Base station antennas that utilize amplitude-weighted and phase-weighted linear superposition to support high effective isotropic radiated power (EIRP) with high boresight coverage

Abstract

A base station antenna (BSA) system includes a radio-frequency (RF) generator having a plurality of power-amplifying circuits therein, and an antenna, which includes a plurality of columns of radiating elements. These radiating elements are electrically coupled by RF signal routing to a corresponding plurality of ports of the antenna that receive a corresponding plurality of RF input signals. These RF input signals have respective amplitudes and phases that support the concurrent generation of three spaced-apart RF beams by the antenna and are derived from respective RF signals generated by the plurality of power-amplifying circuits. The RF input signals including: (i) a first RF input signal defined by at least two linearly superposed RF signals of equivalent frequency having unequal combinations of amplitude and phase weighting, and (ii) a second RF input signal defined by at least two linearly superposed RF signals of equivalent frequency having unequal combinations of amplitude and phase weighting.

Claims

1. A base station antenna, comprising: a plurality of columns of radiating elements electrically coupled by RF signal routing to a corresponding plurality of ports of the antenna that are configured to receive a corresponding plurality of RF input signals having respective amplitudes and phases that support the concurrent generation of first, second and third spaced-apart beams by the antenna, the plurality of ports including: a first port configured to receive a first of the plurality of RF input signals, which comprises first and second signals of equivalent frequency having unequal amplitude and/or phase weighting that contribute to the first and second beams, respectively; a second port configured to receive a second of the plurality of RF input signals, which comprises third and fourth signals of equivalent frequency having unequal amplitude and/or phase weighting that contribute to the first and third beams, respectively; and a third port configured to receive a third of the plurality of RF input signals, which comprises a fifth signal that contributes to the first beam; wherein the first and third signals are amplitude-tapered relative to the fifth signal; wherein a total power of the first of the plurality of RF input signals is within 4% of a total power of the third of the plurality of RF input signals; and wherein a total power of the second of the plurality of RF input signals is within 4% of the total power of the third of the plurality of RF input signals.

2. The antenna of claim 1, wherein the first, second and third ports correspond to respective first, second and third columns of radiating elements within the antenna; and where the third column extends between the first and second columns.

3. The antenna of claim 2, wherein the third of the plurality of RF input signals consists of the fifth signal.

4. The antenna of claim 1, further comprising a fourth port configured to receive a fourth of the plurality of RF input signals, which comprises a sixth signal that contributes to the first beam.

5. The antenna of claim 4, wherein the fourth of the plurality of RF input signals consists of the sixth signal.

6. The antenna of claim 5, wherein the antenna includes eight (8) columns of radiating elements arranged side-by-side as columns one through eight; and wherein the first, second, third and fourth ports correspond to the third, sixth, fourth and fifth columns of radiating elements, respectively.

7. The antenna of claim 6, wherein the first and third signals are amplitude-tapered relative to the sixth signal.

8. The antenna of claim 1, wherein the first and second signals are linearly superposed and 180° out-of-phase relative to each other; and wherein the third and fourth signals are linearly superposed and 180° out-of-phase relative to each other.

9. A base station antenna, comprising: first through nth side-by-side columns of radiating elements electrically coupled by RF signal routing to respective first through nth ports of the antenna, which are configured to receive respective first through nth RF input signals having respective amplitudes and phases that support the concurrent generation of first, second and third spaced-apart beams by the antenna, the first through nth ports including: a mth port configured to receive an mth RF input signal that contributes to the first, second and third beams, said mth RF input signal comprising first, second and third signals of equivalent frequency having respective first, second and third unequal amplitudes; and a (m+1)th port configured to receive an (m+1)th RF input signal that contributes to the first, second and third beams, said (m+1)th RF input signal comprising fourth, fifth and sixth signals of equivalent frequency having respective fourth, fifth and sixth unequal amplitudes; wherein the third and sixth signals contribute to the first beam and have unequal amplitudes; wherein the second and fifth signals contribute to the second beam and have unequal amplitudes; wherein the first and fourth signals contribute to the third beam and have equal amplitudes; and wherein the third beam extends between the first and second beams within the azimuth plane of the antenna.

10. The antenna of claim 9, wherein n is a positive integer equal to eight (8), and m is a positive integer equal to four (4).

11. The antenna of claim 9, wherein the third and fifth signals have equivalent amplitudes; and wherein the second and sixth signals have equivalent amplitudes.

12. The antenna of claim 9, wherein the first through nth ports includes an (m−1)th port, which is configured to receive an (m−1)th RF input signal that contributes to the first and third beams, but not the second beam.

13. The antenna of claim 9, wherein the first through nth ports includes an (m−1)th port, which is configured to receive an (m−1)th RF input signal that contributes to the first and third beams; and wherein a total power of the (m−1)th RF input signal is within 4% of a total power of the mth RF input signal.

14. A base station antenna, comprising: first through nth side-by-side columns of radiating elements electrically coupled by RF signal routing to respective first through nth ports of the antenna, which are configured to receive respective first through nth RF input signals having respective amplitudes and phases that support the concurrent generation of first, second and third spaced-apart beams by the antenna, the first through nth ports including: a second port configured to receive a second RF input signal that contributes to the first beam; a third port configured to receive a third RF input signal that contributes to the first and third beams; a fourth port configured to receive a fourth RF input signal that contributes to the third beam; a fifth port configured to receive a fifth RF input signal that contributes to the third beam; a sixth port configured to receive a sixth RF input signal that contributes to the second and third beams; and a seventh port configured to receive a seventh RF input signal that contributes to the second beam.

15. The antenna of claim 14, wherein the second RF input signal contributes to the first beam, but not the second or third beams; wherein the third RF input signal contributes to the first and third beams, but not the second beam; wherein the sixth RF input signal contributes to the second and third beams, but not the first beam; and wherein the seventh RF input signal contributes to the second beam, but not the first or third beams.

16. The antenna of claim 15, wherein a total power of the third RF input signal is within 2% of the total power of the second RF input signal; and wherein a total power of the sixth RF input signal is within 2% of the total power of the seventh RF input signal.

17. The antenna of claim 14, wherein the first port is configured to receive a first RF input signal that is 90° out-of-phase relative to the second RF input signal; and wherein the nth port is configured to receive an nth RF input signal that is 90° out-of-phase relative to the seventh RF input signal.

18. The antenna of claim 17 wherein a portion of the third RF input signal that contributes to the first beam is 180° out-of-phase relative to the first RF input signal; and wherein a portion of the sixth RF input signal that contributes to the second beam is 180° out-of-phase relative to the nth RF input signal, where n equals eight (8).

19. The antenna of claim 18, wherein a portion of the third RF input signal that contributes to the third beam is in phase with the fourth RF input signal; and wherein a portion of the sixth RF input signal that contributes to the third beam is in phase with the fifth RF input signal.

20. The antenna of claim 17, wherein a portion of the third RF input signal that contributes to the third beam is in phase with the fourth RF input signal; and wherein a portion of the sixth RF input signal that contributes to the third beam is in phase with the fifth RF input signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a block diagram of a phased array antenna according to the prior art.

(2) FIG. 1B is a normalized plot of a single radiated antenna beam having an azimuth Half Power Beam Width (HPBW) of approximately 65°, which may be utilized with two other equivalent beams to cover three 120° sectors, as shown.

(3) FIG. 2 is a normalized plot of two 38° radiated antenna beams, which demonstrate an absence of sufficient coverage, particularly at boresight (e.g., 00) for a tessellated pattern arrangement covering three (3) 120° sectors, as shown.

(4) FIG. 3A is a functional block diagram of a base station antenna system that utilizes multiple columns of diplexed dual-polarized radiating elements, a wide band RF transceiver (TX/RX), and power amplifier circuits that support amplitude-weighted and phase-weighted linear superposition, according to an embodiment of the present invention.

(5) FIGS. 3B, 3C and 3D are simulated two-dimensional graphs of first through third antenna beams, respectively, that are generated by an 8-column base station antenna, along with graphs showing the amplitude-weights and phase-weights that are applied to the RF signals transmitted through each column of the base station antenna in order to generate the first through third antenna beams.

(6) FIG. 3E is a normalized plot of three antenna beams that collectively demonstrate higher crossovers (at +/−20°) for better coverage over a respective 120° sector, for an eight-column base station antenna that utilizes amplitude-weighted and phase-weighted linear superposition according to an embodiment of the present invention.

(7) FIG. 3F is a block diagram that illustrates a “long” array of paired radiating elements that may be fed with signals from multiple radios (i.e., two frequency bands) to thereby achieve significant improvements in gain (in the elevation plane) with relatively minimal offsets caused by diplexer insertion loss, according to an embodiment of the present invention.

(8) FIG. 3G is a block diagram of an eight (8) column dual-band base station antenna, according to an embodiment of the present invention.

(9) FIG. 4 is a block diagram of a multi-band RF transmitter for a base station antenna with power-amplifying linear superposition (PALS) circuits therein to support multi-beam generation according to embodiments of the present invention.

DETAILED DESCRIPTION

(10) Pursuant to embodiments of the present invention, base station antennas are provided that include a plurality of columns of radiating elements that may be configured to generate three spaced-apart beams in the azimuth plane. The three antenna beams may, for example, provide coverage for a 120° sector (in the azimuth plane) of a cellular base station. The antenna beams may be generated by feeding at least two linearly superposed RF signals of equivalent frequency that have different amplitude and/or phase weights applied thereto to at least some of the columns of radiating elements.

(11) In some embodiments, the base station antennas may have eight columns of radiating elements. The amplitude and phase weights may be selected so that a weighting loss may be kept low, and hence the antenna may maintain high effective isotropic radiated power (EIRP) levels. For example, in some embodiments, the weighting loss may be less than 20%. In other embodiments, the weighting loss may be less than 10%. In fact, in some embodiments, the weighting loss may be effectively zero or at least close to zero. Herein, the “weighting loss” refers to the reduction in EIRP that results from the amplitude taper applied to different columns of radiating element in forming the multiple antenna beams.

(12) In some embodiments, the radiating elements may be wideband radiating elements that support operation in at least two different frequency bands. Diplexers may be provided for each column of radiating elements that connect the radiating elements of the column to a pair of radio ports that transmit in the different frequency bands. By using diplexers and wide band radiating elements, longer columns may be used that narrow the elevation beamwidth, thereby improving the gain of the antenna and hence the supportable EIRP level.

(13) Referring now to FIG. 3A, a base station antenna (BSA) system 100 according to an embodiment of the invention is illustrated that includes a multi-band radio 40, a diplexer and phase shifter assembly (PSA) array 50, and an antenna 70 containing a multi-column array of radiating elements 72 (e.g., 8-column array), such as dual-polarized (e.g., +45°, −45°), wide band radiating elements. As illustrated, the multi-band radio 40 may be a dual-polarized wide band RF transceiver (Tx/Rx) with digital control 42, and a control processor 44, which controls operations of the transceiver 42. As illustrated, on the transmission (Tx) side, the transceiver 42 is coupled to and drives power amplifiers 46 with RF signals to be transmitted (e.g., dual-band RF signals). And, on the receiver (Rx) side, the transceiver 42 receives RF signals output by low noise amplifiers LNA 48. As described more fully hereinbelow, the power amplifiers 46 may be embodied as digitally-controlled power-amplifying linear superposition circuits with programmable amplitude and/or phase weighting, which supports enhanced three-beam generation and low effective isotropic radiated power (EIRP) loss when the power amplifiers are advantageously run at full or nearly full power.

(14) As further illustrated by FIG. 3A, the radio frequency output signals generated by the power-amplifying linear superposition circuits may be provided to an array of diplexers (to support multi-band operation) and an array of phase shifter assemblies 50, which drive the antenna 70. In some embodiments of the invention, the diplexers may be configured as comb-line filters having high Q-factor (e.g., approx. 1800) and relatively small dimensions (e.g., 81×41×20 mm). Advantageously, diplexers of small size may be more readily integrated between relatively narrowly-spaced columns of antenna radiating elements. The phase shifter assembly 50 that is provided for each column of radiating elements included in the antenna array 70 may split RF signals that are to be transmitted by the column into a plurality of sub-components, and each sub-component may be fed to a respective one of the radiating element (or to a commonly-fed sub-array of radiating elements) and may likewise combine the RF signals received at each radiating element (or sub-array) and pass the combined signal to the dual-band radio 40. Each phase shifter assembly 50 may also be configured to apply a phase taper to the sub-components of the RF signal that are passed to the respective radiating elements (or sub-arrays) in order to, for example, effect an electronic downtilt to the antenna beam. It will be appreciated that the phase shifter assemblies 50 may be simply comprise power splitter/combiners in some embodiments that do not perform any relative phase shifting of the sub-components of the RF signal.

(15) Referring now to FIGS. 3B-3E and Tables 1-2, the power amplifiers 46 illustrated in FIG. 3A may be advantageously operated as power-amplifying linear superposition (PALS) circuits (with programmable amplitude and/or phase weighting), to thereby provide enhanced three-beam generation (with low EIRP loss) within the antenna 70, as illustrated by FIG. 3E. In particular, the simulated two-dimensional graphs of FIGS. 3B-3D and entries of Table 1 illustrate amplitude and/or phase weighted operations of the PALS circuits according to an embodiment of the present invention. In this embodiment, the PALS circuits can provide controlled three-way splitting of power amplifier output signals, along with independent phase shifting of the three-way split signals, if necessary, and then combining of the three-way split signals (in accordance with linear superposition principles). After combining, a plurality of the “combined” signals are provided to the radiating elements 72 within the antenna 70, via the diplexer and phase shifter assembly (PSA) array 50, to thereby yield three separate beams associated with a corresponding band.

(16) Thus, as shown by FIG. 3B and Table 1, a first beam (BEAM 1, −40°) having the illustrated characteristics may be generated by the antenna 70, based on the illustrated per column amplitude and phase weights, which are implemented by the PALS circuits associated with the programmable power amplifiers 46. Similarly, as shown by FIG. 3C and Table 1, a second beam (BEAM 2, +40°), which is a mirror-image of the first beam (about 0°), may be generated based on the illustrated per column amplitude and phase weights. Next, as shown by FIG. 3D and Table 1, a third beam (BEAM 3, 0°), which is symmetric about 0° and preferentially has a peak amplitude at boresight, may be generated based on the illustrated per column amplitude and phase weights. The entries of Table 1 further illustrate that amplitude tapering (>0.25) associated with the “left” BEAM 1 can be performed using the radiating elements associated with Columns 1 and 4-5 of the antenna and amplitude tapering associated with the “right” BEAM 2 can be performed using the radiating elements associated with Columns 4-5 and 8. In addition, amplitude tapering associated with “center” BEAM 3 can be performed using the radiating elements associated with Columns 3 and 6, where a taper of 0.75 is illustrated for BEAM 3.

(17) TABLE-US-00001 TABLE 1 AMPLITUDE WEIGHTING - EXAMPLE 1 COLUMN 1 2 3 4 5 6 7 8 BEAM 1 0.77 1.0  1.0 0.74 0.28 0.0 0.16 0.08 (−40°) BEAM 2 0.08 0.16 0.0 0.28 0.74 1.0 1.0  0.77 (+40°) BEAM 3 0.0  0.10 0.75 1.0 1.0 0.75 0.10 0.0  (0°) TAPER YES NO* YES YES YES YES NO* YES (1) (3) (1/2) (1/2) (3) (2) Total 0.37 0.64 0.96 1.0 1.0 0.96 0.64 0.37 (PWR)

(18) Next, applying the same simulation approach illustrated by FIGS. 3B-3C, but substituting the amplitude and phase weights of Table 2 to the PALS circuits, yields the “composite” beam pattern of FIG. 3E with: (i) high coverage at boresight (BEAM 3), (ii) improved coverage by the side beams (BEAMS 1, 2) at +/−20°, and (iii) lower crossovers (with neighboring 120° sectors) at +/−60°, which closely matches the 65° pattern of FIG. 1B and resolves the loss of boresight coverage associated with the two-beam pattern of FIG. 2.

(19) Moreover, as shown by the amplitude/power distribution within Table 2, the beams of FIG. 3E allow for 100% rms power usage of the corresponding eight (8) antenna ports (but with two ports having two signal amplitudes adding), which minimizes the EIRP losses typically caused by running power amplifiers at less than full power. Preferably, the PALS circuits are operated with less than 20% weighting loss during the concurrent generation of the three spaced-apart RF beams at the first frequency.

(20) The entries of Table 2 further illustrate that one-sided amplitude tapering associated with the “left” BEAM 1 can be performed by using the radiating elements associated with Column 3 of the antenna and one-sided amplitude tapering associated with the “right” BEAM 2 can be performed by using the radiating elements associated with Column 6. In contrast, dual-sided amplitude tapering associated with “center” BEAM 3 can be performed using the radiating elements associated with Columns 3 and 6, where a taper of 0.7 is illustrated.

(21) TABLE-US-00002 TABLE 2 AMPLITUDE AND PHASE WEIGHTING - EXAMPLE 2 COLUMN 1 2 3 4 5 6 7 8 BEAM 1 1.0 1.0 0.7 0.0 0.0 0.0 0.0 0.0 PHASE 1 0 90° 180° 0 0 0 0 0 BEAM 2 0.0 0.0 0.0 0.0 0.0 0.7 1.0 1.0 PHASE 2 0 0 0 0 0 180° 90° 0 BEAM 3 0.0 0.0 0.7 1.0 1.0 0.7 0.0 0.0 PHASE 3 0 0 0 0 0 0 0 0 TAPER NO NO YES NO NO YES NO NO (1/3) (2/3)

(22) Next, as shown by the diplexer and phase shifter assembly 50′ of FIG. 3F, multiple relatively short single band antennas (not shown) may be replaced by a 2× length broad band antenna having paired radiating elements 72′, in order to achieve a significant increase in antenna directivity and gain, along with increased EIRP. Thus, by using a two-input diplexer to implement frequency-domain multiplexing of two bands (RF1, RF2), two single band antenna arrays having seven (7) radiating elements per column may be replaced by a single multi band antenna having fourteen (14) paired radiating elements per column, as shown. While in the depicted embodiment, the radiating elements 72′ are arranged in pairs, it will be appreciated that other arrangements are possible. For example, a phase shifter assembly (PSA) having fourteen outputs (as opposed to the seven outputs shown in FIG. 3F) could be used, in which case all fourteen radiating elements could receive distinct sub-components of the RF signal. In other cases, the radiating elements could be grouped into any combination of sub-arrays having one, two, three or even more radiating elements. It will also be appreciated that the phase shifter assembly could be replaced with a power splitter/combiner in still other embodiments.

(23) FIG. 3G is a block diagram of an 8-column dual-band base station antenna (BSA) 110, according to an embodiment of the present invention. As illustrated, the antenna 110 includes eight columns of fourteen (14) dual-band, cross-polarized, radiating elements (RE), which are respectively coupled to multi-band RF signal routing 112_1 to 112_8. The multi-band RF signal routing 112_1 to 112_8 may comprise, for example, corporate feed networks or phase shifter assemblies that divide the RF signals fed to each column into a plurality of sub-components that are passed to the radiating elements RE, and which may also optionally adjust the relative amplitudes and/or phases of the sub-components. As shown, each “band” of the RF signal routing is electrically coupled to corresponding ones of the bidirectional ports (e.g., 32 ports), via the 2-to-1 diplexers 114 (2 diplexers/column), which may be configured as comb-line filters.

(24) Referring now to FIG. 4, a block diagram of a multi-band RF transmission system 200 is illustrated as containing a first radio transmitter 202a (BAND1) with a first array of PALS circuits 46a, and a second radio transmitter 202b (BAND2) with a second array of PALS circuits 46b. This RF transmission system 200 is also illustrated as including an array of diplexers for supporting dual-band signal transmission to an eight (8) column broad band antenna array (see, e.g., FIG. 3F), and an array of phase shifter assemblies 50″ coupled thereto, as shown. It will be appreciated that FIG. 4 is a functional block diagram that illustrates the types of operations that may be performed by the multi-band RF transmission system 200, and is not intended to be limiting in any fashion regarding the implementation of the circuitry that performs such operations.

(25) The PALS circuits 1-8 associated with the first and second radio transmitters 202a, 202b are illustrated as having equivalent design, with each PALS circuit containing: (i) a power amplifier PA (e.g., 5 Watt), (ii) a low-loss programmable power divider PPD with three outputs, (iii) three programmable phase shifters PPS1, PPS2, PPS3 connected to respective PPD outputs, and (iv) a power combiner PC for support linear superposition of three output signals from PPS1-PPS3. The phase shifters PPS1-PPS3 may be programmed to achieve desired phase weighting. The amplitude weightings provided by the PPDs may be programmed so that the power amplifiers PA are continuously operated at full or nearly full power to thereby minimize EIRP losses caused by amplitude taper (i.e., “weighting loss”), while simultaneously achieving a desired 3-beam pattern within an antenna, as shown by FIG. 3E, for example.

(26) The present invention has been described above with reference to the accompanying drawings, in which preferred embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth above; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

(27) It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

(28) The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprising”, “including”, “having” and variants thereof, when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. In contrast, the term “consisting of” when used in this specification, specifies the stated features, steps, operations, elements, and/or components, and precludes additional features, steps, operations, elements and/or components.

(29) Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

(30) In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.