrangement of FIG.

  4 to 7, the signal line to the input / output terminal land 9 is not shown, but it is preferable to use a wiring that passes through the inner layer or the back surface of the substrate 7 because the current flowing on the conductor pattern 8 is not hindered. Further, the fixed terminal land 10 may or may not be connected to the conductor pattern 8.

  When the antenna 1 is mounted on a metal body that is not a substrate, it may be difficult to mount by reflow. In that case, the antenna 1 can be fixed at a predetermined position with a double-sided tape or the like, and power can be supplied to the terminal 5 by contact with a pin or soldering of a conductive wire. An antenna device having good communication performance can be obtained.

  Next, the concept that the antenna 1 of the present invention functions as an antenna in the vertical direction of the surface of the surface-mounted metal body by surface mounting will be described.

  FIG. 8 is a conceptual diagram of the present invention. The state in which the antenna 1 of the present invention is attached to the substrate 7 so that the base exposed portion is disposed outside the outer periphery 12 of the conductor pattern is illustrated.

  First, a case where a signal is input to the antenna 1 will be described. When a signal is input to the antenna 1, a current flows through the coil portion of the antenna 1, and a magnetic field is generated in the coil axis direction of the coil portion by the current. In other words, since it is orthogonal to the magnetic field in the direction perpendicular to the substrate 7 as it is, it does not operate as an antenna. Due to this magnetic field, a current 14 is generated on the substrate 7 that generates a magnetic field 13 in a direction that cancels the magnetic field of the antenna 1. The current 14 flows along the outer periphery 12 of the conductor pattern, and the current density is highest at the outer periphery and decreases as it goes inward. Since the current 14 along the outer periphery 12 of the conductor pattern forms a large loop path, a magnetic field in a direction perpendicular to the main surface of the substrate 7 is generated. Therefore, it can be seen that the antenna 1 is an antenna having good performance in the direction perpendicular to the main surface of the substrate 7.

  Next, a case where a magnetic field perpendicular to the substrate 7 is applied from the outside will be described with reference to FIG. When an external magnetic field in a direction perpendicular to the main surface of the substrate 7 is applied, a current (eddy current) 14 that generates a magnetic field in a direction that cancels the external magnetic field is generated on the substrate 7. A current is induced in the antenna 1 by a magnetic field 13 generated by the current 14, and is output as a signal. Therefore, it can be seen that the antenna 1 is an antenna having good performance against an external magnetic field in a direction perpendicular to the main surface of the substrate 7.

  From this, it can be said that the antenna 1 becomes an antenna having good communication performance by being mounted on a metal body. Although FIG. 8 illustrates the case where the antenna 1 is mounted on the substrate 7, the component on which the antenna 1 is mounted is not limited to the substrate, and may be a metal body such as a battery, a frame of a liquid crystal panel, or a metal housing.

  Here, the arrow indicating the direction in FIG. 8 is used to express an image of a certain moment. Actually, a magnetic field or a signal vibrates at a certain frequency, and the direction is reversed at another moment. .

  However, FIG. 8 is not provided with a land or a fixed land for inputting / outputting signals to / from the antenna 1 on the substrate 7 for the purpose of explaining the concept. In this state, there is no structure that obstructs the current flowing on the surface of the substrate 7, but the antenna device 1 and other components must be connected by aerial wiring or the like, which is preferable because it prevents miniaturization of the entire device. In addition, when automatic mounting is considered, it is actually necessary to provide a land, and it is necessary to consider a land layout having a structure that does not disturb the current on the substrate 7 as much as possible.

  For this reason, in this embodiment, the land layout was examined under the following conditions.

  Here, the antenna used in the experiment uses 5 mm × 5 mm × 0.4 mm rectangular ferrite as the substrate 3, and the conductor 4 uses a coated copper wire having a diameter of 0.26 mm, and is wound for 7.5 turns. An antenna was used. At this time, the length of the coil part 30 was set to 3 mm, and the base bare part 31 of 1 mm was provided on both sides thereof.

  First, as an ordinary conceivable structure, an antenna as shown in the plan view of the antenna in the case of carrying out with the ordinary chip part structure of FIG. 9 is assumed and used as a comparative example of this embodiment. In order to give priority to antenna sensitivity, assuming that no terminal is provided in the coil opening direction of the antenna, the input / output terminal 105 has a width close to the width of the chip as shown in FIG. This structure is provided with a terminal. Since there are only two terminals in total for input and output, two terminals are sufficient, and considering the mountability and soldering strength, the larger terminal width is better.

  FIG. 10 shows a state where the antenna 101 is mounted on the substrate 7. Since the input / output terminal 105 is provided, a ground extraction portion 115 for the input / output terminal 105 is formed on the outer periphery 12 of the conductor pattern.

  Therefore, even if the substrate 7 receives a magnetic field from the outside and a current is generated on the substrate 7, the current 14 on the substrate 7 is hindered by the ground removal portion 115 and greatly meanders. It is speculated that it is not preferable.

  That is, when the conductor pattern is formed as shown in FIG. 10 and the antenna is arranged, the current flowing in the direction perpendicular to the coil axis of the antenna is small and the antenna cannot efficiently receive the current flowing on the substrate 7. Will get worse.

  This state was set as Experiment 1, and the size of the ground removal portion 115 was 4 mm in the vertical direction and 2 mm in width. In the state shown in FIG. 10, 50Ω was matched at 13.56 MHz, a 20 dBm sine wave signal was input from the signal generator to the antenna at 13.56 MHz, and the magnetic field strength at 30 mm above the main surface of the substrate 7 was measured. The magnetic field intensity in this state was set to 100%, and the following experiments 2 to 7 were compared.

  FIG. 11 is an explanatory diagram of Experiment 2 and Experiment 3. For the purpose of preventing large meandering of the current 14 seen in the explanatory diagram of Experiment 1 in FIG. 10, the portion C was configured so as not to interrupt the conductor pattern outer periphery 12. Here, C part is a part of the conductor pattern having a width from the outer periphery 12 of the conductor pattern to the ground extraction part 15 for arranging the land for the input / output terminals, and the width of the C part inward from the outer periphery of the conductor pattern is C. To do. D is a distance from the outer periphery 12 of the conductor pattern to the inner edge of the substrate of the grounding portion 15 for arranging the input / output terminal land. D was fixed at 4 mm, C = 1 mm in Experiment 2, C = 3 mm in Experiment 3, and the same measurement as in Experiment 1. As a result, Experiment 2 was 124% compared to Experiment 1 and Experiment 3 was 131% compared to Experiment 1. became. It can be seen that the larger C, the better the characteristics.

  FIG. 12 is an explanatory diagram of Experiment 4. For the purpose of further increasing the portion C in FIG. 11, the non-coiled portion of the antenna is no longer protruded from the outer periphery 12 of the conductor pattern, and a ground removal portion 11 is provided instead. Is. By doing so, it could be increased to C = 4 mm. At this time, D = 5 mm. The size of the ground removal part 11 was 5 mm in width and 1 mm in the vertical direction, and the same measurement as in Experiment 1 was performed. As a result, it was 124% as compared with Experiment 1. It can be inferred from Experiment 3 that the vertical edge of the ground removal portion is close to the coil portion, and the current 14 is partially parallel to the coil axis.

  FIG. 13 is an explanatory diagram of Experiment 5. In response to the result of Experiment 4, the edge of the ground removal portion 11 was cut at 45 ° in order to keep it away from the coil portion. As a result, the path of the current 14 can be made substantially perpendicular to the coil axis, and it can be assumed that the characteristics are restored. As a result of measuring in the same manner as in Experiment 1, it was improved to 134% compared with Experiment 1.

  FIG. 14 is an explanatory diagram of Experiment 6. In order to further improve the state of Experiment 5, it is necessary to eliminate the grounding portion 15 for disposing the input / output terminal land 9 that hinders the current 14 from being on the path of the current 14. Accordingly, the ground extraction portion 11 is enlarged, and only one of the input / output terminals on the path of the current 14 is moved into the ground extraction portion 11, and one input / output terminal land 9 is provided in the ground extraction portion 11. At this time, the width of the ground removal portion was 9 mm, and the vertical direction was 1 mm as it was, and the same measurement as in Experiment 1 was performed. As a result, 138% was further improved compared to Experiment 1.

  FIG. 15 is an explanatory diagram of Experiment 7. In Experiment 6, it was effective to move the placement ground removal portion 15 of the input / output terminal land 9 into the ground removal portion 11, and therefore the remaining placement ground removal portion 15 of the other input / output terminal land 9. Also moved into the ground removal portion 11, and a total of two input / output terminal lands 9 were provided in the ground removal portion 11. At this time, the size of the ground removal portion 11 was 11 mm in width and 1 mm in the vertical direction, and the same measurement as in Experiment 1 was performed.

  The magnetic field strength with no land on the substrate 7 as shown in FIG. 8 can be measured as 134% by connecting the antenna terminal directly to the matching circuit and measuring.

  FIG. 16 is a graph of the results of Experiments 1-7. The broken line at 134% represents the magnetic field strength in an ideal state (FIG. 8) where there is no land on the substrate 7. From this result, it can be seen that all the measures are effective for the antenna of the comparative example of FIG. 9 and the communication characteristics are good.

  Further, in Experiment 5 (FIG. 13), Experiment 6 (FIG. 14), and Experiment 7 (FIG. 15), the communication characteristics are better than the ideal configuration of FIG. I understand.

  It can be presumed that by providing the ground extraction portion 11 on the outer periphery 12 of the conductor pattern, the current 14 is bent along the ground extraction portion 11 and the density is increased under the antenna 1, particularly under the coil portion 30. . Accordingly, it can be said that it is very effective to provide the ground extraction portion 11 and to dispose the exposed base portion of the antenna 1 there, and the present invention is effective for providing an antenna and an antenna device having good communication performance. It can be seen that it is.

  For comparison, a similar experiment was performed using a sheet-like loop antenna having a conventional structure. A ferrite sheet having a sheet size of 25 mm × 15 mm and a thickness of 0.4 mm is attached to the place of the antenna 1 in FIG. 8, and is wound in a flat form for 3 turns with an outer diameter of 24 mm × 14 mm with a coated copper wire having a diameter of 0.26 mm. The antenna was pasted on it. The magnetic field strength of this conventional antenna was 137%. Therefore, in this experiment, with the antenna of the present invention, a magnetic field strength equal to or greater than 7% of the conventional antenna area (calculated by the ferrite area) was obtained. That is, it can be said that the present invention can provide an antenna that can greatly contribute to space saving.

  Next, an experiment performed on the number of windings will be described.

  FIG. 19 shows a graph of the results of the winding number experiment. The horizontal axis plotted the number of windings, and the vertical axis plotted the values normalized by the magnetic field strength at 0.5 windings. The antenna used in the experiment has a shape as shown in the perspective view of the antenna in FIG. 17, ferrite of 21 mm × 4 mm × 0.2 mm is used for the base 3, and a copper thin plate with a thickness of 0.1 mm is matched to the number of turns. The width was varied from 1 mm to 0.6 mm. As shown in the configuration diagram of the winding number experiment in FIG. 18, the antenna 1 was placed close to the end portion of the substrate 7, and the base exposed portion was positioned outside the conductor pattern 8. A land is not formed on the substrate 7 but is directly connected to the terminal 5 and matched to 50Ω at 13.56 MHz. A sine wave signal of 20 dBm is input from the signal generator to the antenna at 13.56 MHz. The magnetic field strength at 30 mm above the surface was measured. As shown in FIG. 19, the magnetic field strength increases as the number of turns increases. However, considering the rate of increase, it can be seen that when the number of windings increases from an integer by a half turn, it greatly increases. The conductor on the side not facing the metal body 6 is less affected by the eddy current on the surface of the metal body 6, but the conductor of the coil portion 2 on the side facing the metal body 6 is canceled by the eddy current on the surface of the metal body 6. Therefore, it can be estimated that the increase in the magnetic field strength is small when the number of windings is an integral multiple. This is effective in designing the antenna more efficiently with less material.

  Hereinafter, a case where the antenna is mounted on a portable terminal will be described.

  20 is an exploded perspective view of a portable terminal using the antenna of the embodiment of the present invention, and FIG. 21 is a perspective view of the back surface of the substrate of FIG. The portable terminal 16 includes a liquid crystal panel 17, a button 18, a casing 21, a casing 22, a substrate 19 included therein, a battery 20, and the like, and the antenna 1 is attached to the substrate 19. The antenna 1 is mounted on the surface of the substrate 19 on the side opposite to the direction in which the liquid crystal panel 17 is present, and the ground removal portion 11 is formed on the substrate 19. Although not shown, it is assumed that components such as ICs, RF modules, other frequency antennas, speakers, and camera units are mounted on the substrate 19.

  FIG. 21 is a diagram in which the substrate 19 is turned upside down, but two antennas 1 are mounted on the substrate 19. Arranging a plurality of them in this way is preferable because the current flowing on the substrate surface can be used more efficiently than when using only one. Of course, the arrangement of the antennas 1 does not have to be symmetrical as shown in FIG. 21 and may not be two. The best performance is when it is mounted at the center of the long side of the substrate where the density of the current flowing on the substrate is the highest, but it functions as an antenna wherever it is mounted around the substrate 19. Therefore, the antenna device can be obtained without worrying about the occupied area of the antenna by mounting it in an empty space, and when the antenna 1 is shorter than other tall mounting parts, the antenna device is tall. By mounting the antenna 1 in the gap between the mounting components, the thickness of the antenna 1 does not affect the thickness design of the mobile terminal at all, so that the thickness increases like a mobile terminal using a conventional sheet-like antenna. An antenna device can be obtained without this. Although the antenna 1 is mounted on the substrate 19 in FIG. 20, a metal body such as the battery 20 or the frame of the liquid crystal panel 17 can be used as the antenna device by mounting the antenna 1.

  FIG. 22 is a circuit diagram of the antenna circuit of the present invention. (A) is a circuit diagram in the case of mounting one antenna, (b) is a circuit diagram in the case of mounting two antennas, and (c) is a case of using three antennas. The antenna 1, the terminal 5, the resonance frequency adjusting capacitor 34, and a matching circuit connection end 33 connected to a matching circuit or IC. When a plurality of antennas are used, the number of antennas can be easily increased by connecting the antennas 1 with the connecting conductors 32, and therefore the characteristics can be easily improved. The capacitance of the resonance frequency adjusting capacitor 34 is determined by the inductance of the antenna 1 when the antenna 1 is mounted at a predetermined location and the frequency to be used. In FIG. 22, only one resonance frequency adjusting capacitor 34 is shown, but a plurality of capacitors 34 may be used for fine adjustment. The resonance frequency adjusting capacitor 34 may be on a matching circuit connected to the matching circuit connection end 33.

  FIG. 23 is an exploded perspective view of a mobile terminal using the antenna of the embodiment of the present invention. The antenna 1 is disposed on the inner surface of the housing 22. The metal body used by the antenna 1 is a substrate 19 or a component mounted on the substrate 19 (not shown). With such an arrangement, even if the antenna 1 is not directly mounted on the metal body, the structure in which the metal body exists in the vicinity of the antenna 1 when assembled has a good communication performance. It becomes an antenna device. As described above, the antenna 1 may be provided not only on the metal body but also on the inner surface of the housing.

  According to the antenna and the antenna device of the present invention, since the antenna device can be formed by using the gap between the components of the housing, the space of the antenna device can be saved, which is useful for downsizing the housing. It can be used as an RF-ID antenna (tag) for mobile phones.

DESCRIPTION OF SYMBOLS 1 Antenna 2 Protective material 3 Base | substrate 4 Conductor 5 Terminal 6 Fixing terminal 7 Board | substrate 8 Conductor pattern 9 Input / output terminal land 10 Fixed terminal land 11 Ground extraction part 12 Conductor pattern outer periphery 13 Magnetic field 14 Current 15 Input / output terminal land 16 Mobile terminal 17 Liquid crystal panel 18 Button 19 Substrate 20 Battery 21 Housing 22 Housing 30 Coil portion 31 Exposed portion 32 Connection conductor between antennas 33 Matching circuit connection end 34 Resonance frequency adjusting capacitor 34

Claims (5)

A base, a coil formed by a conductor wound around the base, and a plurality of terminals connected to the conductor; the base includes a conductor except for the start and end of winding of the coil The antenna is characterized in that a base bare portion, which is a portion where no coil exists, is formed, the terminal is arranged on the surface side parallel to the coil axis of the coil portion, and is arranged on the base bare portion side. The antenna according to claim 1, wherein the number of windings of the coil portion of the antenna is approximately half a round than an integral multiple. The antenna according to claim 1, wherein a base exposed portion is formed at both ends of the base. 2. The antenna according to claim 1, wherein the plurality of terminals connected to the coil portion are on the same base exposed portion side. The antenna device according to claim 1, wherein at least one of the base exposed portions in the antenna is mounted so as to be located outside an outer periphery of a metal body on which the antenna is mounted.

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