Front end module

Abstract

The invention discloses a front-end module. The front-end module comprises a first elastic wave device connected with an antenna terminal and used for passing through a first frequency band; a second elastic wave device connected to the antenna terminal and configured to pass through a second frequency band; a third elastic wave device connected to the antenna terminal and configured to pass through a third frequency band; a capacitive element connected to the antenna terminal; a first switch for switching on / off states of the antenna terminal and the first elastic wave device; a second switch for switching on / off states of the antenna terminal and the second elastic wave device; a third switch for switching on / off states of the antenna terminal and the third elastic wave device; and a fourth switch for switching the closed / open state of the antenna terminal and the capacitive element. The frequencies of the second and third frequency bands are higher than the first frequency band, and the resonant frequency of the capacitive element is higher than the first frequency band and lower than the frequencies of the second and third frequency bands.

Description

Technical Field

[0001] The present disclosure relates to a high-frequency front-end module for transmitting and receiving communication signals in multiple communication bands. Background Art

[0002] Mobile communication terminals represented by smartphones provide various telecommunication functions such as telephone, video, data, messaging, and broadcasting. In order to implement these telecommunication functions, a high-frequency front-end module capable of utilizing multiple different frequency bands corresponding to different frequency ranges must be used.

[0003] As a high-frequency front-end module capable of utilizing multiple communication bands, an electronic system circuit employing carrier aggregation is known (for example, see Patent Document 1).

[0004] In Figure 2 C of Patent Document 1, an electronic system including an antenna, a frequency divider, and two power amplifiers (a first power amplifier and a second power amplifier) is described.

[0005] In the above electronic system, the frequency divider is connected to the antenna. Further, in this electronic system, each of the two power amplifiers is connected to the frequency divider through a transceiver switch and a filter.

[0006] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2017-17691 Summary of the Invention

[0007] A front-end module supporting carrier aggregation generally includes three or more band-pass filters, but the design of the equivalent capacitance of each band-pass filter is difficult. The purpose of the present disclosure is to construct a front-end module supporting carrier aggregation with a simpler structure and easier design of the equivalent capacitance of the band-pass filter.

[0008] To achieve the above object, the present disclosure provides a front-end module, characterized by including an antenna terminal, a first surface acoustic wave device, a second surface acoustic wave device, a third surface acoustic wave device, a capacitive element, a first switch, a second switch, a third switch, and a fourth switch; The first surface acoustic wave device is connected to the antenna terminal and is configured to pass through a first frequency band; The second surface acoustic wave device is connected to the antenna terminal and is configured to pass through a second frequency band; The third surface acoustic wave device is connected to the antenna terminal and is configured to pass through a third frequency band; The capacitive element is connected to the antenna terminal; The first switch is configured to perform a closing / opening switching between the antenna terminal and the first surface acoustic wave device; The second switch is configured to perform a closing / opening switching between the antenna terminal and the second surface acoustic wave device; The third switch is used to perform a closing / opening switching between the antenna terminal and the third elastic wave device; The fourth switch is used to perform a closing / opening switching between the antenna terminal and the capacitive element; Wherein, the second frequency band and the third frequency band are frequency bands with higher frequencies than the first frequency band; the capacitive element is a capacitive component or a resonator; when the capacitive element is the resonator, the resonance frequency of the resonator is a frequency higher than the first frequency band and lower than the second frequency band and the third frequency band.

[0009] In some embodiments, at least one of the first switch to the third switch is in a closed state, and the second frequency band and the third frequency band are at least partially overlapping frequency bands or adjacent frequency bands to each other, and the second switch and the third switch will not be closed simultaneously.

[0010] In some embodiments, when the first switch is in a closed state, and the second switch and the third switch are in open states, the fourth switch is in a closed state.

[0011] In some embodiments, the resonator is divided in parallel into a first divided resonator and a second divided resonator, and the resonance frequencies of the first divided resonator and the second divided resonator are different frequencies.

[0012] In some embodiments, the resonator is a SAW resonator, and at least one of the second elastic wave device and the third elastic wave device is an elastic wave device of a SAW filter including a piezoelectric substrate, and the resonator is formed on the piezoelectric substrate.

[0013] In some embodiments, it further includes a fourth elastic wave device and a fifth switch; the fourth elastic wave device is connected to the antenna terminal and is used to pass through a fourth frequency band; the fifth switch is used to perform a closing / opening switching between the antenna terminal and the fourth elastic wave device; the fourth frequency band is a frequency band lower than the second frequency band, and when the first switch or the fifth switch is closed, and the second switch and the third switch are open, the fourth switch is closed.

[0014] In some embodiments, when only the fifth switch is closed, the fourth switch is closed.

[0015] In some embodiments, when the third switch and the fifth switch are closed, the fourth switch is open.

[0016] In some of these embodiments, a first coil element is further included; the first coil element is connected between the first switch and the first elastic wave device and grounded.

[0017] In some of these embodiments, a second coil element and a third coil element are further included; the second coil element is connected in series between the second switch and the second elastic wave device; the third coil element is connected in series between the third switch and the third elastic wave device.

[0018] In some of these embodiments, a fourth coil element is further included; the fourth coil element is connected between the fifth switch and the fourth elastic wave device and grounded.

[0019] In some of these embodiments, the equivalent input capacitance of the first elastic wave device is less than the equivalent input capacitance of the capacitive element at frequencies outside the second frequency band and at frequencies outside the third frequency band.

[0020] In some of these embodiments, the equivalent input capacitance of the second elastic wave device is equal to the equivalent input capacitance of the third elastic wave device at the center frequency of the first frequency band.

[0021] In some of these embodiments, the equivalent input capacitance of the first elastic wave device is less than the equivalent input capacitance of the second elastic wave device and the equivalent input capacitance of the third elastic wave device at frequencies outside the first frequency band.

[0022] In some of these embodiments, the equivalent input capacitance of the second elastic wave device is equal to the equivalent input capacitance of the third elastic wave device at the center frequency of the first frequency band and is also equal at the center frequency of the fourth frequency band.

[0023] In some of these embodiments, the first elastic wave device includes a first filter and a second filter. The first filter passes through a first frequency band in the first frequency band; the second filter passes through a second frequency band in the first frequency band that is higher in frequency than the first frequency band, and the equivalent input capacitance of the first filter is less than the equivalent input capacitance of the second filter at the average of the center frequencies of the second frequency band and the third frequency band, i.e., the average center frequency.

[0024] In some of these embodiments, the fourth elastic wave device includes a third filter and a fourth filter. The third filter passes through band three in the fourth frequency band; the fourth filter passes through band four in the fourth frequency band that is higher in frequency than band three, and the equivalent input capacitance of the third filter is less than that of the fourth filter at the average center frequency, which is the average of the center frequency of the second frequency band and the center frequency of the third frequency band.

[0025] According to the present disclosure, a front-end module supporting carrier aggregation with a simpler structure and easier to design the equivalent capacitance of a band-pass filter can be constructed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the front-end module 1 in Embodiment 1; Figure 2 is a characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the fourth switch SW4 are closed; Figure 3 is a characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the second switch SW2 are closed; Figure 4 is a characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the third switch SW3 are closed; Figure 5 is a characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the fourth switch SW4 are closed (the second one); Figure 6 is a characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the second switch SW2 are closed (the second one); Figure 7 is a characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the third switch SW3 are closed (the second one); Figure 8 is a diagram showing a surface acoustic wave resonator for a surface acoustic wave filter as an example of a band-pass filter; Figure 9 is a diagram showing a piezoelectric thin film resonator for an elastic wave filter as an example of a band-pass filter; Figure 10 is a schematic diagram of the front-end module 1 in Embodiment 2; Figure 11 is a schematic diagram of the resonator R of the front-end module 1 in Embodiment 3; Figure 12 is a characteristic diagram of the front-end module 1 in Embodiment 3 when the first switch SW1 and the fourth switch SW4 are closed; Figure 13 It is a schematic diagram of the front-end module 4 in Embodiment 4; Figure 14 It is a schematic diagram of the front-end module 5 in Embodiment 5; Figure 15 It is a schematic diagram of the front-end module 6 in Embodiment 6; Figure 16 It is a schematic diagram of the front-end module 7 in Embodiment 7.

[0027]

Symbol Explanation

[0028] The embodiments will be described below with reference to the accompanying drawings. In each figure, the same or corresponding parts are marked with the same symbols. The repeated description of the corresponding parts is appropriately simplified or omitted.

[0029] Unless otherwise defined, the technical terms or scientific terms involved in this disclosure shall have the general meaning understood by those with ordinary skills in the technical field to which this disclosure belongs. In this disclosure, words such as "a", "an", "one kind", "the", "these" and the like do not indicate a limitation in quantity, and they can be singular or plural. The terms "including", "comprising", "having" and any variants thereof involved in this disclosure are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent in these processes, methods, products or devices. The terms "connected", "coupled" and the like involved in this disclosure are not limited to physical or mechanical connections, but may include electrical connections, whether directly or indirectly connected. The term "plurality" involved in this disclosure means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" may mean: A exists alone, A and B exist simultaneously, and B exists alone. Usually, the character " / " indicates that the objects associated before and after are in an "or" relationship. The terms "first", "second", "third" and the like involved in this disclosure are only used to distinguish similar objects and do not represent a specific sorting of the objects.

[0030] The following will be combined with Figures 1 to 16A detailed description of typical embodiments of the present invention will be given.

[0031] Embodiment 1 Figure 1 is a schematic diagram of the front-end module 1 in Embodiment 1. As Figure 1 shown, the front-end module 1 includes an antenna terminal ANT, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a first surface acoustic wave device BPF1, a second surface acoustic wave device BPF2, a third surface acoustic wave device BPF3, and a resonator R as a capacitive element. It should be noted that in other embodiments, the capacitive element may also be a capacitor element.

[0032] Each of the switches SW1 to SW4 is used to switch between the antenna terminal ANT and each of the surface acoustic wave devices BPF1 to BPF3 and the resonator R.

[0033] The surface acoustic wave devices BPF1 to BPF3 form a band-pass filter, for example, to allow only the electrical signals in the required frequency band of the applied electrical signal to pass through.

[0034] The first surface acoustic wave device BPF1 includes a first filter F1 and a second filter F2. The first filter F1 is a band-pass filter, for example, which is a receiving band of frequency band 1, with a center frequency of 2140 MHz, allowing a frequency band of 2110 MHz to 2170 MHz to pass through.

[0035] The second filter F2 is a band-pass filter, for example, which is a receiving band of frequency band 3, with a center frequency of 1842.5 MHz, allowing a frequency band of 1805 MHz to 1880 MHz to pass through.

[0036] The second surface acoustic wave device BPF2 is a band-pass filter, for example, which is a receiving band of frequency band 7, with a center frequency of 2655 MHz, allowing a frequency band of 2620 MHz to 2690 MHz to pass through.

[0037] The third surface acoustic wave device BPF3 is a band-pass filter, for example, which is a receiving band of frequency band 41, with a center frequency of 2593 MHz, allowing a frequency band of 2496 MHz to 2690 MHz to pass through.

[0038] The passband portions of the second surface acoustic wave device BPF2 and the third surface acoustic wave device BPF3 overlap. Therefore, the second surface acoustic wave device BPF2 and the third surface acoustic wave device BPF3 are not used simultaneously. That is, the second switch SW2 and the third switch SW3 are not closed simultaneously.

[0039] This is because if elastic wave devices with partially overlapping frequency bands are closed simultaneously, significant impedance mismatches will occur. In addition, even if the frequency bands do not partially overlap, if the passband frequencies of the elastic wave devices are close to each other to the extent that impedance matching is difficult to achieve, these elastic wave devices will not be used simultaneously.

[0040] For example, for elastic wave devices with passband frequencies that differ by only about 25 MHz, it can be considered that they are close to each other to the extent that impedance matching is difficult to achieve.

[0041] The equivalent input capacitance of the first elastic wave device BPF1 of the front-end module 1 in Embodiment 1, that is, the equivalent capacitance EC (Equivalent Capacitance) at a specific frequency, is configured to be less than the equivalent input capacitance (equivalent capacitance EC at a specific frequency) of the resonator R at frequencies outside the passband of the second elastic wave device BPF2 and outside the passband of the third elastic wave device BPF3.

[0042] The resonance frequency of the resonator R is set to 2470 MHz, for example. The resonance frequency of the resonator R is higher than the frequencies of Band 1 and Band 3, and lower than the frequencies of Band 7 and Band 41. For example, the resonance frequency of the resonator R is set to 2470 MHz.

[0043] Figure 2 is the characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the fourth switch SW4 are closed. As Figure 2 shown, when the first switch SW1 and the fourth switch SW4 are closed, a good impedance matching state can be obtained on the antenna side, good passband characteristics can be achieved, and good attenuation characteristics can be obtained at the resonance frequency of the resonator R.

[0044] In addition, the equivalent capacitance EC of the first elastic wave device BPF1 is configured to be less than the equivalent input capacitances (equivalent capacitance EC at a specific frequency) of the second elastic wave device BPF2 and the third elastic wave device BPF3 at frequencies outside its passband.

[0045] Through the above configuration, a good impedance matching state can be obtained on the antenna side regardless of which switch SW1 to 4 is in the closed state.

[0046] The equivalent capacitance EC here refers to the equivalent input capacitance at a specific frequency. Representing the imaginary part (i.e., reactance) of the input impedance of the filter as X and the frequency as f, it can be calculated by the following formula 1. The specific frequency referred to here is the frequency outside the passband of the filter.

[0047] EC = 1 / (2*π*f*X) Formula 1 In addition, the equivalent input capacitances of the second elastic wave device BPF2 and the third elastic wave device BPF3 are configured to be equivalent at the center frequency of the first elastic wave device BPF1. The equivalent input capacitance referred to here is the equivalent input capacitance at a specific frequency calculated by the above formula 1.

[0048] Table 1:

[0049] Table 1 shows the usage of each elastic wave device BPF1 - 3 and the closed / open states of each switch SW1 - 4. When the first switch SW1 and the second switch SW2 are both closed, only the second switch SW2 is closed, or only the third switch SW3 is closed, the fourth switch SW4 is in the open state.

[0050] In addition, when only the first switch SW1 is closed, the fourth switch SW4 is also in the closed state. At the same time, at least one of the switches SW1 - 3 is in the closed state. Also, the second switch SW2 and the third switch SW3 are not closed simultaneously.

[0051] In the front - end module supporting carrier aggregation, under any connection mode of the elastic wave device, the equivalent input capacitance is the same in the ideal state, so the impedance remains consistent in any connection state. For example, when Band 3 (B3) is used simultaneously with Band 7 (B7) or Band 41 (B41), since the influence of the equivalent input capacitance of Band 7 or Band 41 has been considered in Band 3, there is no need to connect the resonator R.

[0052] If the equivalent input capacitances of Band 7 and Band 41 are equal at the center frequency of Band 3, the configuration of Band 3 considering the equivalent input capacitance will be optimized. For example, in the case of Band 7 and Band 41, Band 3 is optimized when the equivalent input capacitance is 1.4 pF.

[0053] Since the pass - band parts of Band 7 and Band 41 overlap, they are not used simultaneously. Therefore, when Band 7 or Band 41 is used alone, Band 3 can be made in the off state for separate optimization.

[0054] When Band 1 (B1) or Band 3 is used alone, by connecting the resonator R to replace the equivalent input capacitance of Band 7 or Band 41, the influence of the equivalent input capacitance is considered. As Figure 2 shown, the performance can be exerted without changing the configuration characteristics of the optimized Band 1 or Band 3.

[0055] Figure 3 is the characteristic diagram of the front - end module 1 in Embodiment 1 when the first switch SW1 and the second switch SW2 are closed. As Figure 3As shown, when the first switch SW1 and the second switch SW2 are closed, a good impedance matching state can be obtained on the antenna side, achieving good frequency response characteristics.

[0056] Figure 4 is the characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the third switch SW3 are closed. As Figure 4 shown, when the first switch SW1 and the third switch SW3 are closed, a good impedance matching state can be obtained on the antenna side, achieving good frequency response characteristics.

[0057] Figures 5 to 7 shows the characteristics of the front-end module 1, where the characteristics of the first surface acoustic wave device BPF1 include: as the frequency band 34 receiving band of the first filter F1, which is a band-pass filter with a center frequency of 2117.5 MHz and allowing a frequency band of 2110 MHz to 2125 MHz to pass through; and as the frequency band 39 receiving band of the second filter F2, which is a band-pass filter with a center frequency of 1900 MHz and allowing a frequency band of 1880 MHz to 1920 MHz to pass through.

[0058] Figure 5 is the second characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the fourth switch SW4 are closed.

[0059] As Figure 5 shown, even when other frequency bands are used for the first surface acoustic wave device BPF1, when the first switch SW1 and the fourth switch SW4 are closed, a good impedance matching state can still be obtained on the antenna side, achieving good frequency response characteristics, and good attenuation characteristics can be obtained at the resonance frequency of the resonator R.

[0060] Figure 6 is the second characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the second switch SW2 are closed. In Figure 6 it, the frequency band 34 is used for the first filter F1, and the frequency band 39 is used for the second filter F2. As Figure 6 shown, even when other frequency bands are used for the first surface acoustic wave device BPF1, when the first switch SW1 and the second switch SW2 are closed, a good impedance matching state can still be obtained on the antenna side, achieving good frequency response characteristics.

[0061] Figure 7 is the second characteristic diagram of the front-end module 1 in Embodiment 1 when the first switch SW1 and the third switch SW3 are closed. In Figure 7 it, the frequency band 34 is used for the first filter F1, and the frequency band 39 is used for the second filter F2. As Figure 7As shown, even when another frequency band is adopted for the first elastic wave device BPF1, when the first switch SW1 and the third switch SW3 are closed, a good impedance matching state can still be obtained on the antenna side, achieving good passband characteristics.

[0062] Figure 8 An example of a band-pass filter, a surface acoustic wave resonator for a surface acoustic wave filter, is shown. The surface acoustic wave resonator includes an interdigital transducer (IDT) 51 and a reflector 52 formed on a piezoelectric substrate 50. The IDT 51 has a pair of comb-shaped electrodes 51a arranged opposite to each other.

[0063] For example, the comb-shaped electrode 51a includes a plurality of electrode fingers 51b and a bus bar 51c connecting the plurality of electrode fingers 51b. The reflector 52 is provided on both sides of the IDT 51, sandwiching the IDT 51. The IDT 51 is used to excite surface acoustic waves. For example, the piezoelectric substrate 50 is a lithium tantalate substrate or a lithium niobate substrate. The IDT 51 and the reflector 52 are formed of, for example, an aluminum film or a copper film.

[0064] For example, the piezoelectric substrate 50 can be bonded to a support substrate such as a sapphire substrate, an alumina substrate, a spinel substrate, or a silicon substrate. In addition, a protective film or a temperature compensation film covering the IDT 50 and the reflector 52 can also be provided.

[0065] When any one of the elastic wave devices BPF1 to 3 is an elastic wave device using a surface acoustic wave filter, the resonator R can be formed as a SAW resonator on the device chip of the elastic wave device using the surface acoustic wave filter.

[0066] In addition, when there are a plurality of elastic wave devices using surface acoustic wave filters, it is preferable to form the resonator R on the device chip of the elastic wave device whose frequency is closest to the resonance frequency of the resonator R. This is because the device chip has optimized the cutting angle and thickness of the piezoelectric substrate, the thickness of the IDT electrode, etc. according to the frequency band. For example, the resonator R can be formed as a SAW resonator on the device chip provided with the surface acoustic wave filter having the highest frequency.

[0067] Figure 9is an example of a band-pass filter, showing a schematic diagram of a piezoelectric thin-film resonator for an elastic-wave filter. The piezoelectric thin-film resonator includes a piezoelectric film 57 provided on a substrate 55. A lower electrode 56 and an upper electrode 58 are sandwiched on both sides of the piezoelectric film 57. A gap 59 is formed between the lower electrode 56 and the substrate 55. The lower electrode 56 and the upper electrode 58 excite elastic waves in the piezoelectric film 57 in a thickness longitudinal vibration mode. The lower electrode 56 and the upper electrode 58 are made of a metal film such as a ruthenium film, for example. The piezoelectric film 57 is an aluminum nitride film, for example. The substrate 55 can be a silicon substrate, a sapphire substrate, an alumina substrate, a spinel substrate, or a glass substrate, for example. Another example, the elastic-wave resonator can adopt a structure different from that of Figure 8 and Figure 9 shown in the structure.

[0068] The front-end module 1 of the above-described Embodiment 1 has a simpler structure, can construct a front-end module supporting carrier aggregation, and is easy to design the equivalent capacitance of the band-pass filter.

[0069] Embodiment 2 Figure 10 is a schematic diagram of the front-end module 2 in Embodiment 2. As Figure 10 shown, the front-end module 2 includes an antenna terminal ANT, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a first elastic-wave device BPF1, a second elastic-wave device BPF2, a third elastic-wave device BPF3, a first coil element L1, a second coil element L2, a third coil element L3, and a resonator R as a capacitive element.

[0070] The first coil element L1 is connected between the first switch SW1 and the first elastic-wave device BPF1 and grounded. The second coil element L2 is connected in series between the second switch and the second elastic-wave device BPF2. The third coil element L3 is connected in series between the third switch and the third elastic-wave device BPF3. Other structures are the same as those of the front-end module 1 in Embodiment 1. As described in Embodiment 1, the first elastic-wave device BPF1 is an elastic-wave device including a band-pass filter having a lower frequency than the second elastic-wave device BPF2 and the third elastic-wave device BPF3.

[0071] Since the first elastic-wave device BPF1 is a low-frequency filter in the front-end module 2, its capacitance component is relatively large, so it is necessary to reduce the capacitance value of the first elastic-wave device BPF1. By connecting the coil element in parallel, all or part of the capacitance component of the first elastic-wave device BPF1 can be canceled. For example, the first coil element L1 can be set to 5 nH.

[0072] Since the second elastic wave device BPF2 and the third elastic wave device BPF3 are high-frequency filters, their capacitive components are relatively small. Therefore, it is desirable to increase the capacitive components of the second elastic wave device BPF2 and the third elastic wave device BPF3. By connecting the coil elements in series, the capacitive components of the second elastic wave device BPF2 and the third elastic wave device BPF3 can be made to appear larger, so that the equivalent input capacitance can be adjusted more easily. For example, the second coil element L2 and the third coil element L3 can be set to 3 nH.

[0073] The equivalent input capacitances of the second elastic wave device BPF2 and the third elastic wave device BPF3 are configured to be equivalent at the center frequency of the first elastic wave device BPF1 in combination with the inductance values of the second coil element L2 and the third coil element L3.

[0074] In the case of the front-end module 2 of the above-described second embodiment, only by adding inductive elements for adjustment, a simple structure is maintained, thus constituting a front-end module that facilitates the design of a band-pass filter and supports carrier aggregation.

[0075] Embodiment 3 Figure 11 is a schematic diagram of the resonator R of the front-end module 3 in Embodiment 3. As Figure 11 shown, the resonator R can be divided in parallel into a first resonator R1 and a second resonator R2. Figure 11 The resonator R shown can also adopt a structure sandwiched between a pair of reflectors. In addition, the resonance frequencies of the first resonator R1 and the second resonator R2 can be set to different frequencies. For example, the resonance frequency difference between the first resonator R1 and the second resonator R2 can be set in the range of 25 MHz to 50 MHz to ensure sufficient attenuation characteristics and achieve wide-band attenuation.

[0076] Figure 12 is a characteristic diagram of the front-end module 1 in Embodiment 3 when the first switch SW1 and the fourth switch SW4 are closed.

[0077] As Figure 12 shown, when the first switch SW1 and the fourth switch SW4 are closed, a good impedance matching state can be obtained on the antenna side, good passband characteristics can be achieved, and good attenuation characteristics with a wider frequency band can be obtained through the resonance frequency of the first resonator R1 and the resonance frequency of the second resonator R2 different from the resonance frequency of the first resonator R1.

[0078] The front-end module 3 of the above-described Embodiment 3 can obtain good attenuation characteristics with a wider frequency band while maintaining a simple structure, thus constituting a front-end module that facilitates the design of a band-pass filter and supports carrier aggregation.

[0079] Embodiment 4 Figure 13 It is a schematic diagram of the front-end module 4 in Embodiment 4. As Figure 13 shown, in addition to including the structures of the front-end module 1 in Embodiment 1 and the front-end module 2 in Embodiment 2, the front-end module 4 further includes a fourth elastic wave device BPF4, a fifth switch SW5, and a fourth coil element L4.

[0080] As Figure 13 shown, the fifth switch SW5 is used to switch the closed / open state between the antenna terminal ANT and the fourth elastic wave device BPF4. The fourth coil element L4 is connected between the fifth switch SW5 and the fourth elastic wave device BPF4.

[0081] As Figure 13 shown, the first elastic wave device BPF1 includes a first filter F1 and a second filter F2. In addition, the fourth elastic wave device BPF4 includes a third filter F3 and a fourth filter F4.

[0082] The first filter F1 is, for example, a band-pass filter, which is a receiving band for frequency band 3, with a center frequency of 1842.5 MHz, allowing a frequency band of 1805 MHz to 1880 MHz to pass through.

[0083] The second filter F2 is, for example, a band-pass filter, which is a receiving band for frequency band 1, with a center frequency of 2140 MHz, allowing a frequency band of 2110 MHz to 2170 MHz to pass through.

[0084] Here, as described above, the second elastic wave device BPF2 is, for example, a receiving band for frequency band 7, with a center frequency of 2655 MHz. The third elastic wave device BPF3 is, for example, a receiving band for frequency band 41, with a center frequency of 2593 MHz. The average value of these center frequencies is 2624 MHz.

[0085] The first filter F1 and the first coil element L1 are designed to have an equivalent input capacitance that satisfies the following conditions at the average center frequency of 2624 MHz, and this equivalent input capacitance is calculated by the aforementioned formula 1. The second filter F2 and the first coil element L1 are similarly designed to have an equivalent input capacitance that satisfies the following conditions at the average center frequency of 2624 MHz.

[0086] Since the frequency of the first filter F1 is lower than that of the second filter F2, at the average center frequency of 2624 MHz, its equivalent input capacitance is smaller.

[0087] The third filter F3 is, for example, a band-pass filter, which is a receiving band for frequency band 39, with a center frequency of 1900 MHz, allowing a frequency band of 1880 MHz to 1920 MHz to pass through.

[0088] The fourth filter F4 is, for example, a band-pass filter, which is the reception band of frequency band 34, with a center frequency of 2117.5 MHz, allowing a frequency band of 2110 MHz to 2125 MHz to pass through.

[0089] Here, the center frequencies of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz) are 1872 MHz.

[0090] The center frequencies of the second filter F2 (2110 MHz to 2170 MHz) and the fourth filter F4 (2110 MHz to 2125 MHz) are 2129 MHz.

[0091] The third filter F3 and the fourth coil element L4 are designed to have an equivalent input capacitance that satisfies the following conditions at an average center frequency of 2624 MHz, and this equivalent input capacitance is calculated by the aforementioned formula 1.

[0092] The fourth filter F4 and the fourth coil element L4 are also designed to have an equivalent input capacitance that satisfies the following conditions at an average center frequency of 2624 MHz. Since the frequency of the third filter F3 is lower than that of the fourth filter F4, its equivalent input capacitance is smaller at an average center frequency of 2624 MHz.

[0093] The equivalent input capacitance of the second surface acoustic wave device BPF2 is greater than the equivalent input capacitances of the filters F1 to F4 at an average center frequency of 2624 MHz at the center frequency of 1872 MHz of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz).

[0094] In addition, the equivalent input capacitance of the third surface acoustic wave device BPF3 is greater than the equivalent input capacitances of the filters F1 to F4 at an average center frequency of 2624 MHz at the center frequency of 1872 MHz of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz).

[0095] Furthermore, at the center frequency of 1872 MHz of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz), the absolute value of the impedance of the sum of the equivalent input capacitances of the second filter F2 or the fourth filter F4 and the second surface acoustic wave device BPF2 is preferably equal to the absolute value of the impedance of the first coil element L1 at 1872 MHz.

[0096] In addition, at the center frequency of 2129 MHz of the second filter F2 (2110 MHz to 2170 MHz) and the fourth filter F4 (2110 MHz to 2125 MHz), the absolute value of the impedance of the sum of the equivalent input capacitance of the first filter F1 or the third filter F3 and the equivalent input capacitance of the second surface acoustic wave device BPF2 is preferably equal to the absolute value of the impedance of the first coil element L1 at 2129 MHz.

[0097] In addition, at the average center frequency of 2624 MHz, the absolute value of the impedance of the sum of the equivalent input capacitance of the first filter F1 or the third filter F3 and the equivalent input capacitance of the second filter F2 or the fourth filter F4 is preferably equal to the absolute value of the impedance of the first coil element L1 at 2624 MHz.

[0098] The fourth surface acoustic wave device BPF4 has a passband with a lower frequency than the passband of the second surface acoustic wave device BPF2, and thus its capacitive component is relatively large. Therefore, it is desirable to reduce the capacitive component of the fourth surface acoustic wave device BPF4. By connecting the coil element in parallel, all or part of the capacitive component of the fourth surface acoustic wave device BPF4 can be canceled. Thus, regardless of which of the switches SW1 to 5 is closed, a good impedance matching state can be obtained on the antenna side through the fourth coil element L4 connected between the fifth switch SW5 and the fourth surface acoustic wave device BPF4 and grounded.

[0099] Table 2:

[0100] Table 2 shows the usage of each surface acoustic wave device BPF1 to BPF4 and the closed / open states of each switch SW1 to SW5. When the second switch SW2 and the fifth switch SW5 are closed, or when the third switch SW3 and the fifth switch SW5 are closed, the fourth switch SW4 is in the open state.

[0101] In addition, when only the fifth switch SW5 is closed, the fourth switch SW4 is also in the closed state. At the same time, at least one of the switches SW1 to SW3 and SW5 is in the closed state. In addition, the second switch SW2 and the third switch SW3 are not closed at the same time; the first switch SW1 and the fifth switch SW5 are not closed at the same time.

[0102] For example, when Band 39 (B39) is used simultaneously with Band 7 (B7) or Band 41 (B41), since Band 39 already takes into account the influence of the equivalent input capacitance of Band 7 or Band 41, there is no need to connect the resonator R.

[0103] For example, if the equivalent input capacitances of band 7 and band 41 are equivalent at the center frequency of band 39, the configuration of band 39 considering the equivalent input capacitance will be optimized. For example, in the case of band 7 and band 41, band 39 is optimized when the equivalent input capacitance is 1.4 pF.

[0104] For example, since the passbands of band 7 and band 41 partially overlap and thus they will not be used simultaneously, when band 7 or band 41 is used alone, it can be optimized separately according to the fact that band 39 is in the off state.

[0105] For example, when band 39 is used alone, by connecting the resonator R to replace the equivalent input capacitance of band 7 or band 41, thus considering the influence of the equivalent input capacitance, the configured characteristics of the optimized band 39 can be kept unchanged and its performance can be exerted.

[0106] In the front-end module 4 of Embodiment 4, for example, it is not envisaged that band 3 and band 39 will be used simultaneously because their passband frequencies are close to each other to the extent that impedance matching is difficult to achieve.

[0107] The front-end module 4 of the above Embodiment 4 can constitute a front-end module supporting carrier aggregation with a simpler structure even in a configuration including six bands, making the equivalent capacitance design of the band-pass filter more convenient.

[0108] Embodiment 5 Figure 14 is a schematic diagram of the front-end module 5 in Embodiment 5. As Figure 14 shown, the front-end module 5 includes an antenna terminal ANT, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a first surface acoustic wave device BPF1, a second surface acoustic wave device BPF2, a third surface acoustic wave device BPF3, a first coil element L1, a second coil element L2, a third coil element L3, and a capacitive element C as a capacitive component.

[0109] Each of the switches SW1 to SW4 is used for switching between the antenna terminal ANT and each of the surface acoustic wave devices BPF1 to BPF3 and the capacitive element C. The first coil element L1 is connected between the first switch SW1 and the first surface acoustic wave device BPF1 and grounded. The second coil element L2 is connected in series between the second switch SW2 and the second surface acoustic wave device BPF2. The third coil element L3 is connected in series between the third switch SW3 and the third surface acoustic wave device BPF3.

[0110] Each of the elastic wave devices BPF1 to BPF3 is, for example, a band-pass filter that allows only the electrical signals in the required frequency band of the applied electrical signals to pass through. The first elastic wave device BPF1 is, for example, for the receiving frequency band of frequency band 3, with a center frequency of 1842.5 MHz, and is a band-pass filter that allows the frequency band of 1805 MHz to 1990 MHz to pass through.

[0111] The second elastic wave device BPF2 is, for example, for the receiving frequency band of frequency band 7, with a center frequency of 2655 MHz, and is a band-pass filter that allows the frequency band of 2620 MHz to 2690 MHz to pass through. The third elastic wave device BPF3 is, for example, for the receiving frequency band of frequency band 41, with a center frequency of 2593 MHz, and is a band-pass filter that allows the frequency band of 2496 MHz to 2690 MHz to pass through.

[0112] A part of the passbands of the second elastic wave device BPF2 and the third elastic wave device BPF3 overlaps. Therefore, the second elastic wave device BPF2 and the third elastic wave device BPF3 are not used simultaneously. That is, the second switch SW2 and the third switch SW3 are not closed simultaneously.

[0113] This is because if elastic wave devices with partially overlapping frequencies are closed simultaneously, it will significantly cause impedance mismatch. In addition, even if the frequencies do not partially overlap, it is difficult to achieve impedance matching between elastic wave devices with passband frequencies close to each other, so they are not used simultaneously.

[0114] For example, elastic wave devices with passband frequencies differing by only about 25 MHz can be considered to have frequencies close enough to each other that it is difficult to achieve impedance matching.

[0115] Since the first elastic wave device BPF1 is a low-frequency filter in the front-end module 1, its capacitance is relatively large. Therefore, it is necessary to reduce the capacitance value of the first elastic wave device BPF1. By connecting a coil element in parallel, all or part of the capacitance of the first elastic wave device BPF1 can be cancelled out. For example, the first coil element L1 can be set to 5 nH.

[0116] Since the second elastic wave device BPF2 and the third elastic wave device BPF3 are high-frequency filters, their capacitances are relatively small. Therefore, it is necessary to make the capacitances of the second elastic wave device BPF2 and the third elastic wave device BPF3 appear larger. By connecting a coil element in series, the capacitances of the second elastic wave device BPF2 and the third elastic wave device BPF3 can be made to appear larger. This can more easily adjust the equivalent input capacitance. For example, the second coil element L2 and the third coil element L3 can be set to 3 nH.

[0117] The equivalent input capacitance of the first elastic wave device BPF1 of the front-end module 5 in Embodiment 5, that is, the equivalent capacitance EC at a specific frequency, is designed to be smaller than the equivalent input capacitance (equivalent capacitance EC at a specific frequency) of the capacitive element C at frequencies outside the passband of the second elastic wave device BPF2 and outside the passband of the third elastic wave device BPF3.

[0118] Therefore, regardless of which one of the switches SW1 to 4 is in the closed state, a good impedance matching state can be obtained at the antenna terminal through the first coil element L1 connected to and grounded by the first elastic wave device BPF1.

[0119] In addition, the equivalent capacitance EC of the first elastic wave device BPF1 at frequencies outside its passband is designed to be smaller than the equivalent input capacitances (equivalent capacitances EC at a specific frequency) of the second elastic wave device BPF2 and the third elastic wave device BPF3.

[0120] Therefore, regardless of which one of the switches SW1 to 4 is in the closed state, a good impedance matching state can be obtained at the antenna terminal through the first coil element L1 connected to and grounded by the first elastic wave device BPF1.

[0121] The equivalent capacitance EC mentioned here refers to the equivalent input capacitance at a specific frequency. Let the imaginary part of the filter input impedance be reactance X and the frequency be f, then it can be calculated by Formula 1 in Embodiment 1 above. The specific frequency referred to here is the frequency outside the passband of the filter.

[0122] In addition, the equivalent input capacitances of the second elastic wave device BPF2 and the third elastic wave device BPF3 are adjusted to be equivalent at the center frequency of the first elastic wave device BPF1 in combination with the coil amounts of the second coil element L2 and the third coil element L3. The equivalent input capacitance here refers to the equivalent input capacitance calculated by the above Formula 1 at a specific frequency.

[0123] Table 3

[0124] Table 3 lists the usage conditions of the elastic wave devices BPF1 to 3 and the switch states of the switches SW1 to 4. When the first switch SW1 and the second switch SW2 are closed, when only the second switch SW2 is closed, or when only the third switch SW3 is closed, the fourth switch SW4 is in the open state.

[0125] In addition, when only the first switch SW1 is closed, the fourth switch SW4 is also closed. In addition, at least one of the switches SW1 to 3 is always in the closed state. And the second switch SW2 and the third switch SW3 are not closed simultaneously.

[0126] In any connection mode of the elastic wave device, the equivalent input capacitance of the front-end module supporting carrier aggregation should be the same, and the impedance should be consistent regardless of the connection situation. For example, when Band 3 (B3) is used simultaneously with Band 7 (B7) or Band 41 (B41), since the design of Band 3 has considered the equivalent input capacitance of Band 7 or Band 41, there is no need to connect the capacitive element C.

[0127] When the equivalent input capacitances of Band 7 and Band 41 are equal at the center frequency of Band 3, the configuration of Band 3 considering the equivalent input capacitance will be optimized. For example, in the case of Band 7 and Band 41, when the equivalent input capacitance is 1.4 pF, the configuration of Band 3 will be optimized.

[0128] Since the passbands of Band 7 and Band 41 partially overlap, they will not be used simultaneously. Therefore, when Band 7 or Band 41 is used alone, it only needs to be optimized separately according to the disconnected state of Band 3.

[0129] When Band 3 is used alone, the capacitive element C is connected to replace the equivalent input capacitance of Band 7 or Band 41, so as to consider the equivalent input capacitance and ensure that the characteristics of the optimized configuration of Band 3 remain unchanged while playing its role.

[0130] The front-end module 5 in the above Embodiment 5 has a simpler structure, can construct a front-end module supporting carrier aggregation, and is easy to design the equivalent capacitance of the band-pass filter.

[0131] Embodiment 6 Figure 15 is a schematic diagram of the front-end module 6 in Embodiment 6. As Figure 15 shown, on the basis of the structure of the front-end module 5 in Embodiment 5, the front-end module 6 adds a fourth elastic wave device BPF4, a fifth switch SW5, and a fourth coil element L4.

[0132] The fifth switch SW5 is used to switch between closing and disconnecting between the antenna terminal ANT and the fourth elastic wave device BPF4. The fourth coil element L4 is connected between the fifth switch SW5 and the fourth elastic wave device BPF4 and grounded.

[0133] The fourth elastic wave device BPF4 is, for example, for the receiving band of Band 39, whose center frequency is 1900 MHz, and is a band-pass filter allowing the passage of the frequency band from 1880 MHz to 1920 MHz. In other words, the passband frequency of the fourth elastic wave device BPF4 is lower than the passband frequency of the second elastic wave device BPF2. For example, the fourth coil element L4 can be set to 4.8 nH.

[0134] Since the passband of the fourth elastic wave device BPF4 is lower than that of the second elastic wave device BPF2, its capacitance is relatively large. Therefore, it is necessary to reduce the capacitance of the fourth elastic wave device BPF4. By connecting coil elements in parallel, all or part of the capacitance of the fourth elastic wave device BPF4 can be canceled out. In this way, no matter which one of the switches SW1-5 is in the closed state, a good impedance matching state can be obtained at the antenna terminal through the fourth coil element L4 connected between the fifth switch SW5 and the fourth elastic wave device BPF4 and grounded.

[0135] Table 4

[0136] Table 4 shows the usage of each elastic wave device BPF1-4 and the switch states of each switch SW1-5. When the second switch SW2 and the fifth switch SW5 are closed, or when the third switch SW3 and the fifth switch SW5 are closed, the fourth switch SW4 is in the open state.

[0137] In addition, when only the fifth switch SW5 is closed, the fourth switch SW4 is in the closed state. In addition, at least one of the switches SW1-3 and SW5 is in the closed state. Moreover, the second switch SW2 and the third switch SW3 are not closed at the same time. In addition, the first switch SW1 and the fifth switch SW5 are not closed at the same time.

[0138] For example, when Band 39 (B39) is used simultaneously with Band 7 (B7) or Band 41 (B41), since the design of Band 39 has taken into account the equivalent input capacitance of Band 7 or Band 41, there is no need to connect the capacitive element C.

[0139] When the equivalent input capacitances of Band 7 and Band 41 are equal at the center frequency of Band 39, the configuration of Band 39 considering the equivalent input capacitance will be optimized. For example, in the case of Band 7 and Band 41, when the equivalent input capacitance is 1.4 pF, the configuration of Band 39 is optimized.

[0140] Since the passbands of Band 7 and Band 41 partially overlap and they are not used simultaneously, when Band 7 or Band 41 is used alone, it is only necessary to optimize them separately according to the state of Band 39 being disconnected.

[0141] When Band 39 is used alone, the capacitive element C is connected to replace the equivalent input capacitance of Band 7 or Band 41, so as to consider the equivalent input capacitance, ensure that the characteristics of the optimized Band 39 remain unchanged, and give play to its performance.

[0142] Note that in the front-end module 2 of Embodiment 2, the simultaneous use of frequency band 3 and frequency band 39 is not considered. This is because the passband frequencies of these two frequency bands are close to each other, making it difficult to achieve impedance matching.

[0143] In another usage example, the first surface acoustic wave device BPF1 can be, for example, a receive frequency band for frequency band 1, with a center frequency of 2140 MHz, serving as a band-pass filter that allows the 2110 MHz to 2170 MHz frequency band to pass through.

[0144] The fourth surface acoustic wave device BPF4 can be, for example, a receive frequency band for frequency band 34, with a center frequency of 2117.5 MHz, serving as a band-pass filter that allows the 2110 MHz to 2125 MHz frequency band to pass through.

[0145] The front-end module 6 of the above-described Embodiment 6 has a simpler structure, can construct a front-end module supporting carrier aggregation, and is easy to design the equivalent capacitance of the band-pass filter.

[0146] Embodiment 7 Figure 16 is a schematic diagram of the front-end module 7 in Embodiment 7. As Figure 16 shown, based on the structure of the front-end module 6 in Embodiment 6, the front-end module 7 adds a first surface acoustic wave device BPF1, which includes a first filter F1 and a second filter F2. In addition, the fourth surface acoustic wave device BPF4 includes a third filter F3 and a fourth filter F4.

[0147] The first filter F1 is, for example, a receive frequency band for frequency band 3, with a center frequency of 1842.5 MHz, serving as a band-pass filter that allows the 1805 MHz to 1880 MHz frequency band to pass through.

[0148] The second filter F2 is, for example, a receive frequency band for frequency band 1, with a center frequency of 2140 MHz, serving as a band-pass filter that allows the 2110 MHz to 2170 MHz frequency band to pass through.

[0149] As described above, the second surface acoustic wave device BPF2 is, for example, a receive frequency band for frequency band 7, with a center frequency of 2655 MHz. The third surface acoustic wave device BPF3 is, for example, a receive frequency band for frequency band 41, with a center frequency of 2593 MHz. The average value of the two center frequencies is 2624 MHz.

[0150] The first filter F1 and the first coil element L1 are designed to have an equivalent input capacitance that satisfies the calculation of the above formula 1 at an average center frequency of 2624 MHz and meet the following conditions. Similarly, the second filter F2 and the first coil element L1 are designed to have an equivalent input capacitance that satisfies the calculation of the above formula 1 at an average center frequency of 2624 MHz and meet the following conditions.

[0151] Since the frequency of the first filter F1 is lower than that of the second filter F2, the equivalent input capacitance of the first filter F1 is smaller at an average center frequency of 2624 MHz.

[0152] The third filter F3 is, for example, for the receiving band of frequency band 39, with a center frequency of 1900 MHz, and is a band-pass filter that allows the 1880 MHz to 1920 MHz band to pass through.

[0153] The fourth filter F4 is, for example, for the receiving band of frequency band 34, with a center frequency of 2117.5 MHz, and is a band-pass filter that allows the 2110 MHz to 2125 MHz band to pass through.

[0154] The center frequencies of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz) are 1872 MHz.

[0155] The center frequencies of the second filter F2 (2110 MHz to 2170 MHz) and the fourth filter F4 (2110 MHz to 2125 MHz) are 2129 MHz.

[0156] The third filter F3 and the fourth coil element L4 are designed to have an equivalent input capacitance that satisfies the calculation of the above formula 1 at an average center frequency of 2624 MHz and meet the following conditions.

[0157] The fourth filter F4 and the fourth coil element L4 are also designed to have an equivalent input capacitance that satisfies the calculation of the above formula 1 at an average center frequency of 2624 MHz and meet the following conditions. Since the frequency of the third filter F3 is lower than that of the fourth filter F4, the equivalent input capacitance of the third filter F3 is smaller at an average center frequency of 2624 MHz.

[0158] The equivalent input capacitance of the second surface acoustic wave device BPF2 is greater at the center frequency of 1872 MHz of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz) than the equivalent input capacitances of the respective filters F1 to F4 at an average center frequency of 2624 MHz.

[0159] The equivalent input capacitance of the third elastic wave device BPF3 is greater at the center frequency of 1872 MHz of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz) than the equivalent input capacitance of each of the filters F1 to F4 at the average center frequency of 2624 MHz.

[0160] At the center frequency of 1872 MHz of the first filter F1 (1805 MHz to 1880 MHz) and the third filter F3 (1880 MHz to 1920 MHz), the absolute value of the impedance of the sum of the equivalent input capacitance of the second filter F2 or the fourth filter F4 and the equivalent input capacitance of the second elastic wave device BPF2 is preferably equal to the absolute value of the impedance of the first coil element L1 at 1872 MHz.

[0161] At the center frequency of 2129 MHz of the second filter F2 (2110 MHz to 2170 MHz) and the fourth filter F4 (2110 MHz to 2125 MHz), the absolute value of the impedance of the sum of the equivalent input capacitance of the first filter F1 or the third filter F3 and the equivalent input capacitance of the second elastic wave device BPF2 is preferably equal to the absolute value of the impedance of the first coil element L1 at 2129 MHz.

[0162] At the average center frequency of 2624 MHz, the absolute value of the impedance of the sum of the equivalent input capacitance of the first filter F1 or the third filter F3 and the equivalent input capacitance of the second filter F2 or the fourth filter F4 is preferably equal to the absolute value of the impedance of the first coil element L1 at 2624 MHz.

[0163] The front-end module 7 of the above-described embodiment 7 has a simpler structure even in a configuration including 6 frequency bands, can construct a front-end module supporting carrier aggregation, and is easy to design the equivalent capacitance of the band-pass filter.

[0164] Although several aspects of at least one embodiment have been described, it should be understood that various modifications, corrections, and improvements are readily conceivable to those skilled in the art. These modifications, corrections, and improvements are intended to be part of the present disclosure and within the scope of the present disclosure.

[0165] It should be understood that the embodiments of the methods and apparatuses described herein are not limited to the structural and arrangement details of the components described in the above description or shown in the drawings. The methods and apparatuses can be implemented in other embodiments and can be implemented or executed in various ways.

[0166] The specific embodiments are for illustrative purposes only and are not intended to be limiting. In addition, for example, the number of components installed in the module is not limited to the number shown in the drawings.

[0167] The expressions and terms used in this disclosure are for explanatory purposes and should not be construed as limiting. The use of "including", "comprising", "having", "containing" and their variants herein is intended to cover the items listed hereinafter, their equivalents as well as additional items.

[0168] The reference to "or" should be construed such that any term described using "or" may refer to one term, multiple terms or all terms in that description.

[0169] The references to front and back, left and right, top and bottom, vertical and horizontal, inside and outside, etc. are for convenience of description. These references do not limit the components of this disclosure to any particular orientation or spatial arrangement. Therefore, the above descriptions and illustrations are merely examples.

Claims

1. A front-end module, characterized in that: The device comprises an antenna terminal, a first elastic wave device, a second elastic wave device, a third elastic wave device, a capacitive element, a first switch, a second switch, a third switch and a fourth switch; The first elastic wave device is connected to the antenna terminal and is used to pass a first frequency band; The second elastic wave device is connected to the antenna terminal and is used to pass a second frequency band; The third elastic wave device is connected to the antenna terminal and is used to pass a third frequency band; The capacitive element is connected to the antenna terminal; The first switch is used to switch between the antenna terminal and the first elastic wave device on / off; The second switch is used to switch between the antenna terminal and the second elastic wave device on / off; The third switch is used to switch between the antenna terminal and the third elastic wave device on / off; The fourth switch is used to switch between the antenna terminal and the capacitive element on / off; Among them, the second frequency band and the third frequency band are frequency bands with higher frequencies than the first frequency band; the capacitive element is a capacitor or a resonator; when the capacitive element is the resonator, the resonant frequency of the resonator is a frequency higher than the first frequency band and a frequency lower than the second frequency band and the third frequency band.

2. The front-end module according to claim 1, characterized in that: At least one of the first to third switches is in a closed state, and the second frequency band and the third frequency band are frequency bands that at least partially overlap or are adjacent to each other, and the second switch and the third switch are not closed at the same time.

3. The front-end module according to claim 2, characterized in that: When the first switch is in a closed state, and the second switch and the third switch are in an open state, the fourth switch is in a closed state.

4. The front-end module according to claim 1, characterized in that: The resonator is divided into a first divided resonator and a second divided resonator in parallel, and a resonant frequency of the first divided resonator and a resonant frequency of the second divided resonator are different frequencies.

5. The front-end module according to claim 1, characterized in that: The resonator is a SAW resonator, and at least one of the second elastic wave device and the third elastic wave device is an elastic wave device of a SAW filter including a piezoelectric substrate, and the resonator is formed on the piezoelectric substrate.

6. The front-end module according to claim 3, characterized in that: It also includes a fourth elastic wave device and a fifth switch; the fourth elastic wave device is connected to the antenna terminal and is used to pass a fourth frequency band; the fifth switch is used to switch the antenna terminal and the fourth elastic wave device on / off; the fourth frequency band is a frequency band lower than the second frequency band, and when the first switch or the fifth switch is closed and the second switch and the third switch are opened, the fourth switch is closed.

7. The front-end module according to claim 6, characterized in that: When only the fifth switch is closed, the fourth switch is closed.

8. The front-end module according to claim 6, characterized in that: When the third switch and the fifth switch are closed, the fourth switch is open.

9. The front-end module according to claim 3, characterized in that: It also includes a first coil element; the first coil element is connected between the first switch and the first elastic wave device and is grounded.

10. The front-end module according to claim 3, characterized in that: It also includes a second coil element and a third coil element; the second coil element is connected in series between the second switch and the second elastic wave device; the third coil element is connected in series between the third switch and the third elastic wave device.

11. The front-end module according to claim 6, characterized in that: It also includes a fourth coil element; the fourth coil element is connected between the fifth switch and the fourth elastic wave device and is grounded.

12. The front-end module according to claim 3, characterized in that: The equivalent input capacitance of the first elastic wave device is smaller than the equivalent input capacitance of the capacitive element at frequencies outside the second frequency band and at frequencies outside the third frequency band.

13. The front-end module according to claim 3, characterized in that: An equivalent input capacitance of the second elastic wave device is equal to an equivalent input capacitance of the third elastic wave device at a center frequency of the first frequency band.

14. The front-end module according to claim 3, characterized in that: The equivalent input capacitance of the first elastic wave device is smaller than the equivalent input capacitance of the second elastic wave device and the equivalent input capacitance of the third elastic wave device at a frequency outside the first frequency band.

15. The front-end module according to claim 6, characterized in that: The equivalent input capacitance of the second elastic wave device is equal to the equivalent input capacitance of the third elastic wave device at the center frequency of the first frequency band, and is also equal to the equivalent input capacitance of the third elastic wave device at the center frequency of the fourth frequency band.

16. The front-end module according to claim 3 or claim 6, characterized in that: The first elastic wave device includes a first filter and a second filter, wherein the first filter passes frequency band one in the first frequency band; the second filter passes frequency band two in the first frequency band which is higher frequency than frequency band one, and the equivalent input capacitance of the first filter is smaller than the equivalent input capacitance of the second filter at the average of the center frequency of the second frequency band and the center frequency of the third frequency band, i.e., the average center frequency.

17. The front-end module according to claim 6, characterized in that: The fourth elastic wave device includes a third filter and a fourth filter, wherein the third filter passes frequency band three in the fourth frequency band; the fourth filter passes frequency band four in the fourth frequency band which is higher frequency than frequency band three, and the equivalent input capacitance of the third filter is smaller than the equivalent input capacitance of the fourth filter at the average of the center frequency of the second frequency band and the center frequency of the third frequency band, i.e., the average center frequency.

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