Front-end architecture for carrier aggregation

Abstract

A carrier aggregation circuit includes a primary signal path for processing a first frequency band, the first frequency band being a TDD frequency band, and a secondary signal path for processing a second frequency band. The primary signal path includes a first TDD filter configured to process a receive signal in the first frequency band and a second TDD filter configured to process a transmit signal in the first frequency band, the first TDD filter and the second TDD filter including one or more corresponding initial stages that are identical. Related front-end architectures, front-end modules, and wireless devices for carrier aggregation are also provided.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63 / 311,696, entitled “CARRIER AGGREGATION FRONT-END ARCHITECTURE,” filed on February 18, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] background Field Aspects of the present disclosure relate to carrier aggregation in radio frequency applications. [Background technology]

[0003] 2. Description of Related Art Carrier aggregation (CA) is a data transmission strategy that transmits data across multiple frequency bands to increase data bandwidth and thereby increase bit rates. In some Radio Frequency (RF) applications, cellular carrier aggregation can include two or more RF signals processed through a common path. For example, carrier aggregation can include the use of paths for multiple bands with well-separated frequency ranges. In such a configuration, simultaneous operation of two or more bands can be achieved. Summary of the Invention [Means for solving the problem]

[0004] overview According to one aspect of the present disclosure, a carrier aggregation circuit is provided, the carrier aggregation circuit comprising: a primary signal path for processing a first frequency band, the first frequency band being a first time division duplex (TDD) frequency band; and a secondary signal path for processing a second frequency band, the primary signal path including a first time division duplex filter configured to process a receive signal in the first frequency band and a second time division duplex filter configured to process a transmit signal in the first frequency band, the first time division duplex filter and the second time division duplex filter including one or more corresponding initial stages that are identical.

[0005] In one example, the first frequency band is a primary component carrier (PCC) and the second frequency band is a secondary component carrier (SCC).

[0006] In one example, the first time division duplex filter is coupled to the one or more initial stages and includes one or more further stages optimized for processing received signals in a first frequency band.

[0007] In one example, the second time division duplex filter is coupled to the one or more initial stages and includes one or more further stages optimized for processing transmit signals in the first frequency band.

[0008] In one example, one or more corresponding initial stages comprise a single resonator, a pair of parallel and series resonators, or multiple parallel and series resonators.

[0009] In one example, the one or more initial stages are configured to be coupled to an antenna port.

[0010] In another example, the one or more initial stages are configured to be coupled to the antenna port, and the one or more further stages of the first time division duplex filter and the second time division duplex filter are coupled to the antenna port via the one or more initial stages.

[0011] In one example, the second frequency band is either a frequency division duplex (FDD) frequency band or a second time division duplex frequency band.

[0012] In one example, the secondary path is configured to include a duplexer configured to process signals in a second frequency band utilizing a frequency division duplexing scheme.

[0013] In one example, the secondary path is configured to include a third time division duplex filter configured to process receive signals in the second frequency band and a fourth filter configured to process transmit signals in the second frequency band, where the third time division duplex filter and the fourth time division duplex filter include one or more corresponding initial stages that are identical.

[0014] In one example, the first time division duplex filter and the second time division duplex filter may be implemented as a bulk acoustic wave (BAW) filter or a surface acoustic wave (SAW) filter.

[0015] In one example, the secondary path is configured to include a third time division duplex filter configured to process receive signals in the second frequency band and a fourth filter configured to process transmit signals in the second frequency band, the third time division duplex filter and the fourth time division duplex filter include one or more corresponding initial stages that are identical, and the third time division duplex filter and the fourth time division duplex filter are implemented as bulk acoustic wave (BAW) filters or surface acoustic wave (SAW) filters.

[0016] In one example, the first frequency band is from about 2,300 MHz to 2,400 MHz, or from about 2,496 MHz to 2,690 MHz.

[0017] In one example, the second frequency band is about 1,920 MHz to 1,980 MHz and about 2,110 MHz to 2,170 MHz, or about 1,710 MHz to 1,785 MHz and about 1,805 MHz to 1,880 MHz, or about 2,500 MHz to 2,570 MHz and about 2,620 MHz to 2,690 MHz, or about 1,850 MHz to 1,915 MHz and about 1,930 MHz to 1,995 MHz, or about 1,880 MHz to 1,920 MHz, or about 1,710 MHz to 1,780 MHz and about 2,110 MHz to 2,200 MHz.

[0018] In one example, the first frequency band is approximately 2,300 MHz to 2,400 MHz, and the second frequency band is either approximately 1,920 MHz to 1,980 MHz and approximately 2,110 MHz to 2,170 MHz, or approximately 1,710 MHz to 1,785 MHz and approximately 1,805 MHz to 1,880 MHz, or approximately 2,500 MHz to 2,570 MHz and approximately 2,620 MHz to 2,690 MHz.

[0019] In one example, the first frequency band is about 2,496 MHz to 2,690 MHz and the second frequency band is about 1,920 MHz to 1,980 MHz and about 2,110 MHz to 2,170 MHz, or about 1,710 MHz to 1,785 MHz and about 1,805 MHz to 1,880 MHz, or about 1,850 MHz to 1,915 MHz and about 1,930 MHz to 1,995 MHz, or about 1,880 MHz to 1,920 MHz, or about 1,710 MHz to 1,780 MHz and about 2,110 MHz to 2,200 MHz.

[0020] In one example, the primary signal path includes a power amplifier (PA) configured to amplify a signal for transmission and a low noise amplifier (LNA) configured to amplify a received signal.

[0021] According to another aspect of the present disclosure, a front-end architecture configured to support carrier aggregation is provided, the front-end architecture comprising: a first node configured to be coupled to an antenna; a second node configured to be coupled to a transceiver; a primary signal path for processing a first frequency band, the first frequency band being a first Time Division Duplex (TDD) frequency band; and a secondary signal path for processing a second frequency band, the primary signal path including a first time division duplex filter configured to process a receive signal in the first frequency band and a second time division duplex filter configured to process a transmit signal in the first frequency band, the first time division duplex filter and the second time division duplex filter including one or more corresponding initial stages that are identical.

[0022] According to another aspect of the present disclosure, a front-end module configured to support carrier aggregation is provided. the front-end module comprises a primary signal path for processing a first frequency band, the first frequency band being a first time division duplex (TDD) frequency band, and a secondary signal path for processing a second frequency band, the primary signal path including a first time division duplex filter module configured to process receive signals in the first frequency band and a second time division duplex filter module configured to process transmit signals in the first frequency band, the first time division duplex filter module and the second time division duplex filter module including one or more filters having one or more corresponding initial stages that are identical; an antenna switch module coupled to the antenna port and at least the primary signal path and the secondary signal path; a low noise amplifier (LNA) module including one or more low noise amplifiers configured to amplify signals received at the antenna port via the first time division duplex filter module; and a power amplifier (PA) module including one or more power amplifiers configured to amplify signals received at the transceiver port for providing to the second time division duplex filter module.

[0023] One example further comprises a multiplexer coupled to the power amplifier module and the low noise amplifier module, the multiplexer configured to direct the amplified signal along multiple paths.

[0024] Another example further comprises a frequency division duplex (FDD) filter module configured to process received signals in the second frequency band and to process transmitted signals in the second frequency band.

[0025] According to another aspect of the present disclosure, a wireless device is provided, the wireless device comprising: an antenna configured to receive and transmit a plurality of cellular frequency bands; a transceiver configured to provide a transmitted signal and to provide a received signal; and a front-end module, the primary signal path for processing a first frequency band, the first frequency band being a first Time Division Duplex (TDD) frequency band, and a secondary signal path for processing a second frequency band, the primary signal path including a first time division duplex filter configured to process a received signal of the first frequency band, and a second time division duplex filter configured to process a transmitted signal of the first frequency band. and a time division duplex filter including a first time division duplex filter and a second time division duplex filter including one or more corresponding initial stages that are identical, and a front-end module including: an antenna switch module coupled to an antenna port and at least a primary signal path and a secondary signal path; a low noise amplifier module including one or more low noise amplifiers configured to amplify a signal received at the antenna port through the first time division duplex filter; and a power amplifier module including one or more power amplifiers configured to amplify a signal received at the transceiver port for providing to the second time division duplex filter.

[0026] Further aspects, embodiments, and advantages of these exemplary aspects and embodiments are described in detail below. The embodiments disclosed herein can be combined with other embodiments in any manner consistent with at least one of the principles disclosed herein, and references to "embodiments," "some embodiments," "alternative embodiments," "various embodiments," "one embodiment," and the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. Appearances of such terms in this specification do not necessarily all refer to the same embodiment.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS Various aspects of at least one embodiment are described below with reference to the accompanying drawings, which are not drawn to scale. The drawings are included to provide illustration and further understanding of the various aspects and embodiments, are incorporated in and constitute a part of this specification, and are not intended as a definition of the limitations of the invention. In the drawings, each identical or nearly identical component shown in the various figures is represented by a similar reference numeral. For clarity, not every component is labeled in every figure. [Brief description of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of a first known carrier aggregation (CA) configuration that includes a CA circuit configured to receive an input and provide an output. [Diagram 2] FIG. 2 is a schematic diagram of a second known CA arrangement capable of processing more than two radio frequency signals. [Diagram 3] FIG. 1 is a schematic diagram of a third known CA circuit implemented as a receiver with a low noise amplifier. [Figure 4] FIG. 1 is a schematic diagram of a known CA architecture that uses a combination of Time Division Duplex (TDD) and Frequency Division Duplex (FDD) frequency bands to provide carrier aggregation. [Diagram 5] FIG. 2 is a schematic diagram of an alternative known CA architecture that uses a combination of two TDD frequency bands to perform carrier aggregation. [Figure 6] 1 is a graph showing the calculated impairment effect on the received signal across a normalized timeslot for a known CA architecture; [Figure 7] FIG. 2 is a schematic diagram of a first CA architecture according to an embodiment of the present disclosure. [Figure 8] FIG. 2 is a schematic diagram of a second CA architecture according to an embodiment of the present disclosure. [Figure 9] FIG. 1 is a schematic diagram of a known filter design; [Figure 10A] FIG. 2 is a schematic diagram of a filter design according to an aspect of the present disclosure. [Figure 10B] 1 is a schematic diagram of an alternative filter design according to an aspect of the present disclosure. [Figure 11] FIG. 2 is a schematic diagram of a front-end module for carrier aggregation according to an aspect of the present disclosure. [Figure 12] FIG. 1 is a schematic diagram of a wireless device for carrier aggregation according to an aspect of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Detailed Description Aspects and embodiments described herein relate to carrier aggregation architectures that enable reduced insertion loss, reduced switching loss, and reduced degradation of secondary component carrier (SCC) signals.

[0030] It should be understood that the embodiments of the method and apparatus described herein are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The method and apparatus may be implemented in other embodiments and may be practiced or carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. Additionally, the phraseology and terminology used herein are for purposes of explanation and should not be considered limiting. The use of "including," "comprising," "having," "containing," "involving," and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to "or" may be construed as inclusive, such that any term described using "or" may refer to either a single, more than one, and all of the described term.

[0031] Cellular carrier aggregation (CA) may be supported by allowing two or more radio frequency (RF) signals to be processed over a common path. For example, carrier aggregation may include the use of paths for multiple bands with well-separated frequency ranges. In such a configuration, simultaneous operation of two or more bands is possible.

[0032] In such carrier aggregation systems, it is desirable to maintain a low noise figure (NF) for each RF signal, and if the two bands being aggregated are close in frequency, it is also desirable to maintain sufficient separation between the two bands.

[0033] In the context of a receiver, carrier aggregation can enable simultaneous processing of RF signals of multiple bands, for example to provide high data rate capabilities. In particular, fourth generation (4G) and fifth generation (5G) handsets support multiple CA band combinations in a single circuit configuration.

[0034] FIG. 1 is a schematic diagram of a carrier aggregation (CA) configuration 100 including a CA circuit 110 configured to receive multiple inputs and generate an output. The multiple inputs can include a first RF signal and a second RF signal. The first RF signal can be provided to the CA circuit 110 from a common input node 102 (RF_IN) via a first path 104a including a first filter 106a. Similarly, the second RF signal can be provided to the CA circuit 110 from the common input node 102 (RF_IN) via a second path 104b including a second filter 106b. As described herein, the CA circuit 110 can be configured such that the output at the common output node 114 is a recombined RF signal including two separated frequency bands associated with the first and second RF signals. As also described herein, the CA circuit 110 can be configured to provide desirable performance characteristics such as low loss, low noise figure, and / or high isolation between the two signal paths 104a, 104b.

[0035] Various examples herein, including the example of FIG. 1, are described in the context of aggregating two frequency bands. However, it will be understood that one or more features of the present disclosure can be implemented with aggregating three or more frequency bands. For example, FIG. 2 is a schematic diagram of a CA configuration 100 in which three RF signals are separated at a common input node 102 (RF_IN), processed through respective filters 106a, 106b, 106c, and recombined by a CA circuit 110 to generate a recombined RF signal at a common output node 114 (RF_OUT).

[0036] For purposes of explanation, such signal paths may be referred to as the "A", "B", and "C" bands, and such bands may include any combination of RF bands suitable for carrier aggregation. The frequency bands may be cellular frequency bands, such as Universal Mobile Telecommunications System (UMTS) frequency bands. For example, the first frequency band may be UMTS downlink or "Rx" band 3 from 1805 megahertz (MHz) to 1880 MHz, the second frequency band may be UMTS downlink or "Rx" band 66 from 2110 MHz to 2200 MHz, and the third frequency band may be UMTS downlink or "Rx" band 40 from 2300 MHz to 2400 MHz.

[0037] Other downlink frequency bands, such as those listed in Table 1 below, or other non-UMTS frequency bands may be used.

[0038] [Table 1] TIFF2025508303000003.tif85170

[0039] Frequency bands operating in frequency division duplex (FDD) mode perform simultaneous transmit (Tx) and receive (Rx) operations over different frequencies. For example, band 3 operates with transmit signals having frequencies between about 2500 MHz and about 2570 MHz and receive signals having frequencies between about 2620 MHz and about 2690 MHz. This is typically accomplished through the use of a duplexer that couples the Tx and Rx paths to a common terminal. In contrast, frequency bands operating in time division duplex (TDD) mode have a single frequency band utilized for both Tx and Rx operations. For example, band 40 operates with a single frequency band between about 2300 MHz and about 2400 MHz.

[0040] The CA configuration 100 of FIG. 1 and FIG. 2 can be implemented in a number of RF applications. FIG. 3 illustrates a more specific example in which a CA circuit 110 having one or more features described herein can be implemented in a low noise amplifier (LNA) of a receiver. The CA circuit 110 can be configured to receive multiple inputs and generate an output. The multiple inputs can include a first RF signal and a second RF signal. The first RF signal can be provided to the CA circuit 110 from a common input node 102 (RF_IN) via a first path that includes a first bandpass filter 122a. Similarly, the second RF signal can be provided to the CA circuit 110 from the common input node 102 (RF_IN) via a second path that includes a second bandpass filter 122b. As described herein, the CA circuit 110 can be configured such that the output at the common output node 114 is a recombined RF signal that includes two separated frequency bands associated with the first and second RF signals. The CA circuit 110 can also be configured to provide desirable performance characteristics, such as low loss, a low noise figure, and / or high isolation between the two input signal paths.

[0041] 3, the recombined RF signal is shown as being provided to LNA 130 and amplified to thereby generate a low noise amplified output signal at output node 114. LNA 130 may be configured to operate with a bandwidth wide enough to effectively amplify first and second bands of the recombined RF signal.

[0042] It will be appreciated that in some embodiments, a separate LNA may be implemented for each signal path, with the RF signal being recombined after each constituent signal has been amplified. In some embodiments, the bandpass filter 122 may be implemented in a number of ways, including, for example, a surface acoustic wave (SAW) filter. It will be appreciated that other types of filters may be utilized.

[0043] In the case of downlink carrier aggregation, the bandwidths of multiple receive bands are combined to increase throughput (i.e., the speed at which signals are processed) and improve the user experience. However, the use of TDD frequency bands in legacy architectures brings several drawbacks. As mentioned above, in the TDD mode of operation, both transmit (Tx) and receive (Rx) operations are performed using a single frequency band. Legacy architectures typically provide common signal paths and components for both transmit and receive operations to reduce chip space. However, transmit and receive operations have different requirements, and therefore it is not possible to optimize the common circuit components on the TDD signal path to fully support both operations simultaneously.

[0044] FIG. 4 is a schematic diagram of a known architecture 400 that enables performing carrier aggregation (CA) using a combination of TDD and FDD frequency bands. In the TDD-FDD architecture shown in FIG. 4, signals may be received or transmitted via a common node 402 coupled to an antenna. An antenna switch module (ASM) 404 is configured to switch between a first signal path 406a and a second signal path 406b, such that one of these paths may be selected for use as a primary component carrier (PCC) path and the other path is selected for use as a secondary component carrier (SCC) path. For downlink CA, the PCC path provides both receive and transmit signals, while the SCC path provides only receive signals. For uplink CA, both the PCC path and the SCC path provide receive and transmit signals.

[0045] 4, the first signal path 406a is configured to handle the FDD frequency band and is used as an SCC path, while the second signal path 406b is configured to handle the TDD frequency band and is used as a PCC path. The ASM can be a single pole multiple throw (SPMT) switch with each throw coupled to an individual filter and / or individual duplexer.

[0046] 4, the first signal path 406a includes an FDD duplexer 408a, a transmit path 412a, and a receive path 414a. The transmit path 412a includes a power amplifier (PA) 416a configured to amplify a signal for transmission by an antenna, and an output node 420a coupled to the PA 416a and configured to provide the signal to the PA 416a for amplification and transmission. The receive path 414a includes a low noise amplifier (LNA) 418a configured to amplify a signal received by the antenna, and an input node 422a coupled to the LNA 418a and configured to receive the amplified signal from the LNA 418a.

[0047] The second signal path 406b comprises a single TDD filter 408b, a transmit / receive switch 410, a transmit path 412b, and a receive path 414b. The transmit path 412b comprises a power amplifier (PA) 416b configured to amplify a signal for transmission by an antenna, and an output node 420b coupled to the PA 416b and configured to provide the signal to the PA 416b for amplification and transmission. The receive path 414b comprises a low noise amplifier (LNA) 418b configured to amplify a signal received by the antenna, and an input node 422b coupled to the LNA 418b and configured to receive the amplified signal from the LNA 418b.

[0048] Since the FDD operating modes use different frequency regimes to transmit and receive signals, the first signal path 406a carrying the FDD signal contains two separate filters, implemented in the example of FIG. 4 as FDD duplexers. Each of these FDD filters can be individually optimized as a transmit or receive filter for a particular operating frequency regime. In contrast, the TDD operating mode uses a single frequency to transmit and receive signals, and therefore the second signal path 406b contains a common TDD filter for both Rx and Tx operations.

[0049] FIG. 5 illustrates an alternative known architecture 500 that uses a combination of two TDD frequency bands to perform carrier aggregation. In the TDD-TDD architecture illustrated in FIG. 5, signals may be received or transmitted via a common node 502 coupled to an antenna. An antenna switch module (ASM) 504 is configured to switch between a first signal path 506a and a second signal path 506b. In the example illustrated in FIG. 5, the first signal path 506a is configured to process a first TDD frequency band, and the second signal path 506b is configured to process a second TDD frequency band. Either of the two TDD frequency bands may be a PCC, and the other TDD frequency band may be a SCC.

[0050] 5, the first signal path 506a includes a first TDD filter 508a, a first transmit / receive switch 510a, a transmit path 512a, and a receive path 514a. The transmit path 512a includes a power amplifier (PA) 516a configured to amplify a signal for transmission by an antenna, and an output node 520a coupled to the PA 516a and configured to provide the signal to the PA 516a for amplification and transmission. The receive path 514a includes a low noise amplifier (LNA) 518a configured to amplify a signal received by the antenna, and an input node 522a coupled to the LNA 518a and configured to receive the amplified signal from the LNA 518a.

[0051] The second signal path 506b comprises a second TDD filter 508b, a second transmit / receive switch 510b, a transmit path 512b, and a receive path 514b. The transmit path 512b comprises a power amplifier (PA) 516b configured to amplify a signal for transmission by an antenna, and an output node 520b coupled to the PA 516b and configured to provide the signal to the PA 516b for amplification and transmission. The receive path 514b comprises a low noise amplifier (LNA) 518b configured to amplify a signal received by the antenna, and an input node 522b coupled to the LNA 518b and configured to receive the amplified signal from the LNA 518b.

[0052] Typically, for the architectures shown in Figures 4 and 5, mid-band or high-band frequency bands may be used as FDD bands. In a particular embodiment, the first signal path 406a is configured to use band 1, band 3, band 7, band 25, band 39, and / or band 66 as FDD or TDD bands, and the second signal path 406b is configured to use band 40 and / or band 41 as TDD bands. In an embodiment where the second signal path 406b processes band 41 signals, the first signal path 406a typically processes band 1, band 3, band 25, band 39, or band 66 signals. When the second signal path 406a processes band 40, the first signal path 406a typically processes band 1, band 3, or band 7 signals.

[0053] In the example shown in Figure 4, the first signal path 406a is configured to provide an FDD frequency band as a secondary component carrier (SCC), and the second signal path 406b is configured to provide a TDD frequency band as a primary component carrier (PCC). In Figure 5, the first TDD frequency band acts as the primary component carrier (PCC) and the second TDD frequency band acts as the secondary component carrier (SCC), and respective transmit / receive switches 410 are used to provide transmit signals to the TDD PA and receive signals to the TDD LNA.

[0054] However, as mentioned above, a single transmit / receive (TRx) filter cannot be fully optimized for both Tx and Rx functions. Therefore, when a single TDD TRx filter is used to process a PCC signal, the TRx filter must completely eliminate signal noise and harmonics originating from the user equipment to ensure that the transmitted signal is sufficiently clean, but also completely eliminate blockers, signal noise and interference from the local environment for the received signal. Therefore, a common TRx filter must block a wide range of frequencies, leading to increased out-of-band impedance and increased insertion loss.

[0055] In addition, as shown in the architectures of Figures 4 and 5, the TDD signal path includes two switches, which increases the PCB footprint and increases switch losses. Cascading the transmit / receive switch with the ASM, as shown in Figures 4 and 5, can result in large switch losses of approximately 0.25 dB at mid-band frequencies and approximately 0.4 dB at high-band frequencies.

[0056] Therefore, it would be preferable to have separate TDD Tx and Rx filters to optimize the performance of each filter and to eliminate the requirement for a transmit / receive switch. However, this is not easy to achieve in practice.

[0057] This is primarily due to the additional chip space required by the additional filters. Additionally, the use of separate Tx and Rx filters requires switch-coupling of the transmitted and received RF signals, but switching between non-ideal filters (i.e., filters with finite quality (Q) factors) results in loading effects on the other signal paths. For example, when a TDD signal path is used as a primary component carrier (PCC) path, switching between the TDD Tx and Rx filters results in an out-of-band impedance being presented on the secondary component carrier (SCC) path. Thus, the received SCC signal experiences amplitude and phase changes due to the out-of-band impedance presented by one or more of the TDD Rx and Tx filters.

[0058] Furthermore, amplitude and phase changes may also derive from differences in signal transmission path lengths and / or lack of synchronicity between different evolved Node B (eNodeB) base stations. Such scenarios result in misalignment between transmit and receive time slots, for example, when switching from transmit to receive mode occurs in the middle of a receive slot instead of at the beginning of the receive slot. This also results in loading effects and degradation on the received SCC signal.

[0059] Figure 6 illustrates the degrading effect that amplitude changes have on the received signal when switching between Rx and Tx modes at various times throughout a normalized timeslot. The example shown in Figure 6 illustrates how a simulated 1 dB amplitude shift affects an FDD Rx signal, as quantified by the error vector magnitude (EVM) of the Rx signal, which can be caused by the loading effects outlined above.

[0060] As shown in FIG. 6, when an amplitude shift occurs at the boundaries of a receive timeslot (i.e., at "0" and "1" on the x-axis), there is no change in the Rx signal. This is because, in an ideal situation, the modem expects the switch between transmit and receive modes to occur near the transmit / receive slot boundaries, and therefore the modem calculates a compensation factor at the beginning of each timeslot to compensate for the gain change that occurs during the mode switch. However, if the mode switch occurs in the middle of the timeslot, the compensation factor used during the timeslot is no longer valid and cannot compensate for the sudden amplitude or phase shift. Thus, the change that occurs towards the middle of the timeslot is the furthest from the slot boundaries and therefore has the largest predicted EVM value. As shown in FIG. 6, the peak EVM value is nearly 6% towards the middle of the slot (i.e., around "0.5" on the x-axis), while EVM values ​​of more than 5% (i.e., between about "0.25" and about "0.75" on the x-axis) occur in the central portion of the timeslot.

[0061] Under the 3GPP® standard, modulation schemes such as 256-QAM require a maximum EVM of 3.5% across the entire transmission architecture, including the baseband modem, RF integrated circuit, and front-end module. It is therefore desirable to keep the maximum EVM at or below 2% within the front-end module. EVM values ​​above about 2% result in significant degradation in the Rx signal, which means that signal packets need to be retransmitted by the eNodeB, thus significantly reducing the achievable throughput. However, more stringent future modulation schemes such as 1024-QAM may require maximum EVM values ​​to be even lower than 2%.

[0062] It should be noted that the known architectures shown in Figures 4 and 5 do not result in degradation of the Rx signal in the manner described above, since there is only a single TDD filter in the PCC path, and therefore the input impedance presented by the common TDD filter does not change. If an FDD frequency band were used as a PCC instead of a TDD frequency band, the FDD frequency band would use separate bands for transmitting and receiving signals, and would therefore have respective Rx and Tx FDD filters optimized for their respective specific functions. Thus, no switching between filters is required in any of these scenarios, and therefore the above problems do not arise.

[0063] FIG. 7 illustrates a schematic diagram of a first architecture 700 embodying aspects of the present disclosure. The architecture 700 enables performing carrier aggregation (CA) using a combination of TDD and FDD frequency bands. In the TDD-FDD architecture illustrated in FIG. 7, signals may be received or transmitted via a common node 702 coupled to an antenna. The ASM 704 is configured to switch between a first signal path 706a, a second signal path 706b, and a third signal path 706c. In a preferred embodiment, the first signal path 706a is configured as an SCC path, the second signal path 706b is configured as a PCC Tx path, and the third signal path 706c is configured as a PCC Rx path.

[0064] The first signal path 706a in FIG. 7 has similar characteristics as the first signal path 406a in FIG.

[0065] The second signal path 706b includes a transmit path 712b including a single TDD Tx filter 708b, a power amplifier (PA) 716b configured to amplify the signal for transmission by the antenna, and an output node 720b coupled to the PA 716b and configured to provide the signal to the PA 716b for amplification and transmission.

[0066] The third signal path 706c includes a single TDD Rx filter 708c, a receive path 714c including a low noise amplifier (LNA) 718c configured to amplify a signal received by the antenna, and an input node 722c coupled to the LNA 718c and configured to receive the amplified signal from the LNA 718c.

[0067] FIG. 8 illustrates a schematic diagram of a second architecture 800 embodying aspects of the present disclosure. The architecture 800 enables performing carrier aggregation (CA) using a combination of two TDD frequency bands. In the TDD-TDD architecture illustrated in FIG. 8, a signal may be received or transmitted via a common node 802 coupled to an antenna. The ASM 804 is configured to switch between a first signal path 806a, a second signal path 806b, a third signal path 806c, and a fourth signal path 806d.

[0068] The first signal path 806a in FIG. 8 is configured for a first TDD frequency band and includes a transmit path 812a including a single TDD Tx filter 808a, a power amplifier (PA) 816a configured to amplify a signal for transmission by an antenna, and an output node 820a coupled to the PA 816a and configured to provide the signal to the PA 816a for amplification and transmission.

[0069] The second signal path 806b is also configured for the first TDD frequency band and includes a single TDD Rx filter 808b, a receive path 814b including a low noise amplifier (LNA) 818b configured to amplify a signal received by the antenna, and an input node 822b coupled to the LNA 818b and configured to receive the amplified signal from the LNA 818b.

[0070] The third signal path 806c of FIG. 8 includes the same features as the first signal path 806a, but is configured for a second TDD frequency band.

[0071] The fourth signal path 806d of FIG. 8 includes the same features as the second signal path 806b, but is also configured for the second TDD frequency band.

[0072] In a particular embodiment, the first signal path 806a is configured as an SCC Tx path, the second signal path 806b is configured as an SCC Rx path, the third signal path 806c is configured as a PCC Tx path, and the fourth signal path 806d is configured as a PCC Rx path. However, it will be understood that in other embodiments, the first signal path 806a and the second signal path 806b may be configured as PCC paths, and the third signal path 806c and the fourth signal path 806d may be configured as SCC paths.

[0073] Figure 9 is a schematic diagram of a filter 900, such as the TDD Tx or Rx filter shown in Figure 7 or Figure 8. The exemplary filter 900 shown in Figure 9 is configured as a passband or ladder filter and includes multiple bulk acoustic wave (BAW) resonators. However, it will be appreciated that high performance filters used in cellular applications may be implemented with bulk acoustic wave resonators (BAW), surface acoustic wave resonators (SAW), or any other resonators with a suitably high Q factor.

[0074] The ladder filter 900 includes a number of series resonators S1, S2, S3, and S4 coupled in series between an input port PORT1 and an output port PORT2. The filter 900 also has a number of parallel resonators P1, P2, P3 connected between the terminals of the series resonators and ground. The example of FIG. 9 includes four series resonators S1, S2, S3, S4 and three parallel resonators P1, P2, P3, although it will be understood that more or fewer series and / or parallel resonators may be included in the filter 900.

[0075] The resonators of ladder filter 900 may be grouped into different stages. In some embodiments, a filter stage may comprise a single resonator, a pair of parallel and series resonators, or multiple parallel and series resonators. An initial or first order filter stage may comprise one or more groups of series and parallel resonators located on the antenna side of filter 900. One or more subsequent filter stages may comprise one or more groups of series and parallel resonators coupled to one or more initial stages on the opposite side of the initial filter stage from the antenna (i.e., the user equipment side).

[0076] FIG. 10A is a schematic diagram of a TDD Tx filter 1010 and a TDD Rx filter 1020 embodying an embodiment of the present invention and including two pairs of parallel and series resonators. With reference to FIG. 9, the exemplary TDD Tx filter 1010 and the TDD Rx filter 1020 may be configured as a passband or ladder filter and may include multiple bulk acoustic wave (BAW) resonators, surface acoustic wave resonators (SAW), or any other resonators having a suitably high Q factor. The TDD TX filter 1010 and the TDD Rx filter 1020 may be implemented in the architectures of FIG. 7 and / or FIG. 8 to provide the advantages described herein.

[0077] The TDD Tx filter 1010 shown in Fig. 10A includes a number of series resonators S11, S12, S1X, and S1Y coupled in series between a transmit port Tx and an antenna port ANT. The TDD Tx filter 1010 also includes a number of parallel resonators P11, P12, P1X, and P1Y connected between the terminals of the respective series resonators and ground. The resonators S1X, S1Y, P1X, and P1Y form a Tx initial filter stage, and the resonators S11, S12, P11, and P12 form a subsequent filter stage.

[0078] The TDD Rx filter 1020 shown in Fig. 10A includes a number of series resonators S21, S22, S2X, and S2Y coupled in series between the receiving port Rx and the antenna port ANT. The TDD Rx filter 1020 also includes a number of parallel resonators P21, P22, P2X, and P2Y connected between the terminals of the respective series resonators and ground. The resonators S2X, S2Y, P2X, and P2Y form an Rx initial filter stage, and the resonators S21, S22, P21, and P22 form a subsequent filter stage. Those skilled in the art will appreciate that, although not shown in the example of Fig. 10A, there may be further filter stages between the initial filter stage and the subsequent filter stage.

[0079] In the example of Fig. 10A, the Rx initial filter stage is the same or substantially the same as the Tx initial filter stage, in other words, the initial filter stage is common to both the Rx and Tx filters, such that resonator S1X has substantially the same characteristics as resonator S2X, resonator S1Y has substantially the same characteristics as resonator S2Y, resonator P1X has substantially the same characteristics as resonator P2X, and resonator P1Y has substantially the same characteristics as resonator P2Y.

[0080] Figure 10B is a schematic diagram of an alternative filter design for the TDD Tx and Rx filters shown in Figure 10A. The filter design shown in Figure 10B is the same as the filter design in 10A, but further includes an additional series resonator on the antenna side. Thus, the exemplary filter shown in Figure 10B includes a first TDD Tx filter 1030 and a TDD Rx filter 1040, each filter with two parallel resonators and three series resonators.

[0081] The TDD Tx filter 1030 of Figure 10B includes multiple series resonators S11, S12, S1X, S1Y, and S1Z, and multiple parallel resonators P11, P12, P1X, and P1Y. The resonators S1X, S1Y, S1Z, P1X, and P1Y form a Tx initial filter stage, and the resonators S11, S12, P11, and P12 form a subsequent Tx filter stage.

[0082] The TDD Rx filter 1040 of Figure 10B includes a number of series resonators S21, S22, S2X, S2Y, and S2Z, and a number of parallel resonators P21, P22, P2X, and P2Y. The resonators S2X, S2Y, S2Z, P2X, and P2Y form an Rx initial filter stage, and the resonators S21, S22, P21, and P22 form a subsequent Rx filter stage.

[0083] As with the filter of Fig. 10A, in Fig. 10B the Rx initial filter stage is the same or substantially the same as the Tx initial filter stage, in other words the initial filter stage is common to both the Rx and Tx filters such that resonator S1X has substantially the same characteristics as resonator S2X, resonator S1Y has substantially the same characteristics as resonator S2Y, resonator S1Z has substantially the same characteristics as resonator S2Z, resonator P1X has substantially the same characteristics as resonator P2X, and resonator P1Y has substantially the same characteristics as resonator P2Y.

[0084] The TDD Tx filter 1030 and the TDD Rx filter 1040 may include BAW resonators, SAW resonators, or any other resonators having a suitably high Q factor, and may be implemented in the architectures of Figures 7 and / or 8 to provide the advantages described herein.

[0085] In some embodiments, the TDD Rx and Tx filters comprise multiple identical and corresponding, i.e., common, initial filter stages. In a preferred embodiment, the TDD Rx and Tx filters comprise multiple subsequent filter stages. The exact number of filter stages required may depend on the frequency bands being used as the PCC and SCC.

[0086] The input impedance of the initial filter stages dominates the total input impedance presented by the TDD filter as a whole. Therefore, ensuring that one or more of the initial filter stages of the TDD Rx filter and the TDD Tx filter are identical will present the same input impedance to the ASM. Ensuring that the TDD Rx filter and the TDD Tx filter present the same input impedance to the ASM means that switching between Rx and Tx modes does not induce amplitude or phase changes on the SCC path, unlike known architectures.

[0087] Subsequent filter stages have relatively little effect on the input impedance presented to the ASM, but allow each filter to be tuned for optimum Rx or Tx performance for a particular TDD frequency band.

[0088] Thus, embodiments of the present invention advantageously provide optimized TDD Rx and Tx filters that do not suffer from throughput degradation and offer reduced switch and insertion loss by eliminating the need for a TDD Rx / Tx switch cascaded with the ASM.

[0089] 11 is a schematic diagram of a front-end module 1100 for carrier aggregation embodying an embodiment of the present invention. The front-end module 1100 includes an ASM 1110 coupled to an antenna port (ANT). The ASM is configured to direct a transmit signal to the antenna port for transmission via the antenna. Similarly, the ASM is configured to direct a receive signal from the antenna port to a target filter and / or a duplexer. The ASM can be a single-pole, multi-throw (SPMT) switch with individual throws coupled to the target filters and / or duplexers.

[0090] For embodiments using FDD frequency bands as the SCC, the front-end module 1100 may also include an FDD filter module 1120 including one or more FDD filters for filtering FDD signals in one or more FDD cellular frequency bands. As described above, the FDD filter module 1120 may include a duplexer configured to process signals utilizing a frequency division duplexing scheme. The FDD filter module 1120 is coupled to the ASM 1110 to receive the FDD signals for directing to a low noise amplifier.

[0091] The front-end module 1100 includes a TDD Rx filter module 1130 including one or more TDD Rx filters configured to filter received TDD signals in one or more TDD cellular frequency bands. The front-end module 1100 also includes a TDD Tx filter module 1140 including one or more TDD Tx filters configured to filter TDD signals for transmission in one or more TDD cellular frequency bands. The TDD Rx filter module 1130 is coupled to the ASM 1110 to direct received TDD signals to a low noise amplifier for amplification. The TDD Tx filter module 1140 is coupled to a transceiver port (TRx) via a multiplexer to receive TDD signals for transmission.

[0092] Thus, the ASM 1100 is configured to direct signals between the FDD filter and / or the TDD filter and the antenna port.

[0093] It will be appreciated that one or more signals or cellular frequency bands may be conducted between the ASM 1110 and the FDD filter module 1120, and one or more signals or cellular frequency bands may be conducted between the ASM 1110 and each of the TDD Rx filter module 1130 and the Tx filter module 1140. It will also be appreciated that the front-end module 1100 includes impedance matching components, filters, phase shifting components, etc. (not shown in FIG. 11 ) to reduce signal degradation within the front-end module.

[0094] The front-end module 1100 may include a multiplexer (MUX) 1150 configured to direct signals along multiple paths. The multiplexer 1150 may be implemented as a switch and may include one or more poles and / or throws. The multiplexer 1150 may be configured to receive signals from a power amplifier module for transmission and direct those signals along multiple paths to an antenna port. The multiplexer 1150 may be further configured to receive signals from one or more of an FDD filter and / or a TDD Rx filter and / or a TDD Tx filter and direct those signals along multiple paths to a power amplifier module or a low noise amplifier module for further processing.

[0095] The front-end module 1100 includes a power amplifier module 1160 having one or more power amplifiers (PAs) configured to amplify signals received at a transceiver port (TRx). The front-end module 1100 may further include an envelope tracker configured to modify a supply voltage to the power amplifiers to increase the efficiency of the one or more power amplifiers. In a preferred embodiment, such as the example shown in FIG. 11, the envelope tracker is implemented as part of the power amplifier module 1160.

[0096] The front-end module 1100 also includes a low noise amplifier (LNA) module 1170 including one or more low noise amplifiers configured to amplify signals received at the antenna ports. The low noise amplifier module 1170 is coupled to the FDD filter module 1120 and the TDD Rx filter module 1130 to amplify received signals utilizing time division duplexing and provide amplified signals to the transceiver ports.

[0097] Figure 12 is a schematic diagram of a wireless device 1200 including the front-end module 1100 of Figure 11 and embodying aspects of the present invention. The wireless device 1200 may be, for example, but not limited to, a mobile communication device such as a mobile cellular telephone.

[0098] The wireless device 1200 may include an antenna 1210, a multiplexer 1220, a front-end module 1100, a power management module 1230, a transceiver 1240, a baseband subsystem 1250, a memory 1260, and a user interface 1270.

[0099] As described above, the front-end module 1100 may include an antenna switch module (ASM) 1110, an FDD filter module 1120, a TDD Rx filter module 1130, a TDD Tx filter module 1140, a multiplexer 1150, a power amplifier (PA) module 1160, and a low noise amplifier (LNA) module 1170.

[0100] In the exemplary wireless device 1200, the front-end module 1100 is coupled to the antenna 1210 via a multiplexer 1220. The multiplexer 1220 is configured to direct received signals to the front-end module 1100 for processing.

[0101] The transmitted signal may be routed from the transceiver 1240 to the PA module of the front-end module 1110, where the signal is amplified. The signal is then routed through a multiplexer, a filter and / or duplexer, and an ASM before being passed to the antenna 1210 for transmission. Similarly, the received signal is routed from the antenna 1210 through the multiplexer 1220 and directed to the front-end module 1110. The signal is routed and filtered using the ASM 1110 and a filter / duplexer before being amplified by the LNA module 1170. The amplified received signal may then be routed from the LNA module 1170 to the transceiver 1240.

[0102] In some embodiments, the wireless device 1200 may include multiple front-end modules, each for a particular combination of RF frequency bands. In such embodiments, the multiplexer 1220 may direct the received signal to one or more targeted front-end modules, which may be configured to process signals in the corresponding frequency bands. For example, the wireless device may include a low-band front-end module configured to process low-band cellular signals, a mid-band front-end module configured to process mid-band cellular signals, and a high-band front-end module configured to process high-band cellular signals. In some embodiments, the wireless device may include a front-end module configured to process both mid-band and high-band signals.

[0103] The transceiver 1240 interacts with a baseband subsystem 1250 configured to provide conversion between data and / or voice signals suitable for a user and RF signals suitable for the transceiver. The transceiver 1240 is also connected to a power management module 1230 (e.g., a power management integrated circuit or PMIC) configured to manage power for operation of the wireless device. Such power management can control operation of the baseband subsystem and the front-end module.

[0104] The baseband subsystem 1250 is connected to a memory 1260 configured to store data and / or instructions to facilitate operation of the wireless device 1200 and / or to provide storage of information for a user. The baseband subsystem 1250 is also connected to a user interface 1270 to facilitate various inputs and outputs of voice and / or data provided to and received from the user.

[0105] Several other wireless device configurations can utilize one or more of the features described herein. For example, the wireless device can include additional antennas, such as diversity antennas, and additional connectivity features, such as Wi-Fi, Bluetooth, and GPS.

[0106] Although several aspects of at least one embodiment have been described above, it should be understood that various changes, modifications, and improvements may readily occur to those skilled in the art. Such changes, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the present invention. Accordingly, the foregoing description and drawings are merely exemplary, and the scope of the present invention should be determined from proper construction of the appended claims and their equivalents.

Claims

1. A carrier aggregation circuit, comprising: a primary signal path for processing a first frequency band, the first frequency band being a first time division duplex (TDD) frequency band; a secondary signal path for processing a second frequency band; the primary signal path includes a first time division duplex filter configured to process receive signals in the first frequency band and a second time division duplex filter configured to process transmit signals in the first frequency band; the first time division duplex filter and the second time division duplex filter include one or more corresponding initial stages that are identical.

2. 2. The carrier aggregation circuit of claim 1, wherein the first frequency band is a primary component carrier (PCC) and the second frequency band is a secondary component carrier (SCC).

3. 2. The carrier aggregation circuit of claim 1, wherein the first time division duplex filter comprises one or more further stages coupled to the one or more initial stages and optimized for processing received signals in the first frequency band.

4. 2. The carrier aggregation circuit of claim 1, wherein the second time division duplex filter comprises one or more further stages coupled to the one or more initial stages and optimized for processing transmit signals in the first frequency band.

5. 2. The carrier aggregation circuit of claim 1, wherein the one or more corresponding initial stages comprise a single resonator, a pair of parallel and series resonators, or multiple parallel and series resonators.

6. The carrier aggregation circuit of claim 1 , wherein the one or more initial stages are configured to be coupled to an antenna port.

7. 2. The carrier aggregation circuit of claim 1, wherein the one or more initial stages are configured to be coupled to an antenna port, and one or more further stages of the first time division duplex filter and the second time division duplex filter are coupled to the antenna port via the one or more initial stages.

8. 2. The carrier aggregation circuit of claim 1, wherein the second frequency band is either a Frequency Division Duplex (FDD) frequency band or a second Time Division Duplex frequency band.

9. 10. The carrier aggregation circuit of claim 1, wherein the secondary path is configured to include a duplexer configured to process signals in the second frequency band utilizing a frequency division duplexing scheme.

10. 2. The carrier aggregation circuit of claim 1, wherein the secondary path is configured to include a third time division duplex filter configured to process a receive signal in the second frequency band and a fourth filter configured to process a transmit signal in the second frequency band, and the third time division duplex filter and the fourth time division duplex filter include one or more corresponding initial stages that are identical.

11. 2. The carrier aggregation circuit of claim 1, wherein the first time division duplex filter and the second time division duplex filter are implemented as a bulk acoustic wave (BAW) filter or a surface acoustic wave (SAW) filter.

12. 2. The carrier aggregation circuit of claim 1, wherein the secondary path is configured to include a third time division duplex filter configured to process a receive signal in the second frequency band and a fourth filter configured to process a transmit signal in the second frequency band, the third time division duplex filter and the fourth time division duplex filter including one or more corresponding initial stages that are identical, and the third time division duplex filter and the fourth time division duplex filter are implemented as a bulk acoustic wave (BAW) filter or a surface acoustic wave (SAW) filter.

13. 2. The carrier aggregation circuit of claim 1, wherein the first frequency band is approximately 2,300 MHz to 2,400 MHz, or approximately 2,496 MHz to 2,690 MHz.

14. 2. The carrier aggregation circuit of claim 1, wherein the second frequency band is about 1,920 MHz to 1,980 MHz and about 2,110 MHz to 2,170 MHz, or about 1,710 MHz to 1,785 MHz and about 1,805 MHz to 1,880 MHz, or about 2,500 MHz to 2,570 MHz and about 2,620 MHz to 2,690 MHz, or about 1,850 MHz to 1,915 MHz and about 1,930 MHz to 1,995 MHz, or about 1,880 MHz to 1,920 MHz, or about 1,710 MHz to 1,780 MHz and about 2,110 MHz to 2,200 MHz.

15. 2. The carrier aggregation circuit of claim 1, wherein the first frequency band is about 2,300 MHz to 2,400 MHz, and the second frequency band is any of about 1,920 MHz to 1,980 MHz and about 2,110 MHz to 2,170 MHz, or about 1,710 MHz to 1,785 MHz and about 1,805 MHz to 1,880 MHz, or about 2,500 MHz to 2,570 MHz and about 2,620 MHz to 2,690 MHz.

16. 2. The carrier aggregation circuit of claim 1, wherein the first frequency band is about 2,496 MHz to 2,690 MHz, and the second frequency band is about 1,920 MHz to 1,980 MHz and about 2,110 MHz to 2,170 MHz, or about 1,710 MHz to 1,785 MHz and about 1,805 MHz to 1,880 MHz, or about 1,850 MHz to 1,915 MHz and about 1,930 MHz to 1,995 MHz, or about 1,880 MHz to 1,920 MHz, or about 1,710 MHz to 1,780 MHz and about 2,110 MHz to 2,200 MHz.

17. 2. The carrier aggregation circuit of claim 1, wherein the primary signal path includes a power amplifier (PA) configured to amplify a signal for transmission and a low noise amplifier (LNA) configured to amplify a received signal.

18. 1. A front-end module configured to support carrier aggregation, comprising: a primary signal path for processing a first frequency band, the first frequency band being a first time division duplex (TDD) frequency band; a secondary signal path for processing a second frequency band; the primary signal path includes a first time division duplex filter module configured to process receive signals in the first frequency band and a second time division duplex filter module configured to process transmit signals in the first frequency band; the first time division duplex filter module and the second time division duplex filter module include one or more filters having one or more corresponding initial stages that are identical; an antenna switch module coupled to an antenna port and to at least the primary signal path and the secondary signal path; a low noise amplifier (LNA) module including one or more low noise amplifiers configured to amplify signals received at the antenna port through the first time division duplex filter module; a power amplifier (PA) module including one or more power amplifiers configured to amplify signals received at a transceiver port for providing to the second time division duplex filter module; A front-end module comprising:

19. 20. The front-end module of claim 18, further comprising a multiplexer coupled to the power amplifier module and the low noise amplifier module, the multiplexer configured to direct the amplified signal along multiple paths.

20. 20. The front-end module of claim 18, further comprising a frequency division duplex (FDD) filter module configured to process receive signals in the second frequency band and to process transmit signals in the second frequency band.

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