Multiplexer and communication equipment

Abstract

The utility model relates to a multiplexer and communication equipment. The multiplexer is characterized in that a first frequency band emission filter is arranged between a common port and a first signal transmission end; the second frequency band transmitting filter is arranged between the public port and the third signal transmission end; the first frequency band receiving filter is arranged between the public port and the second signal transmission end; the second frequency band receiving filter is arranged between the common port and the fourth signal transmission end; a first end of the notch inductor unit is connected with the common port, and a second end of the notch inductor unit is connected with a common node closest to the common port in at least two filters except the first frequency band transmitting filter; the equivalent inductor of the notch inductor unit and the parallel equivalent capacitors of at least two filters except the first frequency band transmitting filter generate series resonance, and the resonant frequency is two times of the passband center frequency of the first frequency band transmitting filter.

Description

Technical Field

[0001] The utility model relates to a communication device, and more particularly to a communication device including a multiplexer and the multiplexer. Background Art

[0002] Portable communication devices, such as mobile phones, laptops, and personal digital assistants

[0003] Personal digital assistants (PDAs), global positioning systems (GPS), and BeiDou (Beidou) require signal acquisition and transmission. Different signals correspond to different frequency ranges. To meet the signal acquisition and transmission needs of portable communication devices, multiplexers have emerged. With the increasing commercial use of 5G, the demand for multiplexers is also increasing.

[0004] Multiplexers typically include multiple filters with different passbands. These filters typically consist of resonant networks composed of resonators. These filters pass desired frequencies while blocking undesirable frequencies. However, these filters also generate harmonics during the filtering process, which can impair the quality of wireless communications within the multiplexer. Therefore, mitigating these harmonics is crucial.

[0005] Existing techniques create harmonic suppression trap circuits in certain transmit filters of multiplexers. This requires the connection of a large trap inductor in series with the common terminals of other filters, hindering chip miniaturization and achieving high Q values. It also easily introduces additional inductive coupling on the substrate on which the multiplexer is mounted. Therefore, it is desirable in the art to provide new approaches to achieve harmonic suppression in multiplexers. Utility Model Content

[0006] In view of the above technical problems, the present invention has carefully designed the circuit structure of the multiplexer, and designed a multiplexer that overcomes the above technical problems and has a steep passband edge roll-off and good suppression between multiple frequency bands.

[0007] The following is a brief overview of the present invention to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important aspects of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is simply to present certain concepts in a simplified form as a prelude to the more detailed description discussed later.

[0008] According to one aspect of the present invention, a multiplexer is provided, comprising: a common port, a notch inductor unit, a first frequency band transmit filter, a first frequency band receive filter, a second frequency band transmit filter, a second frequency band receive filter, a first signal transmission end, a second signal transmission end, a third signal transmission end and a fourth signal transmission end; the first frequency band transmit filter is arranged between the common port and the first signal transmission end; the second frequency band transmit filter is arranged between the common port and the third signal transmission end; the first frequency band receive filter is arranged between the common port and the second signal transmission end; the second frequency band receive filter is arranged between the common port and the fourth signal transmission end; the first end of the notch inductor unit is connected to the common port, and the second end of the notch inductor unit is connected to the common node closest to the common port in at least two filters other than the first frequency band transmit filter; the equivalent inductance of the notch inductor unit and the parallel equivalent capacitance of the at least two filters other than the first frequency band transmit filter resonate in series, and the resonant frequency is twice the passband center frequency of the first frequency band transmit filter.

[0009] Furthermore, the first frequency band transmit filter, the first frequency band receive filter, the second frequency band transmit filter, and the second frequency band receive filter all include multiple series branches and multiple parallel branches; the first series branch of each of at least two filters other than the first frequency band transmit filter is closer to the common port than the first parallel branch in the corresponding filter.

[0010] Furthermore, the frequency interval between the filter directly connected to the second end of the trap inductor unit and the filter at the low frequency of the multiplexer is greater than the minimum value of the bandwidth of the two filters.

[0011] Furthermore, a first matching unit is provided between the common port and the ground potential to offset the capacitive characteristics of the filters in the multiplexer as a whole;

[0012] Furthermore, each of the first frequency band transmit filter, the first frequency band receive filter, the second frequency band transmit filter, and the second frequency band receive filter has a second matching unit.

[0013] Furthermore, the first frequency band transmit filter, the first frequency band receive filter, the second frequency band transmit filter, and the second frequency band receive filter all have a T-type topology structure consisting of four series resonant branches and four parallel resonant branches, each series resonant branch includes at least one thin film bulk acoustic resonator, each parallel resonant branch includes at least one thin film bulk acoustic resonator, and the thin film bulk acoustic resonator in each parallel resonant branch is grounded through a single inductor or through a shared inductor.

[0014] Furthermore, the first frequency band transmit filter is a B25 transmit filter with a passband frequency range of 1850 to 1915 MHz, the first frequency band receive filter is a B25 receive filter with a passband frequency range of 1930 to 2020 MHz, the second frequency band transmit filter is a B66 transmit filter with a passband frequency range of 1695 to 1780 MHz, and the second frequency band receive filter is a B66 receive filter with a passband frequency range of 2110 to 2200 MHz.

[0015] Furthermore, the first matching unit includes an inductor connected between the common port and the ground, and an inductor connected between the common port and the input end of the first frequency band receiving filter; the second matching unit of the first frequency band transmitting filter includes an inductor connected between the first signal transmission end and the ground; the second matching unit of the first frequency band receiving filter includes an inductor connected between the second signal transmission end and the ground, and an inductor connected between the second signal transmission end and the output end of the first frequency band receiving filter, the second matching unit of the second frequency band transmitting filter includes an inductor connected between the third signal transmission end and the ground, and the second matching unit of the second frequency band receiving filter includes an inductor connected between the fourth signal transmission end and the ground.

[0016] Furthermore, a first end of the trap inductor is connected to the common port, and a second end is connected to a common node of an output end of the second frequency band transmit filter and an input end of the second frequency band receive filter.

[0017] According to another aspect of the present invention, a communication device is provided, comprising any one of the multiplexers described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The following description of the present invention will provide a more comprehensive understanding of the above and other purposes, features, and advantages of the present invention, with reference to the accompanying drawings. The accompanying drawings are intended only to illustrate the principles of the present invention. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale.

[0019] Figure 1 A schematic diagram of the circuit structure of the quadplexer provided by the present invention is shown;

[0020] Figure 2 A schematic diagram showing the specific circuit structure of the quadplexer provided by the present invention is shown;

[0021] Figure 3 for Figure 2 Schematic diagram of the equivalent circuit for harmonic suppression.

[0022] Figure 4a shows the input impedance curve of the common port of the multiplexer;

[0023] Figure 4b Shows the multiplexer passband matching curve. DETAILED DESCRIPTION

[0024] The following describes exemplary embodiments of the present invention in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features that implement the present invention are described in this specification. However, it should be understood that in developing any such implementation of the present invention, many decisions specific to the invention may be made to achieve the developer's specific goals, and these decisions may vary from one invention to another.

[0025] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, the accompanying drawings only show device structures closely related to the solutions according to the present invention, while other details that are not closely related to the present invention are omitted.

[0026] It should be understood that the present invention is not limited to the described embodiments due to the following description with reference to the accompanying drawings. In the present invention, features between different embodiments may be replaced or borrowed, and one or more features may be omitted in one embodiment, where feasible.

[0027] The following uses a quadplexer as an example to explain this solution in detail. Figure 1 , Figure 1 The circuit structure block diagram of the quadplexer provided by the present invention is shown, which includes a common port A, a first frequency band transmit filter 100, a second frequency band transmit filter 200, a first frequency band receive filter 110, a second frequency band receive filter 210 and a notch unit 300.

[0028] The common port A is an external port for sending and receiving radio waves through an antenna element (not shown in the figure); the first frequency band transmitting filter 100 is arranged between the common port A and the first signal transmission terminal TP1; the first frequency band receiving filter 110 is arranged between the common port A and the second signal transmission terminal RP1; the second frequency band transmitting filter 200 is arranged between the common port A and the third signal transmission terminal TP2, and the second frequency band receiving filter 210 is arranged between the common port A and the fourth signal transmission terminal RP2.

[0029] A first matching unit MC1 is provided between the common port A and each filter. Since the first-band transmit filter 100, the first-band receive filter 110, the second-band transmit filter 200, and the second-band receive filter 210 exhibit capacitive characteristics, the inductive first matching unit MC1 is provided to offset the capacitive characteristics of the filters in the quadplexer as a whole, thereby achieving impedance matching among the first-band transmit filter 100, the first-band receive filter 110, the second-band transmit filter 200, and the second-band receive filter 210, thereby preventing insertion loss degradation. The first matching unit MC1 can be connected in parallel between the common port A and ground, or in series between a particular filter and the common port. Alternatively, the first matching unit MC1 can be a multi-port unit with one end connected to the common port, one end connected to the ground, and at least one end connected to the signal transmission end of a particular filter near the common port.

[0030] Furthermore, the first-band transmit filter 100 includes a first filter network disposed between the input and output of the first-band transmit filter 100. The first-band receive filter 110 includes a second filter network disposed between the input and output of the first-band receive filter 110. The second-band transmit filter 200 includes a third filter network disposed between the input and output of the second-band transmit filter 200. The second-band receive filter 210 includes a fourth filter network disposed between the input and output of the second-band receive filter 210.

[0031] The following description uses the first filter network in the first-band transmit filter 100 as a representative example. The first filter network is disposed between the input and output of the first-band transmit filter 100. The first filter network includes series and parallel branches, where the boxes within the series and parallel branches represent resonant units. A resonant unit can be composed of LC lumped elements, or one or more acoustic resonators. When a resonant unit includes multiple acoustic resonators, the multiple resonators are connected in series and / or in parallel. Alternatively, a resonant unit can be composed of different types of devices, such as an LC lumped element and an SMR acoustic resonator, an SMR acoustic resonator and an FBAR acoustic resonator, or an LC lumped element and an FBAR acoustic resonator. Each parallel branch of the filter may also include an inductor connected to ground. Furthermore, when different resonant units contain components of the same type, the component parameters can be equal or unequal. For example, when different resonant units contain inductors, the inductors can be equal or unequal in size.

[0032] It can be understood that the second filtering network in the first frequency band receiving filter 110, the third filtering network in the second frequency band transmitting filter 200, and the fourth filtering network in the second frequency band receiving filter 210 also include series branches and parallel branches. The setting method of the series branches and parallel branches in each filtering network refers to the setting method of the first filtering network in the first frequency band transmitting filter 100, and will not be repeated here.

[0033] When harmonic suppression is required for the first frequency band transmit filter in the quadplexer, the first end of the trap inductor unit 300 is connected to the common port A, and the second end is connected to the common node C closest to the common port in at least two filters other than the first frequency band transmit filter.

[0034] The trap inductor unit 300 is equivalent to an inductor Lx. Since all filters are capacitive, the at least two filters connected to the second end of the trap inductor unit 300 are equivalent to at least two capacitors connected in parallel. In the present invention, the inductor Lx and the at least two capacitors connected in parallel are connected in series resonance, and the resonant frequency is set to twice the passband center frequency of the first frequency band transmit filter requiring harmonic suppression, thereby suppressing the signal strength of the transmit filter's second harmonic.

[0035] Furthermore, the frequency interval between the filter directly connected to the second end of the notch inductor unit 300 and other filters at the low frequency in the quadplexer is greater than the minimum value of their bandwidths, so as to avoid impedance mismatch of the multiplexer caused by the introduction of the notch inductor unit 300.

[0036] Furthermore, in at least two parallel-connected filters directly connected to the second end of the trap inductor unit 300, the series branch should be closer to the common end than the parallel branch to take into account both matching and trap point setting. Otherwise, the trap point cannot be adjusted to twice the passband center frequency of the transmitting filter that requires harmonic suppression, that is, the second harmonic cannot be effectively suppressed.

[0037] Further, such as Figure 1 As shown, at least one of the first-band receive filter 110, the second-band receive filter 210, the first-band transmit filter 100, and the second-band transmit filter 200 in the quadplexer of the present invention may include a second matching unit MC2. Specifically, the second matching circuit MC2 may be provided at at least one of the following: the first signal transmission port TP1 of the first-band transmit filter 100, the second transmit port TP2 of the second-band transmit filter 200, the first receive port RP1 of the first-band receive filter 110, and the fourth signal transmission port RP2 of the second-band receive filter 210.

[0038] Furthermore, when the second matching unit MC2 is disposed at the first signal transmission terminal TP1 of the first-band transmit filter 100, it can be disposed in series between the input terminal of the first-band transmit filter 100 and the first signal transmission terminal TP1, or the second matching unit MC2 can be disposed in parallel between the input terminal of the first-band transmit filter 100 and the ground potential. In this case, the second matching unit MC2 is used to match the impedance of the first-band transmit filter 100 itself to avoid signal reflection and signal loss. The second matching unit MC2 can be various series and parallel combinations of capacitors and / or inductors.

[0039] It can be understood that when the second matching unit MC2 is set at the second transmitting port TP2 of the second frequency band transmitting filter 200, the first receiving port RP1 of the first frequency band receiving filter 110, and the fourth signal transmission end RP2 of the second frequency band receiving filter 210, the manner and function are the same as when the second matching unit MC2 is set at the first signal transmission end TP1 of the first frequency band transmitting filter 100, and no further details are given here.

[0040] See also Figure 2 , Figure 2 A schematic diagram of the specific circuit structure of the quadplexer provided by the present invention is shown. The quadplexer includes at least a B25 transmit filter 100, a B25 receive filter 110, a B66 transmit filter 200, a B66 transmit filter 210, and a first matching unit MC1. The passband frequency range of the B25 transmit filter is 1850-1915 MHz, and the passband frequency range of the B25 receive filter is 1930-2020 MHz; the passband frequency range of the B66 transmit filter is 1695-1780 MHz, and the passband frequency range of the B66 receive filter is 2110-2200 MHz. The B25 transmit filter 100, the B25 receive filter 110, the B66 transmit filter 200, and the B66 receive filter 210 correspond to the first frequency band transmit filter, the first frequency band receive filter, the second frequency band transmit filter, and the second frequency band receive filter, respectively.

[0041] The B25 transmit filter 100 is arranged between the common port A and the first signal transmission terminal B25TP; the B25 receive filter 110 is arranged between the common port A and the second signal transmission terminal B25RP; the B66 transmit filter 200 is arranged between the common port A and the third signal transmission terminal B66RP; the B66 receive filter 210 is arranged between the common port A and the fourth signal transmission terminal B66TP.

[0042] The first matching unit includes an inductor Lm1 and an inductor Lm2. The first end of the inductor Lm1 is connected to the common port A, and the second end of the inductor Lm1 is grounded. The first end of the inductor Lm2 is connected to the common port A, and the second end of the inductor Lm2 is connected to the input end of the B25 receive filter 110.

[0043] A first end of the trap inductor Lx is connected to the common port A, and a second end of the trap inductor Lx is connected to the output end of the B66 transmit filter 200 and the input end of the B66 receive filter 210 .

[0044] The B25 transmit filter 100 has four series resonant branches and four parallel resonant branches. The first series resonant branch includes a series resonator S1 formed by a thin film bulk acoustic resonator, the second series resonant branch includes a series resonator S2 formed by a thin film bulk acoustic resonator, the third series resonant branch includes a series resonator S3 formed by a thin film bulk acoustic resonator, and the fourth series resonant branch includes a series resonator S4 formed by a thin film bulk acoustic resonator. Connection nodes N1-N3 are provided between the first series resonant branch and the fourth series resonant branch. The first parallel resonant branch includes a first parallel resonator P1 and an inductor L1. The first end of the first parallel resonator P1 is connected to node N1, the second end of the first parallel resonator P1 is connected to the first end of the inductor L1, and the second end of the inductor L1 is grounded. The second parallel resonant branch includes a second parallel resonator P2 and an inductor L2. The first end of the second parallel resonator P2 is connected to node N2, the second end of the second parallel resonator P2 is connected to the first end of the inductor L2, and the second end of the inductor L2 is grounded. The third parallel resonant branch includes a third parallel resonator P3. The first end of the third parallel resonator P3 is connected to node N3, the second end of the third parallel resonator P3 is connected to the first end of the shared inductor L3, and the second end of the inductor L3 is grounded. The fourth parallel resonant branch includes a fourth parallel resonator P4. The first end of the fourth parallel resonator P4 is connected to the first signal transmission terminal B25TP, the second end of the fourth parallel resonator P4 is connected to the first end of the shared inductor L3, and the second end of the inductor L3 is grounded. Furthermore, a matching inductor L4 is provided between the first signal transmission terminal B25TP and the ground to match the impedance of the B25 transmit filter 100 itself.

[0045] The B25 receive filter 110 has four series resonant branches and four parallel resonant branches. The fifth series resonant branch includes a series resonator S5 formed by a thin film bulk acoustic resonator (FBAR). The sixth series resonant branch includes a series resonator S6 formed by a thin film bulk acoustic resonator (FBAR). The seventh series resonant branch includes a series resonator S7 formed by a thin film bulk acoustic resonator (FBAR). The eighth series resonant branch includes a series resonator S8 formed by a thin film bulk acoustic resonator (FBAR). Connection nodes N4-N6 are located between the fifth and eighth series resonant branches. The fifth parallel resonant branch includes a fifth parallel resonator P5, with a first end connected to the second end of inductor Lm2, a second end connected to the first end of shared inductor L5, and a second end of shared inductor L5 connected to ground. The sixth parallel resonant branch includes a sixth parallel resonator P6, with a first end connected to node N4 and a second end connected to the first end of shared inductor L5. The seventh parallel resonant branch includes a seventh parallel resonator P7 and an inductor L6. The first end of the seventh parallel resonator P7 is connected to the node N5, the second end of the seventh parallel resonator P7 is connected to the first end of the inductor L6, and the second end of the inductor L6 is grounded. The eighth parallel resonant branch includes an eighth parallel resonator P8 and an inductor L7. The first end of the eighth parallel resonator P8 is connected to the node N6, the second end of the eighth parallel resonator P4 is connected to the first end of the inductor L7, and the second end of the inductor L7 is grounded. Furthermore, a matching inductor L8 is provided between the second end of the eighth parallel resonator P4 and the second signal transmission terminal B25RP, and a matching inductor L9 is provided between the second signal transmission terminal B25Rx and the ground. Inductor L8 and inductor L9 are used to match the impedance of the B25 transmit filter 100 itself.

[0046] The B66 transmit filter 200 has four series resonant branches and four parallel resonant branches. The ninth series resonant branch includes a series resonator S9 formed by a thin film bulk acoustic resonator (FBAR). The tenth series resonant branch includes a series resonator S10 formed by a thin film bulk acoustic resonator (FBAR). The eleventh series resonant branch includes a series resonator S11 formed by a thin film bulk acoustic resonator (FBAR). The twelfth series resonant branch includes a series resonator S12 formed by a thin film bulk acoustic resonator (FBAR). Connection nodes N7-N9 are located between the first series resonant branch and the fourth series resonant branch. The ninth parallel resonant branch includes a first parallel resonator P9 and an inductor L10. The first end of the first parallel resonator P1 is connected to node N7, the second end of the first parallel resonator P1 is connected to the first end of the inductor L10, and the second end of the inductor L10 is grounded. The tenth parallel resonant branch includes a tenth parallel resonator P10 and an inductor L11. The first end of the tenth parallel resonator P10 is connected to node N8, the second end of the tenth parallel resonator P10 is connected to the first end of the inductor L11, and the second end of the inductor L11 is grounded. The eleventh parallel resonant branch includes an eleventh parallel resonator P11. The first end of the eleventh parallel resonator P11 is connected to node N9, the second end of the third parallel resonator P11 is connected to the first end of the shared inductor L12, and the second end of the inductor L12 is grounded. The twelfth parallel resonant branch includes a twelfth parallel resonator P12. The first end of the twelfth parallel resonator P12 is connected to the first end of the inductor L12, the second end of the inductor L13 is connected to the third signal transmission terminal B66TP, and the second end of the twelfth parallel resonator P12 is connected to the first end of the shared inductor L12. Furthermore, a matching inductor L13 is provided between the third signal transmission terminal B66Tx and the ground, and the inductor L13 is used to match the impedance of the 66 transmit filter 200 itself.

[0047] The B66 receive filter 210 has four series resonant branches and four parallel resonant branches. The thirteenth series resonant branch includes a series resonator S13 formed by a thin film bulk acoustic resonator (FBAR). The fourteenth series resonant branch includes a series resonator S14 formed by a thin film bulk acoustic resonator (FBAR). The fifteenth series resonant branch includes a series resonator S15 formed by a thin film bulk acoustic resonator (FBAR). The sixteenth series resonant branch includes a series resonator S16 formed by a thin film bulk acoustic resonator (FBAR). Connection nodes N10-N12 are located between the thirteenth and sixteenth series resonant branches. The thirteenth parallel resonant branch includes a thirteenth parallel resonator P13 and an inductor L14. The first end of the thirteenth parallel resonator P13 is connected to node N10, the second end of the thirteenth parallel resonator P13 is connected to the first end of the inductor L14, and the second end of the inductor L14 is grounded. The fourteenth parallel resonant branch includes a fourteenth parallel resonator P14 and an inductor L15. The first end of the fourteenth parallel resonator P14 is connected to node N11, the second end of the fourteenth parallel resonator P14 is connected to the first end of the inductor L15, and the second end of the inductor L15 is grounded. The fifteenth parallel resonant branch includes a fifteenth parallel resonator P15. The first end of the fifteenth parallel resonator P15 is connected to node N12, the second end of the fifteenth parallel resonator P15 is connected to the first end of the shared inductor L16, and the second end of the inductor L16 is grounded. The sixteenth parallel resonant branch includes a sixteenth parallel resonator P16. The first end of the sixteenth parallel resonator P16 is connected to the fourth signal transmission terminal B66RP, and the second end of the sixteenth parallel resonator P16 is connected to the first end of the shared inductor L16. Furthermore, a matching inductor L17 is provided between the fourth signal transmission terminal B66Rx and ground to match the impedance of the B66 receive filter 210 itself.

[0048] See also Figure 3 , Figure 3 for Figure 2 Schematic diagram of the equivalent circuit for harmonic suppression. Figure 3 As shown, the B66 transmit filter 200 is equivalent to the capacitor Cx1, and the B66 receive filter 210 is equivalent to the capacitor Cx2. The capacitors Cx1 and Cx2 are connected in parallel. One end of the trap inductor Lx is connected to the common port A. The other end of the trap inductor Lx is connected to the first common end of the parallel capacitors Cx1 and Cx2. The second common end of the parallel capacitors Cx1 and Cx2 is grounded. And by setting the parameters of each device in the quadplexer, the B25 transmit filter is made To suppress the signal strength of the second harmonic of the B25 transmit filter. It should be noted that Figure 2The ninth series resonant branch of the B66 transmitting filter 200 connected to the notch inductor Lx should be closer to the common port A than the ninth parallel resonant branch; and the thirteenth series resonant branch of the B66 receiving filter 210 connected to the notch inductor Lx should be closer to the common port A than the thirteenth parallel resonant branch; so that both matching and notch point setting can be taken into account, otherwise the notch point cannot be adjusted to 2f0 of the B25 transmitting filter.

[0049] The quadplexer provided by the present invention connects the notch unit in series between multiple filters and the common port A. Compared with a structure in which the notch unit is only connected in series with a single filter and the common port A, the inductance value can be reduced, the integration is facilitated, and the Q value of the quadplexer is improved. By setting the parameters of the quadplexer, harmonic suppression is created for a certain transmit filter, and chip miniaturization and a high Q value can be better achieved.

[0050] See Figure 4a-4b , Figure 4a The input impedance curve of the multiplexer common port is shown. Figure 4b The passband matching curve of the multiplexer is shown in FIG. Figure 4a It can be seen that due to the common effect of the notch inductor, the B66 transmit filter and the B66 receive filter, a notch point is formed at 2f0 of the B25 transmit filter, which can improve the second harmonic suppression by about 10db. Figure 4b It can be seen that the return loss of the four filter passbands is around 15dB, and the matching is good.

[0051] Furthermore, the quadplexer can be used in communication devices, exemplified by mobile phones, personal digital assistants, electronic game devices, wearable terminals, and the like.

[0052] The present invention has been described above with reference to specific embodiments. However, those skilled in the art should understand that these descriptions are merely illustrative and do not limit the scope of protection of the present invention. Those skilled in the art may make various variations and modifications to the present invention based on the spirit and principles of the present invention, and such variations and modifications are also within the scope of the present invention.

Claims

1. A multiplexer, characterized in that: include: A common port, a trap inductor unit, a first frequency band transmit filter, a first frequency band receive filter, a second frequency band transmit filter, a second frequency band receive filter, a first signal transmission end, a second signal transmission end, a third signal transmission end, and a fourth signal transmission end; The first frequency band transmission filter is arranged between the common port and the first signal transmission end; The second frequency band transmission filter is arranged between the common port and the third signal transmission end; The first frequency band receiving filter is arranged between the common port and the second signal transmission end; The second frequency band receiving filter is arranged between the common port and the fourth signal transmission end; The first end of the trap inductor unit is connected to the common port, and the second end of the trap inductor unit is connected to a common node closest to the common port in at least two filters except the first frequency band transmit filter; The equivalent inductance of the trap inductor unit resonates in series with the parallel equivalent capacitance of at least two filters except the first frequency band transmit filter, and the resonant frequency is twice the passband center frequency of the first frequency band transmit filter.

2. The multiplexer according to claim 1, wherein: The first frequency band transmit filter, the first frequency band receive filter, the second frequency band transmit filter, and the second frequency band receive filter all include multiple series branches and multiple parallel branches; the first series branch of each of at least two filters other than the first frequency band transmit filter is closer to the common port than the first parallel branch in the corresponding filter.

3. The multiplexer according to claim 1 or 2, wherein: The frequency interval between the filter directly connected to the second end of the trap inductor unit and the filter at the low frequency of the multiplexer is greater than the minimum value of the bandwidth of the two filters.

4. The multiplexer according to claim 3, wherein: A first matching unit is provided between the common port and the ground potential, for offsetting the capacitive characteristics of the filters in the multiplexer as a whole.

5. The multiplexer according to claim 4, wherein: The first frequency band transmitting filter, the first frequency band receiving filter, the second frequency band transmitting filter, and the second frequency band receiving filter each have a second matching unit.

6. The multiplexer according to claim 5, wherein: The first frequency band transmit filter, the first frequency band receive filter, the second frequency band transmit filter, and the second frequency band receive filter all have a T-type topology structure consisting of four series resonant branches and four parallel resonant branches. Each series resonant branch includes at least one thin film bulk acoustic resonator, and each parallel resonant branch includes at least one thin film bulk acoustic resonator. The thin film bulk acoustic resonator in each parallel resonant branch is grounded through a single inductor or through a shared inductor.

7. The multiplexer according to claim 6, wherein: The first frequency band transmit filter is a B25 transmit filter with a passband frequency range of 1850 to 1915 MHz, the first frequency band receive filter is a B25 receive filter with a passband frequency range of 1930 to 2020 MHz, the second frequency band transmit filter is a B66 transmit filter with a passband frequency range of 1695 to 1780 MHz, and the second frequency band receive filter is a B66 receive filter with a passband frequency range of 2110 to 2200 MHz.

8. The multiplexer according to claim 7, wherein: The first matching unit includes an inductor connected between the common port and the ground, and an inductor connected between the common port and the input end of the first frequency band receiving filter; the second matching unit of the first frequency band transmitting filter includes an inductor connected between the first signal transmission end and the ground; the second matching unit of the first frequency band receiving filter includes an inductor connected between the second signal transmission end and the ground, and an inductor connected between the second signal transmission end and the output end of the first frequency band receiving filter, the second matching unit of the second frequency band transmitting filter includes an inductor connected between the third signal transmission end and the ground, and the second matching unit of the second frequency band receiving filter includes an inductor connected between the fourth signal transmission end and the ground.

9. The multiplexer according to claim 8, wherein: A first end of the trap inductor is connected to the common port, and a second end of the trap inductor is connected to a common node of an output end of the second frequency band transmit filter and an input end of the second frequency band receive filter.

10. A communication device, characterized in that: The communication device includes the multiplexer according to any one of claims 1 to 9.

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