Radio receiver for full-duplex communication

Abstract

There is provided a radio receiver for full-duplex communication. The radio receiver comprises an input port for receiving a signal from an antenna. The radio receiver comprises a first signal path operatively connected to the input port for providing a positive polarity of a differential down-converted version of the received signal. The radio receiver comprises a second signal path operatively connected to the input port for providing a negative polarity of the differential down-converted version of the received signal. The radio receiver comprises a cancellation circuit operatively connected to the first signal path for injecting a cancellation current in the first signal path. The radio receiver comprises a Self-Interference-Signal control circuit configured to receive channel and cross-interference information and to control the cancellation circuit based on the received channel and cross-interference information.

Description

[0001] RADIO RECEIVER FOR FULL-DUPLEX COMMUNICATION

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to a radio receiver for full-duplex communication, and to a full-duplex transceiver comprising such a radio receiver.

[0004] BACKGROUND

[0005] In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed.

[0006] For example, in order to improve the spectral efficiency in congested parts of the frequency spectrum, there is an interest in radio circuits able to transmit (Tx) and receive (Rx) signals simultaneously and at the same frequency. This approach is referred to as Full-Duplex (FD) and allows to operate Uplink (UL) and Downlink (DL) on the same time-frequency resource. FD is compared to Time-Division Duplex (TDD) and Frequency-Division Duplex (FDD) in Fig. 1. In more detail, Fig. 1 shows time and frequency allocation for different duplexing schemes; Fig. 1(a) shows an example of TDD, Fig. 1(b) shows an example of FDD, and Fig. 1(c) shows an example of FD.

[0007] One challenge introduced by FD is self-interference, where a portion of the Tx signal is undesirably transmitted to the equipment’s own Rx circuitry. Self-interference can be mitigated, or even resolved, by means of isolation, i.e., by minimizing as much as possible the leakage from the Tx circuitry to the Rx circuitry, and by cancellation (i.e., by Self-Interference Cancellation; (SIC) where the leaking of the Tx signal is subtracted from the Rx signal. In a single-antenna Transceiver (TRx), isolation can, for example, be obtained by using a circulator at the antenna interface. Cancellation can be performed in the radio frequency (RF) domain, the analog domain, and in the baseband (BB) domain. In an antenna array, isolation can be introduced by connecting the Tx circuitry and the Rx circuitry to split antenna panels. Placing the panels further apart increases the isolation. In this example, the self-interference varies between the different Rx elements according to the steering angle. In an antenna array, the cancellation circuit should address both self-interference and cross-interference (i.e., coupling between the antennas). In some aspects, the complexity of the cancellation circuit grows quadratically with the number of antennas.

[0008] One advantage of performing SIC at the antenna interface is that the cancellation includes some of the Tx impairments, such as the Power Amplifier (PA) nonlinearities. Approaches have been implemented using passive or active balanced duplexers, and circulators. However, the sensitivity to antenna impedance, the inherent 3 dB Noise Figure (NF) degradation and the physical size of these networks remain limiting factors for integration. Considering these limitations, recent attempts at implementing a FD Rx attempts to combine both SIC and noise cancellation (NC).

[0009] In M. Essawy et al., "A Noise-Cancelling Self-Interference Canceller with +7 dBm Self-Interference Power Handling in o.i8p m CMOS,", 2021 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), Atlanta, GA, USA, 2021, pp. 95-98, doi: 10.1109 / RFIC51843.2021.9490418 is disclosed a dual-path NC and SIC. The distortion and noise added by the SIC circuit is sensed and also cancelled. A 2odB SI cancellation over a 50MHz bandwidth and 23dB cancellation for +idBm peak SI power while degrading the Rx NF by 3.8dB is claimed. However, the usability in antenna array is limited as cross-interference is not addressed.

[0010] In D. Murphy et al., "A Blocker-Tolerant, Noise-Cancelling Receiver Suitable for Wideband Wireless Applications," in IEEE Journal of Solid-State Circuits, vol. 47, no. 12, pp. 2943-2963, Dec. 2012, doi: 10.1109 / JSSC.2012.2217832 is introduced a NC- Rx consisting of a Main-Path sensing current and an Auxiliary-Path sensing voltage. The thermal noise on each path has an opposite sign and therefore, can be cancelled.

[0011] Hence, there is still a need for an FD radio receiver that is capable of performing Self- and Cross-Interference Cancellation, with a limited impact on the Rx noise.

[0012] SUMMARY

[0013] An object of embodiments herein is to address the above issues by providing an FD radio receiver that is capable of performing Self- and Cross-Interference Cancellation, with a limited impact on the Rx noise. A particular object is to provide an FD radio receiver that is tunable according to the level of cancellation required, to limit the impact on overall power consumption in a large antenna array.

[0014] According to a first aspect there is presented a radio receiver for full-duplex communication. The radio receiver comprises an input port for receiving a signal from an antenna. The radio receiver comprises a first signal path operatively connected to the input port for providing a positive polarity of a differential down- converted version of the received signal. The radio receiver comprises a second signal path operatively connected to the input port for providing a negative polarity of the differential down-converted version of the received signal. The radio receiver comprises a cancellation circuit operatively connected to the first signal path for injecting a cancellation current in the first signal path. The radio receiver comprises a Self-Interference-Signal control circuit configured to receive channel and crossinterference information and to control the cancellation circuit based on the received channel and cross-interference information.

[0015] According to a second aspect there is presented a full-duplex transceiver. The full- duplex transceiver comprises the radio receiver according to the first aspect.

[0016] Advantageously, this radio receiver and this transceiver are capable of performing Self- and Cross-Interference Cancellation, with a limited impact on the Rx noise.

[0017] Advantageously, this radio receiver and this transceiver are tunable according to the level of cancellation required, to limit the impact on overall power consumption in a large antenna array.

[0018] Advantageously, this radio receiver and this transceiver can use digital control of the cancellation to enable a tradeoff between power and complexity on the one hand and cancellation on the other hand.

[0019] Advantageously, this radio receiver and this transceiver can run in TDD without penalty on the performance.

[0020] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0023] Fig. 1 is a schematic diagram illustrating TDD, FDD, and FD according to examples;

[0024] Figs. 2, 3, 4, and 6 schematically illustrate radio receivers according to embodiments;

[0025] Fig. 5 shows simulation results according to embodiments;

[0026] Fig. 7 schematically illustrates radio transceivers according to embodiments; and

[0027] Fig. 8 schematically illustrates a double switch mixer according to an embodiment.

[0028] DETAILED DESCRIPTION

[0029] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

[0030] As noted above, there is still a need for an FD radio receiver that is capable of performing Self- and Cross-Interference Cancellation, with a limited impact on the Rx noise. A radio receiver that performs both noise and Interference cancellation is disclosed. The radio receiver has a first signal path and a second signal path providing noise cancellation. An additional current can be injected on the first signal path to perform (self-) interference cancellation. The noise introduced by the cancellation circuit can be suppressed, or even cancelled, using a second current source that utilizes the first signal path. The cancellation signal can be digitally controlled and set to cancel both self-interference and cross-interference (i.e., the coupling between the antennas). The proposed radio receiver is therefore compatible with an antenna array operating in FD. The SIC circuit can be turned off so that a full-duplex transceiver that comprises the radio receiver operates in a regular TDD fashion.

[0031] In particular, a radio receiver 2ooa:2ooe for full-duplex communication as illustrated in Figs. 2, 3, 4, and 6 adapted to perform both noise cancellation and interference cancellation will now be disclosed. The radio receiver 2ooa:2ooe comprises an input port for receiving a signal from an antenna. The radio receiver 200a: 2ooe further comprises a first signal path operatively connected to the input port for providing a positive polarity of a differential down-converted version of the received signal. The radio receiver 200a: 2ooe further comprises a second signal path operatively connected to the input port for providing a negative polarity of the differential down- converted version of the received signal. The radio receiver 200a: 2ooe further comprises a cancellation circuit operatively connected to the first signal path for injecting a cancellation current in the first signal path. The radio receiver 200a: 2ooe further comprises a Self-Interference-Signal control circuit configured to receive channel and cross-interference information and to control the cancellation circuit based on the received channel and cross-interference information.

[0032] In Figs. 2, 3, 4, and 6 SIC is introduced to an NC-Rx system in the form of a cancellation current ici, controlled by the Self-Interference-Signal (SIS) signal, and upconverted towards the antenna by a mixer Mixer 1, resulting in cancellation of the self-interference at the input port.

[0033] In some embodiments, the first signal path comprises a first passive mixer (Mixer 1) and a first transimpedance amplifier TIAi operatively connected in series with each other. In further detail, in the radio receiver 200a shown in Fig. 2, part of the SIC current ici might leak into the transimpedance amplifier TIAi, resulting in that only a portion of the current is effectively up-converted to RF at the antenna / input-port for SIC. One way to mitigate the issue of current leaking towards the TIAi is to introduce a resistor Ri to reduce the leakage into TIAi (as in the radio receiver 200b of Fig. 3(a)) or a second mixer switch (as in the radio receiver 200c Fig. 3(b)). That is, in some embodiments, the first signal path further comprises a resistor Ri operatively connected in series between the first passive mixer Mixeri and the first transimpedance amplifier TIAi. In some embodiments, the cancellation circuit is operatively connected to the first signal path between the passive mixer and the first transimpedance amplifier TIAi. In some embodiments, the Self-Interference-Signal control circuit is configured to control the cancellation circuit in accordance with a calibration procedure performed during operation of the radio receiver 2ooa:2ooe.

[0034] A two-switch mixer allows to reduce the amount of cancellation current leaking towards the TIA. Therefore, in some embodiments, the first passive mixer Mixeri is a two-switch mixer, and wherein a first current source ici of the at least one current source ici, ic2 is operatively connected to a center tap of the two-switch mixer. Further, a second current source allows to further reduce the amount of cancellation current leaking towards the TIA, and can be used to suppress additional noise introduced by the cancellation. Therefore, in some embodiments, a second current source ic2 of the at least one current source ici, ic2 is operatively connected to an input of the first transimpedance amplifier TIAi.

[0035] As Figs. 2, 3, 4, and 6, in some embodiments, the second signal path comprises a radio-frequency transconductance amplifier (denoted Gm), a second passive mixer (denoted Mixer2), and a second transimpedance amplifier TIA2operatively connected in series with each other.

[0036] Further, in Fig. 4 is shown a radio receiver 2ood where the continuous SIS signals have been converted into pulses that can be time aligned with the switching of Mixeri, in time, frequency, and / or duty-cycle. That is, in some embodiments, the Self- Interference-Signal control circuit further is configured to control the cancellation circuit using pulsed signals, wherein the pulsed signals are aligned with switching of the first passive mixer Mixeri with respect to time, frequency, and duty-cycle.

[0037] Further, a second current source ic2 has been introduced at the input of TIAi to cancel the leakage of ici towards TIAi. That is, in some embodiments, the cancellation circuit comprises at least one current source ici, ic2 configured to tune amplitude and phase of the cancellation current, and where the Self-Interference-Signal control circuit is configured to control the amplitude and phase based on the received channel and cross-interference information. The difference between ici and ic2 is the magnitude and the sign of the currents. If ici has the normalized magnitude of i and a positive phase, then ic2 has a magnitude a, which is less than i, and a negative phase. The value of a can be set by the ratio of RSw,i and RSw,2, i.e., how much of ici that leaks towards the input of TIAi. The impedance of RSw,i and RSw,2 can be set to match the NC-Rx to the antenna.

[0038] The behavior of the radio receiver 2ood as shown in Fig. 4 will be studied next. Using the second current source ic2, the radio receiver 2ooe has three main modes of operation: for perfect SIC (denoted mode 1), for cancellation of the leakage from ici (denoted mode 2), and for cancellation of additional noise introduced by the SIC system (denoted mode 3). Further aspects of mode 1 will now be disclosed, ici provides a first level of SIC, but also introduces a residue at the input port, leaking towards the second signal path and eventually present at the output of TIA2. In this mode, ic2 is set so the output of TIAi equals the output of TIA2. That is, in some embodiments, the amplitude and phase of the second current source ic2 are set to equal an output of the first transimpedance amplifier TIAi to an output of the second transimpedance amplifier TIA2. Perfect SIC is then achieved when the first signal path is combined to the second signal path. The leakage from ici towards TIAM is partially cancelled. Further aspects of mode 2 will now be disclosed. The residue introduced by ici at the input port is amplified by the second signal path and present at the output of TIAA. In this mode, ic2 is set to compensate this residue on the first signal path, so only a small part of the ici residue is present at the output of TIAM. Hence, in some embodiments, the amplitude and phase of the second current source ic2 are by the Self-Interference-Signal control circuit controlled to compensate for residue of the first current source ici on the first signal path. This maximizes the linearity of the first signal path, but reduces the SIC when combining the first and the second signal paths. Further, in some embodiments, the amplitude and phase of the second current source ic2 are by the Self-Interference-Signal control circuit controlled to suppress noise introduced by the Self-Interference-Signal control circuit. Further aspects of mode 3 will now be disclosed. Additional noise introduced by a SIC system generally remains uncancelled, because it is only present in the SIS signal and not in the self-interference itself. With the herein disclosed radio receiver, noise suppression from the SIC system is possible using ic2. If cancellation can be performed by two out-of-phase identical signals, the same applies to the noise from the SIC system. If made differential, (i.e., the noise is identical, amplitude-wise, and statistically, but out-of-phase), then the SIC noise can be cancelled.

[0039] In further detail, the SIC system noise, injected by ici, sees a higher impedance from the antenna impedance and Rswi, while seeing a lower impedance from Rsw2 and the input of TIAi. The result is that most of the noise current from ici goes towards the TIAi input (as the impedance towards Rswi and the antenna is lower). The noise current that flows towards the antenna impedance is converted into a voltage, which is then amplified by the second signal path and is present at the output of TIA2. The inverted noise current is injected by ic2, cancelling the noise at the TIAi input. A noise voltage is present at the output of TIAi with the same phase as the noise voltage at the output of TIA2. Therefore, the amplitude of the noise voltage at the output of TIAi is set by ic2.

[0040] Denote the ratio between ici and ic2 by a. The value of a can be set to maximize SIC (first mode), or to minimize the amount of ici leaking in TIAi (second mode), or to determine the amplitude of the output noise (third mode). Hence, in some embodiments, the Self-Interference-Signal control circuit further is configured to selectively set a ratio between the amplitude and phase of the first current source ici and the amplitude and phase of the second current source ic2 in accordance with different modes of operation. This means that SIC and noise cancelation might not be fulfilled simultaneously. This tradeoff is illustrated in Fig. 5. In more detail, Fig. 5 shows simulation results and it is possible to identify the three main modes of operation in the figure. For the simulations, the currents were normalized to ici = 2 and ic2 = 1. When ic2is about 1.05, 38dB SIC is achieved at the Rx output (i.e., when combining the first and the second signal path). This corresponds to the first mode. The SIC on the first signal path alone is about 25dB. When ic2 =1 (ici / 2), all leakage from ici is cancelled, resulting in a 36dB SIC on the first signal path. When the first and second signal paths are combined, the SIC is about 26dB. This corresponds to the second mode. When iC2 is about 1.55, the NF is 2.4dB, which is the same than the NC-Rx without any SIC circuit. All the noise from the SIC circuit is cancelled, which corresponds to third mode.

[0041] By introducing a current integrating element, such as a shunt capacitor Cc, into the double switched mixer, additional out-of-band filtering is introduced, and this limits the size of the capacitor. In some embodiments, the two-switch mixer comprises a shunt capacitor Cc operatively connected to the center tap of the two-switch mixer. An example of such a radio receiver 2ooe is shown in Fig. 6. This radio receiver 2ooe comprises a DAC and is appropriate for digital assisted SIC. One reason for this is that the radio receiver 2ooe does not require individual phase / delay tuning of ici and ic2. By integrating the current pulses of ici with a shunt capacitor Cc, the injection node voltage is at baseband frequency, but the current to each terminal is still a high- frequency pulse and the phase-shift between the RF-terminal, current injection terminal, and the baseband terminal is less than i degree.

[0042] A full-duplex transceiver ooar ooc comprising a radio receiver 2ooa:2ooe as disclosed above is illustrated in Fig. 7. Fig. 7(a) shows an example of a full-duplex transceiver 700a with analog SIC. Fig. 7(b) shows an example of a full-duplex transceiver 700b with digital-assisted SIC system. Fig. 7(c) shows an example of a full-duplex transceiver 700c with a hybrid SIC architecture. That is, in some embodiments, the Self-Interference-Signal control circuit has an analog architecture, a digitally assisted architecture, or a hybrid architecture. As schematically illustrated in Fig. 7, in some examples, the full-duplex transceiver 7003:7000 is a single antenna transceiver, or comprises an antenna array with a circulator at each input port, or comprises an antenna array with separate antennas for transmission and reception. As further schematically illustrated in Fig. 7, in some examples, the radio receiver further comprises a subtractor (denoted in the figure) for subtracting an output of the second transimpedance amplifier TIAA from an output of the first transimpedance amplifier TIAi. The subtractor, via a third signal path comprising analog baseband circuitry and an analog-to-digital converter operatively connected in series with each other, is operatively connected to digital baseband circuitry (denoted DBB). In some examples, as in Fig. 7, the Self-Interference-Signal control circuit is operatively connected to the first signal path and the third signal path via delay elements (denoted T) and buffers (denoted Buf) and attenuators (denoted Att.). In some embodiments, the full-duplex transceiver ooar ooc is configured for timedivision duplex communication by having the cancellation circuit turned off. One advantage of the transceivers ooar ooc is that the SIC system can be disabled without any Rx performance degradation. Further, all buffers are in the current domain nodes, which means that no significant loading is present in the off-state, which is beneficial for Time-Division-Duplex (TDD), Frequency-Division-Duplex (FDD), and FD. The different transceivers ooar ooc illustrated in Fig. 7 will now be disclosed in more detail.

[0043] In Fig. 7(a) the output of the TX / PA is sensed (a coupler can be used for this purpose) and feed through an attenuator (denoted Att.), and then down-converted (using a mixer denoted Mixersis) to baseband. This signal is thus a baseband replica of the Tx signal sent to the antenna interface. The same signal will also be present at the input of the Rx, in an attenuated form. The Tx replica is depicted as the Self-Interference- Signal (SIS), present at baseband and this signal is signal processed in the analog domain for the full-duplex transceiver 700a. Furthermore, in the present example, the analog signal processing consists of the delay elements (denoted T), which includes multiple delay elements in parallel, to generate a signal to also cancel reflections. In the present example, buffers (denoted Buf) in the beginning of the NC- Rx, after the mixer MixerRx,i and before the analog baseband (denoted Analog BB) are transconductors. The output is in the current domain and the last buffer between the Analog BB and the Analog-to-Digital Converter (ADC) can be in the voltage- or current-domain. The first buffer, after MixerRx,i, feeds a SIS current at the baseband terminal of the mixer and the mixer then up-converts the SIS current to RF, where it cancels the self-interference at the RF input of the NC-Rx. Further, the second buffer, before the Analog BB, is used to cancel the self-interference residue from the aforementioned SIC at the RF input. This is needed due to the gain of the transconductor (denoted -Gm), the two TIAs, and the gain, due to the subtraction from the first and second signal paths, which is implemented with transconductors (i.e., with Gm cells). For the SIC with this current injection, different delay (T) and signal amplitude might be required, because the delay / phase-shift caused by blocks in the NC-RX is different from the one used for the SIC at the RF-input. Finally, the third SIC tap, provided between the Analog BB and the ADC, requires a different delay (T) and signal amplitude in order to cancel the self-interference residue from the two SIC circuits earlier in the NC-Rx chain. One advantage of the transceiver 700a is that it has the most straight forward approach, where signals are kept in the analog domain.

[0044] In Fig. 7(b), the output of the TX / PA is feed through an attenuator (denoted Att.), then down-converted to baseband using mixer MixersE and then converted by the ADC to the digital domain, as illustrated by the signal denoted DSE. This digital representation of the Tx output signal is feed to a self-interference signal generator (denoted Si-Signal Generator), which is also fed the digital data of the Tx (denoted DTX), the digital version of the received data (denoted DRX), and also a digital control signal (denoted Dctri). That is, in some embodiments, the channel and crossinterference information is based on any, or any combination, of: an analog-to-digital converted version of the received signal, a digital transmission signal, an analog-to- digital converted version of an analog transmission signal, a digital control signal. The channel information might represent channel properties of a wireless communication link established between the full-duplex transceiver yooaryooc and some other transceiver. Further in this respect, the radio receiver might be the receiver of this wireless communication link. The channel information might describe how a signal propagates from the transmitter to the receiver and represent the combined effect of, for example, scattering, fading, and power decay with distance between transmitter and receiver. The cross-interference information refers to information of the interference resulting from the coupling between the antennas at the full-duplex transceiver yooaryooc. The Si-Signal Generator is used to generate SIS signals representing the non-linear behavior of the Tx, Rx, and the SIC circuits, to generate delays, long and short for the direct-path from Tx to Rx, and also to generate long and short delays for reflections and scattering effects. Finally, the generated signal from the Si-Signal Generator, denoted Dsis, is converted into the analog domain by a Digital-to-Analog Converter (DAC) and this analog signal is fed to the SIC buffers. SIC is performed as in Fig. 7(a), but the delays (denoted T) are much shorter in Fig. 7(b) than in Fig. 7(a), and only need to compensate for the propagation within the NC-Rx. One advantage of the transceiver 700b is that more complex SIS operations can be performed in the digital domain with the ability to use Machine Learning (ML) to train of the system. Further, it does not require any complex routing when used in a beamforming antenna array. The hybrid SIC system in Fig. 7(c) is the same from Tx point-of-view as the digital assisted SIC system. One difference is how the Si-Signal Generator and the analog SIC circuits work. The Si-Signal Generator is mainly used to model the non-linear behavior of the Tx, Rx, and the SIC circuits. Longer delays can also be implemented, but synchronization (with respect to delay / phase and amplitude) of the SIS are analog functions in the analog domain, as in the analog SIC system (i.e., as in Fig. 7(a)). The transceiver 700c uses the same SIC-circuits as the transceiver 700a and the transceiver 700b. One advantage of the transceiver 700c is that is the use of more complex SIS operations when needed, less complex routing in a beamforming antenna array, lower requirements on the ADC and DAC, associated with the SI- Signal Generator.

[0045] The functionality of the double switch mixer 800, acting as a full-duplex-mixer, is shown in Fig. 8. The local oscillators (LO) are fed an even distribution over the LO period (TLO), where the LO pulse width is equal to TLO / N, and where N is the number of phases. When each LO phase is in the high state, the related switch is turned ON and conducts. As the related switch is turned ON, the nodes in the double switch mixer has low impedance, while injecting pulsed currents for SIC. The pulsed current injection is performed when the related LO is in the high-state, and the amplitude and frequency information is stored on top of the pulse. This is the same as for the baseband pulses of a passive-mixer operating in current mode. The baseband information is stored on top of the pulse and may be integrated to retrieve only the baseband information. Further, it is shown that the pulses from ici,i and ic2,i have different amplitudes and are out-of-phase. One reason why ici,i has a higher amplitude is because it is divided into two by the current division of Rswi and Rsw2. By adding half of ici,i to ic2,i, the resulting current is much lower or cancelled out, this is shown by the amplitude of the current iTIA11going into the TIA input load ZTIA11.Furthermore, the SIS current pulses for ici,i are integrated into a baseband voltage by the shunt capacitor Cc. This is shown as VCc t, and it can be observed that the functionality is the same as for a sample and hold circuit, this feature also adds to the current used to perform the SIC, in the form of stored charges in Cc.

[0046] The IMBB current contains up-converted information / signal-entities, but also a baseband counterpart of the same information. To cancel / suppress the unwanted signals associated by the self-interference and the SIC system in IMBB, and by subtracting (or addition of two out-of-phase signals) ic2 from IMBB, a representation of these unwanted signals are present in ic2. After the subtraction of ic2 from IMBB, a cancelation / suppression of the “SIS”, “TX Noise Replica”, and “SIC System Noise” is observed, and this is best seen in the TIA input current iTjAM. The baseband signal is selected by integrating the iTIA1current, for example by including a shunt capacitor to the TIA input impedance (ZTIA1) and also by using an active low-pass filter as the TIA. Finally, if the signals are present at the output of TIAi and TIA2, and are in-phase, they are further cancelled as common-mode.

[0047] To further increase the range of handled self-interference power (Psi), the main bottleneck of the double switch mixer, with regards to Psi should be defined and the bottleneck is the voltage over the cap Cc, i.e., VCc. The other nodes of the double switched mixer can be considered signal -ground or virtual signal-ground for the selfinterference, but the voltage VCcis set by the power within ici. The LO terminals will follow VCc, to ensure that the switches will turn ON, and as an additional benefit, the connected baseband TIA can operate with a higher supply voltage, i.e.. the TIA input DC-level is different. By selecting a higher supply voltage for the TIA, the RX linearity is improved, but the linearity of the double switched mixer is not affected by the TIA supply voltage, the limitation with the bootstrap will still be the voltage VCc. Furthermore, the linearity of the mixer with regards to the self-interference is improved with bootstrapping.

[0048] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A radio receiver (200a: 2ooe) for full-duplex communication, the radio receiver (2ooa:2ooe) comprising: an input port for receiving a signal from an antenna; a first signal path operatively connected to the input port for providing a positive polarity of a differential down-converted version of the received signal; a second signal path operatively connected to the input port for providing a negative polarity of the differential down-converted version of the received signal; a cancellation circuit operatively connected to the first signal path for injecting a cancellation current in the first signal path; and a Self-Interference-Signal control circuit configured to receive channel and cross-interference information and to control the cancellation circuit based on the received channel and cross-interference information.

2. The radio receiver (2ooa:2ooe) according to claim 1, wherein the first signal path comprises a first passive mixer (Mixeri) and a first transimpedance amplifier (TIAM) operatively connected in series with each other.

3. The radio receiver (2ooa:2ooe) according to claim 2, wherein the first signal path further comprises a resistor (RM) operatively connected in series between the first passive mixer (Mixeri) and the first transimpedance amplifier (TIA1).

4. The radio receiver (2ooa:2ooe) according to claim 2 or 3, wherein the cancellation circuit is operatively connected to the first signal path between the passive mixer and the first transimpedance amplifier (TIA1).

5. The radio receiver (2ooa:2ooe) according to claim 2, 3, or 4, wherein the cancellation circuit comprises at least one current source (iCi, iC2) configured to tune amplitude and phase of the cancellation current, and wherein the Self-Interference- Signal control circuit is configured to control the amplitude and phase based on the received channel and cross-interference information.

6. The radio receiver (2ooa:2ooe) according to claim 5, wherein the first passive mixer (Mixeri) is a two-switch mixer, and wherein a first current source (iCi) of the at least one current source (iCi, iC2) is operatively connected to a center tap of the two-switch mixer.

7. The radio receiver (2ooa:2ooe) according to claim 6, wherein a second current source (iC2) of the at least one current source (iCi, iC2) is operatively connected to an input of the first transimpedance amplifier (TIA1).

8. The radio receiver (2ooa:2ooe) according to claim 5 or 6, wherein the two- switch mixer comprises a shunt capacitor (Cc) operatively connected to the center tap of the two-switch mixer.

9. The radio receiver (2ooa:2ooe) according to any preceding claim, wherein the second signal path comprises a radio-frequency transconductance amplifier (Gm), a second passive mixer (Mixer2), and a second transimpedance amplifier (TIA2) operatively connected in series with each other.

10. The radio receiver (2ooa:2ooe) according to a combination of claim 2 and 9, wherein the amplitude and phase of the first current source (iCi) are set to equal an output of the first transimpedance amplifier (TIAi) to an output of the second transimpedance amplifier (TIA2).

11. The radio receiver (2ooa:2ooe) according to a combination of claim 2 and 9, wherein the amplitude and phase of the second current source (iC2) are by the Self- Interference-Signal control circuit controlled to compensate for residue of the first current source (iCi) on the first signal path.

12. The radio receiver (200a: 2ooe) according to a combination of claim 2 and 9, wherein the amplitude and phase of the second current source (iC2) are by the Self- Interference-Signal control circuit controlled to suppress noise introduced by the Self-Interference-Signal control circuit.

13. The radio receiver (2ooa:2ooe) according to any of claims 2 to 12, wherein the Self-Interference-Signal control circuit further is configured to selectively set a ratio between the amplitude and phase of the first current source (iCi) and the amplitudeand phase of the second current source (iC2) in accordance with different modes of operation.

14. The radio receiver (2ooa:2ooe) according to claims 2 to 13, wherein the Self- Interference-Signal control circuit further is configured to control the cancellation circuit using pulsed signals, wherein the pulsed signals are aligned with switching of the first passive mixer (Mixeri) with respect to time, frequency, and duty-cycle.

15. The radio receiver (2ooa:2ooe) according to any preceding claim, wherein the channel and cross-interference information is based on any, or any combination, of: an analog-to-digital converted version of the received signal, a digital transmission signal, an analog-to-digital converted version of an analog transmission signal, a digital control signal.

16. The radio receiver (2ooa:2ooe) according to any preceding claim, wherein the Self-Interference-Signal control circuit is configured to control the cancellation circuit in accordance with a calibration procedure performed during operation of the radio receiver (2ooa:2ooe).

17. The radio receiver (2ooa:2ooe) according to a combination of claim 2 and 9 or claim 10, wherein the radio receiver (200a: 2ooe) further comprises a subtractor (-) for subtracting an output of the second transimpedance amplifier (TIA2) from an output of the first transimpedance amplifier (TIA1), and wherein the subtractor, via a third signal path comprising analog baseband circuitry and an analog-to-digital converter operatively connected in series with each other, is operatively connected to digital baseband circuitry.

18. The radio receiver (2ooa:2ooe) according to claim 17, wherein the Self- Interference-Signal control circuit is operatively connected to the first signal path and the third signal path via delay elements and buffers.

19. The radio receiver (2ooa:2ooe) according to any preceding claim, wherein the Self-Interference-Signal control circuit has an analog architecture, a digitally assisted architecture, or a hybrid architecture.

20. A full-duplex transceiver, the full-duplex transceiver (yooaryooc) comprising a radio receiver (2ooa:2ooe) according to any of the preceding claims.

21. The full-duplex transceiver (7003:700c) according to claim 20, wherein the full- duplex transceiver (7003:700c) is a single antenna transceiver, or comprises an antenna array with a circulator at each input port, or comprises an antenna array with separate antennas for transmission and reception.

22. The full-duplex transceiver (7003:7000) according to claim 20 or 21, wherein the full-duplex transceiver (7003:700c) is configured for time-division duplex communication by having the cancellation circuit turned off.

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