200941937 九、發明說明： 【發明所屬之技術領域】 ' 本發明涉及一種濾波器，尤其涉及一種低通濾波器。 【先前技術】 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（passband)的插入損耗（inserti〇n i〇ss) ©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兪 好的表現。 " 清參照圖4，揭示了 徑得統的低通濾波窃。 該2通滤波器40包括輸入端4〇〇、輸出端42〇、高阻 =傳輸部440、矩形第一低阻抗傳輸部彻以及矩形200941937 IX. Description of the invention: [Technical field to which the invention pertains] The present invention relates to a filter, and more particularly to a low-pass filter. [Prior Art] 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 passband (insert) and the suppression of the stopband (rejecti〇n). The rejection of the filter in the stop band depends on its transmission zero point, and the more transmission zeros the filter has a good performance in suppressing the stop band. " Clearly refer to Figure 4, which reveals the low-pass filtering of the path. The 2-pass filter 40 includes an input terminal 4〇〇, an output terminal 42〇, a high resistance=transmission portion 440, a rectangular first low-impedance transmission portion, and a rectangle
且Γ專輸部480。輸入端400係用於饋入電磁 輸出#420係用於饋出電磁波訊號。高阻抗 傳440與輸入端彻和輸出端420電性連接。第 一:阻㈣輸部460與輸入端彻和高阻抗傳接^ 的端電性連接，第二低阻抗傳輪部48〇盥浐 :二和高阻抗傳輪部楊的另一端二接 置阻=輸部460和第二低阻抗傳輸部4 為8.69Π1ΙΛΛ35Γ。該低通逯波器4G的總長 咬务Μ為.53顏，面積為30.67mm2。 …圖5’揭示了該低通遽波器4〇之測試圖。 200941937 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，1 : 波效能不佳。 & 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 乃當今滤波器設計之一大挑戰。 【發明内容】 ❺ 有鑒於此，需提供一種具有良好濾波效能和較小面 積的低通濾波器。 種低通濾波器，包括輸入端、輸出端、高阻抗傳輸線 及一對低阻抗傳輸部。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輸入端和輸出端 電性連接。該等低阻抗傳輸部位於該高阻抗傳輸線的兩側， "亥等低阻抗傳輸部分別與輸入端、輸出端及高阻抗傳輸線電 φ性連接。 本發明實施方式所提供之低通濾波器，利用多個低阻抗 傳輪線排列於尚阻抗傳輪線的兩侧，增強了低阻抗傳輸線之 1的輕合，使付低通遽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】 如 請參閱圖1 ’所示為本發明實施方式之低通濾波 器10之結構示意圖。 在本實施方式中，低通遽波器1 〇印刷於電路板 200941937 20上。低通濾'波器10包括輸入端1〇〇、輸出端i2〇、 高阻抗傳輸線X40、一對低阻抗傳輸部16〇、第一 接線182、第二連接線184、第三連接線及 連接線188。 輸入端100係用 …"人机祝，W出端120 係用於饋出電磁波訊號。輸入端100與輸出端120 低通濾波器10之50歐姆匹配阻抗。 為 〇 ❹ 中，輸入端100與輸出端120位於同一 靶方式 山高阻抗傳輸線140電性連接於輸入端;〇〇°和輸出 端120之間並在輸入端1〇〇和輸出端12〇之間傳播 磁波訊號。高阻抗傳輸線14〇呈蜿蜒狀，其包括 連接端142、第二連接端144及_婉誕部μ。第— 連接端142與輸入端100、第一連接線182及第二 :線⑻電性連接。第二連接端144與輸出端咖、 第二連接線186及第四連接線188電性連接。 ⑷位於第-連接端142和第二連接端144之間並： 它們相連。即高阻抗傳輸線140從輸入端1〇〇向輸出、 端120婉挺延伸。 因高阻抗傳輸線ί40具有蜿蜒部146，從而減 了低通濾波器1 〇的面積。 在其它實施方式中，高阻抗傳輸線140的婉 146的彎折次數可以依實際需求改變。 該等低阻抗傳輸部160分別位於該高阻抗傳輪 線140的兩側。每個低阻抗傳輸部16〇呈矩形並包 第一低阻抗傳輸線162及第二低阻抗傳輸線164。第 9 200941937 :低阻抗傳輸線162和第二低阻抗傳輸線i64 隙m。第一低阻抗傳輸線i62和第二低阻抗 2線164的寬度不相等。第一低阻抗傳輸、線162包 =二連接端1620和第—麵合線1622，第二低阻抗 傳輸線164包括第四連接# 1640和第二耗合線 ❹And the special department 480. The input terminal 400 is used to feed the electromagnetic output #420 for feeding out electromagnetic wave signals. The high impedance transmission 440 is electrically connected to the input terminal and the output terminal 420. First, the resistance (four) transmission portion 460 is electrically connected to the input terminal and the high-impedance transmission terminal, and the second low-impedance transmission portion 48 is connected to the other end of the second and high-impedance transmission portion. The resistance=transmission unit 460 and the second low-impedance transmission unit 4 are 8.69Π1ΙΛΛ35Γ. The low-pass chopper 4G has a total length of .53 colors and an area of 30.67 mm 2 . ... Figure 5' reveals a test chart of the low pass chopper 4〇. 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 in the stop band, and 1: the wave performance is poor. At the same time, the area of the low-pass filter 40 is too large, which does not conform to the trend of wireless communication products toward light, thin, short, and small directions. 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 filter design. SUMMARY OF THE INVENTION In view of the above, it is desirable to provide a low pass filter with good filtering performance and a small area. A low pass filter includes an input end, an output end, a high impedance transmission line, and a pair of low impedance transmission sections. The input is used to feed electromagnetic signals. The output is used to feed out electromagnetic wave signals. The high impedance transmission lines are electrically connected to the input terminal and the output terminal, respectively. The low-impedance transmission portions are located on both sides of the high-impedance transmission line, and the low-impedance transmission portions such as "Hai" are electrically connected to the input terminal, the output terminal, and the high-impedance transmission line, respectively. The low-pass filter provided by the embodiment of the present invention uses a plurality of low-impedance transmission lines arranged on both sides of the impedance transmission line to enhance the lightness of the low-impedance transmission line, so that the low-pass chopper is Increase the transmission zero while bringing the transmission zero closer to the cutoff frequency. [Embodiment] FIG. 1 is a schematic structural view of a low-pass filter 10 according to an embodiment of the present invention. In the present embodiment, the low pass chopper 1 is printed on the circuit board 200941937 20. The low pass filter 10 includes an input terminal 1 , an output terminal i2 , a high impedance transmission line X40 , a pair of low impedance transmission portions 16 , a first connection 182 , a second connection line 184 , a third connection line , and a connection Line 188. The input terminal 100 is composed of ..." human machine, and the W terminal 120 is used for feeding electromagnetic wave signals. The input terminal 100 and the output terminal 120 have a 50 ohm matching impedance of the low pass filter 10. For example, the input end 100 and the output end 120 are located in the same target mode mountain high impedance transmission line 140 electrically connected to the input end; between the 〇〇° and the output end 120 and between the input end 1〇〇 and the output end 12〇 Spread magnetic wave signals. The high-impedance transmission line 14 is formed in a meander shape, and includes a connection end 142, a second connection end 144, and a 婉 部 portion μ. The first connection terminal 142 is electrically connected to the input terminal 100, the first connection line 182, and the second: line (8). The second connection end 144 is electrically connected to the output terminal, the second connection line 186 and the fourth connection line 188. (4) is located between the first connection end 142 and the second connection end 144 and: they are connected. That is, the high-impedance transmission line 140 extends from the input terminal 1 to the output terminal 120. Since the high-impedance transmission line ί40 has the crotch portion 146, the area of the low-pass filter 1 减 is reduced. In other embodiments, the number of bends of the crucible 146 of the high impedance transmission line 140 can be varied as needed. The low impedance transmission portions 160 are respectively located on both sides of the high impedance transmission line 140. Each of the low-impedance transmission portions 16 is rectangular and includes a first low-impedance transmission line 162 and a second low-impedance transmission line 164. 9th 200941937: low impedance transmission line 162 and second low impedance transmission line i64 slot m. The widths of the first low impedance transmission line i62 and the second low impedance 2 line 164 are not equal. The first low impedance transmission, line 162 package = two connection ends 1620 and first face line 1622, and the second low impedance transmission line 164 includes a fourth connection # 1640 and a second consumption line ❹
1642。第一稱合線1622和第二輛合線1642相對設 计。第一低阻抗傳輸線162的第三連接端162〇透過 第一連接線182或第二連接線184與輸入端1〇〇和高 阻抗傳輸線14G的第-連接端142電性連接，第二低 阻抗傳輸線164的第四連接端164〇透過第三連接線 186或第四連接線188與輸出端12〇和高阻抗傳輸線 140的第二連接端144電性連接。 在本實施方式中，間隙17〇呈v型。換而言之， 第一麵合線1622和第二耦合線1642分別呈v型。 在其它實施方式中’該間隙170可以呈C型、S 型L型、W型等。相應地，第一耦合線1622和第 二耦合線1642可以分別為c型、s型、L型、w型 等。即第一耦合線1622和第二耦合線1642分別呈彎 折型，從而增加了第一低阻抗傳輸線丄62和第二低阻 抗傳輸線164之間耦合所形成的電容值。 請參照圖2 ’所示為本發明低通濾波器的等 效電路圖。圖2之電感LI、L2、L3及L4係分別由 本發明低通濾波器10之第一連接線182、第二連接 線184、第三連接線186和第四連接線188所等效形 成，電感L5係由尚阻抗傳輸線14〇所等效形成，電 200941937 容Cl和C2係分別由該等第一低阻抗傳輪線i62與 .電路板20之接地金屬面所等效形成，電容C3和& ’係分別由該等第二低阻抗傳輸線164與電路板2〇之 接地金屬面所等效形成，電容C5和C6係分別由該 等第一低阻抗傳輸線162與該等第二低阻抗 ^ 182耦合形成。 hi 在本實施方式中，低通濾波器1〇的總長為 5.82mm，總寬為3.68mm ’面積為2142mm2，與傳統 ❹的低通濾波器40相比，低通濾波器1〇的面積^ ” 30%。 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10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^ (s-parameter:S21)的幅度以及反射之散射參數 (S-parameter:S11)的幅度。透射之散射參數（S21)表示 〇通過低通低通滤波器10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）。在低通滤波器 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率之 間的關係，其相應的數學函數為：S11 (dB) =10Lg (反射功率/入射功率）。 由圖3可知，本發明實施方式中之低通濾波器 11 200941937 10具有良好之濾波效能。從曲線|S21|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〇。同時從曲線1642. The first splicing line 1622 and the second merging line 1642 are oppositely designed. The third connection end 162 of the first low-impedance transmission line 162 is electrically connected to the input end 1〇〇 and the first connection end 142 of the high-impedance transmission line 14G through the first connection line 182 or the second connection line 184, and the second low impedance The fourth connection end 164 of the transmission line 164 is electrically connected to the output end 12A and the second connection end 144 of the high-impedance transmission line 140 through the third connection line 186 or the fourth connection line 188. In the present embodiment, the gap 17 is v-shaped. In other words, the first cross line 1622 and the second coupling line 1642 are respectively v-shaped. In other embodiments, the gap 170 may be C-shaped, S-shaped L-shaped, W-shaped, or the like. Accordingly, the first coupling line 1622 and the second coupling line 1642 may be c-type, s-type, L-type, w-type, etc., respectively. That is, the first coupling line 1622 and the second coupling line 1642 are respectively bent, thereby increasing the capacitance value formed by the coupling between the first low-impedance transmission line 62 and the second low-impedance transmission line 164. Referring to Figure 2', there is shown an equivalent circuit diagram of the low pass filter of the present invention. The inductors LI, L2, L3, and L4 of FIG. 2 are respectively formed by the first connection line 182, the second connection line 184, the third connection line 186, and the fourth connection line 188 of the low-pass filter 10 of the present invention, and the inductance is The L5 is formed by the equivalent impedance transmission line 14〇, and the electrical 200941937 capacitors C1 and C2 are respectively formed by the first low-impedance transmission line i62 and the grounded metal surface of the circuit board 20, and the capacitors C3 and & The 'lower impedance transmission line 164 is formed equivalently to the grounded metal surface of the circuit board 2, respectively, and the capacitors C5 and C6 are respectively connected by the first low impedance transmission line 162 and the second low impedance ^ 182 is formed by coupling. In the present embodiment, the total length of the low-pass filter 1 为 is 5.82 mm, and the total width is 3.68 mm 'the area is 2142 mm 2 . Compared with the conventional low-pass filter 40 , the area of the low-pass filter 1 ^ ^ 30%. Please refer to Fig. 3' for the test diagram of the low-pass filter 10 in the embodiment of the present invention obtained by electromagnetic simulation. The horizontal axis of the figure shows the frequency of the signal passing through the low-pass filter 10 (unit·· GHz ), the vertical axis represents the amplitude (unit: dB), and the quadrant region includes the amplitude of the transmitted scattering parameter (s-parameter: S21) and the amplitude of the scattering parameter of the reflection (S-parameter: S11). S21) represents the relationship between the input power of the signal passing through the low-pass low-pass filter 10 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 reflected back to the signal source is called the reflected power. The input power of the signal passing through the low-pass filter 10 and the reflection of the signal The relationship between power and its corresponding mathematics The number is: S11 (dB) = 10 Lg (reflected power / incident power). As can be seen from Fig. 3, the low pass filter 11 200941937 10 in the embodiment of the present invention has good filtering performance. It can be observed from the curve |S21| 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 〇. Simultaneous curve
Is 111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1 〇。 在本實施方式中，低通濾波器1〇藉由第一低阻 抗傳輸線162和第二低阻抗傳輸線164呈不對稱設計 產生兩個傳輸零點，這不僅使低通濾波器於 處之截止頻寬超過10GHz’而且提高了低通濟波写 止帶的抑制能力’提高了低通濾波器1〇的遽波 在本實施方式中’利用第一 馇-把„丨 ' 吵丨Λ仍丨寸铷蜾160和 第二低阻抗傳輸線162之間的f折輕合線1622、1642 f = ’從而增加了第一低阻抗傳輸、線160和第二低阻 ”輸線咖之間輕合所形成的電容值，上： 二的傳輸零點更為靠近截止頻率。而且，在】= •k内，具有較低之損耗值。 ， 菱依法提出專利 施例，舉凡熟悉 之等效修飾或變 二紅上所述，本發明符合發明專利要件， 申清准，以上所述者僅為本發明之較佳實 本案技藝之人士’在爰依本案發明精神所作 化’皆應包含於以下之申請專利範圍内。 【圖式簡單說明】 12 200941937 圖1為本發明實施方式中低通濾波器之結構示意圖。 圖2為本發明低通濾波器的等效電路圖。 圖3為本發明實施方式中低通濾波器之測試圖。 圖4為習知低通濾波器之結構示意圖。 圖5為習知低通濾波器之測試圖。 【主要元件符號說明】 低通濾波器 10 20 100 120 140 142 144 146 160 162 1620 164 1640 1622 1642 182 184 電路板 ®輸入端 輸出端 尚阻抗傳輸線 第一連接端 第二連接端 婉挺部 低阻抗傳輸部 0 第一低阻抗傳輸線 第三連接端 第二低阻抗傳輸線 第四連接端 第一耦合線 第二耦合線 第一連接線 第二連接線 第三連接線 186 13 188 200941937 第四連接線Is 111 can observe that the absolute value of signal reflection loss in the passband band is greater than 10, and outside the passband band, the absolute value of signal reflection loss is less than 1 〇. In the present embodiment, the low pass filter 1 is asymmetrically designed to generate two transmission zeros by the first low impedance transmission line 162 and the second low impedance transmission line 164, which not only causes the low pass filter to have a cutoff bandwidth. More than 10 GHz' and improved the suppression ability of the low-pass wave write-stop band 'Improve the chopping of the low-pass filter 1 在 In the present embodiment, 'Using the first 馇-把 丨 丨Λ 丨Λ 丨Λ 丨Λ 丨Λ 铷The f-folded light-bonding line 1622, 1642 f = ' between the 蜾160 and the second low-impedance transmission line 162 increases the light-weight connection between the first low-impedance transmission, the line 160 and the second low-resistance line Capacitance value, upper: The transmission zero of the second is closer to the cutoff frequency. Moreover, within ??? = • k, there is a lower loss value. The patent is filed according to law, and the invention is in accordance with the equivalent of the invention, and the invention is in accordance with the requirements of the invention patent, and the above is only the person skilled in the art of the present invention. In the spirit of the invention, it should be included in the scope of the following patent application. BRIEF DESCRIPTION OF THE DRAWINGS 12 200941937 FIG. 1 is a schematic structural view of a low pass filter according to an embodiment of the present invention. 2 is an equivalent circuit diagram of a low pass filter 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 filter. Figure 5 is a test diagram of a conventional low pass filter. [Main component symbol description] Low-pass filter 10 20 100 120 140 142 144 146 160 162 1620 164 1640 1622 1642 182 184 Circuit board ® input terminal output impedance transmission line first connection terminal second connection terminal taper low impedance Transmission part 0 first low-impedance transmission line third connection end second low-impedance transmission line fourth connection end first coupling line second coupling line first connection line second connection line third connection line 186 13 188 200941937 fourth connection line
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