JP2011217204A - Planar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar antenna which can be configured in a small size and at low cost and can be operated in a plurality of frequency bands as an antenna of an apparatus related to RFID for instance.SOLUTION: The planar antenna includes: a dielectric substrate 12; a first loop conductor 14 which is formed on one plane of the dielectric substrate 12 and has a gap at a part; and a first linear conductor 16 which is formed inside the first loop conductor 14 and extends from a proximal end part separated from the first loop conductor to the end part inside a loop. Balanced feeding is performed between the proximal end part of the first linear conductor 16 and the first loop conductor 14, and the first loop conductor 14 configures the loop radiation element of the loop antenna of a first frequency.

Description

  The present invention relates to a planar antenna that can be configured to be small and inexpensive and can operate in a plurality of frequency bands, for example, as an antenna of an RFID-related device.

  In recent years, technologies using non-contact IC cards, wireless IC tags, etc. have been actively used. For example, as security applications, they are increasingly used in entrance / exit management, office security management, etc. Applications of built-in RFID reader / writer devices are expanding.

  Known antennas for RFID reader / writer devices include a 13.56 MHz HF band print loop coil, a 950 MHz band resonant dipole antenna, and a 2.45 GHz patch antenna.

  Conventionally, it has been used as a separate device for each band, but a reader / writer device that integrates these devices is indispensable, so it can operate in multiple frequency bands, and is small and inexpensive. The practical application of an integrated planar antenna is desired.

  As a conventional planar ring antenna, for example, an antenna described in Patent Document 1 is known.

  In the one described in Patent Document 1, a coiled antenna section for 13.56 MHz and two L-shaped conductors formed at predetermined intervals so as to surround the antenna section on the base substrate. The 2.45 GHz antenna section and the 950 MHz antenna section including two conductors formed at a predetermined interval outside the 2.45 GHz antenna section are formed.

JP 2005-252853 A

  An object of the present invention is to provide a planar loop antenna having a novel configuration that is small and can be configured at low cost and that can operate at a desired frequency of one frequency or more.

In order to achieve the above object, a planar antenna according to the first aspect of the present invention comprises:
A dielectric substrate;
A first loop conductor formed on one plane of the dielectric substrate and having a gap in part;
A first linear conductor formed within the first loop conductor and extending from a proximal end spaced close to the first loop conductor to a distal end within the loop approaching the gap;
And a balanced feeding is performed between the base end of the first linear conductor and the first loop conductor, and the first loop conductor constitutes a loop radiating element of a loop antenna having a first frequency. .

  According to a second aspect of the present invention, in the planar antenna according to the first aspect, the first linear conductor constitutes a radiating element of a monopole antenna that operates at a second frequency different from the first frequency. .

  A third aspect of the present invention is the planar antenna according to the first or second aspect, wherein the coil is formed on the other surface of the dielectric substrate and operates in a frequency band different from that of the antenna and performs transmission by electromagnetic induction. A shaped conductor is formed.

  According to a fourth aspect of the present invention, there is provided the planar antenna according to the first or second aspect, wherein the planar antenna is formed on the other surface of the dielectric substrate, has a second gap in part, and is electrically connected to the first loop conductor. It further comprises a two-loop conductor.

  According to a fifth aspect of the present invention, in the planar antenna according to the fourth aspect of the present invention, the planar antenna is disposed between the first loop conductor and the second loop conductor, operates in a frequency band different from the antenna, and uses an electromagnetic induction method. It further comprises a coiled conductor that performs transmission.

  According to a sixth aspect of the present invention, in the planar antenna according to the fifth aspect, the loop is formed inside the second loop conductor and approaches the second gap from a proximal end portion that is spaced close to the second loop conductor. It further has the 2nd straight conductor extended to an internal terminal part, It is characterized by the above-mentioned.

  According to a seventh aspect of the present invention, in the planar antenna according to the sixth aspect, balanced feeding is performed between the base end portion of the second straight conductor and the second loop conductor, and the first loop conductor is a loop having a first frequency. A loop radiating element of the antenna is configured, and the second linear conductor is configured as a monopole radiating element that operates at a second frequency different from the first frequency.

  According to an eighth aspect of the present invention, in the planar antenna according to any one of the first to seventh aspects, a metal reflector is disposed substantially parallel to the dielectric substrate with a predetermined distance apart. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, the planar antenna which can be comprised small and cheaply is realizable. In addition, the first loop conductor constitutes a loop radiating element of a loop antenna, and the linear conductor is constituted as a radiating element of a monopole antenna, whereby an antenna that operates at two frequencies can be configured. Furthermore, by providing a coiled conductor that performs transmission by electromagnetic induction, it can be configured as an antenna that operates at two or more frequencies. By sandwiching the coiled conductor between the first loop conductor and the second loop conductor, electrostatic shielding can be performed on the electromagnetic induction type coiled conductor when the first loop conductor and the second loop conductor are grounded. it can. Therefore, even when the electric power of the coiled conductor is increased, the electric field in the distance can be attenuated, and the influence of the electric field by the coiled conductor on the surroundings can be reduced.

  In addition, the planar antenna of the present invention can be used as an antenna for RFID-related devices as an antenna that operates at a frequency of 13.56 MHz, 950 MHz, or a UHF band in the vicinity thereof, 2.45 GHz.

1 is an exploded perspective view of a planar antenna according to a first embodiment of the present invention. It is a top view of a 1st embodiment. It is a side view of a 1st embodiment. In 1st Embodiment, it is a simulation result of the return loss characteristic of 950 MHz vicinity when a 1st frequency is 950 MHz. It is a disassembled perspective view of the modification of 1st Embodiment (The dielectric substrate is abbreviate | omitting illustration). It is a side view of the modification of 1st Embodiment. It is a block diagram of the planar antenna which concerns on 2nd Embodiment of this invention. In 2nd Embodiment, it is a simulation result of the return loss characteristic from 800 MHz to 3 GHz when the 1st frequency is 950 MHz and the 2nd frequency is 2.45 GHz. It is a disassembled perspective view of the planar antenna which concerns on 3rd Embodiment (The dielectric substrate is abbreviate | omitting illustration). It is a side view of 3rd Embodiment. It is a disassembled perspective view of the modification of 3rd Embodiment (The dielectric substrate is abbreviate | omitting illustration). It is a side view of the modification of 3rd Embodiment and 5th Embodiment. It is a block diagram of the modification of 3rd Embodiment. It is a side view showing the further modification of 3rd Embodiment. It is the top view of the modification of FIG. 13A, the top view of the one part component, and a side view. It is a block diagram of the planar antenna which concerns on 4th Embodiment. It is a block diagram of the planar antenna which concerns on the modification of 4th Embodiment. It is a disassembled perspective view of the planar antenna which concerns on 5th Embodiment of this invention (The dielectric material board is abbreviate | omitting illustration). It is a top view of a 5th embodiment. It is a side view of 5th Embodiment. It is a block diagram of a 5th embodiment. It is a disassembled perspective view of the modification of 5th Embodiment (The dielectric substrate is abbreviate | omitting illustration). It is a block diagram of the modification of 5th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
1 to 3 show a planar antenna according to a first embodiment of the present invention. In the figure, the planar antenna 10 has a first loop conductor 14 formed on one surface of a dielectric substrate 12 and a first straight conductor 16 formed in the first loop conductor 14.

  Specifically, the first loop conductor 14 includes a first horizontal side portion 14A (length L1, width W) and a first vertical side portion 14B (length L2, L2) orthogonal to the first horizontal side portion 14A. Width W) and second vertical side portion 14C (length L2, width W), and second horizontal side portion orthogonal to the first vertical side portion 14B and second vertical side portion 14C and parallel to the first horizontal side portion 14A. It consists of a rectangular loop radiating element consisting of 14D (length L1, width W), and is formed by copper foil etching. The aspect ratio of length and width is preferably about 2.0 (1.5 to 2.5).

  A gap 15 (distance d) is formed in the central portion of the second lateral side portion 14D. Therefore, the second lateral side portion 14D includes the first portion 14D1 (length L3, width W) and the second portion. It is further divided into a portion 14D2 (length L4, width W). The length L1 + 2L2 + L3 + L4 corresponds to one wavelength of the wavelength λg1 in consideration of the wavelength shortening rate due to the dielectric constant of the dielectric substrate 12 with respect to the wavelength λ1 of the first frequency (for example, 950 MHz).

  From the vicinity of the center of the first horizontal side portion 14A, the first straight conductor 16 (width a, length b) extends toward the inside of the loop (distance c from the first vertical side portion 14B). The end portion of the straight conductor 16 is directed toward the gap 15. However, the lateral position of the gap 15 and the lateral position of the first straight conductor 16 do not have to be exactly the same. Further, the base end portion of the first straight conductor 16 is a tapered portion 16a that becomes narrower toward the first lateral side portion 14A.

  Further, the metal reflector 20 is arranged in parallel with the dielectric substrate 12 so as to be separated from the dielectric substrate 12. This distance h1 is preferably about 0.1λ1.

  Power is fed through a balun and a matching circuit between the proximal end portion of the first straight conductor 16 and the substantially central portion of the first lateral side portion 14A.

  In the planar antenna 10 configured as described above, by performing balanced feeding at the first frequency, the first loop conductor 14 corresponds to one wavelength thereof, and thus operates as a loop radiating element of the loop antenna. A linearly polarized wave of frequency can be emitted.

  FIG. 4 shows the simulation result of the return loss characteristic around 950 MHz when the first frequency is 950 MHz. Various parameters at this time are as follows: L1 = 104 mm, L2 = 57 mm, L3 = L4 = 48.5 mm, W = 8 mm, gap 15 interval d = 7 mm, a = 12.5 mm, c = L1 / 2 = 28.5 mm The thickness h of the dielectric substrate 12 is 1.6 mm, the dielectric constant of the dielectric substrate 12 is 4.6, and the dimension b is changed.

  It can be seen from FIG. 4 that resonance characteristics at 950 MHz can be obtained, and that the resonance frequency can be adjusted by changing the dimension of b. It was also confirmed that the measured data was almost the same as the simulation data.

  In the first embodiment, as shown in FIGS. 5 and 6, a coiled conductor 34 for the HF band (13.56 MHz) is provided on the other surface of the dielectric substrate 12, so that the frequency at 13.56 MHz is obtained. Transmission by an electromagnetic induction method can be performed, and an antenna compatible with two frequencies can be obtained. In addition, since the influence of the radiation efficiency due to the dielectric loss is small, the dielectric substrate 12 can be realized in a low grade such as FR-4, and an inexpensive and small antenna can be obtained. Then, it can be used as an RFID-related device that operates at a frequency of 950 MHz or in the vicinity of the UHF band, for example, as a reader-side antenna, or as a tag-side or card-side antenna in combination with an IC chip.

(Second Embodiment)
FIG. 7 shows a planar antenna according to the second embodiment. In the second embodiment, the configuration is substantially the same as that of the first embodiment, but the length b of the first straight conductor 16 is set to be dielectric with respect to the wavelength λ2 of the second frequency (for example, 2.45 GHz). This is equivalent to a quarter wavelength of the wavelength λg2 considering the wavelength shortening rate due to the dielectric constant of the body substrate 12. Accordingly, the first straight conductor 16 operates as a radiating element of the monopole antenna with respect to the second frequency, and the first loop conductor 14 operates as a ground plate of the monopole antenna.

  Power is supplied to the first frequency balun and matching circuit 30 and the second frequency balun and matching circuit 32 via a switch (high frequency switch) 38.

  FIG. 8 shows a simulation result of the return loss characteristic from 800 MHz to 3 GHz when the length b of the first straight conductor 16 is variously changed. The conditions of dimensions other than b are the same as the conditions of FIG.

  From this figure, it can be seen that resonance characteristics are observed in the vicinity of 950 MHz and 2.45 GHz due to changes in b. Therefore, by appropriately adjusting the value of b, a two-frequency antenna can be obtained. As another parameter, when L1 is changed by 3 mm, the resonance frequency near 950 MHz is changed by 2.6%, and when h is changed by 0.8 mm, the resonance frequency near 950 MHz is changed by 4.2% and 2.45 GHz. The nearby resonant frequency changes by 2.2%. When the dielectric constant is changed between 3.8 and 4.8, the resonance frequency near 950 MHz is changed by 3.2%, and the resonance frequency near 2.45 GHz is changed by 2.0%.

  By finely adjusting the parameters, resonance conditions suitable for both the first frequency and the second frequency can be satisfied. In general, the longer the length of the first straight conductor 16 is, the better the return loss at the first frequency, and the shorter the length, the better the return loss at the second frequency. The length of the first straight conductor 16 may be set.

  Thus, the same effect as that of the first embodiment can be obtained, and a dual-frequency antenna can be obtained.

  In the second embodiment, a coil for the HF band (13.56 MHz) is provided on the other surface of the dielectric substrate 12 (see FIGS. 5 and 6), and transmission by an electromagnetic induction method at 13.56 MHz. And an antenna compatible with three frequencies can be obtained.

(Third embodiment)
9 to 10 show a planar antenna according to the third embodiment. In this example, the first loop conductor 14 and the first linear conductor 16 are formed on one surface of the dielectric substrate 12 as in the first embodiment, and the second surface of the dielectric substrate 12 is second on the other surface. A loop conductor 24 is formed.

  The second loop conductor 24 is configured in the same manner as the first loop conductor 14, and specifically, the first horizontal side 24A, the first vertical side 24B orthogonal to the first horizontal side 24A, and the first A rectangular loop radiating element comprising two vertical side portions 24C and a second horizontal side portion 24D orthogonal to the first vertical side portion 24B and the second vertical side portion 24C and parallel to the first horizontal side portion 24A; Formed from foil etching. A gap 25 is formed in the central portion of the second horizontal side portion 24D, and is divided into a first portion 24D1 and a second portion 24D2. The length and width of each part are preferably the same as those of the first loop conductor 14.

  The first loop conductor 14 and the second loop conductor 24 are electrically connected to each other when the first lateral side portion 14A and the first lateral side portion 24A are connected by the connection conductor 28 that penetrates the dielectric substrate 12. Yes.

  Also in this embodiment, since the second loop conductor 24 operates in the same manner as the first loop conductor 14, the second loop conductor 24 can be operated similarly to the first embodiment.

  Further, as shown in FIGS. 11 and 12, a coiled conductor 34 for the HF band (13.56 MHz) is embedded between the first loop conductor 14 and the second loop conductor 24 in the dielectric substrate 12. Can be made. In this case, as shown in FIG. 13, transmission by the electromagnetic induction method at 13.56 MHz can be performed by feeding power to the coiled conductor 34 from the transmission / reception circuit 36.

  The coiled conductor 34 is sandwiched between the first loop conductor 14 and the second loop conductor 24, and when the first loop conductor 14 and the second loop conductor 24 are grounded, the coiled conductor 34 is electrostatically charged. Can be shielded. Therefore, even when the electric power of the coiled conductor 34 is increased, a distant electric field can be attenuated within the radio wave regulation value, and the influence of the electric field on the surroundings can be reduced. The magnetic field generated by the coiled conductor 34 can be generated outside without being attenuated by providing the gaps 15 and 25 in the first loop conductor 14 and the second loop conductor 24.

  Regarding the mutual influences of the radio wave system using the first loop conductor 14 and the electromagnetic induction system using the coiled conductor 34, the coiled conductor 34 operates in a magnetic field, and hence the electric field of the surrounding radio wave system. There is little influence, and there is not much fluctuation of the resonance frequency. On the other hand, the radio wave system is affected by the coiled conductor 34, and the resonance frequency may shift and the radiation pattern may also change. However, as shown in FIG. 13, the first frequency transmission / reception circuit 31 connected to the first loop conductor 14 and the first straight conductor 16 and the electromagnetic induction transmission / reception circuit 36 connected to the coiled conductor 34. By separating the grounds from each other and insulating them, the influence on the radiation pattern at the first frequency can be eliminated. For the deviation of the resonance frequency, the lengths of the first loop conductor 14 and the second loop conductor 24 (particularly the length L1 of the first lateral sides 14A and 24A, which is the length in the longitudinal direction of the rectangular loop), the dielectric By adjusting the dielectric constant and the substrate thickness of the body substrate 12, it is possible to adjust the resonance frequency at the first frequency.

  Further, as shown in FIGS. 13A and 13B, a transmission spiral coil 42 of 13.56 MHz is provided between the dielectric substrate 12 and the reflection plate 20, and the coiled conductor 34 is supplied with non-contact power, so that the radio wave system It is also possible not to affect the antenna. The capacitor C is connected to the coiled conductor 34, and the resonance state (f = 1 / 2π√LC = 13.56 MHz) is established by the inductance L and the capacitor C due to the coiled conductor, whereby 13.56 MHz from the spiral coil 42 is obtained. The transmission induced power is amplified by magnetic resonance and multiplied by Q, and a magnetic field proportional to the current is generated from the coiled conductor 34.

  Thus, in addition to the effects of the previous embodiment, by providing the coiled conductor 34, a two-frequency antenna can be obtained.

(Fourth embodiment)
FIG. 14 shows a planar antenna according to the fourth embodiment. In the fourth embodiment, the configuration is almost the same as that of the third embodiment, but the length b of the first straight conductor 16 is set to be dielectric with respect to the wavelength λ2 of the second frequency (eg, 2.45 GHz). This is equivalent to a quarter wavelength of the wavelength λg2 considering the wavelength shortening rate due to the dielectric constant of the body substrate 12. Accordingly, the first straight conductor 16 operates as a radiating element of the monopole antenna with respect to the second frequency.

  Power is supplied to the first frequency balun and matching circuit 30 and the second frequency balun and matching circuit 32 via a switch (high frequency switch) 38.

  As a result, in the fourth embodiment, an antenna compatible with two frequencies can be obtained, and adjustment thereof is facilitated.

  That is, the first loop conductor 14 is set to a length and a position that are suitable for resonance at the first frequency, and the first loop conductor 14 operates as a loop radiating element at the first frequency (for example, 950 MHz). The conductor 16 is set to a length and a position that are exclusively suitable for resonance at the second frequency (eg, 2.45 GHz), and the second linear conductor 26 operates as a monopole radiating element at the second frequency.

  As a result, in addition to the effects of the previous embodiment, a dual-frequency antenna can be obtained. By finely adjusting the first loop conductor 14 and the first linear conductor 16 individually, fine adjustment suitable for the first frequency and the second frequency to be resonated can be performed.

  Further, a coiled conductor 34 for the HF band (13.56 MHz) can be embedded between the first loop conductor 14 and the second loop conductor 24 in the dielectric substrate 12. In this case, as shown in FIG. 15, power is supplied to the coiled conductor 34, the transmission / reception circuit 31 for the first frequency and the transmission / reception circuit 33 for the second frequency, and the HF band (13.56 MHz). For this reason, the ground for the transmission / reception circuit 36 is separated and insulated from each other, thereby eliminating the influence on the radiation pattern at the first frequency. For the deviation of the resonance frequency, the lengths of the first loop conductor 14 and the second loop conductor 24 (particularly the length L1 of the first lateral sides 14A and 24A, which is the length in the longitudinal direction of the rectangular loop), the dielectric By adjusting the dielectric constant and the substrate thickness of the body substrate 12, it is possible to adjust the resonance frequency at the first frequency.

Similarly to the one shown in FIGS. 13A and 13B, a transmission spiral coil 42 of 13.56 MHz is provided between the dielectric substrate 12 and the reflection plate 20, and non-contact power feeding is performed on the coiled conductor 34. It is also possible not to affect the radio wave antenna. The capacitor C is connected to the coiled conductor 34, and the resonance state (f = 1 / 2π√LC = 13.56 MHz) is established by the inductance L and the capacitor C due to the coiled conductor, whereby 13.56 MHz from the spiral coil 42 is obtained. The transmission induced power is amplified by magnetic resonance and multiplied by Q, and a magnetic field proportional to the current is generated from the coiled conductor 34.
In this way, in addition to the effects of the previous embodiment, a three-frequency antenna can be obtained.

(Fifth embodiment)
16 to 19 are planar antennas according to the fifth embodiment. In the fifth embodiment, a second linear conductor 26 is further formed in the second loop conductor 24 compared to the third embodiment.

  That is, from the vicinity of the center of the first lateral side 24A of the second loop conductor 24, the first straight conductor 26 extends toward the inside of the loop, and the end of the second straight conductor 26 extends in the direction of the gap 25. Heading to However, the lateral position of the gap 25 and the lateral position of the second straight conductor 26 do not have to be exactly the same. The base end portion of the second straight conductor 26 is a tapered portion 26a that becomes narrower toward the first lateral side portion 24A.

  As shown in FIG. 19, balanced feeding is performed between the base end portion of the first straight conductor 16 and the substantially central portion of the first lateral side portion 14A via the balun and the matching circuit 30, as shown in FIG. Via the balun and matching circuit 32, balanced power feeding is performed between the proximal end portion of the second straight conductor 26 and the substantially central portion of the first lateral side portion 24A. The balun and matching circuit 30 supplies power at the first frequency, and the balun and matching circuit 32 supplies power at the second frequency.

  The first straight conductor 16 is set to a length and position that are suitable for resonance at the first frequency, and the first loop conductor 14 operates as a loop radiating element at the first frequency (for example, 950 MHz). The conductor 26 is set to a length and a position that are exclusively suitable for resonance at the second frequency (eg, 2.45 GHz), and the second straight conductor 26 operates as a monopole radiating element at the second frequency.

  Alternatively, the first straight conductor 16 is set to a length and a position that are suitable for resonance at the first frequency, and the first loop conductor 14 operates as a loop radiating element at the first frequency (for example, 950 MHz). The conductor 26 may be set to a length and a position that are exclusively suitable for resonance at the second frequency (for example, 915 MHz), and the second loop conductor 24 may operate as a loop radiating element at the second frequency.

  As a result, in addition to the effects of the previous embodiment, a dual-frequency antenna can be obtained. By finely adjusting the first linear conductor 16 and the second linear conductor 26 individually, fine adjustment suitable for the first frequency and the second frequency to be resonated can be performed.

  Further, as shown in FIGS. 20 and 12, a coiled conductor 34 for the HF band (13.56 MHz) is embedded between the first loop conductor 14 and the second loop conductor 24 in the dielectric substrate 12. Can be done. In this case, as shown in FIG. 21, by feeding power to the coiled conductor 34, transmission by an electromagnetic induction method at 13.56 MHz can be performed, and an antenna compatible with three frequencies can be obtained.

  Similarly to the one shown in FIGS. 13A and 13B, a transmission spiral coil 42 of 13.56 MHz is provided between the dielectric substrate 12 and the reflection plate 20, and non-contact power feeding is performed on the coiled conductor 34. It is also possible not to affect the radio wave antenna. The capacitor C is connected to the coiled conductor 34, and the resonance state (f = 1 / 2π√LC = 13.56 MHz) is established by the inductance L and the capacitor C due to the coiled conductor, whereby 13.56 MHz from the spiral coil 42 is obtained. The transmission induced power is amplified by magnetic resonance and multiplied by Q, and a magnetic field proportional to the current is generated from the coiled conductor 34.

  In each of the above embodiments, the metal reflector 20 is provided. However, the metal reflector 20 can be omitted. The resonance frequency of the first frequency fluctuates depending on the presence or absence of the metal reflector 20, and the gain is increased in comparison with the case where the metal reflector 20 is present, so that adjustment can be made depending on whether or not the metal reflector 20 is present. It is.

DESCRIPTION OF SYMBOLS 10 Planar antenna 12 Dielectric board | substrate 14 1st loop conductor 15 Gap 16 1st linear conductor 20 Metal reflector 24 2nd loop conductor 25 Gap 26 2nd linear conductor 34 Coiled conductor

Claims (8)

A dielectric substrate;
A first loop conductor formed on one plane of the dielectric substrate and having a gap in part;
A first linear conductor formed within the first loop conductor and extending from a proximal end spaced close to the first loop conductor to a distal end within the loop approaching the gap;
And a balanced feeding is performed between the base end of the first linear conductor and the first loop conductor, and the first loop conductor constitutes a loop radiating element of a loop antenna having a first frequency. Planar antenna.   The planar antenna according to claim 1, wherein the first linear conductor constitutes a radiating element of a monopole antenna that operates at a second frequency different from the first frequency.   The coiled conductor formed on the other surface of the dielectric substrate and operating in a frequency band different from that of the antenna and performing transmission by an electromagnetic induction method is formed. Planar antenna.   The first loop conductor according to claim 1, further comprising a second loop conductor formed on the other surface of the dielectric substrate, having a second gap in a part thereof, and being electrically connected to the first loop conductor. Planar antenna.   The coil-shaped conductor which is arrange | positioned between the said 1st loop conductor and the said 2nd loop conductor, operate | moves in the frequency band different from the said antenna, and performs transmission by an electromagnetic induction system, It is characterized by the above-mentioned. 4. The planar antenna according to 4.   And a second linear conductor formed inside the second loop conductor and extending from a proximal end portion adjacent to and spaced apart from the second loop conductor to a distal end portion inside the loop approaching the second gap. The planar antenna according to claim 5.   Balance feed is performed between the base end portion of the second linear conductor and the second loop conductor, the first loop conductor constitutes a loop radiating element of the loop antenna of the first frequency, and the second linear conductor is the first. The planar antenna according to claim 6, comprising a monopole radiating element that operates at a second frequency different from the frequency.   The planar antenna according to any one of claims 1 to 7, wherein a metal reflector is disposed substantially parallel to the dielectric substrate at a predetermined distance from the dielectric substrate.