JP2012178741A - Multiband antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiband antenna capable of transmitting and receiving radio waves at multi-frequencies and with a wide band.SOLUTION: A multiband antenna dealing with transmission and reception waves at multi-frequencies and with a wide band includes a shank connected to a single feeding part and common to a lower frequency band and a higher frequency band, and a feeding element for the lower frequency band and a feeding element for the higher frequency band branched out from the shank using a frequency band as a unit. The feeding element for the lower frequency band and the feeding element for the higher frequency band are antenna elements having asymmetrical structure. By the above structure, a frequency in the lower frequency band is handled by distributing current in the shank and the feeding element for the lower frequency band, and a frequency in the higher frequency band is handled by distributing current in the shank and the feeding element for the higher frequency band. Thus, the multiband antenna deals with transmission and reception of radio waves at multi-frequencies and with a wide band.

Description

  The present invention relates to a multiband antenna corresponding to transmission / reception of a multi-frequency broadband.

  Recently, LTE (Long Term Evolution) has been put into practical use as a further evolution of the high-speed data communication standard “HSDPA” of the third generation mobile phone system “W-CDMA”, which is one of the high-speed data communication specifications of mobile phones. Is underway. The LTE is aimed at realizing high-speed communication of 100 Mbps or higher / 50 Mbps or higher, and is being standardized by a W-CDMA standardization organization.

  LTE introduced the 4th generation mobile communication (4G) candidate technology that prevents the increase of mutual interference due to the generation of multipath due to the broadband, and smoothly transitioned to the 4th generation mobile communication. Is also possible and is called 3.9G. Note that G represents the generation.

  4th generation mobile communication is intended to build the same type of mobile phone as the foundation of the ultimate 4th generation mobile phone in Japan, the United States, Europe and Southeast Asia, but it also uses communication of previous generations together. Therefore, one antenna is required to cover, for example, 700 to 960 MHz in the low frequency band and 1420 to 2700 MHz in the high frequency band.

  The present inventors have developed an antenna that forms the basis of a multiband antenna that can meet the above requirements (Patent Document 1). The multiband antenna assumes that the wavelength of the radio wave is λ, and that orthogonal coordinates XX ′ and YY ′ are assumed. (A) It is substantially rectangular and the length of each side is less than λ / 4. A flat antenna element is configured, and the rectangular sides are arranged in the X and Y directions on the Y side of the ground plate having an edge in the XX ′ direction, and (b) Y of the flat antenna element. A flat parasitic element having a basic portion partially opposed to a side in the −Y ′ direction is disposed, and (c) an extension extending in the X direction from the basic portion of the flat parasitic element is integrally formed Forming an enlarged flat parasitic element, and (d) an extension of the enlarged flat parasitic element facing the X-direction side of the flat antenna element in the YY ′ direction. Is building.

JP 2007-82037 A JP 2008-17047 A JP 2004-207992 A

  The multiband antenna is an ultra-small and ultra-thin antenna that resonates in the GHz band, that is, is intended for the GHz band, and therefore cannot transmit and receive in the 750 MHz band on the low frequency side. was there.

  When the transmission / reception band by the multiband antenna is shifted to near 750 MHz on the low frequency side, the electrical length of the antenna element increases accordingly. Therefore, if processing for the increased electrical length is not performed, the size and thickness can be reduced. There was a problem that it could not be realized.

  Patent Document 2 discloses a multi-antenna having a parasitic element. However, it is necessary to provide a feeding point, that is, a feeding circuit, for each frequency band supported by the multi-antenna, so that the size and thickness can be reduced. There was a limit.

  Patent Document 3 discloses a low reflection loss T-type antenna. The low reflection loss T-type antenna runs horizontally with a certain distance from the horizontal conductor below the horizontal plane including the horizontal conductor of the T-type antenna, and the distance from the vertical conductor of the T-type antenna becomes a predetermined distance. One or a plurality of parasitic L-type elements that vertically bend downward from the position and reach the ground plane are provided. By doing so, a current flows through the parasitic L-type elements due to induction from the T-type antenna, Since it will radiate | emit to space from now on, it is the structure that reflection to a feeding point decreases.

  However, as is apparent from FIG. 1 of the publication, the low reflection loss T-type antenna disclosed in Patent Document 3 has a configuration in which the electrical lengths of the left and right horizontal conductors are equal to 0.15λ, and the so-called dipole structure antenna element Therefore, the low reflection loss T-type antenna can not cope with only a single frequency, and cannot correspond to different frequencies between the left horizontal conductor and the right horizontal conductor.

  Furthermore, the low reflection loss T-type antenna disclosed in Patent Document 3 has a configuration in which the electrical lengths of the left and right parasitic elements are equal, as is apparent from FIGS. 3B and 4B of the publication, The left and right parasitic elements in the low reflection loss T-type antenna can only support a single frequency, and the left parasitic element and the right parasitic element cannot correspond to different frequencies. Is.

  As described above, LTE (Long Term Evolution) is a further evolution of the high-speed data communication standard “HSDPA” of the third-generation mobile phone system “W-CDMA”, which is one of the high-speed data communication specifications of mobile phones. However, the antennas disclosed in any of the patent documents can only be used with a single frequency, can handle multi-frequency broadband transmission and reception, and can be made smaller and thinner. There is a demand for an antenna to be realized.

  An object of the present invention is to provide a multi-band antenna that is compatible with multi-frequency wide-band transmission and reception and that is small and thin.

  In order to achieve the above object, a multiband antenna according to the present invention is a multiband antenna corresponding to a transmission / reception wave of a multi-frequency broadband and is common to a low frequency band and a high frequency band connected to a single power feeding unit. A low frequency band feeding element and a high frequency band feeding element branched from the shaft part in units of frequency bands, the low frequency band feeding element and the high frequency band feeding element, Is an antenna element having an asymmetric structure.

As described above, according to the present invention, by distributing the current to the shaft portion and the low frequency band feeding element, the current is applied to the shaft portion and the high frequency band feeding element so as to correspond to the low frequency band frequency. By distributing it, it is possible to correspond to a frequency in a high frequency band, and it is possible to cope with transmission / reception of a multi-frequency broadband.
Further, the antenna element has a structure approximating a planar structure by branching a low-frequency band feeding element and a high-frequency band feeding element from the shaft portion in units of frequency bands, and the low-frequency band feeding element And the high frequency band feeding element have an asymmetric structure, thereby shortening the dimension in the height direction along the shaft portion and the dimension in the direction in which the feeding element is branched, thereby reducing the size and thickness. It can be realized.

It is a surface view which shows the multiband antenna which concerns on Embodiment 1 of this invention. It is a back view which shows the multiband antenna which concerns on Embodiment 1 of this invention. It is sectional drawing which follows the XX line of FIG. It is the characteristic view which simulated the current distribution in 700 MHz of the low frequency band in the multiband antenna which concerns on Embodiment 1 of this invention. It is the characteristic view which simulated the current distribution in 960 MHz of the low frequency band in the multiband antenna which concerns on Embodiment 1 of this invention. It is the characteristic view which simulated the current distribution in 1420 MHz of the high frequency band in the multiband antenna which concerns on Embodiment 1 of this invention. It is the characteristic view which simulated the current distribution in 2700 MHz of the high frequency band in the multiband antenna which concerns on Embodiment 1 of this invention. It is the characteristic view which measured the relationship between a frequency and VSWR using the multiband antenna which concerns on Embodiment 1 of this invention. It is a surface view which shows the multiband antenna which concerns on Embodiment 2 of this invention. It is a back view which shows the multiband antenna which concerns on Embodiment 2 of this invention. It is the characteristic view which measured the relationship between a frequency and VSWR using the multiband antenna which concerns on Embodiment 2 of this invention. (A) is a surface figure which shows the multiband antenna which concerns on embodiment of this invention, (b) is a characteristic view which shows the relationship with frequency-VSWR measured using the multiband antenna shown to (a). . (A) is a surface view showing a modified example of the multiband antenna according to the embodiment of the present invention, (b) is a characteristic showing a relationship with the frequency -VSWR measured using the multiband antenna shown in (a). FIG. (A) is a surface view showing a modified example of the multiband antenna according to the embodiment of the present invention, (b) is a characteristic showing a relationship with the frequency -VSWR measured using the multiband antenna shown in (a). FIG. (A) is a front view which shows the example of a change of the multiband antenna which concerns on embodiment of this invention, (b) is the back view.

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

(Embodiment 1)
The multiband antenna according to the first embodiment of the present invention is intended for a multiband antenna corresponding to a transmission / reception wave of a multi-frequency broadband. By using a single power feeding unit 1, multi-frequency broadband transmission / reception is performed. Is what you do.
Furthermore, as shown in FIGS. 1 and 2, the multiband antenna according to the first embodiment of the present invention includes a shaft portion 2 that is connected to a single power feeding portion 1 and is common to a low frequency band and a high frequency band, and a frequency. A low-frequency band feeding element 3 and a high-frequency band feeding element 4 branched from the shaft portion 2 in units of bands, and the low-frequency band feeding element 3 and the high-frequency band feeding element 4 are The antenna element has an asymmetric structure.
In Embodiment 1 of the present invention, since the low-frequency band feeding element 3 and the high-frequency band feeding element 4 are antenna elements having an asymmetric structure, the low-frequency band feeding element being an antenna element having an asymmetric structure is used. 3 and the shaft 2 to distribute the current to correspond to the frequency in the low frequency band, and distribute the current to the high frequency band feeding element 4 which is an asymmetrical antenna element and the shaft 2 to increase the frequency. By making it correspond to the frequency of the band, it corresponds to transmission / reception of multi-frequency broadband.

More specifically, in the first embodiment of the present invention shown in FIGS. 1 and 2, the patterns of the feed elements 3 and 4 and the parasitic elements 5 and 6 are formed on the dielectric substrate 8 by etching. Yes. The structure of the multiband antenna according to the first embodiment after etching will be described.
In FIG. 1 and FIG. 2, the feeding elements 3 and 4 and the parasitic elements 5 and 6 are marked with halftone dots to identify each other, and the elements formed on the surface 8 a side of the substrate 8 are not meshed. The elements formed on the back surface 8b of the substrate 8 are marked with a dot-dash line to identify the elements on the front and back surfaces 8a and 8b of the substrate 8.

As shown in FIGS. 1 and 2, the shaft portion 2 is connected to the single power feeding portion 1 and rises to form a straight line on the surface 8 a of the substrate 8. The high frequency band feeding element 4 is formed on the surface 8a of the substrate 8 so as to be branched from the shaft portion 2 with the frequency band as a unit.
In the first embodiment shown in FIGS. 1 and 2, the low-frequency band feeding element 3 is formed on the surface 8 a of the substrate 8 by branching to the left with the shaft portion 2 as the center, and the high-frequency band feeding element 4. Is formed on the surface 8a of the substrate 8 so as to branch rightward with the shaft portion 2 as the center. The low frequency band feeding element 3 may be formed to branch to the right with the shaft portion 2 as the center, and the high frequency band feeding element 4 may be formed to branch to the left with the shaft portion 2 as the center. Is.

Further, the low frequency band feeding element 3 and the high frequency band feeding element 4 are formed as antenna elements having an asymmetric structure.
Specifically, as shown in FIGS. 1 and 2, the low-frequency band feeding element 3 is pulled out from the top of the shaft portion 2 in the lateral direction on the left side, the tip thereof is pulled out downward, and then the left side The tip is drawn upward, the tip is drawn upward, and then the tip is drawn to the right side to meander on the right side of the height range of the shaft portion 2.
As shown in FIGS. 1 and 2, the high-frequency band feeding element 4 is pulled out from the substantially central portion of the shaft portion 2 to the right side, its tip is drawn upward, and then its tip is turned to the left side. By drawing it out, it is meandering on the left side of the height range of the shaft portion 2.
Furthermore, to distribute the current to the feeding element 3 and the shaft portion 2 of the lower frequency bands, the electrical length of the feed element 3 and the shaft portion 2, and the wavelength of the used frequency band and λ _1, λ _1/4 around Is set. Similarly, in order to distribute the current to the feed element 4 and the shaft portion 2 of the high frequency band, the electrical length of the feed element 4 and the shaft portion 2, and the wavelength of the used frequency band and lambda _2, lambda _2/4 It is set near.
As described above, since the wavelengths λ ₁ and λ ₂ of the corresponding use frequency bands are different, the respective electrical lengths are different. As a result, the low frequency band feed element 3 and the high frequency band feed element 4 are: It is formed as an antenna element having an asymmetric structure.
Incidentally, the dimension a is λ (λ _1, λ ₂₎ from the near _{/ 4, λ (λ 1,} λ 2) / 4 hints and _{λ (λ 1, λ 2)} / 4 for resonating around the The electrical length is defined as including the range of fluctuation. From antenna _{theory, λ (λ 1, λ 2} ) / is a 4, reactance adjustment, such tolerance dielectric or assembly process of the substrate 8 is _{influenced, λ (λ 1, λ 2} ) a / 4 Since the electrical length that resonates as the center may vary, it is defined as above.

  As described above, since the feeding elements 3 and 4 in both frequency bands are formed to branch left and right within the height range of the shaft portion 2, the dimension in the height direction of the shaft portion 2 is shortened. Thus, the size is reduced in the height direction. Further, the feeding elements 3 and 4 in both frequency bands are formed by meandering using a space within the height range of the shaft portion 2, thereby reducing the horizontal dimension in FIGS. 1 and 2. Therefore, the size is reduced in the left-right direction.

In Embodiment 1 of the present invention, by combining at least one of the low-frequency band feeding element 3 and the high-frequency band feeding element 4 and the parasitic element 5 or 6, in the low-frequency band and the high-frequency band. Each of them may resonate at two or more frequencies so as to correspond to a multi-frequency broadband.
The example shown in FIGS. 1 and 2 is a combination of the low frequency band feeding element 3 and the high frequency band feeding element 4 with parasitic elements 5 and 6, respectively. Depending on the number of resonance frequencies in the high frequency band, at least one of the low frequency band feeding element 3 and the high frequency band feeding element 4 and the parasitic element 5 or 6 may be combined.

The example shown in FIGS. 1 and 2 will be described. As shown in FIG. 1 and FIG. 2, the parasitic element 5 in the low frequency band includes a short side end 5a along the shaft portion 2, and a length extending in the left lateral direction from the short side end 5a. It is formed on the back surface 8b of the substrate 8 as an inverted L-shaped pattern having side edges 5b. The parasitic element 5 in the low frequency band is arranged such that the short side end portion 5 a is close to the power feeding portion 1 side of the shaft portion 2, and the long side end portion 5 b is in the space below the power feeding element 3. Is arranged.
Similarly, as shown in FIG. 1 and FIG. 2, the parasitic element 6 in the high frequency band extends from the short side end 6a along the shaft portion 2 to the right side direction from the short side end 6a. Further, an inverted L-shaped pattern having a long side end 6b is formed on the surface 8a of the substrate 8. The parasitic element 6 in the high frequency band is arranged such that the short side end portion 6 a is close to the power feeding portion 1 side of the shaft portion 2 and the long side end portion 6 b is in the space below the power feeding element 6. Is arranged.
Furthermore, since the current is distributed to the parasitic element 5 in the low frequency band by being electromagnetically coupled to the shaft part 2, the electrical length of the parasitic element 5 electromagnetically coupled to the shaft part 2 is the wavelength of the used frequency band λ ₃ and is set in the vicinity of λ _3/4. Similarly, since the current is distributed to the parasitic element 6 in the high frequency band by being electromagnetically coupled to the shaft part 2, the electrical length of the parasitic element 6 electromagnetically coupled to the shaft part 2 is the wavelength of the used frequency band. When λ ₄ is set, it is set in the vicinity of λ _4/4 .
As described above, since the wavelengths λ ₃ and λ ₄ of the corresponding use frequency bands are different, the respective electrical lengths are different. As a result, the parasitic element 5 in the low frequency band and the parasitic element 6 in the high frequency band are Is formed as an antenna element having an asymmetric structure.
Note that it is the dimension λ (λ _3, λ ₄₎ and / 4 around, λ (λ _3, λ ₄₎ / 4 hints and λ (λ _3, λ ₄₎ / 4 for resonating around the It is defined as the meaning including the range in which the electrical length varies. From antenna _{theory, λ (λ 3, λ 4} ) / is a 4, reactance adjustment, such tolerance dielectric or assembly process of the substrate 8 is _{influenced, λ (λ 3, λ 4} ) and / 4 Since the electrical length for resonance at the center may fluctuate, it is defined as described above.

Next, the relationship with the ground plate 7 combined with the antenna elements 3, 4, 5, 6 described above will be described. The single power feeding portion 1 is connected to the end portion 2 a of the shaft portion 2 on the ground plate 7 side and the ground plate 7.
The parasitic element 5 in the low frequency band formed on the back surface 8b of the substrate 8 is a ground plate in which the end portion 5c on the ground plate 7 side of the end portion 5a on the short side is formed on the surface 8a of the substrate 8. 7 through the through hole 9.
Further, the parasitic element 6 in the high frequency band has an end portion 6 c on the ground plate 7 side of the end portion 6 a on the short side thereof joined to the ground plate 7. Further, a narrow impedance matching piece 11 is formed on the end edge of the ground plate 7 and the impedance matching piece 11 is joined to the end 6c of the parasitic element 6 in the high frequency band.
Further, a horizontally long impedance matching piece 10 is formed on the surface 8a of the substrate 8, one end portion 10a of the impedance matching piece 10 is joined to the end portion 2a on the ground plate 7 side of the shaft portion 2, and the ground plate The other end portion 10 b of the impedance matching piece 10 along the edge of 7 is joined to the ground plate 7. In this case, a gap 10 c is secured between the impedance matching piece 10 and the edge of the ground plate 7.
The end 5a of the parasitic element 5 formed on the back surface 8b of the substrate 8 and the impedance matching piece 10 formed on the front surface 8a of the substrate 8 intersect as shown in FIG. 1 and FIG. As shown in FIG. 3, the end 5a of the element 5 and the impedance matching piece 10 are insulated by a dielectric substrate 8, and the end 5a of the parasitic element 5 is a substrate as described above. 8 is joined to a ground plate 7 formed on the surface 8a of the substrate 8 through a through hole 9 formed in the substrate 8.
As described above, by combining the parasitic elements 5, 6, the impedance matching pieces 10, 11 and the ground plate 7, impedance matching between the feeding section 1 and the antenna elements 3, 4, 5, 6 can be achieved. I am trying. Therefore, a configuration is adopted in which a coaxial cable is used as the feeding portion 1, the inner conductor of the coaxial cable is connected to the end 2 a of the shaft portion 2, and the outer conductor of the coaxial cable is connected to the ground plate 7. ing.
The impedance matching pieces 10 and 11 are used for better VSWR improvement, and there is no practical problem even when these impedance matching pieces 10 and 11 are not required. I have confirmed.
In the example shown in FIGS. 1 and 2, the ground plate 7 is formed on a part of the substrate 8 by etching. However, as shown in FIG. In addition, only the antenna elements of the parasitic elements 5 and 6 may be formed, and these may be combined with a ground plate or the like that forms a common electrode of the notebook personal computer. The ground plate 7 must be formed on the substrate 8. It is not a sufficient condition.

  1 and 2, the low frequency band parasitic element 5 is formed on the back surface 8b of the substrate 8, and the impedance matching piece 10 is formed on the front surface 8a of the substrate 8. is not. That is, the parasitic element 5 in the low frequency band is formed on the front surface 8a of the substrate 8, the impedance matching piece 10 is formed on the back surface 8b of the substrate 8, and the substrate between the parasitic element 5 and the impedance matching piece 10 is formed. 8, the impedance matching piece 10 may be connected to the shaft portion 2 and the ground plate 7 through a through hole.

  Next, the combination of the low frequency band feeding element 3 and the shaft portion 2 and the parasitic element 4 electromagnetically coupled to the shaft portion 2 is adapted to the low frequency band, and the high frequency band feeding element 4 and the shaft In order to verify that the combination of the portion 2 and the parasitic element 6 electromagnetically coupled to the shaft portion 2 corresponds to the high frequency band, the results of simulating the current distribution in the antenna element are based on FIGS. I will explain.

In the simulation of the current distribution shown in FIGS. 4 to 7, the parasitic element 5 in the low frequency band is arranged with only the end portion 5 a close to the shaft portion 2 as shown in FIGS. 1 and 2. Similarly, the parasitic element 6 in the high frequency band is arranged with only the end 6a close to the shaft part 2, and further, as shown in FIGS. 1 and 2, the parasitic element in both frequency bands. 6 by setting the distance between the end portions 5a, 6a and the shaft portion 2 to be narrower than the distance between the end portions 5b, 6b other than the bent end portions 5a, 6a and the feeding elements 3, 4. A simulation was performed.
The result is analyzed based on FIGS. 4 to 7, a thick solid line means that a strong current flows, and a halftone dot portion indicates that the current flows in a distributed manner. Further, according to the antenna theory, the electrical length between the feeding element 3 and the shaft portion 2 is ¼ of the wavelength λ ₁ of the operating frequency band, and the electrical length between the feeding element 4 and the shaft portion 2 is the operating frequency band. 1/4 of the wavelength λ ₂ , the electrical length of the parasitic element 5 electromagnetically coupled to the shaft portion 2 is ¼ of the wavelength λ ₃ of the operating frequency band, and the parasitic element 6 electromagnetically coupled to the shaft portion 2. Are set to ¼ of the wavelength λ ₄ of the used frequency band.
FIG. 4 shows the current distribution at 700 MHz in the low frequency band. When the current distribution at 700 MHz was simulated, it was found that current was flowing through the shaft portion 2 and the feed element 3.
FIG. 5 shows a current distribution at 960 MHz in the low frequency band. When a current distribution at 960 MHz is simulated, a current flows through the parasitic element 5 in the low frequency band that is electromagnetically coupled to the shaft portion 2. I found out that
FIG. 6 shows the current distribution at 1420 MHz in the high frequency band. When the current distribution at 1420 MHz is simulated, current flows through the shaft portion 2 and the feeding element 4 in the high frequency band. I understand.
FIG. 7 shows a current distribution at 2700 MHz in the high frequency band. When a current distribution at 2700 MHz is simulated, a current flows through the parasitic element 6 in the high frequency band that is electromagnetically coupled to the shaft portion 2. I found out that
As is apparent from the simulation results shown in FIGS. 4 to 7, the low frequency band feed element 3 and the shaft portion 2 correspond to the low frequency band of 700 MHz and are electromagnetically coupled to the shaft portion 2. The element 5 corresponds to the low frequency band 960 MHz, the high frequency band feed element 4 and the shaft part 2 correspond to the high frequency band 1420 MHz, and the high frequency band parasitic element 6 electromagnetically coupled to the shaft part 2 is high. It was found that it corresponds to the frequency band of 2700 MHz.

Next, in order to support the simulation results shown in FIGS. The result is shown in FIG. In FIG. 8, the horizontal axis represents frequency, and the vertical axis represents VSWR. In the actual measurement value of FIG. 8, the target is to set VSWR to “3” or less, and each element 3, 4, 5, 6 is affected by reactance adjustment, the dielectric constant of the substrate 8 or the tolerance of the assembly process. The dimensions of were deviated from the theoretical values as follows.
That is, the electrical length of the feed element 3 and the shaft portion 2 for supporting the low frequency band of 700 MHz is 0.31λ ₁ , and the parasitic element for electromagnetically coupling the shaft portion 2 to the low frequency band of 960 MHz. the electrical length of 5 were respectively set to 0.27λ _3. Similarly, the electrical length of the feeding element 4 and the shaft portion 2 for supporting 1420 MHz in the high frequency band is 0.28λ ₂ , and no power feeding is performed for electromagnetic coupling to the shaft portion 2 to support 2700 MHz in the high frequency band. set the electrical length of the element 6 to 0.26λ _4.

As shown in FIG. 8, it resonates near 780 MHz in the low frequency band, resonates near 960 MHz in the low frequency band, resonates near 1540 MHz in the high frequency band, and resonates near 2700 MHz in the high frequency band. I understand. Although there is a slight deviation between the simulation and the actual measurement value, this is an allowable range, and there was no practical problem.
From the measurement results of the actual measurement values in FIG. 8, the low frequency band feed element 3 and the shaft part 2 correspond to the low frequency band 700 MHz, and the low frequency band non-feeding electromagnetically coupled to the shaft part 2 to the low frequency band 960 MHz. It can be seen that the element 5 corresponds. Therefore, the result of the simulation in the low frequency band in FIGS. 4 and 5 agrees with the actually measured value in FIG.
Similarly, from the measurement results of the actual measurement values in FIG. 8, the high frequency band feeding element 4 and the shaft portion 2 correspond to 1420 MHz in the high frequency band, and the high frequency band is electromagnetically coupled to the shaft portion 2 in the high frequency band 2700 MHz. It can be seen that the parasitic element 6 corresponds. Therefore, the result of the simulation in the high frequency band in FIGS. 6 and 7 agrees with the actually measured value in FIG.
Accordingly, the feeding element 3 and the shaft part 2 in the low frequency band, the parasitic element 5 in the low frequency band electromagnetically coupled to the shaft part 2, the feeding element 4 and the shaft part 2 in the high frequency band, and the shaft part 2 are electromagnetic. It was confirmed from the simulation of the current distribution in FIGS. 4 to 7 and the actually measured values in FIG. 8 that the coupled high-frequency parasitic elements 6 correspond to each other independently.
Further, as is apparent from FIG. 8, it was found that the VSWR for the frequency in the low frequency band and the VSWR for the frequency in the high frequency band are each 3 or less, and the performance that can be put into practical use is maintained.
Further, from the antenna theory, it is λ (λ ₁ , λ ₂ , λ ₃ , λ ₄ ) / 4, but it is affected by reactance adjustment, the dielectric constant of the substrate 8 or the tolerance of the assembly process, and so on. With the center at (λ ₁ , λ ₂ , λ ₃ , λ ₄ ), the resonant electrical length may vary as 0.31λ ₁ , 0.28λ ₂ , 0.27λ ₃ , 0.26λ _4. Was confirmed.

  As described above, according to the first embodiment of the present invention, the low frequency band feeding element and the high frequency band feeding element have an asymmetric structure, and the shaft portion common to the low frequency band and the high frequency band and the low frequency band By distributing the current to the feeding element, it can correspond to the frequency of the low frequency band, and by distributing the current to the shaft part and the feeding element of the high frequency band, it can correspond to the frequency of the high frequency band, It can handle multi-frequency broadband transmission / reception.

  Furthermore, the antenna element can be made to have a planar structure by branching a low-frequency band feeding element and a high-frequency band feeding element from the shaft portion in units of frequency bands. Further, by incorporating a feeding element and a parasitic element with an asymmetric structure in a space within the height range of the shaft portion, the height dimension along the shaft portion and the dimension in the direction in which the feeding element is branched. It is possible to realize a reduction in size and thickness.

  Further, by combining at least one of a low-frequency band feeding element and a high-frequency band feeding element and a parasitic element, the low-frequency band and the high-frequency band can be resonated at two frequencies or more to obtain a multi-frequency broadband. It can respond.

  Furthermore, one end of the parasitic element in the low frequency band and the high frequency band is joined to the ground plate, and one end of the shaft portion is joined to the ground plate by the impedance matching piece, so that the VSWR can be improved further. It is.

(Embodiment 2)
An example in which the shapes of the shaft portion 2, the feed elements 3 and 4, and the parasitic elements 5 and 6 in Embodiment 1 shown in FIGS. 1 and 2 are changed will be described as Embodiment 2 of the present invention.

The multi-band antenna according to the second embodiment of the present invention shown in FIGS. 9 and 10 is intended for a multi-band antenna corresponding to a transmission / reception wave of a multi-frequency broadband as in the first embodiment shown in FIGS. Thus, transmission / reception is performed by using a single power feeding unit 1.
Furthermore, as shown in FIGS. 9 and 10, the multiband antenna according to the second embodiment of the present invention includes a shaft portion 2 that is connected to a single power feeding portion 1 and is common to a low frequency band and a high frequency band, and a frequency. A low-frequency band feeding element 3 and a high-frequency band feeding element 4 branched from the shaft portion 2 in units of bands, and the low-frequency band feeding element 3 and the high-frequency band feeding element 4 are The antenna element has an asymmetric structure.
In Embodiment 2 of the present invention, since the low-frequency band feeding element 3 and the high-frequency band feeding element 4 are antenna elements having an asymmetric structure, the low-frequency band feeding element being an antenna element having an asymmetric structure is used. 3 and the shaft 2 to distribute the current to correspond to the frequency in the low frequency band, and distribute the current to the high frequency band feeding element 4 which is an asymmetrical antenna element and the shaft 2 to increase the frequency. By making it correspond to the frequency of the band, it corresponds to transmission / reception of multi-frequency broadband.

More specifically, in the second embodiment of the present invention shown in FIG. 9, the patterns of the feeding elements 3 and 4 and the parasitic elements 5 and 6 are formed on the dielectric substrate 8 by etching. The structure of the multiband antenna according to the second embodiment after the etching process will be described.
In FIG. 9 and FIG. 10, the feeding elements 3 and 4 and the parasitic elements 5 and 6 are marked with a halftone dot to identify each other, and the element formed on the surface 8a side of the substrate 8 is a mesh. The elements formed on the front and back surfaces 8a and 8b of the substrate 8 are identified by attaching dots to the elements formed on the back surface 8b of the substrate 8 by attaching a one-dot chain line.

As shown in FIG. 9, the shaft portion 2 is connected to the single power feeding portion 1 and rises to form a straight line on the surface 8 a of the substrate 8. The band feeding element 4 is formed on the surface 8 a of the substrate 8 so as to be branched from the shaft portion 2 in units of frequency bands.
In FIG. 9, the shaft portion 2 and the feeding elements 3 and 4 are separated by a two-dot chain line based on a current path.
In the second embodiment shown in FIG. 9, the low-frequency band feeding element 3 is formed on the surface 8 a of the substrate 8 by branching to the right with the shaft portion 2 as the center, and the high-frequency band feeding element 4 is formed on the shaft 8. It is formed on the surface 8 a of the substrate 8 so as to branch to the left with the portion 2 as the center. The low frequency band feeding element 3 may be formed to branch to the left with the shaft portion 2 as the center, and the high frequency band feeding element 4 may be formed to branch to the right with the shaft portion 2 as the center. Is.

Further, the low frequency band feeding element 3 and the high frequency band feeding element 4 are formed as antenna elements having an asymmetric structure.
Specifically, as shown in FIG. 9, the low frequency band feeding element 3 includes a taper element 3 a that is tapered so as to taper from the side of the shaft portion 2 toward the right side, and a substrate. 8 is formed on the back surface 8b of the straight line 8b, and these are joined by the through hole 12 to ensure a necessary length. Further, the front end portion 6c of the linear piece 3b of the feeding element 3 formed on the back surface 8b of the substrate 8 is bent and electromagnetically coupled to the pad 14 formed on the back surface 8b of the substrate 8 so as to achieve impedance matching. I have to.
As shown in FIG. 9, the high-frequency band feeding element 4 is formed on the surface 8a of the substrate 8 so as to be tapered from the side of the shaft portion 2 to the left side, and its tip is elongated. is doing.
Furthermore, to distribute the current to the feeding element 3 and the shaft portion 2 of the lower frequency bands, the electrical length of the feed element 3 and the shaft portion 2, and the wavelength of the used frequency band and λ _5, λ _5/4 around Is set. Similarly, in order to distribute the current to the feed element 4 and the shaft portion 2 of the high frequency band, the electrical length of the feed element 4 and the shaft portion 2, and the wavelength of the used frequency band and λ _6, λ _6/4 It is set near.
As described above, since the wavelengths in the corresponding use frequency bands are different, the electrical lengths thereof are different. As a result, the low-frequency band feeding element 3 and the high-frequency band feeding element 4 are asymmetric antenna elements. Will be formed.
Incidentally, the dimension a is λ (λ _5, λ ₆₎ from the / 4 around, λ (λ _5, λ ₆₎ / 4 hints and λ (λ _5, λ ₆₎ / 4 for resonating around the It is defined as the meaning including the range in which the electrical length varies. From antenna _{theory, λ (λ 5, λ 6} ) / is a 4, reactance adjustment, such tolerance dielectric or assembly process of the substrate 8 is _{influenced, λ (λ 5, λ 6} ) a / 4 Since the electrical length for resonance at the center may fluctuate, it is defined as described above.

  As described above, since the feeding elements 3 and 4 in both frequency bands are formed to branch left and right within the height range of the shaft portion 2, the dimension in the height direction of the shaft portion 2 is shortened. Thus, the size is reduced in the height direction. Further, the feeding element 3 in both frequency bands is formed by dividing it into the front surface 8a and the back surface 8b of the substrate 8, thereby shortening the horizontal dimension in FIGS. 9 and 10 and reducing the size in the horizontal direction. I am trying.

In the second embodiment of the present invention, by combining at least one of the low frequency band feeding element 3 and the high frequency band feeding element 4 and the parasitic element 5 or 6, in the low frequency band and the high frequency band. Each of them may resonate at two or more frequencies so as to correspond to a multi-frequency broadband.
The example shown in FIG. 9 and FIG. 10 is a combination of the low frequency band feeding element 3 and the high frequency band feeding element 4 with parasitic elements 5 and 6, respectively. Depending on the number of resonance frequencies in the high frequency band, at least one of the low frequency band feeding element 3 and the high frequency band feeding element 4 and the parasitic element 5 or 6 may be combined.

The example shown in FIGS. 9 and 10 will be described. As shown in FIGS. 9 and 10, the parasitic element 6 in the high frequency band includes a short side end portion 6 a along the shaft portion 2 and a length extending in the left lateral direction from the short side end portion 6 a. It is formed on the surface 8a of the substrate 8 as an inverted L-shaped pattern having side edges 6b. The parasitic element 6 in the high frequency band is arranged such that the short side end portion 6 a is close to the power feeding portion 1 side of the shaft portion 2 and the long side end portion 6 b is in the space below the power feeding element 4. Is arranged.
Similarly, the parasitic element 5 in the low frequency band includes a short-side end portion 5a along the top of the shaft portion 2, and a long-side end portion 5b extending in the left lateral direction from the short-side end portion 5a. Is formed on the surface 8a of the substrate 8 as an inverted L-shaped pattern having The parasitic element 5 in the low frequency band is arranged such that the short side end portion 5a is close to the top side of the shaft portion 2, and the surface 8a of the substrate 8 is positioned above the feeding element 4 and the parasitic element 6. It is placed in the existing space.
Furthermore, the low frequency band of a current to the parasitic element 5 for distributing the electrical length of the passive element 5 for electromagnetic coupling to the shaft 2, and the wavelength of the used frequency band and λ _7, λ _7/4 around Is set. Similarly, in order to distribute the current to the parasitic element 6 of the high frequency band, the electrical length of the passive element 6 is connected to the shaft portion 2 to Chuan, when the wavelength of the used frequency band and λ _8, λ ₈ / It is set to around 4.
As described above, since the wavelengths of the corresponding use frequency bands are different, the respective electrical lengths are different. As a result, the parasitic element 5 in the low frequency band and the parasitic element 6 in the high frequency band have an asymmetric structure. It will be formed as an antenna element.
Incidentally, the dimension a is λ (λ _7, λ ₈₎ and / 4 around, λ (λ _7, λ ₈₎ / 4 include and λ (λ _7, λ ₈₎ / 4 for resonating around the It is defined as the meaning including the range in which the electrical length varies. From antenna _{theory, λ (λ 7, λ 8} ) is a / 4, the reactance adjusting and tolerances in the dielectric constant or the assembly process of the substrate 8 is _{influenced, λ (λ 7, λ 8} ) and / 4 Since the electrical length for resonance at the center may fluctuate, it is defined as described above.

Next, the relationship with the ground plate 7 combined with the antenna elements 3, 4, 5, 6 described above will be described. The single power feeding portion 1 is connected to the end portion 2 a of the shaft portion 2 on the ground plate 7 side and the ground plate 7.
The parasitic element 5 in the low frequency band has an end portion 5 c on the ground plate 7 side of the end portion 5 b on the long side thereof joined to the ground plate 7.
Further, the parasitic element 6 in the high frequency band has an end portion 6 c on the ground plate 7 side of the end portion 6 b of the long side joined to the ground plate 7.
As described above, the parasitic elements 5 and 6 and the ground plate 7 are combined to achieve impedance matching between the feeder 1 and the antenna elements 3, 4, 5 and 6. Therefore, a coaxial cable 13 is used as the feeding portion 1, and the inner conductor 13 a of the coaxial cable 13 is connected to the end portion 2 a of the shaft portion 2 through the through hole 15 of the substrate 8, and the outside of the coaxial cable 13 is connected. A configuration in which the conductor 13b is connected to the ground plate 7 is adopted.
Further, as shown in FIGS. 9 and 10, the coaxial cable 13 is pulled out in the lateral direction along the upper edge 7a of the ground plate 7, so that the magnetic field due to the current flowing through the coaxial cable 13 is changed to the antenna elements 3, 4, and 4. 5 and 6 are avoided. The drawing structure of the coaxial cable 13 shown in FIGS. 9 and 10 can be similarly applied to the antenna shown in FIGS.
In the example shown in FIGS. 1 and 2, the ground plate 7 is formed on a part of the substrate 8 by etching. However, as shown in FIG. Only the antenna elements of the parasitic elements 5 and 6 may be formed, and these may be combined with a ground plate or the like that forms a common electrode of the notebook personal computer. It is not necessary that the ground plate 7 is formed on the substrate 8. Absent.

Actual values measured by the multiband antenna according to the second embodiment shown in FIGS. 9 and 10 are measured, and the results are shown in FIG.
As shown in FIG. 11, it resonates near 700 MHz in the low frequency band, resonates near 960 MHz in the low frequency band, resonates near 1420 MHz in the high frequency band, and resonates near 2700 MHz in the high frequency band. I understand.
From the results of FIG. 11, the feed elements 3 and 4 and the shaft part 2 in the low frequency band and the high frequency band in the low frequency band and the high frequency band and the parasitic elements 5 and 6 electromagnetically coupled to the shaft part 2 are obtained. It can be seen that each corresponds independently.
Further, as is apparent from FIG. 11, the VSWR for the frequency in the low frequency band and the VSWR for the frequency in the high frequency band are each 3 or less, and it was found that the performance that can be put into practical use is maintained.

The embodiment 2 of the present invention shown in FIG. 9 and FIG. 10 not only can obtain the same effect as the embodiment 1 shown in FIG. 1 and FIG. Even if the feeding element and the parasitic element in the frequency band and the feeding element and the parasitic element in the high frequency band are formed, the feeding element and the non-feeding element in the low frequency band are the same as in the first embodiment shown in FIGS. The feed element can independently correspond to the low frequency band multi-frequency, and similarly, the high frequency band feed element and the parasitic element can independently correspond to the high frequency band multi-frequency. .
Furthermore, since the antenna element is incorporated using the front surface and the back surface of the substrate, the antenna can be miniaturized.

(Embodiment 3)
A configuration for shortening the dimension in the height direction of the shaft portion 2 will be described as a third embodiment of the present invention.
To shorten the dimension in the height direction of the shaft portion 2, as shown in FIG. 12A, the width of the upper side 3d of the two sides along the parallel of the feeding element 3 in the low frequency band is T ₁ , and the lower side When 3e width of the _{T 2,} is set to satisfy the relationship of _T 1> T _2. Similarly, in order to shorten the dimension in the height direction of the shaft portion 2, as shown in FIG. 12A, the width of the upper side 4a of the two sides along the parallel of the feeding element 4 in the high frequency band is set to T. _3, when the width of the lower edge 4b and _{T 4,} is set to satisfy the relationship of T 3> _{T 4.}
As described above, the width dimension of the upper side 3d and the lower side 3e of the feeding element 3 in the low frequency band is set to T ₁ > T ₂ and the width dimension of the upper side 4a and the lower side 4b of the feeding element 4 in the high frequency band. the by setting T _3> T _4, each of the lower side 3e, by decreasing the width of the 4b, which shortens the dimension of the shaft portion 2 in the height direction.
FIG. 12B shows the result of actual measurement of the frequency-VSWR relationship using the multiband antenna shown in FIG.
When the characteristics of FIG. 12B and the characteristics of FIG. 8 are compared, since the VSWRs of 700 MHz to 2700 MHz are both “3” or less, the configuration of FIG. It turns out that it is effective in shortening.
By adopting the configuration shown in FIG. 12A, the dimension of the shaft portion 2 in the height direction can be shortened, and further miniaturization can be realized.
When there is a margin in the dimension in the height direction of the shaft 2 and it is not necessary to shorten it, the width relationship between the upper side 3d, 4a and the lower side 3e, 4b is expressed as T as shown in FIG. _{Even when} the relationship of ₁ <T ₂ and T ₃ <T ₄ is set, as is apparent from FIG. 13B, the same characteristics as the frequency-VSWR shown in FIG. 12B can be obtained. In this case, the configuration shown in FIG. 13 (a) or FIG. 12 (a) may be adopted as appropriate.

FIG. 14 shows another configuration for shortening the dimension of the shaft portion in the height direction. As shown in FIG. 14A, the width of the upper side 3d of the two sides along the parallel of the feed element 3 in the low frequency band is T ₁ , the width of the lower side 3e is T ₂ , and T ₁ > T ₂ Set to the relationship. Similarly, in order to shorten the dimension in the height direction of the shaft portion 2, as shown in FIG. 12A, the width of the upper side 4a of the two sides along the parallel of the feeding element 4 in the high frequency band is set to T. _3, when the width of the lower edge 4b and _{T 4,} is set to satisfy the relationship of T 3> _{T 4.} For setting the widths T ₁ , T ₂ , T ₃ , T ₄ between the upper sides 3d, 4a and the lower sides 3e, 4b, see FIG. 12 (a).
Further, as shown in FIG. 14 (a), the tip 3f of the wide upper side 3d of the feed element 3 in the low frequency band and the tip 4c of the wide upper side 4a of the feed element 4 in the high frequency band are respectively provided. By bending upward or downward with an angle, the dimension in the height direction of the shaft portion 2 is further shortened than the configuration shown in FIG.
FIG. 14B shows the result of actual measurement of the frequency-VSWR relationship using the multiband antenna shown in FIG.
Comparing the characteristics of FIG. 14 (b) with the characteristics of FIG. 8, the VSWR of 700 MHz to 2700 MHz changes. However, since it can withstand use, it is effective in shortening the dimension of the shaft portion 2 in the height direction. I know that there is.
By adopting the configuration shown in FIG. 14A, the dimension in the height direction of the shaft portion 2 can be further shortened compared to the configuration shown in FIG. 12A, and further downsizing can be realized. Is.
In the embodiment shown in FIG. 14A, a part of both the low-frequency band feeding element 3 and the high-frequency band feeding element 4 are bent along the length direction of the elements 3 and 4. Although the width of the power feeding elements 3 and 4 (see the widths T ₁ and T ₃ in FIG. 12A) is narrowed by bending upward or downward at a location, the present invention is not limited to this. That is, the width (T ₁ , T ₃ ) of the power supply element may be narrowed by bending a part of at least one of the power supply element 3 in the low frequency band and the power supply element 4 in the high frequency band. .
The widths of the feeding elements 3 and 4 are bent by partially bending both the feeding element 3 in the low frequency band and the feeding element 4 in the high frequency band (see widths T ₁ and T ₃ in FIG. 12A). Is narrowed, the height of the antenna element can be lowered in the left-right direction around the shaft portion 2.
Further, when the width (T ₁ , T ₃ ) of the feeding element is narrowed by bending at least a part of at least one of the feeding element 3 in the low frequency band and the feeding element 4 in the high frequency band, The height of the antenna element on the right side or the left side can be lowered.
Further, in FIG. 14A, by forming the upper sides 3d and 4a of the power feeding elements 3 and 4 in a block shape, the volume integral corresponding to the tip portions 3f and 4c of the power feeding elements 3 and 4 bent upward is obtained. By ensuring, the dimension in the height direction of the shaft portion 2 may be further shortened than the configuration shown in FIG.

1, 2, 9, and 10, in the low frequency band, the distance between the end portion 5 a of the parasitic element 5 and the shaft portion 2 is the same as the end portion 5 b of the parasitic element 5 and the feed element 3. Or the distance between the end b of the parasitic element 5 and the feed element 3, or between the end b of the parasitic element 5 and the feed element 3. It may be set wider than the distance.
1, 2, 9, and 10, in the high frequency band, the distance between the end 6 a of the parasitic element 6 and the shaft 2 is equal to the end 6 b of the parasitic element 6 and the feed element 3. It is necessary to set it narrower than the distance between.
Furthermore, in the examples shown in FIGS. 1, 2, 9, and 10, the antenna elements 3, 4, 5, and 6 are patterned on the substrate 8, but the present invention is not limited to this. That is, the antenna elements 3, 4, 5, and 6 may be molded and combined with sheet metal, and the antenna elements 3, 4, 5, and 6 may be constructed as a laminated structure.

  The present invention is compatible with multi-frequency broadband transmission and reception, and can contribute to the realization of miniaturization and thinning.

DESCRIPTION OF SYMBOLS 1 Feeding part 2 Shaft part 3 Low frequency band feeding element 4 High frequency band feeding element 5 Low frequency band parasitic element 6 High frequency band parasitic element 7 Ground plate 8 Substrate

Claims (7)

A multiband antenna corresponding to a multi-frequency broadband transmission / reception wave,
A shaft common to a low frequency band and a high frequency band connected to a single power supply unit;
A low-frequency power feeding element and a high-frequency power feeding element branched from the shaft portion in units of frequency bands;
The low-frequency band feeding element and the high-frequency band feeding element are antenna elements having an asymmetric structure.   The multiband antenna according to claim 1, further comprising a parasitic element that forms a pair with at least one of the low-frequency band feeding element and the high-frequency band feeding element.   The multiband antenna according to claim 2, wherein the parasitic element in the low frequency band and the parasitic element in the high frequency band are antenna elements having an asymmetric structure.   4. The low frequency band parasitic element and the high frequency band parasitic element each have one end grounded to a ground plate, and one end of the shaft portion grounded to the ground plate by an impedance matching piece. Multiband antenna. The low-frequency band feeding element and the high-frequency band feeding element are branched to the left and right around the shaft portion;
The multi-frequency element according to claim 2, wherein the low-frequency band parasitic element and the high-frequency band parasitic element are arranged along the low-frequency band feeder element and the high-frequency band feeder element. Band antenna.   The multiband antenna according to claim 5, wherein the width of the parasitic elements in both frequency bands is set narrower than the width of the feeder elements in both frequency bands, and the height dimension along the shaft portion is shortened.   The multiband antenna according to claim 2, wherein a part of at least one of the low frequency band feeding element and the high frequency band feeding element is bent.

Images