JP4637638B2 - Multi-frequency antenna - Google Patents
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- JP4637638B2 JP4637638B2 JP2005130591A JP2005130591A JP4637638B2 JP 4637638 B2 JP4637638 B2 JP 4637638B2 JP 2005130591 A JP2005130591 A JP 2005130591A JP 2005130591 A JP2005130591 A JP 2005130591A JP 4637638 B2 JP4637638 B2 JP 4637638B2
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本発明は、パソコン、ＰＤＡ（携帯型情報機器）、携帯電話、あるいはＶＩＣＳなどの情報端末機器等に内蔵させる多周波用小型アンテナに関する。 The present invention relates to a small multi-frequency antenna incorporated in an information terminal device such as a personal computer, PDA (portable information device), mobile phone, or VICS.
近年の無線ＬＡＮあるいはＢｌｕｅｔｏｏｔｈ（近距離無線データ通信システム）搭載のＰＤＡ等においては、アンテナの多周波化とともに小型化の要求がますます強くなってきている。
そこで、本出願人は先に、図４に示すような多周波用小型アンテナを提案した（特願２００４−１０１３７４）。このアンテナにおいては、高周波側放射エレメント（１ａ）とグランド板（４）と短絡部（３）とでスリット（Ｓ）を形成するとともに、同軸ケーブル（５）の内部導体をスリット（Ｓ）の開放端部に位置する給電点（Ｐ１）に、そして外部導体をアースポイント（Ｐ２）に接続し、エレメント部（１）に給電することによりスリット（Ｓ）が高周波側放射エレメント（１ａ）の共振点近傍に共振点を有するスリットアンテナとして機能するように工夫されている。なお、（１ｂ）は低周波側放射エレメントである。
しかるに、このアンテナにおいても、そこそこの通信品質は確保されるものの、用途あるいは設置環境によっては、帯域幅不足に起因する感度不良が生じることが判明した。この障害は、無線ＬＡＮ等で使用される周波数帯域（２ＧＨｚ及び５ＧＨｚ）は勿論、それよりも低めの周波数帯域、特に携帯電話等で使用されているＷＡＮ帯域（８２４ＭＨｚ〜９６０ＭＨｚ及び１７１０ＭＨｚ〜２２００ＭＨｚ）で起こりやすい。更に、使用周波数が低い場合、エレメント長が長くなるので、アンテナ形状・寸法が大きくなってしまい、機器によっては組み込めなくなる。
それゆえ、通信感度に優れ尚且つ、小型で構造がシンプルな多周波用アンテナが待ち望まれている。併せて、無線ＬＡＮ帯域のみならずＷＡＮ帯域においても適用可能な多周波用アンテナも待ち望まれている。
In recent years, PDAs and the like mounted on a wireless LAN or Bluetooth (short-range wireless data communication system) are increasingly required to be miniaturized as antennas have multiple frequencies.
Therefore, the present applicant has previously proposed a multi-frequency small antenna as shown in FIG. 4 (Japanese Patent Application No. 2004-101374). In this antenna, the high-frequency radiation element (1a), the ground plate (4), and the short-circuit portion (3) form a slit (S), and the inner conductor of the coaxial cable (5) is opened to the slit (S). The slit (S) is connected to the feeding point (P1) located at the end, and the outer conductor is connected to the earth point (P2), and the element (1) is fed to make the slit (S) the resonance point of the high-frequency radiation element (1a). It is devised to function as a slit antenna having a resonance point in the vicinity. In addition, (1b) is a low frequency side radiation element.
However, even with this antenna, although moderate communication quality is ensured, it has been found that depending on the application or installation environment, a sensitivity failure due to insufficient bandwidth occurs. This failure is not only in the frequency bands (2 GHz and 5 GHz) used in wireless LANs and the like, but also in lower frequency bands, particularly in the WAN bands (824 MHz to 960 MHz and 1710 MHz to 2200 MHz) used in mobile phones and the like. It is easy to happen. Furthermore, when the operating frequency is low, the element length becomes long, so that the antenna shape and dimensions become large, and some devices cannot be incorporated.
Therefore, a multi-frequency antenna having excellent communication sensitivity, a small size and a simple structure is awaited. In addition, a multi-frequency antenna that can be applied not only in the wireless LAN band but also in the WAN band is also awaited.
したがって、本発明の課題は、十分な帯域幅を有することで通信感度に優れ、しかも小型で構造がシンプルな多周波用アンテナを提供することにある。
更に、本発明の他の課題は、無線ＬＡＮ帯域のみならずＷＡＮ帯域においても対応できる多周波用アンテナを提供することにある。
Accordingly, an object of the present invention is to provide a multi-frequency antenna that has a sufficient bandwidth, has excellent communication sensitivity, is small, and has a simple structure.
Furthermore, another object of the present invention is to provide a multi-frequency antenna capable of supporting not only the wireless LAN band but also the WAN band.
本発明者等は、図４に示した多周波用アンテナの低周波側放射エレメントの上方（図面の上部）で、その端部から該エレメントと平行且つ同方向に指向する突出部を配するとき、この突出部と該スリット部との間で高周波側の帯域幅が広がるような相互作用が生じることを究明した。更に、低周波側放射エレメントの幅如何によっては低周波側での帯域幅を更に広がると言う事実も究明し、ＷＡＮ帯域での安定な通信感度を実現するに至った。 When the present inventors arrange a projecting portion that is parallel to the element from the end of the low-frequency radiation element of the multi-frequency antenna shown in FIG. The inventors have clarified that an interaction that widens the bandwidth on the high frequency side occurs between the protruding portion and the slit portion. Furthermore, the fact that the bandwidth on the low frequency side is further expanded depending on the width of the low frequency side radiating element has been investigated, and stable communication sensitivity in the WAN band has been realized.
本発明のアンテナでは、以下のような格別顕著な効果が奏される。
（１）上記突出部とスリット部との相互作用により、高周波側放射エレメントの共振点近傍での帯域幅が広がるとともに周波数特性（ＶＳＷＲ）が改善され、もって通信感度が向上する。
（２）低周波側放射エレメント幅を特に４ｍｍ以上で尚且つ高周波側放射エレメントの幅より広くすることにより、ＷＡＮ帯域での安定な送受信が実現する。
（３）放射エレメントの構成本数を増やすことにより、３周波以上の多周波アンテナに対しても容易に対応できる。
（４）平面アンテナだけでなく立体アンテナ等の各種形態のアンテナに対しても対応でき、多用途での適用が期待される。
The antenna of the present invention has the following remarkable effects.
(1) The interaction between the projecting portion and the slit portion increases the bandwidth in the vicinity of the resonance point of the high-frequency side radiating element and improves the frequency characteristic (VSWR), thereby improving the communication sensitivity.
(2) Stable transmission and reception in the WAN band is realized by making the width of the low-frequency side radiating element particularly 4 mm or more and wider than the width of the high-frequency side radiating element.
(3) By increasing the number of radiating elements, it is possible to easily cope with multi-frequency antennas having three or more frequencies.
(4) Not only a planar antenna but also various types of antennas such as a three-dimensional antenna can be dealt with, and versatile application is expected.
以下、上述のスリットと突出部による共振点を最大共振周波数に設定した２周波対応のアンテナについて、添付図面を参照しながら説明する。
図１は、本発明の２周波用アンテナの一例を示す正面図である。
図２は、図１のアンテナに給電用同軸ケーブルを取り付けた際の斜視図である。
図３は、２周波に対応した本発明のアンテナの周波数特性（ＶＳＷＲ）を示す図（グラフ）である。
図４は、２周波に対応した先願発明のアンテナの一例を示す斜視図である。
図１及び図２において、（１）は、エレメント部であり、共に細幅状の高周波側放射エレメント（１ａ）と低周波側放射エレメント（１ｂ）とからなる、いわゆるデュアルタイプとして図示されている。（２）は、後で詳述する細幅状の突出部、（３）は、高周波側放射エレメント（１ａ）とグランド板（４）とを電気的に接続する短絡部である。その際、高周波側放射エレメント（１ａ）は短絡部（３）を介してグランド板（４）と平行に形成され、更に、該エレメント（１ａ）の終端部から接続部（Ａ）を経て低周波側放射エレメント（１ｂ）がＬ字状に折り返す形でグランド板（４）と平行に形成されている。この低周波側放射エレメント（１ｂ）の上部には、該エレメントの開始端から接続部（Ｂ）を経て前記細幅状の突出部（２）が低周波側放射エレメント（１ｂ）と同方向に配されている。そして、高周波側放射エレメント（１ａ）と短絡部（３）とグランド板（４）の縁部（４ａ）とでスリット（Ｓ）が形成される。
更に、（Ｌ）は高周波側放射エレメント（１ａ）の長さ、（Ｌ１）はスリット（Ｓ）の長さ、（Ｌ２）は高周波側放射エレメント（１ｂ）とグランド板（４）の縁部（４ａ）との間隔（スリット幅）、（Ｌ３）は突出部（２）の長さ、（Ｌ４）は突出部（２）の幅、そして、（Ｐ１）はエレメント部（１）に給電するための同軸ケーブル（５）（図２）の内部導体を接続する給電点で、スリット（Ｓ）の開放部近傍に位置している。又、（Ｐ２）はケーブル（５）の外部導体を接続するアースポイントで、スリット（Ｓ）の開放部近傍に位置している。
本発明で特徴的なことは、スリット（Ｓ）単独の共振作用の利用に加えてスリット（Ｓ）と突出部（２）との相互作用を利用して高周波側放射エレメント（１ａ）の共振点近傍での帯域幅を更に広げながら周波数特性（ＶＳＷＲ）を改善することにより、アンテナ通信感度を大幅に向上させたことである。
この点について、以下に詳細に説明する。
本発明では、スリット部（Ｓ）での共振周波数を高周波側放射エレメント（１ａ）の共振周波数近傍の最大共振周波数とする。このことから、スリット（Ｓ）の長さ（Ｌ１）と突出部（２）の長さ（Ｌ３）を加算した長さ（Ｌ１＋Ｌ３）を、高周波側放射エレメント（１ａ）の長さ（Ｌ）近傍に設定する。これにより、スリット（Ｓ）と突出部（２）とで高周波側放射エレメント（１ａ）近傍の最大共振周波数で共振するので、スリット（Ｓ）単独の共振に、更にスリット（Ｓ）と突出部（２）との共振も加わるのでアンテナの帯域幅を更に広げることができる。
具体的に述べると、無線ＬＡＮ等の周波数帯域として２ＧＨｚ及び５ＧＨｚ（ギガヘルツ）が確保できるよう、高周波側放射エレメント（１ａ）の共振周波数に応じてスリット部（Ｓ）と突出部（２）の合計した長さ（Ｌ１＋Ｌ３）を調整して共振周波数を設定すればよい。この場合、突出部（２）の長さ（Ｌ３）が短いと帯域幅が広がらず、逆に、長いと周波数特性（ＶＳＷＲ）が悪化する。この点から、突出部（２）の長さ（Ｌ３）は、高周波側放射エレメント（１ａ）の長さ（Ｌ１）の１０％〜５０％程度に設定すればよい。具体的には、その長さ（Ｌ３）は０．５ｍｍ〜３０ｍｍ、好ましくは５ｍｍ〜２５ｍｍ程度であればよい。又、その幅（Ｌ４）は、帯域幅の拡大効果と寸法の拡大防止の両面を考慮して設定すればよい。具体的には、０．５ｍｍ〜２ｍｍ、好ましくは１ｍｍ〜１．５ｍｍであり、通常は、高周波側放射エレメント（１ａ）又は低周波側放射エレメント（１ｂ）の幅と同じであればよい。
更に、本発明では、給電点（Ｐ１）及びアースポイント（Ｐ２）をスリット（Ｓ）の開放部近傍に位置させる。これにより、スリット（Ｓ）を最大共振周波数のスリットアンテナとして共振させることが可能となる。更に言えば、給電点（Ｐ１）及びアースポイント（Ｐ２）の位置が、スリット（Ｓ）の開放部に面した夫々の角部に位置している方が好ましい。この場合、同軸ケーブル（５）からスリット（Ｓ）への給電距離が短くなり、給電損失が少なくなるので、スリット（Ｓ）に誘起される電界強度が強くなり、感度が向上する。
又、スリット幅（Ｌ２）が広すぎると、スリット部（Ｓ）に誘起される電磁界が弱くなり、反対に、この間隔が狭すぎると干渉を起こす等の不安定状態になる。このことから、（Ｌ２）は、０．５ｍｍ〜２．０ｍｍの範囲で調整することが好ましい。
Hereinafter, a dual-frequency antenna in which the resonance point by the slit and the protrusion is set to the maximum resonance frequency will be described with reference to the accompanying drawings.
FIG. 1 is a front view showing an example of the dual-frequency antenna of the present invention.
FIG. 2 is a perspective view when a feeding coaxial cable is attached to the antenna of FIG.
FIG. 3 is a graph (graph) showing the frequency characteristic (VSWR) of the antenna of the present invention corresponding to two frequencies.
FIG. 4 is a perspective view showing an example of the antenna of the prior invention corresponding to two frequencies.
1 and 2, (1) is an element portion, which is illustrated as a so-called dual type, which is composed of a narrow high-frequency side radiating element (1a) and a low-frequency side radiating element (1b). . (2) is a narrow protrusion which will be described in detail later, and (3) is a short-circuit portion that electrically connects the high-frequency radiation element (1a) and the ground plate (4). At that time, the high-frequency side radiating element (1a) is formed in parallel with the ground plate (4) through the short-circuited part (3), and further, the low-frequency side through the connecting part (A) from the terminal part of the element (1a). The side radiating element (1b) is formed in parallel with the ground plate (4) so as to be folded in an L shape. At the upper part of the low-frequency side radiating element (1b), the narrow protrusion (2) extends in the same direction as the low-frequency side radiating element (1b) from the start end of the element through the connecting part (B). It is arranged. And a slit (S) is formed by the high frequency side radiation element (1a), the short circuit part (3), and the edge part (4a) of the ground plate (4).
Furthermore, (L) is the length of the high-frequency side radiating element (1a), (L1) is the length of the slit (S), and (L2) is the edge of the high-frequency side radiating element (1b) and the ground plate (4) ( 4a) (slit width), (L3) is the length of the protrusion (2), (L4) is the width of the protrusion (2), and (P1) is for supplying power to the element part (1) This is a feeding point for connecting the inner conductors of the coaxial cable (5) (FIG. 2) and is located near the open portion of the slit (S). Further, (P2) is an earth point for connecting the outer conductor of the cable (5), and is located near the open portion of the slit (S).
What is characteristic of the present invention is that the resonance point of the high-frequency radiation element (1a) is obtained by utilizing the interaction between the slit (S) and the protrusion (2) in addition to the use of the resonance action of the slit (S) alone. The antenna communication sensitivity is greatly improved by improving the frequency characteristic (VSWR) while further expanding the bandwidth in the vicinity.
This point will be described in detail below.
In the present invention, the resonance frequency at the slit portion (S) is set to the maximum resonance frequency in the vicinity of the resonance frequency of the high-frequency radiation element (1a). From this, the length (L1 + L3) obtained by adding the length (L1) of the slit (S) and the length (L3) of the protrusion (2) is near the length (L) of the high-frequency radiation element (1a). Set to. Accordingly, the slit (S) and the protrusion (2) resonate at the maximum resonance frequency in the vicinity of the high-frequency side radiating element (1a), so that the slit (S) and the protrusion ( Since the resonance with 2) is also added, the bandwidth of the antenna can be further expanded.
Specifically, the sum of the slit portion (S) and the protruding portion (2) according to the resonance frequency of the high-frequency side radiating element (1a) so that 2 GHz and 5 GHz (gigahertz) can be secured as a frequency band of a wireless LAN or the like. The resonance frequency may be set by adjusting the length (L1 + L3). In this case, if the length (L3) of the projecting portion (2) is short, the bandwidth is not widened. Conversely, if the length (L3) is long, the frequency characteristic (VSWR) is deteriorated. From this point, the length (L3) of the protrusion (2) may be set to about 10% to 50% of the length (L1) of the high-frequency radiation element (1a). Specifically, the length (L3) may be about 0.5 mm to 30 mm, preferably about 5 mm to 25 mm. Further, the width (L4) may be set in consideration of both the effect of expanding the bandwidth and the prevention of the increase in size. Specifically, it is 0.5 mm to 2 mm, preferably 1 mm to 1.5 mm, and may be usually the same as the width of the high frequency side radiating element (1a) or the low frequency side radiating element (1b).
Furthermore, in the present invention, the feeding point (P1) and the ground point (P2) are positioned in the vicinity of the open portion of the slit (S). This makes it possible to resonate the slit (S) as a slit antenna having the maximum resonance frequency. Furthermore, it is preferable that the positions of the feeding point (P1) and the earth point (P2) are located at the respective corners facing the open part of the slit (S). In this case, since the feeding distance from the coaxial cable (5) to the slit (S) is shortened and feeding loss is reduced, the electric field strength induced in the slit (S) is increased and the sensitivity is improved.
On the other hand, if the slit width (L2) is too wide, the electromagnetic field induced in the slit portion (S) becomes weak. On the other hand, if the interval is too narrow, an unstable state such as interference occurs. From this, it is preferable to adjust (L2) in the range of 0.5 mm to 2.0 mm.
次に、本発明のその余の構成について説明する。
本発明においては、エレメント部（１）の各放射エレメント（１ａ）、（１ｂ）の長さは採択しようとする波長の概ね１／４の長さに設定し、他方、その幅は１ｍｍ〜５ｍｍの範囲から適宜採択する。但し、低周波側放射エレメント（１ｂ）の幅については、後述するように４ｍｍ以上で尚且つ高周波側放射エレメント（１ａ）の幅より広くする場合もある。更に、その厚さについては格段の制約はないが、０．１ｍｍ〜１ｍｍ程度で十分である。又、高周波側放射エレメント（１ａ）とグランド板（４）の縁部（４ａ）との間隔（Ｌ２）、高周波側放射エレメント（１ａ）と低周波側放射エレメント（１ｂ）との間隔、及び低周波側放射エレメント（１ｂ）と突出部（２）との間隔は、アンテナとしての安定した動作を確保するため、それぞれに１ｍｍ以上であることが好ましい。これらの間隔が０．１ｍｍ未満では干渉等の不安定現象が生じる懸念がある。
上述した放射エレメント（１ａ）、（１ｂ）の材質としては、洋白（白銅）、銅、鉄、黄銅等の導電性の金属が好ましい。これら放射エレメント（１ａ）及び（１ｂ）を含むアンテナの作成にあたっては、上記の金属の一枚板を打ち抜いて、該エレメントを、突出部（２）、短絡部（３）及びグランド板（４）と一体打ち抜き体としてもよい。あるいは、平板状絶縁性基板上に銅箔のような金属薄膜を貼り付けた状態で、該金属膜をエッチングして所望のアンテナ形状を得るのも有用である。
又、グランド板（４）については、安定したアンテナ動作を得るためには、グランド板（４）の必要最低面積（ｍｍ２）がλ／４＊λ／４（λは波長）以上を満足することが好ましい。したがって、より安定したアンテナ動作を望む場合には、スペースの許す限り、その面積を大きくすることが望ましい。短絡部（３）については、エレメント部（１）とグランド板（４）とを接続する機能を呈する限り、その形状は任意である。
給電用同軸ケーブル（５）としては、周知のフッ素樹脂被覆等の高周波同軸ケーブルが採用される。このケーブル（５）の内部導体の終端は、スリット（Ｓ）の開放部近傍、すなわち該ケーブル（５）が該開放端を跨ぐ状態で給電点（Ｐ１）に接続し、外部導体はグランド板（４）上に設けられたアースポイント（Ｐ２）に接続される。同軸ケーブル（５）を給電点（Ｐ１）及びアースポイント（Ｐ２）に接続するには、ハンダ付あるいは超音波接続等を利用すればよい。
以上の構成によるアンテナは、通常の無線ＬＡＮ等で使用される帯域においては十分な通信感度を呈するものの、携帯電話等で使用されるＷＡＮ帯域においては、十分な通信感度を呈しないことがある。この不利益を克服するには、低周波側放射エレメント（１ｂ）の幅を特に４ｍｍ以上で尚且つ高周波側放射エレメント（１ａ）の幅より広くなるように設定して、十分な電解強度を確保するのが有用である。ちなみに、図１〜図２では、このような幅設定がなされた例が示されている。
以上の態様は、スリット（Ｓ）と突出部（２）とによる共振点を最大共振周波数に設定した例であるが、該共振点は、任意且つ所望の共振周波数に設定されてもよい。又、この態様は２周波アンテナの例であるが、放射エレメントの構成本数に応じて３周波以上の多周波に展開できることは言うまでもない。更に、アンテナ自体は、上述の板金によるアンテナ以外にアンテナ取付け空間の状況に応じて立体アンテナあるいは平面アンテナに展開できることは言うまでもない。なお、スリット（Ｓ）と突出部（２）とを別の第３周波用エレメントとして設定することもでき、この場合は、図２の態様で３周波にも対応可能であることを付言しておく。
Next, the remaining configuration of the present invention will be described.
In the present invention, the length of each radiating element (1a), (1b) of the element part (1) is set to approximately 1/4 of the wavelength to be adopted, while its width is 1 mm to 5 mm. Adopted from the scope of. However, the width of the low frequency side radiating element (1b) may be 4 mm or more and wider than the width of the high frequency side radiating element (1a), as will be described later. Further, there is no particular limitation on the thickness, but about 0.1 mm to 1 mm is sufficient. Further, the distance (L2) between the high frequency side radiating element (1a) and the edge (4a) of the ground plate (4), the distance between the high frequency side radiating element (1a) and the low frequency side radiating element (1b), and the low The distance between the frequency side radiation element (1b) and the protrusion (2) is preferably 1 mm or more in order to ensure stable operation as an antenna. If these intervals are less than 0.1 mm, unstable phenomena such as interference may occur.
As a material of the radiation elements (1a) and (1b) described above, conductive metals such as white (white copper), copper, iron and brass are preferable. In producing an antenna including these radiating elements (1a) and (1b), the above-mentioned metal plate is punched out, and the elements are formed into a projecting portion (2), a short-circuit portion (3), and a ground plate (4). It is good also as an integrally punched body. Alternatively, it is also useful to obtain a desired antenna shape by etching the metal film in a state where a metal thin film such as a copper foil is attached to the flat insulating substrate.
As for the ground plate (4), in order to obtain a stable antenna operation, the required minimum area (mm2) of the ground plate (4) satisfies λ / 4 * λ / 4 (λ is a wavelength) or more. Is preferred. Therefore, when more stable antenna operation is desired, it is desirable to increase the area as long as space permits. About the short circuit part (3), as long as the function which connects an element part (1) and a ground board (4) is exhibited, the shape is arbitrary.
As the feeding coaxial cable (5), a known high-frequency coaxial cable such as a fluororesin coating is employed. The end of the inner conductor of the cable (5) is connected to the feeding point (P1) in the vicinity of the open portion of the slit (S), that is, with the cable (5) straddling the open end, and the outer conductor is connected to the ground plate ( 4) Connected to the ground point (P2) provided above. In order to connect the coaxial cable (5) to the feeding point (P1) and the earth point (P2), soldering or ultrasonic connection may be used.
The antenna having the above configuration may exhibit sufficient communication sensitivity in a band used in a normal wireless LAN or the like, but may not exhibit sufficient communication sensitivity in a WAN band used in a mobile phone or the like. In order to overcome this disadvantage, the width of the low-frequency side radiating element (1b) is set to be particularly 4 mm or more and wider than the width of the high-frequency side radiating element (1a) to ensure sufficient electrolytic strength. It is useful to do. Incidentally, FIGS. 1 and 2 show an example in which such a width setting is made.
Although the above aspect is an example in which the resonance point by the slit (S) and the protrusion (2) is set to the maximum resonance frequency, the resonance point may be set to any desired resonance frequency. This embodiment is an example of a two-frequency antenna, but it goes without saying that it can be expanded to three or more frequencies according to the number of radiating elements. Furthermore, it goes without saying that the antenna itself can be developed into a three-dimensional antenna or a planar antenna depending on the situation of the antenna mounting space other than the above-described antenna made of sheet metal. It should be noted that the slit (S) and the projecting portion (2) can be set as separate third frequency elements, and in this case, it is possible to cope with three frequencies in the manner shown in FIG. deep.
以下に、図１〜図２に示した２周波対応のアンテナを、ＷＡＮ帯域（８００ＭＨｚ／１８００ＭＨｚ）を使用する携帯電話内蔵用として適用する例について示す。
1. 放射エレメント（１ａ）、（１ｂ）、突出部（２）、短絡部（３）、及びグランド板（４）の作成
先ず、高周波側放射エレメント（１ａ）として、１８００ＭＨｚの波長に対応する長さ（Ｌ）が７０ｍｍ、幅が１ｍｍ、厚さ０．４ｍｍのエレメントを形成する。その際、高周波側放射エレメント（１ａ）とグランド板（４）の縁部（４ａ）とは１．０ｍｍの間隔（スリット幅（Ｌ２））を開けて平行に配置した。又、短絡部（３）は、長さ３ｍｍ、幅３ｍｍ、厚さ０．４ｍｍとした。
これにより、高周波用放射エレメント（１ａ）とグランド板（４）の縁部（４ａ）及び短絡部（３）とにより、幅（Ｌ２）１ｍｍ、長さ（Ｌ１）が６７ｍｍのスリット部（Ｓ）が形成された。
次に、低周波側放射エレメント（１ｂ）として、８９４ＭＨｚに対応した長さが８０ｍｍ、幅が５mm、厚さ０．４ｍｍのエレメントを、高周波側放射エレメント（１ａ）から接続部（Ａ）を経て該エレメント（１ａ）の端とは逆方向に指向するように形成した。この際、低周波側放射エレメント（１ｂ）は高周波側放射エレメント（１ａ）とは１ｍｍの間隔を開けて平行に配置した。
更に、低周波側放射エレメント（１ｂ）から接続部（Ｂ）を経て低周波側放射エレメント（１ｂ）と同方向に、長さ（Ｌ３）が２０ｍｍ、幅（Ｌ４）が１ｍｍの突出部（２）を設けた。この結果、突出部（２）とスリット部（Ｓ）とで共振周波数が１．８ＧＨｚの最大共振周波数で共振するアンテナとして機能させることができた。
このとき、エレメント部の材質は洋白（白銅）とし、一方、グランド板は、高さ８０ｍｍ、幅８０ｍｍ（低周波側エレメント（１ｂ）の長さに同じ）、厚さ０．４ｍｍの洋白とした。
又、給電点（Ｐ１）は、スリット（Ｓ）の開放部近傍、即ち図１に向かって、スリット（Ｓ）の開放部に面した高周波側放射エレメント（１ａ）の右下端角の位置に設け、一方、アースポイント（Ｐ２）の位置も、スリット（Ｓ）の開放部近傍、即ち図１に向かって、スリット（Ｓ）に面したグランド板（４）の縁（４ａ）の右上端角の位置とした。
２．アンテナの完成
最後に、給電用同軸ケーブル（５）として、外径１．１３ｍｍ、内部導体径０．２４ｍｍのフッ素樹脂（ＰＦＡ）被覆の高周波同軸ケーブルを用意し、その先端部で内部導体および外部導体を露出させた。そして、該ケーブル（５）がスリット（Ｓ）の開放部を跨ぐ形で、該内部導体の終端部を給電点（Ｐ１）に、そして該外部導体をアースポイント（Ｐ２）にそれぞれハンダにより接続することにより、図２に示す形状のパソコン内蔵用アンテナを得た。
このアンテナの帯域幅を測定したところ、図３に示すように、ＶＳＷＲが３以下の帯域が、低周波側の８２４ＭＨｚ〜９６０ＭＨｚで約３００ＭＨｚ、高周波側の１７１０ＭＨｚ〜２２００ＭＨｚで７００ＭＨｚと十分に確保されており、十分な通信特性が得られた。
Hereinafter, an example in which the antenna for two frequencies shown in FIGS. 1 to 2 is applied for use in a cellular phone using a WAN band (800 MHz / 1800 MHz) will be described.
1. Creation of radiating elements (1a), (1b), protrusion (2), short-circuited part (3), and ground plate (4) First, as a high-frequency radiating element (1a), a length corresponding to a wavelength of 1800 MHz An element having a thickness (L) of 70 mm, a width of 1 mm, and a thickness of 0.4 mm is formed. At that time, the high-frequency radiation element (1a) and the edge (4a) of the ground plate (4) were arranged in parallel with an interval of 1.0 mm (slit width (L2)). Moreover, the short circuit part (3) was 3 mm in length, 3 mm in width, and 0.4 mm in thickness.
As a result, a slit (S) having a width (L2) of 1 mm and a length (L1) of 67 mm is formed by the high-frequency radiation element (1a), the edge (4a) of the ground plate (4), and the short-circuit portion (3). Formed.
Next, as the low-frequency side radiating element (1b), an element having a length corresponding to 894 MHz of 80 mm, a width of 5 mm, and a thickness of 0.4 mm is connected from the high-frequency side radiating element (1a) through the connecting portion (A). It was formed so as to be directed in the direction opposite to the end of the element (1a). At this time, the low-frequency side radiating element (1b) was arranged in parallel with the high-frequency side radiating element (1a) at a distance of 1 mm.
Furthermore, a projecting part (2) having a length (L3) of 20 mm and a width (L4) of 1 mm in the same direction as the low frequency side radiating element (1b) from the low frequency side radiating element (1b) through the connection part (B). ). As a result, the projecting portion (2) and the slit portion (S) could function as an antenna that resonates at a maximum resonance frequency of 1.8 GHz.
At this time, the material of the element part is white (white copper), while the ground plate is 80 mm in height, 80 mm in width (same as the length of the low-frequency element (1b)), and 0.4 mm in thickness. It was.
Further, the feeding point (P1) is provided in the vicinity of the open portion of the slit (S), that is, at the position of the lower right corner of the high-frequency radiation element (1a) facing the open portion of the slit (S) toward FIG. On the other hand, the position of the earth point (P2) is also in the vicinity of the open portion of the slit (S), that is, the upper right corner of the edge (4a) of the ground plate (4) facing the slit (S) toward FIG. The position.
2. At the end of the antenna, a high-frequency coaxial cable coated with fluororesin (PFA) with an outer diameter of 1.13 mm and an inner conductor diameter of 0.24 mm is prepared as a feeding coaxial cable (5). The conductor was exposed. Then, the cable (5) straddles the open portion of the slit (S), the terminal end of the inner conductor is connected to the feeding point (P1), and the outer conductor is connected to the ground point (P2) by soldering. Thus, an antenna for incorporating a personal computer having the shape shown in FIG. 2 was obtained.
When the bandwidth of this antenna was measured, as shown in FIG. 3, a band with a VSWR of 3 or less was sufficiently secured at about 300 MHz at 824 MHz to 960 MHz on the low frequency side and 700 MHz at 1710 MHz to 2200 MHz on the high frequency side. Thus, sufficient communication characteristics were obtained.
本発明のアンテナはコンパクトで、しかも安定した通信特性を呈するので、携帯電話の他に、ＰＤＡ、或いはＶＩＣＳ等の各種情報端末機器のみならず通信機能を有した情報家電、更には自動車関連機器へも同様に利用できる。 Since the antenna of the present invention is compact and exhibits stable communication characteristics, it can be used not only for mobile phones but also for various information terminal devices such as PDA or VICS, as well as information home appliances having communication functions, and also automobile related devices. Can be used as well.
１ エレメント部
１ａ 高周波側放射エレメント
１ｂ 低周波側放射エレメント
２ 突出部
３ 短絡部
４ グランド板
４ａ グランド板（４）の縁部
５ 給電用同軸ケーブル
Ａ 高周波側放射エレメント（１ａ）と低周波側放射エレメント（１ｂ）との接続部
Ｂ 低周波側放射エレメント（１ｂ）と突出部（２）との接続部
Ｓ スリット
Ｌ 高周波側放射エレメント（１ａ）の長さ
Ｌ１ スリット（Ｓ）の長さ
Ｌ２ スリット（Ｓ）の幅
Ｌ３ 突出部（２）の長さ
Ｌ４ 突出部（２）の幅
Ｐ１
給電点
Ｐ２ アースポイント
DESCRIPTION OF
5 Coaxial cable A for feeding A Connection portion B between the high frequency side radiating element (1a) and the low frequency side radiating element (1b) Connection portion between the low frequency side radiating element (1b) and the protruding portion (2) S Slit L High frequency side Radiation element (1a) length L1 Slit (S) length L2 Slit (S) width L3 Protrusion (2) length L4 Protrusion (2) width P1
Feed point P2 Earth point
Claims (2)
A high-frequency side radiation element in which an element portion to which a feeding point is provided and a ground plate to which an earth point is provided is connected via a short-circuit portion, and the element portion is connected to the short-circuit portion, and the high-frequency side radiation A low-frequency side radiating element that extends in a folded shape from the end portion of the element, and whose end portion is directed in the opposite direction to the high-frequency side radiating element, the high-frequency side element portion and the ground plate A multi-frequency antenna having a feeding point and a ground point in the vicinity of an open portion of a slit formed by the short-circuit portion, and the antenna further radiates the low-frequency side from the starting end of the low-frequency side radiating element. parallel to the element, provided with a protrusion such as its end is directed in the same direction as the low-frequency side radiation element, adding the length and the protruding portion length of the slit By setting the length in the vicinity length of the high-frequency side radiation element, multi-frequency, wherein the projecting portion and the resonance point near the resonance point of the high-frequency side radiation element between the slit is caused Antenna.
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| JP4880439B2 (en) * | 2006-12-21 | 2012-02-22 | 日星電気株式会社 | Antenna element |
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| JP4896806B2 (en) * | 2007-04-26 | 2012-03-14 | 京セラ株式会社 | Communication equipment |
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