WO2024074852A1 - Analog front end for massive multiple input, multiple output (mmimo) communication systems - Google Patents

Abstract

An analog front end unit employs at least two power amplifiers (PAs) and at least two low-noise amplifiers (LNAs). Each PA receives a signal for transmission, at least one which is a digitally pre-distorted signal, and at least one of the signals for transmission supplied ac input to one of the PAs is adjusted so that the phase and/or amplitude of the signals output by the PA and another PA are identical. The outputs of the PAs may be supplied to antenna feeds. In the receive direction, each of the LNAs is fed with a receive signal. At least one of the received signals is adjusted so that when amplified by one of the LNAs the output of the LNA is identical in phase and/or amplitude to the output of at least one of the other LNAs. The outputs of the LNAs are combined.

Description

ANALOG FRONT END FOR MASSIVE MULTIPLE INPUT, MULTIPLE OUTPUT (mMIMO) COMMUNICATION SYSTEMS

TECHNICAL FIELD

[001] This invention relates to wireless communication, and more particularly, to a front end for wireless communication systems that are considered to be massive multiple input, multiple output (mMIMO) systems.

BACKGROUND

[002] Massive multiple input, multiple output (mMIMO) technology, is considered, as of this writing, as typically employing 16 antennas or more for wireless communication, whereas most commonly used are arrays of 32 antennas. Other, higher numbers of antennas, e.g., 64, may also be employed. Massive MIMO, by using a large number of antennas is able to support two or more users at one time instant, using the same frequency, which may be achieved by pointing an individual beam at each user. mMIMO is expected to be a major contributor to the expected success of fifth generation wireless technology (5G) as it promises to provide better exploitation of the space dimension in service of increasing wireless network capability. Herein, the term 5G is meant to refer to the current generation of mobile networks as specified by the International Telecommunications Union-Radio communications sector (ITU-R) and/or the 3rd Generation Partnership Project (3GPP), which is well known to those of ordinary skill in the art.

[003] mMIMO systems require an analog front end (AFE) unit to provide amplified signals for transmission to the antennas and to amplify received signals from the antennas. In the transmit direction, each AFE unit amplifies the signal it receives that is to be transmitted. These signals have already been upconverted from baseband to the frequency of interest for transmission. Each AFE unit then supplies the amplified signal it produced to one antenna element (AE) of an antenna array, which is an array of M antenna elements, each of which is also referred to herein simply as an antenna, e.g., via a respective antenna feeding port. As such, there may be a bank of AFE units that is made up of M individual AFE units.

[004] To this end, each AFE unit contains a power amplifier to amplify the signal for transmission that is supplied to the antennas coupled to the AFE unit. The power amplifier is typically a high-power amplifier that has at least a portion thereof that is not linear in amplitude and may also introduce a phase change. Since it is desirable to use as much of the range of the power amplifier as possible, digital pre-distortion (DPD) is employed to modify the input to the power amplifier to provide for an effective linear operation of the power amplifier, i.e., to reduce the distortion created by running the power amplifier in any nonlinear regions. DPD is a cost- effective linearization technique which aims to provide improved linearity, better efficiency, and to take full advantage of the power amplifier. DPD is typically achieved by modifying an original signal for transmission to produce the signal supplied to the power amplifier using modification values from a look up table which are used to modify the original signal for transmission. The lookup table is developed based on feedback of the output of the high-power amplifier as compared to what is supplied thereto as input.

[005] More specifically, DPD may use the look-up table (LUT) to properly distort the original signal for transmission, the resulting distorted signal being the signal actually supplied to the high-power amplifier. Such distorted signal, i.e., the output of the DPD, is generated so that when it is supplied to the high-power amplifier the signal output by the high-power amplifier is expected to be a linearly amplified version of the original signal for transmission, i.e., prior to undergoing DPD.

[006] In addition, in the receive direction, each AFE unit amplifies signals received by the at least one antenna coupled to it. Individual AFE units may be coupled to more than one antenna which may be connected together to one feeding port, e.g., as noted above. Because the received signal may be weak, e.g., received from a distant transmitter with limited power, a low-noise amplifier (LNA) is typically used so that minimal noise is added to the weak received signal, which may already be close to the level of noise.

[007] Typically, 5G systems operate in a time division duplex (TDD) fashion, so that they transmit during a first time period and then receive during a second, subsequent time period, where the first and second time periods alternate. As such, the analog front end unit includes a switch to switch from transmit mode to receive mode and vice versa. While such a switch may have various operating modes, the primary function is to couple the amplified signal for transmission from the power amplifier to the one or more antennas coupled to the front end unit, e.g., via a feeding port, during the first time period and to couple the antennas to a low-noise amplifier during the second time period. [008] Disadvantageous^, the power amplifiers of the prior art, in order to provide the necessary power, have a high cost. Similarly, high quality LNAs are costly.

SUMMARY

[009] A summary of several example embodiments of the disclosure follows. This summary is provided for the convenience of the reader to provide a basic understanding of such embodiments and does not wholly define the breadth of the disclosure. This summary is not an extensive overview of all contemplated embodiments and is intended to neither identify key or critical elements of all embodiments nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later. For convenience, the term “some embodiments” or “certain embodiments” may be used herein to refer to a single embodiment or multiple embodiments of the disclosure.

[0010] Certain embodiments disclosed herein include an analog front end for a wireless system for at least amplifying a signal for wireless transmission via at least two antennas. The analog front end comprises: a splitter receiving an input signal for amplification by the analog front end and producing at least two copies thereof; a plurality of power amplifiers, each of the power amplifiers amplifying a respective version of one of the at least two copies produced by the splitter to produce as output amplified output versions thereof, wherein the input signal to the splitter is based on an upconverted signal for transmission which is developed, responsive to a feedback signal derived from at least one of the power amplifiers, so that each of the power amplifiers appears to be operating substantially linearly across an operating range even though the operating range for at least one of the power amplifiers contains at least one nonlinear operating region; and at least one harmonizer, each of the at least one harmonizer being interposed between the splitter and a respective one of the power amplifiers, each harmonizer being adapted to adjust a phase of at least one of the at least two copies produced by the splitter so as to provide one of the respective versions amplified by one of the power amplifiers, wherein the phase is adjusted by each of the at least one harmonizer so that the amplified output versions of each of the power amplifiers are substantially identical in phase.

[0011] Certain embodiments disclosed herein include an analog front end for a wireless system for at least developing a received wireless transmission via at least two antennas. The analog front end comprises: a plurality of low-noise amplifiers, each low-noise amplifier of the plurality adapted to receive a respective analog electrical signal representative of a version of a received signal and supplying as an output an amplified version of its received input; and at least one harmonizer, each of the at least one harmonizer receiving a respective one of the analog electrical signals and being configurable to adjust at least one of a phase and an amplitude of its respective received one of the analog electrical signals and to supply the adjusted received analog electrical signal as an output to a respective corresponding one of the low-noise amplifiers to which the harmonizer is coupled, the adjustment made being such that an output of each of the low-noise amplifiers to which one of the at least one harmonizer is respectively coupled is substantially identical to an output of at least one of the other low-noise amplifiers at a same time.

[0012] Certain embodiments disclosed herein include a method for operating an analog front end unit comprising at least two power amplifiers in a transmit mode, the method comprising: performing digital pre-distortion on a signal for transmission to produce a pre-distorted signal for transmission, the pre-distorted signal for transmission being such that when supplied to each of the power amplifiers each power amplifier appears to be providing a substantially linear gain with respect to the signal for transmission across an operating range even though the operating range for at least one of the power amplifiers contains at least one nonlinear operating region; supplying a version of the pre-distorted signal for transmission to each of the power amplifiers, wherein at least one version of the pre-distorted signal for transmission supplied to a respective one of the power amplifiers is supplied via a harmonizer that is adapted to adjust a phase of the at least one version of the pre-distorted signal for transmission; and adjusting the harmonizer so that at least one of the power amplifiers that receives a version of the pre-distorted signal for transmission via the harmonizer produces an amplified version thereof that is substantially identical in phase to an amplified version of the pre-distorted signal for transmission produced by at least one other one of the power amplifiers amplifying its received version

BRIEF DESCRIPTION OF THE DRAWING

[0013] In the drawing:

[0014] FIG.1 shows an illustrative portion of a radio unit (RU) arranged in accordance with the principles of the disclosure; [0015] FIG. 2 shows an illustrative flow chart of a process for the calibration and operation of an arrangement such as is shown in FIG. 1 , in accordance with the principles of the disclosure

[0016] FIG. 3 shows a first illustrative loop-back path;

[0017] FIG. 4 shows a second illustrative loop-back path;

[0018] FIG. 5 shows a third illustrative loop-back path;

[0019] FIG. 6 shows a fourth illustrative loop-back path;

[0020] FIG. 7 shows a prior art amplifier employing a noise cancelling network;

[0021] FIG. 8 shows a portion of an analog front unit arranged in accordance with an aspect of the disclosure to employ a form of amplifier noise cancelling network;

[0022] FIG. 9 shows the illustrative AFE unit of FIG. 1 along with illustrative additional components, e.g., a digital front end (DFE) and an up-down converter (UDC), for use in performing the DPD, in accordance with the principles of the disclosure;

[0023] FIG. 10 shows a schematic diagram of an illustrative controller according to an embodiment;

[0024] FIG. 11 shows an illustrative arrangement of the antenna block of FIG.

1 according to an embodiment; and

[0025] FIG. 12 shows an illustrative arrangement of the antenna block of FIG. 1 according to an embodiment.

DETAILED DESCRIPTION

[0026] It is important to note that the embodiments disclosed herein are only examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed embodiments. Moreover, some statements may apply to some inventive features but not to others. In general, unless otherwise indicated, singular elements may be in plural and vice versa with no loss of generality. In the drawings, like numerals refer to like parts through several views.

[0027] In accordance with the principles of the disclosure, an analog front end unit is configured to employ at least two power amplifiers in the transmit mode and/or at least two low-noise amplifiers in the receive mode. Each of the power amplifiers receives a signal for transmission, at least one of the power amplifiers may receive a digitally pre-distorted signal for transmission, and at least one of the signals for transmission is adjusted prior to being supplied as input to one of the power amplifiers so that at least one of the phase and amplitude of the signals supplied as output by that one of the power amplifiers and another of the power amplifiers are substantially identical. The outputs of the power amplifiers may be supplied to antenna feeds, e.g., for transmission by various antenna elements. In the receive direction, each of the low-noise amplifiers is fed with a receive signal, e.g., derived from an antenna feed. At least one of the received signals is adjusted so that when the adjusted receive signal is amplified by one of the low-noise amplifiers the output of that one of the low-noise amplifiers is substantially identical in at least one of phase and amplitude to the output of at least one of the other low-noise amplifiers. The outputs of the low-noise amplifiers are combined and the combined signal may then be further processed. Advantageously, less expensive amplifiers may be employed or more amplification may be achieved as compared to prior art arrangements.

[0028] FIG. 1 shows an illustrative portion of a radio unit (RU) 100 arranged in accordance with the principles of tne disclosure. RU 100 includes analog front end (AFE) unit 110, antenna block 120, and radio frequency (RF) filters 130-1 and 130-2, referred to collectively herein as RF filters 130. AFE unit 110 includes: a) power amplifiers (PAs) 111-1 and 111-2, referred to collectively herein as PAs 111 , b) low-noise amplifiers (LNAs) 112-1 and 112-2, referred to collectively herein as LNAs 112, c) switches 113-1 and 113-2, referred to collectively herein as switches 113, d) splitter 114, e) combiner 115, f) combiner 116, and g) harmonizers (HMs) 117 and 118.

[0029] Power amplifiers 111-1 and 111-2 are power amplifiers used in the transmission of wireless signals. At least one of PAs 111 , and typically both, has a nonlinear region which is desired to be exploited to make the maximum use of the power amplifiers. As such, digital pre-distortion (DPD) may be utilized in connection with PAs 111 so as to effectively linearize more of the operating region of PAs 111. In addition, PAs 111 may each be of lower cost and provide less amplification than PAs used in prior art arrangement that employ only a single PA. Alternatively, PAs 111 may have the same power as power amplifiers used in prior art arrangement which will result in the instant system having more power than prior art solutions. Although only two PAs 111 are shown, it will be readily recognized that more than two may be employed. In some embodiments, PAs 111 may be identical to all other PAs of PAs 111. However, as will be recognized by those of ordinary skill in the art, PAs 111 and their associated signal paths, even when intended to be identical, will never be precisely identical. Therefore, in accordance with the principles of the disclosure, adjustments to the input signal of at least one of PAs 111 may be made to ensure that the output of each of PAs 111 is substantially identical for any input received on input RF TX supplied as input to splitter 114, e.g., as disclosed hereinbelow.

[0030] LNAs 112 are low-noise amplifiers used in the reception of wireless signals. Although only two LNAs 112 are shown, it will be readily recognized that more than two may be employed. In some embodiments, each of LNAs 112 is intended to be identical to all other LNAs 112 in order to facilitate their outputs being combined by combiner 115. However, as will be recognized by those of ordinary skill in the art, LNAs 112 and their associated signal paths, even when intended to be identical, will never be precisely identical. Therefore, in accordance with the principles of the disclosure, adjustments to the input signal of at least one of the LNAs, e.g., LNA 112- 2, may be made to ensure that the output of each of LNAs 112 is substantially identical for any input received from their respective antenna elements of antenna block 120.

[0031] Switches 113 may be set to various states but are primarily employed to route signals either to or from antenna 120, e.g., in accordance with TDD operation. However, switches 112 may also be set into various modes to provide feedback and control for establishing operating parameters for AFE 110, e.g., at startup or on occasion during operation. The operating state of switch 113-1 is controlled by control signal C3 while the operating state of switch 113-2 is controlled by control signal C4. Typically, during a first time period, switches 113 route signals to antenna 120, signals amplified by PAs 111 are routed to antenna block 120, e.g., via RF filters 130. This may be achieved by setting control signals C3 and C4 to a prescribed value, e.g., 1 during the first time period. Typically, during a second time period, signals received at antenna block 120 are routed via switches 113 to LNAs 112, e.g., via RF filters 130. This may be achieved by setting control signals C3 and C4 to a different prescribed value, e.g , 2. Setting control signals C3 and C4 to yet a further prescribed value, e.g., zero, causes the link between each of switches 113 and RF filters 130 to be grounded, thus, effectively, disconnecting switches 113 from FR filters 130. However, due to leakage, some signal from PAs 111 will pass through switches 113 and on to LNAs 112. This allows for a sort of a loopback providing feedback of what is being output by PAs 111 , which may be employed in calibration of harmonizer 118 as explained further hereinbelow, e.g., at startup or on occasion during operation. [0032] Splitter 114 receives a signal for transmission, RF_TX, as an input. Splitter 114 has several modes of operation, the particular mode in which splitter 114 114 operates is based on control signal C1 . In a first mode, splitter 114 supplies the signal for transmission, RF TX, only to PA 111-1. In a second mode, splitter 114 supplies the signal for transmission, RF TX, only to PA 111-2. In a third mode, splitter 114 splits the signal for transmission, RF_TX, into at least two copies and supplies one of the at least two copies to PA 111 -1 while another of the at least two copies is supplied to harmonizer 117.

[0033] In some embodiments, splitter 114 may be implemented as a power splitter. Such a splitter employs a transformer-based configuration that is well known in the art and operates on differential input and output signals. In some embodiments, splitter 114 is implemented as a Wilkinson splitter, which is a configuration well known in the art, and splitter 114 operates on single-ended input and output signals. As is well known, both such embodiments employ one input amplifier and two parallel output amplifiers, e.g., as drivers.

[0034] Combiner 115 receives as inputs the signals from each of LNAs 112, e.g., RF_RX1 and RF RX2, and combines or selects them and supplies the result as output RF_RX. In some embodiments, combiner 115 may employ a power combiner. In this regard, combiner 115 has several modes of operation, the particular mode in which combiner 115 operates is based on control signal C2, which employs a different respective prescribed value to indicate each respective mode. In a first mode, combiner 115 supplies the signal received from LNA 112-1 , RF_RX1 , as its output RF_RX. In a second mode, combiner 115 supplies as output RF RX the signal received from LNA 112-2, RF RX2. In a third mode, combiner 115 supplies as output RF RX the addition of the signals RF_RX1 and RF_RX2 which are received from each of LNA 112-1 and LNA 112-2, respectively.

[0035] Combiner 116 receives as its inputs signals representing the amplitude and phase of the outputs of each of PAs 111 and supplies an output signal feedback signal FBK, which is put to use in controlling the DPD operations, e.g., to populate a look-up table used therefore, and also to control the operations of harmonizers 117 and 118. The mode of operation of combiner 116 is based on control signal C5, which employs a different respective prescribed value to indicate each respective mode. In a first mode, combiner 116 passes a signal sensed from PA 111-1 to output FBK. In a second mode, combiner 116 passes a signal sensed from PA 111-2 to output FBK. In a third mode, combiner 116 passes the addition of the signals sensed from PA 111 -

1 and PA 111-2 to output FBK. In practice, this may really mean taking the average of the two senses signals which is used to for the DPD to achieve effective linearity for each of PAs 111.

[0036] In one embodiment at least one of the signals inputs to combiner 116 other than control signa) C5, e.g., the respective signals sensed from PA 111-1 or 111-2, may be obtained via inductive coupling from each of the respective paths connecting PAs 111 to switches 113. This is possible because the signal at the output of each of PAs 111 is very strong. Thus, there may only need be a wire or trace run along each of the links from each of the respective paths connecting PAs 111 to switches 113. Operation of combiner 116 will be described further hereinbelow.

[0037] Harmonizer 117 is employed to make sure that PA 111 -1 and PA 111 -2 effectively function in a substantially identical manner. How this is achieved will be described further hereinbelow.

[0038] Harmonizer 118 is employed to make sure that LNA 112-1 and LNA 112-

2 effectively function in a substantially identical manner. How this is achieved will be described further hereinbelow.

[0039] In a first embodiment, antenna block 120 contains N antenna elements, N being an integer greater than 1 , where N determines a beamforming gain and a beam width. The N antenna elements are organized as two subarrays of N/2 antenna elements per subarray. To this end, a passive 1-to-N/2 splitter/combiner for each of RF filters 130 couples each one of RF filters 130 to a respective subarray of N/2 antenna elements, e.g., via a feeding port connected between a respective one of RF filters 130 and a respective one of the subarrays, in the conventional manner. Thus, each subarray has a common feed. All of the antenna elements in every subarray of N/2 antenna elements in antenna block 120 are collectively treated as if they are a single antenna. Each subarray of antenna elements is associated with one of PAs 111.

[0040] FIG. 11 shows an illustrative arrangement according to the first embodiment where antenna block 120 contains N antenna elements arranged into antenna subarrays 122-1 and 122-2, each antenna subarray 122 having N/J antenna elements, where J is the number of power amplifiers, each subarray being fed by a respective one of common feeding ports 131-1 and 131-2 via a respective one of passive, low loss 1 -to-N/2 splitter/combiners 121-1 and 121 -2, so that for FIG. 11 , with N=4 and J-2, each subarray 122 has 2 antenna elements.

[0041] In a second embodiment, when feeding antenna block 120 with the same power as in the above embodiment, in order to have a higher beamforming gain and a narrower beam width, antenna block 120 contains 2xN antenna elements in total organized as J subarrays of N antennas each and a passive 1 -to-N splitter/combiner for each of RF filters 130 which couples each of RF filters 130 to a feeding port connected to N antennas of a subarray. Use of more antennas is desirable given that when the number of antenna doubles there is, in theory, a gain increase of 3 dB. There is also an increase in directionality.

[0042] FIG. 12 shows an i''ustrative arrangement according to the second embodiment where antenna block 120 contains 2N antenna elements, N being the number of antennas in the first embodiment, similarly arranged into antenna subarrays 122-1 and 122-2, each antenna subarray 122 having 2N/J antenna elements, where J is the number of power amplifiers, each subarray being fed by a respective one of common feeding ports 131 -1 and 131-2 via a respective one of passive, low loss 1-to-2N/2 splitter/combiners 121-1 and 121-2, so that for FIG. 12, with N=4 and J=2, each subarray 122 has 4 antenna elements.

[0043] The first embodiment may have a lower insertion loss than the second embodiment because it employs less splitting of the signal being transmitted, and each signal split typically results in insertion loss. The second embodiment may have a slightly higher insertion loss than that of the first embodiment but such loss is more than compensated for by the increase in gain provided by the second embodiment. However, the slightly higher insertion loss will result in practice in the gain increase realized by the second embodiment being actually somewhat less than the aforementioned 3dB.

[0044] In addition, as indicated above, there are tradeoffs to be considered when designing a system, as will be readily recognized by those of ordinary skill in the art. For example, having more RF filters will have a cost implication. However, for example, if the power output is held constant but the number of RF filters is increased and each RF filter is reduced in the power it must handle because of the use of additional PAs, the RF filters may be optimized for the resulting reduced signal power requirement of the signal that must pass through the RF filters in such an embodiment. In other word, some embodiments may employ a larger number of RF filters that are, by their construction, suitable only for reduced signal power but, advantageously, cost less individually, thus possibly reducing the total cost.

[0045] RF filters 130 are filte^rs employed to frequency limit what is supplied as output in the transmit direction from switches 113 or received as input at switches 113 in the receive direction to signals that are desired to be transmitted or received. RF filters 130 thus help prevent interference with other radio devices in neighboring frequencies. These filters, which are well known in the art, are typically custom passive filters that are designed to not attenuate the desired signal nor to introduce noise. In one embodiment, instead of employing RF filters 130 interposed between switches 113 and antenna block 120, an RF filter may be interposed between each of PAs 111 and its respective corresponding one of switches 113 and also, similarly, between switch 113-1 and LNA 112-1 and between switch 113-2 and harmonizer 118.

[0046] Advantageously the arrangement of FIG. 1 allows the doubling of the analog part of the radio unit without increasing the number of up-down converters employed and without requiring a change to the digital operations of the system. Further advantageously, the disclosed arrangements allow for the complexity of 16 antennas while delivering the power of 32 antennas or allow for the complexity of 32 antennas while delivering the power of 64 antennas, and so forth. In addition, the disclosed arrangement can be implemented at quite a lower cost than prior art arrangements. Furthermore, LNAs 112 may be integrated into a radio frequency integrated circuit, (RFIC) which, in the prior art, is an integrated circuit that receives and processes the output of the single prior art LNA. Being able to perform such integration using the current disclosure will reduce the cost of the system overall.

[0047] It should also be appreciated that although two PAs and two LNAs are shown in FIG. 1 more than two of one and/or of the other may be employed. For example, an embodiment may include three PAs and three LNAs, i.e., J=3, and in such an embodiment the antenna block would include three 1-to-N/3 splitters.

[0048] FIG. 2 shows an illustrative flow chart 200 of a process for the calibration and operation of an arrangement such as is shown in FIG. 1 , in accordance with the principles of the disclosure. The process may be performed or coordinated by a controller, e.g., controller 1000 (FIG. 10), further described hereinbelow.

[0049]At a high level, generally, the process of FIG. 2 first develops the information necessary for performing DPD in the nonlinear range of PAs 111 using a plurality of strong signals, i.e., high-amplitude signals, that would cause a nonlinear output response by the PAs if not corrected for. Such information is developed for each of PA 111-1 and 111-2. This is shown in steps 202, 203, and 204. The correction, or harmonization factor, to be applied by HM 117 for such high-amplitude signals is thereafter developed as the ratio of the values developed for PAs 111 -1 and 111-2.

[0050] Thereafter, the harmonization factor for at least one signal value in the linear range of PAs 111 is developed in steps 205, 206, and 207. While only a single value, i.e., sample point, in the linear region need be taken, of course, more may be employed at the option of the impiementer. The developed harmonization factor is applied for normal operation in step 208.

[0051] In view of the foregoing, in one embodiment, after development of the DPD and harmonization factor, e.g., during normal operation, only the information developed for DPD for one of the PAs, e.g., for PA 111-1 , may be employed to adjust signal RF_TX even though when RF_TX is split it is also supplied for amplification by at least one other PA, e.g., PA 111-2. When the PAs are substantially identical, they will each be linearized and the difference between their outputs will be small even when only employing the DPD values for just one of the PAs, e.g., PA 111-1. To make the outputs of the PAs actually substantially identical for a given RF TX signal value, the determined harmonization factor is applied by HM 117 to the signal RF_TX received at HM 117 which then supplies an adjusted version to its connected one of the PAs 111 , e.g., PA 111-2, so that the outputs of PA 111-1 and 111-2 become substantially equal. This is indicated in step 208

[0052] Steps 209, 210, and 211 compute the harmonization factor for HM 118 which is applied during normal operation in step 212. This is somewhat simpler since the LNAs, where LNA 112-2 will have its input adjusted so that its output is substantially equal to that of LNA 112-1 at any given time, are lower power amplifiers that are only operated in a linear region. As such, only a single sample point need be taken, although, of course, more may be employed at the option of the impiementer.

[0053]Turning to more specifics, the process is entered in step 201 when it is determined that determination of DPD and harmonization factors should be performed. Typically, such will be done at least at the beginning of operation but it may also be done from time to time during operation.

[0054] In step 202, a plurality of strong signals, i.e., high amplitude signal levels that cause PA 111-1 to operate in its nonlinear region, are sequentially supplied as input signal RF_TX to PA 111-1 via splitter 114. For each such signal, e.g., I, supplied, the development of the value necessary to perform DPD, i.e., correction factor D1(l) necessary to modify the input supplied at RF TX to linearize the output of PA 111 -1 with respect to the signal to be amplified, is performed. To this end, control signal C1 is set so that the operating mode of splitter 114 (FIG. 1) is the first mode in which splitter 114 supplies the signal for transmission, RF_TX to PA 111-1 and control signal 05 is set so that the operating mode of combiner 116 is the first operating mode in which it supplies as output signal FBK the signal sensed from PA 111 -1 . Also, control signals 03 and C4 are set so that SWs 113 are effectively not connected to anything.

[0055] From the values developed, DPD can be performed over the nonlinear region, e.g., using interpolation. The values developed may be stored in a lookup table, e.g., in controller 1000 (FIG. 10), further described hereinbelow.

[0056] Similar to step 202, in step 203 a plurality of strong signals, i.e., high amplitude signal levels that cause PA 111-2 to operate in its nonlinear region, are sequentially supplied as input signal RF TX to PA 111-2 via splitter 114 and HM 117. In one embodiment, the same values that were supplied as input values in step 202 are employed in step 203. To this end, HM 117 is operated in a pass-through mode. For each such signal, e.g., I, supplied, the development of the value necessary to perform DPD, i.e., correction factor D2(l) necessary to modify the input supplied at RF_TX to linearize the output of PA 111-2 with respect to the signal to be amplified, is performed. To this end, control signal C1 is set so that the operating mode of splitter 114 (FIG. 1) is the second mode in which splitter 114 supplies the signal for transmission, RF_TX, to PA 111-2 and control signal C5 is set so that the operating mode of combiner 116 is the second operating mode in which it supplies as output signal FBK the signal sensed from PA 111-2. Also, control signals C3 and C4 are set so that the signals passing through SWs 113 are effectively not connected to anything.

[0057] From the values developed, DPD can be performed over the nonlinear region, e.g., using interpolation. The values developed may be stored in a lookup table, e.g., in controller 1000 (FIG. 10), further described hereinbelow.

[0058] Next, in step 204 the ratio of the values developed in steps 202 and 203 for respective corresponding input values are developed to be used as the harmonization factor HM to be applied by HM 117 when PAs 111 are operated in their nonlinear region. More specifically, for each signal value I for which PAs 111 are operated in their nonlinear region, HM(I) = D1(l) / D2(l) is computed and the values may be stored in a lookup table, e.g., in a controller, to be supplied thereby to HM 117. [0059] The ratio computed is a complex ratio in that it gives a real ratio for amplitude and a phase difference for phase. The resulting value may be represented in polar format. The lookup table may have, for each value, an entry for amplitude and an entry for phase. Thus, there may be a column for amplitudes and a column with corresponding entries for phase.

[0060] In step 205 a weak signal, i.e., a signal level with an amplitude that lets PA 111-1 to operate in its linear region, is supplied as input signal RF_TX to PA 111- 1 via splitter 114. The output of PA 111-1 at FBK, T1, is obtained. To this end, control signal C1 is set so that the operating mode of splitter 114 (FIG. 1) is the first mode in which splitter 114 supplies the signal for transmission, RF_TX, to PA 111-1 and control signal C5 is set so that the operating mode of combiner 116 is the first operating mode in which it supplies as output signal FBK the signal sensed from PA 111-1. Also, control signals C3 and C4 are set so that the signals passing through SWs 113 are effectively not connected to anything. Although more than one value may be employed, given that the supplied signal causes PA 111 -1 to operate in its linear region only one signal value is required.

[0061] In step 206 at least the same weak signal, i.e., a signal level with an amplitude that lets PA 111-2 to operate in its linear region, that was supplied in step 205, is supplied as input signal RF TX to PA 111-2 via splitter 114. The output of PA 111-2 at FBK, 72, is obtained. To this end, control signal C1 is set so that the operating mode of splitter 114 (FIG. 1) is the second mode in which splitter 114 supplies the signal for transmission, RF TX to PA 111-2 and control signal C5 is set so that the operating mode of combiner 116 is the second operating mode in which it supplies as output signal FBK the signal sensed from PA 111 -2. Also, control signals C3 and C4 are set so that the signals passing through SWs 113 are effectively not connected to anything. Although more than one value may be employed, given that the supplied signal causes PA 111-1 to operate in its linear region only one signal value is required.

[0062] Thereafter, in step 207, the ratio of the values developed in steps 205 and 206 for the weak input signal value is developed to be used as the harmonization factor HM to be applied by HM 117 when PAs 111 are operated in their linear region. More specifically, for the linear regions of PAs 111 HM = T1 / 72 is developed and stored to be supplied to HM 117 when PAs 111 are operated in their linear region.

[0063] The ratio computed is a complex ratio in that it gives a real ratio for amplitude and a phase difference for phase. The resulting value may be represented in polar format and may be stored in a memory of the controller.

[0064] In step 208 the previously computed values of HM are supplied to HM 117, e.g., by the controller for use, e.g., during normal operation. In one embodiment, these values may be supplied by the controller based on its knowledge of the signal to be transmitted.

[0065]Turning to the receive direction, step 209 computes the response R1 of a weak test signal at RF_RX1 . This is achieved by supplying a signal to RF TX and setting the various control signals to arrange for a loop by which the signal arrives at combiner 115 from LNA 112-1. Such a path is often referred to as a loop-back path. More specifically, in one embodiment, in which the loop is formed via splitter 114, HM

117, PA 111 -2, SW 113-2, RF filter 130-2, antenna bock 120, RF filter 130-1 , SW 113- 1 , LNA 112-1 , and combiner 115. To this end, control signal C1 is set so that the operating mode of splitter 114 is the second mode in which splitter 114 supplies the signal for transmission, RF_TX, to PA 111-2; control signal C2 is set so that the operating mode of combiner 115 is the first mode, in which combiner supplies the signal received from LNA 112-1 , RF_RX1 , as its output signal RF RX; control signal C3 is set so that SW 113-1 operates to pass a signal received from RF filter 130-1 to LNA 112-1 ; control signal C4 is set so that SW 113-2 operates to pass a signal received from PA 111 -2 to RF filter 130-2; and control signal C5 is set so that combiner 116 operates in its third mode in which combiner 116 passes the addition of the signals sensed from PA 111-1 and PA 111-2 to output FBK. This loop-back path is shown in FIG. 3 as path 330. The value at RF RX is measured, both amplitude and phase, and used as R1.

[0066] Step 210 computes trie response R2 of a weak test signal at RF RX2. This is achieved by supplying a signal to RF_TX and setting the various control signals to arrange for a loop by which the signal arrives combiner at 115 from LNA 112-2. More specifically, in one embodiment, in which the loop is formed via splitter 114, PA 111 -1 , SW 113-1 , RF filter 130-1 , antenna bock 120, RF filter 130-2, SW 113-2, HM

118, LNA 112-2, and combiner 115. To this end, control signal C1 is set so that the operating mode of splitter 114 is the first mode in which splitter 114 supplies the signal for transmission, RF TX, to PA 111-1 ; control signal C2 is set so that the operating mode of combiner 115 is the second mode, in which combiner supplies as output signal RF RX the signal received from LNA 112-2, RF_RX2, as its output RF RX; control signal C3 is set so that SW 113-1 operates to pass a signal received from PA 111-1 to RF filter 130-1 ; control signal C4 is set so that SW 113-2 operates to pass a signal received from RF filter 130-2 to LNA 112-2 via HM 118; and control signal C5 is set so that combiner 116 operates in its third mode in which combiner 116 passes the addition of the signals sensed from PA 111 -1 and PA 111-2 to output FBK. This loop-back path is shown in FIG. 4 as path 430. The value of the signal at RF_RX is measured, both amplitude and phase, and used as R2.

[0067] It is possible in other embodiments to employ a loop-back path that extends only through switches 113 and the signals are not routed through antenna block 120, which is useful for when RF filters 130 and antenna 120 are not connected . More specifically, in one such embodiment, the loopback path for step 209 is formed via splitter 114, PA 111-1 , SW 113-1 , LNA 112-1 , and combiner 115. To this end, control signal C1 is set so that the operating mode of splitter 114 is the first mode in which splitter 114 supplies the signal for transmission, RF_TX, to PA 111-1 ; control signal C2 is set so that the operating mode of combiner 115 is the first mode, in which combiner supplies as output signal RF_RX the signal received from LNA 112-1 , RF RX1 , as its output RF_RX; control signal C3 is set so that ground is connected to the output of SW 113-1 that is coupled to RF filter 130-1 , which results in SW 113-1 operating to pass an attenuated version of the signal received from PA 111-1 to LNA

112-1 , which may in some cases be a leakage current version; control signal C4 is set so that ground is connected to the output of SW 113-2 that is coupled to RF filter 130- 2, which results in SW 113-2 operating to only pass an attenuated version of the signal received from PA 111-2 to LNA 112-2 via HM 118, which should already be close to zero since no signal is being supplied from splitter 114, thus ensuring that, effectively, zero signal is supplied from LNA 112-2 to combiner 115; and control signal C5 is set so that combiner 116 operates in its third mode in which combiner 116 passes the addition of the signals sensed from PA 111 -1 and PA 111 -2 to output FBK. This loop- back path is shown in FIG. 5 as path 530. The value of the signal at RF RX is measured, both amplitude and phase, and used as R1.

[0068] Similarly, for step 210, it is possible in other embodiments to employ a loop-back path that extends only through switches 113 and the signals are not routed through antenna block 120. More specifically, in one such embodiment, the loopback path for step 209 is formed via splitter 114, HM 117, PA 111-2, SW 113-2, HM 118, LNA 112-2, and combiner 115. To this end, control signal C1 is set so that the operating mode of splitter 114 is the second mode in which splitter 114 supplies the signal for transmission, RF_TX, to PA 111-2 via HM 117; control signal C2 is set so that the operating mode of combiner 115 is the second mode, in which combiner supplies as output RF RX the signal received from LNA 112-2, RF RX2, as its output signal RF RX; control signal C3 is set so that ground is connected to the output of SW 113-1 that is coupled to RF filter 130-1 , which results in SW 113-1 operating to only pass an attenuated version of the signal received from PA 111 -1 to LNA 112-1 , which should already be close to zero since no signal is being supplied from splitter 114, thus ensuring that, effectively, zero sigral is supplied from LNA 112-1 to combiner 115; control signal C4 is set so that ground is connected to the output of SW 113-2 that is coupled to RF filter 130-2, which results in SW 113-2 operating to pass an attenuated version of the signal received from PA 111 -2 to LNA 112-2, which may in some cases be a leakage current version; and control signal C5 is set so that combiner 116 operates in its third mode in which combiner 116 passes the addition of the signals sensed from PA 111-1 and PA 111-2 to output FBK. This loop-back path is shown in FIG. 6 as path 630. The value of the signal at RF_RX is measured, both amplitude and phase, and used as R2.

[0069] Note that one loop embodiment may be used for step 209 and another loop embodiment may be used for 210.

[0070] Regardless of which of the embodiments are employed to determine R1 and R2, in step 211 the harmonization factor HM to be applied by HM 118 is computed by determining the ratio of R1 to R2, i.e., HM = R1 / R2. As with the harmonization factor for the transmit direction, the ratio computed is a complex ratio in that it gives a real ratio for amplitude and a phase difference for phase. The resulting value may be represented in polar format and may be stored in a memory of the controller.

[0071] In step 212 the previously computed values of HM are supplied to HM 118, e.g., by the controller for use, e.g., during normal operation. Normal operation of AFE unit 110 then commences.

[0072] During normal operation, control signal control signal C1 is set so that the operating mode of splitter 114 is the third mode in which splitter 114 splits the signal for transmission, RF TX into at least two copies and routes one of the at least two copies to PA 111 -1 while at least one other copy is supplied to harmonizer 117; control signal C2 is set so that the operating mode of combiner 115 is the third mode in which combiner 115 supplies as output signal RF_RX the addition of the signals RF_RX1 and RF_RX2 which are received from each of LNA 112-1 and LNA 112-2, respectively; control signals C3 and C4 alternate between having switches 113 route signals either to or from antenna block 120, so that signals amplified by PAs 111 are routed to antenna block 120, e.g., via RF filters 130 during a first period, e.g., by setting control signals C3 and C4 to 1 and during a second time period, signals received at antenna block 120 are routed via switches 113 toward LNAs 112, e.g., via RF filters 130, e.g., by setting control signals C3 and C4 to 2; and C5 is set so that combiner 116 operates in its third mode in which combiner 116 passes the addition of the signals sensed from PA 111-1 and PA 111-2 to output FBK.

[0073] The process then exits in step 213.

[0074] FIG. 7 shows a prior art amplifier 700 employing a noise cancelling network such as is disclosed in “Thermal Noise Canceling in LNAs: A Review”, Bram Nauta, Eric A.M. Klumperink, Federico Bruccoleri Asia-Pacific Microwave Conference, Dec 2004 - New Delhi, India, which is incorporated by reference as if fully set forth herein. The purpose of prior art amplifier 700 employing a noise cancelling network is to amplify a signal from single source 701 while introducing a minimal amount of noise. The signal from source 701 is supplied to both matching amplifier stage 702 and voltage sensing amplifier stage 703. The respective outputs developed by each of matching amplifier stage 702 and voltage sensing amplifier stage 703 are supplied to combining network 704 which combines them and produces a single amplified output.

[0075] FIG. 8 shows a portion of AFE unit 110 but arranged in accordance with an aspect of the disclosure to employ a form of an amplifier noise cancelling network. In one embodiment, LNA 112-1 is implemented as a matching amplifier stage, such as matching amplifier stage 702 (FIG. 7) and LNA 112-2 is implemented as a voltage sensing amplifier stage, such as voltage sensing amplifier stage 703. Thus, in this embodiment, unlike the earlier described embodiments, LNAs 112 are not intended to be as identical as possible. Combiner 115 is implemented similar to combining network 704 (FIG. 7) but also employing control elements to route the signals supplied to it as described hereinabove. Unlike prior art amplifier 700 employing a noise cancelling network, which only amplified a single source, in FIG. 8 two different sources, source 1 , corresponding to SW 113-1 , and source 2, corresponding to SW 113-2, are to be amplified and combined. To this end, as described hereinabove, in accordance with an aspect of the disclosure, HM 118 is interposed between SW 113- 2 and LNA 112-2. Advantageously, the signals received from SWs 113 are amplified and combined, while the output of LNA 112-2 cancels part of the noise inherent to the output of LNA 112-1.

[0076] FIG. 9 shows illustrative AFE unit 110 of FIG. 1 along with illustrative additional components, e.g., digital front end (DFE) 910 and up-down converter (UDC) 920, that are part RD 100 and are employed for performing the DPD described hereinabove, in accordance with the principles of the disclosure.

[0077] In the transmit direction, DFE 910 receives a baseband signal, BB TX, for transmission. In particular, BB TX is supplied to digital pre-d istortion (DPD) unit 911 which performs the DPD on BB_TX based on stored values, e.g., in a lookup table, as described hereinabove. To this end, DPD 911 is provided with a baseband feedback signal, BB FBK, which is a baseband version of feedback signal FBK that was supplied as an output from combiner 116. The DPD adjusted transmit signal produced as an output from DPD 911 is supplied as an input to upconverter (UP) 921 of UDC 920. Upconverter 921 upconverts the received DPD adjusted signal to the carrier frequency for transmission so as to generate as an output an upconverted version of BB TX, which is signal RF_TX, that is supplied as an input to splitter 114, as described hereinabove.

[0078] In the receive direction, received signal RF RX is supplied to multiplexer (MUX) 923 from which it is supplied to downconverter (DN) 922. Downconverter 922 supplies a downconverted version ^f RF RX to demultiplexer (DEMUX) 912 which in turn supplies as one of its outputs the downconverted version of RF_RX, now at baseband, as output BB RX.

[0079] MUX 923 also receives as an input signal FBK supplied as an output by combiner 116. This signal is an upconverted signal, i.e., at the carrier frequency, because the transmit signals in AFE 110 are all upconverted signals. Signal FBK is supplied as an output by MUX 923 to downconverter 922, which downconverts it to a baseband version, which in turn supplies the baseband version to demultiplexer 912. Demultiplexer 912 supplies as one of its outputs the baseband version received from downconverter 922 as baseband feedback signal BB_FBK to DPD 912 for use as the feedback signal employed to generate the appropriate values, e.g., for the lookup table, to perform the DPD.

[0080] The arrangement of FIG. 9 is able to employ downconverter 922 for both the received signal RF RX and feedback signal FBK because the system is a time division duplexing (TDD) system where transmission takes place during one time while reception takes place during another time. Therefore, signal FBK, which is only generated during transmission is, effectively, not present during reception and signal RF RX is, effectively, not present during transmission. To this end, a controller, not shown in FIG. 9, e.g., controller 1000 (FIG. 10), may be employed to supply necessary control signals, some of which were described hereinabove, and others which may be used to control MUX 923 and DEMUX 912 in accordance with the above explanation, as will be readily recognized by those of ordinary skill in the art.

[0081]To this end, FIG. 10 shows a schematic diagram of an illustrative controller 1000 according to an embodiment. The controller 1000 includes processing circuitry 1010 coupled to memory 1020, optional storage 1030, optional network interface 1040, and control signal generator 1050. In an embodiment, the components of controller 1000 may be commurn natively connected via a bus 1060.

[0082] Processing circuitry 1010 may be realized as one or more hardware logic components and circuits. For example, and without limitation, illustrative types of hardware logic components that can be used include field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), controller-on-a-chip controllers (SOCs), graphics processing units (GPUs), tensor processing units (TPUs), general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), and the like, or any other hardware logic components that can perform calculations or other manipulations of information.

[0083] Memory 1020 may be volatile (e.g., random access memory, etc.), non-volatile (e.g., read only memory, flash memory, etc.), or a combination thereof.

[0084] In one configuration, software for implementing one or more embodiments disclosed herein may be stored in storage 1030. In another configuration, the memory 1020 is configured to store such software. Software shall be construed broadly to mean any type of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code). The instructions, when executed by the processing circuitry 1010, cause the processing circuitry 1010 to perform the various processes described herein.

[0085] Memory 1020 and/or storage 1030 may store various values used to control radio unit 100, digital front end (DFE) 910, and up-down converter (UDC) 920, e.g., any lookup tables.

[0086] Storage 1030 may be magnetic storage, optical storage, and the like, and may be realized, for example, as flash memory or other memory technology, compact disk- read only memory (CD-ROM), Digital Versatile Disks (DVDs), or any other medium which can be used to store the desired information.

[0087] Optional network interface 1040 allows the controller 1000 to communicate with other components of a wireless communication system or a user interface.

[0088] Control signal generator 1050 generates various control signals so as to control radio unit 10, digital front end (DFE) 910, and up-down converter (UDC) 920, e.g., providing control signals C1 , C2, C3, C4, and C5, values for HM 117 and HM 118, and controls for MUX 923 and DEMUX 912 if employed.

[0089] It should be understood that the embodiments described herein are not limited to any specific architecture illustrated herein and that other architectures may be equally used without departing from the scope of the disclosed embodiments.

[0090] The various embodiments disclosed herein can be implemented as hardware, firmware, software, or any combination thereof. Moreover, the software is preferably implemented as an application program tangibly embodied on a program storage unit or computer readable medium consisting of parts, or of certain devices and/or a combination of devices. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (“CPUs”), a memory, and input/output interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU, whether or not such a computer or processor is explicitly shown. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a printing unit. Furthermore, a non- transitory computer readable medium is any computer readable medium except for a transitory propagating signal.

[0091] All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the disclosed embodiment and the concepts contributed by the inventor to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosed embodiments, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

[0092] It should be understood that any reference to an element herein using a designation such as “first,” “second,” and so forth does not generally limit the quantity or order of those elements. Rather, these designations are generally used herein as a convenient method of distinguish^:ng between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements may be employed there or that the first element must precede the second element in some manner. Also, unless stated otherwise, a set of elements comprises one or more elements.

[0093]As used herein, the phrase “at least one of followed by a listing of items means that any of the listed items can be utilized individually, or any combination of two or more of the listed items can be utilized. For example, if a system is described as including “at least one of A, B, and C,” the system can include A alone; B alone; C alone; 2A; 2B; 2C; 3A; A and B in combination; B and C in combination; A and C in combination; A, B, and C in combination; 2A and C in combination; A, 3B, and 2C in combination; and the like.

[0094] Note that wherever a signal that is transmitted from a transmit antenna is referred to, in systems without antennas such phraseology may be considered to refer to signal supplied to a transmit branch. Similarly, the number of transmit branches may be substituted for the number of transmit antennas.

[0095] Likewise, wherever a signal that originates at a receive antenna is referred to, in systems without antennas such phraseology may be considered to refer to a signal arriving at a receive branch. Similarly, the number of receive branches may be substituted for the number of receive antennas.

[0096] Unless otherwise explicitly specified herein, the drawings are not drawn to scale.

[0097] In the description, identically numbered components within different ones of the FIGs. refer to components that are substantially the same.

Claims

CLAIMS What is claimed is:

1. An analog front end for a wireless system for at least amplifying a signal for wireless transmission via at least two antennas, comprising: a splitter receiving an input signal for amplification by the analog front end and producing at least two copies thereof; a plurality of power amplifiers, each of the power amplifiers amplifying a respective version of one of the at least two copies produced by the splitter to produce as output amplified output versions thereof, wherein the input signal to the splitter is based on an upconverted signal for transmission which is developed, responsive to a feedback signal derived from at least one of the power amplifiers, so that each of the power amplifiers appears to be operating substantially linearly across an operating range even though the operating range for at least one of the power amplifiers contains at least one nonlinear operating region; and at least one harmonizer, each of the at least one harmonizer being interposed between the splitter and a respective one of the power amplifiers, each harmonizer being adapted to adjust a phase of at least one of the at least two copies produced by the splitter so as to provide one of the respective versions amplified by one of the power amplifiers, wherein the phase is adjusted by each of the at least one harmonizer so that the amplified output versions of each of the power amplifiers are substantially identical in phase.

2. The analog front end of claim 1 , further comprising a plurality of radio frequency filters, each radio frequency filter receiving as input a respective one of the amplified versions output by the power amplifiers and supplying as an output a filtered version thereof.

3. The analog front end of claim 2, further comprising a plurality of antennas, wherein the output of each of the radio frequency filters is supplied to a respective one of the antennas.

4. The analog front end of claim 2, further comprising a plurality of N antenna elements, N being an integer greater than one; wherein the output of each of the radio frequency filters is supplied to a respective one of a plurality of low-loss splitters, wherein each low-loss splitter of the plurality is coupled to N/J of the antenna elements, wherein J is a number of the power amplifiers, J being an integer greater than one.

5. The analog front end of claim 1 , further comprising a combiner, the combiner receiving an indication of the amplified versions provided as output by each of the power amplifiers and developing therefrom the feedback signal used by each of the at least one harmonizer to adjust the upconverted signal for transmission.

6. The analog front end of claim 1 , wherein at least one of the at least one harmonizer is further adapted to adjust both the phase and an amplitude of the at least one of the at least two copies produced by the splitter, wherein the amplified output versions of each of the power amplifiers are substantially identical in amplitude.

7. The analog front end of claim 6, wherein the at least one of the at least one harmonizer is adapted to adjust both the phase and the amplitude based on the feedback signal.

8. The analog front end of claim 1 , further comprising: a combiner, the combiner receiving as inputs signals representing an amplitude and phase of the amplified output versions produced by at least two of the plurality of power amplifiers, the combiner being controllable configurable to supply as output at different times one of at least (i) each input signal individually received by the combiner and (ii) a combination of at least two of the input signals individually received by the combiner; wherein the feedback signal is based on the output of the combiner.

9. The analog front end of claim 1 , further comprising: a plurality of switches; a plurality of antenna feeds; and a plurality of low-noise amplifiers; wherein each switch of the plurality is coupled to a respective one of the power amplifiers, a respective one of the antenna feeds, and a respective one of the low-noise amplifiers; and wherein each of the switches is controllably operative to route an output of a respective one of the plurality of power amplifiers toward the respective one of the antenna feeds to which it is coupled at one time and to route a signal from the respective one of the antenna feeds to which it is coupled to the respective one of the low-noise amplifiers to which it is coupled at another time.

10. The analog front end of claim 9, wherein each of the plurality of switches is further controllably operative to couple the output of a respective one of the plurality of power amplifiers toward the respective one of the low-noise amplifiers to which it is coupled at yet a further time.

11. The analog front end of claim 1 , further comprising: a digital pre-distortion processor; an upconverter interposed between the digital pre-distortion processor and the splitter; wherein the digital pre-distortion processor receives a baseband version of the signal for transmission and the feedback signal and supplies as an output to the upconverter a gain-linearized version of the baseband version of the signal for transmission based on the feedback signal; and wherein the upconverter receives the gain-linearized version of the baseband version of the signal for transmission and upconverts the gain-linearized version of the baseband version of the signal for transmission to produce the upconverted signal for transmission.

12. An analog front end for a wireless system for at least developing a received wireless transmission via at least two antennas, comprising: a plurality of low-noise amplifiers, each low-noise amplifier of the plurality adapted to receive a respective analog electrical signal representative of a version of a received signal and supplying as an output an amplified version of its received input; and at least one harmonizer, each of the at least one harmonizer receiving a respective one of the analog electrical signals and being configurable to adjust at least one of a phase and an amplitude of its respective received one of the analog electrical signals and to supply the adjusted received analog electrical signal as an output to a respective corresponding one of the low-noise amplifiers to which the harmonizer is coupled, the adjustment made being such that an output of each of the low-noise amplifiers to which one of the at least one harmonizer is respectively coupled is substantially identical to an output of at least one of the other low-noise amplifiers at a same time.

13. The analog front end of claim 12, further comprising a combiner that combines together the outputs supplied by at least two of the plurality of low-noise amplifiers.

14. The analog front end of claim 12, wherein at least two of the plurality of low-noise amplifiers are substantially identical.

15. The analog front end of claim 12, wherein one of the plurality of low-noise amplifiers is a matching amplifier stage that receives its respective analog electrical signal representative of a version of wireless signal without such respective analog electrical signal representative of a version of wireless signal having been adjusted by any of the at least one harmonizer and wherein one of the plurality of low-noise amplifiers is a voltage sensing amplifier stage that receives its respective analog electrical signal representative of a version of wireless signal from one of the at least one harmonizer.

16. The analog front end of claim 12, wherein each respective received signal is received from a respective antenna feeding port.

17. The analog front end of claim 12, further comprising a plurality of N antenna elements, N being an integer greater than one; wherein the input to each of the low-noise amplifiers is supplied via a respective one of a plurality of low-loss combiners, wherein each low-loss combiner of the plurality is coupled to N/J of the antenna elements, wherein J is a number of the low-noise amplifiers, J being an integer greater than one.

18. The analog front end of claim 12, wherein each respective received signal is received wireless from at least one device external to the analog front end.

19. The analog front end of claim 12, further comprising: a plurality of switches; a plurality of antenna feeds; and a plurality of power amplifiers; wherein each switch of the plurality is coupled to a respective one of the power amplifiers, a respective on of the antenna feeds, and a respective one of the low-noise amplifiers; and wherein each switch is controllably operative to route an output of a respective one of the plurality of power amplifiers toward the respective one of the antenna feeds to which it is coupled at one time and to route a signal from the respective one of the antenna feeds to which it is coupled to the respective one of the low-noise amplifiers to which it is coupled at another time

20. The analog front end of claim 19, each of the plurality of switches is further controllably operative to couple the output of a respective one of the plurality of power amplifiers toward the respective one of the low-noise amplifiers to which it is coupled at yet a further time.

21. A method for operating an analog front end unit comprising at least two power amplifiers in a transmit mode, the method comprising: performing digital pre-distortion on a signal for transmission to produce a pre-distorted signal for transmission, the pre-distorted signal for transmission being such that when supplied to each of the power amplifiers each power amplifier appears to be providing a substantially linear gain with respect to the signal for transmission across an operating range even though the operating range for at least one of the power amplifiers contains at least one nonlinear operating region; supplying a version of the pre-distorted signal for transmission to each of the power amplifiers, wherein at least one version of the pre-distorted signal for transmission supplied to a respective one of the power amplifiers is supplied via a harmonizer that is adapted to adjust a phase of the at least one version of the pre-distorted signal for transmission; and adjusting the harmonizer so that at least one of the power amplifiers that receives a version of the pre-distorted signa¹ for transmission via the harmonizer produces an amplified version thereof that is substantially identical in phase to an amplified version of the pre-distorted signal for transmission produced by at least one other one of the power amplifiers amplifying its received version of the pre-distorted signal for transmission.

22. The method of claim 21 , wherein the version of the pre-distorted signal is an upconverted version thereof.

23. The method of claim 21 , wherein the digital pre-distortion is based on feedback received from at least two of the at least two power amplifiers.

24. The method of claim 21 , wherein the digital pre-distortion is based on feedback received from at least one of the at least two power amplifiers operated in its nonlinear operating region.

25. The method of claim 21 , wherein the adjusting performed by the harmonizer is based on feedback received from each of at least two of the power amplifiers when operated in both their nonlinear operating region and in their linear operating region.

26. The method of claim 21 , further comprising: receiving at each one of a plurality of low-noise amplifiers a loop-back version of the amplified version of the pre-distorted signal for transmission supplied by a respective one of the power amplifiers; and adjusting at least one particular version of the received loop-back version so that the output of the one of the low-noise amplifiers receiving the adjusted particular version of the loop-back version has the same phase as the output of at least one other one of the low-noise amplifiers.

27. The method of claim 21 , further comprising: supplying each output produced by each respective one of the power amplifiers to a respective antenna feed.

28. The method of claim 27, further comprising: receiving at each respective one of a plurality of low-noise amplifiers a version of a received signal supplied at each antenna feed, wherein at least one particular version of the received signal is adjusted so that the output of the one of the low-noise amplifiers receiving the particular version of the receive signal has the same phase as the output of at least one other one of the low-noise amplifiers.