Apparatus and method for self-interference cancellation

Abstract

Embodiments of the present disclosure relate to a user equipment apparatus, method, and computer program for self-interference cancellation The UE apparatus comprises a first transmit chain (210) comprising a power amplifier, PA, (211) and a coupler (213) connected serially, a second transmit chain (220) comprising a PA (221) and a coupler (223) connected serially, and an interference cancellation circuit (230) configured to feed an output signal of an aggressor transmit chain back to an input terminal of a PA in a victim transmit chain to cancel interference of the aggressor transmit chain with the victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain (210) and the second transmit chain (220) causing the interference, and the victim transmit chain is another one of the first transmit chain (210) and the second transmit chain (220) subject to the interference.

Description

APPARATUS AND METHOD FOR SELF-INTERFERENCE CANCELLATIONFIELD

[0001] Embodiments of the present disclosure generally relate to the field of wireless communication, and in particular to a device, method, and a computer program for self-interference cancellation (SIC).BACKGROUND

[0002] A communication network can be seen as a facility that enables communications between two or more communication devices, or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network.

[0003] Such communication networks operate in accordance with standards, such as those promulgated by third generation partnership project (3 GPP) or European telecommunications standards institute (ETSI). Examples of such standards include the so-called 5th generation (5G) standard, 6th generation (6G), or other standards promulgated by 3 GPP.

[0004] However, there might be UL-to-UL self-interference issues at user equipment (UE), especially for UE supporting individual uplink (UL) power control for each configured UL multiple input multiple output (MIMO) layer.SUMMARY

[0005] In general, example embodiments of the present disclosure provide devices, methods and a computer program for self-interference cancellation.

[0006] In a first aspect, there is provided a user equipment (UE) apparatus. The UE apparatus comprises a first transmit chain comprising a power amplifier (PA) and a coupler connected serially, a second transmit chain comprising a PA and a coupler connected serially, and an interference cancellation circuit configured to feed an output signal of an aggressor transmit chain back to an input terminal of a PA in a victim transmit chain to cancel interference of the aggressor transmit chain with the victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain and the second transmit chain causing the interference, and the victim transmit chain is another one of the first transmit chain and the second transmit chain subject to the interference.

[0007] In some implementations, the interference cancellation circuit is further configured to tune the output signal of the aggressor transmit chain in accordance with an interference signal of the aggressor transmit chain at an output terminal of the victim transmit chain.

[0008] In some implementations, the output signal of the aggressor transmit chain is tuned to have substantially same amplitude and approximately 180 degrees out of phase with the interference signal of the aggressor transmit chain at the output terminal of the victim transmit chain.

[0009] In some implementations, the interference cancellation circuit comprises a phase rotating module and an amplitude adjusting module connected serially, and an input terminal of the interference cancellation circuit is connected to the coupler of the first transmit chain or the coupler of the second transmit chain via a first selective switch, an output terminal of the interference cancellation circuit is connected to an input terminal of the PA in the second transmit chain or an input terminal of the PA in the first transmit chain via a second selective switch.

[0010] In some implementations, the interference cancellation circuit comprises: a first feedback receiver configured to receive the output signal in the aggressor transmit chain, a second feedback receiver configured to receive an output signal of the victim transmit chain, and a control circuit configured to tune an output signal of the first feedback receiver and combine the tuned output signal of the first feedback receiver with an output signal of the second feedback receiver.

[0011] In some implementations, the interference cancellation circuit comprises a first subcircuit and a second sub-circuit, wherein each of the first sub-circuit and the second sub-circuit comprises the first feedback receiver, the second feedback receiver, and the control circuit of their own, wherein the first sub-circuit is configured to cancel interference of the second transmit chain with the first transmit chain, the second sub-circuit is configured to cancel interference of the first transmit chain with the second transmit chain.

[0012] In some implementations, the first feedback receiver of the first sub-circuit has an input terminal connected to a reverse coupling path of the coupler of the first transmit chain and an output terminal connected to the control circuit of the first sub-circuit, wherein the second feedback receiver of the first sub-circuit has an input terminal connected to a forward coupling path of the coupler of the first transmit chain and an output terminal connected to the control circuit of the first sub-circuit, wherein the control circuit of the first sub-circuit has an output terminal connected to the input terminal of the PA in the first transmit chain, wherein the first feedback receiver of the second sub-circuit has an input terminal connected to a reverse coupling path of the coupler of the second transmit chain and an output terminal connected to the control circuit of the second sub-circuit, wherein the second feedback receiver of the second sub-circuit has an input terminal connected to a forward coupling path of the coupler of the second transmit chain, and an output terminal connected to the control circuit of the second sub-circuit, and wherein the control circuit of the second sub-circuit has an output terminal connected to the input terminal of the PA in the second transmit chain.

[0013] In some implementations, the interference cancellation circuit comprises a first subcircuit and a second sub-circuit, and the first sub-circuit and the second sub-circuit share the same first feedback receiver and the same control circuit and have the second feedback receiver of their own, wherein the second feedback receiver of the first sub-circuit has an input terminal connected to a forward coupling path of the coupler of the first transmit chain and an output terminal connected to the control circuit, wherein the second feedback receiver of the second sub-circuit has an input terminal connected to a forward coupling path of the coupler of the second transmit chain and an output terminal connected to the control circuit, wherein the first feedback receiver has an input terminal connected to the coupler of the first transmit chain or the coupler of the second transmit chain via a third selective switch, and an output terminal is connected to the control circuit, and wherein the control circuit has a first output terminal connected to the input terminal of the PA in the first transmit chain and a second output terminal connected to the input terminal of the PA in the second transmit chain.

[0014] In some implementations, the input terminal of the first feedback receiver is connected to a reverse coupling path of the coupler of the first transmit chain or a reverse coupling path of the coupler of the second transmit chain via the third selective switch.

[0015] In some implementations, the input terminal of the first feedback receiver is connected to a forward coupling path of the coupler of the first transmit chain or a forward coupling path of the coupler of the second transmit chain via the third selective switch, wherein the input terminal the second feedback receiver of the first sub-circuit is connected to a reverse coupling path or the forward coupling path of the coupler of the first transmit chain via a fourth switch, wherein the input terminal of the second feedback receiver of the second sub-circuit is connected to a reverse coupling path or the forward coupling path of the coupler of the second transmit chain via a fifth switch, wherein the forward coupling path of the coupler of the first transmit chain is connected to the input terminal of the second feedback receiver of the first sub-circuit and the input terminal of the first feedback receiver via a first splitter, and wherein the forward coupling path of the coupler of the second transmit chain is connected to the input terminal of the second feedback receiver of the second sub-circuit and the input terminal of the first feedback receiver via a second splitter.

[0016] In some implementations, the interference cancellation circuit comprises: a first feedback receiver configured to receive one of the output signal of the aggressor transmit chain and the output signal of the victim transmit chain, a second feedback receiver configured to receive another of the output signal of the aggressor transmit chain and an output signal of the victim transmit chain, and a control circuit connected to the first feedback receiver and the second feedback receiver and configured to tune an output signal of the aggressor transmit chain and combine the tuned output signal of the aggressor transmit chain with an output signal of the victim transmit chain.

[0017] In some implementations, the first feedback receiver has an input terminal connected to a reverse coupling path of the coupler of the second transmit chain or a forward coupling path of the coupler of the first transmit chain via a sixth selective switch, and an output terminal connected to the control circuit, wherein the second feedback receiver has an input terminal connected to a forward coupling path of the coupler of the second transmit chain or a reverse coupling path of the coupler of the first transmit chain via a seventh selective switch, and an output terminal connected to the control circuit, wherein the control circuit has a first output terminal connected to the input terminal of the PA in the first transmit chain, and a second output terminal connected to the input terminal of the PA in the second transmit chain.

[0018] In a second aspect, there is provided a method implemented at a UE apparatus, wherein the UE apparatus comprises: a first transmit chain, a second transmit chain (220), and an interference cancellation circuit. The method comprises obtaining, by the interference cancellation circuit, an output signal of an aggressor transmit chain. The method further comprises tuning, by the interference cancellation circuit, the output signal in accordance with an interference signal of the aggressor transmit chain at an output terminal of the victim transmit chain. The method further comprises outputting, by the interference cancellation circuit, the tuned output signal to an input terminal of a power amplifier (PA) in a victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain and the second transmit chain causing the interference, and the victim transmit chain is another one of the first transmit chain (210) and the second transmit chain subject to the interference.

[0019] In some implementations, the output signal is tuned to have substantially same amplitude and approximately 180 degrees out of phase with the interference signal.

[0020] In a third aspect, there is provided a computer program. The computer program comprising instructions which, when executed by an apparatus, cause the apparatus to perform the method according to the second aspect above.

[0021] In a fourth aspect, there is provided a non-transitory computer readable medium. The non-transitory computer readable medium comprising program instructions for causing the user equipment apparatus at least to perform the method according to the second aspect above.

[0022] It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Some embodiments will now be described with reference to the accompanying drawings, in which:

[0024] FIG. 1A illustrates an example network environment in which some embodiments of the present disclosure can be implemented;

[0025] FIG. 1B illustrates an illustrative diagram of UL-to-UL self-interference according to some embodiments of the present disclosure;

[0026] FIG. 2 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0027] FIG. 3 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0028] FIG. 4 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0029] FIG. 5 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0030] FIG. 6 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0031] FIG. 7 illustrates an example coupler according to some embodiments of the present disclosure;

[0032] FIG. 8 illustrates an example antenna according to some embodiments of the present disclosure;

[0033] FIG. 9 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0034] FIG. 10 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0035] FIG. 11 illustrates an example circuit for self-interference cancellation according to some embodiments of the present disclosure;

[0036] FIG. 12 illustrates a simulation model according to some embodiments of the present disclosure;

[0037] FIG. 13 illustrates a simulation result according to some embodiments of the present disclosure;

[0038] Fig. 14 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

[0039] Fig. 15 illustrates a simplified block diagram of an apparatus that is suitable for implementing embodiments of the present disclosure; and

[0040] Fig. 16 illustrates a block diagram of an example computer readable medium in accordance with some embodiments of the present disclosure.

[0041] Throughout the drawings, the same or similar reference numerals represent the same or similar elements.DETAILED DESCRIPTION

[0042] Principles of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

[0043] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0044] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0045] It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0046] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0047] As used in this application, the term “circuitry” may refer to one or more or all of the following:(a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0048] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0049] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the future fifth generation (5G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0050] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NRNB (also referred to as a gNB), a remote radio unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

[0051] As used herein, the term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0052] Principles and embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0053] Reference is first made to Fig. 1A, which illustrates an example communication system 100 in which embodiments of the present disclosure may be implemented. The system 100 includes a network device 110. The network device 110 serves area 130 (also called as cell 130). The system 100 also includes one or more terminal devices, such as terminal devices 120, and 121. The terminal devices 120, 121 are capable of connecting and communicating in an uplink (UL) and downlink (DL) with the network device 110. In communication systems, an UL refers to a link in a direction from a terminal device to a network device, and a DL refers to a link in a direction from the network device to the terminal device.

[0054] It is to be understood that the number of network device and terminal devices is only for the purpose of illustration without suggesting any limitations. The system 100 may include any suitable number of network device and terminal devices adapted for implementing embodiments of the present disclosure.

[0055] Communications in the communication system 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (1G), the second generation (2G), the third generation (3G), the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), frequency division duplex (FDD), time division duplex (TDD), multiple-input multiple-output (MIMO), orthogonal frequency division multiple (OFDM), discrete fourier transform spread OFDM (DFT-s-OFDM) and / or any othertechnologies currently known or to be developed in the future.

[0056] Among others, an issue addressed by some embodiments of the present disclosure is how to cancel UL-to-UL self-interference (also referred to as TX self-interference) in UE, especially in UE that supports individual UL power control for each configured UL MIMO layer (e.g., projected new feature for 6G).

[0057] Ideally, antennas for UL MIMO at UE are isotropic and with infinite RF isolation between the antennas so that there is no UL-to-UL self-interference. However, radiation patterns for antennas implemented on a real UE are far from isotropic with perfect orthogonal behavior. In addition, each of the implemented UE antennas will have differences in the following antenna characteristics:• total radiation efficiency;• Directivity;• angular direction of the maximum gain.Such differences in antenna characteristics will result in SINR imbalance at a gNB for different UL MIMO layers. Therefore, due to non-ideal isolation (coupling) between antennas of the UE and non-ideal antenna impedance match, self-interference may occur.

[0058] Reference is now made to Fig. 1B, which illustrates an illustrative diagram of UL-to-UL self-interference according to some embodiments of the present disclosure. There are two different types of UL-to-UL self-interference. For example, a first signal radiated from a first antenna and received at a second antenna might be directed into a second Tx branch connected to the second antenna. This is referred as “coupled contribution of Layer #1 in Fig, IB. This may affect power amplifier (PA) implementation relying on digital pre-distortion (DPD). As another example, a first signal may be radiated from a first antenna and reflected at a second antenna (referred as “Antenna Reflected Contribution of Layer#l @ MiMo Channel #2 in Fig, IB”). The power level of that reflected first signal will be present at the radiated second signal from the second antenna. The contribution of the first signal at the radiated second signal will be seen as noise / interference and affect the SINR at the gNB.

[0059] According to embodiments of the present disclosure, there is provided a UE apparatus for self-interference cancellation. In an aspect of the UE apparatus, the UE apparatus comprises a first transmit chain comprising a power amplifier (PA) and a coupler connected serially, a second transmit chain comprising a PA and a coupler connected serially, and an interference cancellation circuit configured to feed an output signal of an aggressor transmit chain back to an inputterminal of a PA in a victim transmit chain to cancel interference of the aggressor transmit chain with the victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain and the second transmit chain causing the interference, and the victim transmit chain is another one of the first transmit chain and the second transmit chain subject to the interference. In this way, UL-to-UL self-interference at the UE apparatus may be cancelled.Example Circuits

[0060] Reference is now made to Fig. 2, which shows the basic principle for self-interference cancellation as proposed in embodiments of the present disclosure. The example circuit 200 may be implemented in a UE, for example, the terminal device 120 as illustrated in Fig. 1 A.

[0061] The example circuit 200 may comprise a first transmit chain 210, a second transmit chain 220, and an interference cancellation circuit 230. The first transmit chain 210 may comprise a power amplifier (PA) 211 and a coupler 213 connected serially. The first transmit chain 210 may have an output terminal 219. The PA 211 may have an input terminal 215 and an output terminal 217. The second transmit chain 220 may comprise a PA221 and a coupler 223 connected serially. The second transmit chain 220 may have an output terminal 229. The PA 221 may have an input terminal 225 and an output terminal 227.

[0062] In some embodiments, the first transmit chain 210 may be an aggressor transmit chain causing interference, while the second transmit chain 220 may be a victim transmit chain subject to the interference. In some other embodiments, the second transmit chain 220 may be the aggressor transmit chain, while the first transmit chain 210 may be the victim transmit chain. In other words, the aggressor transmit chain is one of the first transmit chain 210 and the second transmit chain 220 causing the interference, and the victim transmit chain is another one of the first transmit chain 210 and the second transmit chain 220 subject to the interference. It is to be understood that interfere process may or may not be symmetric for the first transmit chain 210 and the second transmit chain 220.

[0063] The interference cancellation circuit 230 may be configured to feed an output signal of an aggressor transmit chain back to an input terminal of a PA in a victim transmit chain to cancel interference of the aggressor transmit chain with the victim transmit chain. In other words, the interference cancellation circuit 230 may be configured to feed an output signal of the first transmit chain 210 back to the input terminal 225 of the PA 221 in the second transmit chain 220 to cancel interference of the first transmit chain 210 with the second transmit chain 220, and / or feed an output signal of the second transmit chain 220 back to the input terminal 215 of the PA 211 in thefirst transmit chain 210 to cancel interference of the second transmit chain 220 with the first transmit chain 210.

[0064] In some embodiments, the interference of the aggressor transmit chain means a coupled contribution of an aggressor signal transmitted by the aggressor transmit chain and received at the output terminal of the victim transmit chain.

[0065] In some embodiments, the interference cancellation circuit 230 is further configured to tune the output signal of the aggressor transmit chain in accordance with an interference signal of the aggressor transmit chain at an output terminal of the victim transmit chain.

[0066] In some embodiments, the output signal of the aggressor transmit chain is tuned to have substantially same amplitude and approximately 180 degrees out of phase with the interference signal of the aggressor transmit chain at the output terminal of the victim transmit chain.

[0067] With the implementation of the example circuit 200, the cancellation signal (i.e. the tuned output signal of the aggressor transmit chain) is fed back to the input of the PA, and would be amplified by the PA, so that a required power level for the cancellation signal is thereby reduced.

[0068] In some embodiments, the output terminal 219 of the first transmit chain 210 may be connected to a first antenna 218. The output terminal 229 of the second transmit chain 220 may be connected to a second antenna 228.

[0069] In some embodiments, the PA in the transmit chain may alternatively be any other analog or digital gain stage in the transmit chain.

[0070] The TX SIC concept as illustrated in Fig. 2 may work by feeding the aggressor TX signal back to the input of the victim TX chain and add it to the victim signal after phase rotating and amplitude adjusting in such a way that it has substantially same amplitude but approximately 180 degree out of phase with the aggressor signal at the output of the victim transmit chain). In this way is the SINR of a victim signal maintained / enhanced when transmitted by the antenna).

[0071] In some embodiments, the aggressor TX signal is obtained from the coupler of the aggressor transmit chain (e.g. by a forward coupling path). In some embodiments, the aggressor TX signal is obtained from the coupler of the victim transmit chain (e.g. by a reverse coupling path), as the aggressor TX signal would couple to the output terminal of the victim transmit chain and propagate through the coupler of the victim transmit chain.

[0072] Reference is now made to Fig. 3, which shows an example circuit 300 for self-interference cancellation. The example circuit 300 may be a detailed implementation of the example circuit 200.

[0073] As illustrated in Fig. 3, the input terminal 215 of the PA 211 of the first transmit chain 210 and the input terminal 225 of the PA 221 of the second transmit chain 220 are connected to a baseband and transceiver 350 to receive the input signal to the PAs 211 and 221 respectively. The interference cancellation circuit 230 may comprise a phase rotating module 310 and an amplitude adjusting module 320 connected serially. An input terminal of the interference cancellation circuit 230 is connected to the coupler 213 of the first transmit chain 210 or the coupler 223 of the second transmit chain 220 via a first selective switch 330 (also referred to as RF switch). An output terminal of the interference cancellation circuit 230 is connected to the input terminal 225 of the PA 221 in the second transmit chain 220 or the input terminal 215 of the PA 211 in the first transmit chain 210 via a second selective switch 340.

[0074] In a case that the first transmit chain 210 is the aggressor transmit chain and the second transmit chain 220 is the victim transmit chain, the first selective switch 330 may be switched to connect with the coupler 213 of the first transmit chain 210 and the second selective switch 340 may be switched to connect with an input terminal 225 of the PA 221 in the second transmit chain 220). Thus, the interference cancellation circuit 230 may feed an output signal of the first transmit chain 210 back to the input terminal 225 of the PA 221 in the second transmit chain 220 to cancel interference of the first transmit chain 210 with the second transmit chain 220. This set up is shown in Fig. 3 with the corresponding states of the first selective switch and the second selective switch.

[0075] In a case that the second transmit chain 220 is the aggressor transmit chain and the first transmit chain 210 is the victim transmit chain, the first selective switch 330 may be switched to connect with the coupler 223 of the second transmit chain 220 and the second selective switch 340 may be switched to connect with the PA 211 in the first transmit chain 210). Therefore, the interference cancellation circuit 230 may feed an output signal of the second transmit chain 220 back to the input terminal 215 of the PA 211 in the first transmit chain 210 to cancel interference of the second transmit chain 220 with the first transmit chain 210.

[0076] In some embodiments, the amplitude adjusting module 320 may be an amplifier, an adjustable attenuator or any other suitable adjusting element. The exact and best implementation depends on actual gain in the circuit blocks and antenna isolation.

[0077] Reference is now made to Fig. 4, which shows an example circuit 400 for self-interference cancellation. The example circuit 400 may be a detailed implementation of the example circuit 300.

[0078] As illustrated in Fig. 4, a baseband and transceiver circuit are connected to the input terminal 215 of the PA 211 of the first transmit chain 210 via a first combiner and connected to theinput terminal 225 of the PA 221 of the second transmit chain 220 via a second combiner. The transmitter circuitry may further comprise a feedback receiver 440 connected to the coupler 213 of the first transmit chain 210 for DPD and / or antenna impedance tuning, and / or a feedback receiver 450 connected to the coupler 223 of the second transmit chain 220 for DPD and / or antenna impedance tuning. Legacy DPD functionality and antenna tuning may be performed in the feedback loop through the coupler 223, a selective switch 470 and the feedback receiver 450 for the second transmit chain. Similarly, for the first transmit chain, legacy DPD functionality and antenna tuning may be performed in the feedback loop through the coupler 213, a selective switch and the feedback receiver 440. In some embodiments, the UE may further comprise one or more receive chains 460.

[0079] In some embodiments, a baseband equivalent of the interference signal observed at the output terminal of the second transmit chain 220 due to the signal transmitted by the first transmit chain 210 may be given by Cf221Cf2223C^2228C213* gPA211 * S2BB= <zce7^cS2BBwhere acand (pcdenotes amplitude and phase of Cf221Cf2223C^2228C213*,gP.4211 respectively; C-j denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), the PA 221 (PA221), the second antenna 228 (A228), the coupler 213 (C213) etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; ^P / 1211 denotes the complex baseband transfer function of the PA211 and corresponding DAC, mixer, etc. in the transmit chain; S2BBdenotes a baseband aggressor signal (i.e. a signal at the input terminal 215 of the PA 211). Similarly, a baseband equivalent of an output signal of the interference cancellation circuit 230 is given byS2BB= aFej(l> FS2BB, where aFand <pFdenotes amplitude and phase ofrespectively; <z230and < >230denotes a tuning amplitude and phase of the interference cancellation circuit 230 respectively; gP.4211 denotes the complex baseband transfer function of the PA 211 and corresponding DAC, mixer, etc. in the transmit chain.

[0080] To mitigate the interference, an input signal of the interference cancellation circuit 230 need to be tuned such that a feedback signal aFe(> FgPA221 S2BBis (substantially) equal to a negative of <zce7^cS2BBand in such away, the effect of the interference may be cancelled out.

[0081] In Fig. 4, an example power level plan is provided for a case in which the first transmit chain 210 is the aggressor transmit chain and the second transmit chain 220 is the victim transmit chain. As illustrated in Fig. 4, an output power of the PA 211 (Pol) is 23 dBm, an output power of the PA 221 of the second transmit chain 220 (Po2) is 13 dBm, antenna isolation is 10 dB, gain of the PA 221 is 30 dB, loss of the second combiner is 3dB. Therefore, a power level of theinterference signal of the first transmit chain 210 at the output terminal of the second transmit chain 220 is determined as:Pol - antenna isolation = 13 dBm.In order to cancel the interference, the interference cancellation circuit 230 need to feedback a phase rotated version of the interference signal with a power level of 13 dBm. This in turn means that a power level at the output terminal of the interference cancellation circuit 230 should be:13 dBm - (gain in the PA 221 and the second combiner)= 13 dBm - (30 dB - 3dB) = 13 dBm - 27 dB = -14 dBm.

[0082] On the other hand, as the loss of the coupler 213 can be 20 dB, a power level of the input terminal of the interference cancellation circuit 230 is:Pol - 20 dB = 23 dBm - 20 dB = 3 dBm.This in turn result in an allowed loss for the interference cancellation circuit 230 of:3 dBm - (-14 dBm) = 17 dB.The numbers above that illustrates this are more or less worst case although a “power in balance” at the output terminal of the first transmit chain 210 and the output terminal of the second transmit chain 220 of 20 dB is still supported since it result in 7 dB loss for the interference cancellation circuit 230.

[0083] In some embodiments, since quite high loss is allowed in the interference cancellation circuit 230, the interference cancellation circuit 230 may be implemented by use of passive circuitry, which may save power and improve efficiency of the circuit.

[0084] In some embodiments, at least one of the following components may be implemented in digital domain: the interference cancellation circuit 230, the first combiner, the second combiner, the first selective switch 330, or the second selective switch 340. In this way, it may improve integration of the circuit.

[0085] Continuous cancellation is possible by use of the example circuit 400, and sequential estimation of transfer functions is not required.

[0086] Reference is now made to Fig. 5, which shows an example circuit 500 for self-interference cancellation. The example circuit 500 illustrates a digital implementation of the interference cancellation circuit 230.

[0087] As illustrated in Fig. 5, the interference cancellation circuit 230 may comprise a first feedback receiver 411, a second feedback receiver 421 and a control circuit 430. In someembodiments, the first feedback receiver 411 may be configured to receive the output signal in the aggressor transmit chain, the second feedback receiver 421 may be configured to receive an output signal of the victim transmit chain, and the control circuit 430 may be configured to tune an output signal of the first feedback receiver 411 and combine the tuned output signal of the first feedback receiver 411 with an output signal of the second feedback receiver 421. For example, the output signal of the first feedback receiver 411 may be tuned to be equal to the interference signal, and the control circuit 430 may be configured to subtract the tuned output signal of the first feedback receiver 411 from the output signal of the second feedback receiver 421. For another example, the output signal of the first feedback receiver 411 may be tuned to be negative of the interference signal, and the control circuit 430 may be configured to add the tuned output signal of the first feedback receiver 411 with the output signal of the second feedback receiver 421.

[0088] Reference is next made to Fig. 6, which shows an example circuit 600 for self-interference cancellation. The example circuit 600 may be a detailed implementation of the example circuit 200.

[0089] As illustrated in Fig. 6, the interference cancellation circuit 230 may comprise a first subcircuit 510 and a second sub-circuit 520 and each of the first sub-circuit 510 and the second subcircuit 520 may comprise the first feedback receiver 410, the second feedback receiver 420, and the control circuit 430 of their own. The first sub-circuit 510 may be configured to cancel interference of the second transmit chain 220 with the first transmit chain 210. The second subcircuit 520 may be configured to cancel interference of the first transmit chain 210 with the second transmit chain 220.

[0090] In some embodiments, two input terminals of the first sub-circuit 510 are respectively connected to two ports of the couplers. In other words, the two input terminals of the first subcircuit 510 are respectively connected to the port of the forward coupling path and the port of the reverse coupling path of the couplers 213 and 223.

[0091] As shown in Fig. 7, the coupler 213 may be seen as a 4-port network, and a S-parameter matrix of the coupler 213 is of size 4 x 4. The coupler 213 comprises four ports, Port 1, Port 2, Port 3, and Port 4. A path from the Port 1 to the Port 3 may be referred to as a forward coupling path that couples to a signal coming from the Port 1 to the Port 3. A path from the Port 1 to the Port may be referred to as a reverse coupling path that couples to a signal coming from the Port 1 to the Port 4.

[0092] The Port 1 is connected to the output terminal 217 of the PA 211, and the Port 2 is connected to the output terminal 219 of the first transmit chain 210, and the Port 3 is connected toan input terminal of the second feedback receiver 420 of the first sub-circuit 510, and the Port 4 is connected to an input terminal of the first feedback receiver 410 of the first sub-circuit 510. In other words, in Fig. 6, the second feedback receiver 420 of the first sub-circuit 510 is connected to a forward coupling path, and the first feedback receiver 410 of the first sub-circuit 510 is connected to a reverse coupling path.

[0093] Similarly, the coupler 223 may also be seen as a 4-port network including four ports, Port 1, Port 2, Port 3, Port 4. The Port 1 is connected to the output terminal 227 of the PA 221, the Port 2 is connected to the output terminal 229 of the second transmit chain 220). The Port 3 is connected to an input terminal of the second feedback receiver 420 of the second sub-circuit 520, and a Port 4 is connected to an input terminal of the first feedback receiver 410 of the second subcircuit 520. In Fig. 6, the second feedback receiver 420 of the second sub-circuit 520 is connected to a forward coupling path, and the first feedback receiver 410 of the first sub-circuit 520 is connected to a reverse coupling path.

[0094] In some embodiments, the first feedback receiver 410 receives the interference signal coupled on the output terminal of the victim transmit chain through the coupler of the victim transmit chain.

[0095] The first feedback receiver 410 of the first sub-circuit 510 also has an output terminal connected to the control circuit 430 of the first sub-circuit 510. The second feedback receiver 420 of the first sub-circuit 510 has an output terminal connected to the control circuit 430 of the first sub-circuit 510. The control circuit 430 of the first sub-circuit 510 has an output terminal connected to the input terminal 215 of the PA 211 in the first transmit chain 210.

[0096] Similarly, the first feedback receiver 410 of the second sub-circuit 520 has an output terminal connected to the control circuit 430 of the second sub-circuit 520. The second feedback receiver 420 of the second sub-circuit 520 has an output terminal connected to the control circuit 430 of the second sub-circuit 520. The control circuit 430 of the second sub-circuit 520 has an output terminal connected to the input terminal 225 of the PA 221 in the second transmit chain 220.

[0097] In some embodiments, the output terminal of the control circuit 430 of the first sub-circuit 510 is connected to the input terminal 215 of the PA 211 via a first modulator 610. The output terminal of the control circuit 430 of the second sub-circuit 520 is connected to the input terminal 225 of the PA 221 via a second modulator 620.

[0098] In some embodiments, the first modulator 610 may be alternatively included in the control circuit 430 of the first sub-circuit 510, and / or the second modulator 620 may be alternatively included in the control circuit 430 of the second sub-circuit 520.

[0099] With the implementation of the example circuit 600, the first feedback receiver 410 and the second feedback receiver 420 of each sub-circuit may be fed back to a same transceiver which is likely to be in the same physical location in practical device.

[0100] In some embodiments, the second feedback receiver 420 may reuse a receiver of unused (during UL) receive chain by a RF switch, so that no additional receiver is needed. It is quite feasible for TDD systems, since in practical implementations for handheld devices there are likely more receive chains than transmit chains. Current implementations may be (1 UL and 4 DL) & (2 UL and 4 DL). In the near future (2 UL and 8 DL) may be applied.

[0101] The interference signal may be coupled in the second antenna 228 from the first antenna 218 and further propagate through the coupler 223 and distorts the PA221’s output signal. The PA 221’s output signal is fed back into a DPD loop through the second feedback receiver 420 of the second sub-circuit 520 and propagates towards the second antenna 228 through the coupler 223)). The interference signal coupled in the second antenna 228 from the first antenna 218, i.e., y(C223, A228), may be written as:where C- denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223, the PA 221, the second antenna 228, etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; S2 denotes a baseband equivalent of a true RF signal transmitted by the first antenna 218.

[0102] The coupling coefficientcaptures the coupling effect from the first antenna 218 along with the effect of hand grip. The signals ‘ST and ‘S2’ are the baseband equivalent of the true RF signals transmitted by the first antenna 218 and second antenna 228, respectively, and may be written asS1 = C21C223* gPA221 * S1BB...eq(2)where C- denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), the coupler 213 (C213) etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; gP.4221 (or gP.4211) respectively denotes the complex baseband transfer function of the PA 221 (or PA 211) and corresponding DAC, mixer, etc. in the transmit chain; and S1BB(or S2BB) respectively denotes desired baseband signal transmitted by the PA 221 (or PA 211).

[0103] The coupling coefficients of the antennas are the function of S-parameters of the corresponding antenna which can be represented as a two-port network as shown in Fig. 8. As illustrated in Fig. 8, the antenna may have two ports, Port 1, and port 2 and the S-parameter matrix of the antenna is of size 2 x 2.

[0104] The signal coupled by the coupler 223 on Port 3 (towards the second feedback receiver 420 of the second sub-circuit 520) and Port 4 (towards the first feedback receiver 410 of the second sub-circuit 520) may be written asOn port 3:as Port 1 and Port 3 are coupled ports whereas Port 2 and Port 3 are isolated ports, where C-denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; y(C223, PA221~) denotes an input signal on the Port 1; y(C223, A228~) denotes an input signal on the Port 2. Andy(C223, PA221) = #PA221 * S1BB+ Cf221* y(PA221, C223),... eq(6)as y(PA221, C223) = Cf^23* y(C223, A228) and we have used the results in eq (1) and eq (3), where C- denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), the coupler 213 (C213), the PA 221 (PA221), the PA 211 (PA211), the second antenna 228 (A228), etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; y(PA221, C223) denotes an output signal on the Port 1 of the coupler 223; y(C223, A2) denotes an input signal on the Port 2 of the coupler 223; gP.4211 denotes the complex baseband transfer function of the PA 211 and corresponding DAC, mixer, etc. in the transmit chain; gP / 1221 denotes the complex baseband transfer function of the PA221 and corresponding DAC, mixer, etc. in the transmit chain; S2BBdenotes a baseband aggressor signal (i.e. a signal at the input terminal 215 of the PA 211); S21ssdenotes a baseband victim signal.

[0105] From eq (5) and eq (7), the following equation may be gotteny( / ?x420, C223) « C3c223* ^P4221 * S1BB+ C3c1223C2221Cf2223C(12228C2C213* 0P 211 * S2BB...eq(8)where C- denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), the coupler 213 (C213), the PA 221 (PA221), the PA 211 (PA211), the second antenna 228 (A228), etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; y(Rx420, C223) denotes an input signal on the input terminal of the second feedback receiver 420; y(C223, A228) denotes a input signal on the Port 2 of the coupler 223; g 4211 denotes the complex baseband transfer function of the PA 211 and corresponding DAC, mixer, etc. in the transmit chain; gP.4221 denotes the complex baseband transfer function of the PA 221 and corresponding DAC, mixer, etc. in the transmit chain; S2BBdenotes a baseband aggressor signal (i.e. a signal at the input terminal 215 of the PA 211); S21ssdenotes a baseband victim signal.

[0106] Therefore, the baseband signal received at the output of Rx420 can be written as yBB( / ?%420) = gRx420 * y( / ?%420, C223) = a^Slgg + <z12S2BB... eq(9)gP.4211 * g / ?x420).where C- denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), the coupler 213 (C213), the PA 221 (PA221), the PA 211 (PA211), the second antenna 228 (A228), etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; y(Rx420, C223) denotes an input signal on the input terminal of the second feedback receiver 420; yBB(Rx420) denotes an output signal of the second feedback receiver 420; gP.4211 denotes the complex baseband transfer function of the PA 211 and corresponding DAC, mixer, etc. in the transmit chain; gP.4221 denotes the complex baseband transfer function of the PA 221 and corresponding DAC, mixer, etc. in the transmit chain; g / ?x420 denotes the complex baseband transfer function of the feedback receiver 420; S2BBdenotes a baseband aggressor signal (i.e. a signal at the input terminal 215 of the PA 211); S21ssdenotes a baseband victim signal.On port 4:as Port 2 and Port 4 are coupled ports whereas Port 1 and Port 4 are isolated ports, where C-denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; y( / ?x410, C223) denotes an input signal on the input terminal of the first feedback receiver 410; y C223, A22&) denotes an input signal on the Port 2 of the coupler 223.

[0107] Using the results in eq (1) and eq (3), eq (11) can be written as

[0108] Therefore, the baseband signal received at the output of Rx410 can be written as yss( / ?x410) = gRx410 * y( / ?x410, C223) = a22S2BB...eq(13)

[0109] From eq(9) and eq(13), a system of linear equations is formed with coefficientsan>ai2> and a22, which may be represented in a matrix form as:... eq(14)

[0110] The objective in eq(14) is to suppress or mitigate the impact of a12S2BB" term in y( / ?x420) signal which is then fed back for calculating the weights of digital pre-distortion. In case the impact of “a12S2BB” term in y( / ?x420) signal is not mitigated, the weights of DPD will be incorrectly computed and will subsequently degrade the DPD performance.

[0111] As yss( / ?x420) and yss( / ?x410) are the baseband signals observed at the output of Rx420 and Rx410 respectively, and S1BBand S2BBare the baseband signals transmitted by the second transmit chain 220 and the first transmit chain 210 respectively, these baseband signals are known and we need to calculate the coefficients a11(a12, and a22for the interference suppression.

[0112] Transmitting two baseband symbols sequentially and receiving the corresponding baseband signals, we get... eq(15)

[0113] Using the identity vec(ABC) = (CT.4) vec B), eq (15) may be rewritten asfrom which the coefficients a1, a12, and a22may be obtained aswhere the identity (4 0 B)1= (410 Bx) is used.

[0114] Once the coefficients a1, a12, and a22are estimated, the term <z12S2BBmay be directly subtracted from the yss( / ?%420) to remove the effect of the coupled contribution of the aggressor going into the DPD loop.

[0115] It is to be understood that the above procedure works based on the assumption that the SIBBI BBImatrix of baseband symbols is invertible.S1-BB2 BB2.

[0116] In some embodiments, the coefficients a1, a12, and a22need to be periodically estimated as the effect of hand-grip will change over time and will impact the coupling factor13which in turn will change the coefficients a1, <z12, and a22.

[0117] The above procedure can estimate the coefficients a1, a12, and a22using any data / reference symbols transmitted in the uplink which satisfies the above assumption. Therefore, the procedure does not require any special measurement gaps to estimate the coefficients allta12,and a22.

[0118] Reference is now made to Fig. 9, which shows an example circuit 900 for self-interference cancellation. The example circuit 900 may be a detailed implementation of the example circuit 200.

[0119] As illustrated in Fig. 9, the interference cancellation circuit 230 may comprise a first subcircuit 510 and a second sub-circuit 520, and the first sub-circuit 510 and the second sub-circuit 520 may share the same first feedback receiver 410 and the same control circuit 430 but have the second feedback receiver 420 of their own.

[0120] The second feedback receiver 420 of the first sub-circuit 510 has an input terminal connected to the Port 3 of the coupler 213 of the first transmit chain 210 and an output terminal connected to the control circuit 430. The second feedback receiver 420 of the second sub-circuit 520 has an input terminal connected to the Port 3 of the coupler 223 of the second transmit chain 220 and an output terminal connected to the control circuit 430. The control circuit 430 has afirst output terminal connected to the input terminal 215 of the PA 211 in the first transmit chain 210 and a second output terminal connected to the input terminal 225 of the PA 221 in the second transmit chain 220.

[0121] As shown in Fig. 9, the first feedback receiver 410 has an input terminal connected to the Port 4 of the coupler 213 of the first transmit chain 210 or the Port 4 of the coupler 223 of the second transmit chain 220 via a third selective switch 710, and an output terminal is connected to the control circuit 430. Alternatively, as shown in Fig. 10, the input terminal of the first feedback receiver 410 and the input terminal of the second feedback receiver 420 of the first sub-circuit 510 is connected to the Port 3 of the coupler 213 via a first power splitter 930. The input terminal of the first feedback receiver 410 and the input terminal of the second feedback receiver 420 of the second sub-circuit 520 is connected to the Port 3 of the coupler 223 via a second power splitter (940).

[0122] In a case that the second transmit chain 220 is the aggressor transmit chain and the first transmit chain 210 is the victim transmit chain, the third selective switch 710 may be switched to connect with the Port 3 of the coupler 223 of the second transmit chain 220. In some embodiments, the first feedback receiver 410 receives the interference signal coupled on the output terminal 229 of the second transmit chain 220 through the coupler 223.

[0123] In a case that the first transmit chain 210 is the aggressor transmit chain and the second transmit chain 220 is the victim transmit chain, the third selective switch 710 may be switched to connect with the Port 3 of the coupler 213 of the first transmit chain 210. In some embodiments, the first feedback receiver 410 receives the interference signal coupled on the output terminal 219 of the first transmit chain 210 through the coupler 213.

[0124] By means of switch 710, the first feedback receiver 410 may be shared by the first and second sub-circuits 510 and 520. Thus, with implementation of the example circuit 900, only one feedback receiver for interference cancellation is needed, which may improve efficiency of the circuit, reduce the size of circuit, and cost of the circuit.

[0125] Reference is now made to Fig. 10, which shows an example circuit 1000 for selfinterference cancellation. The example circuit 1000 may be a detailed implementation of the example circuit 200.

[0126] As illustrated in Fig. 10, the interference cancellation circuit 230 may comprise a first sub-circuit 510 and a second sub-circuit 520 and the first sub-circuit 510 and the second sub-circuit 520 may share the same first feedback receiver 410 and the same control circuit 430 but have the second feedback receiver 420 of their own.

[0127] The second feedback receiver 420 of the first sub-circuit 510 has an input terminal connected to the Port 3 or the Port 4 of the coupler 213 of the first transmit chain 210 via a fourth switch 910 and an output terminal connected to the control circuit 430. The fourth switch 910 is switched to connect with the Port 3 of the coupler 213 for DPD or DL reception, and the fourth switch 910 is switched to connect with the Port 4 of the coupler 213 for antenna impedance tuning.

[0128] The second feedback receiver 420 of the second sub-circuit 520 has an input terminal connected to the Port 3 or the Port 4 of the coupler 223 of the second transmit chain 220 via a fifth switch 920 and an output terminal connected to the control circuit 430. The fifth switch 920 may be switched to connect with the Port 3 of the coupler 223 for DPD or DL reception, and the fifth switch 920 may be switched to connect with the Port 4 of the coupler 223 for antenna impedance tuning.

[0129] The first feedback receiver 410 has an input terminal connected to the Port 3 of the coupler 213 of the first transmit chain 210 or the Port 3 of the coupler 223 of the second transmit chain 220 via a third selective switch 710, and an output terminal is connected to the control circuit 430.

[0130] In a case that the first transmit chain 210 is the aggressor transmit chain and the second transmit chain 220 is the victim transmit chain, the third selective switch 710 may be switched to connect with the Port 3 of the coupler 213 of the first transmit chain 210.

[0131] In a case that the second transmit chain 220 is the aggressor transmit chain and the first transmit chain 210 is the victim transmit chain, the third selective switch 710 may be switched to connect with the Port 3 of the coupler 223 of the second transmit chain 220.

[0132] The control circuit 430 has a first output terminal connected to the input terminal 215 of the PA 211 in the first transmit chain 210 and a second output terminal connected to the input terminal 225 of the PA 221 in the second transmit chain 220.

[0133] A baseband equivalent of the interference signal present at the output terminal 227 of the PA 221 is given by Cf221Cf2223C^2228C213* gPA211 * S2BB= <zce7^cS2BB, where acand < >cdenotes, respectively, an amplitude and phase of Cf221Cf2223C^2228C213*,gP.4211; C-j denotes a coupling coefficient of a RF element ‘X’, e.g., the coupler 223 (C223), the PA 221 (PA221), the second antenna 228 (A228), the coupler 213 (C213) etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; ^P / 1211 denotes the complex baseband transfer function of the PA211 and corresponding DAC, mixer, etc. in the transmit chain; S2BBdenotes a baseband aggressor signal (i.e. a signal at the input terminal 215 of the PA 211).

[0134] And a baseband equivalent of an output signal of the first feedback receiver 410 is given by C2930CIC3213* gP 1211 * gRx410 * S2BB= ape^FS2BB, where apand c / )Fdenotes, respectively, an amplitude and phase of C32S930C13C213* g 4211 * g / ?x410 C-j denotes a coupling coefficient of a RF element ‘X’, e.g., the switch 930 (S930), the coupler 213 (C213) etc., when an input signal is applied at a Port j and a coupled contribution of the input signal is observed as an output at a Port i; g 4211 denotes the complex baseband transfer function of the PA 211 and corresponding DAC, mixer, etc. in the transmit chain; g / ?x410 denotes the complex baseband transfer function of the first feedback receiver 410; S2BBdenotes a baseband aggressor signal (i.e. a signal at the input terminal 215 of the PA 211).

[0135] To mitigate the coupled contribution of the aggressor signal at the output of the PA 221, the feedback signal aFe(> FgPA221 S2BBneeds to be multiplied with the optimal complex numbersuch that the product* apeJ^FgPA221 S2BBis (substantially) equal to the negative of <zce7^cS2BBand hence the effect of coupled contribution of the aggressor signal is cancelled out. This is mathematically shown below.

[0136] The example circuit 1000 may be seen as a digital implementation of the example circuit 400. A structure of the example circuit 1000 is similar to the example circuit 900, as only one feedback receiver for interference cancellation is needed. It may improve efficiency of the circuit.

[0137] Reference is now made to Fig. 11, which shows an example circuit 1100 for selfinterference cancellation. The example circuit 1100 may be a detailed implementation of the example circuit 200.

[0138] The interference cancellation circuit 230 comprises a first feedback receiver 410 configured to receive one of the output signal of the aggressor transmit chain or the output signal of the victim transmit chain, a second feedback receiver 420 configured to receive another of the output signal of the aggressor transmit chain or an output signal of the victim transmit chain, and a control circuit 430 connected to the first feedback receiver 410 and the second feedback receiver 420 and configured to tune an output signal of the aggressor transmit chain and combine the tuned output signal of the aggressor transmit chain with an output signal of the victim transmit chain.

[0139] In some embodiments, the first feedback receiver 410 has an input terminal connected tothe Port 4 of the coupler 223 of the second transmit chain 220 or the Port 3 of the coupler 213 of the first transmit chain 210 via a sixth selective switch (1010), and an output terminal connected to the control circuit 430. The second feedback receiver 420 has an input terminal connected to the Port 3 of the coupler 223 of the second transmit chain 220 or the Port 4 of the coupler 213 of the first transmit chain 210 via a seventh selective switch (1020), and an output terminal connected to the control circuit 430. The control circuit 430 has a first output terminal connected to the input terminal 215 of the PA 211 in the first transmit chain 210, and a second output terminal connected to the input terminal 225 of the PA 221 in the second transmit chain 220.

[0140] In some embodiments, the Port 4 of the coupler 223 is connected to the sixth selective switch 1010 or a first resistor via an eighth selective switch. The Port 4 of the coupler 213 is connected to the seventh selective switch 1020 or a second resistor via a ninth selective switch.

[0141] In a case that the first transmit chain 210 is the aggressor transmit chain and the second transmit chain 220 is the victim transmit chain, the sixth selective switch 1010 may firstly be switched to connect with the coupler 213 of the first transmit chain 210 for DPD, and then may be switched to connect with the coupler 223 of the second transmit chain 220, the seventh selective switch 1020 may be switched to connect with the coupler 223, the eighth selective switch 1040 may be switched to connect with the first resistor, and the ninth selective switch 1050 may be switched to connect with the sixth selective switch 1010, so that the interference cancellation circuit 230 may feed an output signal of the first transmit chain 210 back to the input terminal 225 of the PA 221 in the second transmit chain 220 to cancel interference of the first transmit chain 210 with the second transmit chain 220. That is, transfer functions of DPD loop and TX SIC are estimated sequentially.

[0142] In a case that the second transmit chain 220 is the aggressor transmit chain and the first transmit chain 210 is the victim transmit chain, the sixth selective switch 1010 may firstly be switched to connect with the coupler 223 of the second transmit chain 220 for DPD, and then may be switched to connect with the coupler 213 of the first transmit chain 210, the seventh selective switch 1020 may be switched to connect with the coupler 213, the eighth selective switch 1040 may be switched to connect with the seventh selective switch (1020), and the ninth selective switch 1050 may be switched to connect with the second resistor, so that the interference cancellation circuit 230 may feed an output signal of the second transmit chain 220 back to the input terminal 215 of the PA 211 in the first transmit chain 210 to cancel interference of the second transmit chain 220 with the first transmit chain 210. That is, transfer functions of DPD loop and TX SIC are estimated sequentially.

[0143] A mathematical formulation of the example circuit 1100 is similar to the example circuit600.

[0144] Eq (20) is very similar to eq (14) and hence the algorithm / procedure described after eq(14) till eq(18) can be used to estimate the coefficients.

[0145] Once the coefficients allta12, and a22are estimated, the term <z12S2BBcan be directly subtracted from the yss( / ?x420) to remove the effect of the coupled contribution of the aggressor going into the DPD loop.

[0146] With the implementation of the example circuit 1100, only 2 feedback receivers are needed. Only 2 RF switches are added compared with current state of art implementations as of today. It may improve efficiency of the circuit.System Simulation Result

[0147] A system simulation result is provided to illustrate the technical effect of the present disclosure. Fig. 12 illustrates an example simulation model according to embodiments of the present disclosure. The simulation model comprises two transmit chain, each comprise a PA and a coupler connected serially.

[0148] A power level used in the simulation set-up was set so low that non-linear effects caused by the PA’s was so low that it does not affect the system performance. The simulation results shown below was obtained by first estimating / calculating a required amplitude setting for the attenuator and next sweep / tune the phase shifter and thereby find an optimum phase shifter setting. An outcome of this is shown on Fig.13 & Table 1.Table 1| 335 | 27 | 45 |

[0149] The attenuator was tuned next and SNR of 41 dB was achieved for stream 1, as shown in Table 2.Table 2

[0150] It is an improvement of 24 dB compared with the setting where TXSIC was turned off by setting the attenuator to 100 dB, SNR Stream 1 = 17 dB, as shown in Table 3.Table 3

[0151] The result shown on Fig. 13 implies that the resolution of the phase tuning does not require a very fine resolution or accuracy of the phase tuning to achieve a significant improvement. SNR for the stream 2 was as expected fixed at 45 dB in all the simulation results which is expected since the stream 2 is an aggressor signal and a power level of the stream 1 is so low that it cannot affect performance of the stream 2.Example Method

[0152] Fig. 14 shows a flowchart of an example method 1400 implemented at a UE apparatus in accordance with some embodiments of the present disclosure. The UE apparatus comprises a first transmit chain 210, a second transmit chain 220, and an interference cancellation circuit 230.

[0153] At block 1410, the interference cancellation circuit 230 obtains an output signal of an aggressor transmit chain. At block 1420, the interference cancellation circuit 230 tunes the output signal in accordance with an interference signal of the aggressor transmit chain at an output terminal of the victim transmit chain. At block 1430, the interference cancellation circuit 230 outputs the tuned output signal to an input terminal of a power amplifier (PA) in a victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain 210 and the second transmit chain 220 causing the interference, and the victim transmit chain is another one of the first transmit chain 210 and the second transmit chain 220 subject to the interference.

[0154] In some embodiments, the output signal is tuned to have substantially same amplitude and approximately 180 degrees out of phase with the interference signal.

[0155] In some embodiments, an apparatus capable of performing any of the method 1400 (for example, the terminal device 120) may comprise means for performing the respective steps of the method 1400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0156] In some embodiments, the apparatus comprises: means for inputting an output signal of an aggressor transmit chain; means for tuning the output signal in accordance with an interference signal of the aggressor transmit chain at an output terminal of the victim transmit chain; and means for outputting the tuned output signal to an input terminal of a power amplifier (PA) in a victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain 210 and the second transmit chain 220 causing the interference, and the victim transmit chain is another one of the first transmit chain 210 and the second transmit chain 220 subject to the interference.

[0157] In some embodiments, the output signal is tuned to have substantially same amplitude and approximately 180 degrees out of phase with the interference signal.

[0158] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 800. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0159] FIG. 15 is a simplified block diagram of a device 1500 that is suitable for implementing embodiments of the present disclosure. The device 1500 may be provided to implement the communication device, for example the terminal device 120 or the network device 110 as shown in Fig. 1A. As shown, the device 1500 includes one or more processors 1510, one or more memories 1520 coupled to the processor 1510, and one or more communication modules 1540 coupled to the processor 1510.

[0160] The communication module 1540 is for bidirectional communications. The communication module 1540 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

[0161] The processor 1510 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processorarchitecture, as non-limiting examples. The device 1500 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0162] The memory 1520 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a read only memory (ROM) 1524, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 1522 and other volatile memories that will not last in the powerdown duration.

[0163] A computer program 1530 includes computer executable instructions that are executed by the associated processor 1510. The program 1530 may be stored in the ROM 1524. The processor 1510 may perform any suitable actions and processing by loading the program 1530 into the RAM 1522.

[0164] The communication module 1540 is for bidirectional communications. The communication module 1540 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

[0165] The embodiments of the present disclosure may be implemented by means of the program 1530 so that the device 1500 may perform any process of the disclosure as discussed with reference to Figs. 2 to 14. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0166] In some embodiments, the program 1530 may be tangibly contained in a computer readable medium which may be included in the device 1500 (such as in the memory 1520) or other storage devices that are accessible by the device 1500. The device 1500 may load the program 1530 from the computer readable medium to the RAM 1522 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. Fig. 16 shows an example of the computer readable medium 1600 in form of CD or DVD. The computer readable medium has the program 1530 stored thereon.

[0167] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware orsoftware which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0168] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method 1400 as described above with reference to Figs. 2-14. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machineexecutable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0169] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0170] In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0171] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0172] Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

[0173] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A user equipment (UE) apparatus, comprising:a first transmit chain comprising a power amplifier (PA) and a coupler connected serially, a second transmit chain comprising a PA and a coupler connected serially, andan interference cancellation circuit configured to feed an output signal of an aggressor transmit chain back to an input terminal of a PA in a victim transmit chain to cancel interference of the aggressor transmit chain with the victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain and the second transmit chain causing the interference, and the victim transmit chain is another one of the first transmit chain and the second transmit chain subject to the interference.

2. The UE apparatus of claim 1, wherein the interference cancellation circuit is further configured to tune the output signal of the aggressor transmit chain in accordance with an interference signal of the aggressor transmit chain at an output terminal of the victim transmit chain.

3. The UE apparatus of claim 2, wherein the output signal of the aggressor transmit chain is tuned to have substantially same amplitude and approximately 180 degrees out of phase with the interference signal of the aggressor transmit chain at the output terminal of the victim transmit chain.

4. The UE apparatus of any of claims 1 to 3, wherein the interference cancellation circuit comprises a phase rotating module and an amplitude adjusting module connected serially, and an input terminal of the interference cancellation circuit is connected to the coupler of the first transmit chain or the coupler of the second transmit chain via a first selective switch, an output terminal of the interference cancellation circuit is connected to an input terminal of the PA in the second transmit chain or an input terminal of the PAin the first transmit chain via a second selective switch.

5. The UE apparatus of claim 1, wherein the interference cancellation circuit comprises: a first feedback receiver configured to receive the output signal in the aggressor transmit chain,a second feedback receiver configured to receive an output signal of the victim transmit chain, anda control circuit configured to tune an output signal of the first feedback receiver and combine the tuned output signal of the first feedback receiver with an output signal of the second feedback receiver.

6. The UE apparatus of claim 1, wherein the interference cancellation circuit comprises a first sub-circuit and a second sub-circuit, wherein each of the first sub-circuit and the second subcircuit comprises the first feedback receiver, the second feedback receiver, and the control circuit of their own, wherein the first sub-circuit is configured to cancel interference of the second transmit chain with the first transmit chain, the second sub-circuit is configured to cancel interference of the first transmit chain with the second transmit chain.

7. The UE apparatus of claim 6, wherein the first feedback receiver of the first sub-circuit has an input terminal connected to a reverse coupling path of the coupler of the first transmit chain and an output terminal connected to the control circuit of the first sub-circuit,wherein the second feedback receiver of the first sub-circuit has an input terminal connected to a forward coupling path of the coupler of the first transmit chain and an output terminal connected to the control circuit of the first sub-circuit,wherein the control circuit of the first sub-circuit has an output terminal connected to the input terminal of the PA in the first transmit chain,wherein the first feedback receiver of the second sub-circuit has an input terminal connected to a reverse coupling path of the coupler of the second transmit chain and an output terminal connected to the control circuit of the second sub-circuit,wherein the second feedback receiver of the second sub-circuit has an input terminal connected to a forward coupling path of the coupler of the second transmit chain, and an output terminal connected to the control circuit of the second sub-circuit, andwherein the control circuit of the second sub-circuit has an output terminal connected to the input terminal of the PA in the second transmit chain.

8. The UE apparatus of claim 1, wherein the interference cancellation circuit comprises a first sub-circuit and a second sub-circuit, and the first sub-circuit and the second sub-circuit share the same first feedback receiver and the same control circuit and have the second feedback receiver of their own,wherein the second feedback receiver of the first sub-circuit has an input terminal connected to a forwardcoupling path of the coupler of the first transmit chain and an output terminal connected to the control circuit,wherein the second feedback receiver of the second sub-circuit has an input terminal connected to a forward coupling path of the coupler of the second transmit chain and an output terminal connected to the control circuit,wherein the first feedback receiver has an input terminal connected to the coupler of the first transmit chain or the coupler of the second transmit chain via a third selective switch, and an output terminal is connected to the control circuit, andwherein the control circuit has a first output terminal connected to the input terminal of the PA in the first transmit chain and a second output terminal connected to the input terminal of the PA in the second transmit chain.

9. The UE apparatus of claim 8, wherein the input terminal of the first feedback receiver is connected to a reverse coupling path of the coupler of the first transmit chain or a reverse coupling path of the coupler of the second transmit chain via the third selective switch.

10. The UE apparatus of claim 8, wherein the input terminal the first feedback receiver is connected to a forward coupling path of the coupler of the first transmit chain or a forward coupling path of the coupler of the second transmit chain via the third selective switch,wherein the input terminal of the second feedback receiver of the first sub-circuit is connected to a reverse coupling path or the forward coupling path of the coupler of the first transmit chain via a fourth switch,wherein the input terminal of the second feedback receiver of the second sub-circuit is connected to a reverse coupling path or the forward coupling of the coupler of the second transmit chain via a fifth switch, wherein the first port of the coupler of the second transmit chain is coupled with a port of the coupler connected to an output terminal of the second transmit chain, wherein the forward coupling path of the coupler of the first transmit chain is connected to the input terminal of the second feedback receiver of the first sub-circuit and the input terminal of the first feedback receiver via a first splitter, andwherein the forward coupling path of the coupler of the second transmit chain is connected to the input terminal of the second feedback receiver of the second sub-circuit and the input terminal of the first feedback receiver via a second splitter.

11. The UE apparatus of claim 1, wherein the interference cancellation circuit comprises: a first feedback receiver configured to receive one of the output signal of the aggressor transmit chain and the output signal of the victim transmit chain;a second feedback receiver configured to receive another of the output signal of theaggressor transmit chain and an output signal of the victim transmit chain, anda control circuit connected to the first feedback receiver and the second feedback receiver and configured to tune an output signal of the aggressor transmit chain and combine the tuned output signal of the aggressor transmit chain with an output signal of the victim transmit chain.

12. The UE apparatus of claim 11, wherein the first feedback receiver has an input terminal connected to a reverse coupling path of the coupler of the second transmit chain or a forward coupling path of the coupler of the first transmit chain via a sixth selective switch, and an output terminal connected to the control circuit,wherein the second feedback receiver has an input terminal connected to a forward coupling path of the coupler of the second transmit chain or a reverse coupling path of the coupler of the first transmit chain via a seventh selective switch, and an output terminal connected to the control circuit,wherein of the control circuit has a first output terminal connected to the input terminal of the PA in the first transmit chain, and a second output terminal connected to the input terminal of the PA in the second transmit chain.

13. A method implemented at a user equipment (UE), wherein the terminal device comprises a first transmit chain, a second transmit chain, and an interference cancellation circuit, the method comprising:obtaining, by the interference cancellation circuit, an output signal of an aggressor transmit chain;tuning, by the interference cancellation circuit, the output signal in accordance with an interference signal of the aggressor transmit chain at an output terminal of the victim transmit chain; andoutputting, by the interference cancellation circuit, the tuned output signal to an input terminal of a power amplifier (PA) in a victim transmit chain, wherein the aggressor transmit chain is one of the first transmit chain and the second transmit chain causing the interference, and the victim transmit chain is another one of the first transmit chain and the second transmit chain subject to the interference.

14. The method of claim 13, wherein the output signal is tuned to have substantially same amplitude and approximately 180 degrees out of phase with the interference signal.

15. A computer program comprising instructions which, when executed by an apparatus,cause the apparatus to perform the method of any of claims 13 to 14.

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