A duplexer

Abstract

The present invention provides a duplexer, including a transmission filter and a receiving filter, the transmission filter includes a first resonator and a second resonator, the first resonator is connected in series between an antenna terminal and a transmission terminal, and the second resonator is connected in parallel between the antenna terminal and the transmission terminal; the receiving filter includes a third resonator, a fourth resonator, a first inductor, a fifth resonator and a sixth resonator, the third resonator, the fourth resonator and the fifth resonator are connected in series between the antenna terminal and the receiving terminal in sequence, the first inductor is connected in parallel between the third resonator and the fourth resonator, and the sixth resonator is connected in parallel between the fourth resonator and the receiving terminal; or the first inductor and the fifth resonator are connected in series between the antenna terminal and the receiving terminal in sequence, the third resonator and the fourth resonator are respectively connected in parallel at both ends of the first inductor, and the sixth resonator is connected in parallel between the fifth resonator and the receiving terminal. The duplexer provided by the present invention is small in size and easy to integrate.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a duplexer. Background Art

[0002] The duplexer is one of the key components of modern intelligent communication devices (such as smartphones, etc.). The duplexer mainly includes filters suitable for the transmission frequency band (hereinafter referred to as the transmission filter) and filters suitable for the reception frequency band (hereinafter referred to as the reception filter). Please refer to Figure 1 , Figure 1 It is a structural diagram of a duplexer in the prior art. As shown in the figure, the transmit filter 1 is arranged between the antenna terminal 4 and the transmit terminal 5, and the receive filter 2 is arranged between the antenna terminal 4 and the receive terminal 6. The transmit filter 1 and the receive filter 2 are generally designed as a ladder network structure. Specifically, the transmit filter 1 and the receive filter 2 each include one or more series resonators and one or more parallel resonators. For the transmit filter 1, the one or more series resonators are connected in series between the antenna terminal 4 and the transmit terminal 5, and the one or more parallel resonators are connected in parallel between the antenna terminal 4 and the receive terminal 6. For the receive filter 2, the one or more series resonators are connected in series between the antenna terminal 4 and the transmit terminal 5, and the one or more parallel resonators are connected in parallel between the antenna terminal 4 and the receive terminal 6. In some specific application scenarios, the input impedance (here refers to the amplitude) of the transmit filter 1 seen from the antenna terminal 4 is typically high in the receive frequency band, while the input impedance (here refers to the amplitude) of the receive filter 2 seen from the antenna terminal is typically low in the transmit frequency band. In this case, the receive filter 2 will have a large load effect on the transmit filter 1, thereby causing its passband to deteriorate. In order to solve the above problems, Figure 1 As shown, a matching network 3 may be connected in series between the antenna terminal 4 and the receiving filter 2 to perform impedance matching.

[0003] In the prior art, the matching network is usually composed of an inductor and a capacitor. Among them, the inductor can be easily realized through the routing on the chip, but the capacitor is difficult to integrate in the chip, so the capacitor is usually set independently of the chip. This design method is not conducive to the miniaturization of the duplexer. Summary of the invention

[0004] In order to overcome the above-mentioned defects in the prior art, the present invention provides a duplexer, the duplexer comprising:

[0005] A transmitting filter, a receiving filter, an antenna terminal, a transmitting terminal, and a receiving terminal;

[0006] The transmission filter comprises at least one first resonator and at least one second resonator, wherein the at least one first resonator is connected in series between the antenna terminal and the transmission terminal, and the at least one second resonator is connected in parallel between the antenna terminal and the transmission terminal;

[0007] The receive filter includes a third resonator, a fourth resonator, a first inductor, at least one fifth resonator and at least one sixth resonator, wherein the third resonator, the fourth resonator and the at least one fifth resonator are sequentially connected in series between the antenna terminal and the receive terminal, the first inductor is connected in parallel between the third resonator and the fourth resonator, and the at least one sixth resonator is connected in parallel between the fourth resonator and the receive terminal; or the first inductor and the at least one fifth resonator are sequentially connected in series between the antenna terminal and the receive terminal, the third resonator and the fourth resonator are respectively connected in parallel at both ends of the first inductor, and the at least one sixth resonator is connected in parallel between the fifth resonator and the receive terminal.

[0008] According to one aspect of the present invention, in the duplexer, the third resonator and the fourth resonator have the same static capacitance value; the resonant frequency of the third resonator is less than or equal to the resonant frequency of the fifth resonator; and the resonant frequency of the fourth resonator is less than or equal to the resonant frequency of the fifth resonator.

[0009] According to another aspect of the present invention, in the duplexer, when the resonant frequencies of the third resonator, the fourth resonator and the fifth resonator are the same, the receive filter further includes a second inductor having one end connected to the receive terminal and the other end connected to ground.

[0010] According to still another aspect of the present invention, in the duplexer, the transmission filter further includes a third inductor, one end of the third inductor is connected to the transmission terminal, and the other end of the third inductor is connected to the ground.

[0011] According to still another aspect of the present invention, in the duplexer, the inductance value of the second inductor is smaller than the inductance value of the third inductor.

[0012] The receiving filter in the duplexer provided by the present invention is composed of a resonator and an inductor, and the input impedance of the receiving filter viewed from the antenna terminal is higher in the transmission frequency band by utilizing the capacitive characteristic of the resonator at the non-resonant frequency. In this way, there is no need to set up a matching network as in the prior art, thereby avoiding the use of capacitors, which is not only beneficial to chip integration but also conducive to the miniaturization of the duplexer. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0014] Figure 1 It is a structural schematic diagram of a duplexer in the prior art;

[0015] Figure 2 is a circuit diagram of a duplexer according to a specific embodiment of the present invention;

[0016] Figure 3 is a circuit diagram of a duplexer according to another specific embodiment of the present invention;

[0017] Figure 4 is a circuit diagram of a duplexer according to another specific embodiment of the present invention;

[0018] Figure 5 yes Figure 4 The relationship between the input impedance (amplitude) of the transmit filter in the duplexer as seen from the antenna terminal and the frequency is shown;

[0019] Figure 6 yes Figure 4 The relationship between the input impedance (amplitude) of the receive filter in the duplexer as seen from the antenna terminal and the frequency is shown;

[0020] Figure 7 yes Figure 4 A graph showing the relationship between insertion loss and frequency of the transmit filter in the duplexer shown;

[0021] Figure 8 yes Figure 4 A graph showing the relationship between insertion loss and frequency of the receive filter in the duplexer shown;

[0022] Fig. 9 yes Figure 4 A graph showing the relationship between out-of-band rejection and frequency of the duplexer is shown;

[0023] Fig.10 yes Figure 4 A graph showing the relationship between duplexer isolation and frequency;

[0024] Fig.11 is a circuit diagram of a duplexer according to another specific embodiment of the present invention;

[0025] Fig.12 yes Fig.11 A diagram showing the relationship between the impedance phase and the frequency of the third resonator in the receiving filter of the duplexer shown;

[0026] Fig.13 yes Fig.11A diagram showing the relationship between phase shift and frequency in a T-shaped network structure in a receiving filter of the duplexer shown;

[0027] Fig.14 yes Fig.11 The relationship between the insertion loss and frequency of the T-shaped network structure in the receiving filter of the duplexer shown;

[0028] Fig.15 yes Fig.11 Insertion loss vs. frequency for the receive filter in the duplexer shown.

[0029] The same or similar reference numerals in the drawings represent the same or similar components. DETAILED DESCRIPTION

[0030] In order to better understand and illustrate the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] The present invention provides a duplexer, the duplexer comprising:

[0032] A transmitting filter, a receiving filter, an antenna terminal, a transmitting terminal, and a receiving terminal;

[0033] The transmission filter comprises at least one first resonator and at least one second resonator, wherein the at least one first resonator is connected in series between the antenna terminal and the transmission terminal, and the at least one second resonator is connected in parallel between the antenna terminal and the transmission terminal;

[0034] The receive filter includes a third resonator, a fourth resonator, a first inductor, at least one fifth resonator and at least one sixth resonator, wherein the third resonator, the fourth resonator and the at least one fifth resonator are sequentially connected in series between the antenna terminal and the receive terminal, the first inductor is connected in parallel between the third resonator and the fourth resonator, and the at least one sixth resonator is connected in parallel between the fourth resonator and the receive terminal; or the first inductor and the at least one fifth resonator are sequentially connected in series between the antenna terminal and the receive terminal, the third resonator and the fourth resonator are respectively connected in parallel at both ends of the first inductor, and the at least one sixth resonator is connected in parallel between the fifth resonator and the receive terminal.

[0035] Next, we will combine Figure 2 and Figure 3 Each component of the above duplexer is described in detail.

[0036] Specifically, the duplexer provided by the present invention includes a transmitting filter, a receiving filter, an antenna terminal, a transmitting terminal and a receiving terminal, wherein the transmitting filter is arranged between the antenna terminal and the transmitting terminal, and the receiving filter is arranged between the antenna terminal and the receiving terminal.

[0037] The transmit filter is a ladder network structure, which includes at least one first resonator and at least one second resonator, wherein the at least one first resonator is connected in series between the antenna terminal and the transmit terminal, and the at least one second resonator is connected in parallel between the antenna terminal and the transmit terminal, specifically, one end of the second resonator is connected between the antenna terminal and the transmit terminal, and the other end is grounded. In some specific application scenarios, the second resonator can also be connected to the ground through an inductor. Figure 2 and Figure 3 is a circuit diagram of a duplexer according to two specific embodiments of the present invention, wherein: Figure 2 and Figure 3 The structure of the transmit filter is the same as that of the Figure 2 A specific embodiment of the transmission filter is described by taking FIG. Figure 2 The duplexer shown is suitable for Band 7 frequency band, in which 2500 MHz-2570 MHz is the transmitting frequency band and 2620 MHz-2690 MHz is the receiving frequency band. Figure 2 The transmitting filter 10 in the duplexer shown includes four first resonators (resonator 101, resonator 102, resonator 103 and resonator 104 respectively in the figure), four second resonators (resonator 105, resonator 106, resonator 107 and resonator 108 respectively in the figure), and four first grounding inductors (respectively shown as inductor 109, inductor 110, inductor 111 and inductor 112 in the figure). Among them, resonator 101, resonator 102, resonator 103 and resonator 104 are connected in series between antenna terminal 30 and transmitting terminal 40, one end of resonator 105 is connected between resonator 101 and resonator 102, and the other end is grounded through inductor 109, one end of resonator 106 is connected between resonator 102 and resonator 103, and the other end is grounded through inductor 110, one end of resonator 107 is connected between resonator 103 and resonator 104, and the other end is grounded through inductor 111, and one end of resonator 108 is connected between resonator 104 and transmitting terminal 40, and the other end is grounded through inductor 112. It can be understood by those skilled in the art that the transmitting filter should not be limited to the above-mentioned Figure 2In the structure shown, the specific number and specific layout of the first resonator, the second resonator and the first ground inductor in the transmitting filter can be determined according to the actual design requirements. Taking into account the many applicable scenarios of the duplexer, the number and layout of the first resonator, the second resonator and the first ground inductor included therein are also many possibilities, so for the sake of simplicity, all possible structures of the transmitting filter are no longer listed here. In addition, it should be noted that in this embodiment, the first resonator and the second resonator are both implemented using thin film bulk acoustic wave resonators. In other embodiments, the first resonator and the second resonator can also be implemented using other conventional resonators such as surface acoustic wave resonators.

[0038] The receiving filter includes a third resonator, a fourth resonator, a first inductor, at least one fifth resonator and at least one sixth resonator, wherein the third resonator, the fourth resonator, the first inductor, at least one fifth resonator and at least one sixth resonator have two layout modes.

[0039] The first layout is as follows: the third resonator, the fourth resonator, and at least one fifth resonator are connected in series between the antenna terminal and the receiving terminal in sequence; the first inductor is connected in parallel between the third resonator and the fourth resonator, specifically, one end of the first inductor is connected to between the third resonator and the fourth resonator, and the other end is grounded; at least one sixth resonator is connected in parallel between the fourth resonator and the receiving terminal, specifically, one end of the sixth resonator is connected to between the fourth resonator and the receiving terminal, and the other end is grounded. In some specific application scenarios, the sixth resonator can also be connected to the ground through an inductor. The above layout is illustrated with a specific embodiment. As Figure 2As shown, the receiving filter 20 includes a third resonator (shown as resonator 201 in the figure), a fourth resonator (shown as resonator 202 in the figure), a first inductor (shown as inductor 210 in the figure), three fifth resonators (shown as resonator 203, resonator 204 and resonator 205 in the figure respectively), four sixth resonators (shown as resonator 206, resonator 207, resonator 208 and resonator 209 in the figure respectively), and four second grounding inductors (shown as inductor 211, inductor 212, inductor 213 and inductor 214 in the figure respectively). Among them, resonator 201, resonator 202, resonator 203, resonator 204 and resonator 205 are connected in series between antenna terminal 30 and receiving terminal 50 in sequence, one end of inductor 201 is connected between resonator 201 and resonator 202, and the other end is grounded. One end of the resonator 206 is connected between the resonator 202 and the resonator 203, and the other end is grounded through the inductor 211. One end of the resonator 207 is connected between the resonator 203 and the resonator 204, and the other end is grounded through the inductor 212. One end of the resonator 208 is connected between the resonator 204 and the resonator 205, and the other end is grounded through the inductor 213. One end of the resonator 209 is connected between the resonator 205 and the receiving terminal 50, and the other end is connected between the resonator 208 and the inductor 213 through the inductor 214. It can be understood by those skilled in the art that the receiving filter should not be limited to the above. Figure 2 In the structure shown, the specific number and specific layout of the fifth resonator, the sixth resonator and the second ground inductor in the receiving filter can be determined according to actual design requirements. Considering that the duplexer has many applicable scenarios, the number and layout of the fifth resonator, the sixth resonator and the second ground inductor included therein are also many possibilities. Therefore, for the sake of simplicity, all possible structures of the transmitting filter under the first layout mode are no longer listed one by one.

[0040] The second layout is as follows: the first inductor and at least one fifth resonator are connected in series between the antenna terminal and the receiving terminal in sequence; the third resonator and the fourth resonator are respectively connected in parallel at both ends of the first inductor, specifically, one end of the third resonator is connected between the antenna terminal and the first inductor, and the other end is grounded, and one end of the fourth resonator is connected between the first inductor and the fifth resonator, and the other end is grounded; at least one sixth resonator is connected in parallel between the fifth resonator and the receiving terminal, specifically, one end of the sixth resonator is connected between the fifth resonator and the receiving terminal, and the other end is grounded. The above layout is described with a specific embodiment. Figure 3As shown, the receiving filter 20 includes a third resonator (shown as resonator 305 in the figure), a fourth resonator (shown as resonator 306 in the figure), a first inductor (shown as inductor 301 in the figure), three fifth resonators (shown as resonator 302, resonator 303 and resonator 304 in the figure), three sixth resonators (shown as resonator 307, resonator 308 and resonator 309 in the figure), and three second grounding inductors (shown as inductor 310, inductor 311 and inductor 312 in the figure). Among them, inductor 301, resonator 302, resonator 303 and resonator 304 are connected in series between antenna terminal 30 and receiving terminal 50 in sequence, and one end of resonator 305 is connected between antenna terminal 30 and inductor 301, and the other end is grounded. One end of the resonator 306 is connected between the inductor 301 and the resonator 302, and the other end is grounded. One end of the resonator 307 is connected between the resonator 302 and the resonator 303, and the other end is grounded through the inductor 310. One end of the resonator 308 is connected between the resonator 303 and the resonator 304, and the other end is grounded through the inductor 311. One end of the resonator 309 is connected between the resonator 304 and the receiving terminal 50, and the other end is connected between the resonator 308 and the inductor 311 through the inductor 312. It can be understood by those skilled in the art that the receiving filter should not be limited to the above. Figure 3 In the structure shown, the specific number and specific layout of the fifth resonator, the sixth resonator and the second ground inductor in the receiving filter can be determined according to actual design requirements. Considering that the duplexer has many applicable scenarios, the number and layout of the fifth resonator, the sixth resonator and the second ground inductor included therein are also many possibilities. Therefore, for the sake of simplicity, all possible structures of the transmitting filter under the second layout are not listed one by one here.

[0041] In addition, it should be noted that in this embodiment, the third resonator, the fourth resonator, the fifth resonator and the sixth resonator are all implemented by thin film bulk acoustic wave resonators. In other embodiments, the third resonator, the fourth resonator, the fifth resonator and the sixth resonator can also be implemented by other conventional resonators such as surface acoustic wave resonators.

[0042] The receiving filter in the duplexer provided by the present invention can be regarded as consisting of two parts. For the first layout mode, the receiving filter includes a T-shaped network structure composed of a third resonator, a fourth resonator and a first inductor, and a trapezoidal network structure composed of a fifth resonator and a sixth resonator. For the second layout mode, the receiving filter includes a π-shaped network structure composed of a third resonator, a fourth resonator and a first inductor, and a trapezoidal network structure composed of a fifth resonator and a sixth resonator. In other words, compared with the duplexer in the prior art in which the receiving filter only adopts a trapezoidal network structure, the receiving filter in the duplexer provided by the present invention includes not only a trapezoidal network structure but also a T-shaped network structure / π-shaped network structure. On the one hand, the T-shaped network structure and the π-shaped network structure are arranged between the antenna terminal and the trapezoidal network structure, which is the same as the arrangement position of the matching network in the prior art; on the other hand, considering the characteristic that the resonator is capacitive outside the resonant frequency, the resonator that is capacitive at the transmission frequency of the duplexer is appropriately selected, so that the phase shift of the T-shaped network structure and the π-shaped network structure composed of the third resonator, the fourth resonator and the first inductor in the duplexer transmission frequency band is around 90°, which is close to the phase shift of the matching network in the prior art. Therefore, the T-shaped network structure and the π-shaped network structure can play the same role as the matching network in the prior art, so that the input impedance of the receiving filter seen from the antenna terminal is higher in the transmission frequency band. In other words, the input impedance of the receiving filter seen from the antenna terminal of the duplexer provided by the present invention is higher in the transmission frequency band, so there is no need to perform impedance matching through a matching network as in the prior art, and the use of capacitors is avoided. In this way, it is not only conducive to chip integration but also conducive to the miniaturization of the duplexer.

[0043] Preferably, when the third resonator and the fourth resonator have the same static capacitance value, the resonant frequency of the third resonator is less than or equal to the resonant frequency of the fifth resonator in the trapezoidal network structure, and the resonant frequency of the fourth resonator is less than or equal to the resonant frequency of the fifth resonator in the trapezoidal network structure, not only can the phase shift of the T-shaped network structure and the π-shaped network structure in the duplexer transmission frequency band be ensured to be around 90°, but it is also beneficial to reduce the insertion loss of the T-shaped network structure and the π-shaped network structure in the duplexer receiving frequency band, thereby helping to reduce the insertion loss of the receiving filter in the receiving frequency band. For the third resonator and the fourth resonator having the same static capacitance value, this can be achieved by designing the third resonator and the fourth resonator to have the same effective working area. In the case where the resonant frequency of the third resonator and the fourth resonator is lower than the resonant frequency of the fifth resonator, this can be achieved by thickening the piezoelectric oscillation stack (including the upper electrode, the piezoelectric layer and the lower electrode) of the third resonator and the fourth resonator. Specifically, one or more layers of the upper electrode, the piezoelectric layer and the lower electrode in the third resonator and the fourth resonator can be thickened so that the thickness of the piezoelectric oscillation stack is greater than the thickness of the piezoelectric oscillation stack of the fifth resonator, thereby making the resonant frequency of the third resonator and the fourth resonator lower than the resonant frequency of the fifth resonator. In the case where the resonant frequency of the third resonator and the fourth resonator is equal to the resonant frequency of the fifth resonator in the ladder network structure, this can be achieved by making the third resonator, the fourth resonator and the fifth resonator have piezoelectric oscillation stacks with the same thickness.

[0044] It should be noted that, compared with the method of thickening the piezoelectric oscillation stack of the third resonator and the fourth resonator separately, the third resonator, the fourth resonator and the fifth resonator that form the same piezoelectric oscillation stack at the same time can save at least one mask plate, which is beneficial to reduce the process complexity of the duplexer. Therefore, in a preferred embodiment, the third resonator and the fourth resonator have the same effective working area, and the third resonator, the fourth resonator and the fifth resonator have the same piezoelectric oscillation stack (that is, the static capacitance value of the third resonator and the fourth resonator is the same, and the resonant frequency of the third resonator, the fourth resonator and the fifth resonator is the same). However, in this case, the third resonator and the fourth resonator are capacitive in the transmission frequency band of the duplexer, and are not completely capacitive in the receiving frequency band, but are inductive in part of the receiving frequency band, wherein the third resonator and the fourth resonator are inductive in part of the receiving frequency band, which will affect the insertion loss characteristics of the T-shaped network structure and the π-shaped network structure in the part of the receiving frequency band (specifically, causing the insertion loss to be larger), thereby affecting the insertion loss characteristics of the receiving filter in the part of the receiving frequency band. In order to solve the above problems, the receiving filter may further include a second inductor, one end of which is connected to the receiving terminal and the other end is grounded, so as to improve the insertion loss of the T-shaped network structure and the π-shaped network structure in some receiving frequency bands. Similarly, the transmitting filter may further include a third inductor, one end of which is connected to the transmitting terminal and the other end is connected to the ground, so as to improve the insertion loss of the transmitting filter. Figure 2 In the duplexer shown in FIG. 1 , when resonators 201, 202, 203, 204, and 205 are the same, the duplexer can be configured as follows: Figure 4 As shown, by connecting the second inductor 215 between the transmitting terminal 50 and the ground, the insertion loss of the T-shaped network structure and the π-shaped network structure in the receiving filter 20 can be improved. Figure 4 As shown, the insertion loss of the transmission filter 10 is improved by connecting the third inductor 113 between the receiving terminal 40 and the ground. For the case where the transmission filter includes the third inductor and the receiving filter includes the second inductor, since the input impedance of the receiving filter of the duplexer provided by the present invention as seen from the antenna terminal is relatively high in the transmission frequency band, the influence on the passband deterioration degree of the transmission filter is relatively small. In this case, the improvement effect of the second inductor on the insertion loss is greater than the improvement effect of the third inductor on the insertion loss, so the inductance value of the second inductor needs to be smaller than the inductance value of the third inductor.

[0045] Below, Figure 4 The performance of the duplexer provided by the present invention is described by taking the example of Figure 4The parameters of the components in the duplexer are as follows: In the transmission filter 10, the effective working area of ​​resonator 101, resonator 102, resonator 103, resonator 104, resonator 105, resonator 106, resonator 107, and resonator 108 are 11335 μm 2 、7130μm 2 、10802μm 2 、6517μm 2 、17657μm 2 、16788μm 2 、18033μm 2 and 12810μm 2 , the inductance values ​​of inductor 109, inductor 110, inductor 111, inductor 112 and inductor 113 are 0.46nH, 0.23nH, 0.35nH, 3.5nH and 8.84nH respectively. In the receiving filter 20, the effective working area of ​​resonator 201, resonator 202, resonator 203, resonator 204, resonator 205, resonator 206, resonator 207, resonator 208 and resonator 209 are 7052μm 2 、7052μm 2 、7028μm 2 、10419μm 2 、6887μm 2 、14201μm 2 、19214μm 2 、14590μm 2 and 7754 μm 2 The inductance values ​​of the inductor 210 , the inductor 211 , the inductor 212 , the inductor 213 , the inductor 214 , and the inductor 215 are 2.92 nH, 0.78 nH, 0.25 nH, 0.1 nH, 1.95 nH, and 4.76 nH, respectively.

[0046] Please refer to Figure 5 and Figure 6 , Figure 5 and Figure 6 They are Figure 4 The relationship between the input impedance (amplitude) and frequency of the transmit filter and the receive filter in the duplexer as seen from the antenna terminal is shown in FIG. Figure 5 As shown, Figure 4 The input impedance of the transmit filter in the duplexer shown as seen from the antenna terminal is typically high (greater than 100) in the receive frequency band, so the transmit filter will not have a significant loading effect on the receive filter, thereby not causing a degradation in the receive filter passband. Figure 6 As shown, Figure 4The input impedance of the receiving filter in the duplexer shown as seen from the antenna terminal is relatively high (greater than 100) in the transmitting frequency band, so the receiving filter will not have a large load effect on the transmitting filter, thereby not causing deterioration of the transmit filter passband. Therefore, there is no need for a matching network for impedance matching as in the prior art.

[0047] Please refer to Figure 7 and Figure 8 , Figure 7 and Figure 8 They are Figure 4 The relationship between the insertion loss of the transmit filter and the receive filter in the duplexer shown in Figure 2 is a graph of the relationship between the insertion loss and the frequency. Figure 7 and Figure 8 It can be seen that Figure 4 The insertion loss of the transmitting filter in the transmitting frequency band and the insertion loss of the receiving filter in the receiving frequency band of the duplexer shown meet the performance requirements of the duplexer.

[0048] Please refer to Fig. 9 and Fig.10 , Fig. 9 and Fig.10 They are Figure 4 The relationship between the out-of-band rejection and isolation of the duplexer and the frequency is shown. Fig. 9 and Fig.10 It can be seen that Figure 4 The out-of-band suppression characteristics and isolation characteristics of the duplexer shown meet the performance requirements of the duplexer.

[0049] To illustrate Figure 4 The role of the second inductor in the receiving filter of the duplexer shown in FIG. Fig.11 The performance of the duplexer shown is illustrated as a comparison, where Fig.11 The duplexer shown is Figure 4 The difference between the duplexers shown is that Fig.11 The receiving filter of the duplexer shown does not include a second inductor. In addition, it should be noted that Fig.11 and Figure 4 Elements with the same reference numerals have the same parameters and are not described again for the sake of brevity.

[0050] Please refer to Fig.12 , Fig.12 yes Fig.11 The relationship between the impedance phase and frequency of the third resonator in the receiving filter of the duplexer shown in the figure. It should be noted here that since the third resonator and the fourth resonator are the same, the relationship between the impedance phase and frequency of the fourth resonator can be referred to Fig.12 .from Fig.12It can be seen that the third resonator and the fourth resonator are capacitive in the duplexer transmission frequency band, and are capacitive and inductive in the reception frequency band, specifically, they are capacitive in the first half of the reception frequency band and inductive in the second half of the reception frequency band.

[0051] Please refer to Fig.13 and Fig.14 , Fig.13 yes Fig.11 The relationship between the phase shift and frequency of the T-shaped network structure in the receiving filter of the duplexer shown in the figure, Fig.14 yes Fig.11 The relationship between insertion loss and frequency in the T-shaped network structure of the receiving filter in the duplexer shown in the figure. Fig.13 It can be seen that Fig.11 The phase shift value of the T-shaped network structure in the receiving filter of the duplexer shown in the figure is about 90° in the transmitting frequency band, which can meet the phase shift requirement. Fig.14 It can be seen that Fig.11 The insertion loss of the T-shaped network structure in the receiving filter of the duplexer shown in the figure deteriorates in the second half of the receiving frequency band. The deterioration of the insertion loss of the T-shaped network structure in the receiving filter in the second half of the receiving frequency band will correspondingly lead to the deterioration of the insertion loss of the receiving filter in the corresponding frequency band. This can be seen from Fig.15 It can be seen in.

[0052] Please refer to Fig.15 , Fig.15 yes Fig.11 The relationship between the insertion loss of the receive filter and the frequency in the duplexer shown. Fig.15 It can be seen that Fig.11 The insertion loss of the receive filter in the duplexer shown deteriorates in the second half of the receive frequency band.

[0053] Will Fig.15 and Figure 8 By comparison, compared with Fig.11 For the duplexer shown in the figure, Figure 4 The duplexer shown in the figure shifts the parallel resonant frequency point in the receiving filter to the right by connecting a second inductor between the transmitting terminal and the ground, thereby improving the insertion loss of the receiving filter in the second half of the receiving frequency band to meet the performance requirements of the duplexer.

[0054] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other components, units or steps, and the singular does not exclude the plural. Multiple components, units or devices stated in the system claim may also be implemented by one component, unit or device through software or hardware.

[0055] The receiving filter in the duplexer provided by the present invention is composed of a resonator and an inductor, and the input impedance of the receiving filter viewed from the antenna terminal is higher in the transmission frequency band by utilizing the capacitive characteristic of the resonator at the non-resonant frequency. In this way, there is no need to set up a matching network as in the prior art, thereby avoiding the use of capacitors, which is not only beneficial to chip integration but also conducive to the miniaturization of the duplexer.

[0056] The above disclosures are only some preferred embodiments of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A duplexer, comprising: Transmit filter, receive filter, antenna terminal, transmit terminal and receive terminal; The transmission filter comprises at least one first resonator and at least one second resonator, wherein the at least one first resonator is connected in series between the antenna terminal and the transmission terminal, and the at least one second resonator is connected in parallel between the antenna terminal and the transmission terminal; The receive filter includes a third resonator, a fourth resonator, a first inductor, at least one fifth resonator and at least one sixth resonator, wherein the third resonator, the fourth resonator and the at least one fifth resonator are sequentially connected in series between the antenna terminal and the receive terminal, one end of the first inductor is connected between the third resonator and the fourth resonator, and the other end is grounded, and one end of the sixth resonator is connected between the fourth resonator and the receive terminal, and the other end is grounded; or the first inductor and the at least one fifth resonator are sequentially connected in series between the antenna terminal and the receive terminal, one end of the third resonator is connected between the antenna terminal and the first inductor, and the other end is grounded, one end of the fourth resonator is connected between the first inductor and the fifth resonator, and the other end is grounded, and one end of the sixth resonator is connected between the fifth resonator and the receive terminal, and the other end is grounded.

2. The duplexer according to claim 1, wherein: The third resonator and the fourth resonator have the same static capacitance value; The resonant frequency of the third resonator is less than or equal to the resonant frequency of the fifth resonator; The resonant frequency of the fourth resonator is less than or equal to the resonant frequency of the fifth resonator.

3. The duplexer according to claim 2, characterized in that: When the resonance frequencies of the third resonator, the fourth resonator, and the fifth resonator are the same, the reception filter further includes a second inductor having one end connected to the reception terminal and the other end connected to the ground.

4. The duplexer according to claim 3, characterized in that: The transmission filter further includes a third inductor having one end connected to the transmission terminal and the other end connected to the ground.

5. The duplexer according to claim 4, characterized in that: The inductance value of the second inductor is smaller than the inductance value of the third inductor.

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