201114107 六、發明說明。° 【發明所屬之技術領域】 本發明相關於一種天線’尤指一種多頻段之切換式天線。 【先前技術】 隨著無線通訊科技的日益發展，行動電話、筆記型電 腦、個人數位助理（personal digital assistant, PDA)或藍牙 耳機等可攜式電子產品皆能透過内建天線來收發無線訊 號’因此能連結至無線廣域網路（Wireless Wide Area Network， WWAN)以進行資料交換，讓使用者能夠隨時瀏覽網頁或收 發電子郵件。天線的種類眾多，包含雙極天線（dipole antenna )、單極天線（monopole antenna )、平板式天線(patch antenna)、平面倒 F 型天線（planner inverted F antenna， PIFA)，和表面黏著天線(surface mountable antenna)等。 為了使全球通訊系統能夠標準化，國際電信聯盟（ITU) 制定了第三代（Third generation, 3G)通訊技術，3G通訊技 術是支援高速數據傳輸的蜂窩移動通訊技術，能夠同時傳送 聲音（通話）及數據資訊（電子郵件、即時通訊等）。另一 方面，第三代合作夥伴計晝（Third Generation Partnership 201114107201114107 VI. Description of invention. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna ‘especially a multi-band switched antenna. [Prior Art] With the development of wireless communication technology, portable electronic products such as mobile phones, notebook computers, personal digital assistants (PDAs) or Bluetooth headsets can send and receive wireless signals through built-in antennas. Therefore, it can be connected to the Wireless Wide Area Network (WWAN) for data exchange, allowing users to browse the web or send and receive emails at any time. There are many types of antennas, including dipole antennas, monopole antennas, patch antennas, planner inverted F antennas (PIFAs), and surface-adhesive antennas (surfaces). Mountable antenna) and so on. In order to standardize the global communication system, the International Telecommunication Union (ITU) has developed a third generation (Third generation, 3G) communication technology. The 3G communication technology is a cellular mobile communication technology that supports high-speed data transmission, and can simultaneously transmit sound (call) and Data information (email, instant messaging, etc.). On the other hand, the third generation partner (Third Generation Partnership 201114107)
Project, 3GPP)提出了長期演進(Long Term Evolution, LTE) 通訊技術，能夠針對無線寬頻數據設計出最佳化的性能，並 且相容於現有的全球行動通訊系統(Global System for Mobile Communication，GSM)、寬碼分碼多工存取（Wide Code DivisionMultiple Access, WCDMA)，全球行動通信系 統（Universal Mobile Telecommunications System，UMTS) 等3G網路。若通訊裝置需在有限的天線擺放空間中同時支 援 3G 頻段（例如 824〜960MHz、1710〜2170MHz、2300〜 ® 2700MHz)和 LTE 700 MHz 頻段（698〜787MHz)，則天 線操作於等效波長較長的低頻帶時往往由於低高度與小空 間時造成其頻寬的不足，使得某些頻段的收訊效果變差。故 為解決有限空間中天線效能低弱與滿足通訊系統多頻操作 的趨勢，頻帶可切換式的天線便可解決傳統天線技術的不 足。 【發明内容】 本發明提供一種多頻段之切換式天線，其包含一輻射元件和一 開關兀件。該輻射元件依據—輸入訊號以共振方式來提供_特定共 振頻帶’包含一饋入端，用來接收該輸人訊號；一第一接地端，接 至一接地電位’其中該輕射元件提供由該饋人端至該第-接地端之 第共振路禮，以及一冑二接地端，其中該輕射元件提供由 201114107 該饋入端至該第二接地端之一第二共振路徑》且該第一共振 路徑之長度大於該第二共振路徑之長度。該開關元件接於該 第二接地端，用來控制該第二接地端和該接地電位之間的訊 號流通路徑。 【實施方式】 請參考第1圖，第1圖為本發明第一實施例中一切換式 天線10之示意圖。切換式天線10包含一輻射元件12、一開 關裝置14，以及一補償元件16。輻射元件12包含一饋入端 F、一第一接地端G1，和一第二接地端G2，其主體（由饋 入端F至第一接地端G1之間的結構）採用迴圈式佈局。第 一接地端G1接至接地電位，第二接地端G2則透過開關裝 置14接至接地電位或高阻抗（開路）。補償元件16係為輻 射元件12之延伸結構，作用在於提供阻抗匹配。 切換式天線10藉由輻射元件12之結構長度設計於特定 頻帶產生共振，其中心頻率相關於天線共振路徑（從輻射元 件12之饋入端F至接地電位）之長度。當第二接地端G2 被開關裝置14開路時，輸入訊號係由輻射元件12之饋入端 F流至第一接地端G1(此時天線共振路徑由第1圖中的箭頭 L1來表示），因此輻射元件12可對應L1之長度產生一第 201114107 一電磁波共振帶B1，其中天線共振路徑口之長度為第一電 磁波共振帶B1其中心共振頻率波長的二分之一或二分之一 的整數倍。另一方面，當第二接地端G2透過開關裝置14接 至接地電位時，輸入訊號係由輻射元件12之饋入端F流至 第二接地端G2(此時天線共振路徑由第i圖中的箭頭L2來 表示），因此輻射元件12可對應[2之長度產生共振而產生 一第二電磁波共振帶B2,其電磁波共振路徑[2之長度為第 二電磁波共振帶B2其中心共振頻率波長又2的二分之一或 二分之一的整數倍。 如第1圖所示，天線共振路徑L1之長度大於天線共振 路徑L2之長度，因此第一電磁波共振帶B1之中心共振頻率 會低於第二電磁波共振帶B2之中心共振頻率。舉例來說， 本發明第一實施例可依據698〜787MHz的LTE頻段來決定 φ 輻射元件12的總長度（亦即天線共振路徑L1之長度），再 依據824〜960MHz的3G頻段來決定第二接地端G2的位置 (亦即天線共振路徑L2之長度）。透過控制開關裝置14， 天線10即能輕易地在3G頻段和LTE頻段之間切換運作。 第2圖和第3圖說明了本發明天線1〇之運作，第2圖 為當第二接地端G2接至接地電位時天線1〇之電壓駐波比 (Voltage Standing Wave Ratio, VSWR)圖，而第 3 圖為當第 201114107 二接地端G2接至高阻抗時天線10之電壓駐波比圖。在2圖 和第3圖中，縱軸代表阻抗匹配，橫軸代表頻率。當第二接 地端G2接至接地電位時，天線10能提供操作頻率介於824 〜960MHz的低頻第二電磁波共振帶B2，此時天線10運作 於3G頻段。當第二接地端G2接至高阻抗時，天線10能提 供操作頻率介於698〜787MHz的低頻第一電磁波共振帶 B1，此時天線10運作於LTE頻段。 請參考第4圖，第4圖為本發明第二實施例中一切換式 天線20之示意圖。切換式天線20和切換式天線10結構類 似，同樣包含一輻射元件12和一補償元件16，不同之處在 於切換式天線20包含複數個開關裝置（第4圖顯示兩個開 關裝置13和15之實施例）。輻射元件12包含一饋入端F、 一第一接地端G卜一第二接地端G2,和一第三接地端G3， 其主體（由饋入端F至第一接地端G1之間的結構）採用迴 圈式佈局。第一接地端G1接至接地電位，第二接地端G2 透過開關裝置13接至接地電位或高阻抗（開路），而第三 接地端G3則透過開關裝置15接至接地電位或高阻抗（開 路）。補償元件16係為輻射元件12之延伸結構，作用在於 提供阻抗匹配。 201114107 切換式天線10藉由輻射元件12之長度設計於特定頻帶 產生共振，其令心頻率相關於天線共振路徑（從輻射元件12 之饋入端F至接地電位）之長度。當第二接地端G2和第三 接地端G3分別被開關裝置13和15開路時，輸入訊號係由 輻射元件12之饋入端F流至第一接地端G1 (此時天線共振 路徑由第4圖中的箭頭L1來表示），因此輻射元件12可對 應L1之長度產生一第一電磁波共振帶B1，其中天線共振路 徑L1之長度為第一電磁波共振帶B1其中心共振頻率波長的 * 二分之一或二分之一的整數倍。當第二接地端G2透過開關 裝置13接至接地電位而第三接地端G3被開關裝置15開路 時，輸入訊號係由輻射元件12之饋入端F流至第二接地端 G2(此時天線共振路徑由第4圖中的箭頭L2來表示），因 此輻射元件12可對應L2之長度產生一第二電磁波共振帶 B2，其中天線共振路徑L2之長度為第二電磁波共振帶B2 其中心共振頻率波長的二分之一或二分之一的整數倍。當第 • 三接地端G3透過開關裝置15接至接地電位時，輸入訊號係 由輻射元件12之饋入端F流至第三接地端G3 (此時天線共 振路徑由第4圖中的箭頭L3來表示），因此輻射元件12可 對應L3之長度產生一第三電磁波共振帶B3，其中天線共振 路徑L3之長度為第二電磁波共振帶B3其中心共振頻率波長 的二分之一或二分之一的整數倍。換而言之，本發明可輕易 地在多個頻段之間切換。 201114107 請參考第5圖，第5圖為本發明第三實施例中一切換式 天線30之示意圖。切換式天線30包含一輻射元件32和一 開關裝置14。輻射元件32包含一饋入端F、一開路端Ο、 一第一接地端G1，和一第二接地端G2，其主體採用 IFA(inverted F antenna)設計。第一接地端G1接至接地電位， 第二接地端G2則透過開關裝置14接至接地電位或高阻抗 (開路）。切換式天線30藉由輻射元件32產生特定電磁波 共振帶，其中心頻率相關於天線共振路徑（從輻射元件32 之開路端0至接地電位）之長度。當第二接地端G2被開關 裝置14開路時，輸入訊號係由輻射元件12之饋入端F流至 第一接地端G1 (此時天線共振路徑由第5圖中的箭頭L1來 表示），因此輻射元件32可共振產生一第一電磁波共振帶 B1，其中天線共振路徑L1之長度為第一電磁波共振帶B1 其中心共振頻率波長λ!的四分之一或四分之一的奇數倍。 另一方面，當第二接地端G2透過開關裝置14接至接地電位 時，輸入訊號係由輻射元件32之饋入端F流至第二接地端 G2 (此時天線共振路徑由第5圖中的箭頭L2來表示），因 此輻射元件32可共振產生一第二電磁波共振帶Β2，其中電 磁波共振路徑L2之長度為第二電磁波共振帶Β2其中心共振 頻率波長λ2的四分之一或四分之一的奇數倍。 201114107 如第5圖所示，天線共振路徑L1之長度大於天線共振 路徑L2之長度，因此第一電磁波共振帶B1之中心共振頻率 會低於第二電磁波共振帶B 2之1f7心共振頻率。舉例來s尤’ 本發明第三實施例可依據698〜787MHz的LTE頻段來決定 輻射元件32每端的長度（亦即天線共振路徑L1之長度）， 再依據824〜960MHz的3G頻段來決定第二接地端G2的位 置（亦即天線共振路徑L2之長度）。透過控制開關裝置14， 天線30即能在3G頻段和LTE頻段之間切換運作。 在本發明中，開關裝置13〜15可為單極雙投開關（single pole double throw, SPDT)或其它具類似功能之元件。第1 圖和第4圖所示之迴圈式輻射元件以及第5圖所示之IFA式 輻射元件僅為本發明之實施例，並不限定本發明之範疇。 • 以上所述僅為本發明之較佳實施例，凡依本發明申請專 利範圍所做之均等變化與修飾，皆應屬本發明之涵蓋範圍。 【圖式簡單說明】 第1圖為本發明第一實施例中一切換式天線之示意圖。 第2圖為本發明之天線在3G頻段運作時之電壓駐波比圖。 第3圖為本發明之天線在LTE頻段運作時之電壓駐波比圖。 201114107 第4圖為本發明第二實施例中一切換式天線之示意圖。 第5圖為本發明第三實施例中一切換式天線之示意圖。 【主要元件符號說明】 12 輻射元件 13 〜15 開關裝置 16 補償元件 10 、 20 、 30 切換式天線 F 饋入端 G1 〜G3 接地端 0 開路端 12Project, 3GPP) proposes Long Term Evolution (LTE) communication technology, which can optimize performance for wireless broadband data and is compatible with existing Global System for Mobile Communication (GSM). , Wide Code Division Multiple Access (WCDMA), Global Mobile Telecommunications System (UMTS) and other 3G networks. If the communication device needs to support 3G frequency bands (such as 824~960MHz, 1710~2170MHz, 2300~ ® 2700MHz) and LTE 700 MHz frequency band (698~787MHz) in a limited antenna placement space, the antenna operates at the equivalent wavelength. In the long low frequency band, the bandwidth is often insufficient due to low altitude and small space, which makes the receiving effect of some frequency bands worse. Therefore, in order to solve the trend of low antenna performance in a limited space and to meet the multi-frequency operation of the communication system, the band switchable antenna can solve the shortage of the conventional antenna technology. SUMMARY OF THE INVENTION The present invention provides a multi-band switched antenna that includes a radiating element and a switching element. The radiating element is provided in a resonant manner according to the input signal. The specific resonant frequency band includes a feed end for receiving the input signal, and a first ground end connected to a ground potential 'where the light-emitting element is provided by a first resonant path of the feed end to the first ground terminal, and a second ground end, wherein the light projecting element provides a second resonant path from the feed end to the second ground end of 201114107 and the The length of the first resonant path is greater than the length of the second resonant path. The switching element is connected to the second ground end for controlling a signal flow path between the second ground and the ground potential. [Embodiment] Please refer to Fig. 1, which is a schematic diagram of a switched antenna 10 according to a first embodiment of the present invention. The switched antenna 10 includes a radiating element 12, a switching device 14, and a compensating element 16. The radiating element 12 includes a feed terminal F, a first ground terminal G1, and a second ground terminal G2, and the main body (the structure from the feed terminal F to the first ground terminal G1) adopts a loop layout. The first ground terminal G1 is connected to the ground potential, and the second ground terminal G2 is connected to the ground potential or the high impedance (open circuit) through the switching device 14. The compensating element 16 is an extension of the radiating element 12 that serves to provide impedance matching. The switched antenna 10 is designed to resonate in a particular frequency band by the structural length of the radiating element 12, the center frequency of which is related to the length of the antenna resonant path (from the feed terminal F of the radiating element 12 to the ground potential). When the second ground terminal G2 is opened by the switching device 14, the input signal flows from the feeding terminal F of the radiating element 12 to the first ground terminal G1 (in this case, the antenna resonance path is represented by an arrow L1 in FIG. 1). Therefore, the radiating element 12 can generate a 201114107 electromagnetic wave resonance band B1 corresponding to the length of the L1, wherein the length of the antenna resonant path port is one-half or one-half the integer of the wavelength of the central resonant frequency of the first electromagnetic wave resonant band B1. Times. On the other hand, when the second ground terminal G2 is connected to the ground potential through the switching device 14, the input signal flows from the feeding terminal F of the radiating element 12 to the second ground terminal G2 (at this time, the antenna resonance path is from the i-th diagram) The arrow L2 is shown), so the radiating element 12 can generate a second electromagnetic wave resonance band B2 corresponding to the length of [2], and the electromagnetic wave resonance path [2 is the length of the second electromagnetic wave resonance band B2 whose center resonance frequency wavelength is again One-half or one-half of an integer multiple of two. As shown in Fig. 1, the length of the antenna resonance path L1 is larger than the length of the antenna resonance path L2, so that the center resonance frequency of the first electromagnetic wave resonance band B1 is lower than the center resonance frequency of the second electromagnetic wave resonance band B2. For example, the first embodiment of the present invention can determine the total length of the φ radiating element 12 (that is, the length of the antenna resonant path L1) according to the LTE frequency band of 698 to 787 MHz, and then determine the second according to the 3G frequency band of 824 to 960 MHz. The position of the ground terminal G2 (that is, the length of the antenna resonance path L2). By controlling the switching device 14, the antenna 10 can be easily switched between the 3G band and the LTE band. 2 and 3 illustrate the operation of the antenna 1〇 of the present invention, and FIG. 2 is a diagram of the voltage standing wave ratio (VSWR) of the antenna 1 when the second ground terminal G2 is connected to the ground potential. The third figure shows the voltage standing wave ratio of the antenna 10 when the ground terminal G2 of the 201114107 is connected to a high impedance. In the 2 and 3 figures, the vertical axis represents impedance matching and the horizontal axis represents frequency. When the second ground terminal G2 is connected to the ground potential, the antenna 10 can provide the low frequency second electromagnetic wave resonance band B2 whose operating frequency is between 824 and 960 MHz, and the antenna 10 operates in the 3G frequency band. When the second ground terminal G2 is connected to a high impedance, the antenna 10 can provide a low frequency first electromagnetic wave resonance band B1 having an operating frequency of 698 to 787 MHz, and the antenna 10 operates in the LTE band. Please refer to FIG. 4, which is a schematic diagram of a switched antenna 20 according to a second embodiment of the present invention. The switched antenna 20 and the switched antenna 10 are similar in structure, and also include a radiating element 12 and a compensating element 16, except that the switched antenna 20 includes a plurality of switching devices (Fig. 4 shows two switching devices 13 and 15). Example). The radiating element 12 includes a feeding end F, a first grounding end G, a second grounding end G2, and a third grounding end G3, the main body (the structure between the feeding end F and the first grounding end G1) ) Adopt a loop layout. The first ground terminal G1 is connected to the ground potential, the second ground terminal G2 is connected to the ground potential or the high impedance (open circuit) through the switching device 13, and the third ground terminal G3 is connected to the ground potential or the high impedance through the switching device 15 (open circuit) ). The compensating element 16 is an extension of the radiating element 12 and serves to provide impedance matching. The 201114107 switched antenna 10 is designed to generate a resonance in a particular frequency band by the length of the radiating element 12, which correlates the heart frequency to the length of the antenna resonant path (from the feed terminal F of the radiating element 12 to the ground potential). When the second ground terminal G2 and the third ground terminal G3 are opened by the switching devices 13 and 15, respectively, the input signal flows from the feeding terminal F of the radiating element 12 to the first ground terminal G1 (at this time, the antenna resonance path is 4th) The arrow L1 in the figure is shown), so that the radiating element 12 can generate a first electromagnetic wave resonance band B1 corresponding to the length of L1, wherein the length of the antenna resonance path L1 is the dichotomy of the center wavelength of the first electromagnetic wave resonance band B1. One or one-half of an integer multiple. When the second ground terminal G2 is connected to the ground potential through the switching device 13, and the third ground terminal G3 is opened by the switching device 15, the input signal flows from the feeding terminal F of the radiating element 12 to the second ground terminal G2 (the antenna at this time) The resonant path is represented by an arrow L2 in FIG. 4, so that the radiating element 12 can generate a second electromagnetic wave resonant band B2 corresponding to the length of L2, wherein the length of the antenna resonant path L2 is the second electromagnetic wave resonant band B2, its central resonant frequency One-half of the wavelength or an integer multiple of one-half. When the third ground terminal G3 is connected to the ground potential through the switching device 15, the input signal flows from the feeding terminal F of the radiating element 12 to the third ground terminal G3 (at this time, the antenna resonance path is indicated by the arrow L3 in FIG. 4). The radiation element 12 can generate a third electromagnetic wave resonance band B3 corresponding to the length of L3, wherein the length of the antenna resonance path L3 is one-half or two-half of the wavelength of the central resonance frequency of the second electromagnetic wave resonance band B3. An integer multiple of one. In other words, the present invention can be easily switched between a plurality of frequency bands. 201114107 Please refer to FIG. 5, which is a schematic diagram of a switched antenna 30 according to a third embodiment of the present invention. The switched antenna 30 includes a radiating element 32 and a switching device 14. The radiating element 32 includes a feed end F, an open end Ο, a first ground end G1, and a second ground end G2, the main body of which is designed by an IFA (inverted F antenna). The first ground terminal G1 is connected to the ground potential, and the second ground terminal G2 is connected to the ground potential or the high impedance (open circuit) through the switching device 14. The switched antenna 30 generates a specific electromagnetic wave resonance band by the radiating element 32, the center frequency of which is related to the length of the antenna resonant path (from the open end 0 of the radiating element 32 to the ground potential). When the second ground terminal G2 is opened by the switching device 14, the input signal flows from the feeding terminal F of the radiating element 12 to the first ground terminal G1 (at this time, the antenna resonance path is represented by an arrow L1 in FIG. 5). Therefore, the radiating element 32 can resonate to generate a first electromagnetic wave resonance band B1, wherein the length of the antenna resonance path L1 is an odd multiple of a quarter or a quarter of the center wavelength of the first electromagnetic wave resonance band B1 . On the other hand, when the second ground terminal G2 is connected to the ground potential through the switching device 14, the input signal flows from the feeding terminal F of the radiating element 32 to the second ground terminal G2 (the antenna resonant path is in FIG. 5 The arrow L2 is represented by the arrow L2, so that the radiating element 32 can resonate to generate a second electromagnetic wave resonance band ,2, wherein the length of the electromagnetic wave resonance path L2 is a quarter or a quarter of the wavelength λ2 of the center of the second electromagnetic wave resonance band Β2 An odd multiple of one. 201114107 As shown in Fig. 5, the length of the antenna resonance path L1 is larger than the length of the antenna resonance path L2, so the center resonance frequency of the first electromagnetic wave resonance band B1 is lower than the 1f7 core resonance frequency of the second electromagnetic wave resonance band B2. For example, the third embodiment of the present invention can determine the length of each end of the radiating element 32 (that is, the length of the antenna resonant path L1) according to the LTE frequency band of 698 to 787 MHz, and then determine the second according to the 3G frequency band of 824 to 960 MHz. The position of the ground terminal G2 (that is, the length of the antenna resonance path L2). By controlling the switching device 14, the antenna 30 can be switched between the 3G band and the LTE band. In the present invention, the switching devices 13 to 15 may be single pole double throw (SPDT) or other components having similar functions. The loop type radiating element shown in Figs. 1 and 4 and the IFA type radiating element shown in Fig. 5 are only examples of the present invention, and do not limit the scope of the present invention. The above are only the preferred embodiments of the present invention, and all changes and modifications made to the patent scope of the present invention are intended to be within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a switched antenna according to a first embodiment of the present invention. Figure 2 is a diagram showing the voltage standing wave ratio of the antenna of the present invention operating in the 3G band. Figure 3 is a graph showing the voltage standing wave ratio of the antenna of the present invention operating in the LTE band. 201114107 FIG. 4 is a schematic diagram of a switched antenna according to a second embodiment of the present invention. Figure 5 is a schematic diagram of a switched antenna in a third embodiment of the present invention. [Main component symbol description] 12 Radiating components 13 to 15 Switching devices 16 Compensating components 10, 20, 30 Switching antenna F Feeding terminal G1 to G3 Grounding terminal 0 Opening terminal 12