Surface Acoustic Wave (SAW) Filters and Duplexers

Abstract

A surface acoustic wave (SAW) filter applicable to one embodiment of the present invention is a high-frequency filter including a universal terminal for inputting and outputting high-frequency signals, a transmitting terminal, and a receiving terminal, and includes: a first filter circuit, which uses a first frequency band as a passband and is connected to the universal terminal and the first terminal; a second filter circuit, which uses a second frequency band different from the first frequency band as a passband and is connected to the universal terminal and the second terminal; an antenna connected to the universal terminal; and at least one inductor connected in series between the universal terminal and the first filter circuit or the second filter circuit.

Description

Technical Field

[0001] The present invention relates to a surface acoustic wave (SAW) filter and a duplexer. Specifically, it relates to a surface acoustic wave (SAW) filter and a duplexer that can exhibit attenuation characteristics in a wider frequency range by separating an antenna board connected to a filter that allows different frequency bands to pass and additionally inserting an inductor into each antenna board. Background Art

[0002] Filters are an essential element in communication, signal generation, signal processing, and signal output, as a component for passing or removing frequencies in a specific frequency band. The most representative application field of the filters described above is the field of mobile communications, and surface acoustic wave (SAW) filters and duplexers are used as elements for passing or removing frequencies in a specific frequency band in mobile communication devices.

[0003] Existing surface acoustic wave (SAW) filters and duplexers are mainly used in the frequency band of 850MHz to 2.6GHz, so their attenuation performance is only an important requirement for a part of the frequency band. However, with the emergence of the global positioning system (GPS) frequency band, acoustic attenuation, various multi-frequency communication systems, and the commercialization of 5G systems using ultra-high frequency bands above 3.5GHz, attenuation characteristics are required in more diverse frequencies, high frequencies, and high frequency bands than before.

[0004] Furthermore, in order to be applicable to increasingly high-performance and ultra-miniaturized communication devices, surface acoustic wave (SAW) filters and duplexers also need to achieve high performance and ultra-miniaturization. As mentioned above, the miniaturization of surface acoustic wave (SAW) filters and duplexers is difficult to ensure sufficient attenuation characteristics due to the constraints of their design space and the increase of coupling.

[0005] In order to overcome the above-mentioned problems, a technology has been disclosed that forms a low-pass filter (LPF) type matching unit by adding inductors and capacitors to the outside of a surface acoustic wave (SAW) filter and a duplexer, or forms a defective microstrip structure (DMS) type surface acoustic wave (SAW) filter to ensure attenuation characteristics in the high frequency band.

[0006] However, the above-mentioned technology leads to a reduction in the external space available for matching the filter and other components, an increase in material costs, and a reduction in the degree of freedom in design.

[0007] Therefore, there is a need for a surface acoustic wave (SAW) filter and a duplexer having a novel structure that can maintain the existing miniaturization characteristics while ensuring the attenuation characteristics in the high frequency and ultra-high frequency regions.

[0008] Patent content

[0009] The object of the present invention is to provide a surface acoustic wave (SAW) filter and duplexer that can exhibit excellent attenuation characteristics over a wider high-frequency band by individually separating an antenna board connected to a filter that can pass different frequency bands and selectively inserting an inductor into the separated antenna board.

[0010] The technical problems of the present invention are not limited to the technical problems mentioned in the above content, and a person skilled in the art will be able to further clearly understand other technical problems not mentioned through the following description.

[0011] A surface acoustic wave (SAW) filter applicable to one embodiment of the present invention is a surface acoustic wave (SAW) filter including a universal terminal for inputting and outputting high-frequency signals, a transmitting terminal, and a receiving terminal, comprising: a first filter circuit, which uses a first frequency band as a passband and is connected to the universal terminal and the transmitting terminal; a second filter circuit, which uses a second frequency band different from the first frequency band as a passband and is connected to the universal terminal and the receiving terminal; an antenna connected to the universal terminal; and at least one inductor connected in series between the universal terminal and the first filter circuit or the second filter circuit.

[0012] In one embodiment, the inductor may include: a first inductor inserted into the first antenna board; and a second inductor inserted into the second antenna board.

[0013] In one embodiment, the antenna may include: a first antenna board branched from the common terminal and connected to the first filter circuit; and a second antenna board connected to the second filter circuit; wherein the first and second antenna boards may be arranged on the same plane.

[0014] In one embodiment, the attenuation region of the first filter circuit or the second filter circuit can be adjusted by the inductance value of the inductor.

[0015] In one embodiment, the present invention may further include: at least one shunt capacitor inserted between the first filter circuit or the second filter circuit and the inductor.

[0016] In one embodiment, the device may further include a bump for electrically connecting the inductor to the first antenna terminal or the second antenna terminal.

[0017] A duplexer applicable to another embodiment of the present invention is a duplexer including a universal terminal for inputting and outputting high-frequency signals, a transmitting terminal, and a receiving terminal, including: a transmitting filter connected to the universal terminal and the transmitting terminal; a receiving filter connected to the universal terminal and the receiving terminal; an antenna connected to the universal terminal; and at least one inductor connected in series between the universal terminal and the transmitting filter or the receiving filter.

[0018] In one embodiment, the antenna may include: a first antenna plate branched from the common terminal and connected to the transmitting filter; and a second antenna plate connected to the second receiving filter; wherein the first and second antenna plates may be arranged on the same plane.

[0019] In one embodiment, the inductor may include: a first inductor inserted into the first antenna board; and a second inductor inserted into the second antenna board.

[0020] In one embodiment, the attenuation region of the transmission filter or the reception filter can be adjusted by the inductance value of the inductor.

[0021] In one embodiment, the present invention may further include: at least one shunt capacitor inserted between the transmitting filter or the receiving filter and the inductor.

[0022] In one embodiment, the device may further include a bump for electrically connecting the inductor to the first antenna terminal or the second antenna terminal.

[0023] In one embodiment, the receiving filter may be formed of a ladder circuit including a surface acoustic wave (SAW) resonator.

[0024] In one embodiment, the receiving filter circuit may include: a surface acoustic wave (SAW) resonator connected in series to one side of the second antenna terminal; and a plurality of interdigital transducer (IDT) electrodes connected in series to the surface acoustic wave (SAW) resonator.

[0025] In the present invention, the attenuation characteristics in a wider frequency band can be improved by separating the electrically connected portions (antennas) of two filters that can pass different frequency bands.

[0026] Furthermore, by adjusting the inductance value of the inductor inserted into the high-frequency filter, the attenuation characteristics can be improved in a desired frequency band.

[0027] In addition, by separating the internal antenna of the high-frequency filter and inserting an inductor, its characteristics can be improved and an external matching space can be secured. The degree of freedom in designing a surface acoustic wave (SAW) filter and a duplexer can also be increased by simplifying its structure.

[0028] In addition, the manufacturing cost for improving the characteristics of a surface acoustic wave (SAW) filter and a duplexer can be saved by implementing an inductor using only a structure for electrically connecting different antenna terminals to a package. Moreover, it is possible to further contribute to the improvement of the characteristics by including an electrical structure for connecting the separated antennas as part of the inductor.

[0029] The effects of the present invention are not limited to the effects described above, and a person skilled in the art will be able to further clearly understand other effects not described through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of a surface acoustic wave (SAW) duplexer circuit applicable to the prior art.

[0031] Figure 2 This is a schematic diagram of a surface acoustic wave (SAW) filter and a duplexer circuit according to a first embodiment of the present invention.

[0032] Figure 3 This is a detailed diagram of a duplexer circuit according to the first embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram exemplarily illustrating a layer in which an antenna plate is arranged in a surface acoustic wave (SAW) filter according to the first embodiment of the present invention.

[0034] Figures 5 to 7 This is a graph for explaining the attenuation characteristics in the duplexer according to the first embodiment of the present invention.

[0035] Figure 8 This is a schematic diagram of a surface acoustic wave (SAW) filter and a duplexer circuit according to a second embodiment of the present invention.

[0036] Fig. 9 This is a detailed diagram of a duplexer circuit according to the second embodiment of the present invention.

[0037] Fig.10 This is a graph for explaining the attenuation characteristics in the duplexer according to the second embodiment of the present invention.

[0038] Fig.11 This is a graph for explaining the attenuation characteristics in the surface acoustic wave (SAW) filter according to the second embodiment of the present invention.

[0039] Fig.12 This is a schematic diagram of a surface acoustic wave (SAW) filter and a duplexer circuit according to a third embodiment of the present invention.

[0040] Fig.13 This is a detailed diagram of a duplexer circuit according to the third embodiment of the present invention.

[0041] Fig.14 This is a graph for explaining the attenuation characteristics in the duplexer according to the third embodiment of the present invention.

[0042] Figures 15 to 17 This is a graph for explaining the attenuation characteristics in the surface acoustic wave (SAW) filters according to the fourth to sixth embodiments of the present invention.

[0043]

Explanation of symbols

[0044] 1: Existing filters

[0045] 100: Surface Acoustic Wave (SAW) Filter

[0046] 110: Antenna

[0047] 200: Duplexer

[0048] 115, 215: Matching inductors

[0049] 120, 220: 1st filter circuit

[0050] 130, 230: Second filter circuit

[0051] 131, 231: Surface Acoustic Wave (SAW) Resonator

[0052] 141, 241: First inductor

[0053] 143, 243: Second inductor

[0054] CN: Universal terminal

[0055] N1: Sending terminal

[0056] N2: Receiving terminal DETAILED DESCRIPTION

[0057] Next, the preferred embodiments applicable to the present invention will be described in detail with reference to the accompanying drawings. The advantages and features of the present invention and methods of achieving the advantages and features will be further clarified by the subsequent embodiments described in detail with reference to the accompanying drawings. Throughout the specification, the same reference symbols represent the same constituent elements.

[0058] Unless otherwise defined, the meaning of all terms (including technical and scientific terms) used in this specification is the same as that commonly understood by personnel with general knowledge of the field to which the present invention belongs. In addition, unless otherwise clearly defined, the commonly used terms defined in the dictionary should not be exaggerated. The terms used in this specification are only used to illustrate the embodiments and are not intended to limit the present invention. In this specification, unless otherwise clearly mentioned, singular statements also include plural meanings.

[0059] The terms “comprises” and “comprising” used in this specification do not exclude the possibility that one or more other constituent elements, steps, actions or elements other than the mentioned constituent elements, steps, actions or elements exist or are added.

[0060] Figure 1 This is a schematic diagram of a conventional surface acoustic wave (SAW) duplexer circuit.

[0061] Existing surface acoustic wave (SAW) duplexers 1 are as follows Figure 1 As shown in (a), the attenuation characteristics in the high frequency band are improved by matching the transmission terminal (TX) with a low-frequency low-pass filter (LPF) represented by a dotted line. Figure 1 In the embodiments shown in (b) and (c), a part of the capacitors and inductors of the low-pass filter (LPF) are built into the surface acoustic wave (SAW) duplexer 1.

[0062] However, when the attenuation characteristics in the high frequency band are improved by matching the low pass filter (LPF) as described above, the degree of freedom in designing the surface acoustic wave (SAW) duplexer 1 decreases and the manufacturing cost increases.

[0063] Therefore, the present invention provides a structure capable of improving the attenuation characteristics in a high frequency band while maintaining the structure of an existing surface acoustic wave (SAW) filter or duplexer to the maximum extent.

[0064] Figure 2 FIG. 1 is a schematic diagram of a surface acoustic wave (SAW) filter 100 and a duplexer 200 circuit according to a first embodiment of the present invention. Figure 3 It is a detailed diagram of the circuit of the duplexer 200 according to the first embodiment of the present invention.

[0065] exist Figure 2 The surface acoustic wave (SAW) filter 100 shown in FIG. 1 (a) may include an antenna 110 , a first filter circuit 120 , a second filter circuit 130 , a first inductor 141 , and a second inductor 143 .

[0066] The antenna 110 is connected to the matching inductor 115 , and can include a first inductor 141 connected to the first filter circuit 120 via a common terminal CN, and a second inductor 143 connected to the second filter circuit 130 .

[0067] In addition, although Figure 2 Although not shown in the circuit diagram, the antenna 110 can include a first antenna plate branched from the common terminal CN and connected to the first filter circuit 120 and a second antenna plate connected to the second filter circuit 130, and the first and second antenna plates can be arranged on the same plane.

[0068] That is, the conventional method is to construct more than two filters on one chip and use one board to connect the antenna to the first filter circuit 120 and the second filter circuit 130 while connecting at least one terminal, but in an embodiment of the present invention, two antenna boards divided from the antenna 110 can be used to connect to the first filter circuit 120 and the second filter circuit 130 respectively.

[0069] Regarding this, Figure 4 This is a schematic diagram exemplarily illustrating a layer in which an antenna plate is arranged in a surface acoustic wave (SAW) filter 100 according to the first embodiment of the present invention. Figure 4 The illustrated surface acoustic wave (SAW) filter 100 is different from the conventional method of providing only one antenna plate, and is provided with separate antenna plates 110a and 110b for the first and second filter circuits 120 and 130 that can pass different frequency bands.

[0070] As described above, by using different antenna boards 110 a and 110 b to electrically separate the filters that were originally connected using one antenna 110 , it is possible to more easily present attenuation characteristics in a required frequency band.

[0071] At the same time, by inserting the first inductor 141 and the second inductor 143 into the antenna plates 110a and 110b, it is possible to present attenuation characteristics in a wider frequency band. In addition, it is possible to electrically connect the package including the surface acoustic wave (SAW) filter 100 by providing a bump (not shown) at the position where the first and second inductors 141 and 143 are inserted. When the bump is connected to the surface acoustic wave (SAW) filter 100, an electrical connection line (feed through) is generated, and the electrical connection line can be used as a part of the first or second inductor 141 and 143 or the electrical connection line as a whole can function as an inductor.

[0072] Re-read Figure 2The first filter circuit 120 can use the first frequency band as a passband and be connected in series between the first inductor 141 and the transmission terminal N1. In addition, the second filter circuit 130 can be at least one surface acoustic wave (SAW) resonator using the second frequency band as a passband, and can be connected to the second inductor 143 and the ground terminal. Among them, either the first frequency band or the second frequency band can be higher or lower.

[0073] The first and second inductors 141 and 143 are inserted into the separate antenna boards 110a and 110b, so that the surface acoustic wave (SAW) filter 100 exhibits attenuation characteristics in a specific frequency band. That is, the attenuation region of the first and second filter loops 120 and 130 connected to the antenna boards 110a and 110b can be adjusted by the inductance values ​​of the first and second inductors 141 and 143.

[0074] Furthermore, the inductance values ​​of the first and second inductors 141 and 143 connected to the antenna boards 110 a and 110 b can be up to 8 nH, and the inductance values ​​can be changed according to the size of the surface acoustic wave (SAW) filter 100 .

[0075] also, Figure 2 (b) is a schematic diagram illustrating the duplexer 200 in the first embodiment, which may include an antenna 210 , a transmission filter 220 , a reception filter 230 , a first inductor 241 , and a second inductor 243 .

[0076] The duplexer 200 is similar to the surface acoustic wave (SAW) filter 100 described above, and can also be electrically separated by connecting the transmitting filter 220 and the receiving filter 230 to different antenna boards respectively, and can also improve the attenuation characteristics in a specific frequency band by inserting the first and second inductors 241 and 243 into their respective antenna boards.

[0077] In the meantime, see Figure 3 The transmitting filter 220 of the duplexer 200 can be a ladder circuit including a plurality of series surface acoustic wave (SAW) resonators S2, S3, S4 and parallel surface acoustic wave (SAW) resonators P1, P2, P3, and the receiving filter 230 can be composed of a series surface acoustic wave (SAW) resonator S1 and a plurality of interdigital transducer (IDT) electrodes connected in series therewith.

[0078] Furthermore, by providing bumps (not shown) at positions where the first and second inductors 241 and 243 are inserted, the duplexer 200 can be electrically connected to an external device (not shown).

[0079] Figures 5 to 7This is a graph for explaining the attenuation characteristics of the duplexer 200 according to the first embodiment of the present invention.

[0080] See also Figure 5 In the duplexer 200, when the first inductor 241 and the second inductor 243 are respectively inserted into the antenna board connected to the transmission filter 220 and the antenna board connected to the reception filter 230, and each inductance value is 1 nH, the attenuation (dB) based on the frequency is as shown in the figure.

[0081] Among them, the graph represented by the black line is a graph related to the existing duplexer in which the antenna board is not separated and the inductor is not inserted, while the graph represented by the red line is a graph related to the duplexer 200 applicable to the present invention in which the antenna board is separated and the first and second inductors 241 and 243 with an inductance value of 1nH are inserted.

[0082] That is, by inserting an inductor into the antenna board separated as described above, it can be confirmed that a sharp skirt characteristic is exhibited and a notch is formed in the high frequency band of 3000 MHz, and it can be confirmed that an excellent attenuation characteristic is exhibited in a wider region above 3000 MHz.

[0083] Figure 6 The graph shows insertion loss (dB) based on frequency when a first inductor 241 having an inductance of 0.3 nH is inserted into an antenna board connected to the transmission filter 220 and a second inductor 243 having an inductance of 1.5 nH is inserted into an antenna board connected to the reception filter 230 .

[0084] Among them, the black graph is a graph related to the existing duplexer, and the red graph is a graph related to the duplexer 200 including the first and second inductors 241 and 243 having different inductance values. The antenna board connected to the transmission filter 220 and the first inductor 241 can be electrically connected to the package including the duplexer 200 by being equipped with bumps.

[0085] As described above, by inserting inductors with different inductance values ​​into the separated antenna boards, it is possible to ensure attenuation characteristics in the required range. That is, it can be confirmed that a sharp skirt characteristic can be exhibited starting from the high-frequency band of 2800MHz, and excellent attenuation characteristics can be exhibited in a wider range above 5000MHz.

[0086] In addition, in addition to inserting inductors having different inductance values ​​into the antenna board separated from the duplexer 200, a shunt capacitor C can be formed. In the case of forming the shunt capacitor, the insertion loss (dB) based on the frequency is as follows: Figure 7 shown.

[0087] See also Figure 7 When comparing the conventional duplexer (black) and the present invention (red), it can be confirmed that a notch is formed at a high frequency of 2400MHz and a sharp skirt characteristic is presented. In addition, a uniform attenuation characteristic is presented in a wide region above 5000MHz.

[0088] In addition, Figure 7 In the description, the case where the shunt capacitor C is formed in the antenna plate region separated from the duplexer 200 is described, but it can also be formed at any position in the duplexer 200 to which the present invention is applied and the package including the above duplexer.

[0089] In the above, the surface acoustic wave (SAW) filter 100 and the duplexer 200 according to the first embodiment of the present invention are described. In the present invention, by separating the antenna areas electrically connected in the process of integrating two filter circuits having different passbands into one chip and inserting inductors respectively, attenuation characteristics can be formed in a desired frequency band, and excellent attenuation characteristics can be ensured in a wider area.

[0090] Next, a case where only one inductor is inserted into an antenna board separated from the surface acoustic wave (SAW) filter 100 or the duplexer 200 and its characteristics will be described.

[0091] Figure 8 FIG. 1 is a schematic diagram of a surface acoustic wave (SAW) filter 100 and a duplexer 200 circuit according to a second embodiment of the present invention. Fig. 9 It is a detailed diagram of the circuit of the duplexer 200 according to the second embodiment of the present invention.

[0092] In the right Figure 8 as well as Fig. 9 In the description of the surface acoustic wave (SAW) filter 100 and the duplexer 200 applicable to the second embodiment shown in the figure, the detailed description related to the elements having the same configuration or shape as the first embodiment will be omitted. That is, since the other components except the inductor are the same as the first embodiment, the detailed description related to them will be omitted and only the inductor will be described.

[0093] See also Figure 8The surface acoustic wave (SAW) filter 100 shown in (a) may include an antenna 110, a first filter circuit 120, a second filter circuit 130, and a first inductor 141, while the duplexer 200 shown in (b) may include an antenna 210, a transmitting filter 220, a receiving filter 230, and a first inductor 241.

[0094] In the meantime, see Fig. 9 The transmitting filter 220 of the duplexer 200 can be a ladder circuit including a plurality of series surface acoustic wave (SAW) resonators S2, S3, S4 and parallel surface acoustic wave (SAW) resonators P1, P2, P3, and the receiving filter 230 can be composed of a series surface acoustic wave (SAW) resonator S1 and a plurality of interdigital transducer (IDT) electrodes connected in series therewith.

[0095] The first inductors 141 and 241 inserted into the surface acoustic wave (SAW) filter 100 and the duplexer 200 are connected to the antenna board connected to the first filter loop 120 and the transmission filter 220 among the two antenna boards branched from the common terminal CN, thereby ensuring the attenuation characteristics in a specific frequency band.

[0096] The inductance value of the first inductors 141 and 241 can be a maximum of 8 nH, and the inductance value can be changed according to the sizes of the surface acoustic wave (SAW) filter 100 and the duplexer 200 .

[0097] Regarding this, Fig.10 is a graph for explaining the attenuation characteristics of the duplexer 200 to which the second embodiment of the present invention is applied, and Fig.11 This is a graph for explaining the attenuation characteristics of the surface acoustic wave (SAW) filter 100 according to the second embodiment of the present invention.

[0098] See also Fig.10 , when the first inductor 241 is inserted into the antenna board connected to the transmission filter 220 in the duplexer 200 and the corresponding inductance value is 1nH, the attenuation (dB) based on the frequency is shown in the figure. Among them, the black graph is a graph related to the conventional duplexer, and the red graph is a graph related to the duplexer 200 applicable to the present invention including the first inductor 241 with an inductance value of 1nH.

[0099] As described above, it was confirmed that by inserting the first inductor 241 into the antenna board connected to the transmission filter 220 among the separated antenna boards, it was possible to exhibit excellent attenuation characteristics in the region of 4800 MHz or higher.

[0100] At the same time, the attenuation characteristics can be ensured in a required region by the inductance value, and a notch pole can be formed when a shunt capacitor is additionally formed.

[0101] In the meantime, see Fig.11 In the case where the first inductor 141 is inserted into the antenna board connected to the first filter loop 120 in the surface acoustic wave (SAW) filter 100 and the corresponding inductance value is 1nH, the attenuation (dB) based on the frequency is as follows. Among them, the black graph is a graph related to the conventional surface acoustic wave (SAW) filter, and the red graph is a graph related to the surface acoustic wave (SAW) filter 100 applicable to the present invention including the first inductor 141 with an inductance value of 1nH.

[0102] As described above, it was confirmed that by inserting the first inductor 141 into the antenna board connected to the first filter circuit 120 among the separated antenna boards, it was possible to exhibit excellent attenuation characteristics in the region of 3200 MHz or more.

[0103] Fig.12 FIG. 1 is a schematic diagram of a surface acoustic wave (SAW) filter 100 and a duplexer 200 circuit according to a third embodiment of the present invention. Fig.13 It is a detailed diagram of the circuit of the duplexer 200 according to the third embodiment of the present invention.

[0104] exist Fig.12 The surface acoustic wave (SAW) filter 100 shown in (a) of FIG. 1 may include an antenna 110, a first filter circuit 120, a second filter circuit 130, and a second inductor 143. Fig.12 The duplexer 200 shown in FIG. 2 (b) may include an antenna 210 , a transmission filter 220 , a reception filter 230 , and a second inductor 243 .

[0105] In addition, see Fig.13 The transmitting filter 220 of the duplexer 200 can be a ladder circuit including a plurality of series surface acoustic wave (SAW) resonators S2, S3, S4 and parallel surface acoustic wave (SAW) resonators P1, P2, P3, and the receiving filter 230 can be composed of a series surface acoustic wave (SAW) resonator S1 and a plurality of interdigital transducer (IDT) electrodes connected in series therewith.

[0106] The second inductors 143 and 243 inserted into the surface acoustic wave (SAW) filter 100 and the duplexer 200 are connected to the antenna board connected to the second filter loop 130 and the receiving filter 230 among the two antenna boards branched from the common terminal CN, thereby ensuring the attenuation characteristics in a specific frequency band.

[0107] The inductance value of the second inductors 143 and 243 can be a maximum of 8 nH, and the inductance value can be changed according to the sizes of the surface acoustic wave (SAW) filter 100 and the duplexer 200 .

[0108] Fig.14 This is a graph for explaining the attenuation characteristics of the duplexer 200 according to the third embodiment of the present invention.

[0109] See also Fig.14 , when the second inductor 243 is inserted into the antenna board connected to the receiving filter 220 in the duplexer 200 and the corresponding inductance value is 1nH, the attenuation (dB) based on the frequency is shown in the figure. Among them, the black graph is a graph related to the conventional duplexer, and the red graph is a graph related to the duplexer 200 applicable to the present invention including the first inductor 243 with an inductance value of 2nH.

[0110] As described above, it can be confirmed that by inserting the second inductor 243 into the separated antenna board connected to the receiving filter 230, a sharp skirt characteristic can be exhibited and a notch can be formed at a high frequency of 3200 MHz, and it can be confirmed that an excellent attenuation characteristic is exhibited in the region above 5000 MHz.

[0111] In the above content, the surface acoustic wave (SAW) filter 100 and the duplexer 200 applicable to the second and third embodiments of the present invention are described. In the present invention, the attenuation characteristics in the required frequency band can be ensured by selectively inserting inductors with different inductance values ​​into the separated antenna board. In addition, since it is not necessary to make a large deformation on the structure of the existing surface acoustic wave (SAW) filter and the duplexer 200, not only can the external matching space be ensured, but also because it is not necessary to consume additional material costs to improve the characteristics, its manufacturing cost can be saved.

[0112] In addition, in the surface acoustic wave (SAW) filter 100 using the first to third embodiments, the case where the first or second inductor 141, 143 is connected to the inside of the package including the surface acoustic wave (SAW) filter 100 is described, but the first or second inductor 141, 143 can also be provided outside the package.

[0113] Figures 15 to 17 This is a graph for explaining the attenuation characteristics of the surface acoustic wave (SAW) filter 100 according to the fourth to sixth embodiments of the present invention.

[0114] See also Fig.15In the surface acoustic wave (SAW) filter 100, when the first inductor 141 and the second inductor 143 are respectively inserted into the antenna board connected to the first filter circuit 120 and the antenna board connected to the second filter circuit 130, and each inductance value is 1 nH, the attenuation (dB) based on the frequency is shown in the figure.

[0115] Among them, the graph represented by the black line is a graph related to the existing filter in which the antenna board is not separated, the inductor is not inserted, and the resonator is not inserted, while the graph represented by the red line is a graph related to the surface acoustic wave (SAW) filter 100 applicable to the present invention, in which the antenna board is separated, the surface acoustic wave (SAW) resonator is inserted, and then the first and second inductors 141 and 143 with an inductance value of 1nH are inserted.

[0116] That is, by inserting an inductor into the antenna board separated as described above, it can be confirmed that a sharp skirt characteristic is exhibited and a notch is formed in the high frequency band of 2500 MHz, and it can be confirmed that an excellent attenuation characteristic is exhibited in a wider area above 2500 MHz.

[0117] See also Fig.16 , when the first inductor 141 with an inductance value of 1nH is inserted into the antenna board connected to the first filter loop 120 in the surface acoustic wave (SAW) filter 100, the attenuation (dB) based on the frequency is as follows. Among them, the graph represented by the black line is a graph related to the conventional filter without performing the separation of the antenna board, the insertion of the inductor, and the insertion of the resonator, and the graph represented by the red line is a graph related to the surface acoustic wave (SAW) filter 100 applicable to the present invention, in which the antenna board is separated and the surface acoustic wave (SAW) resonator is inserted, and then the first inductor 141 with an inductance value of 1nH is inserted.

[0118] That is, it was confirmed that by inserting the inductor into the separated antenna board as described above, it was possible to exhibit excellent attenuation characteristics in a wide range of 4000 MHz or more.

[0119] In addition, see Fig.17, when the first inductor 143 with an inductance value of 2nH is inserted into the antenna board connected to the second filter loop 130 in the surface acoustic wave (SAW) filter 100, the attenuation (dB) based on the frequency is as follows. Among them, the graph represented by the black line is a graph related to the conventional filter without performing the separation of the antenna board, the insertion of the inductor, and the insertion of the resonator, and the graph represented by the red line is a graph related to the surface acoustic wave (SAW) filter 100 applicable to the present invention, in which the antenna board is separated and the surface acoustic wave (SAW) resonator is inserted, and then the first inductor 143 with an inductance value of 2nH is inserted.

[0120] That is, by inserting an inductor into the antenna board separated as described above, it can be confirmed that a sharp skirt characteristic is exhibited and a notch is formed in the high frequency band of 2400 MHz, and it can be confirmed that an excellent attenuation characteristic is exhibited in a wider region above 5000 MHz.

[0121] In the above content, embodiments applicable to the present invention are described in conjunction with the accompanying drawings, but a person having general knowledge of the field to which the present invention belongs should be able to understand that the present invention can be implemented in other specific forms without changing its technical ideas or essential features. Therefore, the embodiments described in the above content are only exemplary and non-limiting in all aspects.

Claims

1. A surface acoustic wave (SAW) filter, characterized in that: A surface acoustic wave (SAW) filter including a common terminal, a transmission terminal, and a reception terminal for inputting and outputting a high-frequency signal includes: The first filter circuit has a first frequency band as a passband and is connected to the common terminal and the transmission terminal; A second filter circuit, having a second frequency band different from the first frequency band as a passband, and connected to the common terminal and the receiving terminal; an antenna connected to the universal terminal; and at least one inductor connected in series between the common terminal and the first filter circuit or the second filter circuit; The above antenna comprises: a first antenna plate branched from the common terminal and connected to the first filter circuit; and a second antenna plate connected to the second filter circuit; Wherein, the first and second antenna plates are arranged on the same plane; The above inductor comprises: A first inductor is inserted into the first antenna plate; and a second inductor is inserted into the second antenna plate.

2. The surface acoustic wave (SAW) filter according to claim 1, characterized in that: The attenuation region of the first filter circuit or the second filter circuit is adjusted by the inductance value of the inductor.

3. The surface acoustic wave (SAW) filter according to claim 1, characterized in that Also includes: At least one shunt capacitor is inserted between the first filter circuit or the second filter circuit and the inductor.

4. The surface acoustic wave (SAW) filter according to claim 1, characterized in that Also includes: The bump electrically connects the inductor and the first antenna terminal or the second antenna terminal.

5. A duplexer, characterized in that: In a duplexer including a universal terminal for inputting and outputting high frequency signals, a transmission terminal, and a reception terminal, the duplexer includes: A signal transmission filter connected to the above-mentioned universal terminal and the above-mentioned signal transmission terminal; A receiving filter connected to the universal terminal and the receiving terminal; an antenna connected to the universal terminal; and at least one inductor connected in series between the common terminal and the transmission filter or the reception filter; The above antenna comprises: a first antenna plate branched from the common terminal and connected to the transmission filter; and a second antenna plate connected to the reception filter; Wherein, the first and second antenna plates are arranged on the same plane; The above inductor comprises: A first inductor is inserted into the first antenna plate; and a second inductor is inserted into the second antenna plate.

6. The duplexer according to claim 5, characterized in that: The attenuation region of the transmission filter or the reception filter is adjusted by the inductance value of the inductor.

7. The duplexer according to claim 5, characterized in that: Also includes: At least one shunt capacitor is inserted between the transmission filter or the reception filter and the inductor.

8. The duplexer according to claim 6, characterized in that: Also includes: The bump electrically connects the inductor and the first antenna terminal or the second antenna terminal.

9. The duplexer according to claim 5, characterized in that: The above receiving filter, It is composed of a ladder circuit including a surface acoustic wave (SAW) resonator.

10. The duplexer according to claim 6, characterized in that: The above-mentioned receiving filter circuit comprises: A surface acoustic wave (SAW) resonator is connected in series to one side of the second antenna terminal; and a plurality of interdigital transducer (IDT) electrodes are connected in series to the surface acoustic wave (SAW) resonator.

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