A circuit device, method and non-transitory storage unit for beamforming

Abstract

The present invention relates to a circuit device, a method and a non-transitory storage unit for beamforming, and the present invention discloses a technology that enables digital predistortion for an amplifier, which can be implemented in a circuit device, a method and a computer instruction. The circuit device includes: an amplifier, which is used to amplify an analog version of a digital input signal; a built-in test circuit, which is configured to provide distortion information associated with the distortion affecting the amplifier; and a signal conditioner, which is used to perform feedforward predistortion of the digital input signal in a signal path of the digital input signal according to a predistortion relationship that maps the digital input signal to a predistorted version. The signal conditioner can be configured to adjust the predistortion relationship according to the distortion information.

Description

Technical Field

[0001] The present document relates to a circuit arrangement having an amplifier (eg, a high frequency power amplifier, a radio frequency RF power amplifier, a millimeter wave power amplifier, etc.).

[0002] The document also relates to a technique for predistorting a digital input signal in a circuit arrangement having an amplifier. The circuit arrangement can be used, for example, for beamforming applications.

[0003] The document also relates to a method for predistorting a digital input signal in a circuit arrangement having a radio frequency (RF) amplifier. Background Art

[0004] Circuit arrangements with high frequency HF power amplifiers, radio frequency RF power amplifiers and / or millimeter wave power amplifiers are known. For example, HF signals, RF signals and / or millimeter wave signals can be fed to antenna elements of an antenna array. The antenna elements can form an antenna array together with other antenna elements. The antenna array can be used for beamforming in, for example, communication applications or positioning applications. The circuit arrangement can be controlled, for example, by a digital processor such as a digital signal processor (DSP) that can generate a digital input signal, which is amplified by a power amplifier after being converted into an analog signal.

[0005] To minimize power consumption, efficiency should be high. However, for power amplifiers, improving efficiency often reduces linearity, thereby causing amplitude distortion and / or phase distortion. For example, within certain ranges of input signal values, the amplified signal may saturate, thereby losing linearity and increasing distortion. Therefore, improvements in efficiency are usually achieved at the expense of linearity and quality.

[0006] An attempt may be made to counter these impairments by using feedback-based predistortion techniques. The analog signal at the output of the HF power amplifier, RF power amplifier and / or millimeter wave power amplifier may be converted to a digital version that is fed back to the processor and subtracted from the digital input signal. Feedback-based predistortion techniques may thus be operated to condition (predistort) the digital input signal so that even after saturation, the overall desired linearity is obtained.

[0007] This digital feedback-based predistortion technique requires a complex feedback function that must perform a subtraction in real time for each value of the amplified output signal. One instance of the feedback function is required for each antenna element of the antenna array: accordingly, 64 antenna elements require 64 instances of the feedback function. Therefore, performing the online subtraction at the processor requires a large amount of processing power.

[0008] Feedback-based techniques that perform a single digital predistortion function for multiple amplifiers have been attempted. However, it is generally not possible to ensure that all amplifiers are subjected to the same distortion. Therefore, using a single digital predistortion for multiple different amplifiers inherently results in incomplete predistortion for at least some of the amplifiers. However, even if the efficiency improvement is very small, every 1% is valuable because the power consumption benefits are compounded over the entire life cycle.

[0009] Furthermore, in case multiple amplifiers are employed (eg when beamforming operations are performed), each feedback should be provided to a single RF-to-digital converter (which may include an analog-to-digital converter ADC), thus implying a complex device.

[0010] US6,356,146B1 discloses a method for measuring an amplifier to generate predistortion parameters. In one example, the method is used for beamforming. In another example, the method uses a splitter to separate an analog signal into a plurality of separate signals. Summary of the invention

[0011] According to an example, a circuit device is provided, which includes an amplifier, a built-in test circuit, and a signal conditioner, wherein the amplifier is used to amplify an analog version of a digital input signal; the built-in test circuit is configured to provide distortion information associated with distortion affecting the amplifier; and the signal conditioner is used to perform feedforward predistortion of the digital input signal in a signal path of the digital input signal according to a predistortion relationship that maps the digital input signal to a predistorted version, wherein the signal conditioner is configured to adjust the predistortion relationship according to the distortion information.

[0012] Therefore, a real-time feedback-based solution is not required.

[0013] According to an aspect, a transmission / reception device is provided, comprising a circuit arrangement and at least one antenna element operatively connected to an amplifier.

[0014] According to one aspect, a method is provided, the method comprising: performing calibration for at least one amplifier to obtain distortion information related to distortion that impairs the at least one amplifier; operating the at least one amplifier by digitally adjusting a digital input signal at the at least one amplifier according to the distortion information obtained during calibration.

[0015] According to one aspect, a non-transitory storage unit storing instructions is provided, and when a processor executes the instructions, the processor performs the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figures 1a to 4 A circuit arrangement according to an example is shown;

[0017] Figure 5 A method according to an example is shown;

[0018] Figure 6 A circuit arrangement according to an example is shown. DETAILED DESCRIPTION

[0019] Figure 1a The basic scheme of an example of a circuit arrangement 100 is shown, comprising at least one amplifier 110. The amplifier 110 may be used, for example, to amplify an analog version 142 of a digital input signal 102 to obtain an analog amplified version 104 of the digital input signal 102. The circuit arrangement 100 may present a digital signal path 108 and an analog signal path 109, which may be separated from each other by a digital-to-RF converter 140 (which may include, for example, a digital-to-analog converter DAC).

[0020] In an example, the digital input signal 102 may be a modulated signal. In an example, the digital input signal 102 may be an HF signal, an RF signal, and / or a millimeter wave signal. In an example, the digital input signal 102 may be an RF signal, an HF signal, or a millimeter wave signal. In an example, the digital input signal 102 may be a millimeter wave signal. In general, along the digital signal path 108, the digital input signal 102 may be processed to generate an input to the power amplifier 110.

[0021] The amplifier 110 may be, for example, an HF amplifier, an RF amplifier and / or a millimeter wave amplifier. The amplifier 110 may be, for example, a power amplifier. An analog amplified version 104 of the digital input signal 102 may be fed, for example, to an antenna, for example an antenna element of an antenna array (such as operating in beamforming).

[0022] For clarity, it is not shown here and can be placed Figure 1a For example, a delay generator may be inserted (eg, upstream or downstream of amplifier 110) to operate in beamforming.

[0023] As such, the amplifier 110 may be subject to undesirable amplitude variations, which tend to degrade linearity. However, even without feedback-based techniques, these variations may be compensated for. In the digital signal path 108 upstream of the amplifier 110, digital processing may be implemented that allows the digital input signal 102 in the digital signal path 108 to be modified without feedback-based techniques and maintain linearity. Specifically, feed-forward pre-distortion may be performed to feed the amplifier 110 with a pre-distorted signal that takes into account the distortion affecting the amplifier 110.

[0024] To implement feedforward predistortion, the digital signal path 108 may include a digital signal conditioner 111, which may process the digital input signal 102 to obtain a digital predistortion version 118 of the digital input signal 102. The digital signal conditioner 111 may be implemented as a functional block in a digital signal processor DSP, for example. The digital signal conditioner 111 may perform feedforward predistortion of the digital input signal 102. The digital predistortion version 118 of the digital input signal 102 may be converted into an analog version 142 (e.g., by a digital to RF converter 140). Thus, the predistorted analog version 142 of the digital input signal 102 may be fed to the amplifier 110.

[0025] The digital signal conditioner 111 may process the digital input signal 102 in the digital signal path 108 to map amplitude information about the digital input signal 102 onto predistorted symbols of a predistorted version 118 of the digital input signal 102. For example, the larger the amplitude of the digital input signal 102, the stronger the predistortion, and / or the smaller the amplitude of the digital input signal 102, the weaker the predistortion. The digital input signal 102 may apply a variable phase shift to the digital input signal 102 such that the predistorted version 118 of the digital input signal 102 has a different phase relative to the digital input signal 102. The digital input signal 102 may apply a variable gain to the digital input signal 102 such that the predistorted version 118 of the digital input signal 102 has a different amplitude relative to the digital input signal 102.

[0026] The pre-distortion at the digital signal conditioner 111 may be based, for example, on distortion information 135 provided by the built-in circuit 140. The distortion information 135 may carry information about the distortion affecting the amplifier 110, the distortion information 135 making it possible to distinguish whether the amplifier 110 is subject to high distortion (thus requiring strong pre-distortion), or whether the amplifier 110 is subject to low distortion or no distortion (thus requiring strong pre-distortion, weak pre-distortion or no pre-distortion, respectively). The distortion information 135 may be obtained, for example, during a calibration (testing) phase, which may be performed irregularly (e.g., at a frequency much smaller than the bandwidth of the digital input signal 102), and which may be performed at intervals of 1 hour (3600 seconds) or more.

[0027] The signal conditioner 111 may operate by converting the digital input signal 102 into the predistorted version 118 according to a predistortion relationship that maps the symbols of the digital input signal 102 to the symbols of the predistorted version 118. The predistortion relationship may be nonlinear. The predistortion relationship may be adjusted according to the distortion information 135. The predistortion relationship may cause the digital input signal 102 to be predistorted by a relatively large amount in the case of relatively large distortion, and / or to be predistorted by a relatively small amount in the case of relatively small distortion. The predistortion relationship may map amplitude information about the digital input signal 102 to the symbols of the predistorted version 118 of the digital input signal 102. The predistortion relationship may map the amplitude information about the digital input signal 102 to a phase shift according to the distortion information 135. The predistortion relationship may map the amplitude information about the digital input signal 102 to a gain according to the distortion information 135. Other mappings are possible.

[0028] In order to obtain the distortion information 135, a calibration (testing) phase may be performed. Figure 1b Shows the use of Figure 1a Possible implementations for calibrating the components. Figure 1b As shown, a test signal injection block can be implemented to generate an analog test input signal 142'. Figure 1b , the test signal injection block is shown as being integrated with the built-in test circuit 140. The analog test input signal 142' can be fed to the amplifier 110. The amplified signal 104" at the output of the amplifier 110 can be input to the detector. Here, the detector is shown as being integrated with the built-in test circuit 140. Therefore, the built-in test circuit 140 can determine the pre-distortion affecting the amplifier 110. For example, if the amplified output signal 104" is significantly different from the analog test input signal 142', high distortion can be determined, and if the amplified output signal 104" is slightly different from the analog test input signal 142', low distortion can be determined.

[0029] Thus, distortion information 135 may provide information regarding distortion based on analog test input signal 142'. For example, distortion information 135 may provide information associated with a difference between analog test input signal 142' and amplified signal 104".

[0030] The test signal injection block may scan through multiple amplitudes of the analog test input signal 142' to obtain different distortion measurements for different amplitudes. Thus, the distortion information 135 may provide information about distortion for different amplitudes of the analog test input signal 142'. Other approaches may be implemented.

[0031] The obtained distortion information 135 can be used to define a predistortion relationship. Amplitude information and / or data associated with the predistortion relationship (e.g., mapping the amplitude of the digital input signal 102 to the sign of the predistorted version 118) can be stored in a lookup table LUT. The LUT can contain functions (which can be non-linear functions) that can be used to map the amplitude information into a phase shift adjustment signal and / or a gain adjustment signal. The LUT can include a symbol table (constellation diagram) and the modification is set according to the distortion information 135.

[0032] After obtaining the distortion information 135, the circuit arrangement 100 may operate as shown in Figure 1. The amplitude information (eg, the version stored in the LUT or another version) may be used by the signal conditioner 111 in the run mode.

[0033] Thus, the circuit arrangement operates in a feed-forward manner, as it does not require continuous feedback from the amplifier 104 .

[0034] Figure 2 A possible implementation of the components of the built-in test circuit is shown and can be instantiated according to Figure 1a and Figure 1b Specifically, Figure 2 An integrated circuit 160 (which may be a radio frequency integrated circuit RFIC) is shown on which built-in test circuits and amplifiers may be mounted. The integrated circuit 160 may include an input port 168 (e.g., from a DSP or another processor that may implement a signal conditioner 111 to obtain a pre-distorted version 118 of the input signal 102) and / or an output port 170 (e.g., toward an antenna element). The RFIC 160 may include an analog phase shifter 166, which may be controlled, for example, under the control of a processor (which may also be a DSP) for phase shifting, for example, for beamforming. The RFIC 160 may include a version of the amplifier 110 (which may be subject to distortion). In some implementations, other analog components 165 (here represented as phase shifters and amplifiers) may be implemented.

[0035] One version of the integrated circuit 160 may include a built-in test circuit 140. The built-in test circuit 140 may include a test signal injection block 182 for generating an analog test input signal 142' to be fed to the amplifier 110. The built-in test circuit 140 may include a detector 180 in a test phase, which may detect an amplified signal 104" obtained downstream from the amplifier 110. The detector 180 may output distortion information 135 obtained, for example, in a test phase (calibration phase). The phase-locked loop PLL block 172 may be used to generate a timing 173, for example, a timing 173 to be used by the test signal injection block 182 and / or the detector 180.

[0036] The built-in test circuit 140 can switch between a test mode (for performing a test phase or calibration phase) and an operation mode (for performing an operation phase). Here, the built-in test equipment BITE mode selector 174 is shown as being selected by controlling a switch 176. When the switch is closed, the built-in test circuit 140 can be in the test mode ( Figure 1b When the switch is open, the built-in test circuit 140 can operate in the operating mode ( Figure 1a )

[0037] Figure 3 A method for implementing a signal conditioner 111 (eg, Figure 1a The signal conditioner 111 may be obtained, for example, using functional elements at the disposal of a processor (e.g., the processor may be a DSP). The signal conditioner 111 may include, for example, a predistortion function 107, which may process the digital input signal 102 to obtain a predistorted version 118 of the digital input signal 102. An amplitude determiner function 120 may be implemented to obtain amplitude information 124 (e.g., amplitude) about a current symbol of the digital input signal 102. The predistortion function 107 may use mapping data 127 provided by a digital signal mapping function 125. The mapping data 127 may instantiate a predistortion relationship, for example, by mapping symbols of the digital input signal 102 into symbols of the predistorted version 118 (e.g., the amplitude information 124 may be mapped into symbols of the predistorted version 118). The signal mapping function 125 may obtain the mapping from the LUT 144. The LUT 144 may contain a relationship between the sign of the signal 102 and its version 112 (or the sign of the signal 102 and the phase shift and / or gain to be applied) based on the distortion information 135 .

[0038] Above for Figure 3 The operation discussed for elements 107, 120 and 125 is typically in the run mode ( Figure 1a ; Figure 2 , with the switch open). During test mode ( Figure 1b ; Figure 2 , with the switch closed), LUT 144 may be populated with data that instantiates the pre-distortion relationship.

[0039] The circuit arrangement need not necessarily comprise a single amplifier: there may be several amplifiers, each subject to a different distortion. Nevertheless, it has been noted that even if a single processor (e.g. a DSP) is used to implement the signal conditioner 111, it is still possible to pre-compensate the distortion of a plurality of amplifiers. Typically, different amplifiers will be subject to different distortions, but each signal may be pre-distorted for each amplifier. In a test mode, the distortion information 135 may be obtained simply by repeating the test phase for each amplifier, so that the distortion information 135 represents a collection of data, each data being for a specific amplifier (e.g. there will be one LUT for each specific amplifier).

[0040] Figure 4 An example of a device 400 (which may be a transmit / receive device) is shown that includes, for example, multiple amplifiers 110 (which may be high frequency HF amplifiers, RF amplifiers, or millimeter wave power amplifiers). Each amplifier 110 may be included in a corresponding branch 408. Typically, different amplifiers 110 are subject to different nonlinear impairments. Each branch 408 may be independently controlled, for example for beamforming. A processor 162 (e.g., a DSP) that may implement a signal conditioner 111 may control each branch 408 and may provide a predistortion signal 142 to each amplifier 110. Each predistortion signal 142 may be processed for a specific amplifier 110 to precompensate for its specific distortion. Thus, the predistortion signals 142 at different branches 408 are typically different from each other. Each of the predistortion signals 142 may be generated by the techniques described above. For each branch 408, a built-in test circuit 140 may be implemented. Thus, each branch 408 may behave as Figure 2 RFIC 160. Distortion information 135 may thereby be provided to DSP 162. DSP 162 may thereby obtain a pre-distortion relationship to be used in the run mode.

[0041] By relying on the present feed-forward technique, each amplifier 110 at each branch 408 is fed with a signal 142 adapted to its specific distortion. It is not necessary to perform a single pre-distortion for all the different amplifiers. Thus, the different distortions affecting different HF power amplifiers, RF power amplifiers and / or millimeter wave power amplifiers are compensated in a one-to-one manner.

[0042] Furthermore, one signal hardware component (eg, DSP, RF to digital converter) may be used for multiple amplifiers.

[0043] Figure 5 A method 500 is shown that may be implemented, for example, using an apparatus such as apparatus 400 .

[0044] It is assumed here that there are N power amplifiers, each of which is associated with an integer i=[0...N-1]. At step 502, the first power amplifier 0 is selected. At step 504, calibration is performed for power amplifier 0, for example, by injecting an analog test input signal 142' into the first power amplifier 0, by detecting the amplified signal 104" output by amplifier 0, and by determining the distortion information 135 associated with amplifier 0 for at least one amplitude of the analog test input signal 142' and updating the LUT (the process can be repeated by scanning the amplitude of the analog test input signal 142' between multiple values, for example, to associate different distortions with different amplitudes). At step 506, the subsequent power amplifier i+1 (e.g., 1) is selected by updating the index i (e.g., an operation such as i++). At step 508, it is checked whether the last power amplifier N-1 has been calibrated. If there are other power amplifiers to be calibrated ("No", i.e., i<N), a new calibration is performed by repeatedly iterating the loop formed by steps 504 to 506.

[0045] If all power amplifiers have been calibrated ("yes", i.e., i=N), a new operation phase can be started. At step 510, the first power amplifier 0 is selected. At step 512, the digital input signal 102 is predistorted, for example, according to the predistortion relationship identified in the calibration (e.g., by retrieving data from the LUT). At step 516, a new power amplifier i+1 (e.g., 1) is selected. If there are other power amplifiers to be selected ("no", i<N), step 514 is called again for the subsequent power amplifiers. If there are no other power amplifiers to be selected ("yes", i=N), it is checked at step 518 whether it is time to perform a new calibration phase. If it is not time to perform a new calibration phase ("no"), a new signal conditioning can be performed by repeatedly iterating the loop formed by steps 512 to 514. If it is time to perform a new calibration phase ("yes"), a new calibration phase is called at steps 502 to 508.

[0046] Figure 6 A circuit arrangement 600 is shown, which may be an example of the circuit arrangement 400, and provides a plurality of output signals 604 for beamforming. A common analog signal 602 (which is an analog version of a digital input signal not shown) is provided by a common signal source 606 (which may be internal or external). The common signal source 606 implements the signal conditioner 111. The common analog signal 602 is split (e.g., by a splitter / combiner 609) into a plurality of analog signals, each of which is fed to a different channel 608 (each channel being connected to a different channel). Figure 64 in , which are not indicated in the text for brevity). Each channel 608 (associated with a corresponding signal path 108) includes an amplifier 610 (110) that may be subject to distortion. Each channel 608 may include a delay generator 619 that may operate in conjunction with the delay generators of other channels to control beamforming.

[0047] In test mode, each channel 608 may be calibrated, for example to determine the necessary predistortion relationship. For example, the techniques discussed above may be used.

[0048] Specifically, in the test mode, the test common analog signal 602' (142') may be injected by the test signal target block 682 (part of the built-in test circuit) instead of the common analog signal 602 instead of the external source 606. The detector 640 (part of the built-in test circuit) may be used to determine the amplified test signal 604', which may be provided to the RF to digital converter (e.g., the RF to digital converter may include an ADC) and to the processor 634 (which may be understood to be used to implement functions such as Figure 2 The detector 180 is a detector and can be part of the built-in test circuit).

[0049] The detector 640 may include an IQ (In-Phase-Quadrature) determiner that may provide a version (which may be analog) of the amplified test signal 604' in IQ space. The IQ determiner may be configured to:

[0050] - multiplying the amplified version of the test signal by a local oscillator (LO) signal to provide an I version of the amplified test signal 604'; and

[0051] - Multiplying a delayed version (delayed by 90°) of the amplified test signal by the LO signal to provide a Q version of the amplified test signal 604'.

[0052] The I and Q versions of the amplified test signal 604' may be converted to digital signals at the RF to digital converter 615 and provided to the processor 634 for use in determining distortion information. Still other types of detectors may be used.

[0053] A DC removal filter 621 may be placed between the signal source 606 and the splitter / combiner 609. A DC removal filter 623 may be placed downstream of each amplifier 610. At least one of the DC removal filters may be a transformer based filter (other types of filters may be provided in other examples).

[0054] The receiving lines 613 may, for example, each be arranged in parallel with a channel 608. For each channel 608, the parallel connection formed by the receiving line 613 and the channel 608 may be connected in series with (eg, downstream of) a corresponding delay generator 619.

[0055] During the calibration (testing phase), the external source 606 may be informed of the distortion information obtained by the processor 634. Thus, the external source 606 may (using the signal conditioner 111) derive a relationship that maps the amplitude of the digital input signal to the sign of the predistorted version of the digital input signal. Thereafter, the predistorted version of the digital input signal may be converted into an analog version 602 and provided to the circuit arrangement 600. In some examples, the external source 606 is integrated with the circuit arrangement 600. The predistortion may be based on the distortion relationship obtained in the calibration phase. The predistortion may be controlled by the common signal source 606.

[0056] Notably, a single RF to digital converter 615 and a single processor 634 are required for multiple amplifiers 610. In each calibration iteration, each channel 608 may be calibrated, but using only a single processor 634 and a single RF to digital converter 615. No feedback based techniques are used.

[0057] Generally, the examples can be implemented as a computer program product with program instructions, which, when the computer program product runs on a computer, are operated to perform one of the methods. The program instructions may, for example, be stored on a machine-readable medium.

[0058] Other examples comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier.

[0059] In other words, an example of the method is, therefore, a computer program having program instructions for performing one of the methods described herein, when the computer program runs on a computer.

[0060] A further example of a method is, therefore, a data carrier medium (or a digital storage medium or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein. The data carrier medium, the digital storage medium or the recorded medium is tangible and / or non-transitory, as opposed to an intangible and transitory signal.

[0061] A further example of a method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein.The data stream or the sequence of signals can be transmitted, for example, via a data communication connection, for example over the Internet.

[0062] Another example comprises a processing device, for example a computer or a programmable logic device, which performs one of the methods described herein.

[0063] Another example comprises a computer having installed thereon the computer program for performing one of the methods described herein.

[0064] Another example comprises a device or system for transmitting (for example, electronically or optically) a computer program for performing one of the methods described herein to a receiver. The receiver may be, for example, a computer, a mobile device, a memory device, etc. The device or system may, for example, comprise a file server for transmitting the computer program to the receiver.

[0065] In some examples, a programmable logic device (e.g., a field programmable gate array) can be used to perform some or all of the functions of the methods described herein. In some examples, a field programmable gate array can collaborate with a microprocessor to perform one of the methods described herein. Generally, the method can be performed by any suitable hardware device.

[0066] The examples described above are merely for illustrating the principles discussed above. It should be understood that modifications and variations of the devices and details described herein will be apparent. Therefore, it is intended that the scope of the pending claims be limited rather than by the specific details presented by the description and illustration of the examples herein.

[0067] In the present specification, the same or equivalent elements or elements having the same or equivalent functions are denoted by the same or equivalent reference numerals even if they appear in different drawings.

Claims

1. A circuit, comprising: a common signal source operative to provide a common analog signal based on a digital input signal; a plurality of amplifiers operative to amplify separate signals that are separate signal versions of the common analog signal; a built-in test circuit operative to generate distortion information related to distortion affecting the plurality of amplifiers by inputting test signals at different amplitudes to the plurality of amplifiers; and a radio frequency to digital converter connected to the plurality of amplifiers and operative to convert a respective amplified test signal obtained from each amplifier in a test mode, wherein the common signal source is operative to implement a signal conditioner that performs feed-forward predistortion of the digital input signal in a signal path of the digital input signal according to a predistortion relationship that maps the digital input signal onto a corresponding predistortion signal derived from the distortion information, wherein the signal conditioner is operative to adjust the predistortion relationship based on distortion information provided over time by the built-in test circuit, wherein the circuit is operative to switch between the test mode and the operating mode to measure distortion and generate the distortion information in the test mode and to determine a relationship mapping the digital input signal onto a separate predistortion signal version of the digital input signal, wherein each of the plurality of amplifiers is individually controlled according to the predistortion relationship, wherein the built-in test circuit is further operative to repeat a plurality of test iterations to measure the distortion of the amplifier for one of the plurality of amplifiers in each test iteration and determine the pre-distortion relationship, wherein the corresponding predistortion signal is applied as a feedforward predistortion signal to a corresponding amplifier of the plurality of amplifiers without feedback, wherein the built-in test circuit includes a test injection block operative to inject a test signal of a selected amplitude to measure distortion at outputs of the plurality of amplifiers for the test signal, and The signal conditioner is operated to predistort the digital input signal by a relatively large amount when the amplitude of the digital input signal is relatively large, and to predistort the digital input signal by a relatively small amount when the amplitude of the digital input signal is relatively small.

2. The circuit according to claim 1, wherein The predistortion relationship maps amplitude information of the digital input signal to predistortion symbols of a corresponding predistortion signal of the digital input signal.

3. The circuit according to claim 1, in, the signal conditioner being operative to apply a variable phase shift to the digital input signal according to the predistortion relationship, The signal conditioner is operated to adjust the pre-distortion relationship according to the distortion information, so that the pre-distortion relationship maps the amplitude information of the digital input signal to the phase shift according to the distortion information.

4. The circuit according to claim 1, in, the signal conditioner being operative to apply a gain to the digital input signal according to the predistortion relationship, The signal conditioner is operated to adjust the pre-distortion relationship according to the distortion information, so that the pre-distortion relationship maps the amplitude information of the digital input signal to the gain according to the distortion information.

5. The circuit according to claim 1, wherein: The predistortion relationship is non-linear.

6. The circuit according to claim 1, wherein: The signal conditioner operates to apply the predistortion relationship such that: In the case of relatively large distortion, pre-distorting the digital input signal by a relatively large amount; and In the case of relatively small distortion, the digital input signal is pre-distorted by a relatively small amount.

7. The circuit of claim 1, further comprising an integrated circuit on which each of the plurality of amplifiers and the built-in test circuit are mounted.

8. The circuit according to claim 1, wherein: The signal conditioner operates to map the amplitude of the digital input signal to the corresponding predistortion signal via a lookup table.

9. The circuit according to claim 8, wherein The lookup table is a constellation diagram of symbols.

10. The circuit of claim 1, wherein: The signal conditioner is operative to map different amplitudes of the digital input signal to the corresponding predistortion signal via a lookup table.

11. The circuit according to claim 1, wherein: The signal conditioner is operative to map the amplitude of the digital input signal to phase shift adjustment information and gain adjustment information for generating a corresponding predistorted signal when the built-in test circuit is disabled.

12. The circuit of claim 1 , further comprising: A plurality of antennas are driven by the plurality of amplifiers, and the plurality of antennas support beamforming.

13. A transmission / reception device comprising a circuit according to any one of claims 1 to 12 and a plurality of antenna elements operatively connected to an amplifier.

14. A method for beamforming, the method comprising: performing calibration on each of the plurality of amplifiers by inputting a test signal at different amplitudes; obtaining, by said calibration, distortion information related to distortion impairing said plurality of amplifiers; receiving a digital input signal; Mapping the digital input signal to corresponding pre-distortion information through the distortion information; applying the corresponding predistortion information to a received digital input signal, the corresponding predistortion information conditioning the received digital input signal to produce a conditioned signal; as well as inputting the regulated signal into the plurality of amplifiers for amplification, The method further comprises: injecting test signals of different amplitudes into a first amplifier of the plurality of amplifiers during calibration by means of a test injection block, wherein the first amplifier amplifies the test signal; measuring distortion at an output of the first amplifier for test signals of different amplitudes, and generating the distortion information based on the output of the first amplifier for test signals of different amplitudes. wherein the method further comprises generating the distortion information as mapping information, the mapping information mapping a corresponding amplitude of the test signal to a corresponding predistortion associated with the first amplifier at a corresponding amplitude, Wherein, mapping the digital input signal to the corresponding pre-distortion information comprises mapping the amplitude of the digital input signal to the corresponding pre-distortion information, and Therein, the method further comprises applying the predistortion information as a feed-forward adjustment to the digital input signal.

15. The method according to claim 14, wherein: Performing the calibration includes calibrating the plurality of amplifiers periodically over time.

16. The method of claim 14, further comprising applying the conditioned signal as a feed-forward predistortion signal to an amplifier of the plurality of amplifiers without feedback.

17. Computer-readable storage hardware having instructions stored thereon, which instructions, when executed by computer processor hardware, cause the computer processor hardware to perform the method according to any one of claims 14 to 16.

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