JP2008061009A - Antenna system and wireless apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent performance from being reduced when loop-shaped antenna elements are switched among a plurality of systems relating to respective functions and shared or made common in a wireless apparatus that is made multi-functional by providing the antenna elements, and to adjust characteristics of an antenna system including loop-shaped antenna elements independently by functions. <P>SOLUTION: An antenna system 1 operates as an antenna of a first system connecting a radio circuit between a feeding terminal 15 and a grounding terminal 17 by a resonance circuit composed of loop-shaped antenna elements 10 and capacitive elements 11 and 12. Furthermore, a switch element 14 is changed over to operate the antenna system as an antenna of a second system connecting a radio circuit between a feeding terminal 16 and the grounding terminal 17 by a resonance circuit composed of the antenna elements 10 and the capacitive element 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna device and a radio device, and more particularly to an antenna device and a radio device that use a conductor formed in a loop shape as an antenna element.

  2. Description of the Related Art A card-type device is known that includes an antenna element formed of a conductor formed in a loop shape and an integrated circuit (IC) that transmits and receives data to and from an external device (reader / writer) via the antenna element. . Such a device is called a non-contact IC card. In addition, a wireless device (for example, a mobile phone) having a function equivalent to that of a non-contact IC card is known. These non-contact IC cards or wireless devices are used for purposes such as fee settlement, entrance / exit management, authentication, and the like.

  A technique for mounting both a non-contact IC card function and a reader / writer function in a wireless device such as a cellular phone is also known (for example, see Patent Document 1). According to the above Patent Document 1, a semiconductor integrated circuit is configured by combining a non-contact IC card function and a reader / writer function, and communication with an external reader / writer or an external non-contact IC card is performed via a common antenna. It is stated that it can be done.

  In addition to this, a technique for reducing the size and improving the efficiency of the reader / writer is known (see, for example, Patent Document 2 or Patent Document 3). According to the above-mentioned Patent Document 2, the reader / writer is configured to be connected to the first resonance circuit including the loop antenna from the transmission unit and connected from the loop antenna to the reception unit via the coupling capacitor and the second resonance circuit. Thus, it is described that both transmission efficiency and reception sensitivity are improved by separating transmission and reception.

According to the above-mentioned Patent Document 3, it is described that matching and the suppression of higher harmonics are achieved and the antenna efficiency is improved by devising the connection of a loop coil and a capacitor having a three-terminal reader / writer.
JP 2006-74423 A (2nd, 7th to 12th pages, FIG. 3) Japanese Patent Laying-Open No. 2005-26741 (pages 2, 6 to 8, FIG. 1) Japanese Patent Laid-Open No. 2004-235484 (2nd, 6th to 9th pages, FIG. 1)

  The size of a loop-like antenna element (for example, but not limited to a non-contact IC card function or a reader / writer function) incorporated in a wireless device such as a cellular phone is a frequency band to be used (for example, currently practical use). In the case of a non-contact IC card system that has been developed, the frequency may be considerably large.

  On the other hand, for example, wireless devices such as mobile phones tend to be equipped with a plurality of system functions and become multi-functional. It is convenient if they can be shared, and space efficiency is also improved. The first problem to be solved by the present invention is to share or share the loop-shaped antenna element as described above.

  When both a plurality of functions are mounted on a wireless device, the frequency used for each function is different (for example, a mobile phone and a non-contact IC card), and the same (for example, a non-contact IC card and a reader / writer) Can be considered. The antenna device including the loop-shaped antenna element that is shared or shared as described above is switched to and connected to a radio circuit related to each function. It is desirable that characteristics such as the resonance frequency of the antenna device can be adjusted independently for each function. The second problem to be solved by the present invention is to enable such independent adjustment.

  None of the techniques disclosed in Patent Document 1 to Patent Document 3 described above share the loop-shaped antenna element as described above, and cannot solve the first problem. There was a problem.

  The technique disclosed in Patent Document 1 described above does not allow the characteristics of the loop-shaped antenna element in each of the non-contact IC card function and the reader / writer function to be adjusted independently, and solves the second problem. There was a problem that you can't. The technology disclosed in Patent Document 2 or Patent Document 3 described above relates only to the reader / writer function, and has a problem that the second problem cannot be solved.

  A conventional antenna device for a non-contact IC card or a reader / writer is configured as a parallel resonant circuit including a loop-shaped antenna element and a capacitive element as shown in FIG. 8A, for example. The antenna device 8a in the figure is configured by a parallel resonant circuit including an antenna element 80 and a capacitive element 81 made of a conductor formed in a loop shape. The antenna device 8a is fed by connecting the feeding end 85 and the ground end 87 to a wireless circuit (not shown).

The inductance value of the antenna element 80 is L (80), the resistance value is R (80), the capacitance value of the capacitive element 81 is C (81), and the resonance angular frequency of the parallel resonant circuit composed of the antenna element 80 and the capacitive element 81 Is ω (8a) and the Q value of the antenna element 80 is Q (8a),
Q (8a) = (ω (8a) × L (80)) / R (80)
However, it is represented by the reciprocal of the square root of ω (8a) = (L (80) × C (81)).

  As shown in FIG. 8B, the antenna device 8a can be modified to configure the antenna device 8b that can be shared by a plurality of systems (referred to as the first system and the second system). In the antenna device 8b, a switch element 84 is added to the configuration of the antenna device 8a, and an upper end (upper end) of the antenna element 80 in the drawing is switched by the switch element 84, or a feed end 85 or a newly provided feed end. 86 is configured to be electrically connected to any one of 86.

  Similarly to the antenna device 8a, the antenna device 8b connects the feeding end 85 and the grounding end 87 to a radio circuit for the first system (not shown) and switches the switch element 84 to the feeding end 85 side so as to be used for the first system. In addition to being fed as an antenna, the feed end 86 and the ground end 87 are connected to another radio circuit for the second system (not shown), and the switch element 84 is switched to the feed end 86 side to switch for the second system. It is fed as an antenna.

The inductance value and resistance value of the antenna element 80 and the capacitance value of the capacitive element 81 are the same as those in FIG. 8A, and the conduction resistance of the switch element 84 is R (84). Since this value is in series with the resistance value R (80) of the antenna element 80, if the Q value of the antenna element 80 in FIG. 8B is Q (8b),
Q (8b) = (ω (8a) × L (80)) / (R (84) + R (80))
It is represented by

Therefore,
Q (8b) = Q (8a) / (1+ (R (84) / R (80)))
Thus, the Q value of the antenna element 80 (when the switch element 84 is inserted) in FIG. 8B is lower than the Q value of the antenna element 80 in FIG.

  Since the voltage value induced between both ends of the antenna element 80 is proportional to the above Q value, the performance of the antenna device 8b when the switch element 84 is provided and switched to the feeding end 85 side is the performance of the antenna device 8a. Inferior to For example, if the value of R (84) and the value of R (80) are substantially equal, the performance is almost halved by inserting the switch element 84.

  As shown in FIG. 8C, the antenna device 8b is modified to constitute the antenna device 8c. The antenna device 8c is different from the antenna device 8b in that the switch element 84 is provided between the capacitive element 81 and the feeding end 85 (or 86), and the other points are the same as the antenna device 8b.

  The Q value of the antenna element 80 when the switch element 84 is switched to the feeding end 85 side in FIG. 8C is the same Q (8a) as in FIG. Further, the resonance angular frequency of the parallel resonance circuit composed of the antenna element 80 and the capacitive element 81 is ω (8a) which is the same as that in FIG. The resistance of the impedance of the parallel resonance circuit composed of the antenna element 80 and the capacitive element 81 is highest at the resonance frequency ω (8a), and generally takes a value several orders of magnitude higher than the conduction resistance of the switch element 84. Therefore, the decrease in the voltage induced at both ends of the antenna element 80 due to the provision of the switch element 84 is limited to 1% or less, and the above problem in the configuration of FIG. 8B (degradation of performance due to the insertion of the switch element 84). ) Is reduced.

  As shown in FIG. 8D, the antenna device 8c is modified to constitute the antenna device 8d. The antenna device 8d differs from the antenna device 8c in that, for example, a quarter-wave monopole additional antenna element 89 is electrically connected to the upper end of the antenna element 80, and the other points are the same as the antenna device 8c. It is.

  The additional antenna element 89 generally has a resonance frequency different from that of the parallel resonance circuit composed of the antenna element 80 and the capacitive element 81. The impedance of the parallel resonant circuit at the resonant frequency of the additional antenna element 89 is lower than the maximum value at the parallel resonant angular frequency ω (8a). Therefore, when the switch element 84 is switched to the power feed end 86 side, the antenna current fed from the power feed end 86 flows through not only the additional antenna element 89 but also the parallel resonant circuit described above. Equivalent to increased loss.

  When the constant of the antenna element 80 or the capacitive element 81 is adjusted in order to improve the loss of the additional antenna element 89, the value of the resonance frequency when the switch element 84 is switched to the feeding end 85 side changes. That is, the independence of adjustment cannot be maintained.

  The above description with reference to FIG. 8 can be summarized as follows. In the configuration of FIG. 8B, the insertion of the switch element 84 decreases the Q value of the antenna element 80 and decreases the antenna performance. In the configuration of FIG. 8C or FIG. 8D in which the above is improved, there is a problem that it is difficult to sufficiently exhibit the performance even when the additional antenna element is provided.

  The present invention has been made to solve the above-described problems. In a multi-function wireless device, the performance when a loop antenna element is shared or shared among a plurality of systems related to each function. An object of the present invention is to prevent degradation and to adjust the characteristics of an antenna device including a loop-shaped antenna element independently by function.

  In order to achieve the above object, an antenna device of the present invention has a first feeding end, a second feeding end, a first end, and a second end, and is formed in a loop shape. An antenna element made of a conductor, a first capacitive element connected in parallel with the antenna element, and a first end of the antenna element are the first feeding end or the second feeding end A switch element that switches to be electrically connected to either one of the switches, one end is electrically connected to the first feeding end, and the other end is electrically connected to the second end of the antenna element. And a second capacitive element.

  The wireless device of the present invention includes a first feeding end and a second feeding end, an antenna element made of a conductor having a first end and a second end and formed in a loop shape, A first capacitive element connected in parallel with the antenna element and a first end of the antenna element are electrically connected to either the first feeding end or the second feeding end. And a second capacitive element having one end electrically connected to the first feeding end and the other end electrically connected to the second end of the antenna element. An antenna device, a transmission / reception circuit connected to one of the first feeding end or the second feeding end of the antenna device, and the first feeding end or the second feeding end of the antenna device. And a receiving circuit connected to the other of the two.

  According to the present invention, by selecting a configuration of a resonance circuit including a loop-shaped antenna element and a switch element, a circuit including the loop-shaped antenna element can be shared between a plurality of systems in a multi-functional radio apparatus. It is possible to adjust the characteristics of the antenna device including a common antenna element including a loop-shaped antenna element independently for each function.

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

  Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. Fig.1 (a) is a figure showing the structure and connection of the antenna apparatus 1 which concern on Example 1 of this invention. The antenna device 1 includes an antenna element 10, a capacitive element 11, a capacitive element 12, and a switch element 14. The antenna element 10 is a two-terminal element made of a conductor formed in a loop shape, and has end portions (upper and lower ends) on the upper side and the lower side in the drawing. The capacitive element 11 and the capacitive element 12 are two-terminal elements such as a fixed capacitor, a variable capacitor, and a varactor diode, respectively. The switch element 14 is a mechanical switch or an electronic switch (semiconductor switch or the like). The capacitive element 11 is connected in parallel with the antenna element 10.

  The antenna device 1 is configured to be shared by switching to the system 2, and has a feeding end 15, a feeding end 16, and a grounding end 17. The upper end of the antenna element 10 is electrically connected to the power feeding end 15 via the switch element 14. The capacitive element 12 has one end electrically connected to the feeding end 15 and the other end electrically connected to the lower end of the antenna element 10 and the ground end 17.

  In FIG. 1A, the inductance value of the antenna element 10 is L (10), the Q value is Q (1a), the capacitance value of the capacitive element 11 is C (11), and the capacitance value of the capacitive element 12 is C ( 12). The antenna element 10 forms a parallel resonance circuit with the capacitive element 11 and the capacitive element 12, and the resonance angular frequency is equal to the reciprocal of the square root of (L (10) × (C (11) + C (12))). . By connecting a radio circuit (not shown) of a system using a frequency determined by this value or a frequency in the vicinity thereof (this is referred to as a first system) between the feeding end 15 and the grounding end 17, the antenna device 1 is configured. It can be used in the first system.

  The decrease in the Q value of the antenna element 10 due to the provision of the switch element 14 in the first system causes the value of the conduction resistance of the switch element 14 to be changed from the antenna element 10 and the capacitive element 11 at the operating frequency of the first system. By making it smaller than the resistance of the impedance of the parallel resonant circuit, it can be limited in the same manner as described above with reference to FIG.

  FIG. 1B shows the configuration and connection of the antenna device 1 as in FIG. 1A, and is the same diagram as FIG. 1A except that the switch element 14 is switched. The upper end of the antenna element 10 is electrically connected to the feeding end 16 via the switch element 14. The antenna element 10 forms a parallel resonance circuit with the capacitive element 11, and the resonance angular frequency is equal to the reciprocal of the square root of (L (10) × C (11)). By connecting a radio circuit (not shown) of a system using a frequency determined by this value or a frequency in the vicinity thereof (referred to as a second system) between the feeding end 16 and the grounding end 17, the antenna device 1 is configured. It can be used in the second system.

  The decrease in the Q value of the antenna element 10 due to the provision of the switch element 14 in the second system means that the conduction resistance value of the switch element 14 is different from the operating frequency of the second system, that is, from the antenna element 10 and the capacitive element 11. Since it is sufficiently smaller than the resistance of the impedance of the parallel resonant circuit at the resonant frequency of the parallel resonant circuit, it can be limited in the same manner as described above with reference to FIG.

  According to the first embodiment of the present invention, a plurality of resonance circuits including one loop antenna element can be formed by switching the switch elements, thereby configuring a plurality of system antennas used at different frequencies. can do.

  Hereinafter, Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2A is a diagram illustrating the configuration and connection of the antenna device 2 according to the second embodiment of the present invention. Since the antenna device 2 is obtained by adding the capacitive element 23 to the antenna device 1 shown in FIG. 1A or 1B, the same configuration as the antenna device 1 is denoted by the same reference numeral. Description is omitted. The capacitive element 23 is a two-terminal element such as a fixed capacitor, a variable capacitor, or a varactor diode. One end of the capacitive element 23 is electrically connected to the feeding end 16, and the other end is electrically connected to the lower end of the antenna element 10 and the ground end 17.

  In FIG. 2A, the upper end of the antenna element 10 is electrically connected to the feeding end 15 via the switch element 14 in the same manner as described with reference to FIG. The resonant angular frequency of the parallel resonant circuit formed by the antenna element 10, the capacitive element 11, and the capacitive element 12 is equal to the reciprocal of the square root of (L (10) × (C (11) + C (12))). The antenna device 2 is used in the first system by connecting a radio circuit (not shown) of the first system using a frequency determined by this value or a frequency in the vicinity thereof between the feeding end 15 and the ground end 17. Can do.

  FIG. 2B shows the configuration and connection of the antenna device 2 as in FIG. 2A, and is the same diagram as FIG. 2A except that the switch element 14 is switched. The upper end of the antenna element 10 is electrically connected to the feeding end 16 via the switch element 14. The antenna element 10 forms a parallel resonant circuit with the capacitive element 23 and the capacitive element 11, and the resonance angular frequency is equal to the reciprocal of the square root of (L (10) × (C (11) + C (23))). (C (23) is the capacitance value of the capacitive element 23). The antenna device 2 is used in the second system by connecting a radio circuit (not shown) of the second system using a frequency determined by this value or a frequency in the vicinity thereof between the feeding end 16 and the ground end 17. Can do.

  The antenna device 2 can be used as an antenna for a plurality of systems used at different frequencies, like the antenna device 1 described in the first embodiment. The decrease in the Q value of the antenna element 10 due to the provision of the switch element 14 at each frequency is obtained by changing the conduction resistance value of the switch element 14 to the impedance at each frequency of the parallel resonant circuit including the antenna element 10 and the capacitive element 11. By making it smaller than the resistance component, it can be limited in the same manner as described in the first embodiment.

  For example, when the first system is a contactless IC card and the second system is a reader / writer, the frequency used by both systems is the same or close. The first embodiment is based on the premise that the use frequency of the first system to which the antenna device 1 is fed from the feed end 15 is higher than the use frequency of the second system that is fed from the feed end 16. Therefore, it is difficult to apply the antenna device 1 of the first embodiment when the operating frequencies of the first and second systems are the same or close as described above.

  On the other hand, the antenna device 2 can be easily applied even when the operating frequencies of the first and second systems are the same or close as described above. Even if the frequency is adjusted in one system, the other system can be prevented from being affected.

  According to the second embodiment of the present invention, it is possible to form a plurality of resonant circuits including one loop antenna element by switching the switch elements, and the antennas for a plurality of systems used at the same or close frequency. The additional effect that it can be used as is obtained.

  Hereinafter, Embodiment 3 of the present invention will be described with reference to FIG. Fig.3 (a) is a figure showing the structure and connection of the antenna apparatus 3 which concern on Example 3 of this invention. Since the antenna device 3 is obtained by adding the additional antenna element 30 to the antenna device 1 shown in FIG. 1A or 1B, the same configuration as the antenna device 1 is denoted by the same reference numeral, Description is omitted. The upper end of the antenna element 10 included in the antenna device 3 is electrically connected to the power feeding end 15 via the switch element 14.

  The additional antenna element 30 is electrically connected to the upper end of the antenna element 10. The resonance frequency of the additional antenna element 30 is set to the resonance frequency of the parallel resonance circuit including the antenna element 10 and the capacitive element 11 or the vicinity thereof. For example, when the additional antenna element 30 is a quarter-wave monopole antenna, it is considered that the additional antenna element 30 is connected to the feeding end 16 by switching the switching element 14, and the additional antenna element 30 passes from the feeding end 16 through the switching element 14. The above setting is possible by selecting the line length up to the open end of.

  In FIG. 3A, the antenna element 10 forms a parallel resonance circuit with the capacitive element 11 and the capacitive element 12, and the first resonance frequency using the resonance frequency or a frequency in the vicinity thereof is the same as described in the first embodiment. The antenna device 3 can be used in the system. The decrease in the Q value of the antenna element 10 due to the provision of the switch element 14 can be limited as in the first embodiment. By taking a sufficiently large difference between the resonant frequency of the additional antenna element 30 and the parallel resonant frequency, the influence of the additional antenna element 30 added can be limited.

  FIG. 3B shows the configuration and connection of the antenna device 3 as in FIG. 3A, and is the same diagram as FIG. 3A except that the switch element 14 is switched. The additional antenna element 30 is electrically connected to the feeding end 16 via the switch element 14. The antenna element 10 constitutes a parallel resonant circuit with the capacitive element 11, and the impedance of the parallel resonant circuit takes the highest value at the resonant frequency. Therefore, unlike the case shown in FIG. 8D, the side flow of the antenna current fed from the feeding end 16 to the additional antenna element 30 to the parallel resonant circuit is limited, and the increase in the loss of the additional antenna element 30 is suppressed. be able to.

  Even when the constant of the antenna element 10 or the capacitive element 11 is adjusted to improve the loss of the additional antenna element 30, the resonance frequency value when the switch element 14 is switched to the feeding end 15 side is capacitive. It can be adjusted by the constant of the element 12. That is, the independence of adjustment is maintained.

  According to the third embodiment of the present invention, it is possible to form a plurality of resonance circuits including one loop antenna element by switching the switch elements, and to resonate at one of the resonance frequencies or a frequency in the vicinity thereof. By providing the antennas, it is possible to efficiently configure the antennas for a plurality of systems used at different frequencies.

  A fourth embodiment of the present invention will be described below with reference to FIG. FIG. 4A is a diagram illustrating the configuration and connection of the antenna device 4 according to the fourth embodiment of the present invention. Since the antenna device 4 is obtained by adding a switch element 44 to the antenna device 3 shown in FIG. 3A or 3B, the same components as those of the antenna device 3 are denoted by the same reference numerals and described. Is omitted. The upper end of the antenna element 10 is electrically connected to the power feeding end 15 via the switch element 14. The lower end of the antenna element 10 is electrically connected to the ground end 17 via the switch element 44.

  The circuit of the antenna device 4 shown in FIG. 4A is electrically equivalent to the circuit of the antenna device 3 shown in FIG. Therefore, the antenna element 10 forms a parallel resonance circuit with the capacitive element 11 and the capacitive element 12, and the antenna device 4 in the first system using the resonance frequency or a frequency in the vicinity thereof as described in the first embodiment. Can be used.

  FIG. 4B shows the configuration and connection of the antenna device 4 as in FIG. 4A, and is the same diagram as FIG. 4A except that the switch element 14 and the switch element 44 are switched. Note that the switch element 14 and the switch element 44 are configured to be switched in conjunction with each other as described above. The additional antenna element 30 is electrically connected to the feeding end 16 via the switch element 14.

  The lower end of the antenna element 10 is opened because the switch element 44 is switched. As a result, the antenna current fed from the feeding end 16 to the additional antenna element 30 does not flow to the parallel resonant circuit composed of the antenna element 10 and the capacitive element 11, and the loss of the additional antenna element 30 does not increase. Unlike the case of the third embodiment, it is not necessary to set the resonance frequency of the additional antenna element 30 at or near the resonance frequency of the parallel resonance circuit including the antenna element 10 and the capacitive element 11 in order to obtain this effect.

  According to the fourth embodiment of the present invention, there is an additional effect that the degree of freedom in setting the resonance frequency of the additional antenna element can be increased.

  The fifth embodiment of the present invention will be described below with reference to FIGS. FIG. 5 is a diagram illustrating the configuration and connection of the wireless device 5 according to the fifth embodiment of the present invention. The wireless device 5 includes the antenna device 1 described in the first embodiment, a transmission / reception circuit 51, and a reception circuit 52. Since the configuration of the antenna device 1 is as described in the first embodiment, the description thereof is omitted.

  The transmission / reception circuit 51 is connected to the power feeding end 15 and the ground end 17 of the antenna device 1 as a radio circuit of the first system described in the first embodiment. The transmission / reception circuit 51 is, for example, a non-contact IC card or a transmission / reception circuit for a reader / writer, but is not limited thereto. The receiving circuit 52 is connected to the power feeding end 16 and the grounding end 17 of the antenna device 1 as a radio circuit of the second system described in the first embodiment. The receiving circuit 52 is, for example, a receiving circuit for a read-only device, but is not limited thereto. The wireless device 5 can be applied when the use frequency of the transmission / reception circuit 51 is higher than the use frequency of the reception circuit 52.

  FIG. 6 is a diagram illustrating the configuration and connection of the wireless device 6 according to the fifth embodiment of the present invention. The wireless device 6 includes the antenna device 1 described in the first embodiment, a transmission / reception circuit 61, and a reception circuit 62.

  The transmission / reception circuit 61 is connected to the power feeding end 16 and the ground end 17 of the antenna device 1 as a radio circuit of the second system described in the first embodiment. The transmission / reception circuit 61 is, for example, a transmission / reception circuit for a non-contact IC card or a reader / writer, but is not limited thereto. The receiving circuit 62 is connected to the power feeding end 15 and the grounding end 17 of the antenna device 1 as a radio circuit of the first system described in the first embodiment. The receiving circuit 62 is a receiving circuit for a read-only device, for example, but is not limited thereto. The wireless device 6 can be applied when the use frequency of the reception circuit 62 is higher than the use frequency of the transmission / reception circuit 61.

  In the configuration of the wireless device 6 shown in FIG. 6, the antenna device 1 is replaced with the antenna device 3 described in the third embodiment or the antenna device 4 described in the fourth embodiment, and the transmission / reception circuit 61 is used for, for example, a cellular phone or a wireless LAN. The transmission / reception circuit may be used. In this case, the use frequency of the reception circuit 62 may be lower than the use frequency of the transmission / reception circuit 61.

  FIG. 7 is a diagram illustrating the configuration and connection of the wireless device 7 according to the fifth embodiment of the present invention. The wireless device 7 includes the antenna device 2 described in the second embodiment, a transmission / reception circuit 71, and a reception circuit 72. Since the configuration of the antenna device 2 is as described in the second embodiment, the description thereof is omitted.

  The transmission / reception circuit 71 is connected to the feeding end 15 and the grounding end 17 of the antenna device 2 as a wireless circuit of the first system described in the second embodiment. The transmission / reception circuit 71 is, for example, a transmission / reception circuit for a non-contact IC card or a reader / writer, but is not limited thereto. The receiving circuit 72 is connected to the power feeding end 16 and the grounding end 17 of the antenna device 2 as a radio circuit of the second system described in the second embodiment. The receiving circuit 72 is, for example, a receiving circuit for a read-only device, but is not limited thereto.

  Similarly to the wireless device 5 described above, the wireless device 7 can be applied when the frequency used by the transmission / reception circuit 71 and the frequency used by the reception circuit 72 are different. The wireless device 7 can be applied when the frequency used by the transmission / reception circuit 71 and the frequency used by the reception circuit 72 are the same or close to each other. When the inter-terminal capacitance is different between the amplifier of the transmission circuit and the amplifier of the reception circuit, the advantage that the plurality of resonance circuits can be adjusted independently by the configuration of the antenna device 2 is exhibited.

  According to the fifth embodiment of the present invention, a radio apparatus in which the antenna apparatus described in the first to fourth embodiments is shared or shared by a plurality of systems is configured, and the resonance frequency of each system is made different. And can be adjusted independently.

  The conditions such as the configuration, connection, and frequency of the antenna device or wireless device described in the first to fifth embodiments are examples, and various modifications can be made without departing from the scope of the present invention.

The figure showing the structure and connection of the antenna apparatus which concern on Example 1 of this invention (The distinction of (a) and (b) respond | corresponds to switching of a switch element). The figure showing the structure and connection of the antenna apparatus which concern on Example 2 of this invention (The distinction of (a) and (b) respond | corresponds to switching of a switch element). The figure showing the structure and connection of the antenna apparatus which concern on Example 3 of this invention (The distinction of (a) and (b) respond | corresponds to switching of a switch element). The figure showing the structure and connection of the antenna apparatus which concern on Example 4 of this invention (The distinction of (a) and (b) respond | corresponds to switching of a switch element). The figure showing the 1st structure and connection of the radio | wireless apparatus which concern on Example 5 of this invention. The figure showing the 2nd structure and connection of the radio | wireless apparatus which concern on Example 5 of this invention. The figure showing the 3rd structure and connection of the radio | wireless apparatus which concern on Example 5 of this invention. (A) is a diagram showing the configuration and connection of a conventional antenna device for a non-contact IC card, etc., (b) is a diagram showing the configuration and connection of the modified example, (c) is a further interchange of the positional relationship of the elements The figure showing the structure and connection in a case, (d) is a figure showing the structure and connection when an additional antenna element is further added.

Explanation of symbols

1, 2, 3, 4 Antenna device 5, 6, 7 Radio device 10 Antenna element 11, 12, 23 Capacitive element 14 Switch element 15, 16 Feed end 17 Ground end 30 Additional antenna elements 51, 61, 71 Transmission / reception circuit 52 62, 72 Receiver circuit

Claims (5)

A first feeding end;
A second feeding end;
An antenna element having a first end and a second end and made of a conductor formed in a loop;
A first capacitive element connected in parallel with the antenna element;
A switching element that switches so that the first end of the antenna element is electrically connected to either the first feeding end or the second feeding end;
An antenna comprising: a second capacitive element having one end electrically connected to the first feeding end and the other end electrically connected to the second end of the antenna element. apparatus.   And a third capacitive element having one end electrically connected to the second feeding end and the other end electrically connected to the second end of the antenna element. The antenna device according to claim 1.   An additional antenna element electrically connected to the first end of the antenna element and resonating at or near a resonance frequency determined by an inductance value of the antenna element and a capacitance value of the first capacitive element; The antenna device according to claim 1. An additional antenna element electrically connected to the first end of the antenna element;
When the switch element is switched so that the first end of the antenna element is electrically connected to the second feeding end, the second end of the antenna element is opened. The antenna device according to claim 1, further comprising an additional switch element electrically connected to the second end of the element. An antenna element made of a conductor having a first feeding end and a second feeding end, a first end portion and a second end portion and formed in a loop shape, and connected in parallel with the antenna element A first capacitive element, a switching element for switching the first end of the antenna element to be electrically connected to either the first feeding end or the second feeding end, and one end An antenna device comprising: a second capacitive element electrically connected to the first feeding end and the other end electrically connected to the second end of the antenna element;
A transmission / reception circuit connected to one of the first feeding end or the second feeding end of the antenna device;
And a receiving circuit connected to the other of the first feeding end and the second feeding end of the antenna device.

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