Quadruple polarized antenna system

Abstract

To increase the gain of an antenna, an antenna array configuration adapted to separate spaces (sectors) via beams each having a different polarization and spatial multiplexing of the beams using the same is provided. The quadruple polarized antenna system includes a plurality of RF chains and an antenna array in which a row of first dual polarized antenna units and a row of second dual polarized antenna units are alternately arranged in a horizontal direction. The first dual polarized antenna units and the second dual polarized antenna units have different dual polarization characteristics. The row of first dual polarized antenna units is used to form at least one first beam and at least one second beam with a polarization of + / -45°, and the row of second dual polarized antenna units is used to form at least one third beam and at least one fourth beam with a polarization of 0 / 90°. The first beam, the second beam, the third beam, and the fourth beam are formed toward different spatial directions, and the first beam and the third beam correspond to a main lobe, and the second beam and the fourth beam correspond to a grating lobe.

Description

[Technical field]

[0001] The present invention relates to an array antenna system that can improve the orthogonality of wireless channels and increase the channel capacity of the system by spatially separating beams such that adjacent beams have dual polarizations that are different from each other. [Background technology]

[0002] The material described in this section is merely intended to provide background information related to the present invention and may not constitute prior art.

[0003] The polarization of an antenna refers to the direction of the electric field of the radio waves (i.e., the E-plane) relative to the Earth's surface and is determined at least in part by the physical structure and orientation of the antenna element. For example, a simple linear antenna element will have one polarization when mounted vertically and a different polarization when mounted horizontally. Although the magnetic field of the radio waves is at right angles to the electric field, by convention the polarization of an antenna element is understood to refer to the direction of the electric field.

[0004] In mobile communications, multiple-input multiple-output (MIMO) antennas are generally designed as dual-polarized antennas to reduce the fading effect caused by multipath and to perform polarization diversity. However, in a massive multi-input and multi-output (MIMO) system using multiple beams, the correlation coefficient of the wireless channel increases due to interference between adjacent beams, making it difficult to use spatial resources efficiently. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention presents an antenna array configuration suitable for isolating spaces (sectors) via beams each having a different polarization, and spatial multiplexing of the beams using the same, in order to increase the antenna gain. [Means for solving the problem]

[0006] The quadruple polarized antenna system according to the present invention includes a plurality of RF chains and an antenna array in which rows of first dual polarized antenna units and rows of second dual polarized antenna units are alternately arranged in a horizontal direction, the first dual polarized antenna units and the second dual polarized antenna units having different dual polarization characteristics.

[0007] The first array of dual polarized antenna units is used to form at least one first beam and at least one second beam with + / -45° polarization, and the second array of dual polarized antenna units is used to form at least one third beam and at least one fourth beam with 0° / 90° polarization, the first beam and the third beam corresponding to a main lobe, and the second beam and the fourth beam corresponding to a grating lobe.

[0008] The first beam, the second beam, the third beam, and the fourth beam are formed in different spatial directions. The first beam and the second beam are not spatially adjacent to each other, and the third beam and the fourth beam are not spatially adjacent to each other. Each of the first beam and the second beam is formed adjacent to at least one of the third beam and the fourth beam.

[0009] The first dual polarized antenna unit includes first and second antenna elements that intersect perpendicularly to each other, and the second dual polarized antenna unit includes third and fourth antenna elements that intersect perpendicularly to each other, and the antenna elements of the first dual polarized antenna unit are at an angle of 45 degrees to the antenna elements of the second dual polarized antenna unit.

[0010] In each of the first rows of dual polarized antenna units, the first antenna elements are connected to a feeder line to form a first subarray, the second antenna elements are connected to a feeder line to form a second subarray, and in each of the second rows of dual polarized antenna units, the third antenna elements are connected to a feeder line to form a third subarray, and the fourth antenna elements are connected to a feeder line to form a fourth subarray.

[0011] A pair of first subarrays in different columns connect to a first RF chain, a pair of second subarrays in different columns connect to a second RF chain, a pair of third subarrays in different columns connect to a third RF chain, and a pair of fourth subarrays in different columns connect to a fourth RF chain. The RF path difference (and therefore phase difference) to the RF chains between the pair of subarrays determines the direction of the beam. [Brief description of the drawings]

[0012] [Figure 1a] An example of a 4T4R antenna system using a dual polarized array is shown. [Figure 1b] 1 shows an exemplary spatially multiplexed beam pattern realized by the antenna system of FIG. 1a. [Figure 2a] 2 shows another example of a 4T4R antenna system using a dual polarized antenna array. [Figure 2b]2b shows an exemplary spatially multiplexed beam pattern implemented by the antenna system shown in FIG. 2a. [Figure 3a] 1 illustrates an example of a 4T4R antenna system using a quad-polarized antenna array according to one aspect of the present disclosure. [Figure 3b] 3b shows an exemplary spatially multiplexed beam pattern implemented by the antenna system shown in FIG. 3a. [Figure 4a] 1 illustrates an example of an 8T8R antenna system using a quadruple polarized antenna array in accordance with another aspect of the present disclosure. [Figure 4b] 4b shows an exemplary spatially multiplexed beam pattern implemented by the antenna system shown in FIG. 4a. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. When referring to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even if they are displayed in different drawings. In addition, when describing the present invention, if a detailed description of related known configurations or functions is considered to make the gist of the present invention unclear, the detailed description will be omitted.

[0014] The techniques of this disclosure relate to antenna array configurations that are useful for achieving spatial polarization separation such that adjacent beams have different dual polarization characteristics.

[0015] The antenna array according to the present disclosure includes a first dual polarized antenna unit and a second dual polarized antenna unit, the first dual polarized antenna unit and the second dual polarized antenna unit having different dual polarization characteristics.

[0016] The first dual polarized antenna unit is used to generate at least one first beam and at least one second beam, and the second dual polarized antenna unit is used to generate at least one third beam and at least one fourth beam. The first beam and the third beam correspond to a main lobe, and the second beam and the fourth beam correspond to a grating lobe. The first beam and the second beam have the same dual polarization characteristics, and the third beam and the fourth beam have the same dual polarization characteristics, while the first beam and the second beam have a different dual polarization characteristic from the third beam and the fourth beam.

[0017] The first to fourth beams are formed in different spatial directions, the first and third beams correspond to a main lobe, and the second and fourth beams correspond to a grating lobe.

[0018] The first beam and the second beam are not spatially adjacent to each other, and the third beam and the fourth beam are not spatially adjacent to each other. Meanwhile, each of the first beam and the second beam is formed adjacent to at least one of the third beam and the fourth beam. Therefore, the beams adjacent in space have different dual polarization characteristics from each other, and the interference between the adjacent beams is effectively reduced compared to when the adjacent beams have the same dual polarization characteristics.

[0019] To better understand the technical usefulness of the proposed technique, it is useful to start with a description of the solutions considered for forming beams with different polarization characteristics in an antenna system using a dual polarized array.

[0020] FIG. 1a shows an example of a 4T4R antenna system using a dual polarized array, and FIG. 1b shows an exemplary spatially multiplexed beam pattern realized by the antenna system of FIG. 1a.

[0021] The dual polarized antenna array shown in FIG. 1a is composed of two rows of dual polarized antenna units. Each dual polarized antenna unit includes a first antenna element 101a with +45° polarization and a second antenna element 101b with -45° polarization. In each row, the antenna elements are connected to a feeder line according to polarization. That is, in each row, the first antenna element 101a with +45° polarization is connected to a first feeder line 111a to form a first subarray, and the second antenna element 101b with -45° polarization is connected to a second feeder line 111b to form a second subarray. Thus, in the dual polarized antenna array shown in FIG. 1a, the antenna elements are divided into four subarrays. The four subarrays are respectively connected to four antenna ports via feeder lines. Each antenna port is connected to a respective RF chain. Each of the RF chains includes RF elements such as low noise amplifiers (LNAs) and power amplifiers (PAs), filters, etc., and provides an RF transmit path and an RF receive path. Thus, the antenna system of Figure 1a is a 4T4R.

[0022] The spacing between antenna elements with the same polarization characteristics is typically 0.5λ, where λ is the wavelength at the center frequency point of the frequency band of the antenna array. To ensure weak correlation, the larger the spacing, the better. That is, in the illustrated diagram, the spacing between adjacent rows is 0.5λ to 1λ.

[0023] Through polarization synthesis of signals S1-S4 and phase adjustment in the digital domain (e.g., in a digital unit) for the desired beam direction, two beams with different dual polarization characteristics (i.e., a first beam with + / -45° polarization and a second beam with V / H polarization) are formed in different spatial directions from the dual polarized antenna array shown in FIG. 1a.

[0024] In FIG. 1b, a beam in the upper left direction of the + / -45° polarization is formed by providing S1 signals having different phases to the first and third antenna ports and S2 signals having different phases to the second and fourth antenna ports. In FIG. 1b, a beam in the upper right direction of the V / H polarization is formed by providing S3 signals having different phases and S4 signals having different phases to the first to fourth antenna ports. When S3 signals having different phases are radiated from a subarray of the antenna array, a 90° (V) polarization is formed as a result of polarization synthesis, and when S4 signals having different phases are radiated from a subarray of the antenna array, a 0° (H) polarization is formed as a result of polarization synthesis. A specific method for forming a beam having + / -45° polarization and V / H polarization using a dual-polarized antenna array is disclosed, for example, in Korean Patent Application No. 10-2020-0046256 filed by the applicant on April 16, 2020.

[0025] Referring to FIG. 1b, beams having a beam width of about 40° with respect to the horizontal plane are formed toward different directions. In particular, adjacent beams have different dual polarization characteristics. The ±45° notation in FIG. 1b to indicate the dual polarization characteristics of each beam indicates that the beam has +45° polarization and -45° polarization, and V / H indicates that the beam has 90° (V) polarization and 0° (H) polarization. This is the same in other figures. For example, a beam formed toward the upper left has a radio signal with +45° polarization and a radio signal with -45° polarization, and a beam formed toward the upper right has a radio signal with 90° polarization and a radio signal with 0° polarization.

[0026] The antenna system of Fig. 1a increases the capacity compared to the legacy antenna system that forms four beams (65 degree beam width) with the same dual polarization characteristics. In the frequency band above 3.5 GHz, the space of the box is large compared to the space occupied by the dual polarized antenna unit, which is inefficient. Therefore, in order to actively utilize the free space of the box, an antenna array with more subarrays as shown in Fig. 2a is considered.

[0027] FIG. 2a shows another example of a 4T4R antenna system using a dual polarized antenna array, and FIG. 2b shows an exemplary spatially multiplexed beam pattern realized by the antenna system shown in FIG. 2a.

[0028] The antenna array shown in FIG. 2a is composed of four rows of dual polarized antenna units. Each dual polarized antenna unit includes a first antenna element with +45° polarization and a second antenna element with -45° polarization. In each row, the antenna elements are connected to a feeder line according to polarization to form a first subarray and a second subarray. Thus, in the dual polarized antenna array shown in FIG. 2a, the antenna elements are divided into eight subarrays. The eight subarrays are respectively connected to eight antenna ports via feeder lines. The eight antenna ports are connected to four RF chains via an RF matrix. Thus, the antenna system of FIG. 2a is 4T4R.

[0029] The antenna system of Fig. 2a forms four independent beams (i.e., two beams with + / -45° polarization and two beams with V / H polarization) in different spatial directions through polarization reconfiguration of the RF matrix. The RF matrix is ​​realized by passive elements such as hybrid couplers, directional couplers, and phase shifters. The function of the RF matrix may be realized by processing the baseband signals in the digital domain, similar to the antenna system of Fig. 1a.

[0030] Referring to Figure 2b, four beams with a beam width of about 40° are formed in different directions relative to the horizontal plane. In particular, adjacent beams have different dual polarization characteristics. For example, + / -45° beams and 0° / 90° beams are formed alternately from the left.

[0031] As described above, an antenna system using a dual polarized antenna array can spatially separate beams having different dual polarization characteristics through signal processing in the digital domain or RF domain. However, separate hardware is required to implement polarization synthesis / separation performed in the digital domain, which increases heat generation in the antenna system. Polarization reconstruction using an RF matrix involves losses due to elements that make up the matrix, making it difficult to maintain accurate beam spacing.

[0032] As discussed above, the present disclosure presents antenna array configurations useful for achieving spatial polarization separation such that adjacent beams have different dual polarization characteristics.

[0033] FIG. 3a illustrates an example of a 4T4R antenna system using a quad-polarized antenna array according to one aspect of the present disclosure, and FIG. 3b illustrates an example spatially multiplexed beam pattern realized by the antenna system illustrated in FIG. 3a.

[0034] The antenna array illustrated in FIG. 3a is composed of a first dual polarized antenna unit and a second dual polarized antenna unit. The first dual polarized antenna unit and the second dual polarized antenna unit have different dual polarization characteristics. For example, the first dual polarized antenna unit includes a first antenna element 301a with +45° polarization and a second antenna element 301b with -45° polarization, and the second dual polarized antenna unit includes a first antenna element 302a with V (90°) polarization and a second antenna element 302b with H (0°) polarization. Therefore, the antenna array according to the present disclosure is referred to as a "quadruple polarized antenna array."

[0035] In the antenna array shown in Figure 3a, rows of +45° / -45° dual polarized antenna units and rows of V / H dual polarized antenna units are alternately arranged. That is, +45° / -45° dual polarized antenna units and V / H dual polarized antenna units are alternately arranged in the horizontal direction, and antenna units having the same dual polarization characteristics are arranged in the vertical direction. In other words, adjacent rows of dual polarized antenna units have different dual polarization characteristics.

[0036] In each row, the antenna elements are connected to a feeder line for each polarization to form a first subarray and a second subarray.

[0037] Specifically, in a row of +45° / -45° dual polarized antenna units (i.e., the first row and the third row), the first antenna element 301a with +45° polarization is connected to the first feeder line 311a to form a first subarray, and the second antenna element 301b with -45° polarization is connected to the second feeder line 311b to form a second subarray. In a row of V / H dual polarized antenna units (i.e., the second row and the fourth row), the first antenna element 302a with V polarization is connected to the first feeder line 312a to form a first subarray, and the second antenna element 302b with H polarization is connected to the second feeder line 312b to form a second subarray. Thus, in the quadruple polarized antenna array illustrated in FIG. 3a, the antenna elements are divided into eight subarrays. The eight subarrays are respectively connected to eight antenna ports via feeder lines. The eight antenna ports are connected to four RF chains. Therefore, the antenna system in Fig. 3a is a 4T4R. The number of RF chains is equal to the sum of the number of rows of the first dual polarized antenna unit and the number of rows of the second dual polarized antenna unit.

[0038] To form beams for each polarization, one RF chain is applied to two subarrays with the same polarization arranged alternately. The direction of the beam is determined by the RF path difference (and therefore the phase difference) between the two subarrays to the RF chains, without the need for a separate phase shifter.

[0039] It should be noted that the spacing d between two subarrays having the same polarization is greater than λ. For example, the spacing d between two subarrays is 1.5λ to 2λ, where λ is the wavelength of the center frequency point of the frequency band of the antenna array. In such an arrangement, in addition to the main lobe generated in the desired beam direction, a grating lobe is generated, which is a side lobe whose phase is a multiple of 2π and whose size is comparable to that of the main lobe. The direction in which the grating lobe is generated is determined by the spacing d between the subarrays, the wavelength λ, and the beam steering angle θ in the desired beam direction in which the main lobe is generated.

[0040] The antenna system of the present disclosure takes advantage of the typically attenuating grating lobes to form a beam pattern similar to that of FIG. 2b.

[0041] Referring to FIG. 3a, the antenna ports of the antenna elements with +45° polarization in the first row and the antenna ports of the antenna elements with +45° polarization in the third row are coupled to a first RF chain to form a beam with +45° polarization. The antenna ports of the antenna elements with -45° polarization in the first row and the antenna ports of the antenna elements with -45° polarization in the third row are coupled to a second RF chain to form a beam with -45° polarization. A main lobe of the beam with +45° polarization and a main lobe of the beam with -45° polarization are formed in the first spatial direction, and a grating lobe of the beam with +45° polarization and a grating lobe of the beam with -45° polarization are formed in the second spatial direction, so that there are dual polarizations of +45° / -45° in two spatial directions.

[0042] Then, the antenna port connected to the antenna elements having H (0°) polarization in the second row and the antenna port connected to the antenna elements having H (0°) polarization in the fourth row are coupled to a third RF chain to form a beam of H (0°) polarization. The antenna port connected to the antenna elements having V (90°) polarization in the second row and the antenna port connected to the antenna elements having V (90°) polarization in the fourth row are coupled to a fourth RF chain to form a beam of V (90°) polarization. The main lobe of the beam of H (0°) polarization and the main lobe of the beam of V (90°) polarization are formed toward the third spatial direction, and the grating lobe of the beam of H (0°) polarization and the grating lobe of the beam of V (90°) polarization are formed toward the fourth spatial direction, so that H / V dual polarization exists in two spatial directions.

[0043] Referring to FIG. 3b, four beams are formed in different directions based on the horizontal plane. In particular, adjacent beams have different dual polarization characteristics, for example, from the left side, a dual polarization beam of + / -45° and a dual polarization beam of 0° / 90° are alternately formed. One of the dual polarization beams of + / -45° is due to the main lobe, and the other is due to the grating lobe. Furthermore, one of the dual polarization beams of 0° / 90° is due to the main lobe, and the other is due to the grating lobe.

[0044] The antenna system shown in Fig. 3a can achieve spatial multiplexing of polarized beams by configuring a simple combiner that connects subarrays of antenna elements to an RF chain in the RF domain. Since the formation of spatially multiplexed beam patterns can be realized with a pure RF circuit configuration, no hardware is required for signal processing compared to the antenna system shown in Fig. 1a, which must be realized in the digital domain, and the resulting heat generation problem is also improved. Furthermore, compared to the antenna system shown in Fig. 2a, it is possible to maintain accurate inter-beam spacing, and the overlapping area between beams that affects the SINR can be minimized.

[0045] Figure 4a shows an example of an 8T8R antenna system using a quadruple polarized antenna array in accordance with another aspect of the present disclosure, and Figure 4b shows an example spatially multiplexed beam pattern realized by the antenna system shown in Figure 4a. The RF chain and digital unit are omitted from Figure 4a to highlight the configuration of the antenna array.

[0046] The antenna array shown in Figure 4a includes four rows of +45° / -45° dual polarized antenna units and four rows of V / H dual polarized antenna units, which are arranged alternately with each other, i.e., +45° / -45° antenna units and V / H antenna units are arranged alternately in the horizontal direction, and antenna units with the same dual polarization characteristics are arranged in the vertical direction.

[0047] In each row, the antenna elements are connected to a feeder line for each polarization to form a first subarray and a second subarray. Thus, in the quadruple polarized antenna array shown in FIG. 4a, the antenna elements are divided into 16 subarrays. The 16 subarrays are connected to 16 antenna ports via feeder lines. The 16 antenna ports are connected to 8 RF chains (not shown).

[0048] To form a beam for each polarization, one RF chain is applied to two subarrays with the same polarization located in different rows. The RF path difference (and therefore phase difference) between the two subarrays to the RF chain determines the direction of the beam.

[0049] In order to support beam directions of various angles, the horizontal spacing between subarrays combined into one RF chain is larger than that of FIG. 3a. For example, an antenna port connected to an antenna element having a polarization of +45° in the first row and an antenna port connected to an antenna element having a polarization of +45° in the fifth row are combined into one RF chain to form a beam of +45° polarization. An antenna port connected to an antenna element having a polarization of H(0°) in the second row and an antenna port connected to an antenna element having a polarization of H(0°) in the sixth row are combined into one RF chain. Referring to FIG. 4b, eight beams are formed in different directions based on the horizontal plane, and adjacent beams have different dual polarizations. As described above, four of the eight beams are due to grating lobes.

[0050] The above description is merely an illustrative example of the technical ideas of the embodiments of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the present embodiment is for the purpose of illustrating, rather than limiting, the technical ideas of the present invention, and the scope of the technical ideas of the present invention is not limited by such embodiments. The scope of protection of the present invention should be interpreted according to the claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

[0051] [CROSS REFERENCE TO RELATED APPLICATIONS] This patent application claims priority to Patent Application No. 10-2021-0039618 filed in Korea on March 26, 2021, and Patent Application No. 10-2022-0036777 filed in Korea on March 24, 2022, the entireties of which are incorporated by reference into this specification.

Claims

1. A plurality of RF chains; and an antenna array in which a row of first dual polarized antenna units and a row of second dual polarized antenna units are alternately arranged in a horizontal direction; the first dual polarized antenna unit and the second dual polarized antenna unit have different dual polarization characteristics; the first array of dual polarized antenna units is used to form at least one first beam and at least one second beam having +45° and −45° polarizations, and the second array of dual polarized antenna units is used to form at least one third beam and at least one fourth beam having 0° and 90° polarizations; the first beam, the second beam, the third beam, and the fourth beam are formed in different spatial directions, the first beam and the third beam correspond to a main lobe, and the second beam and the fourth beam correspond to a grating lobe; the first dual polarized antenna unit includes a first antenna element and a second antenna element that cross each other perpendicularly, and the second dual polarized antenna unit includes a third antenna element and a fourth antenna element that cross each other perpendicularly; the plurality of RF chains includes a first RF chain, a second RF chain, a third RF chain, and a fourth RF chain; In each of the first rows of dual polarized antenna units, the first antenna elements are connected to a feeder line to form a first subarray, and the second antenna elements are connected to a feeder line to form a second subarray; In each of the second rows of dual polarized antenna units, the third antenna elements are connected to a feeder line to form a third subarray, and the fourth antenna elements are connected to a feeder line to form a fourth subarray; a pair of first subarrays located in different columns are connected to the first RF chain, a pair of second subarrays located in different columns are connected to the second RF chain, a pair of third subarrays located in different columns are connected to the third RF chain, and a pair of fourth subarrays located in different columns are connected to the fourth RF chain; A quadruple polarized antenna system, wherein the directions of the first beam to the fourth beam are defined by an RF path difference from one subarray and the other subarray of the pair to corresponding RF chains in the pair of first to fourth subarrays.

2. 2. The quadruple polarized antenna system of claim 1, wherein the first beam and the second beam are not spatially adjacent to one another and the third beam and the fourth beam are not spatially adjacent to one another.

3. 2. The quadruple polarized antenna system of claim 1, wherein each of the first beam and the second beam is formed adjacent to at least one of the third beam and the fourth beam.

4. 2. The quadruple polarized antenna system of claim 1, wherein the antenna elements of said first dual polarized antenna unit are at a 45 degree angle to the antenna elements of said second dual polarized antenna unit.

5. 2. The quadruple polarized antenna system of claim 1, wherein the number of RF chains is equal to the sum of the number of rows of the first dual polarized antenna units and the number of rows of the second dual polarized antenna units.

Images