WO2025155790A1 - Rapid sequential area scanning with reduced beam interference - Google Patents

Abstract

Systems, methods, and devices are described for adapting multiple-element-array beamforming systems to work with passive multiple beam antennas, such as a RF lens. Different beams can be sequentially powered by different elements distributed about an RF lens. Use of the lens natively directs the beams from each element in a different direction to effect scanning across a sector or subsector region. Such adaptations are implemented by hardware, by software, or combinations thereof. Hardware-based adaptations include introducing a reverse-beam-forming network in combination with traditional beam forming radios. Software-based adaptations include configuring a processor to interface with standard radio heads and an RF lens antenna to deliver beam-forming functionality. Codebook feedback is made compatible with lens beamforming without changing the user equipment, by modifying the CSI reference signals sent by the gNodeB to compensate for the unnecessary discrete Fourier transform operation.

Description

Rapid Sequential Area Scanning With Reduced Beam Interference

Priority

[0001] This application claims priority to US non-provisional application no. 18/926762 filed on October 25, 2024, which claims priority to US provisional application no. 63/623135 filed on January 19, 2024, and additionally claims priority to US provisional application no. 63/729545 filed on December 9, 2024. These and all other referenced extrinsic materials are incorporated herein by reference in their entirety.

Field of the Invention

[0002] The field of the invention is radio frequency (RF) Antenna Systems

Background

[0003] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0004] Cell phone base stations, as well as other applications, need to resolve two basic problems, capacity and throughput. In more recent years capacity (number of people being served) and throughput(the speed at which data can be transferred and the quality of the signal) have become the main priority. Capacity can typically be improved by adding additional beams/radios into a given sector, whereas thruput can be improved by having clean signal (good SINR , signal to noise ratio, or less interference from other beams) and good gain.

[0005] Traditionally a 2x2 radio (two polarizations providing one beam) was used together with an antenna to provide a single beam covering 120 degree sector. In many cases, however, this is no longer sufficient to provide sufficient capacity or throughput. In a typical prior art configuration, a 4x4 radio supports two spatial streams/ beams (each with two polarizations, i.e., each beam being 2X2 ). The two streams can operate on the same sector (same geographical area) to provide MIMO, and to increase capacity, the two streams can alternatively operate simultaneously on two different regions of a sector, i.e., operate on same region in 4X4 configuration or have two 2X2 operating in two separate regions. Operating on two different regions increases the capacity, but can reduce throughput due to interference in any overlapping regions, poor SINR in overlapping regions. Furthermore, at the area of intersection/crossover of the beams, the gain drops and thus again reduces throughput. For simplicity, adjacent spatial streams can be visualized as two beams 110, 120, with interference region 115 in prior art Figure 1. It should be appreciated that although beams 110, 120 are shown with solid boundaries, actual beams have indistinct boundaries of diminishing intensity, as well as side lobes (not shown).

[0006] To increase capacity further, it is possible to use 8x8 radios, which support 4 beams, respectively. Such radios supports four spatial streams/or beams, which can be used to increase capacity by creating 4 separate beams in a given 120 degree sector, each beam now being more narrow (smaller horizontal beamwidth) , as opposed to 2 beams in a 120 degree sector ,and thus having higher gain. The beams can be created by different types of antennas (whether phased array multi-beam antenna or RF Lens multi-beam antenna, or even 4 separate single beam antennas). See prior art Figure 2 showing a 120° sector covered by four beams 210, 220, 230, 240. As with the two-beam solution of Figure 1, there are multiple regions of interference 215, 225, 235, which reduce gain. Therefore, one solution to increase capacity and throughput was to use a multi-beam antenna and have multiple beams covering 120 degree sector. Having multiple beams in a given 120 degree sector can improve capacity, however, due to interference regions and areas of lower gain (where beams cross as compared to peak of the beam), it is difficult to increase throughput.

[0007] Another solution to this was using a beam-forming antenna. Beam forming can be used to increase gain and eliminate destructive interference. In beam forming, a phased array antenna with multiple elements is used to create single beam that can scan the entire 120° sector 305 (e.g., beam 310 scanning left to right in prior art Figure 3), or region within a sector.

[0008] In prior art Figure 4, a single array of elements 412, 414, 416, and 418 can be used to form a single beam (in this case beam 410), which are then used to scan sector 405 by phase shifting. Typically, multiple columns of elements are used to form a beam (i.e., 4 columns of elements, or 32 by 32 elements, 64 by 64 elements). Beam 410 has higher gain as it is a narrow beam created by phasing multiple elements. Therefore beam-forming antennas provide a solution where a 4X4 radio can be connected to a multiple column phased array antenna to create a single beam which can be scanned based on phase signal provided from the radio. This provides a solution for thru put as a single beam in the sector has no (or little) interference from neighboring beams (no cross over area) and has high gain. However, although capacity is increased, there is a limit to increasing capacity as only a single beam is being used in the 120 degree sector. Furthermore, as the beam is scanned (by adjusting phased between elements) away from boresight, the shape of the beam changes as well as the sidelobes are increased lobes (not shown) providing potentially more interference to neighboring sectors. If multiple beams are formed from the same multiple elements phased array antenna, there is poor isolation between the beams thus reducing throughput.

[0009] To increase capacity, multiple beam-formed beams can be operated by different element arrays (i.e., two separate antennas), albeit with increases in complexity, power, and cost and physical size. In prior art Figure 5, beam 510 is formed by combining emissions of elements 512, 514, 516, and beam 520 formed by combining emissions of elements 522, 524, 526, and beams 510, 520 cooperate to scan sector 505. Although in the case of using two separate antennas to create two separate beam-forming beams (Fig. 5), this is not practical as one would need two antennas (cost, physical space, power consumption). Furthermore, to create two narrow beams larger antennas would need to be used.

Therefore, by introducing a beam-forming antenna combined with a 4X4 radio or 8X8 Radio thru put can be improved but there is a limitation to how much capacity can be increased, furthermore beamforming antennas may not be suitable for FDD (frequency division duplex) mode of transmitting/receiving signals due to their relatively narrow band, not stable beamwidth/beam position over larger frequency range. Therefore, a solution is proposed where standard 4X4 or 8X8 or other types of radios can be used together with an RF Lens antenna, to provide a solution for capacity, thru put and allow the antenna to be used in both TDD and FDD modes over wide frequency range, as well as provide potential power saving as compared to a beam forming solution. Summary of the Inventive Subject Matter

[0010] What was not appreciated in the prior art is that all of these problems can be resolved by sequentially powering different elements distributed about an RF lens. Use of the lens natively directs the beams from each element in a different direction to effect scanning across a sector or subsector region.

Brief Description of The Drawings

[0011] Fig. 1 is a diagram of adjacent spatial streams visualized as two beams having interference region.

[0012] Fig. 2 is a diagram of a 120° sector covered by four having three interference regions.

[0013] Fig. 3 is a diagram of a 120° sector beam- scanned by a phased array antenna.

[0014] Fig. 4 is a diagram of a 120° sector beam- scanned by phase shifting of a four-element antenna array.

[0015] Fig. 5 is a diagram of a sector beam-scanned by phase shifting of two, four-element antenna arrays.

[0016] Fig. 6 is a diagram of a sector beam-scanned using twelve beams sequentially powered by twelve elements, respectively, disposed about a lens.

[0017] Fig. 7 is a diagram of a sector beam-scanned using eight beams sequentially powered by eight horn antennas, respectively.

[0018] Fig. 8 is a simplified version of Figure 6, where the four beams in each of three regions is powered by a different 8x8 radio.

[0019] Fig. 9 is a diagram of sector scanning using Frequency Division Duplex beam forming. Detailed Description

[0020] In Figure 6, elements 61 IE, 612E, 613E, 614E are positioned about lens 650are sequentially powered to provide beams 61 IB, 612B, 613B, and 614B respectively, which effectively scans region 602. Similarly, elements 621E, 622E, 623E, and 624E are sequentially powered to provide beams 621B, 622B, 623B, and 624B respectively, which effectively scans region 604. And elements 63 IE, 632E, 633E, and 634E are sequentially powered to provide beams 63 IB, 632B, 633B, and 634B respectively, which effectively scans region 606. To substantially reduce or even eliminate interference, powering the various beams can be coordinated, so that for example, beams 61 IB, 621B, 631B, can all be powered on and off concurrently, beams 612B, 622B, 632B, can all be powered on and off concurrently, and beams 613B, 623B, 633B can all be powered on and off concurrently. In Figure 6, regions 602, 604 and 606 could collectively cover a 120° sector, or a larger or smaller region.

[0021] If the beams arc sufficiently narrow as a result of using a lens having appropriate size and index of refraction, one could operate multiple beams within a single region, without substantial interference. For example, one could concurrently operate beams 61 IB, 613B, 621B, 623B, 631B, and 633B, followed by concurrently operating beams 612B, 614B, 622B, 624B, 632B, and 634B, and then back to 61 IB, 613B, 621B, 623B, 631B, and 633B. Such a solution provides narrow high gain beams with no or little interference with neighboring beams (thus providing good SINR and throughput), while also providing multiple high isolation beams in a 120 degree sector (thus providing good capacity). RF lens as compared to phased array antenna has much higher isolation between beams, further can provide similar shaped (beamwidth, sidelobes) beams across a 120 degree sector (i.e., no or little beam degradation over 120 degree sector unlike a phased array antenna).

[0022] Use of directed sequentially powered narrow beams to scan a region need not rely on a lens for directionality. In Figure 7, beams 701B, 702B, 703B, 704B, 705B, 706B, 707B, and 708B are powered and narrowed directed by horn antennas 701B, 702B, 703B, 704B, 705B, 706B, 707B, and 708B, respectively. One could sequentially operate the beams in any desired sequence. For example, one could operate beams 701B, 702B, 703B, and 704B, 705B, 706B, 707B, and 708, sequentially, or alternatively operate 701B concurrently with 705B, 702B with 706B. 703B with 707B, and 704B with 708B. Still further one could operate 701 B, 703B, 705B and 707B, followed by concurrent operation f 702B, 704B, 706B and 708B.

[0023] Beam scanning for a cell tower, using concepts discussed herein would likely require very rapid switching on/off of the beams/elements. Such switching could advantageously be executed in nanosecond timeframes.

[0024] Figure 8 is a simplified version of Figure 6. Here the four beams in each of the three regions 602, 604, 608 can be powered by a different 8x8 radio. Beams 602A, 602B, 602C, and 602D are powered by 8x8 Radio 602R, beams 604A, 604B, 604C, and 604D are powered by 8x8 Radio 604R, and beams 602A, 602B, 602C, and 602D are powered by 8x8 Radio 602R. As with other drawing figures herein, lens 850 and the various beams in Figure 8 are not drawn to scale.

[0025] The configuration described above with respect to Figures 8 has numerous advantages over prior art beam forming. Capacity is greatly increased by using 3 8x8 radios instead of one or two 4x4 radios. Gain is also increased because the individual beams are narrow and there are no (or at least very minimal) regions of interference thus providing higher throughput(better SINR). Still further, power is reduced using sequential beam scanning. Instead of all elements being concurrently powered at all times with beam forming, sequential beam scanning powers elements sequentially. In order to create a single beam to scan the coverage area, beam-forming antenna has to have power to all elements in the phased array antenna, where as in described solution, only the single elements providing required beam need to be powered on.

[0026] Still further, Frequency Division Duplex is problematic for beam formed configurations, but not for the above-described lens-based, or other sequential beam scanning configurations. Prior art Figure 9 shows that scanning using FDD at 1.7 GHz and 2.7 GHz with elements 902, 904, 906, 908 is problematic with beam forming because the different frequencies have slightly different coverage areas and different beam shape s/direction (beam 910 for 2.7 GHz, beam 920 for 1.7 GHz). Furthermore when operating on FDD a beam forming phased array antenna can also create PIM (passive inter modulation) which is not desirable. [0027] Unlike a phased array antenna, RF Lens antenna provides much better beamwidth stability over larger frequency range (wider band) and thus can be suitable to be used in both TDD and FDD modes.

[0028] The proposed solution provides a solution for having multiple radios/multiple beams covering required sector with high capacity and thru put, number of radios/beams can vary depending on requirement.

[0029] In contrast, using FDD with sequential beam scanning would result in clean, properly directed beams. In Figure 6, for example, beams 601B could operate at 1.7 GHz concurrently with beams 602B operating at 2.7 GHz, with little to no interference. Single elements / beams could also concurrently use multiple frequencies. Thus, for example elements 601E, 603E, 605E, 607E could concurrently use both 1.7 GHz and 2.7 GHz, and then elements 602E, 604E, 606E and 608E could concurrently use both 1.7 GHz and 2.7 GHz

[0030] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C .... and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

Claims

CLAIMS What is claimed is:

1. An antenna system comprising: first, second, third, and fourth beams directed to first, second, third, and fourth coverage areas, respectively; wherein the second coverage area overlaps the first and third coverage areas, and the third coverage area overlaps the second and fourth coverage areas; a controller configured to sequentially operate first and second elements to power the first and second beams at a first frequency, and sequentially operate third and fourth elements to power the third and fourth beams at the first frequency.

2. The system of claim 1, wherein the controller is further configured to concurrently operate first and third elements to power the first and third beams, respectively.

3. The system of claim 1, wherein the controller is further configured to sequentially operate the second and third elements to power the second and third beams, respectively.

4. The system of claim 1, further comprising an 8x8 radio configured to provide signals to each of the first, second, third, and fourth beams.

5. The system of claim 1, wherein the first, second, third and fourth elements are positioned about an RF lens that directs the first, second, third, and fourth beams to the first, second, third, and fourth coverage areas, respectively.

6. The system of claim 1, wherein the controller is configured to operate the second beam at a second frequency different from the first frequency, concurrently with the first beam operating at the first frequency.

7. The system of claim 1, wherein the controller is configured to operate the first beam at a second frequency different from the first frequency, concurrently with the first beam operating at the first frequency.

8. An antenna system comprising: first, second, and third beams directed to first, second, and third coverage areas, respectively; wherein the second coverage area overlaps the first and third coverage areas; and a controller configured to sequentially operate first, second and third elements to power the first, second, and third beams at a first frequency.

9. The system of claim 8, wherein the first, second, and third elements are positioned about an RF lens that directs the first, second, and third beams to the first, second, and third coverage areas, respectively.

10. The system of claim 8, wherein the controller is configured to operate the first beam at a second frequency different from the first frequency, concurrently with the first beam operating at the first frequency.

11. The system of claim 8, wherein the controller is configured to operate the first beam at both the first frequency and a second frequency different from the first frequency, concurrently with the first beam operating at the first frequency.

12. A method of scanning a region comprising: sequentially operating first and second elements to power first and second beams at a first frequency, and sequentially operating third and fourth elements to power third and fourth beams at the first frequency; wherein the first, second, third, and fourth beams directed to first, second, third, and fourth coverage areas of the region, respectively; and wherein the second coverage area overlaps the first and third coverage areas, and the third coverage area overlaps the second and fourth coverage areas.

13. The method of claim 12, further comprising using an RF lens to direct the first, second, third, and fourth beams to the first, second, third, and fourth coverage areas, respectively.

14. The method of claim 12, further comprising concurrently operating the first and third elements to power the first and third beams, respectively.

15. The method of claim 12, further comprising sequentially operating the second and third elements to power the second and third beams, respectively.

16. The method of claim 12, further comprising using an 8x8 radio provide signals to each of the first, second, third, and fourth beams.

17. A method of adapting a beamforming system to a user device using a codebook-based feedback wireless transmission protocol, comprising: transmitting from a transmitting station a weighted sum of channel state information reference signals (CSI-RS) via at least a first beam; using information from the codebook to identify a matching beam from among the at least first beam; and receiving back from a receiving station, an index representing the identified matching beam.

18. The method of claim 17, further comprising using software to identify the matching beam.

19. The method of claim 17, further comprising using firmware to identify the matching beam.

20. A method of using a beamforming system with an array antenna based transmission protocol, wherein the transmission protocol uses a channel state information reference signal to identify a downlink beam, comprising: transmitting a first (CSI-RS) via a plurality of beams of the beamforming system, wherein the transmission encodes a phase gradient identifying a beam of the plurality of beams as the downlink beam; using the downlink beam to transmit information from the beamforming system to the user device receiving the phase gradient.

21. The method of claim 20, wherein the plurality of beams are formed with an RF lens.

22. The method of claim 20, wherein transmission protocol uses a codebook feedback.