Multi-band electronic beam tilt in distributed amplifier antenna array

Abstract

Multi-band electronic beam tilt for distributed amplifier antenna array. A first set of phase adjustment circuits within a low-power first-band RF transmit distribution network applies a first-band electronic beam tilt to a first-band RF transmit signal. A second set of phase adjustment circuits within a low-power second-band RF transmit distribution network applies a second-band electronic beam tilt to a second-band RF transmit signal. A first set of phase-adjusted first-band RF transmit signals is received at a set of RF front end modules that are distributed along an antenna array column. A second set of phase-adjusted second-band RF transmit signals is received at the set of RF front end modules. A set of subarrays of at least one radiating element is distributed along the antenna array column. Each subarray is connected to and positioned substantially adjacent to a corresponding RF front end module of the set of RF front end modules.

Description

MULTI-BAND ELECTRONIC BEAM TILT IN DISTRIBUTED AMPLIFIER ANTENNA ARRAYDESCRIPTION

[0001] The present application is a non-provisional filing of, and claims benefit under 35 U.S.C. § 119(e) from, U.S. Provisional Patent Application Ser. No. 63 / 563,136, filed Mar. 8, 2024. The contents of that application are incorporated herein by reference in their entirety.BACKGROUND

[0002] The present disclosure relates to the field of telecommunications, and more specifically to a distribution of signals for transmission over antenna radiating elements. It may find applications in the field of wireless communications such as 2G / 3G / 4G, LTE, LTE Advanced, and 5G, and the like.

[0003] In wireless base stations, a radio head (also known as a remote radio head or RRH) is a component that is responsible for the radio frequency (RF) transmission and reception functions. The radio head is typically located at the top of a cell tower or distributed throughout a network of small cells, and it plays a key role in the deployment of modem cellular networks. A typical RRH may include 10 Watt amplifiers for generating a high-power RF signal that is then distributed over a coaxial feed network to divide the amplified power amongst a set of antenna elements. The coaxial feed network may also adjust the phase of the divided high- power amplified signals.

[0004] This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present disclosure that are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the systems and methods described herein. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.SUMMARY

[0005] Described herein are wireless radio transmission and reception systems using antenna arrays having two or more distributed amplifier radio frequency (RF) transceiver chains. Amplifying RF signals closer to the radiating elements of an antenna array not only increases the energy efficiency by eliminating signal loss associated with splitting and beamforming of high-power analog RF signals, but in combination with more cost efficient transmit filter structures and easy-to-manufacture modular assemblies provides for more readily adaptablesystem configurations, thereby providing opportunities for adaptable system deployments, making the overall radio signal transmission system more efficient and robust.

[0006] Each distributed amplifier RF transceiver chain is configured to accept a RF transmit signal source, such as a modulated RF signal from an RF integrated circuit (RFIC), that is provided to a low-power RF transmit distribution network for providing the analog RF transmit signal to a plurality of RF front ends comprising power amplifiers, distributed throughout the antenna array. The RF front ends and power amplifiers, in turn, are distributed such that they positioned along a column of radiating elements such that they are substantially adjacent to their associated radiating antenna elements. The transceiver chain of each array also includes RF receive front end components, such as distributed low noise amplifiers, each connected to a respective antenna element and configured to receive an RF signal, amplify it, and provide it to an RF receive combiner network.

[0007] The low-power RF transmit distribution network includes a signal splitter (e.g., a power splitter) to divide signal power from a given input RF signal source to a number of RF outputs (e.g., at least two such outputs, with some embodiments having 5, 7, or 8 or more identical RF outputs) that are used to drive the individual distributed RF power amplifier stages. The low-power RF transmit distribution network include a beamforming network (e.g., a set of phase adjustment circuits) to adjust the phase of the signals being fed to each power amplifier such that the RF signals transmitted from each radiating element create a focused and directional beam, and which may be used to implement an electronic beam tilt. Some embodiments of the low-power RF transmit distribution network may include a buffer amplifier or pre-amplifier prior to signal splitting. The inclusion of a buffer amplifier may depend upon the power level of the input RF signal received from the RFIC or other modulated RF signal source. A buffer amplifier may also be considered to be an element separate from the low-power RF transmit distribution network, that provides a pre-amplified signal to a given low-power RF transmit distribution network.

[0008] Other embodiments are aimed at a receiver apparatus and process. The process includes obtaining a first set of RF receive signals at a first corresponding set of RF distributed amplifier modules distributed along an antenna array column. When summed, this first set of RF receive signals form a combined RF receive signal that may be demodulated at a later stage to extract a desired data signal from a carrier wave. A second set of RF receive signals is obtained at a second corresponding set of RF distributed amplifier modules distributed along the antenna array column. The process then includes applying a firstelectronic beam tilt to the first set of RF receive signals using a first set of phase adjustment circuits within a first-hand RF receive combiner network to generate a first set of phase- adjusted RF receive signals. The process further includes applying a second electronic beam tilt to the second set of RF receive signals using a second set of phase adjustment circuits within a second-band RF receive combiner network to generate a second set of phase- adjusted RF receive signals. By independently imparting phase adjustments to each set of RF receive signals, a unique directional sensitivity is achieved for each set of RF receive signals.

[0009] Each of the distributed RF power amplifiers may take the form of a balanced amplifier, a Doherty amplifier, a feedforward noise cancelling amplifier, an outphasing amplifier, or another suitable amplifier structure(s). Amplification of the individually distributed RF signals substantially reduces signal loss that is otherwise associated with distributing a high-power RF signal from an RF power amplifier through a high-power distribution network such as signal dividers, phase shifters, and associated RF cabling. Each such distributed RF amplifier also includes an output RF bandpass filter to reduce out of band distortion. In some embodiments, the transmit filter structure includes a set of cross-coupled ceramic resonators placed within an enclosure. In some embodiments, each of the distributed RF power amplifiers operates at a common power level. This ensures that distortions introduced at each amplifier are more similar as compared to distortions introduced by like RF power amplifiers operating at different power levels which can improve a global DPD process, if implemented.

[0010] The arrays may take the form of a linear array (aligned vertically or horizontally), generally referred to herein as a “column” of antenna elements, or radiating elements, or an antenna array column, where each element is driven by a separate distributed power amplifier, which is fed by a respective output of the low-power RF transmit distribution network. In some embodiments the radiating elements for two such transceiver chains are associated with sets of cross-polarized radiating elements having an orthogonal orientation (commonly referred to as vertical and horizontal polarizations, or equivalently, as ±45° polarizations), so that a single column within an array comprises two physically overlapping sets of elements, with each set being driven by a separate analog RF signal distributed through its associated low-power RF transmit distribution network. Some embodiments may also be configured to have at least some of the distributed RF power amplifiers drive a group of parallel-connected radiating elements, which form a subarray of antenna elements. In some embodiments, the radiating elements may be used for both transmission and reception, suchas in a time-domain duplexing (TDD) system, or they may use separate radiating elements in a frequency division duplexing (FDD) system.

[0011] Some embodiments include at least one RF transmit observation network configured to obtain and combine observation samples of the outputs of each of the distributed RF amplifiers. The observation samples are obtained from RF signal couplers connected to the outputs of the distributed RF power amplifiers, phase-adjusted to remove phase offsets imposed by the low-power RF transmit distribution network, and combined into a single analog RF observation signal to be fed to an observation receiver within the RF transceiver, such as an RFIC. The observation receiver may then be used to compare the aggregated amplifier output signal samples with the intended transmit signal and perform global digital predistortion (DPD) signal processing on the original RF transmit signal. The RF power amplifiers operate at a common power level, ensuring that the aggregated amplifier output signal samples more closely resemble each individual amplifier observation sample.

[0012] In some embodiments, the overall systems described herein may be assembled from modularized subassemblies, including modularized RF subassemblies comprising distributed RF power amplifiers (each having an associated distributed RF transmit filter subassembly), and having a predetermined number of transmit / receive signal paths (such as two crosspolarized transmit and RF receive signals, referred to herein as 2T2R), or multiple frequency bands (referred to herein as dual-band 2T2R) and being preconfigured according to either a TDD or FDD operational architecture. Each RF subassembly may be configured with a desired arrangement of antenna radiating elements or radiating element subarrays of various dimensions. The modularized RF assemblies may then be configured according to the desired array dimension, the number of desired RF power amplifiers, and of the overall desired power, and connected to respective RF signal sources and receivers through associated properly-dimensioned low-power RF transmit distribution networks, RF transmit observation networks, and RF receive combiner networks.

[0013] Note that the modular aspects of the RF front end architectures described herein may be combined in various ways to achieve higher-dimensional beamforming. That is, a larger array may be formed by combining two or more sets of distributed amplifier RF front end systems in each array column of a multiple column array. For example, a single array column may comprise two separate 2T2R distributed amplifier RF systems to create a 4T4R column. This modularity provides for higher-dimensional digital beamforming in combination with RF analog beam forming (i.e., hybrid beamforming), and including improved electronic tilt.Such systems retain the characteristics of having sets of separate power amplifiers being fed by a low-power RF transmit distribution network for each RF signal path, and may include an associated RF transmit observation network used for global DPD correction within each such RF chain.BRIEF DESCRIPTION OF THE FIGURES

[0014] Fig. 1 depicts a block diagram of a 2T2R distributed amplifier column array driven by a 2T2R transceiver RFIC;

[0015] Fig. 2 depicts one instance of a distributed amplifier RF front end;

[0016] Fig. 3 depicts a block diagram of a TDD 2T2R distributed amplifier column array driven by a 2T2R transceiver RFIC;

[0017] Fig. 4 depicts an RF transmit observation network associated with the low-power RF transmit distribution network;

[0018] Fig. 5 depicts the linearity of a single RF power amplifier used in the distributed amplifier RF transceiver chains and a combined linearity of the set of distributed amplifiers;

[0019] Fig. 6 depicts a block diagram of a FDD 2T2R distributed amplifier column array driven by a 2T2R transceiver RFIC;

[0020] Fig. 7 depicts additional details of the transmit signal circuits of a dual-band 2T2R distributed amplifier column array;

[0021] Fig. 8 depicts additional details of the receive signal circuits of a dual-band 2T2R distributed amplifier column array;

[0022] Fig. 9 depicts two columns of an FDD dual-band 2T2R (combined to create a dualband 4T4R having a total of 8T8R transceiver chains) distributed amplifier column array;

[0023] Fig. 10 depicts embodiments of arrays of various sizes;

[0024] Fig. 11 depicts aspects of a single cavity resonator;

[0025] Fig. 12 depicts aspects of a single ceramic TEOld resonator;

[0026] Fig. 13 depicts a filter assembly suitable for use by each distributed amplifier module of a 2T2R array, having two multi-stage cross-coupled resonator TX filters and two crosscoupled resonator RX filters;

[0027] Fig. 14 depicts a filter assembly suitable for use by each distributed amplifier module of a 2T2R array, having two cross-coupled resonator TX filters;

[0028] Fig. 15 depicts aspects of a modularized RF subassembly;

[0029] Fig. 16 depicts a block diagram of an embodiment described herein;

[0030] Fig. 17 depicts a dual -band distributed amplifier column array with RF receive combiner networks to independently control directional sensitivity of a multi-band RF receive signal;

[0031] Fig. 18 depicts an alternative dual -band distributed amplifier column array with RF receive combiner networks to independently control directional sensitivity of a multi-band RF receive signal;

[0032] Fig. 19 depicts a dual -band dual-polarization distributed amplifier column array with RF receive combiner networks to independently control directional sensitivity of a multiband RF receive signal;

[0033] Fig. 20 depicts a method for band-independent electronic beam tile of two RF transmit signals; and,

[0034] Fig. 21 depicts a method for band-independent electronic directional sensitivity of a multi -band RF receive signal.DETAILED DESCRIPTION

[0035] With respect to Fig. 1, a 2T2R TDD distributed amplifier column array 100 driven by a 2T2R transceiver RFIC 130 will be described, while Fig. 2 shows further details of each 1T1R RF TRX module 200, where each RF TRX element (e.g., each of 122, 129, etc.), contain two such modules 200. Antenna radiating elements 102, 104, 106, 108, 110, 112, 114, 116 are shown configured in a vertical column of cross polarized elements for transmitting two separate RF signals, referred to herein interchangeably as ±45° polarizations and vertical / horizontal (V / H) polarizations. Note that in the particular embodiment of Fig. 1, the top elements 102, 104 and bottom elements 114, 116, each form parallel connected radiating elements (e.g., line 118 carrying V / H RF signals) thereby forming respective subarrays driven by a set of RF power amplifiers, whereas the remaining cross-polarized elements are pairs of single elements (connected, e.g., by line 120 also providing V / H RF connections), each driven by a respective RF power amplifier.

[0036] Array configurations with radiating element subarrays positioned at the upper and / or lower edges of the array may advantageously be used to implement array signal power tapering to reduce sidelobe gratings. The parallel-connected elements may have a 50 / 50%power splitting or may be configured with a 60 / 40% power split (with 40% power provided to elements located at the furthest point of the column (i.e., extreme top and bottom elements). Microstrip transmissions lines, or other equivalent structures, may provide desired power splitting ratios.

[0037] The transmit (DL) and receive (UL) RF signals are split, and combined, respectively, in the RF distribution network 126. The four RF signals (two transmit and two receive) are carried over lines 128 between the RFIC 130 and the RF distribution network 126. The RF distribution network 126 includes (i) at least a pair of low-power RF transmit distribution networks configured to distribute RF transmit signals (e.g., two such transmit signals 202 in a 2T2R configuration) to each of the respective RF power amplifiers 204 / 206 within the RF TRX elements 122, 129, etc., (ii) at least a pair of RF transmit observation networks configured to obtain RF observation signals from the various observation couplers 208, etc., within the RF TRX circuits and combine them into two or more aggregated RF transmit observation signals (e.g., two such observation signals in a 2T2R configuration, also carried over RF connection lines 128 back to observation receivers within the RFIC 130), and, in FDD configurations, (iii) at least a pair of RF receive combiner networks configured to combine RF receive signals from outputs 214 (that is, in TDD operations, the low-power RF transmit distribution networks may also be configured to operate bi-directionally to also combine received RF signals). As will be described more fully below, each of the three distribution network types (RF transmit, RF transmit observation, and RF receive combiner) include respective sets of phase adjustment circuits to adjust the relative phase of each RF signal in the three distribution network types.

[0038] In some embodiments, the low-power RF transmit distribution network may also include a buffer amplifier (not shown) at the input 128 for each transmit signal source to provide sufficient signal to noise ratios (SNRs) of the transmit signals.

[0039] Further with respect to the embodiment of Fig. 2, the distributed RF transmit signal is received at input 202 and is amplified by two stage LD MOS Doherty amplifier 204, 206, whose output is fed to circulator 210, which provides isolation and protection to the amplifier stage 206. The amplified RF signal is then provided to transmit filter 212 to remove out of band distortion components, and filtered signal is then provided to an antenna radiating element(s) over line 224. Uplink received RF signals are obtained from the antenna elements over line 224, processed by receive filter 222, and provide it to LNA 218 and our output on line 214. The LNA 218 may be bypassed using RF switches 216, 220.

[0040] With respect to Fig. 3, further details of an embodiment of a TDD 2T2R distributed amplifier column array driven by a 2T2R transceiver RFIC will be described. The RF IC 346 provides two downlink transmit signals on lines 344 to respective transmit-receive (T / R) switches 334, 336. In the downlink, the transmit signals are split within the distribution network 332 and provided to transceiver modules such as RF front end circuits 306, 348, etc. which in turn drive a cross polarized pair of radiating elements (or parallel-connected radiating element subarrays) from respective filtered outputs (e.g., lines 302, 304). In the embodiment of Fig. 3, the phase rotator circuits 320, 330 are shown contained within the RF front end circuit 306, but for purposes of this description, they may alternatively be considered to be part of RF distribution network 332. In some embodiments the RF distribution network elements, including the phase shifters and the phase shifter controllers, are all located on a single board within the system to eliminate the need for distributing phase shifter control signals to the individual distributed RF front end modules. For uplink signals received from the RF distribution network 332 the phase is adjusted by phase rotators 330, 328 and provided by respective T / R switches 324, 326 to the respective power amplifiers 320, 322. An additional pair of T / R switches 312, 314 route the amplified signals through respective filters 308, 310.

[0041] In the TDD embodiment shown in Fig. 3, the filters 308, 310 are also used to process received signals which are routed by switches 312, 314 to LA circuits 316, 3 / 18, and are then routed to the phase shifters 328, 330 via switches 324, 326.

[0042] In some embodiments, the phase shifters 328, 330 each comprise a set of selectable delay lines of varying length to provide an associated phase delay of the RF signal. It should be noted that because the RF signal phase shifting is being performed on low-power RF signals, a less expensive phase shifter circuit may be used. So-called “handset grade” phase shifters may be used, and may take the form of a set of selectable microstrip transmission paths of varying lengths, rather than more elaborate high-power phase shifters. In particular, phase shifter circuits for high power signals involve considerations and features that ensure the circuit can handle the increased power levels without degradation, distortion, or damage. The components in a high power phase shifter circuit, such as resistors, capacitors, and inductors, need to be selected or designed to handle the increased power levels without overheating or breaking down. Higher power components often have higher power ratings and are built to withstand greater thermal stresses. The materials used in the construction of circuit components should be chosen for their high electrical and thermal conductivity. Thephase shifter circuits for high power applications should also have low insertion losses to minimize power dissipation within the circuit. Furthermore, increased electromagnetic isolation between the input and output ports of the phase shifter is required at higher power levels to avoid issues such as intermodulation distortion. The control mechanisms such as varactor diodes or other tunable components must also be capable of handling the power levels encountered in high power applications. Such designs constraints impose significant additional expense to the phase shifter circuits (i.e., phase adjustment circuits, phase shifters, phase adjusters, and the like).

[0043] In one embodiment, each of the phase adjustment circuits are controlled by a 4-bit control signal to select one of 16 possible delays. Such embodiments can be adjusted during a calibration procedure to remove any relative phase shifts associated with the respective distribution network itself. Such a calibration may be performed once during the manufacturing process or the calibration may be repeated after deployment of the system. The desired calibration phase offsets may be stored in the controller memory. Furthermore, the phase adjustment circuits may be configured to impose additional phase offsets to the respective distributed RF signals, depending on the physical location of the radiating elements within a given column, as well as a desired electronic beam tilt. One such embodiment provides seven discrete down tilt positions. More or fewer tilt settings may be configured according to the number of selectable delay paths, and the magnitude of their respective differential delays, in each phase adjustment circuit.

[0044] Fig. 4 shows a portion of a distributed amplifier radio frequency (RF) transceiver chain 400. The transceiver RFIC 402 shows a downlink RF transmit signal output on line 404 that is provided to an N-way power splitter 408. The outputs of the power splitter 408 are provided to respective 4-bit switched phase adjustment circuits (e.g., 412), the outputs of which are provided to the distributed RF power amplifiers (e.g., 414). In the RF transmit observation network, the outputs of each of the amplifiers are sampled using RF couplers (e.g., 416), and the sampled RF observation signals from the N amplifier paths are processed by additional 4 bit switched delay phase adjustment circuits (e.g., 420), before being combined in the N-way power combiner 410 to form an aggregated RF transmit observation signal (i.e., aggregated RF observation signal, combined RF observation signal, and the like) that is provided to the observation receiver of the RF IC 402 via line 406.

[0045] The RF IC 402 can provide digital predistortion (DPD) of the transmit signal 404 based on the measured characteristics of the aggregated RF transmit observation signalreceived on line 406. The results of the DPD signal processing are shown in Fig. 5, where signal plot 500 shows the raw linearity signal power 502 of a single RF power amplifier in the absence of DPD signal processing. Notably, the side lobe distortion is approximately 30 dB below the signal peak. Graph 550 shows overlaid plots of an amplifier output 504 from first amplifier (Dev 1) generated by a digitally pre-distorted input signal, an amplifier output 506 from a second amplifier (Dev 2) based on a digitally pre-distorted input signal, and a combined power spectrum of the combined amplifier outputs generated from pre-distorted input signals based on DPD algorithm operating on an aggregated RF transmit observation signal, also referred to herein as “global-DPD”. Notably, the out-of-band distortion associated with the combined RF power amplifiers is approximately 50 dB below the signal peak. With respect to Fig. 6, an FDD 2T2R array column 600 is depicted. FDD transceiver modules such as FDD RF front end circuits 602, 604, 606, 608, 610 each provide two uplink receive paths from antenna elements over lines 642 through receive filters 620, 622 and LNA circuits 624, 626 providing received RF signals on lines of 628 and 630 to the RF receive combiner networks. The low-power RF transmit distribution networks provide signals on lines 638, 640 to the distributed RF power amplifiers 634, 636 which are provided to transmit antenna radiating elements over lines 644 after being filtered by transmit filters 631, 632.

[0046] With respect to Fig. 7, a dual-band dual-polarization low-power RF transmit chain 700 will be described. RFICs 702, 750, provide two polarized RF transmit signals in band 1 (Bl-H, Bl-V) and in band 3 (B3-H, B3-V), respectively. Each of these four RF transmit signals are provided to respective low-power RF transmit distribution networks 708a-708d. In some embodiments preamplifiers or buffer amplifiers 706, 734, 754, 772 provide preamplification of the horizontal RF transmit signals on lines 704, 752 and the vertical RF transmit signals on lines 732, 770. Each RF transmit signal is split using power splitters 710, 736, 756, 774 the outputs of which are provided to respective sets of phase adjustment circuits including, for example, sets of phase adjustment circuits 714, 738, 758, and 776. The sets of phase adjustment circuits may be individually calibrated to remove any differential phase variations from the low-power RF transmit distribution network as well as configured to impart additional phase offsets associated with a desired electronic beam tilt. Furthermore, note that the beam tilts imposed for the band one RF transmit signals (Bl-H, Bl-V) may be different than the electronic beam tilt imparted by the sets of phase adjustment circuits operating on band 3 low-power RF transmit signals (B3-H, B3-V). In some cases, as is possible with the provided architecture, each band-polarization pair may receive a unique tilt.

[0047] The various phase-adjusted low-power RF transmit signals are provided to respective RF front end modules 720, 780, each containing four distributed RF power amplifiers 722, 740, 760, 761, and 786, 788, 790, 792 respectively, whose outputs are filtered by transmit filters 724, 742, 762, 763, and 794, 796, 798, 799 respectively. Quadriplexers 726 and 764 combine the dual-band RF transmit signals for transmission via a cross-polarized antenna pair (e.g., radiating element 730) via a horizontal radiating element connected by line 728 and a vertical radiating element connected by line 766. Note that RF front end module 780 is configured to drive parallel-connected horizontal radiating elements and parallel-connected vertical radiating elements within the two pairs of cross polarized radiating elements 782 and 784. The RF front end modules 720 and 780 as well as radiating elements 730, 782, and 784 are positioned within an antenna array column 701.

[0048] As depicted in Fig. 7, and in at least one embodiment, a low-power first-band RF transmit distribution network (e.g., 708a or 708c) comprises a set of first-band phase adjustment circuits (e.g., 714 or 758) collectively configured to apply a first-band electronic beam tilt to a low-power first-band RF transmit signal (e.g., Bl-H or Bl-V) and a low-power second-band RF transmit distribution network (e.g., 708b or 708d) comprises a set of secondhand phase adjustment circuits (e.g., 738 or 776) collectively configured to apply a secondhand electronic beam tilt to a low-power second-band RF transmit signal (e.g., B3-H or B3- V). In the embodiments described here, “collectively” applying a beam tilt refers to the use of individual phase shifters to apply an appropriate time delay for the given signal based on the location of the radiating elements within the array (as well as the desired beam tilt, and array geometries, etc.) In fact, Fig. 7 depicts four low-power RF transmit distribution networks with corresponding sets of phase adjustment circuits, the sets 714, 758, 738, and 776, one set for each of the four RF transmit signals, however a minimal embodiment only requires two sets of phase adjustment circuits such as both sets handling H-polarized signals (i.e., 714 and 738) or both sets handling V-polarized signals (i.e., 758 and 776). Fig. 7 also depicts a set of RF front end modules (e.g., 720 and 780) distributed along antenna array column 701, each RF front end module being configured to receive (i) a respective phase-adjusted first-band RF transmit signal from the set of first-band phase adjustment circuits, and (ii) a respective phase-adjusted second-band RF transmit signal from the set of second-band phase adjustment circuits. RF front end module 720 receives phase-adjusted first-band RF transmit signal 716 and phase-adjusted first-band RF transmit signal 717, whereas RF front end module 780 receives phase-adjusted second-band RF transmit signal 718 and phase-adjusted second-band RF transmit signal 719.

[0049] Fig. 7 also depicts a set of subarrays of at least one radiating element distributed along the antenna array column 701, each subarray being connected to and positioned substantially adjacent to a corresponding RF front end module of the set of RF front end modules. A first subarray comprises radiating element 730 and a second subarray comprises radiating elements 782 and 784.

[0050] At least one embodiment includes only the horizontally polarized signals or only the vertically polarized signals. In at least one embodiment, the low-power first-band RF transmit signal comprises a horizontally polarized signal and a vertically polarized signal, and the low- power second-band RF transmit signal comprises a horizontally polarized signal and a vertically polarized signal. Fig. 7 clearly depicts such an embodiment.

[0051] In at least one embodiment with dual-polarization, each of the at least one radiating element(s) of each subarray comprises a respective cross-polarized antenna pair, and each cross-polarized antenna pair is configured to radiate the horizontally polarized signal of the respective phase-adjusted first-band RF transmit signal, and the horizontally polarized signal of the respective phase-adjusted second-band RF transmit signal, via a first antenna of the cross-polarized pair. Each cross-polarized antenna pair is further configured to radiate the vertically polarized signal of the respective phase-adjusted first-band RF transmit signal, and the vertically polarized signal of the respective phase-adjusted second-band RF transmit signal, via a second antenna of the cross-polarized pair. Both subarrays in Fig. 7 depict such an embodiment. Line 728 feeds a first antenna of the cross-polarized pair (i.e., a first antenna of radiating element 730) and line 766 feeds a second antenna of the cross-polarized pair (i.e., a second antenna of radiating element 730). The parallel wired cross-polarized pairs (i.e., radiating elements 782 and 784) are also fed by band-specific lines.

[0052] In at least one embodiment, the set of subarrays comprises a nominal subarray of N radiating element(s) and a tapering subarray of greater than N radiating elements. In Fig. 7, N=l. The nominal subarray includes radiating element 730 and the tapering subarray includes radiating elements 782 and 784. Other values for N may be selected as depicted in Figs. 9 and 10. Many forms and combinations of nominal and tapering subarrays may be selected based on a desired overall system performance.

[0053] In at least one embodiment, each RF front end module comprises (i) a first-band amplifier configured to amplify the respective phase-adjusted first-band RF transmit signal (e.g., 722 in 720 and 786 in 780), and (ii) a second-band amplifier configured to amplify the respective phase-adjusted second-band RF transmit signal (e.g., 740 in 720 and 788 in 780).However, depicted in Fig. 7, each RF front end module comprises (i) a first-band Flpolarization amplifier configured to amplify a respective phase-adjusted first-hand Flpolarization RF transmit signal, (ii) a second-hand H-polarization amplifier configured to amplify a respective phase-adjusted second-hand H-polarization RF transmit signal, (iii) a first-hand V-polarization amplifier configured to amplify a respective phase-adjusted firsthand V-polarization RF transmit signal, and (iv) a second-hand V-polarization amplifier configured to amplify a respective phase-adjusted second-hand V-polarization RF transmit signal.

[0054] In at least one embodiment, each RF front end module comprises a single wide-band amplifier. In such an embodiment a quadriplexer is used to combine signals from both bands before amplification. A splitter and bandpass filters could be used post-amplification to feed the separate lines to the cross-polarized pairs in the corresponding subarray.

[0055] In at least one embodiment, at least one ceramic resonator element, configured to filter power outside of the first band is connected to an output of a first-band amplifier, and at least one ceramic resonator element, configured to filter power outside of the second band, is connected to an output of a second-band amplifier. In embodiments with dual-polarizations having four amplifiers, at least one ceramic resonator element, configured to filter power outside of the first band is connected to an output of a first-band H-polarization amplifier, at least one ceramic resonator element, configured to filter power outside of the second band, is connected to an output of a second-band H-polarization amplifier, at least one ceramic resonator element, configured to filter power outside of the first band is connected to an output of a first-band V-polarization amplifier, and at least one ceramic resonator element, configured to filter power outside of the second band, is connected to an output of a secondhand V-polarization amplifier.

[0056] In at least one embodiment, each RF front end module comprises a quadriplexer configured to receive and combine an output of a first-band amplifier, and an output of a second-band amplifier. In some embodiments with dual-polarizations having four amplifiers, each RF front end module comprises (i) a H-polarization quadriplexer configured to receive and combine an output of a first-band H-polarization amplifier and an output of a secondhand H-polarization amplifier and (ii) a V-polarization quadriplexer configured to receive and combine an output of a first-band V-polarization amplifier and an output of a secondhand V-polarization amplifier.

[0057] In at least one embodiment, the apparatus further comprises a first-hand buffer amplifier configured to pre-amplify the low-power first-band RF transmit signal and a second-band buffer amplifier configured to pre-amplify the low-power second-band RF transmit signal. In some embodiments with dual-polarizations, the apparatus further comprises a first-band H-polarization buffer amplifier configured to pre-amplify a low-power first-band H-polarization RF transmit signal, a second-band H-polarization buffer amplifier configured to pre-amplify the low-power second-band H-polarization RF transmit signal, a first-band V-polarization buffer amplifier configured to pre-amplify a low-power first-band V-polarization RF transmit signal, and a second-band V-polarization buffer amplifier configured to pre-amplify the low-power second-band V-polarization RF transmit signal. In Fig. 7, buffer amplifier 706 is a first-band H-polarization buffer amplifier, buffer amplifier 734 is a second-band H-polarization buffer amplifier, buffer amplifier 754 is a first-band V- polarization buffer amplifier, and buffer amplifier 772 is a second-band V-polarization buffer amplifier.

[0058] In at least one embodiment, the low-power first-band RF transmit distribution network comprises a first-band power splitter configured to divide the low-power first-band RF transmit signal into a plurality of divided low-power first-band RF transmit signals, and the low-power second-band RF transmit distribution network comprises a second-band power splitter configured to divide the low-power second-band RF transmit signal into a plurality of divided low-power second-band RF transmit signals. In some embodiments with dualpolarizations, the low-power first-band H-polarization RF transmit distribution network comprises a first-band H-polarization power splitter configured to divide the low-power firsthand H-polarization RF transmit signal into a plurality of divided low-power first-band H- polarization RF transmit signals. The low-power second-band H-polarization RF transmit distribution network comprises a second-band H-polarization power splitter configured to divide the low-power second-band H-polarization RF transmit signal into a plurality of divided low-power second-band H-polarization RF transmit signals. The low-power firsthand V-polarization RF transmit distribution network comprises a first-band V-polarization power splitter configured to divide the low-power first-band V-polarization RF transmit signal into a plurality of divided low-power first-band V-polarization RF transmit signals. The low-power second-band V-polarization RF transmit distribution network comprises a second-band V-polarization power splitter configured to divide the low-power second-band V-polarization RF transmit signal into a plurality of divided low-power second-band V- polarization RF transmit signals. In Fig. 7, power splitter 710 is a first-band H-polarizationpower splitter, power splitter 756 is a second-band H-polarization power splitter, power splitter 736 is a first-band V-polarization power splitter, power splitter 774 is a second-band V-polarization power splitter.

[0059] In at least one embodiment with power splitters, each phase adjustment circuit in the set of first-band phase adjustment circuits is configured to receive a corresponding divided low-power first-band RF transmit signal from the first-band power splitter and to impart a respective phase-shift to the corresponding divided low-power first-band RF transmit signal, and each phase adjustment circuit in the set of second-band phase adjustment circuits is configured to receive a corresponding divided low-power second-band RF transmit signal from the second-band power splitter and to impart a respective phase-shift to the corresponding divided low-power second-band RF transmit signal.

[0060] In at least one embodiment with power splitters and dual-polarization, (i) each phase adjustment circuit in the set of first-band H-polarization phase adjustment circuits is configured to receive a corresponding divided low-power first-band H-polarization RF transmit signal from the first-band H-polarization power splitter and to impart a respective phase-shift to the corresponding divided low-power first-band H-polarization RF transmit signal, (ii) each phase adjustment circuit in the set of second-band H-polarization phase adjustment circuits is configured to receive a corresponding divided low-power second-band H-polarization RF transmit signal from the second-band H-polarization power splitter and to impart a respective phase-shift to the corresponding divided low-power second-band H- polarization RF transmit signal, (iii) each phase adjustment circuit in the set of first-band V- polarization phase adjustment circuits is configured to receive a corresponding divided low- power first-band V-polarization RF transmit signal from the first-band V-polarization power splitter and to impart a respective phase-shift to the corresponding divided low-power firsthand V-polarization RF transmit signal, and (iv) each phase adjustment circuit in the set of second-band V-polarization phase adjustment circuits is configured to receive a corresponding divided low-power second-band V-polarization RF transmit signal from the second-band V-polarization power splitter and to impart a respective phase-shift to the corresponding divided low-power second-band V-polarization RF transmit signal.

[0061] In at least one embodiment, each phase adjustment circuit in the set of first-band phase adjustment circuits comprises an N-bit controllable delay and each phase adjustment circuit in the set of second-band phase adjustment circuits comprises an M-bit controllable delay. In at least one embodiment with dual-polarization, each phase adjustment circuit in theset of first-band H-polarization phase adjustment circuits comprises an N-bit controllable delay, each phase adjustment circuit in the set of second-band H-polarization phase adjustment circuits comprises an M-bit controllable delay, each phase adjustment circuit in the set of first-band V-polarization phase adjustment circuits comprises an N-bit controllable delay, and each phase adjustment circuit in the set of second-band V-polarization phase adjustment circuits comprises an M-bit controllable delay. In some embodiments M is equal to N and in other embodiments M is not equal to N. It may be advantageous to have different bit-controllable delay taps for the different bands, but this is not required.

[0062] In at least one embodiment, each first-band amplifier is substantially identical and configured to operate at a first output power level, and each second-band amplifier is substantially identical and configured to operate at a second output power level. In at least one embodiment with dual-polarization, each first-band H-polarization amplifier is substantially identical and configured to operate at a first output power level, each secondhand H-polarization amplifier is substantially identical and configured to operate at a second output power level, each first-band V-polarization amplifier is substantially identical and configured to operate at a third output power level, and each second-band V-polarization amplifier is substantially identical and configured to operate at a fourth output power level.

[0063] In at least one embodiment, the apparatus further comprises a first set of observation couplers connected to outputs of the first-band amplifiers. The apparatus also comprises a first set of observation phase adjustment circuits, collectively configured to remove the firsthand electronic beam tilt, connected to a first-band observation signal combiner. The apparatus also comprises a second set of observation couplers connected to outputs of the second-band amplifiers. The apparatus also comprises a second set of observation phase adjustment circuits, collectively configured to remove the second-band electronic beam tilt, connected to a second-band observation signal combiner.

[0064] In at least one embodiment with dual-polarizations, the apparatus further comprises a first set of observation couplers connected to outputs of the first-band H-polarization amplifiers. The apparatus also comprises a first set of observation phase adjustment circuits, collectively configured to remove the first-band H-polarization electronic beam tilt, connected to a first-band H-polarization observation signal combiner. The apparatus also comprises a second set of observation couplers connected to outputs of the second-band H- polarization amplifiers. The apparatus also comprises a second set of observation phase adjustment circuits, collectively configured to remove the second-band H-polarizationelectronic beam tilt, connected to a second-band H-polarization observation signal combiner. The apparatus further comprises a third set of observation couplers connected to outputs of the first-band V-polarization amplifiers. The apparatus also comprises a third set of observation phase adjustment circuits, collectively configured to remove the first-band V- polarization electronic beam tilt, connected to a first-band V-polarization observation signal combiner. The apparatus also comprises a fourth set of observation couplers connected to outputs of the second-band V-polarization amplifiers. The apparatus also comprises a fourth set of observation phase adjustment circuits, collectively configured to remove the secondhand V-polarization electronic beam tilt, connected to a second-band V-polarization observation signal combiner. Such an embodiment is depicted in Fig. 8.

[0065] In at least one embodiment with observation couplers, the apparatus further comprises (i) a first-band DPD module configured to modify the low-power first-band RF transmit signal and to update a parameter of the first-band DPD module based at least in part on a combined first-band RF observation signal that is obtained from the first-band observation signal combiner, and (ii) a second-band DPD module configured to modify the low-power second-band RF transmit signal and to update a parameter of the second-band DPD module based at least in part on a combined second-band RF observation signal that is obtained from the second-band observation signal combiner.

[0066] In at least one embodiment with observation couplers and dual-polarizations, the apparatus further comprises (i) a first-band H-polarization DPD module configured to modify the low-power first-band H-polarization RF transmit signal and to update a parameter of the first-band H-polarization DPD module based at least in part on a combined first-band H- polarization RF observation signal that is obtained from the first-band H-polarization observation signal combiner, and (ii) a second-band H-polarization DPD module configured to modify the low-power second-band H-polarization RF transmit signal and to update a parameter of the second-band H-polarization DPD module based at least in part on a combined second-band H-polarization RF observation signal that is obtained from the second-band H-polarization observation signal combiner, (iii) a first-band V-polarization DPD module configured to modify the low-power first-band V-polarization RF transmit signal and to update a parameter of the first-band V-polarization DPD module based at least in part on a combined first-band V-polarization RF observation signal that is obtained from the first-band V-polarization observation signal combiner, and (iv) a second-band V- polarization DPD module configured to modify the low-power second-band V-polarizationRF transmit signal and to update a parameter of the second-band V-polarization DPD module based at least in part on a combined second-band V-polarization RF observation signal that is obtained from the second-band V-polarization observation signal combiner. Such an embodiment is depicted in Fig. 8.

[0067] With respect to Fig. 8, a dual-band dual-polarization RF transmit chain with RF transmit observation networks 800 will be described. Samples of each power amplifier output are obtained by couplers (e.g., 816, 838, etc., in RF front end module 820, and 848, 850, etc. in RF front end module 860) connected to the output of each power amplifier. For a given RF transmit signal, the various observation signals are combined at a respective RF transmit observation network in a respective RF observation signal combiner e.g., 810, 834, 844, 846. In Fig. 8, RF observation signal networks 808a-d comprise RF observation signal combiners 810, 834, 844, and 846 respectively, as well as respective sets of phase adjustment circuits.

[0068] The combined RF observation signal from each RF transmit observation network is provided to the respective DPD inputs 804, 832, 840, 842 associated with the RF ICs 802, 840. As one example the combined RF transmit observation signal 804 from signal combiner 810 for band Bl-H Is provided to the DPD-H input of RF IC 802. The RF IC 802 uses an observation receiver to compare the combined RF transmit observation signal to the transmitted RF signal 806. The RF IC 802 will update its DPD algorithm and / or DPD mapping tables based on the comparison. Note also that the phase adjustment circuits 812 through 814 are configured to remove any phase differentials associated with the first-band RF transmit observation network, as well as to remove any intentional phase adjustments imposed by the related low-power first-band RF transmit distribution network for purposes of electronic beam tilt. Note also that the phase adjustment circuits 836 through 837 are configured to remove any phase differentials associated with the second-band RF transmit observation network, as well as to remove any intentional phase adjustments imposed by the related low-power second-band RF transmit distribution network for purposes of electronic beam tilt. In at least one embodiment, each RF observation signal network includes a set of phase adjustment circuits configured to remove electronic beam-tilt phase shifts. In some embodiments, a set of phase adjustment circuits configured to remove electronic beam-tilt phase shifts is substantially adjacent to each RF observation signal combiner.

[0069] Furthermore, as mentioned above the electronic beam tilt angles implemented for band 1 signals may be different than the electronic beam tilt angles implemented for band 3 signals, and the various phase offsets associated with the different electronic beam tilt anglesmay be independently removed by the separate Bl and B3 phase adjustment circuits of the Bl and B3 RF transmit observation networks.

[0070] In embodiments with multiple RF transmit observation networks, each separate RF transmit observation network shall be fed by power amplifiers operating at a common power level associated with that RF transmit observation network. For example, in Fig 8., the power levels of all amplifiers associated with the Bl-H RF transmit observation network shall be substantially identical to each other. The power levels of all amplifiers associated with the Bl-V RF transmit observation network shall be substantially identical to each other. The power levels of all amplifiers associated with the B3-H RF transmit observation network shall be substantially identical to each other. The power levels of all amplifiers associated with the B3-V RF transmit observation network shall be substantially identical to each other. The power levels of amplifiers associated with different RF transmit observation networks need not be substantially identical, as they won’t be summed with each other at a signal aggregator or combiner, but they may be substantially identical in some embodiments.

[0071] In some embodiments, the apparatus comprises a first-band RF transmit observation network that includes (i) a first set of observation couplers connected to outputs of the first plurality of RF distributed amplifier modules, (ii) a first set of observation phase shifter circuits, collectively configured to remove the first applied electronic beam tilt, connected to a first observation signal combiner, and a second-band RF transmit observation network that includes (iii) a second set of observation couplers connected to outputs of the second plurality of RF distributed amplifier modules, and (iv) a second set of observation phase shifter circuits, collectively configured to remove the second applied electronic beam tilt, connected to a second observation signal combiner. The RF transmit observation networks are configured to obtain respective sets of RF transmit observation signals from the sets of observation couplers and to combine each set into respective aggregated RF transmit observation signals. In such an embodiment, electronic beam tilt angles may be independently removed by the separate sets of phase adjustment circuits in the RF transmit observation networks.

[0072] In some embodiments that include a RF transmit observation network, a first DPD module configured to modify the first low-power RF transmit signal and to update a parameter of the first DPD module based at least in part on an aggregated RF observation signal associated with the first set of observation couplers, and a second DPD module configured to modify the second low-power RF transmit signal and to update a parameter ofthe second DPD module based at least in part on an aggregated RF observation signal associated with the second set of observation couplers.

[0073] In at least one embodiment, each RF distributed amplifier module in the first plurality of RF distributed amplifier modules is substantially identical and configured to operate at a first common gain, and each RF distributed amplifier module in the second plurality of RF distributed amplifier modules is substantially identical and configured to operate at a second common gain.

[0074] With respect to Fig 9, a 4T4R FDD dual-band dual column system 900 will be described. The system comprises 2 vertical linear columns 902, 904. Each column comprises cross polarized antenna pairs that are interleaved between transmit and receive antennas. Each RF front end module, including 906, 908, 910, 912, 914, processes dual polarized (V / H) signals in each of two bands (Bl, B3), forming a dual-band 2T2R array. This may be viewed equivalently as a 4T4R array. The receive portion of each RF front end module 920 includes two band one receive filters 922, 929 and two band one LNAs 930, 932, as well as two band three receive filters 926, 928 and two band three LNAs 934, 936. Similarly, the transmit portion of each RF front end module 920 includes two band one transmit filters 938, 939, and two band one distributed RF power amplifiers 942, 944, as well as two band three transmit filters 940, 941, and two band three distributed RF transmit power amplifiers 946, 948.

[0075] Fig. 10 depicts antenna array columns 1000, 1050, 1060, and 1080 that may be formed using the distributed amplifier radio frequency (RF) transceiver chains described above. An RF distributed amplifier module 1016 is configured to produce a respective amplified RF signal with a power level that is substantially equal to the power level produced by the other power amplifiers depicted in Fig. 10. For receive chains a low-noise amplifier may be used. Within distributed amplifier RF transceiver chain 1002 is a RF distributed amplifier module 1016 positioned substantially adjacent to a tapering subarray of cross polarized antennas 1014 and 1020. A band pass filter may be included after a distributed amplifier module, e.g., at connection point 1018, or before the distributed amplifier module. Each distributed amplifier RF transceiver chain is associated with a single RF transmit signal, and a pair of such distributed amplifier configurations may be used to drive a column of cross-polarized antenna elements.

[0076] Within the antenna array column 1000, an RF distributed amplifier module of a set of RF distributed amplifier modules is connected to and positioned substantially adjacent to a nominal subarray of one or more radiating elements at RF distributed amplifier transceiverchains 1006 and 1008. An RF distributed amplifier module of the set of RF distributed amplifier modules is connected to and positioned substantially adjacent to tapering subarrays having more radiating elements than the nominal subarray in RF distributed amplifier transceiver chains 1002, 1004, 1010 and 1012.

[0077] A distribution network includes (i) at least a pair of low-power RF transmit distribution networks configured to distribute RF transmit signals (e.g., two such transmit signals in a 2T2R configuration) to the respective RF power amplifiers within the RF TRX elements, (ii) at least a pair of RF transmit observation networks configured to obtain RF transmit observation signals from the various observation couplers within the RF TRX circuits and to combine them into respective aggregated RF transmit observation signals, and, in FDD configurations, (iii) at least a pair of RF receive combiner networks configured to combine RF receive signals from outputs configured to accept a RF transmit signal source, such as a modulated RF signal from an RF integrated circuit (RFIC), that is provided to a low-power RF transmit distribution network for providing the analog RF signal to a plurality of RF power amplifiers distributed throughout the antenna array. The RF power amplifiers, in turn, shall be distributed along the columns of the example antenna array columns 1000, 1050, 1060, and 1080 such that they are positioned substantially adjacent to their associated radiating antenna elements.

[0078] In Fig. 10., the antenna array column 1050 comprises a centered nominal subarray of one radiating element. Immediately above the nominal subarray is a tapering subarray of two radiating elements. Immediately below the nominal subarray is a second tapering subarray of two radiating elements. At the edges of the antenna array column 1050 are third and fourth tapering subarrays of two radiating elements each.

[0079] In the previously described antenna array column 1050, a nominal subarray is positioned closer to a center of the antenna array column 1050 than at least one tapering subarray. The tapering subarray has a greater number of radiating elements than the nominal subarray. The second, third, and fourth tapering subarrays have the same number of radiating elements as the tapering subarray.

[0080] The antenna array column 1060 comprises two centered nominal subarrays of two radiating elements each. Adjacent to the nominal subarrays and at the top of antenna array column 1050 is a tapering subarray of three radiating elements. At the bottom of antenna array column 1050 is a second tapering subarray that also has three radiating elements.

[0081] In the previously described antenna array column 1060, two nominal subarrays are positioned closer to a center of the antenna array column than the tapering subarray. The tapering subarray has a greater number of radiating elements than the nominal subarray. The second tapering subarray at the bottom has the same number of radiating elements as the tapering subarray at the top.

[0082] In Fig. 10., the antenna array column 1080 comprises a centered nominal subarray of one radiating element. Adjacent to the nominal subarray are two tapering subarrays of two radiating elements each. At the edges of the antenna array column 1080 are two second tapering subarrays of three radiating elements each.

[0083] In the above-described antenna array column 1080, one or more nominal subarrays are positioned closer to a center of the antenna array column than the at least one tapering subarray and the at least one tapering subarray is positioned closer to a center of the antenna array column than the at least one second tapering subarray. The at least one tapering subarray has a greater number of radiating elements than the nominal subarray. The at least one second tapering subarray has a greater number of radiating elements than the tapering sub array.

[0084] A nominal subarray is a subarray with a least number of associated radiating elements in the antenna array column. A tapering subarray is a subarray with a greater number of associated radiating elements than the nominal subarray. Second, third, fourth, etc. tapering subarrays may have equal or varying numbers of associated radiating elements with respect to the tapering subarray. In general, it is preferred, but not required, to maintain reflective symmetry when selecting the positions and number of associated radiating elements for each sub array.

[0085] All the RF power amplifiers are configured to output a common power level. The common power level from each power amplifier is divided evenly across all the radiating elements of the associated subarray. Tapering subarrays are named as such as they will split the common power level across a greater number or radiating elements than nominal subarrays. By sharing the common power level across a greater number of radiating elements, each individual radiating element in a tapering subarray will operate with less power than each individual radiating element in a nominal subarray, thereby achieving tapering of the signal. Various configurations of one or more nominal subarrays and one or more tapering subarrays may be used, as exemplified by Fig. 10. The example antenna array columns 1000, 1050, 1060, and 1080 may each be used to impart tapering across a distributed RF signal.One with experience in the art would understand that other antenna array configurations having at least one nominal subarray and at least one tapering subarray may be used as well.

[0086] In array 1050, individual cross polarized radiating elements within the tapering subarrays each receive 1 / 2 as much RF power when compared to the cross polarized radiating element in the nominal subarray. In array 1060, individual cross polarized radiating elements within the tapering subarrays each receive 2 / 3 as much RF power when compared to individual cross polarized radiating elements in the nominal subarrays. In array 1080, individual cross polarized radiating elements within the top and bottom tapering subarrays each receive 1 / 3 as much RF power when compared to the cross polarized radiating element in the nominal subarray, and individual cross polarized radiating elements within the more central tapering subarrays each receive 1 / 2 as much RF power when compared to the cross polarized radiating element in the nominal subarray.

[0087] Fig. 11 shows a typical resonant cavity filter (or simply, a cavity filter) having a resonator 1104 within a cavity 1102. Cavity filters are a type of electronic filter that uses the resonance of the cavities to achieve a frequency selectivity, typically in the form of a bandpass filter. The cavities are typically formed by metallic walls or surfaces that create a resonant structure. The dimensions of the cavities are designed to resonate at the desired frequency or frequencies. Resonant cavities exhibit a high selectivity for specific frequencies, and the cavities are tuned to resonate at the desired frequency allowing signals close to this frequency to pass through while attenuating signals at other frequencies. The resonance is highly dependent upon the height of the cavity. Cavity filters typically incorporate tuning mechanisms to adjust the resonance frequency. This allows for fine tuning the filter to meet the specific requirements of the application. Multiple resonant cavities are combined in an array to create more complex filters with broader pass bands or improved rejection characteristics. The resonant cavities are combined by providing windows in the cavity walls from one cavity to adjacent cavities. In resonant cavity 1100, note the high current density regions 1108 imposed in the cavity side walls that pass through to the top and bottom of the cavity towards the highest current density 1110 and in particular (“hotspot” regions) 1106, as well as 1112. Resonance of the cavity filter is highly dependent upon the electrical connectivity between the cavity walls and the cavity top and bottom.

[0088] In contrast to the resonant cavity filters, a ceramic resonator 1204 shown in Fig. 12 supported by a passive post element 1206 and placed in an enclosure 1202, demonstrates a frequency selectivity that is primarily a function of the resonator 1204 material, shape, andsize, and is highly independent of the enclosure size and shape. This is due largely to the fact that the enclosure does not form a significant part of the resonating structure. Note the low magnitude of the currents induced in the enclosure sidewalls 1208, 1212, being primarily in the horizontal plane of the resonator 1206, and the very low currents 1214 flowing from the sidewalls to the top or bottom regions 1210.

[0089] In some embodiments, the transmit filters comprise one or more groups of crosscoupled ceramic resonators, where the coupling between resonators is directly between the multiple resonator elements, that is, from each such resonator to each other resonator (i.e., cross-coupled). In such cross-coupled resonator filters, no resonator elements are fully isolated from each other resonator elements. The resonator elements in some embodiments are characterized by a TEO Id resonance mode. The resonator elements may be ceramic discs to provide rotational symmetry for ease of assembly, but other shapes may be used such as square or oblong shapes.

[0090] Cavity filters are only able to achieve couplings to immediately adjacent cavities via openings, or apertures, in the cavity walls between the adjacent cavities, rather than between each cavity of a set of cavity resonators. Unlike cavity resonator filters, the enclosure primarily serves as shield to block external radiation from occurring, and it does not substantially participate in determining the resonance frequency of the resonators. The crosscoupled resonator elements configured as a filter also have signal less loss when compared to cavity filters. The reduced signal loss associated with the direct cross-coupled resonator elements, together with elimination of RF signal loss of the amplified RF signals associated with power distribution (e.g., splitters, phase adjusters, and associated RF cabling networks used to distribute power amplifier output signals to an array of radiating elements) allows some embodiments to use of LDMOS amplifiers rather than GaN-based power amplifiers, which suffer from reduced linearity.

[0091] Fig. 13 depicts a filter assembly 1300 having two TX and two RX filter regions. TX filter regions 1302 and 1304 each comprise three sets of cross-coupled resonators, crosscoupled resonators 1306 - 1310 and 1312 - 1316 respectively, where each set of crosscoupled resonators includes three ceramic resonator elements. Each of the three crosscoupled sets are themselves coupled to an adjacent set through an aperture (e.g., aperture 1318) in the enclosure wall 1320. In the embodiment shown, each of the RX filter regions 1322 and 1324 comprise single sets of three cross-coupled resonators.

[0092] The cross-coupled resonator filters may comprise an array of resonators, including a substantially linear one-dimensional array. “Substantially linear” refers to a set of resonators arranged in a line, where one or more of the resonators may be slightly offset from the line to increase their coupling coefficients to non-adjacent resonator elements further along the array.

[0093] Alternative embodiments may extend to a 2-dimensional array of resonators within a single enclosure. Some embodiments of 2-dimensional arrays include two substantially linear array rows positioned substantially parallel to each other. The resonators within each row may have may include slight offsets to alter the couplings between elements along it's linear set as well as the couplings to resonators in the adjacent row.

[0094] The signal input port and output port to the resonator elements are provided by signal couplers. The filter frequency responses are generally symmetric between ports, and no distinction is necessary between an “input” port and an “output” port. Because signal inputs and outputs are interchangeable in the description, the terms port 1 and port 2 will be used with the understanding that if an input signal is provided at port 1, then port 2 will have the output signal and vice versa. The coupling probes used to couple signals from RF conductors to and from the resonating elements may have a concentric arc that conforms to the curvature of a given resonator element. Input / output coupling probes may be also placed between resonating elements, and the coupling to a specific resonator may be achieved by positioning its arc concentrically around that resonator. Embodiments of the filter having this probe configuration provides a relocation of a transfer function “zero” from the low band to the high band to provide faster roll-off when desired, such as in an FDD embodiment where the transmit and receive frequency bands are immediately adjacent to each other.

[0095] Fig. 14 shows a further embodiment 1400 of two TX filter structures for use in a 2T RF front end module. The sets of cross-coupled resonators each have an enclosure wall 1402, 1404, respectively. A slight variation of the enclosure is shown by enclosure wall 1434, which encloses the set of cross-coupled resonator elements 1420, 1422, 1424, 1426, 1428, and 1430. The enclosure walls may be formed from a single length of a sheet-like metal, such as brass, which is then folded into the desired enclosure shape. Tabs may be provided for alignment of the enclosure during manufacturing. In some embodiments, the enclosure walls may be soldered to the enclosure base using a solder reflow process.

[0096] The TX filters of Fig. 14 comprise two substantially linear rows placed adjacent to each other. Note that resonator element 1424 is slightly offset within the first linear row ofelements 1420, 1422, 1424, 1426, to increase the coupling coefficient to element 1420. In some embodiments, wall extensions may be interposed between resonator elements to also adjust the respective coupling coefficients, such as the stub-wall extension 1436 that reduces the coupling between resonator elements 1424 and 1430, and to a lesser extent, the coupling between elements 1422 and 1430.

[0097] Fig. 15 depicts an exploded view 1500 of RF front end module 1550, comprising a filter wall enclosure 1504, an enclosure top 1502, a filter enclosure bottom 1506. The isolation enclosure 1508 provides interference mitigation for electrical components such as the distributed power amplifiers, LNAs, circulators, duplexers, or quadriplexers mounted on base 1510, which may also provide a heat sink function. RF front end module 1560 is an alternative embodiment of the assembly comprising a filter wall enclosure 1562, an enclosure top 1564, and a filter enclosure bottom 1566. The isolation posts 1568 attached to mounting plate 1570, provides interference mitigation for electrical components via physical distancing. The isolation enclosure 1574 provides further interference mitigation for electrical components such as the distributed power amplifiers, LNAs, circulators, duplexers, or quadriplexers mounted on base 1572, which may also provide a heat sink function. In some embodiments, the RF front end modules of the distributed RF amplifier chains may be designed to be in conformance with IP-67 specifications by employing waterproof seals (e.g., seal 1576). However, in some embodiments the modules are designed to be enclosed by a radome and are compliant with the less stringent requirements of IP-55.

[0098] Fig. 16 depicts an active antenna apparatus 1600 having two antenna radiating columns 1602, 1604, and respective associated RF distribution networks 1610, 1612. The Fronthaul Gateway board (FHGW) 1630 includes digital baseband transmit processor(s) 1632, that provides digital data to the transmit circuit TX RFIC 1614, which in turn converts the digital data to RF signals for distribution among the TRX devices. The FHGW 1630 also includes digital baseband receive processor(s) 1634, which receive digital baseband data from the RX RFIC 1618, which converts RF signals originating from the TRX devices and received via the RF distribution networks 1610, 1612. The front hall gateway 1630 also includes an observation receiver 1636 and a general purpose I / O (GPIO) circuit 1638 for communicating with the corresponding observation receiver and GPIO interfaces 1620, 1622. Power supply unit (PSU) 1640 provides necessary voltages to the system boards 1606, 1608, 1630.

[0099] Fig. 17 depicts a dual -band distributed amplifier column array with RF receive combiner networks to independently control directional sensitivity of a multi-band RF receive signal. A depiction 1700 includes a dual-band distributed amplifier column array 1702 and RF receive combiner networks 1704a-b. The dual-band distributed amplifier column array 1702 comprises a nominal subarray 1706 and a tapering subarray 1716. The nominal subarray 1706 includes a single antenna element 1708 and the tapering subarray 1716 includes two parallel -wired antenna elements 1718 and 1720. The dual -band distributed amplifier column array 1702 further comprises RF front end module 1710 and RF front end module 1722. Each RF front end module 1710 and 1722 is connected to and positioned substantially adjacent to a corresponding subarray, subarrays 1706 and 1716 respectively. RF front end module 1710 includes a first-band low noise amplifier 1712 and a second-band low noise amplifier 1714. RF front end module 1722 includes a first-band low noise amplifier 1724 and a second-band low noise amplifier 1726.

[0100] In at least one embodiment, each RF front end module includes respective bandpass filters; however, these components are not depicted in Fig. 17.

[0101] Each RF front end module outputs a first-band RF receive signal and a second-band RF receive signal. A set of first-band RF receive signals (e.g., signals output from LNA 1712 and LNA 1724) are received at a corresponding set of first-band phase adjustment circuits 1728 within the first-band RF receive combiner network 1704a. A set of second-band RF receive signals (e.g., signals output from LNA 1714 and LNA 1726) are received at a corresponding set of second-band phase adjustment circuits 1730 within the second-band RF receive combiner network 1704b. The set of first-band phase adjustment circuits 1728 collectively applies a first-band electronic beam tilt to the set of first-band RF receive signals. The set of second-band phase adjustment circuits 1730 collectively applies a second-band electronic beam tilt to the set of second-band RF receive signals. The set of first-band RF receive signals are combined into a combined beam-tilted first-band RF receive signal 1732. The set of second-band RF receive signals are combined into a combined beam-tilted secondhand RF receive signal 1734. RFICs (not depicted) may be used to demodulate the combined signals.

[0102] Fig. 18 depicts an alternative dual -band distributed amplifier column array with RF receive combiner networks to independently control directional sensitivity of a multi-band RF receive signal. Fig. 18 differs from Fig. 17 in that it depicts an alternative RF front end module design. A variety of RF front end module designs may be suitable. A depiction 1800includes a dual -band distributed amplifier column array 1802 and RF receive combiner networks 1804a-b. The dual-band distributed amplifier column array 1802 comprises a nominal subarray 1806 and a tapering subarray 1818. The nominal subarray 1806 includes a single antenna element 1808 and the tapering subarray 1818 includes two parallel -wired antenna elements 1820 and 1822. The dual -band distributed amplifier column array 1802 further comprises RF front end module 1810 and RF front end module 1824. Each RF front end module 1810 and 1824 is connected to and positioned substantially adjacent to a corresponding subarray, subarrays 1806 and 1818 respectively. RF front end module 1810 includes a wide-band low noise amplifier 1812 and bandpass filters 1814-1816. RF front end module 1824 includes a wide-band low noise amplifier 1826 and bandpass filters 1828-1830.

[0103] Each RF front end module outputs a first-band RF receive signal and a second-band RF receive signal. A set of first-band RF receive signals (e.g., signals output from filters 1814 and 1828) are received at a corresponding set of first-band phase adjustment circuits 1832 within the first-band RF receive combiner network 1804a. A set of second-band RF receive signals (e.g., signals output from filters 1816 and LNA 1830) are received at a corresponding set of second-band phase adjustment circuits 1834 within the second-band RF receive combiner network 1804b. The set of first-band phase adjustment circuits 1832 collectively applies a first-band electronic beam tilt to the set of first-band RF receive signals. The set of second-band phase adjustment circuits 1834 collectively applies a second-band electronic beam tilt to the set of second-band RF receive signals. The set of first-band RF receive signals are combined into a combined beam-tilted first-band RF receive signal 1836. The set of second-band RF receive signals are combined into a combined beam-tilted second-band RF receive signal 1838. RFICs (not depicted) may be used to demodulate the combined signals.

[0104] Fig. 19 depicts a dual -band dual-polarization distributed amplifier column array with RF receive combiner networks to independently control directional sensitivity of a multiband RF receive signal. A depiction 1900 includes a dual-band dual-polarization distributed amplifier column array 1902 and RF receive combiner network 1904a-d. The dual -band dualpolarization distributed amplifier column array 1902 comprises a subarray 1908 and a subarray 1924. The subarray 1908 includes two parallel-wired cross-polarized antenna elements 1910-1912 and the subarray 1924 includes two parallel -wired cross-polarized antenna elements 1926-1928. The dual-band dual-polarization distributed amplifier column array 1902 further comprises RF front end module 1906 and RF front end module 1922. EachRF front end module 1906 and 1922 is connected to and positioned substantially adjacent to a corresponding subarray, subarrays 1908 and 1924 respectively. RF front end module 1906 includes a first-band H-polarization low noise amplifier 1914, a second-band H-polarization low noise amplifier 1916, a first-band V-polarization low noise amplifier 1918, and a secondhand V-polarization low noise amplifier 1920. RF front end module 1922 includes a firsthand H-polarization low noise amplifier 1930, a second-hand H-polarization low noise amplifier 1932, a first-hand V-polarization low noise amplifier 1934, and a second-hand V- polarization low noise amplifier 1936.

[0105] In at least one embodiment, each RF front end module includes respective bandpass filters; however, these components are not depicted in Fig. 19.

[0106] Each RF front end module outputs a first-hand H-polarization RF receive signal, a second-hand H-polarization RF receive signal, a first-hand V-polarization RF receive signal, and a second-hand V-polarization RF receive signal. A set of first-band H-polarization RF receive signals (e.g., signals output from LNA 1914 and LNA 1930) are received at a corresponding set of first-band H-polarization phase adjustment circuits 1938 within the firsthand RF receive combiner network 1904a. A set of second-hand H-polarization RF receive signals (e.g., signals output from LNA 1916 and LNA 1932) are received at a corresponding set of second-hand H-polarization phase adjustment circuits 1940 within the second-band RF receive combiner network 1904b. A set of first-hand V-polarization RF receive signals (e.g., signals output from LNA 1918 and LNA 1934) are received at a corresponding set of firsthand V-polarization phase adjustment circuits 1942 within the first-hand RF receive combiner network 1904c. A set of second-band V-polarization RF receive signals (e.g., signals output from LNA 1920 and LNA 1936) are received at a corresponding set of secondhand V-polarization phase adjustment circuits 1944 within the second-hand RF receive combiner network 1904c.

[0107] The set of first-band H-polarization phase adjustment circuits 1938 collectively applies a first-hand electronic beam tilt to the set of first-hand H-polarization RF receive signals. The set of second-hand H-polarization phase adjustment circuits 1940 collectively applies a second-band electronic beam tilt to the set of second-hand H-polarization RF receive signals. The set of first-hand V-polarization phase adjustment circuits 1942 collectively applies a first-band V-polarization electronic beam tilt to the set of first-hand V- polarization RF receive signals. The set of second-hand V-polarization phase adjustmentcircuits 1944 collectively applies a second-band V-polarization electronic beam tilt to the set of second-band V-polarization RF receive signals.

[0108] In at least one embodiment, the electronic beam tilts applied by the set of first-band H-polarization phase adjustment circuits and the set of first-band V-polarization phase adjustment circuits are the same. Likewise, the electronic beam tilts applied by the set of second-band H-polarization phase adjustment circuits and the set of second-band V- polarization phase adjustment circuits are the same. It is worth noting that in most scenarios it is desirable to apply a substantially identical electronic beam tilt to both H and V polarized signals in a given band. However, in at least one embodiment, different tilts are applied to H and V polarized signals.

[0109] Phase adjustment circuits 1938-1944 may each receive a respective set of control signals, each control signal determining an applied phase shift of a corresponding signal. In embodiments where common tilts are applied to H and V polarized signals, the first-band H and V phase adjustment circuits may receive a shared or identical set of first-band control signals, and the second-band H and V phase adjustment circuits may receive a shared or identical set of second-band control signals.

[0110] The set of first-band H-polarization RF receive signals are combined into a combined beam-tilted first-band H-polarization RF receive signal 1946. The set of second-band H- polarization RF receive signals are combined into a combined beam-tilted second-band H- polarization RF receive signal 1948. The set of first-band V-polarization RF receive signals are combined into a combined beam-tilted first-band V-polarization RF receive signal 1950. The set of second-band V-polarization RF receive signals are combined into a combined beam-tilted second-band V-polarization RF receive signal 1952. RFICs (not depicted) may be used to demodulate the combined signals.

[0111] Fig. 20 depicts a method 2000 for band-independent electronic beam tilt of two RF transmit signals comprising steps 2002-2008 (note that the term “step” is not intended to impart or imply a specific required sequence to the methodology described).

[0112] Step 2002 comprises dividing a low-power first-band RF transmit signal into a plurality of divided low-power first-band RF transmit signals using a first-band power splitter and dividing a low-power second-band RF transmit signal into a plurality of divided low- power second-band RF transmit signals using a second-band power splitter.

[0113] Step 2004 comprises collectively applying a first-band electronic beam tilt to the plurality of divided low-power first-band RF transmit signals using a corresponding set offirst-band phase adjustment circuits within a low-power first-hand RF transmit distribution network and collectively applying a second-band electronic beam tilt to the plurality of divided low-power second-band RF transmit signals using a corresponding set of secondhand phase adjustment circuits within a low-power second-band RF transmit distribution network.

[0114] Step 2006 comprises receiving the plurality of divided low-power first-band RF transmit signals and the plurality of divided low-power second-band RF transmit signals at a set of RF front end modules distributed along an antenna array column, wherein each RF front end module is configured to receive and amplify (i) a respective signal from the plurality of divided low-power first-band RF transmit signals to generate an amplified firsthand RF transmit signal, and (ii) a respective signal from the plurality of divided low-power second-hand RF transmit signals to generate an amplified second-hand RF transmit signal.

[0115] Step 2008 comprises transmitting the amplified first-hand RF transmit signals and the amplified second-hand RF transmit signals using a set of subarrays of at least one radiating element distributed along the antenna array column, each subarray being connected to and positioned substantially adjacent to a corresponding RF front end module of the set of RF front end modules.

[0116] In at least one embodiment, each RF front end module comprises (i) a respective firsthand amplifier configured to receive the respective signal from the plurality of divided low- power first-hand RF transmit signals and to generate the amplified first-hand RF transmit signal, and (ii) a respective second-hand amplifier configured to receive the respective signal from the plurality of divided low-power second-hand RF transmit signals and to generate the amplified second-hand RF transmit signal.

[0117] In at least one embodiment, (i) collectively applying the first-hand electronic beam tilt to the plurality of divided low-power first-hand RF transmit signals using the corresponding set of first-hand phase adjustment circuits comprises generating a set of respectively phase- shifted low-power first-hand RF transmit signals using the corresponding set of first-hand phase adjustment circuits, and (ii) collectively applying the second-hand electronic beam tilt to the plurality of divided low-power second-hand RF transmit signals using the corresponding set of second-hand phase adjustment circuits comprises generating a set of respectively phase-shifted low-power second-hand RF transmit signals using the corresponding set of second-band phase adjustment circuits.

[0118] Fig. 21 depicts a method 2100 for band-independent electronic directional sensitivity of a multi-band RF receive signal comprising steps 2102-2112.

[0119] Step 2102 comprises obtaining a set of multi -band RF receive signals at a corresponding set of RF front end modules distributed along an antenna array column, each RF front end module being associated with a subarray of at least one radiating element.

[0120] Step 2104 comprises outputting a first-band RF receive signal and a second-band RF receive signal from each RF front end module to produce a set of first-band RF receive signals and a set of second-band RF receive signals.

[0121] Step 2106 comprises receiving the set of first-band RF receive signals at a corresponding set of first-band phase adjustment circuits within a first-band RF receive combiner network and receiving the set of second-band RF receive signals at a corresponding set of second-band phase adjustment circuits within a second-band RF receive combiner network.

[0122] Step 2108 comprises collectively applying a first-band electronic beam tilt to the set of first-band RF receive signals using the corresponding set of first-band phase adjustment circuits and collectively applying a second-band electronic beam tilt to the set of second-band RF receive signals using the corresponding set of second-band phase adjustment circuits.

[0123] Step 2110 comprises combining the set of first-band RF receive signals using a firsthand signal combiner within the first-band RF receive combiner network to generate a combined beam-tilted first-band RF receive signal and combining the set of second-band RF receive signals using a second-band signal combiner within the second-band RF receive combiner network to generate a combined beam-tilted second-band RF receive signal.

[0124] Step 2112 comprises demodulating the combined beam-tilted first-band RF receive signal and demodulating the combined beam -tilted second-band RF receive signal.

[0125] In at least one embodiment, outputting the first-band RF receive signal and the second-band RF receive signal from each RF front end module comprises each RF front end module using (i) a respective first-band low-noise amplifier to generate the first-band RF receive signal, and (ii) a respective second-band low-noise amplifier to generate the secondhand RF receive signal.

[0126] In at least one embodiment, (i) collectively applying the first-band electronic beam tilt to the set of first-band RF receive signals using the corresponding set of first-band phase adjustment circuits comprises generating a set of respectively phase-shifted first-band RF receive signals using the corresponding set of first-band phase adjustment circuits, and (ii)collectively applying the second-band electronic beam tilt to the set of second-band RF receive signals using the corresponding set of second-band phase adjustment circuits comprises generating a set of respectively phase-shifted second-band RF receive signals using the corresponding set of second-band phase adjustment circuits.

Claims

Claims:

1. An apparatus comprising: a low-power first-band RF transmit distribution network comprising a set of first-band phase adjustment circuits collectively configured to apply a first-band electronic beam tilt to a low-power first-band RF transmit signal; a low-power second-band RF transmit distribution network comprising a set of second-band phase adjustment circuits collectively configured to apply a second-band electronic beam tilt to a low-power second-band RF transmit signal; a set of RF front end modules distributed along an antenna array column, each RF front end module being configured to receive (i) a respective phase-adjusted first-band RF transmit signal from the set of first-band phase adjustment circuits, and (ii) a respective phase-adjusted second-band RF transmit signal from the set of second-band phase adjustment circuits; and, a set of subarrays of at least one radiating element distributed along the antenna array column, each subarray being connected to and positioned substantially adjacent to a corresponding RF front end module of the set of RF front end modules.

2. The apparatus of claim 1, wherein the low-power first-band RF transmit signal comprises a horizontally polarized signal and a vertically polarized signal, and the low-power second-band RF transmit signal comprises a horizontally polarized signal and a vertically polarized signal.

3. The apparatus of claim 2, wherein each of the at least one radiating element(s) of each subarray comprises a respective cross-polarized antenna pair, and each cross-polarized antenna pair is configured to radiate:(i) the horizontally polarized signal of the respective phase-adjusted first-band RF transmit signal, and (ii) the horizontally polarized signal of the respective phase-adjusted second-band RF transmit signal, via a first antenna of the cross-polarized pair; and,(iii) the vertically polarized signal of the respective phase-adjusted first-band RF transmit signal, and (iv) the vertically polarized signal of the respective phase-adjusted second-band RF transmit signal, via a second antenna of the cross-polarized pair.

4. The apparatus of claim 1, wherein the set of subarrays comprises a nominal subarray of N radiating element(s) and a tapering subarray of greater than N radiating elements.

5. The apparatus of claim 1, wherein each RF front end module comprises (i) a firsthand amplifier configured to amplify the respective phase-adjusted first-band RF transmit signal, and (ii) a second-band amplifier configured to amplify the respective phase-adjusted second-band RF transmit signal.

6. The apparatus of claim 5, further comprising (i) at least one ceramic resonator element, configured to filter power outside of the first band, connected to an output of the first-band amplifier, and (ii) at least one ceramic resonator element, configured to filter power outside of the second band, connected to an output of the second-band amplifier.

7. The apparatus of claim 5, wherein each RF front end module comprises a quadriplexer configured to receive and combine (i) an output of the first-band amplifier, and (ii) an output of the second-band amplifier.

8. The apparatus of claim 5, wherein (i) each first-band amplifier is substantially identical and configured to operate at a first output power level, and (ii) each second-band amplifier is substantially identical and configured to operate at a second output power level.

9. The apparatus of claim 5, further comprising: a first set of observation couplers connected to outputs of the first-band amplifiers; a first set of observation phase adjustment circuits, collectively configured to remove the first-band electronic beam tilt, connected to a first-band observation signal combiner; a second set of observation couplers connected to outputs of the second-band amplifiers; and, a second set of observation phase adjustment circuits, collectively configured to remove the second-band electronic beam tilt, connected to a second-band observation signal combiner.

10. The apparatus of claim 9, further comprising:a first-band DPD module configured to modify the low-power first-band RF transmit signal and to update a parameter of the first-band DPD module based at least in part on a combined first-band RF observation signal that is obtained from the first-band observation signal combiner; and, a second-band DPD module configured to modify the low-power second-band RF transmit signal and to update a parameter of the second-band DPD module based at least in part on a combined second-band RF observation signal that is obtained from the second-band observation signal combiner.

11. The apparatus of claim 1, further comprising a first-band buffer amplifier configured to pre-amplify the low-power first-band RF transmit signal and a second-band buffer amplifier configured to pre-amplify the low-power second-band RF transmit signal.

12. The apparatus of claim 1, wherein (i) the low-power first-band RF transmit distribution network comprises a first-band power splitter configured to divide the low-power first-band RF transmit signal into a plurality of divided low-power first-band RF transmit signals and, (ii) the low-power second-band RF transmit distribution network comprises a second-band power splitter configured to divide the low-power second-band RF transmit signal into a plurality of divided low-power second-band RF transmit signals.

13. The apparatus of claim 12, wherein each phase adjustment circuit in the set of firsthand phase adjustment circuits is configured to receive a corresponding divided low-power first-band RF transmit signal from the first-band power splitter and to impart a respective phase-shift to the corresponding divided low-power first-band RF transmit signal, and each phase adjustment circuit in the set of second-band phase adjustment circuits is configured to receive a corresponding divided low-power second-band RF transmit signal from the secondhand power splitter and to impart a respective phase-shift to the corresponding low-power second-band RF transmit signal.

14. The apparatus of claim 1, wherein each phase adjustment circuit in the set of firsthand phase adjustment circuits comprises an N-bit controllable delay and each phaseadjustment circuit in the set of second-band phase adjustment circuits comprises an M-bit controllable delay.

15. A method comprising: dividing a low-power first-band RF transmit signal into a plurality of divided low- power first-band RF transmit signals using a first-band power splitter and dividing a low- power second-band RF transmit signal into a plurality of divided low-power second-band RF transmit signals using a second-band power splitter; collectively applying a first-band electronic beam tilt to the plurality of divided low- power first-band RF transmit signals using a corresponding set of first-band phase adjustment circuits within a low-power first-band RF transmit distribution network and collectively applying a second-band electronic beam tilt to the plurality of divided low-power secondhand RF transmit signals using a corresponding set of second-band phase adjustment circuits within a low-power second-band RF transmit distribution network; receiving the plurality of divided low-power first-band RF transmit signals and the plurality of divided low-power second-band RF transmit signals at a set of RF front end modules distributed along an antenna array column, wherein each RF front end module is configured to receive and amplify (i) a respective signal from the plurality of divided low- power first-band RF transmit signals to generate an amplified first-band RF transmit signal, and (ii) a respective signal from the plurality of divided low-power second-band RF transmit signals to generate an amplified second-band RF transmit signal; and, transmitting the amplified first-band RF transmit signals and the amplified secondhand RF transmit signals using a set of subarrays of at least one radiating element distributed along the antenna array column, each subarray being connected to and positioned substantially adjacent to a corresponding RF front end module of the set of RF front end modules.

16. The method of claim 15, wherein each RF front end module comprises (i) a respective first-band amplifier configured to receive the respective signal from the plurality of divided low-power first-band RF transmit signals and to generate the amplified first-band RF transmit signal, and (ii) a respective second-band amplifier configured to receive the respective signal from the plurality of divided low-power second-band RF transmit signals and to generate the amplified second-band RF transmit signal.

17. The method of claim 15, wherein (i) collectively applying the first-hand electronic beam tilt to the plurality of divided low-power first-hand RF transmit signals using the corresponding set of first-hand phase adjustment circuits comprises generating a set of respectively phase-shifted low-power first-hand RF transmit signals using the corresponding set of first-hand phase adjustment circuits, and (ii) collectively applying the second-hand electronic beam tilt to the plurality of divided low-power second-band RF transmit signals using the corresponding set of second-band phase adjustment circuits comprises generating a set of respectively phase-shifted low-power second-band RF transmit signals using the corresponding set of second-band phase adjustment circuits.

18. A method comprising: obtaining a set of multi -band RF receive signals at a corresponding set of RF front end modules distributed along an antenna array column, each RF front end module being associated with a subarray of at least one radiating element; outputting a first-band RF receive signal and a second-band RF receive signal from each RF front end module to produce a set of first-band RF receive signals and a set of second-band RF receive signals; receiving the set of first-band RF receive signals at a corresponding set of first-band phase adjustment circuits within a first-band RF receive combiner network and receiving the set of second-band RF receive signals at a corresponding set of second-band phase adjustment circuits within a second-band RF receive combiner network; collectively applying a first-band electronic beam tilt to the set of first-band RF receive signals using the corresponding set of first-band phase adjustment circuits and collectively applying a second-band electronic beam tilt to the set of second-band RF receive signals using the corresponding set of second-band phase adjustment circuits; combining the set of first-band RF receive signals using a first-band signal combiner within the first-band RF receive combiner network to generate a combined beam-tilted firsthand RF receive signal and combining the set of second-band RF receive signals using a second-band signal combiner within the second-band RF receive combiner network to generate a combined beam-tilted second-band RF receive signal; and,demodulating the combined beam-tilted first-band RF receive signal and demodulating the combined beam -tilted second-band RF receive signal.

19. The method of claim 18, wherein outputting the first-band RF receive signal and the second-band RF receive signal from each RF front end module comprises each RF front end module using (i) a respective first-band low-noise amplifier to generate the first-band RF receive signal, and (ii) a respective second-band low-noise amplifier to generate the secondhand RF receive signal.

20. The method of claim 18, wherein (i) collectively applying the first-band electronic beam tilt to the set of first-band RF receive signals using the corresponding set of first-band phase adjustment circuits comprises generating a set of respectively phase-shifted first-band RF receive signals using the corresponding set of first-band phase adjustment circuits, and (ii) collectively applying the second-band electronic beam tilt to the set of second-band RF receive signals using the corresponding set of second-band phase adjustment circuits comprises generating a set of respectively phase-shifted second-band RF receive signals using the corresponding set of second-band phase adjustment circuits.

Images