1345374 -_____ ‘ | 100年05月04日核正肖^·^ 六、發明說明： 【發明所屬之技術領城】 [0001] 本發明涉及一種慮波器，尤其涉及一種低通滤波器。 【先前技術】 [0002] 在設計各種不同應用的無線通訊產品時，低通濾波器係 被廣泛使用的一種元件，其主要功能係用來過濾掉訊號 的高頻諧波或者一些高頻雜訊。低通濾波器通常以其在 通帶（pa ssband)的插入損耗（insertion loss)以及在 止帶（stopband)的抑制能力（rejecti〇n)來表示其效能 • 。濾波器在止帶的抑制能力取決於其傳輸零點，傳輸零 點愈多的濾波器在止帶的抑制能力有著愈好的表現。 ' [0003] 請參照圖4 ’揭示了一種傳統的低通濾波器40。該低通渡 波器40包括輸入端400、輸出端420、高阻抗傳輸部440 、矩形第一低阻抗傳輪部460以及矩形第二低阻抗傳輸部 480。輸入端400係用於饋入電磁波訊號，輸出端420係 用於饋出電磁波訊號。高阻抗傳輸部440與輸入端400和 • 輸出端420電性連接。第一低阻抗傳輸部460與輸入端 400和高阻抗傳輸部440的一端電性連接，第二低阻抗傳 輸部480與輸出420和尚阻抗傳輸部440的另一端電性 連接。第一低阻抗傳輸部460和第二低阻抗傳輸部480相 對設置，且兩矩形的長邊耦合。該低通濾波器4〇的總長 為8. 69mm，總寬為3. 53mm，面積為30. 67mm2。 [0004] 請參照圖5 ’揭示了該低通濾波器40之測試圖。由圖5可 知，低通濾波器40只產生一個傳輸零點，可見該低通濾 波器40在止帶的抑制能力不好，其濾波效能不佳。 097110172 表單编號AOlOi 苐3頁/共〗4頁 1003154897-0 1345374 ____ 100年05月04日養正替換頁 [0005] 同時，該低通濾波器40的面積過大，不符合無線通訊產 品朝向輕、薄、短、小方向發展之趨勢。故，如何在兼 顧濾波器效能的前提下，同時將濾波器之所佔的面積減 小乃當今渡波器設計之一大挑戰。 【發明内容】 [0006] 有鑒於此，需提供一種具有良好濾波效能和較小面積的 低通渡波器。 [0007] 一種低通濾波器，包括輸入端、輸出端、高阻抗傳輸線 、第一低阻抗傳輸線以及第二低阻抗傳輸線。輸入端用 於饋入電磁波訊號。輸出端用於饋出電磁波訊號。高阻 抗傳輸線分別與該輸入端和該輸出端電性連接。第一低 阻抗傳輸線與該輸入端和該高阻抗傳輸線的一端電性連 接，第二低阻抗傳輸線與該輸出端和該高阻抗傳輸線另 一端電性連接。其中，該第一低阻抗傳輸線和該第二低 阻抗傳輸線排列於高阻抗傳輸線的一側並均呈三角形。 [0008] 本發明實施方式所提供之低通濾波器，利用多個低阻抗 傳輸線排列於高阻抗傳輸線的一側並均呈三角形，增強 了低阻抗傳輸線之間的耦合，使得低通濾波器在增加傳 輸零點的同時使傳輸零點更為靠近截止頻率。 【實施方式】 [0009] 參閱圖1，所示為本發明實施方式中之低通濾波器10之結 構示意圖。 [0010] 在本實施方式中，低通濾波器10印刷於電路板20上。低 通濾波器10包括輸入端100、輸出端120、高阻抗傳輸線 097110172 表單編號A0101 第4頁/共14頁 1003154897-0 1345374 100年05月04日修正替換頁 140、第一低阻抗傳輸線160以及第二低阻抗傳輸線180 [0011] 輸入端100係用於饋入電磁波訊號，輸出端120係用於饋 出電磁波訊號。輸入端100與輸出端120為低通濾波器10 之50歐姆匹配阻抗。在本實施方式中，輸入端100與輸出 端120位於同一直線。 [0012] 高阻抗傳輸線140呈蜿蜒狀，其包括與輸入端100電性連 接的第一連接端142、與輸出端120電性連接的第二連接 • 端144及蜿蜒部146。蜿蜒部146位於第一連接端142和第 二連接端144之間並與它們相連，即高阻抗傳輸線140從 輸入端100向輸出端120蜿蜒延伸。 [0013] 因高阻抗傳輸線140具有蜿蜒部146，從而減小了低通濾 波器1 0的面積。 [0014] 在其它實施方式中，高阻抗傳輸線140的蜿蜒部146的彎 折次數可以改變。 [0015] 第一低阻抗傳輸線160與第二低阻抗傳輸線180均呈直角 三角形，且兩三角形的斜邊耦合。第一低阻抗傳輸線160 包括第三連接端162，該第三連接端162位於第一低阻抗 傳輸線160三角形斜邊的一端部，第一低阻抗傳輸線160 三角形斜邊的另一端為自由端。第三連接端162與高阻抗 傳輸線140的第一連接端142和輸入端100電性連接。第 二低阻抗傳輸線180包括第四連接端182，該第四連接端 182位於第二低阻抗傳輸線180三角形的直角處，從而輸 入端100與第一低阻抗傳輸線160的連接位置為三角形斜 097110172 表單編號A0101 第5頁/共14頁 1003154897-0 100年05月04曰 邊的-端部’而輪出端12Q與第二低吨傳輸線18〇的連 接位置為三角形的直角處。第二低阻抗傳輪線刚三角形 斜邊的兩端部為自由端。第四連接端182與高祖抗傳輸線 140的第二連接端144及輸出端12〇電性連接。 請參照圖2 ’所示為本發明料效電路圖。圖2之電感l係 由本案之高峨傳輸線14〇所等效形成，電容⑽由第一 低阻抗傳㈣U0與電路㈣之接地金屬面所等效形成， 電容C3係由第二低阻抗傳輸線18〇與電路板2〇之接地金屬 面所等效形成，電容C2係由第—低阻抗傳輸線㈣與第二 低阻抗傳輸線180耦合形成。 在本實施方式中，低通渡波㈣的總長為5. 13mm，總寬 為3. 78nm ’面積為19· 39mm2 ’與傳統的低通渡波器綱目 比’低通遽波器1 〇的面積減小了 3 6. 8 %。 請參閱圖3 ’所示為經電磁模擬所得本發明實施方式中低 通濾波器10之測試圖。圖中橫軸表示通過低通濾波器1〇 的訊號的頻率（單位：GHz)，縱軸表示幅度（單位元： dB)，象限區包括透射之散射參數（s_parameter:S21) 的幅度以及反射之散射參數（S-parameter : si 1)的幅度 。透射之散射參數（S21)表示通過低通低通濾波器1〇的訊 號的輸入功率與訊號的輸出功率之間的關係，其相應的 數學函數為：S21 (dB) =l〇Lg (輸出功率/輸入功率） 。在低通濾波器10的訊號傳輸過程中，訊號的部份功率 被反射回訊號源。被反射回訊號源的功率稱為反射功率 。通過低通濾波器10的訊號的輸入功率與訊號的反射功 (dB) =l〇Lg 1003154897-0 率之間的關係，其相應的數學函數為：S11 表單編號A0101 第6頁/共14頁 1345374 _ * ' 100年05月04日修正替換頁 (反射功率/入射功率）。 [0019] 由圖3可知，本發明實施方式中之低通濾波器10具有良好 之濾波效能。從曲線IS21 |可觀察到，通帶頻段與衰減頻 段間形成陡的“過渡坡”，並且在通帶頻段範圍内的訊 號的插入損耗接近0。同時從曲線丨Sll|可觀察到，在通 帶頻段内的訊號反射損耗絕對值大於10，而在通帶頻段 外，則訊號反射損耗絕對值小於10。 [0020] 在本實施方式中，低通濾波器10藉由輸入端100與第一低 • 阻抗傳輸線160的連接位置為三角形斜邊的一端部而輸出 端120與第二低阻抗傳輸線180的連接位置為三角形的直 角處產生兩個傳輸零點，從而低通濾波器1 0在止帶的抑 制能力較好，具有良好的濾波效能。 [0021] 在本實施方式中，利用第一低阻抗傳輸線160和第二低阻 抗傳輸線180之間的斜邊耦合，從而增加了第一低阻抗傳 輸線160和第二低阻抗傳輸線180耦合所形成的電容值， 這不僅提高了低通濾波器10的衰減速度，同時使得低通 濾波器10的傳輸零點更為靠近截止頻率。而且，在通帶 頻段内，具有較低之損耗值。 [0022] 综上所述，本發明符合發明專利要件，爰依法提出專利 申請。惟，以上所述者僅為本發明之較佳實施例，舉凡 熟悉本案技藝之人士，在爰依本案發明精神所作之等效 修飾或變化，皆應包含於以下之申請專利範圍内。 【圖式簡單說明】 [0023] 圖1為本發明實施方式中低通濾波器之結構示意圖。 097110172 表單編號A0101 第7頁/共14頁 1003154897-0 1345374 100年05月〇/日·桉正替換頁 [0024] 圖2為本發明的等效電路圖。 [0025] 圖3為本發明實施方式中低通濾波器之測試圖。 [0026] 圖4為習知低通渡波器之結構示意圖。 [0027] 圖5為習知低通濾波器之測試圖。 【主要元件符號說明】 [0028] 低通濾波器 10 [0029] 電路板 20 [0030] 輸入端 100 [0031] 輸出端 120 [0032] 南阻抗傳輸線 140 [0033] 第一連接端 142 [0034] 第二連接端 144 [0035] 蜿蜒部 146 [0036] 第一低阻抗傳輸線 160 [0037] 第三連接端 162 [0038] 第二低阻抗傳輸線 180 [0039] 第四連接端 1821345374 -_____ ‘ | May 4th, 2004, Nuclear Zheng ^^^ VI. Description of the invention: [Technology of the invention] [0001] The present invention relates to a wave filter, and more particularly to a low-pass filter. [Prior Art] [0002] When designing wireless communication products for various applications, a low-pass filter is a widely used component whose main function is to filter out high-frequency harmonics of signals or some high-frequency noise. . The low-pass filter usually expresses its performance with its insertion loss in the pass band and the stopband suppression capability (rejecti〇n). The rejection of the filter in the stop band depends on its transmission zero point, and the more transmission points, the better the rejection of the filter in the stop band. [0003] A conventional low pass filter 40 is disclosed with reference to FIG. The low pass waver 40 includes an input terminal 400, an output terminal 420, a high impedance transmission portion 440, a rectangular first low impedance transmission portion 460, and a rectangular second low impedance transmission portion 480. The input terminal 400 is for feeding electromagnetic wave signals, and the output terminal 420 is for feeding electromagnetic wave signals. The high impedance transmission portion 440 is electrically connected to the input terminal 400 and the output terminal 420. The first low-impedance transmission portion 460 is electrically connected to one end of the input terminal 400 and the high-impedance transmission portion 440, and the second low-impedance transmission portion 480 is electrically connected to the other end of the output 420 and the impedance transmission portion 440. The first low impedance transmission portion 460 and the second low impedance transmission portion 480 are oppositely disposed, and the long sides of the two rectangles are coupled. The total length of the low-pass filter 4 is 8.69 mm, the total width is 3.53 mm, and the area is 30.67 mm2. [0004] A test diagram of the low pass filter 40 is disclosed with reference to FIG. As can be seen from Fig. 5, the low-pass filter 40 generates only one transmission zero point. It can be seen that the low-pass filter 40 has poor suppression capability at the stop band, and the filtering performance is not good. 097110172 Form number AOlOi 苐 3 pages / total 〖 4 pages 1003154897-0 1345374 ____ 100 years of May 4th, the replacement page [0005] At the same time, the area of the low-pass filter 40 is too large, does not meet the wireless communication products towards light The trend of thin, short and small development. Therefore, how to reduce the area occupied by the filter while balancing the performance of the filter is one of the major challenges in today's wave design. SUMMARY OF THE INVENTION [0006] In view of the above, it is desirable to provide a low-pass waver with good filtering performance and a small area. A low pass filter includes an input end, an output end, a high impedance transmission line, a first low impedance transmission line, and a second low impedance transmission line. The input is used to feed electromagnetic signals. The output is used to feed out electromagnetic wave signals. The high impedance transmission line is electrically connected to the input end and the output end, respectively. The first low-impedance transmission line is electrically connected to the input end and one end of the high-impedance transmission line, and the second low-impedance transmission line is electrically connected to the output end and the other end of the high-impedance transmission line. The first low-impedance transmission line and the second low-impedance transmission line are arranged on one side of the high-impedance transmission line and are each triangular. [0008] The low-pass filter provided by the embodiment of the present invention uses a plurality of low-impedance transmission lines arranged on one side of the high-impedance transmission line and is triangular, thereby enhancing coupling between the low-impedance transmission lines, so that the low-pass filter is Increase the transmission zero while bringing the transmission zero closer to the cutoff frequency. [Embodiment] Referring to Fig. 1, there is shown a schematic structural view of a low pass filter 10 in an embodiment of the present invention. [0010] In the present embodiment, the low pass filter 10 is printed on the circuit board 20. The low pass filter 10 includes an input terminal 100, an output terminal 120, a high impedance transmission line 097110172, a form number A0101, a fourth page, a total of 14 pages, 1003154897-0, 1345374, a revised replacement page 140, a first low impedance transmission line 160, and The second low impedance transmission line 180 [0011] The input terminal 100 is used to feed electromagnetic wave signals, and the output terminal 120 is used to feed out electromagnetic wave signals. Input 100 and output 120 are 50 ohm matching impedances of low pass filter 10. In the present embodiment, the input terminal 100 and the output terminal 120 are in the same straight line. [0012] The high-impedance transmission line 140 has a meandering shape, and includes a first connecting end 142 electrically connected to the input end 100, and a second connecting end 144 and a crotch portion 146 electrically connected to the output end 120. The jaw 146 is located between and connected to the first connection end 142 and the second connection end 144, i.e., the high impedance transmission line 140 extends from the input end 100 to the output end 120蜿蜒. [0013] Since the high impedance transmission line 140 has the crotch portion 146, the area of the low pass filter 10 is reduced. [0014] In other embodiments, the number of bends of the crotch portion 146 of the high impedance transmission line 140 can vary. [0015] The first low-impedance transmission line 160 and the second low-impedance transmission line 180 are both at right angles to the triangle, and the oblique sides of the two triangles are coupled. The first low impedance transmission line 160 includes a third connection end 162 located at one end of the triangular hypotenuse of the first low impedance transmission line 160, and the other end of the triangular hypotenuse of the first low impedance transmission line 160 is a free end. The third connection end 162 is electrically connected to the first connection end 142 and the input end 100 of the high impedance transmission line 140. The second low-impedance transmission line 180 includes a fourth connection end 182 located at a right angle of the triangle of the second low-impedance transmission line 180 such that the connection position of the input end 100 and the first low-impedance transmission line 160 is a triangle oblique 097110172. No. A0101 Page 5 of 14 1003154897-0 100 years of May 04 曰 edge-end' and the connection position of the wheel end 12Q and the second low-ton transmission line 18〇 is a right angle of the triangle. The second low-impedance transmission line is just a triangle. Both ends of the hypotenuse are free ends. The fourth connection end 182 is electrically connected to the second connection end 144 and the output end 12 of the Gaozu anti-transmission line 140. Please refer to FIG. 2' for the material effect circuit diagram of the present invention. The inductor l of FIG. 2 is formed by the high-frequency transmission line 14〇 of the present invention. The capacitor (10) is formed by the first low-impedance transmission (4) U0 and the grounded metal surface of the circuit (4), and the capacitor C3 is composed of the second low-impedance transmission line 18. The 〇 is formed equivalent to the grounded metal surface of the circuit board 2, and the capacitor C2 is formed by coupling the first low impedance transmission line (4) with the second low impedance transmission line 180. In the present embodiment, the total length of the low-pass wave (4) is 5.13 mm, and the total width is 3.78 nm 'area is 19.39 mm2' and the area of the conventional low-pass waver is smaller than that of the low-pass chopper 1 〇 Smaller 3 6.8%. Please refer to FIG. 3' for a test diagram of the low pass filter 10 in the embodiment of the present invention obtained by electromagnetic simulation. In the figure, the horizontal axis represents the frequency (unit: GHz) of the signal passing through the low-pass filter 1〇, the vertical axis represents the amplitude (unit: dB), and the quadrant region includes the amplitude of the transmission scattering parameter (s_parameter: S21) and the reflection The magnitude of the scattering parameter (S-parameter: si 1). The transmission scattering parameter (S21) represents the relationship between the input power of the signal passing through the low-pass low-pass filter 1〇 and the output power of the signal, and the corresponding mathematical function is: S21 (dB) = l〇Lg (output power) /input power) . During the signal transmission of the low pass filter 10, part of the power of the signal is reflected back to the signal source. The power that is reflected back to the signal source is called the reflected power. The relationship between the input power of the signal through the low-pass filter 10 and the reflection power (dB) of the signal = l〇Lg 1003154897-0, the corresponding mathematical function is: S11 Form No. A0101 Page 6 of 14 1345374 _ * ' Corrected replacement page (reflected power / incident power) on May 4, 100. As can be seen from FIG. 3, the low pass filter 10 in the embodiment of the present invention has good filtering performance. From the curve IS21 | it can be observed that a steep "transition slope" is formed between the passband band and the attenuation band, and the insertion loss of the signal in the passband band is close to zero. At the same time, it can be observed from the curve 丨S11| that the absolute value of the signal reflection loss in the passband band is greater than 10, and outside the passband band, the absolute value of the signal reflection loss is less than 10. In the present embodiment, the low-pass filter 10 is connected to the first low-impedance transmission line 160 by the connection position of the input terminal 100 to the first low-impedance transmission line 160, and the output end 120 is connected to the second low-impedance transmission line 180. The two transmission zeros are generated at right angles of the triangle, so that the low-pass filter 10 has better suppression ability in the stop band and has good filtering performance. [0021] In the present embodiment, the oblique side coupling between the first low-impedance transmission line 160 and the second low-impedance transmission line 180 is utilized, thereby increasing the coupling of the first low-impedance transmission line 160 and the second low-impedance transmission line 180. The capacitance value, which not only increases the attenuation speed of the low pass filter 10, but also causes the transmission zero of the low pass filter 10 to be closer to the cutoff frequency. Moreover, it has a lower loss value in the passband band. [0022] In summary, the present invention complies with the requirements of the invention patent, and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims. BRIEF DESCRIPTION OF THE DRAWINGS [0023] FIG. 1 is a schematic structural view of a low pass filter according to an embodiment of the present invention. 097110172 Form No. A0101 Page 7 of 14 1003154897-0 1345374 May 2014 〇/日·桉正换页 [0024] FIG. 2 is an equivalent circuit diagram of the present invention. 3 is a test diagram of a low pass filter in an embodiment of the present invention. 4 is a schematic structural view of a conventional low-pass waver. [0027] FIG. 5 is a test diagram of a conventional low pass filter. [Main Component Symbol Description] [0028] Low Pass Filter 10 [0029] Circuit Board 20 [0030] Input End 100 [0031] Output End 120 [0032] South Impedance Transmission Line 140 [0033] First Connection End 142 [0034] Second connection end 144 [0035] first low impedance transmission line 160 [0037] third connection end 162 [0038] second low impedance transmission line 180 [0039] fourth connection end 182
097110172 表單編號Α0101 第8頁/共14頁 1003154897-0097110172 Form NumberΑ0101 Page 8 of 14 1003154897-0