JP4044502B2

JP4044502B2 - Dual band antenna

Info

Publication number: JP4044502B2
Application number: JP2003330088A
Authority: JP
Inventors: 元珠竇
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 2003-09-22
Filing date: 2003-09-22
Publication date: 2008-02-06
Anticipated expiration: 2023-09-22
Also published as: JP2005101744A

Description

本発明は、２種類の周波数帯域（バンド）の信号波の送信や受信が可能で車載用通信機器等に用いて好適な小型のデュアルバンドアンテナに関する。 The present invention relates to a small dual-band antenna that can transmit and receive signal waves in two types of frequency bands and is suitable for use in in-vehicle communication devices.

小型化に適したデュアルバンドアンテナとして、従来、放射導体板に切欠きを設けることによって高低２種類の周波数で共振可能とした逆Ｆ型アンテナが提案されている（例えば、特許文献１参照）。 As a dual-band antenna suitable for miniaturization, an inverted-F antenna that can resonate at two types of high and low frequencies by providing a notch in a radiation conductor plate has been proposed (for example, see Patent Document 1).

図６はかかる従来例を示す説明図であり、同図に示す逆Ｆ型のデュアルバンドアンテナ１は、放射導体板２に長方形状の切欠き４を形成することによって、第１の周波数ｆ₁に共振するＬ字形導体片２ａと、第１の周波数ｆ₁よりも高周波な第２の周波数ｆ₂に共振する矩形導体片２ｂとを備えている。放射導体板２の一辺端は短絡導体板３に連続しており、短絡導体板３は接地導体板５上に立設されて放射導体板２と該接地導体板５とを短絡している。放射導体板２は全面が接地導体板５と所定の間隔を存して対向しており、放射導体板２の所定位置に給電ピン６がはんだ付けされている。この給電ピン６は、接地導体板５とは非接触で図示せぬ給電回路に接続されている。 FIG. 6 is an explanatory view showing such a conventional example. The inverted F-type dual band antenna 1 shown in FIG. 6 has a first frequency f ₁ by forming a rectangular cutout 4 in the radiation conductor plate 2. It includes a L-shaped conductor piece 2a resonating, and a rectangular conductor piece 2b resonating frequency f ₂ of the high-frequency second than the first frequency f ₁ in. One end of the radiation conductor plate 2 is continuous with the short-circuit conductor plate 3, and the short-circuit conductor plate 3 stands on the ground conductor plate 5 to short-circuit the radiation conductor plate 2 and the ground conductor plate 5. The entire surface of the radiating conductor plate 2 is opposed to the ground conductor plate 5 with a predetermined interval, and a feed pin 6 is soldered to a predetermined position of the radiating conductor plate 2. The power supply pin 6 is connected to a power supply circuit (not shown) without contacting the ground conductor plate 5.

このように概略構成された従来のデュアルバンドアンテナ１は、Ｌ字形導体片２ａの延出方向に沿った長さ寸法が第１の周波数ｆ₁に対応する共振長λ₁の約４分の１に設定され、かつ、延出寸法が短い矩形導体片２ｂの長さ寸法が第２の周波数ｆ₂に対応する共振長λ₂（ただしλ₂＜λ₁）の約４分の１に設定されている。それゆえ、給電ピン６を介して放射導体板２に所定の高周波電力を供給することにより、各導体片２ａ，２ｂを互いに異なる周波数で共振させることができ、高低２種類の周波数帯域の信号波が送受信可能となる。 Thus schematically configured conventional dual band antenna 1 is about a quarter of the resonance length lambda ₁ of the extending length dimension along the direction of the L-shaped conductor piece 2a corresponds to the first frequency f ₁ And the length dimension of the rectangular conductor piece 2b having a short extension dimension is set to about one quarter of the resonance length λ ₂ (where λ ₂ <λ ₁ ) corresponding to the second frequency f _2. ing. Therefore, by supplying a predetermined high frequency power to the radiation conductor plate 2 via the feed pin 6, the conductor pieces 2a and 2b can be resonated at different frequencies, and signal waves in two types of high and low frequency bands can be obtained. Can be sent and received.

また、この種の逆Ｆ型のデュアルバンドアンテナにおいて、小型化を促進するために延出寸法が長いローバンド用の放射導体を蛇行するメアンダ形状に形成するという技術も広く採用されており、こうすることで該放射導体を流れる電流の経路がメアンダ形状に沿ったものとなって電気長が稼げるため、アンテナ全体の小型化が促進しやすくなる。
特開平１０−９３３３２号公報（第２−３頁、図１） In addition, in this type of inverted-F dual-band antenna, a technique of forming a low-band radiation conductor having a long extension in a meander shape meandering in order to promote downsizing is widely adopted. As a result, the path of the current flowing through the radiating conductor follows the meander shape, and the electrical length can be increased. Therefore, it is easy to promote downsizing of the entire antenna.
JP-A-10-93332 (page 2-3, FIG. 1)

ところで、車載用のデュアルバンドアンテナにおいては、近年小型化の要求がますます高まっているが、一般的にアンテナ装置は小型化に伴って共振可能な帯域幅が狭くなるという特性を有し、特に共振長が長いローバンドのときにその傾向が顕著なため、上述した従来のデュアルバンドアンテナ１の小型化を促進した場合、ローバンド使用時に所望の帯域幅が確保できなくなる虞があった。ここで、帯域幅とは、リターンロス（反射減衰量）が例えば−１０ｄＢ以下となる周波数範囲であって、デュアルバンドアンテナはハイバンドとローバンドの信号波のそれぞれについて、使用周波数帯域よりも広い帯域幅を確保しておかねばならないため、このことが小型化の促進を妨げる要因となっていた。 By the way, in a dual-band antenna for in-vehicle use, the demand for downsizing has been increasing in recent years, but in general, an antenna device has a characteristic that a resonating bandwidth is narrowed with downsizing. Since the tendency is remarkable when the resonance length is a low band, when the downsizing of the conventional dual-band antenna 1 described above is promoted, there is a possibility that a desired bandwidth cannot be secured when using the low band. Here, the bandwidth is a frequency range in which the return loss (reflection loss amount) is, for example, −10 dB or less, and the dual-band antenna has a wider band than the used frequency band for each of the high-band and low-band signal waves. Since the width must be secured, this has been a factor that hinders the promotion of downsizing.

また、デュアルバンドアンテナの小型化を推し進めるために、ローバンド用の放射導体をメアンダ形状に形成した場合には、該放射導体の電流経路中に至近距離で逆向きに流れる電流が発生し、これら逆向き電流に起因する電界は相殺されやすいため放射効率の低下を余儀なくされる。そして、一般的にアンテナ装置は放射効率が低下するほど小型化に伴う狭帯域化が顕著となるため、結局、放射導体をメアンダ形状にしてデュアルバンドアンテナの小型化を推し進めると、所望の帯域幅を確保することは一層困難となる。 In addition, when the low-band radiating conductor is formed in a meander shape in order to promote the miniaturization of the dual-band antenna, a current that flows in the opposite direction at a close distance is generated in the current path of the radiating conductor. Since the electric field caused by the direction current is easily canceled, the radiation efficiency is inevitably lowered. In general, as the radiation efficiency of the antenna device decreases, the narrowing of the band accompanying the downsizing becomes more conspicuous. Consequently, when the miniaturization of the dual-band antenna is promoted by making the radiation conductor into a meander shape, a desired bandwidth is obtained. It is even more difficult to ensure

さらにまた、従来のデュアルバンドアンテナ１では、偏波方向が放射導体板２に対して直交する電波（例えば垂直偏波）だけでなく、偏波方向が放射導体板２に対して平行な電波（例えば水平偏波）も放射されるため、偏波純度が低く、その分、特定の偏波方向の電波の利得が低減して高利得化が図りにくいという問題もあった。 Furthermore, in the conventional dual-band antenna 1, not only radio waves whose polarization direction is orthogonal to the radiation conductor plate 2 (for example, vertical polarization), but also radio waves whose polarization direction is parallel to the radiation conductor plate 2 ( For example, since the polarization purity is low, the gain of radio waves in a specific polarization direction is reduced, and it is difficult to achieve high gain.

本発明は、このような従来技術の実情に鑑みてなされたもので、その目的は、ローバンドの信号波の帯域幅を犠牲にすることなく小型化が促進できると共に、特定の偏波方向の電波に対する利得が高く車載用アンテナとして好適なデュアルバンドアンテナを提供することにある。 The present invention has been made in view of the actual situation of the prior art, and an object thereof is to facilitate downsizing without sacrificing the bandwidth of a low-band signal wave, and to achieve radio waves in a specific polarization direction. Is to provide a dual-band antenna suitable for a vehicle-mounted antenna.

上述した目的を達成するため、本発明のデュアルバンドアンテナでは、接地導体を有する支持基板上に搭載された筒状の絶縁性基体と、一対の分割導体板をスリットを存して並設してなり前記絶縁性基体の開口端を蓋閉する位置に装着された第１の放射導体板と、前記絶縁性基体の内部空間に立設されて上端部が一方の前記分割導体板の前記スリット側の外縁と連続している給電導体板および第１の短絡導体板と、前記絶縁性基体の内部空間に立設されて上端部が他方の前記分割導体板の前記スリット側の外縁と連続している第２の短絡導体板と、上端部が前記接地導体に対して略平行に延びており下端部が前記給電導体板に接続されて前記絶縁性基体の内部空間に立設され高さ位置が前記第１の放射導体板よりも低い第２の放射導体板とを備え、前記給電導体板の下端部を給電回路に接続し、かつ、前記第１および第２の短絡導体板の下端部を前記接地導体に接続し、前記第２の短絡導体板を前記スリットを介して前記給電導体板と斜めに対向するように配置して、前記第２の短絡導体板を前記給電導体板と電磁結合させた状態で前記第１の放射導体板を第１の周波数で共振させると共に、前記第１の周波数よりも高周波な第２の周波数で前記第２の放射導体板を共振させるように構成した。 In order to achieve the above-described object, in the dual-band antenna of the present invention, a cylindrical insulating base mounted on a support substrate having a ground conductor and a pair of divided conductor plates are arranged side by side with slits. And a first radiating conductor plate mounted at a position where the opening end of the insulating substrate is closed, and an upper end of the first radiating conductor plate standing in the inner space of the insulating substrate, the slit side of one of the divided conductor plates The first and second shorting conductor plates that are continuous with the outer edge of the insulating base, and the upper end portion of the feeding conductor plate and the first short-circuit conductor plate that is continuous with the outer edge of the other divided conductor plate on the slit side A second short-circuited conductor plate and an upper end extending substantially parallel to the ground conductor, a lower end connected to the feeder conductor plate, and standing in the internal space of the insulating base, the height position being A second radiating conductor plate lower than the first radiating conductor plate; For example, to connect the lower end of the feed conductor plate to the feed circuit, and the lower end portion of the first and second short-circuiting conductor connected to the ground conductor, the slits the second short-circuiting conductor arranged so as to face diagonally and the feeding conductive plate through the resonance the first radiation conductor plate the second short-circuiting conductor while being electromagnetically coupled to the feed conductor plate at a first frequency And the second radiating conductor plate is configured to resonate at a second frequency higher than the first frequency.

このように構成されたデュアルバンドアンテナは、給電導体板の上端部に連続している一方の分割導体板を励振すると、給電導体板と電磁結合する第２の短絡導体板を介して他方の分割導体板が励振されるため、この他方の分割導体板を無給電アンテナの放射素子として動作させることができ、異なる二つの共振点が設定可能となる。そして、これら二つの共振点の共振周波数の差は、給電導体板と第２の短絡導体板との電磁結合の度合いを適宜調整することによって増減できるため、ローバンド用の第１の放射導体板全体の大きさを縮小してデュアルバンドアンテナの小型化を促進しても、リターンロスが所定値以下となる周波数範囲を広げて所望の帯域幅を確保することが容易となる。また、励振時の一対の分割導体板には、互いに逆向きに流れる同等の大きさの電流が生起されて一方の電界と他方の電界とがキャンセルされるため、偏波方向が第１の放射導体板に対して平行な電波はほとんど放射されなくなり、その分、偏波方向が第１の放射導体板に対して直交する電波が強く放射されることになって偏波純度が高まり、それゆえ特定の偏波方向の電波（例えば垂直偏波）に対する利得を大幅に向上させることができる。なお、ハイバンド用の第２の放射導体板は励振時に１／４波長のモノポールアンテナとして動作するため、その垂直偏波の利得は高く、高さ寸法も低く抑えることができる。 In the dual-band antenna configured as described above, when one split conductor plate continuous to the upper end portion of the feed conductor plate is excited, the other split antenna is coupled via the second short-circuit conductor plate electromagnetically coupled to the feed conductor plate. Since the conductor plate is excited, the other divided conductor plate can be operated as a radiating element of the parasitic antenna, and two different resonance points can be set. The difference between the resonance frequencies of these two resonance points can be increased or decreased by appropriately adjusting the degree of electromagnetic coupling between the power supply conductor plate and the second short-circuit conductor plate. Even if the size of the dual-band antenna is reduced by reducing the size of the antenna, it is easy to secure a desired bandwidth by expanding the frequency range in which the return loss is a predetermined value or less. In addition, currents of the same magnitude flowing in opposite directions are generated in the pair of divided conductor plates at the time of excitation, so that one electric field and the other electric field are canceled. The radio wave parallel to the conductor plate is hardly radiated, and accordingly, the radio wave whose polarization direction is orthogonal to the first radiating conductor plate is strongly radiated, thereby increasing the polarization purity. The gain for radio waves in a specific polarization direction (for example, vertical polarization) can be greatly improved. Since the second radiating conductor plate for high band operates as a quarter-wave monopole antenna during excitation, the vertical polarization gain is high and the height dimension can be kept low.

かかる構成のデュアルバンドアンテナは、前記一対の分割導体板にそれぞれ略同形な窓部が開設されていることが好ましく、これにより、一対の分割導体板に供給される電流がそれぞれの窓部の周縁に沿って流れるようになるため、各分割導体板を小型化しても所望の共振電気長が確保しやすくなる。それゆえ、各分割導体板をメアンダ形状に形成する必要がなくなって放射効率が高まり、小型化に伴う狭帯域化を抑制する効果が一層高まる。 In the dual-band antenna having such a configuration, it is preferable that windows of substantially the same shape are formed in the pair of divided conductor plates, respectively, so that the current supplied to the pair of divided conductor plates is the peripheral edge of each window portion. Therefore, even if each divided conductor plate is downsized, it is easy to ensure a desired resonance electric length. Therefore, it is not necessary to form each divided conductor plate in a meander shape, the radiation efficiency is increased, and the effect of suppressing the narrow band accompanying the downsizing is further enhanced.

また、かかる構成のデュアルバンドアンテナは、前記第２の放射導体板の上端部が前記接地導体に対して略平行に延びていることが好ましく、これにより、モノポールアンテナとして動作する第２の放射導体板がトップローディングの状態になるため、その高さ寸法を大幅に低減することができる。 In the dual-band antenna having such a configuration, it is preferable that an upper end portion of the second radiating conductor plate extends substantially in parallel with the ground conductor, whereby the second radiating element that operates as a monopole antenna is provided. Since the conductor plate is in a top loading state, its height dimension can be greatly reduced.

本発明のデュアルバンドアンテナは、一方の分割導体板を励振すると他方の分割導体板が無給電アンテナの放射素子として動作するため、ローバンド用の第１の放射導体板全体の大きさを縮小して小型化を促進しても所望の帯域幅を確保することが容易となる。また、励振時の一対の分割導体板には互いに逆向きに流れる同等の大きさの電流が生起されるため、偏波方向が第１の放射導体板に対して平行な電波はほとんど放射されなくなって偏波純度が高まり、特定の偏波方向の電波に対する利得を大幅に向上させることができる。 In the dual-band antenna of the present invention, when one of the divided conductor plates is excited, the other divided conductor plate operates as a radiating element of the parasitic antenna. Therefore, the size of the first low-band first radiating conductor plate is reduced. Even if miniaturization is promoted, it becomes easy to secure a desired bandwidth. Further, since currents of the same magnitudes flowing in opposite directions are generated in the pair of divided conductor plates at the time of excitation, radio waves whose polarization direction is parallel to the first radiation conductor plate are hardly radiated. Thus, the polarization purity is improved, and the gain for a radio wave in a specific polarization direction can be greatly improved.

また、かかるデュアルバンドアンテナにおいて、一対の分割導体板にそれぞれ略同形な窓部が開設されている場合には、各分割導体板を小型化しても必要な共振電気長が確保しやすくなるため、各分割導体板をメアンダ形状に形成する必要がなくなって放射効率が高まり、小型化に伴う狭帯域化を抑制する効果が一層高まる。 Also, in such a dual-band antenna, when a substantially identical window is opened in each of the pair of divided conductor plates, it becomes easy to ensure the necessary resonant electrical length even if each divided conductor plate is downsized. It is not necessary to form each divided conductor plate in a meander shape, so that the radiation efficiency is increased, and the effect of suppressing the narrow band accompanying the downsizing is further enhanced.

以下、発明の実施の形態を図面を参照して説明すると、図１は本発明の実施形態例に係るデュアルバンドアンテナの斜視図、図２は絶縁性基体を図示省略して該アンテナの各導体板を示す説明図、図３は該アンテナの平面図、図４は該アンテナのスリットに沿う縦断面図、図５は該アンテナの周波数に応じたリターンロスを示す特性図である。 1 is a perspective view of a dual-band antenna according to an embodiment of the present invention. FIG. 2 is a perspective view of a conductor of the antenna with an insulating base omitted. FIG. 3 is a plan view of the antenna, FIG. 4 is a longitudinal sectional view along the slit of the antenna, and FIG. 5 is a characteristic diagram showing return loss according to the frequency of the antenna.

これらの図に示すデュアルバンドアンテナ１０は、車載用アンテナとして使用されるものであって、ローバンド（例えば８００ＭＨｚのＡＭＰＳ帯）とハイバンド（例えば１．９ＧＨｚのＰＣＳ帯）の信号波の送受信が選択的に行える小型のアンテナ装置である。このデュアルバンドアンテナ１０は、裏面全面に接地導体２０を設けた支持基板２１と、この支持基板２１上に載置固定された角筒状の絶縁性基体１１と、一対の分割導体板１３，１４をスリットＳを存して並設してなり絶縁性基体１１の開口端１１ａを蓋閉する位置に装着された第１の放射導体板１２と、絶縁性基体１１の内部空間に立設されて上端部が分割導体板１３のスリットＳ側の外縁と連続している給電導体板１５および第１の短絡導体板１６と、絶縁性基体１１の内部空間に立設されて上端部が分割導体板１４のスリットＳ側の外縁と連続している第２の短絡導体板１７と、下端部が給電導体板１５に接続されて絶縁性基体１１の内部空間に立設され高さ位置が第１の放射導体板１２よりも低い第２の放射導体板１８とによって概略構成されている。 The dual-band antenna 10 shown in these figures is used as an in-vehicle antenna, and transmission / reception of low-band (for example, 800 MHz AMPS band) and high-band (for example, 1.9 GHz PCS band) signals is selected. It is a small antenna device that can be performed automatically. The dual-band antenna 10 includes a support substrate 21 having a ground conductor 20 provided on the entire back surface, a rectangular tubular insulating base 11 placed and fixed on the support substrate 21, and a pair of divided conductor plates 13 and 14. Are arranged side by side with slits S and are erected in the internal space of the insulating substrate 11 and the first radiation conductor plate 12 mounted at a position where the opening end 11a of the insulating substrate 11 is closed. The upper end portion is erected in the internal space of the insulating base 11 with the feeding conductor plate 15 and the first short-circuit conductor plate 16, which are continuous with the outer edge of the split conductor plate 13 on the slit S side, and the upper end portion is the split conductor plate. 14, the second short-circuit conductor plate 17 that is continuous with the outer edge of the slit S side, and the lower end portion is connected to the power supply conductor plate 15 and is erected in the internal space of the insulating base 11, and the height position is the first. By a second radiation conductor plate 18 which is lower than the radiation conductor plate 12. It is substantially constituted.

ここで、絶縁性基体１１は合成樹脂等の誘電材料からなる成形品で、この絶縁性基体１１の四隅は支持基板２１の裏面からねじ止め固定されている。また、第１および第２の放射導体板１２，１８と給電導体板１５と第１および第２の短絡導体板１６，１７はいずれも銅板等の導電性金属板からなり、分割導体板１３と給電導体板１５と第１の短絡導体板１６と第２の放射導体板１８とが一体形成されていると共に、分割導体板１４と第２の短絡導体板１７とが一体形成されている。つまり、分割導体板１３の外縁から下向きに給電導体板１５と第１の短絡導体板１６とが延設されて、給電導体板１５の下端から橋絡部１９を経て第２の放射導体板１８が上向きに延設されており、さらに第２の放射導体板１８の上端部１８ａが接地導体２０と略平行に延設されている。また、分割導体板１４の外縁から下向きに第２の短絡導体板１７が延設されている。 Here, the insulating substrate 11 is a molded product made of a dielectric material such as a synthetic resin, and the four corners of the insulating substrate 11 are fixed by screws from the back surface of the support substrate 21. The first and second radiating conductor plates 12 and 18, the feeding conductor plate 15, and the first and second short-circuit conductor plates 16 and 17 are all made of a conductive metal plate such as a copper plate. The feeding conductor plate 15, the first short-circuit conductor plate 16, and the second radiation conductor plate 18 are integrally formed, and the divided conductor plate 14 and the second short-circuit conductor plate 17 are integrally formed. That is, the feed conductor plate 15 and the first short-circuit conductor plate 16 are extended downward from the outer edge of the divided conductor plate 13, and the second radiation conductor plate 18 passes from the lower end of the feed conductor plate 15 through the bridging portion 19. Is extended upward, and the upper end portion 18 a of the second radiation conductor plate 18 is extended substantially parallel to the ground conductor 20. A second short-circuit conductor plate 17 is extended downward from the outer edge of the divided conductor plate 14.

第１の放射導体板１２を構成している一対の分割導体板１３，１４にはそれぞれ窓部１３ａ，１４ａが開設されていると共に、絶縁性基体１１の開口端１１ａの周縁に沿って延びる折曲片１３ｂ，１４ｂが突設されており、これらの折曲片１３ｂ，１４ｂは絶縁性基体１１の側壁に外嵌されている。給電導体板１５は分割導体板１３のスリットＳ側の外縁の略中央から延設されており、この給電導体板１５の近傍から略平行に第１の短絡導体板１６が延設されている。給電導体板１５の下端と第２の放射導体板１８の下端とを連結している橋絡部１９は、支持基板２１上で給電ランドに半田付けされており、この給電ランドはコプラナ線路２２を経由して図示せぬ給電回路に接続されている。また、第１および第２の短絡導体板１６，１７の下端は、支持基板２１に設けられたスルーホールを介して接地導体２０に接続されている。この第２の短絡導体板１７はスリットＳを介して給電導体板１５と斜めに対向するように配置させてあるので、給電導体板１５が給電されると、第２の短絡導体板１７には電磁結合によって誘導電流が流れる。 The pair of divided conductor plates 13 and 14 constituting the first radiating conductor plate 12 are provided with windows 13a and 14a, respectively, and folded along the periphery of the opening end 11a of the insulating base 11. Bending pieces 13 b and 14 b are provided so as to protrude from the side walls of the insulating base 11. The power supply conductor plate 15 extends from the substantially center of the outer edge of the split conductor plate 13 on the slit S side, and a first short-circuit conductor plate 16 extends from the vicinity of the power supply conductor plate 15 substantially in parallel. A bridging portion 19 that connects the lower end of the feed conductor plate 15 and the lower end of the second radiation conductor plate 18 is soldered to the feed land on the support substrate 21, and the feed land connects the coplanar line 22. Via a power supply circuit (not shown). The lower ends of the first and second short-circuit conductor plates 16 and 17 are connected to the ground conductor 20 through through holes provided in the support substrate 21. Since the second short-circuit conductor plate 17 is disposed so as to be diagonally opposed to the power supply conductor plate 15 through the slit S, when the power supply conductor plate 15 is fed, the second short-circuit conductor plate 17 An induced current flows due to electromagnetic coupling.

このように構成されたデュアルバンドアンテナ１０は、橋絡部１９に周波数の異なる高低２種類の高周波電力を選択的に供給することによって、第１の放射導体板１２と第２の放射導体板１８を選択的に励振することができ、第１の放射導体板１２の励振時には分割導体板１４が無給電アンテナの放射素子として動作する。すなわち、ローバンド用の第１の周波数ｆ₁の高周波電力を給電導体板１５に供給することによって、分割導体板１３を逆Ｆ型アンテナの放射素子と同様に共振させることができると共に、給電導体板１５との電磁結合により第２の短絡導体板１７に誘導電流が流れるため分割導体板１４も共振させることができる。また、ハイバンド用の第２の周波数ｆ₂（ただしｆ₂＞ｆ₁）の高周波電力を第２の放射導体板１８に供給することによって、この第２の放射導体板１８をモノポールアンテナとして共振させることができる。 The dual-band antenna 10 configured in this way selectively supplies two types of high and low-frequency high-frequency powers having different frequencies to the bridge portion 19, whereby the first radiating conductor plate 12 and the second radiating conductor plate 18. Can be selectively excited, and when the first radiating conductor plate 12 is excited, the divided conductor plate 14 operates as a radiating element of the parasitic antenna. That is, by supplying high-frequency power of the first frequency f ₁ for low band to the feed conductor plate 15, the divided conductor plate 13 can resonate similarly to the radiating element of the inverted F-type antenna, and the feed conductor plate Since the induced current flows through the second short-circuit conductor plate 17 due to the electromagnetic coupling with 15, the divided conductor plate 14 can also resonate. Further, by supplying high-frequency power of the second frequency f ₂ for high band (where f ₂ > f ₁ ) to the second radiating conductor plate 18, the second radiating conductor plate 18 is used as a monopole antenna. It can resonate.

したがって、このデュアルバンドアンテナ１０の周波数に応じたリターンロス（反射減衰量）は図５に実線で示すような曲線となり、ローバンドにおいて異なる二つの共振点Ａ，Ｂが発生している。ここで、共振点Ａ，Ｂに対応する共振周波数は、給電導体板１５と第２の短絡導体板１７との相対位置、つまり両導体板１５，１７の電磁結合の度合いに応じて決定される。それゆえ、両導体板１５，１７の相対位置を適宜選択して、共振点Ａに対応する共振周波数ｆ(A）から共振点Ｂに対応する共振周波数ｆ(B）までの間の任意の周波数でリターンロスが−１０ｄＢ以下となり、かつ、共振周波数ｆ(A）と共振周波数ｆ(B）との周波数の差が極力大きくなるように設計しておけば、ローバンド使用時に帯域幅を大幅に広げることができ、小型化に伴う狭帯域化を抑制する効果が高まる。 Therefore, the return loss (reflection loss amount) corresponding to the frequency of the dual-band antenna 10 is a curve as shown by a solid line in FIG. 5, and two different resonance points A and B are generated in the low band. Here, the resonance frequency corresponding to the resonance points A and B is determined according to the relative position between the power supply conductor plate 15 and the second short-circuit conductor plate 17, that is, the degree of electromagnetic coupling between the two conductor plates 15 and 17. . Therefore, an arbitrary frequency between the resonance frequency f (A) corresponding to the resonance point A and the resonance frequency f (B) corresponding to the resonance point B by appropriately selecting the relative positions of the two conductor plates 15 and 17. If the return loss is -10 dB or less and the frequency difference between the resonance frequency f (A) and the resonance frequency f (B) is designed to be as large as possible, the bandwidth will be greatly increased when using the low band. Therefore, the effect of suppressing the narrowing of the band accompanying the downsizing is enhanced.

例えば、給電導体板１５と第２の短絡導体板１７を極力近接させて電磁結合を著しく強くした場合、共振周波数ｆ(A）と共振周波数ｆ(B）はほぼ同等の値になるため帯域幅は狭くなるが、両導体板１５，１７を遠ざけて電磁結合を弱めていけば、共振周波数ｆ(A）と共振周波数ｆ(B）との周波数差は次第に増大していき、それに伴い帯域幅も広くなっていく。しかし、両導体板１５，１７の電磁結合が弱くなりすぎると、共振周波数ｆ(A）と共振周波数ｆ(B）間の所定の周波数の信号波に対してリターンロスが−１０ｄＢを上回ってしまうため、広帯域化とはならない。結局、給電導体板１５と第２の短絡導体板１８の電磁結合の度合いを適宜調整して、図５に示すような共振点Ａ，Ｂを設定した場合に、リターンロスが−１０ｄＢ以下の周波数範囲が最大となって広帯域化に最も有利であることがわかる。なお、図５に破線で示す曲線は、ローバンドにおいて共振点が一つしかない場合のリターンロスを示す比較例であり、本実施形態例に比べてローバンド使用時の帯域幅がかなり狭くなっている。また、帯域幅は共振周波数が高くなるほど広くなるので、ハイバンドにおいては図５に示すように十分な帯域幅が得られている。 For example, when the power supply conductor plate 15 and the second short-circuit conductor plate 17 are brought close to each other as much as possible and the electromagnetic coupling is remarkably strengthened, the resonance frequency f (A) and the resonance frequency f (B) are substantially equal to each other. However, the frequency difference between the resonance frequency f (A) and the resonance frequency f (B) gradually increases as the electromagnetic coupling is weakened by moving the two conductor plates 15 and 17 away from each other. Will also become wider. However, if the electromagnetic coupling between the two conductor plates 15 and 17 becomes too weak, the return loss exceeds −10 dB for a signal wave having a predetermined frequency between the resonance frequency f (A) and the resonance frequency f (B). Therefore, it does not become a broad band. After all, when the degree of electromagnetic coupling between the power supply conductor plate 15 and the second short-circuit conductor plate 18 is appropriately adjusted to set resonance points A and B as shown in FIG. 5, the return loss is a frequency of −10 dB or less. It can be seen that the range is maximized and is most advantageous for widening the bandwidth. In addition, the curve shown with a broken line in FIG. 5 is a comparative example showing a return loss when there is only one resonance point in the low band, and the bandwidth when using the low band is considerably narrower than in this embodiment. . Further, since the bandwidth becomes wider as the resonance frequency becomes higher, a sufficient bandwidth is obtained in the high band as shown in FIG.

また、このデュアルバンドアンテナ１０においては、第１の放射導体板１２を構成する一対の分割導体板１３，１４に窓部１３ａ，１４ａが開設されているので、ローバンド使用時に各分割導体板１３，１４に供給される電流がそれぞれの窓部１３ａ，１４ａの周縁に沿って流れるようになり、それゆえ各分割導体板１３，１４を大きくしなくても所望の共振電気長が確保しやすくなっている。したがって、共振電気長を確保するために各分割導体板１３，１４をメアンダ形状に形成する必要がなくなって放射効率が高まり、小型化に伴う狭帯域化を抑制する効果が一層高まっている。 In the dual band antenna 10, since the windows 13a and 14a are provided in the pair of divided conductor plates 13 and 14 constituting the first radiating conductor plate 12, each divided conductor plate 13 and The current supplied to 14 flows along the peripheries of the respective window portions 13a and 14a. Therefore, it is easy to secure a desired resonance electric length without enlarging the divided conductor plates 13 and 14. Yes. Therefore, it is not necessary to form each of the divided conductor plates 13 and 14 in a meander shape in order to ensure the resonance electric length, so that the radiation efficiency is increased, and the effect of suppressing the narrow band accompanying the downsizing is further increased.

また、このデュアルバンドアンテナ１０では、ローバンド使用時に、第１の放射導体板１２を構成する一対の分割導体板１３，１４に互いに逆向きに流れる同等の大きさの電流が生起され、一方の電界と他方の電界とがキャンセルされるため、偏波方向が第１の放射導体板１２に対して平行な電波はほとんど放射されなくなり、その分、偏波方向が第１の放射導体板１２に対して直交する電波（垂直偏波）が強く放射されることになって、偏波純度が高まる。それゆえ、ローバンド使用時に、車載用の通信機器に要求される垂直偏波の利得を大幅に向上させることができる。なお、ハイバンド用の第２の放射導体板１８は励振時にモノポールアンテナとして動作するため、垂直偏波の利得は高い。 In the dual band antenna 10, when the low band is used, currents of the same magnitude that flow in opposite directions are generated in the pair of divided conductor plates 13 and 14 constituting the first radiating conductor plate 12, and one electric field is generated. And the other electric field are canceled, radio waves whose polarization direction is parallel to the first radiation conductor plate 12 are hardly radiated, and accordingly, the polarization direction is relative to the first radiation conductor plate 12. Thus, orthogonal radio waves (vertically polarized waves) are radiated strongly, and the polarization purity is increased. Therefore, when using the low band, the gain of vertical polarization required for the in-vehicle communication device can be greatly improved. Note that the second radiating conductor plate 18 for high band operates as a monopole antenna during excitation, and therefore the gain of vertical polarization is high.

また、このデュアルバンドアンテナ１０においては、第２の放射導体板１８の上端部１８ａが接地導体２０に対して略平行に延設されており、モノポールアンテナとして動作する第２の放射導体板１８がトップローディングの状態になっているため、高さ寸法を大幅に低減できてアンテナ全体の低背化が促進しやすくなっている。 In this dual-band antenna 10, the upper end portion 18a of the second radiating conductor plate 18 extends substantially in parallel to the ground conductor 20, and the second radiating conductor plate 18 that operates as a monopole antenna. Is in a top-loading state, the height dimension can be greatly reduced, and the overall height of the antenna can be easily reduced.

このように本実施形態例に係るデュアルバンドアンテナ１０は、ローバンド使用時に広帯域化に最も有利な二つの共振点Ａ，Ｂを設定することができるため、アンテナ全体の小型化を促進してもローバンド使用時の帯域幅が不所望に狭くなる虞が少ない。また、周知のようにハイバンド使用時には小型化を促進しても帯域幅が不所望に狭くなる虞は少ない。それゆえ、このデュアルバンドアンテナ１０は、ハイバンドとローバンドのそれぞれについて使用周波数帯域よりも広い帯域幅が容易に確保できるようになり、帯域幅を犠牲にすることなくアンテナ全体の小型化を促進することができる。また、このデュアルバンドアンテナ１０は、ローバンド使用時に一対の分割導体板１３，１４に供給される電流がそれぞれの窓部１３ａ，１４ａの周縁に沿って流れるため、各分割導体板１３，１４をメアンダ形状に形成しなくても所望の共振電気長が確保しやすく、それゆえ小型化に伴う狭帯域化を抑制する効果が一層高まっている。さらにまた、このデュアルバンドアンテナ１０のローバンド使用時には、一対の分割導体板１３，１４を逆向きに流れる電流に起因する電界のキャンセルによって、偏波方向が第１の放射導体板１２に対して直交する電波が強く放射されるため、車載用の通信機器に要求される垂直偏波の利得を大幅に向上させることができる。しかも、このデュアルバンドアンテナ１０のハイバンド用の第２の放射導体板１８は、上端部１８ａによってトップローディングの状態になっているため、高さ寸法が大幅に低減できてアンテナ全体の低背化が促進しやすい。 As described above, the dual-band antenna 10 according to the present embodiment can set the two resonance points A and B that are most advantageous for widening the band when the low-band is used. There is little risk that the bandwidth in use is undesirably narrowed. Further, as is well known, when a high band is used, there is little possibility that the bandwidth is undesirably narrowed even if miniaturization is promoted. Therefore, the dual-band antenna 10 can easily secure a bandwidth wider than the use frequency band for each of the high band and the low band, and promotes downsizing of the entire antenna without sacrificing the bandwidth. be able to. In addition, since the current supplied to the pair of divided conductor plates 13 and 14 flows along the peripheral edges of the respective window portions 13a and 14a when the dual band antenna 10 is used in the low band, each of the divided conductor plates 13 and 14 is provided with a meander. Even if it is not formed into a shape, it is easy to ensure a desired resonance electric length, and therefore, the effect of suppressing the narrow band accompanying the downsizing is further increased. Furthermore, when the dual band antenna 10 is used in a low band, the polarization direction is orthogonal to the first radiation conductor plate 12 by canceling the electric field caused by the current flowing in the opposite direction through the pair of divided conductor plates 13 and 14. Therefore, the vertical polarization gain required for in-vehicle communication equipment can be greatly improved. In addition, since the high-band second radiating conductor plate 18 of the dual-band antenna 10 is in a top-loading state by the upper end portion 18a, the height dimension can be greatly reduced and the overall height of the antenna is reduced. Is easy to promote.

なお、ローバンド使用時に広帯域化に最も有利な二つの共振点Ａ，Ｂを設定しておけば、第１の放射導体板１２を構成する一対の分割導体板１３，１４に窓部１３ａ，１４ａが開設されていない場合でも、帯域幅を犠牲にすることなくアンテナ全体の小型化を促進する効果は大きい。 If the two resonance points A and B that are most advantageous for widening the band are set when the low band is used, the window portions 13a and 14a are formed on the pair of divided conductor plates 13 and 14 constituting the first radiation conductor plate 12. Even if it is not established, the effect of promoting downsizing of the entire antenna without sacrificing bandwidth is great.

本発明の実施形態例に係るデュアルバンドアンテナの斜視図である。It is a perspective view of the dual band antenna concerning the example of an embodiment of the present invention. 該アンテナの各導体板を示す説明図である。It is explanatory drawing which shows each conductor board of this antenna. 該アンテナの平面図である。It is a top view of this antenna. 該アンテナのスリットに沿う縦断面図である。It is a longitudinal cross-sectional view along the slit of this antenna. 該アンテナの周波数に応じたリターンロスを示す特性図である。It is a characteristic view which shows the return loss according to the frequency of this antenna. 従来例に係る逆Ｆ型のデュアルバンドアンテナを示す説明図である。It is explanatory drawing which shows the inverted F type dual band antenna which concerns on a prior art example.

Explanation of symbols

１０デュアルバンドアンテナ
１１絶縁性基体
１１ａ開口端
１２第１の放射導体板
１３，１４分割導体板
１３ａ，１４ａ窓部
１５給電導体板
１６第１の短絡導体板
１７第２の短絡導体板
１８第２の放射導体板
２０接地導体
２１支持基板
Ｓスリット DESCRIPTION OF SYMBOLS 10 Dual band antenna 11 Insulating base | substrate 11a Open end 12 1st radiation | emission conductor plate 13,14 Division | segmentation conductor plate 13a, 14a Window part 15 Feeding conductor plate 16 1st short circuit conductor plate 17 2nd short circuit conductor plate 18 2nd Radiation conductor plate 20 Ground conductor 21 Support substrate S Slit

Claims

A cylindrical insulating base mounted on a support substrate having a grounding conductor and a pair of divided conductor plates arranged side by side with slits are mounted at positions where the opening ends of the insulating base are closed. A first radiating conductor plate, a feeding conductor plate standing in the internal space of the insulating base and having an upper end continuous with the outer edge on the slit side of one of the divided conductor plates, and a first short-circuit conductor A plate, a second short-circuit conductor plate standing in the internal space of the insulating base and having an upper end continuous with the outer edge on the slit side of the other divided conductor plate, and an upper end of the ground conductor A second radiating conductor plate extending substantially in parallel to the lower radiating conductor plate and having a lower end connected to the feeding conductor plate and standing in the internal space of the insulating base and having a height position lower than that of the first radiating conductor plate. And connecting the lower end of the power supply conductor plate to a power supply circuit, and Connect the lower end of the beauty second short-circuiting conductor to the ground conductor, said second short-circuiting conductor arranged so as to face diagonally and the feeding conductive plate through the slit, the second The first radiating conductor plate is resonated at a first frequency with the short-circuit conductor plate being electromagnetically coupled to the feeding conductor plate, and the second frequency is higher than the first frequency. A dual band antenna characterized in that the radiating conductor plate is resonated.

2. The dual-band antenna according to claim 1, wherein a window having substantially the same shape is formed in each of the pair of divided conductor plates.