REDUCTION OF ON-DIE PARASITIC CAPACITANCE FOR 5G FILTER DESIGN WITH HIGH ISOLATION

An acoustic wave filter assembly having reduced on-die capacitance and improved isolation for high-frequency applications. The acoustic wave filter assembly includes a filter port, an antenna port, an acoustic wave filter connected between the filter port and the antenna port, one or more ground pins connected between the filter port and the antenna port, and a metallic guard ring extending around the acoustic wave filter assembly. At least one of the one or more ground pins is connected to the metallic guard ring. A diplexer, multiplexer, radio-frequency module and wireless device are also provided.

BACKGROUND

Field

Embodiments of the present disclosure relate to acoustic wave filter design for 5G applications, and in particular to bulk acoustic wave filter assemblies.

Description of the Related Technology

Acoustic wave filter assemblies can filter radio-frequency signals. An acoustic wave filter assembly can include one or more acoustic wave filters. The acoustic wave filters can include a plurality of resonators arranged to filter a radio-frequency signal. The resonators can be arranged as a ladder circuit. Example acoustic wave filters include bulk acoustic wave (BAW) filters. Acoustic wave filter assemblies can be implemented in radio-frequency electronic systems.

SUMMARY

According to one embodiment there is provided a filter assembly. The filter assembly comprises a metallic guard ring extending around the filter assembly, an antenna port, a filter port, and an acoustic wave filter connected between the antenna port and the filter port. The acoustic wave filter includes one or more bulk acoustic wave resonators, and one or more ground pins connected between the filter port and the antenna port. At least one of the one or more ground pins are further connected to the metallic guard ring.

In one example, the acoustic wave filter is configured to filter a transmit signal received at the filter port to a cellular frequency pass band and output the filtered transmit signal at the antenna port.

In one example, the acoustic wave filter is configured to filter a receive signal received at the antenna port to a cellular frequency pass band and output the filtered receive signal at the filter port.

In one example, the acoustic wave filter is a band-pass filter.

In one example, the acoustic wave filter has a pass band between approximately 4.4 GHz and 5 GHz.

In one example, the acoustic wave filter has a pass band between approximately 3.3 GHz and 4.2 GHz.

According to another embodiment there is provided a diplexer. The diplexer comprises a first acoustic wave filter connected between an antenna port and a first filter port, the first acoustic wave filter including one or more bulk acoustic wave resonators, a second acoustic wave filter connected between the antenna port and a second filter port, the second acoustic wave filter including one or more bulk acoustic wave resonators, a metallic guard ring extending around the first and second acoustic wave filters, and one or more ground pins connected between the antenna port and the first and second filter ports. At least one of the one or more ground pins is further connected to the metallic guard ring.

In one example, the diplexer is arranged on a single semiconductor chip.

In one example, the first acoustic wave filter is configured to filter a transmit signal received at the first filter port to a first frequency pass band and output the filtered transmit signal to the antenna port.

In one example, the first acoustic wave filter is configured to filter a receive signal received at the antenna port to a first frequency pass band and output the filtered receive signal to the first filter port.

In one example, the second acoustic wave filter is configured to filter a transmit signal received at the second filter port to a second frequency pass band and output the filtered transmit signal to the antenna port.

In one example, the second acoustic wave filter is configured to filter a receive signal received at the antenna port to a second frequency pass band and output the filtered receive signal to the second filter port.

In one example, the first acoustic wave filter is a band-pass filter having a pass band between 4.4 GHz and 5 GHz.

In one example, the second acoustic wave filter is a band-pass filter having a pass band between 3.3 GHz and 4.2 GHz.

According to another embodiment, there is provided a multiplexer. The multiplexer comprises a first filter assembly including a first antenna port, one or more first filter ports, one or more first acoustic wave filters connected between the first antenna port and the one or more first filter ports, and one or more ground pins, a second filter assembly including a second antenna port, one or more second filter ports, one or more second acoustic wave filters connected between the second antenna port and the one or more second filter ports, and one or more ground pins, and a metallic guard ring extending around the first and second filter assemblies. At least one of the one or more ground pins of the first filter assembly is connected to the metallic guard ring, and at least one of the one or more ground pins of the second filter assembly is connected to the metallic guard ring.

In one example, the multiplexer further comprises a conductive strip extending across the surface of the semiconductor chip between the first filter assembly and the second filter assembly, the conductive strip being connected at a first and a second end to the metallic guard ring.

In one example, the conductive strip is further connected to a ground pin located between the first filter and second filter assembly.

In one example, the first and second filter assemblies are diplexers.

In one example, the multiplexer is formed on a single semiconductor chip.

According to another embodiment, there is provided a radio-frequency module. The radio frequency module comprises a packaging substrate configured to receive a plurality of components, a first diplexer including a plurality of acoustic wave filters and one or more ground pins, a second diplexer including a plurality of acoustic wave filters and one or more ground pins, and a metallic guard ring extending around the first and second diplexers. At least one of the one or more ground pins of the first diplexer is connected to the metallic guard ring, and at least one of the one or more ground pins of the second diplexer is connected to the metallic guard ring.

In one example, the radio-frequency module is a front-end module.

According to another embodiment, there is provided a wireless device. The wireless device comprises a transceiver configured to generate a radio-frequency signal, a front-end module in communication with the transceiver, and an antenna in communication with the front-end module. The front-end module includes a packaging substrate configured to receive a plurality of components, a first diplexer having a plurality of acoustic wave filters and one or more ground pins, a second diplexer having a plurality of acoustic wave filters and one or more ground pins, a metallic guard ring extending around the first and second diplexers. At least one of the one or more ground pins of the first diplexer is connected to the metallic guard ring, and at least one of the one or more ground pins of the second diplexer is connected to the metallic guard ring.

DETAILED DESCRIPTION

Bulk acoustic wave (BAW) resonators are a form of acoustic wave resonator that generally includes a layer of piezoelectric material sandwiched between a top and a bottom electrode and suspended over a cavity that allows for the layer of piezoelectric material to vibrate. A signal applied across the top and bottom electrodes causes an acoustic wave to be generated in and travel through the layer of piezoelectric material. A BAW resonator exhibits a frequency response to applied signals with a resonance peak determined by a thickness of the film of piezoelectric material. The primary acoustic wave generated in a BAW resonator is an acoustic wave that travels through the layer of piezoelectric material in a direction perpendicular to layers of conducting material forming the top and bottom electrodes.

The International Telecommunication Union (ITU) is a specialized agency of the United Nations (UN) responsible for global issues concerning information and communication technologies, including the shared global use of radio spectrum.

The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications standard bodies across the world, such as the Association of Radio Industries and Businesses (ARIB), the Telecommunications Technology Committee (TTC), the China Communications Standards Association (CCSA), the Alliance for Telecommunications Industry Solutions (ATIS), the Telecommunications Technology Association (TTA), the European Telecommunications Standards Institute (ETSI), and the Telecommunications Standards Development Society, India (TSDSI).

Working within the scope of the ITU, 3GPP develops and maintains technical specifications for a variety of mobile communication technologies, including, for example, second generation (2G) technology (for instance, Global System for Mobile Communications (GSM) and Enhanced Data Rates for GSM Evolution (EDGE)), third generation (3G) technology (for instance, Universal Mobile Telecommunications System (UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G) technology (for instance, Long Term Evolution (LTE) and LTE-Advanced).

The technical specifications controlled by 3GPP can be expanded and revised by specification releases, which can span multiple years and specify a breadth of new features and evolutions.

In one example, 3GPP introduced carrier aggregation (CA) for LTE in Release 10. Although initially introduced with two downlink carriers, 3GPP expanded carrier aggregation in Release 14 to include up to five downlink carriers and up to three uplink carriers. Other examples of new features and evolutions provided by 3GPP releases include, but are not limited to, License Assisted Access (LAA), enhanced LAA (eLAA), Narrowband Internet of things (NB-IOT), Vehicle-to-Everything (V2X), and High Power User Equipment (HPUE).

3GPP introduced Phase 1 of fifth generation (5G) technology in Release 15, and Phase 2 of 5G technology in Release 16. Subsequent 3GPP releases will further evolve and expand 5G technology. 5G technology is also referred to herein as 5G New Radio (NR).

5G NR supports or plans to support a variety of features, such as communications over millimeter wave spectrum, beamforming capability, high spectral efficiency waveforms, low latency communications, multiple radio numerology, and/or non-orthogonal multiple access (NOMA). Although such RF functionalities offer flexibility to networks and enhance user data rates, supporting such features can pose a number of technical challenges.

Frequency Range 1 (FR1) communications technology forms part of the development program of 5G NR. In particular, FR1 communications, also known as ‘sub-6 GHz’ involve communication over high frequencies, such as between 410 MHz and 7125 MHz. The high communication frequency allows for faster data transfer rates than previous-generation communications technologies.

Embodiments of the present disclosure may be configured to handle radio-frequency signals in the range of approximately 410 MHz to approximately 7125 MHz, such as one or more bands of the FR1 communications spectrum such as n77 (about 3.3 GHz to about 4.2 GHz) or n79 (about 4.4 GHz to about 5 GHz).

Millimeter-wave (mmWave) technology also forms part of the development program of 5G NR. In particular, mmWave communications, also known as Frequency Range 2 (FR2), involve communication over high frequencies, such as between 24 GHz and 300 GHz. The high frequency allows communications using mmWave to transfer data even faster than FR1 communications, and to take advantage of a less congested spectrum.

Millimeter wave frequency bands exist in the range of 30 GHz to 300 GHz, or more particularly between 24 GHz and 53 GHz, such as Band n257 (about 26.5 GHz to about 29.5 GHz), Band n258 (about 24.25 GHz to about 27.5 GHz), Band n259 (about 39.5 GHz to 43.5 GHz), Band n260 (about 37 GHz to about 40 GHz), Band n261 (about 27.5 GHz to about 28.35 GHz), and/or Band n262 (about 47.2 GHz to about 48.2 GHz) and/or other equivalent 5G radiofrequency bands in the 5G “Frequency Range 2” range.

The teachings herein are applicable to a wide variety of communication systems, including, but not limited to, communication systems using advanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro, and/or 5G NR.

Aspects and embodiments described herein are directed to an acoustic wave filter assembly. In particular, embodiments herein reduce the effects of parasitic capacitance that become increasingly significant at high operating frequencies such as those associated with 5G NR. The increased parasitic capacitance is caused by the formation of capacitive coupling between signal inputs and the metallic guard ring surrounding the filter assembly. Embodiments disclosed herein are directed to acoustic wave filter assemblies that address the problem of reducing on-die parasitic capacitance, and therefore improved out-of-band rejection. The reduction in on-die capacitance can be achieved by forming a direct electrical connection between one or more of the ground pins of the acoustic wave filter assembly and the metallic guard ring. Embodiments disclosed herein are further directed to acoustic wave filter assemblies that address the problem of improved isolation. The improved isolation may be achieved via relocation of the one or more signal input pins.

FIG.1is a schematic showing the configuration of a known acoustic wave filter assembly, indicated generally at100. The acoustic wave filter assembly100includes a filter port101. The filter port101may be configured to connect to, for example, a transceiver module of a wireless device, and may receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly100includes an antenna port102. The antenna port may be configured to connect to an antenna, and may receive signals from the antenna, and output transmit signals to the antenna. The acoustic wave filter assembly100includes an acoustic wave filter104connected between the filter port101and the antenna port102. The acoustic wave filter104may be configured to receive signals having a certain first frequency range and output filtered signals having one or more second frequency ranges. For example, the acoustic wave filter may be a band-pass filter configured to receive signals having a relatively broad range of frequencies and output filtered signals having a frequency range corresponding to the pass band of the acoustic wave filter104. The acoustic wave filter104may comprise one or more acoustic wave resonators, such as bulk acoustic wave (BAW) resonators. The acoustic wave filter assembly100includes a ground pin103connected between the filter port101and the antenna port102. The ground pin103may be formed in or electrically connected to the acoustic wave filter104. The ground pin103may be configured to be electrically connected to ground. The acoustic wave filter assembly100may include a plurality of ground pins connected between the filter port101and the antenna port102.

The acoustic wave filter assembly100includes a metallic guard ring105extending around the acoustic wave filter assembly100. As shown, the metallic guard ring105extends around the periphery of the acoustic wave filter assembly100, including the filter port101, the antenna port102, and the ground pin103. The metallic guard ring105is formed of an electrically conducting material. The electrically conducting material may comprise gold, copper, and/or indium. The purpose of the metallic guard ring105is to provide structural support to the acoustic wave filter assembly100, and to protect the acoustic wave filter assembly100from the ingress of moisture. Additionally, the metallic guard ring105can provide electromagnetic shielding to components within the acoustic wave filter assembly100. As discussed above, the acoustic wave filter104may include one or more acoustic wave resonators. Acoustic wave resonators are fragile components, that should be protected both from physical stresses and from environmental contamination.

In operation, the acoustic wave filter assembly100may receive a transmit signal at the filter port101. The transmit signal may have a certain first frequency range. The transmit signal is passed to the acoustic wave filter104, which filters the transmit signal to a second frequency range and then outputs the filtered transmit signal to the antenna port102.

It has been found that, at high operating frequencies, such as those associated with 5G NR FR1 communications, the proximity of the metallic guard ring105to the filter port101and antenna port102can result in unwanted capacitive coupling between the metallic guard ring105and each of the filter port101and antenna port102. The resulting parasitic capacitance can reduce the performance of the acoustic wave filter104. For instance, in examples where the acoustic wave filter104is a band-pass filter, the parasitic capacitance can result in the out-of-band rejection of the acoustic wave filter104being bypassed. This can be seen looking at the frequency response curves illustrated inFIGS.6-8.

In known acoustic wave filter assemblies, the increased parasitic capacitance may be overcome by adding additional stages to the acoustic wave filter104, therefore increasing the rejection of out-of-band frequencies. However, adding additional stages to the acoustic wave filter104increases the size of the acoustic wave filter assembly.

FIG.2illustrates an acoustic wave filter assembly according to the present disclosure, indicated generally at200. The acoustic wave filter assembly includes a filter port201. The filter port201may be configured to connect to, for example, a transceiver module of a wireless device, and may receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly200includes an antenna port202. The antenna port may be configured to connect to an antenna, and may receive signals from the antenna, and output transmit signals to the antenna. The acoustic wave filter assembly200includes an acoustic wave filter204connected between the filter port201and the antenna port202. The acoustic wave filter204may be configured to receive signals having a certain first frequency range and output filtered signals having one or more second frequency ranges. For example, the acoustic wave filter may be a band-pass filter configured to receive signals having a relatively broad range of frequencies and output filtered signals having a frequency range corresponding to the pass band of the acoustic wave filter204. The pass band of the acoustic wave filter204may be a cellular frequency pass band, in particular, the pass band may be between approximately 4.4 GHz and approximately 5 GHz, or between approximately 3.3 GHz and approximately 4.2 GHz. The acoustic wave filter204includes one or more bulk acoustic wave (BAW) resonators.

It has been found that, when operating a high frequencies such as those associated with 5G NR FR1 technology, BAW resonators are preferable to other types of resonator such as surface acoustic wave (SAW) resonators due to their high quality factor (Q-factor).

The acoustic wave filter assembly200includes a ground pin203connected between the filter port201and the antenna port202. In some embodiments, the acoustic wave filter assembly201includes a plurality of ground pins connected between the filter port201and the antenna port202. The one or more ground pins203may be formed in or electrically connected to the acoustic wave filter204. The one or more ground pins203is configured to be electrically connected to ground. The acoustic wave filter assembly200includes a metallic guard ring205extending around the acoustic wave filter assembly200. In the embodiment shown, the ground pin203is further connected to the metallic guard ring205. The connection between the ground pin203and the metallic guard ring205is a direct electrical connection, such that electrical charge may flow between the metallic guard ring205and the ground pin203and vice versa. As such, when the ground pin203is connected to ground, the metallic guard ring205is grounded via the ground pin203.

In operation, the acoustic wave filter assembly200may receive a transmit signal at the filter port201. The transmit signal may have a certain first frequency range. The transmit signal is transmitted to the acoustic wave filter204, which filters the transmit signal to a second frequency range and then outputs the filtered transmit signal to the antenna port202. Alternatively, the acoustic wave filter assembly200may receive a receive signal at the antenna port202. The receive signal may have a first frequency range. The receive signal is transmitted to the acoustic wave filter204, which filters the receive signal to a second frequency range and then outputs the filtered receive signal to the filter port201.

At high operating frequencies, such as those associated with 5G NR FR1 communications, it has been found that the parasitic capacitance resulting from the coupling between the metallic guard ring205and each of the filter port201and antenna port202is reduced by virtue of the electrical connection between the ground pin203and the metallic guard ring205. The reduction in parasitic capacitance can significantly improve the filter performance at these high operating frequencies. For example, where the acoustic wave filter204is a band pass filter having a pass band between approximately 3.3 GHz to 4.2 GHz, the connection between the ground pin203and the metallic guard ring205can improve the out-of-band rejection, such as below 3.3 GHz and above 4.2 GHz. Similarly, where the acoustic wave filter204is a band pass filter having a pass band between approximately 4.4 GHz to 5 GHz, the connection between the ground pin203and the metallic guard ring205can improve the out-of-band rejection below 4.4 GHz and above 5 GHz.

FIGS.3-5illustrate filter assemblies. In particular,FIG.3illustrates a known acoustic wave filter assembly, indicated generally at300.FIG.4illustrates an exemplary acoustic wave filter assembly, indicated generally at400.FIG.5illustrates an acoustic wave filter assembly according to the present disclosure, indicated generally at500. The features of these three arrangements will be set out below, and then the relative performance of each arrangement will be discussed with reference to the signal response curves ofFIGS.6-8.

The acoustic wave filter assembly300ofFIG.3may be disposed on a substrate, for example, a silicon substrate that may include a dielectric surface layer of, for example, silicon dioxide. The acoustic wave filter assembly300includes a first filter port301A. The first filter port301A may be configured to connect to, for example, a transceiver module of a wireless device, and may receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly300includes a second filter port301B. The second filter port301B may also be configured to connect to, for example, a transceiver module of a wireless device, and may also receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly300includes an antenna port302, configured to connect to an antenna, and transmit and receive signals via the antenna. The acoustic wave filter assembly300includes a first acoustic wave filter304A connected between the first filter port301A and the antenna port302, and a second acoustic wave filter304B connected between the second filter port301B and the antenna port. Each of the acoustic wave filters304A,304B, may be configured to receive signals having a certain first frequency range, and output filtered signals. The acoustic wave filter assembly includes first and second ground pins303A,303B connected between the antenna port302and the first and second filter ports301A,301B. The acoustic wave filter assembly300includes a metallic guard ring305extending around the acoustic wave filter assembly300. The metallic guard ring305may be configured in accordance with the metallic guard ring105described above in connection with acoustic wave filter assembly100ofFIG.1.

The configuration of acoustic wave filter assembly400shown inFIG.4corresponds to the acoustic wave filter assembly300ofFIG.3, except the acoustic wave filter assembly400does not include a metallic guard ring. The acoustic wave filter assembly400is a theoretical embodiment, which will be used inFIGS.6-8to explain the relative performance of known acoustic wave filter assemblies vs. acoustic wave filter assemblies of the present disclosure.

FIG.5shows an acoustic wave filter assembly500in accordance with the present disclosure. The acoustic wave filter assembly500may be disposed on a substrate, for example, a silicon substrate that may include a dielectric surface layer of, for example, silicon dioxide. The acoustic wave filter assembly500includes a first filter port501A. The first filter port501A may be configured to connect to, for example, a transceiver module of a wireless device, and may receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly500includes a second filter port501B. The second filter port501B may also be configured to connect to, for example, a transceiver module of a wireless device, and may also receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly500includes an antenna port502, configured to connect to an antenna, and transmit and receive signals via the antenna. The acoustic wave filter assembly500includes a first acoustic wave filter504A connected between the first filter port501A and the antenna port502, and a second acoustic wave filter504B connected between the second filter port501B and the antenna port. Each of the acoustic wave filters504A,504B, may be configured to receive signals having a certain first frequency range, and output filtered signals.

In some examples, each of the acoustic wave filters504A,504B are band-pass filters. The pass band of the first acoustic wave filter504A may be different than the pass band of the second acoustic wave filter504B. As such, the acoustic wave filter assembly500may be configured as a diplexer, configured to filter transmit and receive signals at two distinct frequency bands. For example, the first acoustic wave filter504A may be a pass band filter configured to filter a received signal to a cellular frequency pass band between approximately 3.3 GHz and 4.2 GHz, and the second acoustic wave filter504B may be a pass band filter configured to filter a received signal to a cellular frequency pass band between approximately 4.4 GHz and 5 GHz. In alternative embodiments, each of the acoustic wave filters504A,504B may be a pass band filter, each having the same frequency pass band. Each of the acoustic wave filters504A,504B comprise one or more BAW resonators. The acoustic wave filter assembly includes first and second ground pins503A,503B connected between the antenna port502and the first and second filter ports501A,501B. The acoustic wave filter assembly500includes a metallic guard ring505extending around the acoustic wave filter assembly500. The metallic guard ring505may be configured in accordance with the metallic guard ring105described above in connection with acoustic wave filter assembly100ofFIG.1. As can be seen, the ground pin503B is further electrically connected to the metallic guard ring505. The connection between the ground pin503B and the metallic guard ring505is a direct electrical connection, such that electrical charge may flow between the metallic guard ring and the ground pin and vice versa. As such, when the ground pin503B is connected to ground, the metallic guard ring505is grounded via the ground pin503B. In alternative embodiments, either one or both ground pins503A,503B may be further electrically connected to the metallic guard ring505.

FIGS.6-8illustrate frequency response curves for one of the acoustic wave filters shown in each of the acoustic wave filter assembly arrangements shown inFIGS.3-5. In the exemplary embodiments shown, the acoustic wave filter is a band pass filter having a cellular frequency pass band between approximately 4.4 GHz and 5 GHz. The frequency response is measured for the second acoustic wave filters304B,404B,504B, connected between the antenna ports302,402,502and the second filter ports301B,401B,501B. However, it should be appreciated that the same results are achieved for the first acoustic wave filters304A,404A,504A. In each ofFIGS.6-8the dashed line represents the signal response curve of acoustic wave filter304B, comprised in known acoustic wave filter assembly300having a floated metallic guard ring that is not electrically connected to either ground pin303A,303B, and therefore not grounded. The dotted line represents the signal response curve of acoustic wave filter404B, shown in theoretical acoustic wave filter400ofFIG.4without a metallic guard ring. The solid line represents the signal response curve of acoustic wave filter504B, shown in acoustic wave filter assembly500ofFIG.5in accordance with the present disclosure wherein the metallic guard ring505is electrically connected to ground pin503B, and therefore grounded.

FIG.6shows the frequency response curves of the acoustic wave filters304B,404B,504B across a broad range of frequencies between approximately 0 Hz and 15 GHz. The cellular frequency pass band of the acoustic wave filters304B,404B,504B can be seen extending between lower bound601(approximately 4.4 GHz) and upper bound602(approximately 5 GHz).

FIG.7shows the out-of-band frequency response of the acoustic wave filters304B,404B,504B between 5 GHz and 6 GHz. It should be appreciated that, in the case of an acoustic wave filter with a pass band between approximately 4.4 GHz and 5 GHz, the out-of-band rejection above 5 GHz is of particular importance. This is due to the presence of the 5 GHz Wi-Fi (Registered Trade Mark) frequency band. As can be seen fromFIG.7, the out-of-band rejection of acoustic wave filter504B above 5 GHz is significantly improved compared to acoustic wave filter304B, thereby demonstrating the improved out-of-band rejection achieved via the electrical connection between ground pin503B and the metallic guard ring505. It can also be seen that the out-of-band rejection of acoustic wave filter404B above 5 GHz is significantly greater than that of acoustic wave filter304B. This supports the poor out-of-band rejection being caused by the presence of the floated metallic guard ring305.

FIG.8shows the within-band frequency response of the acoustic wave filters304B,404B,504B. As can be seen, the frequency response of the acoustic wave filters304B,404B,504B are substantially the same across the pass band between approximately 4.4 GHz and 5 GHz.

FIG.9illustrates a multiplexer in accordance with the present disclosure, indicated generally at900. In the illustrated embodiment, multiplexer900is formed on a single semiconductor die. The multiplexer900includes a first acoustic wave filter assembly900A. The first acoustic wave filter assembly900A includes a first filter port901A. First filter port901A may be configured to connect to a transceiver module of a wireless device, and may receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The first acoustic wave filter assembly900A includes a second filter port901B. Second filter port901B may also be configured to connect to a transceiver module of a wireless device, and may also receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The first acoustic wave filter assembly900A includes a first antenna port902. The first antenna port may be configured to connect to an antenna, and may receive signals from the antenna, and output transmit signals to the antenna. The first acoustic wave filter assembly900A includes first and second acoustic wave filters904A,904B connected between the first antenna port902and the first and second filter ports901A,901B respectively. In the illustrated embodiment, first acoustic wave filter904A is a band-pass filter having a cellular frequency pass band between approximately 4.4 GHz and 5 GHz. Second acoustic wave filter904B is a band-pass filter having a cellular frequency pass band between approximately 3.3 GHz and 4.2 GHz. Accordingly, the first acoustic wave filter assembly900A of multiplexer900is a diplexer, having a first filter channel and second filter channel. The first acoustic wave filter assembly900A includes first and second ground pins903A,903B connected between the first antenna port902and the first and second filter ports901A,901B. Multiplexer900includes a second acoustic wave filter assembly900B. In the illustrated embodiment, the configuration of the second acoustic wave filter assembly900B corresponds to the first acoustic wave filter assembly900A. The second acoustic wave filter assembly900B includes a third filter port911A, fourth filter port911B, and second antenna port912, with third and fourth acoustic wave filters914A,914B connected between the second antenna port912and the third and fourth filter ports911A,911B respectively. Third acoustic wave filter914A is a band-pass filter having a cellular frequency pass band between approximately 4.4 GHz and 5 GHz. Second acoustic wave filter914B is a band-pass filter having a cellular frequency pass band between approximately 3.3 GHz and 4.2 GHz. Second acoustic wave filter assembly900B includes third and fourth ground pins913A,913B connected between the second antenna port912and the third and fourth filter ports911A,911B. Accordingly, in the illustrated embodiment the multiplexer900comprises two diplexers. Thus, the multiplexer is able to receive signals at the first and second antenna ports, and filter the received signals to both the first and second filter channels (corresponding to the first and second pass bands of the first/third and second/fourth acoustic wave filters) simultaneously. It will be appreciated that in alternative embodiments, the second acoustic wave filter assembly900B need not correspond to the first acoustic wave filter assembly900A. Multiplexer900includes a metallic guard ring905extending around the multiplexer900. In the illustrated embodiment, second ground pin903B of the first acoustic wave filter assembly900A, and fourth ground pin913B of the second acoustic wave filter assembly900B are further connected to the metallic guard ring905. The connection between the ground pins903B,913B and the metallic guard ring905is a direct electrical connection, such that electrical charge may flow between the metallic guard ring905and the ground pins903B,913B and vice versa. As such, when the ground pins903B,913B are connected to ground, the metallic guard ring905is grounded via the ground pins903B,913B. The multiplexer900includes a ground pin908. The ground pin908is arranged between the first acoustic wave filter assembly900A and the second acoustic wave filter assembly900B. The ground pin908is configured to be electrically connected to ground. The ground pin908is further connected to the metallic guard ring905via a conductive strip907. The conductive strip907may be connected at either end to opposing sides of the metallic guard ring905, thereby being interposed between the first and second acoustic wave filter assemblies900A,900B. In alternative embodiments, the conductive strip907may only be connected at one end to the metallic guard strip905, and may not extend from one side of the metallic guard strip905to the other.

Accordingly, first and second acoustic filter assemblies900A,900B of multiplexer900each achieve the improved out-of-band rejection provided by connecting the metallic guard ring to at least one of the ground pins of the acoustic wave filter assemblies900A,900B.

It has been found that when providing the multiplexer900on a single semiconductor die, the isolation between the first antenna port902and second antenna port912can be improved depending on the layout of the antenna ports902,912relative to each other. The isolation between the first and second antenna ports902,912represents the amount of radio-frequency signal that travels between the first and second antenna ports902,912. Increasing the isolation results in improved performance of the multiplexer900due to the reduction in unwanted cross-talk between the antenna ports902,912.

FIG.10illustrates a multiplexer1000in accordance with the present disclosure. The multiplexer1000is substantially the same as multiplexer900, but the layout of the first and second filter ports1001A,1001B, first ground port1003A, and first antenna port1002have been modified. In particular, the relative positions of the first antenna port1002and second filter port1001B have been reversed. Similarly, the relative positions of the first filter port1001A and first ground pin1003A have been reversed. It can therefore be seen that the second filter port1001B is located in between the first and second antenna ports1002,1012, which have an increased spatial separation relative to multiplexer900. It has been found that providing a multiplexer1000wherein the first and second antenna ports1002,1012are separated by at least one of the filter ports1001A,1001B,1011A,1011B or at least one of the ground pins1003A,1003B,1013A,1013B, results in improved isolation between the first and second antenna ports1002,1012, as will be discussed in connection withFIGS.11-12.

FIGS.11and12illustrate the frequency response curve, and frequency-isolation curve of the multiplexers900,1000ofFIGS.9and10. In the exemplary embodiments shown, the acoustic wave filter is a band pass filter having a cellular frequency pass band between approximately 4.4 GHz and 5 GHz shown in either of the first or second acoustic wave filter assemblies900A,1000A,900B,1000B. The frequency-isolation is measured between the first and second antenna ports902,1002,912,1012. Also shown in bothFIGS.11and12is the frequency response curve and frequency-isolation curve of a multiplexer having a floated metallic guard ring, i.e., not electrically connected to the multiplexer. In both ofFIGS.11and12, the dashed line represents the multiplexer having a floated guard ring. The dotted line represents the multiplexer900having a grounded metallic guard ring905, and pin/port layout according toFIG.9. The solid line represents the multiplexer1000having a grounded metallic guard ring1005and modified pin/port layout according toFIG.10.

FIG.11shows the frequency response curves of multiplexers900,1000, and a multiplexer with a floated guard ring. As can be seen, the frequency response curves are substantially the same in the out-of-band region below 4.4 GHz, and in the within-band region between 4.4 GHz and 5 GHz. In the out-of-band region above 5 GHz, the out-of-band rejection of the multiplexer having a floated guard ring is lower than that of the multiplexers900,1000having a grounded metallic guard ring905,1005. On the other hand, the out-of-band rejection of the multiplexers900,1000in the out-of-band region above 5 GHz is substantially the same.

FIG.12shows the frequency-isolation curves of the multiplexers900,1000, and a multiplexer with a floated guard ring. As can be seen, the isolation of the multiplexer900with a grounded metallic guard ring905is higher than that of the multiplexer with a floated guard ring over substantially the entire frequency range between 0 Hz and 10 GHz. In addition. the isolation of the multiplexer1000with the grounded metallic guard ring1005and modified pin/port layout is higher than the isolation of the multiplexer900, and significantly higher than the isolation of the multiplexer with a floated guard ring.

FIG.13is a schematic showing the configuration of a known acoustic wave filter assembly, indicated generally at1300. The acoustic wave filter assembly1300includes a first filter port1301. The first filter port1301may be configured to connect to, for example, a transceiver module of a wireless device, and may receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly includes a first antenna port1302, configured to connect to an antenna, and transmit and receive signals via the antenna. The acoustic wave filter assembly1300includes a first acoustic wave filter1304connected between the first filter port1301and the first antenna port1302. In the illustrated embodiment, the first acoustic wave filter1304is a band-pass filter configured to receive signals and output filtered signals to a cellular frequency pass band between approximately 3.3 GHz and 4.2 GHz. The first acoustic wave filter1304comprises a plurality of BAW resonators1306connected in series and parallel between the first filter port1301and the first antenna port1302. The acoustic wave filter assembly1300includes first and second ground pins1303A,1303B connected between the first antenna port1302and the first filter port1301. The first and second ground pins1303A,1303B may be electrically connected to, or formed in, the first acoustic wave filter1304. The first and second ground pins1303A,1303B, are configured to be connected to ground. The acoustic wave filter assembly includes a second filter port1311. The second filter port1311may be configured to connect to, for example, a transceiver module of a wireless device, and may receive transmit signals from the transceiver module, and output receive signals to the transceiver module. The acoustic wave filter assembly includes a second antenna port1312, configured to connect to an antenna, and transmit and receive signals via the antenna. The acoustic wave filter assembly1300includes a second acoustic wave filter1314connected between the second filter port1311and the second antenna port1312. In the illustrated embodiment, the second acoustic wave filter1314is a band-pass filter configured to receive signals and output filtered signals to a cellular frequency pass band between approximately 3.3 GHz and 4.2 GHz. The second acoustic wave filter1314comprises a plurality of BAW resonators1316connected in series and parallel between the second filter port1311and the second antenna port1312. The acoustic wave filter assembly1300includes third and fourth ground pins1313A,1313B connected between the second antenna port1312and the second filter port1311. The third and fourth ground pins1313A,1313B may be electrically connected to, or comprised in, the second acoustic wave filter1314. The third and fourth ground pins1313A,1313B, are configured to be connected to ground. The acoustic wave filter assembly1300includes a metallic guard ring1305extending around the acoustic wave filter assembly1300. The metallic guard ring1305is formed of an electrically conducting material, such as a material comprising gold, copper, and/or indium.

FIG.14is a schematic showing the configuration of an acoustic wave filter assembly according to the present disclosure, indicated generally at1400. The filter assembly1400may be arranged on a single semiconductor die. The acoustic wave filter assembly1400may be disposed on a substrate, for example, a silicon substrate that may include a dielectric surface layer of, for example, silicon dioxide. The acoustic wave filter assembly1400may comprise the substantially the same components as acoustic wave filter assembly1300. The configuration of the components of acoustic wave filter assembly may also be substantially the same as acoustic wave filter assembly1300. Acoustic wave filter assembly1400includes a ground pin1407. The ground pin1407is configured to be electrically connected to ground. The ground pin1407is further electrically connected to the metallic guard ring1405via a conductive strip1408. Accordingly, when the ground pin1407is electrically connected to ground, the metallic guard ring1405is grounded via the ground pin1407. The ground pin1407and conductive strip1408are arranged such that the first filter port1401, first antenna port1402, first ground pins1403A,1403B, and first acoustic wave filter1404are on one side of the conductive strip1408, and the second filter port1411, second antenna port1412, second ground pins1413A,1413B, and second acoustic wave filter1414are on the opposing side of the conductive strip1408.

It has been found that the arrangement of the ground pin1407and conductive strip1408, interposed between the two sides of filter assembly1400achieves improved isolation between the first and second antenna ports1402,1412, and first and second filter ports1401,1411, as will be shown inFIGS.15-18without a reduction in filter performance.

FIGS.15-18illustrate the frequency response curves, and frequency-isolation curves of the acoustic wave filter assemblies1300,1400. In each ofFIGS.15-18, the dashed line represents the known multiplexer1300having a floated guard ring. The solid line represents the multiplexer1400according to the present disclosure having a grounded metallic guard ring, conductive strip, and modified pin/port layout.

FIG.15shows the frequency response curves of the first acoustic wave filters1304,1404of the acoustic wave filter assemblies1300,1400.FIG.16shows the frequency response curves of the second acoustic wave filter1314,1414, of the acoustic wave filter assemblies1300,1400. It can be seen that the frequency responses of both filter assemblies are substantially the same, and therefore the addition of the ground pin1407and conductive strip does not change the filter performance of the first and second acoustic wave filters1404,1414.

FIG.17shows the frequency-isolation curves representing the isolation between the first and second antenna ports1302,1312,1402,1412of the two acoustic wave filter assemblies1300,1400.FIG.18shows the frequency-isolation curves representing the isolation between the first and second filter ports1301,1311,1401,1411of the two acoustic wave filter assemblies1300,1400. It can be seen that both the filter port-filter port isolation, and antenna port-antenna port isolation of the acoustic wave filter assembly1400according to the invention are improved across substantially the entire frequency range from approximately 0 Hz to 10 GHz compared to the acoustic wave filter assembly1300.

The acoustic wave filter assemblies ofFIGS.2,5,9,10, and14, may also be included in a radio-frequency module, such as a radio-frequency front-end (RFFE) module. A schematic of an exemplary module is shown inFIG.19.

FIG.19illustrates a radio-frequency module according to the present disclosure, indicated generally at1900. The radio-frequency module1900may be, for example, a front-end module (FEM). The radio-frequency module1900may be connected between a transceiver module and an antenna of a wireless electronic device. The radio-frequency module includes a packaging substrate1901. The packaging substrate1901is configured to receive a plurality of components. For example, the packaging substrate1901may be configured to receive a front-end power management integrated circuit (FE-PMIC) component, a power amplifier assembly, a match component, and one or more acoustic wave filter assemblies can be mounted and/or implemented on and/or within the packaging substrate1901. The power amplifier assembly may include a plurality of power amplifiers and/or low-noise amplifiers. In the illustrated example, the radio-frequency module1900includes a first diplexer1902and a second diplexer1903. The first diplexer1902and the second diplexer1903each include a plurality of acoustic wave filters and one or more ground pins. The first diplexer1902and the second diplexer1903are each configured to pass, in two directions, two different cellular frequency bands. The two frequency bands may comprise, for example, a first frequency band between approximately 3.3 GHz and 4.2 GHz, and a second frequency band between approximately 4.4 GHz and 5 GHz. The radio-frequency module1900includes a metallic guard ring1904. In accordance with the present disclosure, at least one of the ground pins of each of the first and second diplexers1902,1903is further electrically connected to the metallic guard ring1904. In some embodiments, the radio-frequency module1900may include other components such as surface-mount technology (SMT) devices and an antenna switch module, which may be mounted on the packaging substrate1901.

FIG.20is a schematic diagram of a wireless device2000that can include aspects of the present invention. The wireless device can be, for example but not limited to, a portable telecommunication device such as, a mobile cellular-type telephone. The wireless device2000can include an antenna2001. The antenna2001is configured to transmit and receive wireless radio-frequency signals. The antenna2001is connected to a front-end-module2002. The front-end module2002can include one or more acoustic wave filter assemblies according to the present disclosure, including one or more metallic guard rings grounded via one or more ground pins of the acoustic wave filters comprised in the one or more acoustic wave filter assemblies. The front-end module2002is connected to a transceiver2003. The transceiver2003is configured to generate radio-frequency signals for transmission and process incoming radio-frequency signals received from the antenna2001. The wireless device2000includes a battery2004for supplying electrical power to the various components of the wireless device2000. The wireless device2000includes a processor2006, and a computer-readable medium2007to facilitate operation of the wireless device2000. The computer-readable medium2007can be used for a wide variety of purposes, such as storing data and/or instructions to facilitate the operation of the wireless device2000and/or to provide storage of user information. The battery2004can be any suitable battery for use in a wireless device, including, for example, a lithium-ion battery. The wireless device2000can include one or more of a microphone arrangement, and may include a baseband system, a power management system, a user interface, and an audio codec. The wireless device2000may include multiple antennas. The antennas can include antennas for transmitting and/or receiving signals associated with a wide variety of frequencies and communications standards. The baseband system may be coupled to the user interface to facilitate processing of various user input and output, such as voice and data. The baseband system may provide the transceiver2003with digital representations of transmit signals, which the transceiver processes to generate radio-frequency signals for transmission. The baseband system may also process digital representations of received signals provided by the transceiver.

The teachings of the invention provided herein can be applied to other systems, not necessarily the systems described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The words “coupled” or connected,” as generally used herein, refer to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.