TRANSCEIVER

TECHNICAL FIELD

The present invention relates to a Radio Frequency (RF) front end for wireless communications, in particular for use in a Half Duplex (HD), Full Duplex (FD) and/or Frequency Division Duplex (FDD) transceiver. Accordingly, the invention also relates to a transceiver with a multi- mode RF front end. The RF front end of the invention is especially based on a Quadrature Balanced Power Amplifier (QBPA).

BACKGROUND

In transmit and receive (T/R) antenna wireless communication scenarios, a Low Noise Amplifier (LNA) in the receive path needs to be protected from a transmit signal leakage (TX leakage). In most scenarios, a minimum T/R isolation required to protect the LNA is about 30 dB. For simultaneous transmit receive (STR) antenna wireless communication scenarios, such as FD or FDD without a Diplexer, a minimum T/R isolation of 50-60 dB is required. Hence, a Transmit-Receive Self Interference Cancellation (SIC) mechanism is needed for STR wireless systems. Conventional implementations of such SIC are implemented at an output of a power amplifier (PA), i.e. between the transmit (TX) output and the receive (RX) input, hence they“load” both TX and RX channels, thus creating a loss of power efficiency and of signal to noise ratio. FIG. 11 shows conceptually an example of a conventional SIC implementation, as it is common in wireless communication applications. A SIC unit is implemented at the PA output (i.e.“post- PA”). In particular, an input signal of the SIC unit is an output signal from the PA. Such implementation introduces both power efficiency loss and signal to noise ratio degradation.

FIG. 12 shows a first example of a modified Quadrature Balanced Power Amplifier (QBPA) RF Front End (RFFE). This example bases in particular on a modified QBPA with un-equal transmit paths (unequal PAA and PAB). Such a 3 ports version RFFE includes a TX input port an RX output port and an antenna TR/RX port. The modification enables the flexibility to create a feed-forward TX cancellation signal in the receive path with the right amplitude and anti phase to the TX signal reflected from the antenna. Hence, the first example realizes a dual mode RF front end with a built-in SIC capability, so as to increase the isolation between transmit and receive ports.

However, the first example requires control of both amplitude and phase of the two PA paths of PA _A and PA _B , which adds considerable complexity to the front end design. Further, the first example is limited in isolation of a wide-band signal, but the use of such a wide-band signal is of high interest.

FIG. 13 thus shows a second example of a modified QBPA RFFEs. This 4 ports version adds a SIC input port. It takes advantage of the QBPA structure, and employs two identical transmit paths (PAA = PAB). In this way, the feed forward cancellation signal is injected from the 4th port that was previously un-used, after normalizing by the gain of the two equal paths. The cancellation signal will re-construct at the receive port to cancel the transmit signal reflected from the antenna.

SUMMARY

In view of the above-mentioned disadvantages and examples, embodiments of the present invention aim to provide an improved multi-mode RF front end. An objective is in particular to design a multi-mode RF front end with an improved power efficiency of a SIC implementation. The multi-mode RF front end should be easy to integrate, e.g. on a chip and/or PCB, and should have a low SIC signal to noise degradation.

The objective is achieved by the embodiments provided in the enclosed independent claims. Advantageous implementations of the embodiments are further defined in the dependent claims.

In particular the embodiments can generate SIC signal/s for either version and mostly for 4 port modified QBPA. All the new embodiments generate the SIC signal in a“pre-PA” manner and reuse the QBPA power amplifiers to amplify the SIC signals as well, together with the TX signal. This dramatically improves an efficiency of the SIC implementation and minimizes signal to noise losses.

A first aspect of the invention provides a RF front end for wireless communication, comprising an antenna port for outputting a transmit signal to and receiving a receive signal from an antenna, a receive port for outputting the receive signal to a signal processing section, a cancellation input signal generator for generating a cancellation input signal and outputting the cancellation input signal to a QBPA, and the QBPA comprising a first, second, third and fourth port, wherein the QBPA is configured to: receive a transmit input signal at the first port or the fourth port, receive the receive signal at a second port connected to the antenna port, receive the cancellation input signal from the cancellation input signal generator, amplify the transmit input signal and the cancellation input signal, generate the transmit signal from the transmit input signal and output the transmit signal at the second port, generate a cancellation signal from the cancellation input signal and output the cancellation signal and the receive signal at the third port connected to the receive port. The cancellation input signal is generated by the cancellation input signal generator in a“pre- PA” manner. In particular, the cancellation input signal is output to the QBPA, thus, the QBPA amplifies the SIC signal(s) together with the TX signal(s). The cancellation signal is reconstructed at the third port, and can thus cancel leakage signals caused at the third port when operating in transmit mode (TX leakage). In particular, the cancellation signal can cancel the transmit signal that is reflected from the antenna (TX antenna reflections). The four-port RF front end of the first aspect enables multi-mode operation with re-using amplifiers, and particularly has a reduced SIC power consumption.

In an implementation form of the first aspect, the cancellation input signal generator comprises a SIC filter. Optionally, the SIC filter may be used to suppress TX interference, i.e. TX leakage, and TX signal antenna reflections.

In an implementation form of the first aspect, the cancellation input signal generator is configured to generate the cancellation input signal based on the transmit input signal and/or based on an SIC signal received at the first or fourth port. In this way, there is no need to feed an extra signal for constructing the cancellation input signal. Alternatively, an extra SIC signal may also be injected to the cancellation input signal generator to form the cancellation input signal.

In an implementation form of the first aspect, the cancellation input signal generator is configured to generate the cancellation input signal in a manner that the cancellation signal cancels a leakage signal caused at the third port when the transmit signal is output from the second port.

Accordingly, the T/R isolation properties of the RF front end of the first aspect are improved. Further, by adjusting the cancellation input signal, the T/R isolation can be adapted to different leakage mechanisms. Thus, the RF front end of the first aspect offers a large flexibility.

In a further implementation form of the first aspect, the QBPA comprises a first coupler configured to divide an input signal received from the first or the fourth port of the QBPA into a first part and second part, with a phase difference of 90° between the first part and second part, wherein the input signal is the transmit input signal or the cancellation input signal; a first amplifier configured to amplify the first part of the input signal and output the amplified first part of the input signal to a second coupler; a second amplifier configured to amplify the second part of the input signal and output the amplified second part of the input signal to the second coupler; and the second coupler configured to combine the amplified first and second parts of the input signal to form a first and second output signal at the second and third ports of the QBPA, respectively.

The QBPA comprises two power amplifiers. Optionally, the first amplifier and the second amplifier may provide different gains. Alternatively, the amplification by the first amplifier may be the same as the amplification by the second amplifier.

In a further implementation form of the first aspect, the input signal of the first coupler comprises the transmit input signal, wherein the second coupler is configured to combine the amplified first and second parts of the transmit input signal such that they constructively form the transmit signal at the second port and destructively cancel each other at the third port.

Thus, a transmit signal leakage to the third port (i.e. towards the signal processing section used to process the receive signal) is reduced or even non-existent (notably not (yet) taking into account antenna reflections of the transmit signal). In a further implementation form of the first aspect, the cancellation input signal generator comprises a first SIC filter arranged between the first coupler and the first amplifier, and a second SIC filter arranged between the first coupler and the second amplifier, wherein the first SIC filter is configured to: receive the first part of the input signal from the first coupler, generate a first cancellation input signal, and output the first cancellation input signal to the first amplifier; and the second SIC filter is configured to: receive the second part of the input signal from the first coupler, generate a second cancellation input signal, and output the second cancellation input signal to the second amplifier.

A maximum SIC degree of freedom may be achieved by implementing two independent analog SIC filters at each PA input. This, however, may not provide the smallest form factor or efficiency, especially with passive delay lines SIC or generate noise and non-linearity with active SIC filters.

In a further implementation form of the first aspect, the second coupler is further configured to combine the amplified first and second cancellation input signal such that they constructively form the cancellation signal at the third port and destructively cancel each other at the second port.

The cancellation signal at the third port can cancel any T/R leakage, for instance, reflections of the transmit signal at the antenna, which reconstructs at the third port.

In a further implementation form of the first aspect, the RF front end further comprises a splitter, and the cancellation input signal generator comprises a third SIC filter, wherein the splitter being is configured to: receive the transmit input signal, split the transmit input signal into a third and fourth parts, output the third part of the transmit input signal to the third SIC filter and output the fourth part of the transmit input signal to the fourth port of the QBPA connected to the first coupler; and the third SIC filter is configured to: receive the third part of the transmit input signal from the splitter, generate the cancellation input signal, and output the cancellation input signal to the first coupler.

Optionally, the TX input signal may be split into two different QBPA inputs. The TX signal may be higher in power and the SIC signal may be fed to the other input after passing an analog SIC filter. This alternative design may better suit passive SIC filtering. In a further implementation form of the first aspect, the RF front end further comprises an in- phase and quadrature digital-to-analog converter, IQ DAC, an IQ baseband processing component, IQ BB, and a first and second mixers, and the cancellation input signal generator comprises a BB SIC filter, wherein the IQ DAC is configured to receive a digital signal, convert the digital signal to an analog signal and output the analog signal to the IQ BB; the IQ BB is configured to receive the analog signal from the IQ DAC, generate a BB signal from the analog signal and output the BB signal to the BB SIC filter and the first mixer; the BB SIC filter is configured to receive the BB signal from the IQ BB, generate a BB cancellation input signal from the BB signal and output the BB cancellation input signal to the second mixer; the first mixer is configured to receive the BB signal from the IQ BB, mix the BB signal with a low- frequency signal to form the transmit input signal, and output the transmit input signal to the fourth port of the QBPA; the second mixer is configured to receive the BB cancellation input signal from the BB SIC filter, mix the BB cancellation signal with the low-frequency signal to form the cancellation input signal, and output the cancellation input signal to the first port of the QBPA.

The implementation of RF SIC filters may be too large physically and/or too complicated for some applications. Thus, a simple analog baseband (BB) SIC implementation may be up- converted to RF as described in this implementation form. A complex low frequency signal is used to generate the transmit input signal and the cancellation input signal. In a further implementation form of the first aspect, the QBPA is configured to: receive the cancellation input signal from the cancellation input signal generator at the first port, and receive the transmit input signal at the fourth port.

A TX chain and a SIC chain may be separate. In particular, the cancellation input signal may be fed to one port of the QBPA, and the transmit input signal may be fed to another port of the QBPA.

In a further implementation form of the first aspect, the second coupler is further configured to combine the amplified first and second parts of the cancellation input signal such that they constructively form the cancellation signal at the third port and destructively cancel each other at the second port. A second aspect of the invention provides a FD or HD transceiver comprising a RF front end according to the first aspect or any of its implementation forms, and a transmit and receive antenna connected to the antenna port of the RF front end.

Accordingly, the transceiver of the second aspect achieves the advantages and effects of the RF front end of the first aspect.

In an implementation form of the second aspect, if the TX chain and the SIC chain are separate, the transceiver further comprises a digital baseband processing module, a digital front end and an analog baseband and RF processing module, wherein the digital baseband processing module is configured to: receive a frequency signal, generate a first and second sequences from the frequency signal, and output the first and second sequences to the digital front end; the digital front end is configured to: receive the first and second sequences from the digital baseband processing module, convert the received first and second sequences, and output converted first and second sequences to the analog baseband and RF processing module; and the analog baseband and RF processing module is configured to: receive the converted first and second sequences from the digital front end, generate a cancellation input signal from the converted first sequence and output the cancellation input signal to a first port of a QBPA in the RF front end, and generate a transmit input signal from the converted second sequence and output the transmit input signal to a fourth port of the QBPA in the RF front end.

The implementation of analog SIC filters may be physically too large and or too complicated for some applications. Thus, a simple digital BB SIC implementation may be up-converted to RF as described in this implementation form. After a digital signal processing procedure, digital signals may be converted to RF signals including the transmit input signal and the cancellation input signal.

In an implementation form of the second aspect, the digital baseband processing module is further configured to convert a mix of the frequency signal and a SIC coefficient to form the first sequence.

In another implementation form of the second aspect, the first sequence is identical to the second sequence, and the digital front end is further configured to filter the received first sequence before converting it. A third aspect of the invention provides a method for performing a wireless communication using a RF front end, the method comprising providing a transmit signal to and receiving a receive signal from an antenna via an antenna port of the RF front end, using a cancellation input signal generator to: generate a cancellation input signal and output the cancellation input signal to a Quadrature Balanced Power Amplifier, QBPA, using the QBPA, to: receive a transmit input signal at the first port or the fourth port, receive the receive signal at the second port connected to the antenna port, receive a cancellation input signal from the cancellation input signal generator, amplifier the transmit input signal and the cancellation input signal, generate the transmit signal from the transmit input signal and output the transmit signal at the second port, generate a cancellation signal from the cancellation input signal, and output the cancellation signal and the receive signal at the third port, and outputting the receive signal to a signal processing section via a receive port connected to the third port.

The method of the third aspect may be developed in implementation forms according to the implementation forms described above for the first aspect. With the method of the third aspect and its implementation forms, the advantages and effects of the RF front end of the first aspect and its respective implementation forms are thus achieved.

It has to be noted that all devices, elements, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof.

BRIEF DESCRIPTION OF DRAWINGS

The above described aspects and implementation forms of the present invention will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which FIG. 1 shows a multi-mode RF front end according to an embodiment of the invention.

FIG. 2 shows a multi-mode RF front end according to an embodiment of the invention. FIG. 3 shows a multi-mode RF front end according to an embodiment of the invention. FIG. 4 shows a multi-mode RF front end according to an embodiment of the invention. FIG. 5 shows a multi-mode RF front end according to an embodiment of the invention. FIG. 6 shows a multi-mode RF front end according to an embodiment of the invention. FIG. 7 shows a transceiver (FD, FDD or HD) according to an embodiment of the invention.

FIG. 8 shows a transceiver (FD, FDD or HD) according to an embodiment of the invention.

FIG. 9 shows a transceiver (FD, FDD or HD) according to an embodiment of the invention.

FIG. 10 shows a method according to an embodiment of the invention FIG. 11 shows conceptually an example of a conventional SIC implementation FIG. 12 shows an example of a modified QBPA RF front end.

FIG. 13 shows another example of a modified QBPA RF front end.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a RF front 100 end according to an embodiment of the invention. The RF front end 100 is in particular a multi-mode RF front end, which is suitable for HD, FD and FDD wireless communications, for instance, in an HD, FD or FDD transceiver.

The RF front end 100 has an antenna port 101, to which an antenna 200 can be connected. The antenna port 101 is used to output a transmit signal 102 to the antenna 200 (in a transmit mode), and is used to receive a receive signal 103 from the antenna 200 (in a receive mode), either simultaneously (FD) or not simultaneously (HD).

The RF front end 100 also has a receive port 104, to which a receive path including a signal processing section 300 can be connected. The receive port 104 is used to output the receive signal 103, as received from the antenna 200 via the antenna port 101 , to the signal processing section 300.

The RF front end 100 also has a cancellation input signal generator 105. The cancellation input signal generator 105 generates a cancellation input signal 106 and outputs the cancellation input signal 106 to a QBPA 107 of the RF front end 100.

Thus, the RF front end 100 further has the QBPA 107. The QBPA 107 acts as a T/R isolation stage and allows STR. The QBPA 107 includes four ports, namely a first port 108, a second port 109, a third port 110, and a fourth port 111. The second port 109 is connected to the antenna port 101 , i.e. it is used to provide the transmit signal 102 to the antenna 200 and to receive the receive signal 103 from the antenna 200. The third port 110 is connected to the receive port 104, i.e. it is used to provide the receive signal 103 to the signal processing section 300.

The QBPA 107 is in particular configured to receive a transmit input signal 112 at the first port 108 or the fourth port 111, and to receive the cancellation input signal 106 from the cancellation input signal generator 105. The cancellation input signal 106 may be received at the first port 108 or the fourth port 111, or it can be received at other port inside the QBPA 107. For instance, the cancellation input signal 106 may be injected to an internal unit of the QBPA 107. Further, the QBPA 107 is configured to receive the receive signal 103 at the second port 110.

The QBPA 107 is configured to amplify the transmit input signal 112 and the cancellation input signal 106. It should be noted that the cancellation input signal 106 is generated before the PA input, and it is thus amplified together with the transmit input signal 112.

The QBPA 107 is further configured to generate the transmit signal 102 from the transmit input signal 112 and output it at the second port 109, to generate a cancellation signal 113 from the cancellation input signal 106 and output it at the third port 110, and to output the receive signal 103 received at the second port 110 at the third port 110.

Accordingly, in a transmit mode, the transmit signal 102 is generated (indicated by the dashed line 112- 02) and provided to the antenna 200. Further, the cancellation signal 113 is generated (indicated by the dashed line 106- 13) and provided to the signal processing section. Optionally, a SIC filter may be used to generate the cancellation input signal 106. Optionally, the cancellation input signal generator 105 may be configured to generate the cancellation input signal 106 based on the transmit input signal 112 and/or based on an SIC signal received at the first port 108 or fourth port 111. In particular, the cancellation signal 113 may cancel any leakage caused by the transmit signal 102 output to the antenna 200, e.g. reflections of the transmit signal 102 at the antenna 200, which are reflected back to the antenna port 101/second port 109 or cancel any other imperfections leading to other TX signal“leakage” phenomena between the second port 109 and the third port 110. In a receive mode, the receive signal 103 is conveyed from the second port 109 to the third port 1 10 (indicated by the dotted line) and provided to the signal processing section 300. As mentioned above, the transmit mode and receive mode may be set simultaneously.

FIG. 2 shows a multi-mode RF front end 100 according to an embodiment of the invention, which builds on the RF front end 100 shown in FIG. 1. Accordingly, same elements are provided with the same reference signs. FIG. 2 shows in particular how the transmit signal 102 is generated from the transmit input signal 112, and how the cancellation signal 111 is generated from“pre-PA” cancellation input signals. To this end, the QPBA 107 includes a first coupler 1071, a first amplifier 1072a, a second amplifier 1072b, and a second coupler 1073. The first coupler 1071, first amplifier 1072a and second coupler 1073 form at least part of a first signal path, and the first coupler 1071, second amplifier 1072b, and second coupler 1073 form at least part of a second signal path. Accordingly, the first amplifier 1072a is arranged in the first signal path, and the second amplifier 1072b in the second signal path.

The first coupler 1071 is configured to divide an input signal received from the first port 108 or the fourth port 111, into a first part and a second part. In particular, the input signal is the transmit input signal 112 or the cancellation input signal 106. For either of the signal 112 or 106, a phase difference of 90° is thereby generated between the first part and the second part. The first amplifier 1072a is configured to amplify the first part, and the second amplifier 1072b is configured to amplify the second part. The second coupler 1073 is further configured to combine the amplified first and second parts of the input signal to form a first and second output signal at the second port 109 and third port 110, respectively. Thereby, the amplified first and second transmit input signal parts are combined such that they constructively form the transmit signal 102 at the second port 109 and destructively cancel each other at the third port 110. In this way, the transmit signal 102 is generated from the transmit input signal 112 and is output only at the second port 109 to the antenna 200.

FIG. 3 shows a multi-mode RF front end 100 according to an embodiment of the invention, which builds on the RF front end 100 shown in FIG. 1 and/or FIG. 2. The cancellation input signal generator 105 may comprise a first SIC filter 1051 arranged between the first coupler 1071 and the first amplifier 1072a, and a second SIC filter 1052 arranged between the first coupler 1071 and the second amplifier 1072b.

In particular, the first SIC filter 1051 is configured to receive the first part of the input signal from the first coupler 1071. The first SIC filter 1051 is further configured to generate a first cancellation input signal, and to output the first cancellation input signal to the first amplifier 1072a. Similarly, the second SIC filter 1052 is configured to receive the second part of the input signal from the first coupler 1071. And the second SIC filter 1052 is further configured to generate a second cancellation input signal, and to output the second cancellation input signal to the second amplifier 1072b.

In this way, the first cancellation input signal and the second cancellation input signal are fed to the first amplifier 1072a and the second amplifier 1072b, respectively. Then the amplified first and second cancellation input signals are combined in the second coupler 1073. Particularly the second coupler 1073 is further configured to combine the amplified first and second cancellation input signals such that they constructively form the cancellation signal 113 at the third port 110 and destructively cancel each other at the second port 109. Further, also in this way, the cancellation signal 113 is generated from the first and second cancellation input signals and is output only at the third port 110 to the signal processing section 300 (here including a LNA 201). It should be noted here that 1051 and 1052 both generate different signals that for both include TX and Cancellation signals. As in all other cases, each amplifier than amplifies a different“mixed” version of both TX and SIC signals. As can be seen in Fig.2, the input to PA1 and PA2 includes the two mentioned TX and SIC signals but in a different phase combination that enable a TX summation by 1073 at 109 (subtracts at 110) while SIC is summed simultaneously by 1073 at 110 (and sure subtracts at 109). This is true for all embodiments here.

A maximum SIC degree of freedom may be achieved by implementing two independent SIC filters (e.g. analog SIC filters) at each PA input. This however may not provide the smallest form factor or efficiency especially with passive delay lines SIC. It may also generate noise and non-linearity with active SIC filters.

FIG. 4 shows a multi-mode RF front end 100 according to another embodiment of the invention, which also builds on the RF front end 100 shown in FIG. 1 and/or FIG. 2. Optionally, the RF front end 100 further comprises a splitter 114, and the cancellation input signal generator 105 comprises a third SIC filter 1053. The splitter 114 is configured to receive and split the transmit input signal 112 into a third and fourth parts. The splitter 114 is further configured to output the third part of the transmit input signal 112 to the third SIC filter 1053. The splitter 114 is further configured to output the fourth part of the transmit input signal 112 to the fourth port 111 of the QBPA 107 connected to the first coupler 1071.

The fourth part of the transmit input signal 112 is fed into the QBPA 107. Accordingly, the transmit signal 102 will be constructed based on the fourth part of the transmit input signal 112.

The third SIC filter 1053 is configured to receive the third part of the transmit input signal 112 from the splitter 1 14. The third SIC filter 1053 is further configured to generate and output the cancellation input signal 106 to the first port 108 of the QBPA 107 connected to the first coupler 1071. In this way, the cancellation input signal 106 is also fed into the QBPA 107. Accordingly, the cancellation signal 113 will be constructed based on the cancellation input signal 106.

It should be noted that, alternatively a TX signal can be split into two different QBPA inputs. The TX signal is higher in power and the SIC signal will be fed to the other input after passing an analog SIC filter. This alternative may better suit a passive SIC filtering design.

FIG. 5 shows a multi-mode RF front end 100 according to another embodiment of the invention, which also builds on the RF front end 100 shown in FIG. 1 and/or FIG. 2. Optionally, the RF front end 100 further comprises an IQ DAC 115, an IQ BB 116, and a first mixer 117a and a second mixer 117b. The cancellation input signal generator 105 comprises a BB SIC filter 1054. The IQ DAC 1 15 is configured to receive and convert a digital signal to an analog signal, and output the analog signal to the IQ BB. Accordingly, the IQ BB 116 is configured to receive the analog signal from the IQ DAC 115. The IQ BB 116 is further configured to generate a BB signal from the analog signal and output the BB signal to the BB SIC filter 1054 and the first mixer 117a. The BB SIC filter 1054 is configured to receive the BB signal from the IQ BB 116, generate a BB cancellation input signal from the BB signal and output the BB cancellation input signal to the second mixer 117b. Additionally, a complex low-frequency signal is provided in this embodiment. The first mixer 117a is configured to receive the BB signal from the IQ BB 116. The first mixer 117a is further configured to mix the BB signal with the low-frequency signal to form the transmit input signal 112, and output the transmit input signal 112 to the fourth port 111 of the QBPA 107. The second mixer 117b is configured to receive the BB cancellation input signal from the BB SIC filter 1054. The second mixer 117b is also configured to mix the BB cancellation signal with the low-frequency signal to form the cancellation input signal 106, and output the cancellation input signal 106 to the first port 108 of the QBPA 107.

Accordingly, the transmit signal 102 and the cancellation signal 113 will be constructed, respectively, based on the transmit input signal 112 and the cancellation input signal 106 fed into the QBPA 107, respectively.

Notably, the implementation of RF SIC filters may be too large physically and/or too complicated in some applications. In this way, a simple analog baseband SIC implementation may be up-converted to RF as described here.

FIG. 6 shows a multi-mode RF front end 100 according to another embodiment of the invention, which also builds on the RF front end 100 shown in FIG. 1 and/or FIG. 2. In particular, a SIC chain and a TX chain may be implemented separately.

The QBPA 107 is configured to receive the cancellation input signal 106 from the cancellation input signal generator 105 at the first port 108. And the QBPA 107 is also configured to receive the transmit input signal 112 at the fourth port 111.

The implementation of analog SIC filters may be too large physically and/or too complicated in some applications. Thus a simple digital BB SIC implementation maybe designed to up- convert digital signals to RF signals.

Optionally, according to the previous embodiments, the cancellation input signal 106 is fed into the QBPA 107. In such scenarios, the cancellation input signal 106 will go through the first coupler 1071 and is divided into the first and second parts of the cancellation input signal. The first and second amplifiers 1072a and 1072b will further amplify the first and second parts of the cancellation input signal, respectively. Accordingly, the second coupler 1073 is further configured to combine the amplified first and second parts of the cancellation input signal such that they constructively form the cancellation signal 113 at the third port 110 and destructively cancel each other at the second port 109. Further, also in this way, the cancellation signal 1 13 is generated from the first and second parts of the cancellation input signal and is output only at the third port 110 to the signal processing section.

FIG. 7 shows a transceiver 700 (HD, FD or FDD) according to an embodiment of the invention, which transceiver 700 comprises a RF front end 100 according to an embodiment of the present invention, in particular one of the RF front end 100 of FIG. 1 to FIG. 6. The transceiver 700 further comprises a transmit and receive antenna 200 connected to the antenna port 101 of the RF front end 100. The transceiver 700 may be able to operate in HD, FD and/or FDD mode, since the RF front end 100 is a multi-mode RF front end, and can specifically transmit and receive signals via the antenna 200 simultaneously. Due to the use of the RF front end 100, a transmit signal leakage is thereby greatly reduced in the transceiver 700.

FIG. 8 and FIG. 9 both show digital Full TX Chain Implementations for separate TX/SIC implementation. Particularly the RF front end 100 is the RF front end 100 of FIG. 6.

The transceiver 700 further comprises a digital baseband processing module 701, a digital front end 702 and an analog baseband and RF processing module 703. The digital baseband processing module 701 is configured to receive a frequency-domain signal, and generate a first and second time-domain sequences from the frequency-domain signal. In particular, the digital baseband processing module 701 may perform an inverse Fast Fourier Transform (IFFT) on the frequency-domain signal.

The digital baseband processing module 701 is further configured to output the first and second sequences to the digital front end 702. The digital front end 702 is configured to receive the first and second sequences from the digital baseband processing module 701. The digital front end 702 is also configured to convert the received first and second sequences, and output converted first and second sequences to the analog baseband and RF processing module 703. Optionally, the digital front end 702 may comprise IQ DACs.

Accordingly, the analog baseband and RF processing module 703 is configured to receive the converted first and second sequences from the digital front end 702. The analog baseband and RF processing module 703 is configured to generate a cancellation input signal 106 from the converted first sequence, and output the cancellation input signal 106 to a first port 108 of a QBPA 107 in the RF front end 100. Then the analog baseband and RF processing module 703 is further configured to generate a transmit input signal 112 from the converted second sequence and output the transmit input signal 1 12 to a fourth port 111 of the QBPA 107 in the RF front end 100. In this way, a transmit input signal 112 and a cancellation input signal 106 are constructed from digital signals, respectively. In a next stage, the transmit input signal 112 and the cancellation input signal 106 are fed into the RF front end 100 and processed accordingly as discussed in the previous embodiments.

As shown in FIG. 8, the digital baseband processing module 701 is further configured to convert a mix of the frequency-domain signal and SIC coefficients to form the first sequence. Particularly, the IFFT is performed on the frequency-domain signal to generate the second sequence. Meanwhile, the IFFT is performed on the mix of the frequency signal and the SIC coefficient, to generate the first sequence. Accordingly, the first sequence is used to form an SIC signal, and the second sequence is used to form a TX signal.

In another digital implementation as shown in FIG. 9, optionally the first sequence may be identical to the second sequence. In other words, the time-domain signal after IFFT processing is fed into the digital front end 702. The digital front end 702 is further configured to filter the received time-domain signal after IFFT processing before converting it. In this manner, only a single IFFT is used, and the application of the SIC coefficients is replaced with a filter applied on the time-domain signal.

FIG. 10 shows a method 1000 according to an embodiment of the invention. The method 1000 is for performing a wireless communication using a RF front end 100, in particular the RF front end 100 shown in one of FIG. 1 to FIG. 6. The method 1000 comprises a step 1001 of providing a transmit signal 102 to and receiving a receive signal 103 from an antenna 200 via an antenna port 101 of the RF front end 100. Further, the method 1000 comprises a step 1002 of using a cancellation input signal generator to generate a cancellation input signal and output the cancellation input signal to a QBPA 107 comprising a first, second, third and fourth port. The method 1000 further comprises using the QBPA 107 to: perform a step 1003 of receiving a transmit input signal 112 at a first port 108 or a fourth port 111, perform a step 1004 of receiving the receive signal 103 at the second port 109 connected to the antenna port 101, perform a step 1005 of receiving a cancellation input signal 106 from the cancellation input signal generator 105, perform a step 1006 of amplifying the transmit input signal 112 and the cancellation input signal 106, perform a step 1007 of generating the transmit signal 102 from the transmit input signal 112 and output the transmit signal 102 at the second port 109, perform a step 1008 of generating a cancellation signal 113 from the cancellation input signal 106, perform a step 1009 of outputting the cancellation signal 113 and the receive signal 103 at a third port 110. Finally, the method 1000 comprises a step 1010 of outputting the receive signal 103 to a signal processing section 201 via a receive port 104 connected to the third port 110.

In summary, embodiments of the present invention achieve multiple benefits. Advantages are: · The RF front end can be integrated on chip especially the digital to RF configurations.

• Wide-band cancellation of antenna reflections are possible.

• A very power efficient SIC implementation is achieved.

• Low SIC Signal to Noise degradation is achieved.

The present invention has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed invention, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article“a” or“an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.