JP2007174582A - Proximity antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend a reachable distance by efficiently radiating radio waves into the air from a radio tag of output limited within the regulation of the radio low. <P>SOLUTION: A radio tag 7 transmits from an antenna 7b an electromagnetic wave resulting from periodically oscillating a fundamental wave and modulating an ID code. In the vicinity of the radio tag 7, an electrostatic coupled proximity antenna 25 is installed, so that the electromagnetic wave transmitted from the radio tag 7 is induced in the electrostatic coupled proximity antenna and an electromagnetic field is secondly radiated from the electrostatic coupled proximity antenna 25. Furthermore, when the electrostatic coupled proximity antenna 25 and a proximity magnetic field antenna are installed in the vicinity of the radio tag 7, radiation in which an electric field component in the electromagnetic field is dominant is made first, the radiation is coupled to the electrostatic coupled proximity antenna 25 outside the tag by electrostatic coupling, and energy is radiated as an electromagnetic component into the air therefrom. Moreover, a magnetic field component in this energy radiated electromagnetic wave is coupled to a proximity magnetic field antenna 9 and re-radiated into the air as a magnetic field component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a low-power radio apparatus capable of further extending the communication distance of a radio tag used to detect the presence of an object or a human body.

  As a conventional low-power radio apparatus, a radio tag system shown in FIG. 11 is known.

  A wireless tag 7 is accommodated in a name tag 5 attached to the human body 3, and an electromagnetic wave to which an ID code is periodically added is transmitted to the surroundings from the wireless tag 7, and the electromagnetic wave from the wireless tag 7 is received by the receiver 1. And an ID code is output (Patent Document 1).

  By the way, wireless tags that can be used in Japan at present are roughly classified into the following four types.

(1) 125 KHz and 135 KHz band wireless tags (2) 13 MHz band wireless tags (3) 2.4 GHz band wireless tags (4) Weak radio wave type wireless tags Among these, (1) and (2) have a search distance of several tens of centimeters (3) and (4) are long-distance types with a search distance of several meters to several tens of meters.

  Further, (3) has a characteristic that the straight-line performance is remarkable and the communication distance is easy to take long due to the property of the microwave band, but it is difficult to propagate to the shadow. In the case of an active wireless tag equipped with a battery, a complicated wireless circuit is built in, and an electronic device in a microwave band is expensive. Therefore, the active wireless tag is not suitable for applications requiring small size and low price.

Furthermore, since (4) has no frequency limitation, it has excellent long-distance communication characteristics used at a frequency of about 300 MHz, which is advantageous in terms of radio wave propagation characteristics such as reflection and antenna size, and is an electronic device in the UHF band. The cost is low.
JP 2005-27104 A

  However, the limit value of weak radio waves regulated by the Radio Law must be a transmission output with an electric field strength of 54 dBμV / m (500 μV / m) or less at a distance of 3 m from the wireless tag. For this reason, the reach is almost determined by this transmission output.

  In addition, the wireless tag is used by attaching it to an object or human body, but the radio wave radiated from the wireless tag may be absorbed by the object or human body, compared to the performance when the wireless tag is placed in an ideal space, There was a problem that the reach of radio waves decreased.

  The present invention has been made in view of the above, and the purpose thereof is to make it difficult for radio waves from an output radio tag limited within the regulations of the Radio Law to be affected by an object or the like to which the radio tag is attached. Then, it is providing the low power radio | wireless apparatus which can radiate | emit to space efficiently and can extend the reachable distance.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a capacitively coupled near-field antenna installed close to a wireless tag having a built-in antenna for transmitting electromagnetic waves and facing one surface of the antenna. The wireless tag emits radiation whose electric field component is dominant, and this radiation causes energy coupling to the electrostatic coupling type proximity antenna by electrostatic coupling to radiate energy into the space as an electromagnetic field component. .

  According to a second aspect of the present invention, in order to solve the above-mentioned problem, the electrostatic coupling type near field antenna is formed by a flat conductor disposed so as to face one surface of the antenna built in the wireless tag. The gist is that

  In order to solve the above-mentioned problem, the capacitively coupled near-field antenna has a multilayer seal in which a pair of thin seals made of resin are attached to both surfaces of the conductor. The gist is to be housed in the container.

  In order to solve the above-mentioned problem, the capacitively coupled near field antenna has a conductor connected to one side surface of the case housing the wireless tag, and the surface of the conductor is The gist is that a thin seal made of resin is attached and stored.

  In order to solve the above problems, the invention according to claim 5 is characterized in that the capacitively coupled near field antenna is stored by applying a resin liquid to the surface of the conductor.

  In order to solve the above-mentioned problem, the invention according to claim 6 comprises a card case for storing the wireless tag and storing a card made of a multilayer seal storing the electrostatic coupling type near field antenna. To do.

  In order to solve the above-mentioned problem, the invention according to claim 7 is a capacitively coupled near-field antenna installed close to a wireless tag having a built-in antenna for transmitting electromagnetic waves and facing one surface of the antenna. The electrostatic coupling type near field antenna is formed of a flat conductor, and radiation with a dominant electric field component is made from the wireless tag, and electrostatic coupling is made to the electrostatic coupling type proximity antenna by the radiation. The gist is that the energy is coupled by radiated into the space as an electromagnetic field component.

  According to an eighth aspect of the present invention, in order to solve the above-mentioned problem, the electrostatic coupling type near field antenna is formed of a flat conductor disposed so as to face an antenna built in the wireless tag, and the wireless The gist of the invention is to have a lead wire having a length that is an integral multiple of a quarter wavelength of the electromagnetic wave generated from the tag.

  In order to solve the above-described problem, the invention according to claim 9 includes a capacitively coupled near-field antenna that is disposed close to a wireless tag including an antenna that transmits electromagnetic waves and is opposed to the antenna. Proximity magnetic field antenna that is close to the wireless tag and resonates at the frequency of the electromagnetic wave transmitted from the wireless tag, and the field component is radiated dominantly from the wireless tag. The energy is coupled to the antenna by electrostatic coupling and is radiated to space as an electromagnetic field component, and the magnetic field component of the radiated electromagnetic wave is coupled to the near-field antenna and secondarily radiated to the space as a magnetic field component. And

  According to a tenth aspect of the present invention, in order to solve the above problem, the near magnetic field antenna has capacitors at both ends of a conductor whose entire circumference is 0.5 wavelength or less with respect to the wavelength of the electromagnetic wave transmitted from the wireless tag. It is formed from a closed loop formed by connecting.

  ADVANTAGE OF THE INVENTION According to this invention, the radio wave from the radio | wireless tag of the output limited within the restrictions of the radio wave law can be efficiently radiated to space, and the reachable distance can be extended.

  Many of the wireless tags have a magnetic antenna mounted therein, but some have an electric field antenna. In this case, even when a magnetic field type is used for the external proximity antenna, electromagnetic field coupling is not performed efficiently. However, according to the present invention, since both the near field antenna and the near field antenna are mounted, the near field antenna first transmits the electromagnetic field energy to the inside of the tag even for the wireless tag mounted with the field type antenna. Then, the electromagnetic field that is secondarily radiated therefrom is efficiently guided to the near-field antenna, and is then efficiently radiated into the space from there. Moreover, since the operating impedance of the magnetic field antenna is low, there is an advantage that it is difficult to be influenced by surrounding objects and human bodies.

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

(First embodiment)
The operation principle according to the first embodiment of the present invention will be described using the conceptual diagram of the low-power radio apparatus of FIG.

  In the present invention, first, the wireless tag 7 shown in FIG. 1 transmits an electromagnetic wave obtained by periodically oscillating a fundamental wave and modulating an ID code from the built-in antenna 7b, and the electric field component of the transmitted electromagnetic wave is dominant. Is done first. The energy is coupled to the electrostatic coupling type near field antenna 25 by electrostatic coupling, and is secondarily radiated from the electrostatic coupling type near field antenna 25 to the space as an electromagnetic field component. As a result, it is possible to obtain an effect of extending the reaching distance when the electromagnetic wave propagated through the space reaches the receiver 1 as compared with the case where the conventional wireless tag 7 is used alone.

  In addition, when the electric field antenna is adopted as the built-in antenna 7b as shown below, the electromagnetic wave is strong in the near-field region (Fresnel region), and the electric field component of the electromagnetic wave is strong in the far-field region (Fraunhofer region). The electric field component and the magnetic field component are propagated as equal electromagnetic waves. For this reason, since only the electric field is dominant in the near-field region, even when a magnetic field antenna is used as the near-field antenna, efficient electromagnetic field coupling is not performed.

  Therefore, the present invention is characterized in that an electric field antenna is used as a proximity antenna in order to efficiently radiate an electromagnetic wave transmitted from the built-in antenna 7b into the space and extend the reach distance when reaching the receiver 1 more effectively. .

  The relationship between the distance from the source of electromagnetic waves transmitted from the electric field antenna and the intensity of the electromagnetic waves is shown below.

If the amount of charge at a place P that is a distance r away from an electric dipole of length l at the origin of a certain space is q (t) (t is time), the rate of change in the amount of charge is current.

And can be expressed in the form of differentiation.
When there is a minute dipole oriented in the z-axis direction at the origin, the electric field E (t) and magnetic field H (t) of the minute dipole at point P shown in FIG.

It becomes. These equations are expressed based on polar coordinates, and e _r , e _θ , and e _ψ are e-direction, θ-direction, and ψ-direction unit vectors, respectively. C is the propagation speed of electromagnetic waves in space.
In these equations, the term proportional to r ⁻³ is a term that creates an electrostatic magnetic field, and in the case of an electric dipole, it exists only in the electric field.
The term r- ^{2 is} a term that generates an inductive electromagnetic field. The r ^-1 term is the term that creates the radiation field. If it is far enough, the electrostatic term and the induction term are much smaller than the radiation term. Therefore, the electric and magnetic fields (referred to as the far field) at a location sufficiently away from the dipole are

It becomes. Since the direction unit vectors are orthogonal, the electric field and the magnetic field are orthogonal in the far field, and there is no electric / magnetic field component in the wave traveling direction.
In the frequency domain display, the far-field electric and magnetic field components are

It becomes.
Here, the ratio ξ between the far-field electric field and the magnetic field is called wave impedance and is expressed by the following equation.

  From (Equation 6) and (Equation 7), in the near field region, the wave impedance ξ increases as the distance r to the wave source becomes shorter. Therefore, in the near field region (Fresnel region), the electric field component of the electromagnetic wave is strong and the far field. It can be said that the magnetic field component becomes stronger in the region (Fraunhofer region).

  FIG. 4 shows the configuration of the low-power radio apparatus according to the first embodiment of the present invention.

  FIG. 4A shows a receiver 1 that receives an electromagnetic wave arriving at an antenna and extracts an ID code modulated by the electromagnetic wave, and FIG. 4B shows a radio with an antenna seal 29 attached. FIG. 4C shows a cross-sectional view when the wireless tag 7 and the antenna seal 29 shown in FIG. 4B are cut along the AA line.

  As shown in FIG. 4C, the wireless tag 7 includes an electronic circuit board 7a including an integrated circuit element, an antenna 7b, and a battery 7c, and predetermined signal processing is performed by the integrated circuit element provided on the electronic circuit board 7a. And transmitting an electromagnetic wave obtained by periodically oscillating the fundamental wave and modulating the ID code via the antenna. The antenna seal 29 includes a seal layer 31 made of a plastic resin that is bonded to the case of the wireless tag 7 via an adhesive surface, a laminate layer 33 made of a plastic resin that is bonded to the other surface of the seal layer 31, and a seal. A flat-plate electrostatic coupling type near field antenna 25 housed between the layer 31 and the laminate layer 33 is provided.

  With the above-described configuration, the wireless tag 7 shown in FIG. 4 first transmits an electromagnetic wave in which the fundamental wave is periodically oscillated to modulate the ID code from the built-in antenna 7b, and the electric field component of the transmitted electromagnetic wave is dominant. First, it is energy-coupled by electrostatic coupling to the electrostatic coupling type near field antenna 25, and is secondarily radiated from the electrostatic coupling type near field antenna 25 to the space as an electromagnetic field component. As a result, it is possible to obtain an effect of extending the reaching distance when the electromagnetic wave propagated through the space reaches the receiver 1 as compared with the case where the conventional wireless tag 7 is used alone.

(Second Embodiment)
FIG. 5 shows the configuration of a low-power radio apparatus according to the second embodiment of the present invention. FIG. 5A shows a low-power wireless device including the wireless tag 7 to which the antenna seal 35 is attached. FIG. 5B shows the wireless tag 7 and the antenna seal 35 cut along a CC line. A sectional view of the case is shown.

   As shown in FIG. 5B, the antenna seal 35 includes a seal layer 37 made of a plastic resin, one side of which is bonded to the case of the wireless tag 7 via an adhesive surface, and the seal layer 37 and the case of the wireless tag 7. Is provided with a flat-plate electrostatic coupling type near field antenna 25 housed between the two.

  Next, the operation of the low-power radio apparatus will be described with reference to FIG.

  First, the wireless tag 7 transmits an electromagnetic wave obtained by periodically oscillating a fundamental wave and modulating an ID code from the antenna 7b. A seal layer 37 of an antenna seal 35 is bonded to the case of the wireless tag 7, and the electrostatic coupling type near field antenna 25 is housed inside the case, so that electromagnetic waves transmitted from the wireless tag 7 are electrostatically The electromagnetic field is induced in the coupling type near field antenna 25, and the electromagnetic field is radiated from the electrostatic coupling type near field antenna 25.

  As a result, the electromagnetic wave transmitted from the low-power wireless device in which the antenna seal 29 is bonded to the wireless tag 7 is radiated more efficiently into the space than when the wireless tag 7 is used alone as in the prior art. It is possible to extend the reach distance when the electromagnetic wave propagated through reaches the receiver 1.

(Third embodiment)
FIG. 6 shows the configuration of a low-power radio apparatus according to the third embodiment of the present invention. FIG. 6A shows a low-power wireless device including the wireless tag 7 provided with the antenna portion 41, and FIG. 6B shows a case where the wireless tag 7 and the antenna portion 41 are cut along the DD line. FIG.

  As shown in FIG. 6B, the antenna unit 41 includes a flat electrostatic coupling proximity electric field antenna 25 provided on the upper lid A of the case of the wireless tag 7 and the flat electrostatic coupling proximity. A varnish layer 43 applied to the upper surface of the electric field antenna 25 and a part of the upper pig A is provided.

  FIG. 7 shows a flowchart of a method for manufacturing the antenna unit 41.

  Next, with reference to FIG. 7, the manufacturing method of the antenna part 41 formed in the upper pig A is demonstrated.

  First, an upper lid A, an etching solution, an etching bag, and a masking sheet are prepared.

  In step S111, a pattern diagram of a flat conductor is drawn on a masking sheet, and unnecessary portions are cut to create a mask pattern. And this mask pattern is affixed and masked on the surface where the copper foil of the upper cover A was vapor-deposited. In step S113, the surface of the upper lid A on which the pattern is adhered is dipped in an etching solution, the copper thin film is removed from the surface excluding the portion where the pattern is adhered, and the upper lid A is washed.

  Next, in step S115, a flat conductor formed on the upper lid A is attached. In step S117, a high-frequency varnish is applied to the upper surface of the flat conductor formed on the upper lid A.

  As a result, the electrostatic coupling type near field antenna 25 is formed on the upper surface of the upper lid A.

  Next, the operation of the low-power radio apparatus will be described with reference to FIG.

  First, the wireless tag 7 transmits an electromagnetic wave obtained by periodically oscillating a fundamental wave and modulating an ID code. Since the electrostatic coupling type near field antenna 25 is adhered to the case of the wireless tag 7, electromagnetic waves transmitted from the wireless tag 7 are induced in the electrostatic coupling type near field antenna 25, and the electrostatic coupling type near field antenna The electromagnetic field is secondarily radiated from 25.

  As a result, the electromagnetic wave transmitted from the low-power wireless device in which the electrostatic coupling type near field antenna 25 is bonded to the wireless tag 7 is more efficiently radiated into the space than when the wireless tag 7 is used alone as in the prior art. Therefore, the reaching distance when the electromagnetic wave propagated through the space reaches the receiver 1 can be extended.

(Fourth embodiment)
FIG. 8 shows the configuration of a low-power radio apparatus according to the fourth embodiment of the present invention. FIG. 8A shows a card case 45 in which an antenna card 47 is inserted, and FIG. 8B shows a cross-sectional view when the antenna card 71 and the card case 77 are cut along line E-E. FIG. 8C shows that both the antenna card 47 and the wireless tag 7 are inserted into the card case 45, and FIG. 8D shows a card case 45 in which the antenna card 47 and the wireless tag 7 are inserted. Sectional drawing at the time of cutting along line FF is shown.

   As shown in FIG. 8B, the antenna card 47 includes a card-shaped card base 51 made of a transparent plastic resin, a capacitively coupled near-field antenna 25 adhered on the card base 51, A seal layer 49 is provided to cover and store the capacitively coupled near field antenna 25 formed on the card base 51.

  Next, the operation of the low-power radio apparatus will be described with reference to FIG.

  First, the wireless tag 7 transmits an electromagnetic wave obtained by periodically oscillating a fundamental wave and modulating an ID code. Since the electrostatic coupling type near field antenna 25 is adhered to the case of the wireless tag 7, electromagnetic waves transmitted from the wireless tag 7 are induced in the electrostatic coupling type near field antenna 25, and the electrostatic coupling type near field antenna The electromagnetic field is secondarily radiated from 25.

  As a result, the electromagnetic wave transmitted from the low-power wireless device in which the electrostatic coupling type near field antenna 25 is bonded to the wireless tag 7 is more efficiently radiated into the space than when the wireless tag 7 is used alone as in the prior art. Therefore, the reaching distance when the electromagnetic wave propagated through the space reaches the receiver 1 can be extended.

(Fifth embodiment)
FIG. 2 shows the configuration of a low-power radio apparatus according to the fifth embodiment of the present invention.

  In the present invention, in the first to fifth embodiments, a conductive wire 27 having a length that is an integral multiple of a quarter wavelength of an electromagnetic wave generated from a wireless tag is connected to the capacitively coupled near field antenna 25. is doing.

  Thereby, the electromagnetic wave transmitted from the low-power wireless device to which the electrostatic coupling type near field antenna 25 connected with the conducting wire 27 is bonded is more efficient than the electrostatic coupling type near field antenna 25 not connected with the conducting wire 27. Since the radiation is radiated into the space, the reachable distance when the electromagnetic wave propagated through the space reaches the receiver 1 can be extended.

(Sixth embodiment)
The operation principle according to the sixth embodiment of the present invention will be described using the conceptual diagram of the low-power radio apparatus of FIG.

  From the electric field antenna with a built-in tag shown in FIG. 3, radiation in which the electric field component of the electromagnetic field is dominant is first performed. It is coupled by electrostatic coupling to the electrostatic coupling proximity antenna 25 outside the tag, and energy is radiated from there to the space as an electromagnetic field component. Furthermore, the magnetic field component of the electromagnetic wave radiated with energy is coupled to the near magnetic field antenna 9 and re-radiated to the space as the magnetic field component.

  FIG. 9 shows the configuration of a low-power radio apparatus according to the sixth embodiment of the present invention.

  FIG. 9A shows a low-power wireless device including the wireless tag 7 to which the antenna seal 55 is attached, and FIG. 9C is a rear view to which the antenna seal 29 of the low-power wireless device is attached. FIG. 9B shows a cross-sectional view of the wireless tag 7, the antenna seal 29, and the antenna seal 55 shown in FIGS. 9A and 9B taken along line GG.

   As shown in FIG. 9B, the wireless tag 7 includes an electronic circuit board 7a including an integrated circuit element, an antenna 7b, and a battery 7c, and predetermined signal processing is performed by the integrated circuit element provided on the electronic circuit board 7a. And transmitting an electromagnetic wave obtained by periodically oscillating the fundamental wave and modulating the ID code via the antenna. The antenna seal 29 includes a seal layer 31 made of a plastic resin that is bonded to the case of the wireless tag 7 via an adhesive surface, a laminate layer 33 made of a plastic resin that is bonded to the other surface of the seal layer 31, and a seal. A flat-plate electrostatic coupling type near field antenna 25 housed between the layer 31 and the laminate layer 33 is provided.

  The antenna seal 55 includes a seal layer 56 made of a plastic resin that is bonded to the case of the wireless tag 7 via an adhesive surface, a laminate layer 57 made of a plastic resin that is bonded to the other surface of the seal layer 56, and a seal. A near magnetic field antenna 9 is provided between the layer 56 and the laminate layer 57.

  FIG. 10 shows the structure of the near magnetic field antenna 9 shown in FIG.

  The near magnetic field antenna 9 is formed of a closed loop in which capacitors 53 are connected to both ends of a circular or square conductor 54 whose entire circumference is 0.5 wavelength or less with respect to the wavelength of the electromagnetic wave transmitted from the wireless tag 7. Yes. With this structure, the near-field antenna 9 resonates with the transmitted electromagnetic wave, and the impedance of the closed loop formed by the conductor 54 and the capacitor 53 at the time of resonance becomes a very low value (generally, a few Ω). A current is induced, and a high-frequency current generates a strong magnetic field in the near field, so that efficient radiation is performed.

  As shown in FIG. 9, when the wireless tag 7 includes the electrostatic coupling type near field antenna 25 and the near field antenna 9, more efficient radiation is performed.

  The electric field antenna with a built-in tag first radiates the electric field component of the electromagnetic field. It is coupled by electrostatic coupling to the electrostatic coupling proximity antenna 25 outside the tag, and energy is radiated from there to the space as an electromagnetic field component. Furthermore, the magnetic field component of the electromagnetic wave radiated with energy is coupled to the near magnetic field antenna 9 and re-radiated to the space as the magnetic field component. At this time, that is, since the impedance of the closed loop formed by the conductor 54 and the capacitor 53 at the time of resonance becomes a very low value (generally, a few Ω), a large high-frequency current is induced, and this high-frequency current causes a near field. Efficient radiation.

  Further, since the impedance of the near magnetic field antenna 9 becomes extremely low, there is a feature that the impedance is not easily disturbed by a nearby object or a human body as compared with a case where only a general electric field type antenna having a high operating impedance is used. Therefore, it is possible to prevent weakening of electromagnetic waves transmitted due to the influence of an object or human body on which the low-power wireless device is mounted.

  As a result, despite one tag, electric field radiation is performed in two modes: high-impedance electric field radiation from the electric field coupling type near field antenna and low magnetic field radiation from the magnetic field coupling type near field antenna. The

  As a result, the electromagnetic wave transmitted from the low-power wireless device including the electrostatic coupling type near-field antenna 25 and the near-field antenna 9 can be used as an object or Even when worn on the human body, the radiation is efficiently radiated to the space, so that the reach distance when the electromagnetic wave propagated through the space reaches the receiver 1 can be extended.

Here, a quantitative numerical example of the near magnetic field antenna 9 shown in FIG. 9 will be described. Now, regarding the size of the conductor in the vicinity of the wireless tag 7, N is the number of turns of the loop conductor (times), W is the length of one side of the conductor (m) (assuming the shape is square), and a is the conductor. This inductance is defined by the following formula, where m is the radius (m) (assuming the conductor is linear) and μs is the relative permeability.

  In consideration of various wireless tag sizes to be applied to the actual system, the conductor size and the capacitance value of the capacitor may be determined by substituting appropriate values.

For example, in the case of a conductor structure having a size of L = about 40 (nH), if a capacitor of C = about 7 (PF) is connected,

If the operating frequency of the wireless tag is assumed to be about 300 MHz due to the relationship, the electromagnetic wave can be efficiently radiated to secondary radiation.

(Experimental result)
With reference to the diagram shown in FIG. 12, the electrolytic strength of the low-power radio apparatus according to the first to sixth embodiments will be described.

  Test 1 is a result of an experiment related to only a wireless tag as in the past, and Test 2 is a low-power wireless device according to the first to fifth embodiments, that is, a capacitively coupled near-field antenna is placed close to a wireless tag. The test 3 is a result of the experiment on the low-power wireless device, and test 3 is the low-power wireless device according to the sixth embodiment, that is, the low-power wireless device in which the capacitively coupled near-field antenna and the near-field antenna are close to the wireless tag. It is the experimental result about.

  In this experiment, as shown in FIG. 12, in test 1, a wireless tag is attached to a human body in test 2 to test 3, and the electric field strength at a location 3 m away from the wireless tag or the low power wireless device. The object of the present invention is to confirm the effect of the present invention.

  As shown in FIG. 12, the experimental result shows that the electric field strength measurement result in Test 1 is about 200 μV / m, the electric field strength measurement result in Test 2 is about 300 μV / m, and the electric field strength measurement result in Test 3 is According to the present invention, the electric field strength of the low-power wireless device in which the electrostatic coupling type near field antenna is close to the wireless tag is about 1.5 times the electric field strength of only the wireless tag, and the electrostatic coupling type near field. It was verified that the electric field strength of the low-power wireless device in which the antenna and the near magnetic field antenna are close to the wireless tag is improved to about twice that of the wireless tag alone.

(The invention's effect)
According to the present invention, even when a wireless tag in which the transmission power of electromagnetic waves is regulated is attached to an object or human body that absorbs and weakens electromagnetic waves, the electromagnetic waves radiated from the wireless tag are placed close to each other. The secondary radiation is efficiently radiated into the space by the coupled near-field antenna and / or near-field magnetic field antenna, so that the receivable distance should maintain the performance close to the ideal case where only the wireless tag is placed in free space. Can do.

  Moreover, since the near-field antenna has a very low operating impedance and is small, the impedance is disturbed by the nearest surrounding object or human body, and the distributed current on the antenna is not easily disturbed. Therefore, even when the near-field antenna is integrated with the wireless tag and attached to an object or human body, its performance is not easily deteriorated, especially when it is attached to the human body, and it can be touched by a human hand or put in a pocket. However, there is an advantage that it is not easily affected.

  In addition, when a very small electrostatic coupling type near-field antenna or / and near-field magnetic field antenna is placed close to the wireless tag, it is not physically or electrically connected to the internal circuit of the wireless tag, and the wireless tag is simply connected. Since it is only necessary to place it in the immediate vicinity, the low-power wireless device of the present invention can be realized very easily, and various targets can be used regardless of the shape, size, manufacturer, type, etc. of the target wireless tag. Can be applied to.

  In addition, the component of the electrostatic coupling type near-field antenna is only a conductor, and the component of the near-field antenna is only a conductor and a capacitor, and no active parts are required. It is extremely reliable, inexpensive, and economical.

  This capacitively coupled near-field antenna and / or near-field antenna is formed of a thin copper foil or other conductor, and the whole is made thin and compact in a seed shape, so that it can be easily attached to the surface of the RFID tag body case be able to. It can be easily processed in a shorter time, and the finished product is extremely simple.

  Furthermore, if this electrostatic coupling type near field antenna and / or near field antenna is mounted on the surface or inner surface of a card case or name tag case that is generally widely used, various types (however, electromagnetic field loop antennas) can be attached to this case. And the resonance frequency coincides with each other), it is very easy to construct a wireless tag system in which the reach of electromagnetic waves is unlikely to decrease due to the influence of a mounted object.

The operation principle according to the first embodiment of the present invention will be described. The principle of operation concerning the 5th embodiment of the present invention is shown. The principle of operation concerning the 6th embodiment of the present invention is shown. It is a figure which shows the structure of the low power radio | wireless apparatus which concerns on the 1st Embodiment of this invention, (a) shows the receiver 1, (b) consists of the radio | wireless tag 7 to which the antenna seal | sticker 29 was affixed. A low-power radio | wireless apparatus is shown, (c) shows sectional drawing of the radio | wireless tag 7 and the antenna seal | sticker 29 which are shown to (b). It is a figure which shows the structure of the low power radio | wireless apparatus which concerns on the 2nd Embodiment of this invention, (a) shows the low power radio | wireless apparatus which consists of the radio | wireless tag 7 to which the antenna seal 35 was affixed, (b) Shows a cross-sectional view of the wireless tag 7 and the antenna seal 21. It is a figure which shows the structure of the low power radio | wireless apparatus which concerns on the 3rd Embodiment of this invention, (a) shows the low power radio | wireless apparatus which consists of the radio | wireless tag 7 in which the antenna part 41 was provided, (b) Sectional drawing of the wireless tag 7 and the antenna part 41 is shown. The flowchart of the manufacturing method of the antenna part 41 shown in FIG. 6 is shown. It is a figure which shows the structure of the low power radio | wireless apparatus which concerns on the 4th Embodiment of this invention, (a) shows the card case 45 in which the antenna card 47 was inserted, (b) is the antenna card 47 and a card case. (C) shows that both the antenna card 47 and the wireless tag 7 are inserted into the card case 45, and (d) shows a cross-sectional view of the antenna card 47 and the wireless tag 7. . It is a figure which shows the structure of the low power radio | wireless apparatus which concerns on the 6th Embodiment of this invention, (a) shows the low power radio | wireless apparatus which consists of the radio | wireless tag 7 to which the antenna seal | sticker 55 was affixed, FIG. FIG. 9C shows a rear view where the antenna seal 29 of the low-power radio apparatus is attached, and FIG. 9B shows the radio tag 7 shown in FIGS. 9A and 9B, the antenna seal 29, and Sectional drawing at the time of cut | disconnecting the antenna seal | sticker 55 with a GG line is shown. The structure of the near magnetic field antenna 9 which concerns on the 6th Embodiment of this invention is shown. Each component of an electric field and a magnetic field is shown when q (t) (t is time) is the amount of charge at a location P separated from a length l electric dipole at the origin of a certain space by a distance r. The relationship between the form of a low power radio | wireless apparatus and the electrolysis intensity | strength in the point 3 m away from the low power radio | wireless apparatus at the time of mounting | wearing a human body with a low power radio | wireless apparatus is shown. FIG. 2 shows a conventional wireless tag system, in which (a) shows a receiver 1, (b) shows a wireless tag attached to a human body, and (c) shows a name tag case in which the wireless tag is inserted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Receiver 7 Radio | wireless tag 25 Electrostatic coupling type near field antenna 29,35 Antenna seal 41 Antenna part 45 Card case 47 Antenna card

Claims (10)

Proximate to a wireless tag containing an antenna for transmitting electromagnetic waves, and having a capacitively coupled near-field antenna installed to face one surface of the antenna,
Low-power wireless device characterized in that electric field component is dominantly radiated from the wireless tag, and energy is coupled to the electrostatic coupling type proximity antenna by electrostatic coupling by this radiation and energy is radiated to space as an electromagnetic field component. . The capacitively coupled near field antenna is
The low-power radio apparatus according to claim 1, wherein the low-power radio apparatus is formed of a flat conductor disposed so as to face one surface of an antenna built in the radio tag. The capacitively coupled near field antenna is
3. The low-power radio apparatus according to claim 2, wherein a pair of thin seals made of resin is attached to both sides of the conductor in a multilayer seal. The capacitively coupled near field antenna is
The low power according to claim 2, wherein a conductor is connected to one side surface of the case housing the wireless tag, and a thin seal made of resin is attached to the surface of the conductor. Wireless device. The capacitively coupled near field antenna is
3. The low-power radio apparatus according to claim 2, wherein a resin liquid is applied to the surface of the conductor and stored. While storing the wireless tag,
4. The low-power radio apparatus according to claim 3, further comprising a card case for storing a card made of a multi-layer seal storing the electrostatic coupling type near field antenna. Proximate to a wireless tag containing an antenna for transmitting electromagnetic waves, and having a capacitively coupled near-field antenna installed to face one surface of the antenna,
The capacitively coupled near field antenna is
Formed with a flat conductor,
Low-power wireless device characterized in that electric field component is dominantly radiated from the wireless tag, and energy is coupled to the electrostatic coupling type proximity antenna by electrostatic coupling by this radiation and energy is radiated to space as an electromagnetic field component. . The capacitively coupled near field antenna is
It is formed of a flat plate-like conductor installed so as to face the antenna built in the wireless tag, and has a lead wire having a length that is an integral multiple of a quarter wavelength of electromagnetic waves generated from the wireless tag. The low-power radio apparatus according to claim 1. Proximity to a wireless tag containing an antenna for transmitting electromagnetic waves, having a capacitively coupled near-field antenna installed to face the antenna,
Proximity magnetic field antenna close to the wireless tag and resonating at the frequency of the electromagnetic wave transmitted from the wireless tag,
Radiation in which an electric field component is dominant from the wireless tag is made, energy is coupled to the electrostatic coupling proximity antenna by electrostatic coupling by this radiation, and energy is radiated to space as an electromagnetic field component. Of the electromagnetic waves radiated The low-power radio apparatus is characterized in that the magnetic field component of the power is coupled to the near-field antenna and is secondarily radiated to the space as the magnetic field component. The near-field antenna is
10. The low power according to claim 9, wherein the entire power is formed from a closed loop formed by connecting capacitors to both ends of a conductor having a wavelength of 0.5 wavelength or less with respect to the wavelength of the electromagnetic wave transmitted from the wireless tag. Wireless device.

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