RF Multiplexer

Abstract

A radio frequency multiplexer (210, 220, 230) includes a transmitting circuit and a receiving circuit, each of which includes an RF filter circuit (211, 212, 221, 227, 231, ..., 234). The transmitting circuit and the receiving circuit are coupled to an antenna port (225, 245) and a corresponding transmitting port (221) and a receiving port (222). A portion of the transmitting circuit and a portion of the receiving circuit are arranged on a single die (213, 226, 250). The layer stack of resonators of the transmitting circuit and the receiving circuit arranged on the single die can be optimized for the required functionality.

Description

[0001] This application is a divisional application of the invention patent application with international application number PCT / EP2019 / 061436, entry into the Chinese national phase date of November 12, 2020, Chinese national application number 201980031922.X, and invention name “RF Multiplexer”. Technical Field

[0002] The present disclosure relates to a radio frequency multiplexer. In particular, the present disclosure relates to a radio frequency (RF) multiplexer circuit including a transmitting circuit and a receiving circuit, each of which includes an RF filter. Background Art

[0003] Radio frequency (RF) multiplexers are used in electronic communication systems located in front of the antenna to couple the transmit and receive paths to the antenna. The transmit and receive paths include RF filters that are used to select the desired bandwidth from the antenna signal or provide the RF signal to the antenna. Resonators are used to set the filters. A duplexer connects one transmit path and one receive path to the antenna port, while a higher-order multiplexer (such as a quadplexer) couples multiple transmit and receive paths to the antenna port.

[0004] In a conventional RF multiplexer, the resonators that form the RF transmit (Tx) and receive (Rx) filters are implemented on separate chips. Typically, one chip includes all the resonators for the Tx filter, and another chip includes all the resonators for the Rx filter. Although different resonators in the filter implement different electrical sub-functions, these resonators are manufactured with the same manufacturing process, making it difficult to optimize these resonators for specific functions. For example, the resonators close to the input port of the Tx filter may have restrictions on skirt steepness and parasitic modes in the frequency band of other carrier aggregation bands, while the resonators close to the antenna port must provide high reflection in the counter band frequency range. Typically, these requirements limit the design flexibility of the resonators when all the resonators of one filter path of a multiplexer are implemented on one chip.

[0005] It would be desirable to have greater flexibility in the design of multiplexer circuits and to improve the performance of filters in RF multiplexers.

[0006] An object of the present disclosure is to provide a radio frequency multiplexer circuit showing improved performance.

[0007] Another object of the present disclosure is to provide an RF multiplexer circuit having improved power ruggedness and improved reflection within the stop-band frequency range. Summary of the invention

[0008] According to the present disclosure, one or more of the above-mentioned purposes are achieved by a radio frequency multiplexer, which includes: a transmitting circuit and a receiving circuit, wherein the transmitting circuit and the receiving circuit each include an RF filter circuit; a first port, which is coupled to an antenna, and the transmitting circuit and the receiving circuit are coupled to the first port; a second port, which is coupled to the transmitting circuit; and a third port, which is coupled to the receiving circuit; a portion of the transmitting circuit and a portion of the receiving circuit are arranged on a single single crystal substrate.

[0009] According to the present disclosure, a portion of the transmit circuit and a portion of the receive circuit are disposed on a single die. Thus, portions of two different filter paths of the multiplexer share the same single die. This is different from conventional solutions in which one die is limited to one filter path, a transmit (Tx) path or a receive (Rx) path. A single die may be a single crystal substrate on which portions of the transmit circuit and the receive circuit are implemented. Within one die, the layer stacks of resonators implementing the transmit circuit and the receive circuit are identical because the resonators on one die are manufactured simultaneously using the same process steps (such as deposition, structuring, etc.). Sharing the same single die for the transmit circuit and the receive circuit allows resonators having corresponding functionality in different filters to be manufactured together. The layer stack of the resonator can be optimized for the desired functionality.

[0010] With this approach, an improvement in the performance of the overall multiplexer functionality can be expected. For example, on the one hand, filter skirts with strong requirements for steepness and low temperature coefficients can be implemented on different dies, and on the other hand, resonators directly located at the antenna nodes that require high reflection in the stopband frequency range can be implemented on different dies. The layer stacks on different dies can be optimized for different functionalities. For example, the thickness of a metal layer or a dielectric layer within a layer stack can be optimized for high skirt steepness and low temperature coefficient or, alternatively, for high stopband reflection. The technician has experience from conventional designs on how to optimize the layer stack for the required functionality.

[0011] The transmitting circuit and receiving circuit in the multiplexer each include multiple resonators, such as surface acoustic wave (SAW) resonators or bulk acoustic wave (BAW) resonators. According to the principles of the present disclosure, at least one resonator of the transmitting circuit and at least one resonator of the receiving circuit are arranged on the same single bare chip. If the filter path is implemented using SAW resonators, the single bare chip is a single crystal piezoelectric substrate on which the SAW resonator is formed. All resonators on the same single bare chip share a common single crystal substrate. The single crystal piezoelectric substrate can be lithium niobate or lithium tantalate or any other piezoelectric substrate that is beneficial to forming a SAW resonator. If the filter is implemented using BAW resonators, the single crystal substrate can be a single crystal silicon on which a layer stack of BAW resonators is formed.

[0012] The resonator coupled to the antenna port of the Tx filter and the antenna port of the Rx filter can be implemented on the same single die. This allows the layer stack to be optimized to achieve high reflection in the stop band, which is outside the pass band of the corresponding filter. This is particularly beneficial in the carrier aggregation filter system of the 4G (LTE) communication standard.

[0013] The transmit filter and the receive filter may include a series path of a resonator, which includes one or more resonators connected in series. The series-connected resonators of the Tx filter and the series-connected resonators of the Rx filter are implemented on the same bare chip, and these series-connected resonators are coupled to the antenna port. The Tx filter may also include one or more parallel paths connected to the series path, which may also be arranged on a single bare chip together with the series resonator near the antenna port. Therefore, the parallel-connected Tx resonator exhibits the same layer stack as the resonator located at the antenna port. The layer stack can be optimized for high reflection within the stopband frequency range. Additional series-connected resonators of the Tx filter (such as resonators near the input port of the Tx filter in the series path of the Tx filter) can be implemented on a separate bare chip so that they can be optimized for steep filter skirts and high power durability. Steep filter skirts and high power durability generally require low temperature coefficients so that the heat generated by the power consumption of the Tx filter does not shift the resonant frequency. However, high reflection in the stopband is usually in conflict with low temperature coefficient and high power endurance, so the stopband reflection can be optimized using a layer stack of the resonator coupled to the antenna. Therefore, a series resonator connected to the Tx input port is implemented on a die separate from the resonator connected to the antenna port, wherein the resonator connected to the antenna port shares the resonator from the Tx filter and the Rx filter. The layer stack of the two dies is optimized for different functionalities, which are power endurance, high skirt steepness and low temperature coefficient on the one hand, and high reflection in the stopband on the other hand. Specifically, the temperature coefficient of the resonator connected to the antenna port sharing the same die is higher than the temperature coefficient of the resonator connected to the Tx input port sharing another die.

[0014] The principles of the present disclosure can be employed with a duplexer circuit or a more complex multiplexer circuit (such as a quadplexer or even a higher order multiplexer). For example, a quadplexer may include two Tx ports and two Rx ports that combine transmit and receive signals at one antenna port. Resonators coupled to antenna ports of at least one Tx filter and at least one Rx filter or two Tx filters and two Rx filters can be implemented on a single die. A series resonator of two Tx ports can be implemented on another die. The layer stacking of resonators of two separate die can be optimized for different functionalities. The first die may also include a parallel-connected resonator of the Tx filter. Other elements from the Rx filter may also be implemented on the first die. Specifically, a series resonator of a corresponding Tx port close to different Tx paths is implemented on the same single die. In addition, other resonators of the Tx path and the Rx path are implemented on another single die. Advantageously, the layer stacking of resonators of different Tx paths or Rx paths can be optimized for the same functionality. The number of components and the size of the circuit are substantially the same as in conventional solutions, where different Tx filters or Rx filters are implemented on different dies.

[0015] According to an embodiment, the layer stack of the SAW resonator is covered by a dielectric layer (such as silicon dioxide). The thickness of the dielectric layer can be weighed between power durability and low temperature coefficient and high reflection in the stop band. The larger thickness of the dielectric layer causes high power durability and low temperature coefficient. However, a relatively thick dielectric layer can also be acoustically excited so that the reflection will be lower. Resonators on the die that are optimized for high power durability and low temperature coefficient (such as resonators close to the Tx input port) can include thick dielectric layers, such as thick silicon dioxide layers. The silicon dioxide layer can have a thickness in the range of about 800 nanometers (nm). On the other hand, the dielectric layer of the resonator coupled to the antenna port can be optimized for lower reflection in the stop band and sacrifice power durability and low temperature coefficient. In this case, the dielectric layer is substantially thinner and can have a thickness in the range of about 400 nanometers (nm). The thickness of the dielectric layer of the resonator that exhibits high power durability and low temperature coefficient can be twice that of the dielectric layer of the resonator that exhibits low reflection in the stop band frequency.

[0016] The principles of the present disclosure can also be applied to BAW resonators arranged on the same die, wherein a piezoelectric substrate (such as aluminum nitride) is sandwiched between two metal electrodes. A reflective component (such as a Bragg mirror) can be arranged between a common substrate and a bottom electrode. All resonators from the same single die have the same layer stack, wherein each layer has the same thickness on different BAW resonators arranged on the same die. In this case, the single crystal substrate can be single crystal silicon.

[0017] It should be understood that both the above general description and the following detailed description are exemplary only and are intended to provide an overview or framework to understand the nature and characteristics of the claims. The accompanying drawings are included to provide a further understanding of this specification and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate one or more embodiments and, together with the description, are used to explain the principles and operation of the various embodiments. The same elements in different figures of the accompanying drawings are represented by the same reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the attached picture:

[0019] Figure 1 Conventional implementations of duplexers and quadplexers are shown;

[0020] Figure 2 Two possible implementations of a duplexer according to the principles of the present disclosure and an implementation of a quadplexer according to the principles of the present disclosure are shown;

[0021] Figure 3 shows a detailed schematic diagram of a duplexer according to the principles of the present disclosure;

[0022] Figure 4 Shows Figure 1 The sum of the conventional duplexer Figure 3 Admittance graph and reflection coefficient graph of a duplexer according to the principles of the present disclosure;

[0023] Figure 5 shows a detailed schematic diagram of a quadplexer according to the principles of the present disclosure; and

[0024] Figure 6 A cross-sectional view of a portion of a die showing several resonators and an enhanced cross-section of a portion of a SAW resonator are shown. DETAILED DESCRIPTION

[0025] The present disclosure will now be described more fully below with reference to the accompanying drawings showing embodiments of the present disclosure. However, the present disclosure may be embodied in many different forms, and the present disclosure should not be construed as being limited to the embodiments set forth herein. Instead, these embodiments are provided so that the present disclosure will fully convey the scope of the present disclosure to those skilled in the art. The accompanying drawings are not necessarily drawn to scale, but are configured to clearly illustrate the present disclosure.

[0026] Figure 1 The implementation of conventional duplexer and conventional quadplexer is shown. Duplexer 110 includes port 125 to be connected to antenna. Signal (Tx) to be transmitted is provided to input port 121, and port 122 provides filtered received signal (Rx). Filters 111, 112 are arranged between antenna terminal 125 and Tx terminal 121, Rx terminal 122. According to conventional principles, filter 111 is implemented using several resonators (for example, surface acoustic wave (SAW) resonators that are all implemented and arranged on one chip). The resonators of Tx filter 111 share the same single crystal piezoelectric substrate on which a resonator layer is arranged. In a similar manner, Rx filter 112 includes several SAW resonators that are all arranged on the same bare die. Tx filter 111 and Rx filter 112 are arranged on two separate bare dies or chips.

[0027] The quadplexer 130 includes an antenna port 145 and two Tx transmit ports 141, 142 and two Rx receive ports 143, 144. The corresponding filters associated with the Tx / Rx ports 141, ..., 144 are implemented on separate individual chips, respectively. The resonators from one Rx or Tx filter are not implemented on the chip of the other Tx or Rx filter, respectively.

[0028] Figure 2 Two possible implementations of an RF duplexer according to an embodiment of the present disclosure and an implementation of an RF quadplexer according to an embodiment of the present disclosure are shown. The duplexer 210 includes an antenna port 225, a Tx port 221, and an Rx port 222. The Rx filter 212 includes several resonators that are all arranged on one chip. The Tx filter 211 includes several resonators, wherein a first portion 213 of the resonator is disposed on the same chip as the Rx filter 212. Another portion 214 of the resonator of the Tx filter 211 is disposed on a separate second chip. The chips 213, 214 are mounted on a laminate, which may include a polymer substrate that includes one or more layers of metal wiring to provide conductivity.

[0029] Duplexer 220 shows another division of resonators within the Tx filter and the Rx filter. A first portion of the resonators of Tx filter 211 and a first portion of the resonators of Rx filter 212 are implemented on a first chip 226. The corresponding resonators are coupled to the antenna port so that their layer stack can be optimized for electrical requirements that are beneficial to the resonators for antenna coupling. A second portion of the resonators is implemented on a second chip 227 so that the layer stack can be optimized to meet other electrical requirements. For example, the layer stack of the resonators on chip 227 can be optimized to meet the requirements for the Tx portion of the duplexer.

[0030] The quadplexer 230 shows another division of resonators within the filters of the quadplexer. The quadplexer 230 includes four filters for four bands, which are Tx filters 232, 233 and Rx filters 231, 234. The resonators of all four filters coupled to the antenna port 245 are implemented on a single chip 250. The chip 250 includes resonators of four different bands and four different filters coupled to the antenna port 245. A second chip 253 includes the remaining resonators of the Rx filter 231 and a portion of the resonators of the Tx filter 232. Another chip 252 includes the remaining resonators of the Rx filter 234 and a portion of the resonators of the Tx filter 233. Yet another chip 251 includes a portion of the resonators of the Tx filters 232, 233.

[0031] The allocation of resonators to corresponding chips depends on functionality. Resonators that perform similar functions in different filters can be allocated on the same chip so that the same layer stack can be used to manufacture these resonators. In fact, for resonators implemented on the same chip, the order of the layers and the thickness of the layers are the same. Therefore, the corresponding layer stack can be optimized for the required function. With respect to duplexer 210, the resonator of chip 214 can be manufactured using the following layer stack, which is suitable for processing the high transmission power of the Tx filter input to the terminal 221. The chip 227 of duplexer 220 can be manufactured using the following layer stack, which is optimized to process the internal skirts of the Tx filter and the Rx filter with a low temperature coefficient and the external part with a large pole distance and zero position. The chip 250 of quadplexer 230 can be manufactured using the following layer stack, which exhibits good reflection in the stopband range, which is beneficial for the resonator coupled to the antenna node. Chip 251 may include a layer stack that provides an internal skirt of a directly adjacent filter with a small temperature coefficient and a small distance between pole and zero locations. Chip 252 includes a layer stack that is beneficial for implementing resonators that implement the desired bandwidth. The layer stack of chip 252 is beneficial for resonators with less critical functions, so that these resonators can be manufactured using a moderate layer stack that has good general electrical characteristics to provide the desired bandwidth. In general, the assignment of resonators to corresponding chips takes into account the electrical function implemented by the resonator rather than the assignment to a specific filter passband according to conventional solutions.

[0032] Now go to Figure 3 and Figure 4 , according to the admittance and reflection coefficient curves obtained through circuit simulation ( Figure 4 ) combined with electrical behavior to depict Figure 2 Detailed schematic diagram of the implementation of the duplexer 210 ( Figure 3 ).against Figure 1 The conventional duplexer 110 and Figure 2 The duplexer 210 according to the present disclosure depicts a corresponding curve.

[0033] The first chip 214 includes series-connected resonators 311, 312, 313 coupled to the Tx port 221. Resonator 311 is directly coupled to the Tx port 221, and resonators 312, 313 are coupled downstream of resonator 311. The second chip 213 includes series-connected resonators (such as resonators 320, 321, 322, 323) of the Rx path and parallel-connected resonators (such as resonators 324, 325) of the Rx path. The chip 213 also includes a resonator 314 of the Tx path, which is coupled to the antenna port 225 and downstream of the series resonator 313. The chip 213 also includes resonators 315, 316, 317, which are parallel-connected resonators of the Tx filter 211. For example, resonator 317 is connected between the node between resonators 313 and 314 and the ground potential. In a similar manner, the resonators 315 , 316 are connected between nodes in the series path of the Tx filter 211 and ground potential.

[0034] The series-connected resonators 311, 312, 313 coupled to the Tx input port 221 or downstream thereof receive considerable input power, and therefore, they must be configured to be power durable. The resonators 311, 312, 313 also form the right skirt 411 of the passband 410 of the filter. The right skirt must be as steep as possible to allow good transmission within the required signal band 212 and to achieve high attenuation at the adjacent unwanted signal band 413. In order to achieve high power durability, it is beneficial to implement resonators with low temperature coefficients so that heating of the resonator by transmitting RF signals does not significantly shift the right skirt of the passband. In order to achieve a defined right skirt of the passband, it is beneficial to implement resonators that have a relatively small distance between the pole and zero positions of the admittance characteristics of the resonator.

[0035] The layer stacking realizing resonators 311, 312, 313 is configured to realize the above-mentioned characteristics. First, this requires a relatively thick dielectric layer, which covers the metal electrode of the interdigital transducer (IDT) of the SAW resonator. The thick dielectric layer can be a silicon dioxide layer with a thickness in the range of about 800nm ​​covering the IDT. By realizing resonators 311, 312, 313 on a single chip 214, the layer stacking including relatively thick silicon dioxide layers of these resonators can be optimized for these resonators. The layer stacking characteristics are limited to these resonators because the thick silicon dioxide layer will not be beneficial to other resonators responsible for other functions of the filter in the duplexer. In this regard, the parallel-connected resonators 315, 316, 317 of the Tx filter 211 receive less power compared to the resonators 311, 312, 313 connected in series. Furthermore, the parallel resonators are not responsible for the steep skirts, and therefore, it is not necessary for the resonators 315, 316, 317 to have a low temperature coefficient. Instead, the resonators 315, 316, 317 are responsible for providing sufficient bandwidth for the passband of the filter. It is beneficial not to include the parallel-connected resonators 315, 316, 317 on the chip 214, because these parallel-connected resonators must meet different requirements compared to the series-connected resonators 311, 312, 313.

[0036] Resonators 315, 316, 317 connected in parallel and resonator 314 connected in series directly coupled to antenna node 225 are implemented on a second chip 213 different from chip 214. In addition, the Rx filters of resonators 320, ..., 325 are also arranged on the second chip 213. This means that the resonators from two filters (Tx filter 211 and Rx filter 212) are arranged on a single bare die or chip 213. The layer stack of resonators 314, ..., 325 meets different requirements from the layer stack of resonators 311, ..., 313, so that the layer stack of the second chip 213 is optimized to have a low plate mode and high reflection in the stopband frequency outside the passband of the filter. In order to achieve this effect, the dielectric layer covering the IDT of resonators 314, ..., 325 is much thinner than the dielectric cover layer of the resonator of chip 214. For example, the silicon dioxide layer on the resonator of chip 213 has a thickness of about 400 nm, which is half the thickness of the dielectric layer covering the IDT of chip 214. The thin dielectric layer reduces the plate mode of the resonator because the coupling of acoustic energy into the dielectric layer is avoided. In addition, the reflection in the stopband frequency is improved.

[0037] Now go to Figure 4 , you can Figure 4The influence on the plate mode is obtained in the region 420 of the attenuation curve shown in the upper part of the graph. In the region 420, the attenuation curve has a local maximum. Curve 421 represents Figure 1 422 depicts the attenuation of the conventional duplexer 110, and curve 422 depicts the attenuation of the duplexer 210 according to the principles of the present disclosure. Figure 4 As a result, the attenuation of the curve 422 in the region 420 is lower than that of the conventional curve 421. This is mainly achieved by implementing the resonator 314 coupled to the antenna port 225 on the second chip 213, which is optimized to have a low thickness of the dielectric silicon dioxide layer covering the IDT. Therefore, the plate mode in the frequency region 420 is reduced.

[0038] Regarding the same frequency region 420 Figure 4 From the reflection coefficient shown in the lower part of FIG. 4 , it should be noted that the conventional duplexer 110 exhibits a curve 431 showing a local minimum in the frequency region 420. In contrast, the reflection curve 432 of the duplexer 210 according to the present disclosure exhibits a relatively high level. Likewise, enhanced reflection is achieved by arranging the resonator 314 on the chip 213 having a silicon dioxide layer with a small thickness in the range of about 400 nm to improve the reflection behavior in the stopband frequency range.

[0039] Now go to Figure 5, depicts a schematic diagram of a quadplexer according to the principles of the present disclosure. The quadplexer includes an antenna port 545, two Rx ports 521, 522, and two Tx ports 523, 524. The resonators in the quadplexer implement four filters, such as Rx filters 531, 532 and Tx filters 533, 534. The resonators are implemented on three chips 550, 551, 552. Chips 550 and 551 include resonators from several filters. Chip 550 includes resonators from all Rx filters and Tx filters. Specifically, at least the following resonators are provided on chip 550, which are coupled to antenna port 545. Chip 551 includes resonators from two Tx filters 533, 534. Specifically, chip 551 includes resonators connected in series and coupled to Tx input ports 523, 524 of Tx filters 533, 534. Chip 552 includes the remaining resonators of Rx filter 532. Chip 550 also includes parallel-connected resonators of Tx filters 533, 534 and parallel-connected resonators of Rx filter 531. The series resonators of Tx filters 533, 534 form a steep right filter skirt and must be able to handle sufficient power so that these series resonators are implemented together on a common chip 551 optimized for high power handling and low temperature coefficient. The resonators coupled to the antennas of all four filters are implemented on chip 550 optimized for low-plane modes and relatively high reflections in the stopband. The resonators of chip 552 have relaxed requirements, so they can be dedicated to a separate chip. The size of the entire circuit of the quadplexer is no larger than that of a conventional design. On the other hand, as previously combined Figure 4 As explained by the admittance and reflection curves of FIG, allocating the functions of the resonators of different filters to a common chip enables the layer stack of the resonators to be optimized for the specific functions of the corresponding resonators, thereby improving the overall filter performance including power handling capability and temperature stability.

[0040] Now go to Figure 6 , depicts a cross section through a chip comprising three resonators. Specifically, Figure 6 Shown along line 600 through Figure 3 A cross section of chip 214 is shown. Figure 6 A cross-sectional view of the resonators 311, 312, 313 and the substrate or chip 214 is depicted in FIG. Figure 6, a portion 610 of the rightmost resonator 313 is shown in an enlarged representation. The substrate 214 can be a single crystal piezoelectric substrate, such as lithium niobate or lithium tantalate. A portion of an interdigital transducer (IDT) 620 is disposed on the substrate 214. The electrode structure of the IDT includes a lowermost layer 621, which can be a titanium seed layer, to enable adhesion of a metal electrode 622 disposed thereon. The metal electrode 622 includes components of copper and aluminum. The IDT is covered by a silicon dioxide layer 623. A trade-off between the power durability and low temperature coefficient of the resonator and high stopband reflection and low plate mode can be achieved by selecting an appropriate thickness of the silicon dioxide layer 622. A higher thickness of the layer 622 allows a low temperature coefficient and high power durability, while a thinner layer 622 provides a low plate mode and high reflection in the stopband frequency. Therefore, the resonator coupled to the Tx input terminal is disposed on a chip with a thick silicon dioxide layer (e.g., about 800nm). A silicon nitride thin layer having a thickness of about 100 nm (in Figure 6 A passivation layer (not shown) covering the silicon dioxide layer may be beneficial. The resonator coupled to the antenna port is arranged on a chip manufactured using a relatively thin silicon dioxide layer (eg, approximately 400 nm).

[0041] The present disclosure is also useful for implementing filters with bulk acoustic wave (BAW) resonators. A BAW resonator is disposed on a single crystal substrate (such as a single crystal silicon substrate). The resonator includes a piezoelectric substrate (such as aluminum nitride) sandwiched between an upper electrode and a lower electrode. A reflective element (such as a Bragg mirror) may be disposed between the lower electrode and the single crystal substrate. The teachings described above in conjunction with the SAW resonator are accordingly applicable to the BAW resonator. Specifically, a BAW resonator disposed on a single chip or substrate exhibits the same layer stack and the same thickness of each layer in the layer stack, including a dielectric layer (such as silicon dioxide) disposed thereon. According to the present disclosure, the layer stack is optimized for different purposes (such as high power durability and low temperature coefficient or high stopband reflection and low plate mode).

[0042] It is obvious to those skilled in the art that various modifications and changes may be made without departing from the spirit or scope of the present disclosure as defined in the appended claims. Since those skilled in the art may conceive of modifications, combinations, sub-combinations and variations of the disclosed embodiments in combination with the spirit and substance of the present disclosure, the present disclosure should be interpreted as including all contents within the scope of the appended claims.

Claims

1. A radio frequency multiplexer, comprising: A transmitting circuit (211, 534) and a receiving circuit (212, 531), each of the transmitting circuit and the receiving circuit comprising an RF filter circuit; A first port (225, 545) to be coupled to an antenna, the transmitting circuit and the receiving circuit being coupled to the first port; A second port (221, 524) coupled to the transmitting circuit; a third port (222, 521) coupled to the receiving circuit; wherein the transmitting circuit (211) includes a first resonator (314) coupled to the first port (225), and the receiving circuit (212) includes a second resonator (323) coupled to the first port (225), wherein the first resonator and the second resonator are disposed on a first die; The transmitting circuit (211) comprises an additional resonator (311, 312, 313), wherein the additional resonator is arranged on a second die different from the first die, The first resonator (314) of the transmission circuit coupled to the first port and the additional resonators (311, 312, 313) are included in a series path of the transmission circuit, The transmit circuit comprises a plurality of parallel paths (315, 316, 317) connected to the series path, wherein one or more further resonators are included in the plurality of parallel paths of the transmit circuit and are arranged on the first die, The additional resonators (311, 312, 313) are connected in series, and the multiple parallel paths are respectively connected between multiple different nodes in the series paths and the ground potential, wherein some of the multiple different nodes are located between adjacent resonators in the additional resonators (311, 312, 313).

2. The radio frequency multiplexer according to claim 1, wherein the filter circuit of the transmitting circuit (211) exhibits a passband (412), and wherein the first resonator (314) of the transmitting circuit disposed on the first die is configured so that the filter circuit of the transmitting circuit exhibits high reflection in a stopband (420) outside the passband (412).

3. The radio frequency multiplexer according to claim 1, further comprising: Another transmission circuit (533) and a fourth port (523) connected to the other transmission circuit, the transmission circuit (534) and the other transmission circuit (533) each include the plurality of parallel paths including the series path and connected to the series path. 4 . The radio frequency multiplexer according to claim 1 , wherein a first dielectric layer of the first die is thinner than a second dielectric layer of the second die.

5. The radio frequency multiplexer according to any one of claims 1 to 3, wherein the first resonator is a surface acoustic wave resonator.

6. The radio frequency multiplexer of claim 4, wherein the first dielectric layer is a silicon dioxide layer (623).

7. A radio frequency multiplexer according to any one of claims 1 to 3, wherein the first resonator, the second resonator and the additional resonator are surface acoustic wave resonators comprising a metal electrode (620) covered by a dielectric layer (623), wherein the thickness of the dielectric layer of the resonator arranged on the first die is substantially different from the thickness of the dielectric layer of the resonator arranged on the second die.

8. The radio frequency multiplexer according to any one of claims 1 to 3, wherein the first resonator and the second resonator are bulk acoustic wave resonators.

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