4-Polarization Diversity Antenna System

Abstract

To provide an antenna array suitable for spatial separation via beams each having a different polarization in order to increase antenna gain, an antenna panel configuration in which the antenna array is arranged, and spatial multiplexing of beams using the same. The polarization diversity antenna system includes an antenna array including a first row of dual polarized antenna units and a second row of dual polarized antenna units. Each of the dual polarized antenna units includes a first antenna element and a second antenna element that are perpendicularly intersecting each other. In each row, the first antenna elements are conductively connected to form a first subarray, and the second antenna elements are conductively connected to form a second subarray. The antenna system further includes an RF matrix that selectively adjusts a phase of an RF input signal to generate an RF output signal that is provided to the subarray. When the RF output signal is radiated by the dual polarized antenna units, a first beam having a + / -45° polarization and a second beam having a 0° / 90° polarization are formed, and the first beam and the second beam are formed toward different spatial directions from each other.

Description

Technical Field

[0001] The present invention relates to a quadruple polarization diversity antenna system that can improve the orthogonality of a radio channel and increase the channel capacity of a system by adjusting the polarization of beams so that spatially adjacent beams have different dual-polarization characteristics.

Background Art

[0002] The content described in this part only provides background information related to the present invention and does not constitute prior art.

[0003] The polarization of an antenna refers to the direction of the electric field (E-plane) of the radio wave with respect to the Earth's surface and is determined at least partially depending on the physical structure and direction of the antenna element. For example, a simple linear antenna element has one polarization when mounted vertically and a different polarization when mounted horizontally. The magnetic field of the radio wave is perpendicular to the electric field, but conventionally, the polarization of the antenna element is understood to indicate the direction of the electric field.

[0004] In mobile communication, MIMO (multiple-input multiple-output) antennas are generally designed as dual-polarized antennas to reduce the fading effect caused by multipath and perform a polarization diversity function. However, in a Massive MIMO system that uses multiple beams, the correlation coefficient of the radio channel becomes high due to interference between adjacent beams, making it difficult to efficiently use spatial resources.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure aims to present an antenna array suitable for separating a space (or sector) via beams having different polarization states to increase the gain of an antenna, a configuration of an antenna panel in which the antenna arrays are arranged, and spatial multiplexing of beams using the same.

Means for Solving the Problem

[0006] According to an embodiment of the present disclosure, an antenna system includes an antenna array including a first row of dual-polarization antenna units and a second row of dual-polarization antenna units. Each of the dual-polarization antenna units includes a first antenna element and a second antenna element that are perpendicular to each other. In each row, the first antenna elements are conductively connected to form a first sub-array, and the second antenna elements are conductively connected to form a second sub-array. The antenna system further includes an RF matrix that selectively adjusts the phase of an RF input signal and generates an RF output signal provided to the sub-arrays. When the RF output signal is radiated by the dual-polarization antenna unit, a first beam having a + / -45° polarization and a second beam having a 0° / 90° polarization are formed, and the first beam and the second beam are formed in spatially different directions from each other.

[0007] The RF matrix is implemented by a quadrature hybrid coupler (QHD) formed on a PCB. The RF matrix is configured to selectively adjust the phases of the plurality of branch signals based on a phase difference for forming the first beam and the second beam and a phase difference for determining the polarizations of the first beam and the second beam.

[0008] Among the RF input signals, the phases adjusted by the RF matrix circuit for a pair of RF input signals propagated by the first beam are defined with respect to the desired spatial direction in which the first beam is formed. Among the RF input signals, the phases adjusted by the RF matrix circuit for a pair of RF input signals propagated by the second beam are defined for the desired spatial direction in which the second beam is formed and for polarization synthesis.

[0009] The dual-polarized antenna unit has + / -45° polarization characteristics, and the 0° / 90° polarization of the second beam is obtained by polarization synthesis.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4a

Figure 4b

Figure 4c

Figure 5a

Figure 5b

Figure 6a

Figure 6b

Figure 6c

Figure 6d

Figure 6e

Figure 7a

Figure 7b

Embodiments for Carrying Out the Invention

[0011] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. Note that when adding reference numerals to the components of each drawing, for the same components, even if they are shown on other drawings, they are given the same reference numerals as much as possible. In addition, when explaining the present invention, if it is determined that a specific explanation of related known configurations or functions obscures the gist of the present invention, the detailed explanation thereof will be omitted.

[0012] The present disclosure relates to a polarization diversity antenna system suitable for separating a space (sector) via beams having different polarizations in order to increase the gain of an antenna.

[0013] To better understand the technical utility of the proposed technology, it is useful to begin with an explanation of solutions considered for forming beams having different polarization characteristics in an antenna system using a dual-polarization antenna array.

[0014] FIG. 1 illustrates a conventional 4T4R polarization diversity antenna system using a +45° / -45° dual-polarization antenna array. The antenna system of FIG. 1 can achieve quadruple polarization diversity through polarization synthesis in the digital domain. FIG. 2 shows the space-division multiplexed beam pattern formed by the antenna system of FIG. 1.

[0015] Referring to FIG. 1, the antenna array employed in the antenna system is composed of two columns of dual-polarization antenna units. Each dual-polarization antenna unit includes a first antenna element 101a with a +45° polarization and a second antenna element 101b with a -45° polarization. That is, two columns of dual-polarization antenna units including a +45° linear radiation element and a -45° linear radiation element form the antenna array. In each column, the antenna elements 101a, 101b are connected to feeder lines 111a, 111b for each polarization. That is, in each column, the first antenna element 101a with a +45° polarization is conductively connected to the first feeder line 111a to form a first sub-array, and the second antenna element 101b with a -45° polarization is conductively connected to the second feeder line 111b to form a second sub-array. Therefore, in the dual-polarization antenna array illustrated in FIG. 1, the antenna elements 101a, 101b are divided into four sub-arrays.

[0016] The four sub-arrays are respectively connected to four antenna ports through feeder lines 111a and 111b. Each antenna port is connected to a respective RF chain 130. Each of the RF chains 130 includes RF elements such as an LNA (low noise amplifier) and a PA (power amplifier), and a filter, and provides an RF transmission path and an RF reception path. Therefore, the antenna system in FIG. 1 is 4T4R.

[0017] The spacing distance between antenna elements having the same polarization characteristic is generally 0.5λ, where λ is the wavelength at the center frequency point of the frequency band of the antenna array. To ensure a weak correlation relationship, the larger the spacing distance, the better. That is, in the illustrated figure, the spacing distance between adjacent columns is 0.5λ to 1λ.

[0018] The antenna system in FIG. 1 forms, from a dual-polarization antenna array, two beams having different dual-polarization characteristics (that is, a first beam of + / -45° orthogonal polarizations and a second beam having V / H orthogonal polarizations) in different spatial directions through polarization synthesis for signals T1 to T4 and phase adjustment in the digital domain (for example, digital unit 120) for a desired beam direction.

[0019] As illustrated in FIG. 2, beams having a beam width of approximately 40° with respect to the horizontal plane are formed in different spatial directions (in FIG. 2, the 10 o'clock direction and the 2 o'clock direction). The dual-polarization characteristics of the beam in the 10 o'clock direction and the beam in the 2 o'clock direction are different from each other. In particular, these beams have significant sidelobes.

[0020] The ±45° notations shown in Fig. 2 to indicate the dual polarization characteristics of each beam indicate that the beam has two orthogonal polarizations composed of a +45° linear polarization and a -45° linear polarization, and V / H indicates that the beam has two orthogonal polarizations composed of a 90° (V) linear polarization and a 0° (H) linear polarization. For example, the beam formed in the 10 o'clock direction has radio waves of +45° polarization and radio waves of -45° polarization, and the beam formed in the 2 o'clock direction has radio waves of 90° polarization and radio waves of 0° polarization. This is the same in other figures. However, strictly speaking, "a beam of + / -45° orthogonal polarization is formed in the 10 o'clock direction" means that a beam of +45° linear polarization and a beam of -45° linear polarization are formed in the 10 o'clock direction, and "a beam of V / H orthogonal polarization is formed in the 2 o'clock direction" means that a beam of 90° (V) linear polarization and a beam of 0° (H) linear polarization are formed in the 2 o'clock direction.

[0021] In Fig. 2, the beam of the 10 o'clock direction with + / -45° orthogonal polarization is formed by providing T1 signals with different phases to the first and third antenna ports and T2 signals with different phases to the second and fourth antenna ports.

[0022] In Fig. 2, the beam of the 2 o'clock direction with V / H orthogonal polarization is formed by providing a T3 signal with a different phase and a T4 signal with a different phase to the first to fourth antenna ports. When the T3 signal with a different phase is radiated from the four sub-arrays of the antenna array, a 90° (V) polarization is formed as a result of polarization synthesis. Similarly, when the T4 signal with a different phase is radiated from the four sub-arrays of the antenna array, a 0° (H) polarization is formed as a result of polarization synthesis.

[0023] Note that, contrary to what is illustrated in Fig. 2, phase adjustment in the digital unit may be made such that the beam in the 10 o'clock direction has V / H orthogonal polarization and the beam in the 2 o'clock direction has + / -45° orthogonal polarization.

[0024] The antenna system illustrated in FIG. 1 is implemented by adding a digital process function for performing polarization separation / combination and beamforming in the digital domain to an AAS (Active Antenna System) or an RRA (Remote Radio Antenna) system integrated with an RRH (Remote Radio Head). The antenna system illustrated in FIG. 1 requires hardware for implementing beamforming and polarization combination / separation performed in the digital domain, thereby increasing heat generation. A specific method of forming beams having + / -45° orthogonal polarization and V / H orthogonal polarization from a dual-polarized antenna array through phase adjustment in the digital domain (for example, a digital unit) is disclosed, for example, in Korean Patent Application No. 10-2020-0046256 filed on April 16, 2020 by the applicant of the present application.

[0025] FIG. 3 illustrates a 4T4R polarization diversity antenna system according to an embodiment of the present invention using a + / -45° dual-polarized antenna array. The antenna system illustrated in FIG. 3 generates two independent beams (i.e., a beam having + / -45° orthogonal polarization and a beam having V / H orthogonal polarization) in different spatial directions through RF signal processing including phase adjustment for signals in the RF domain.

[0026] The antenna array employed in the antenna system of FIG. 3 is substantially the same as the antenna array employed in the antenna system of FIG. 1. That is, in FIG. 3, the antenna array is composed of two columns of dual-polarized antenna units. Each dual-polarized antenna unit includes a first antenna element 301a with +45° polarization and a second antenna element 301b with -45° polarization. In each column, the antenna elements 301a, 301b are connected to feeder lines 311a, 311b for each polarization. Therefore, in the dual-polarized antenna array illustrated in FIG. 3, the antenna elements 301a, 301b are divided into four sub-arrays.

[0027] Transmission signals T1, T2, T3, and T3 from the digital unit 320 are supplied to four RF chains 330. The RF signals output from the RF chains 330 are supplied to four sub-arrays of the antenna array after undergoing signal processing in an RF matrix 340. Therefore, the antenna system in FIG. 3 is 4T4R.

[0028] The RF matrix 340 is configured to perform signal processing including signal splitting and phase adjustment on the RF signals input from the RF chains 330. The RF matrix 340 is implemented by passive elements such as hybrid couplers, directional couplers, and phase shifters. The signal-processed RF signals output from the RF matrix 340 are radiated spatially through the four sub-arrays of the antenna array, and as a result, two independent beams (i.e., a beam having + / -45° orthogonal polarization and a beam having V / H orthogonal polarization) in different spatial directions as illustrated in FIG. 2 are generated. It should be noted that, contrary to what is illustrated in FIG. 2, phase adjustment in the RF matrix 340 may be performed such that the beam in the 10 o'clock direction has V / H orthogonal polarization and the beam in the 2 o'clock direction has + / -45° orthogonal polarization.

[0029] The antenna system in FIG. 3 is implemented not only in an AAS / RRA system having an RF circuit in which the RF matrix 340 is formed, but also in a form in which an RF circuit board in which the RF matrix 340 is formed is disposed between a legacy antenna system and an RRH. Therefore, existing legacy antenna systems can also be easily modified to support quadruple polarization diversity. However, there is RF loss due to the RF matrix 340, and it is difficult to maintain an accurate interval between the beams.

[0030] On the other hand, the antenna array illustrated in FIG. 3 has two columns of dual-polarization antenna units, but in other implementations, the antenna array may have more columns in order to form more beams or to form a narrower beam width.

[0031] Referring now to FIGS. 4a, 4b, and 4c, the RF matrix 340 provides for RF signals for polarization synthesis and a desired beam direction in the 4T4R polarization diversity antenna system of FIG. 3, and signal processing including phase shifts will be described.

[0032] FIG. 4a is a conceptual diagram that schematically represents the RF domain of the antenna system of FIG. 3 for convenience of explanation. FIG. 4b illustrates a pair of beams formed by the antenna system of FIG. 3 and the input signals involved in forming these beams. The table of FIG. 4c shows the phase shifts that the input signals T1, T2, T3, T4 undergo as they reach the sub-arrays of the antenna array via the RF matrix 340 to form the pair of beams shown in FIG. 4b.

[0033] Referring to FIGS. 4a and 4b, the input signals T1, T2 form a first beam having a + / -45° orthogonal polarization via the RF matrix 340, and the input signals T3, T4 form a second beam having a V / H polarization via the RF matrix 340. The upper two beams have different spatial directions. In FIG. 4b, the first beam having a + / -45° orthogonal polarization is directed in the 10 o'clock direction, and the beam having a V / H orthogonal polarization is directed in the 2 o'clock direction.

[0034] To form the beam pattern illustrated in FIG. 4b, the signal processing that the RF matrix 340 performs on the input signals T1, T2, T3, T4, in other words, the phase shifts that the input signals T1, T2, T3, T4 undergo as they reach the sub-arrays of the antenna array through the RF matrix 340, are as follows.

[0035] The target polarization of the input signal T1 is a +45° polarization, and it is provided via the RF matrix 340 to the sub-array of +45° polarized antenna elements in the first column (C1; left column) (which is denoted as "C1 +45" in the table of FIG. 4b) and the sub-array of +45° polarized antenna elements in the second column (C2; right column) (which is denoted as "C2 +45" in the table of FIG. 4b).

[0036] The target polarization of the input signal T2 is -45° polarization, and it is provided to the sub-array of -45° polarized antenna elements in the first column C1 (which is denoted as "C1 -45" in the table of FIG. 4b) and the sub-array of -45° polarized antenna elements in the second column C2 (C2 -45) via the RF matrix 340.

[0037] The target polarization of the input signal T3 is H polarization, and the target polarization of the input signal T4 is V polarization. The input signals T3 and T4 are respectively provided to the four sub-arrays (C1 +45; C1 -45; C2 +45; C2 -45) of the dual-polarized array via the RF matrix 340.

[0038] The input signal T1 is split by the RF matrix 340 into two branch signals. One branch signal reaches the sub-array (C1 +45) with +45° polarization in the first column without phase shift, and the other branch signal reaches the sub-array (C2 +45) with +45° polarization in the second column after receiving a -90° phase shift. Since the target polarization of the input signal T1 is +45° polarization, the -90° phase shift is solely for beamforming. The two branch signals corresponding to the input signal T1 are radiated by the sub-arrays (C1 +45, C2 +45) while having a -90° phase difference with each other, thus forming a beam with +45° polarization in a spatial direction inclined by about 30° to the left with respect to the normal of the antenna array.

[0039] The input signal T2 is split by the RF matrix 340 into two branch signals. One branch signal reaches the sub-array (C1 -45) with -45° polarization in the first column without phase shift, and the other branch signal reaches the sub-array (C2 -45) with -45° polarization in the second column after receiving a -90° phase shift. Since the target polarization of the input signal T2 is -45° polarization, the -90° phase shift is solely for beamforming.

[0040] The two branch signals corresponding to the input signal T2 are radiated by the sub-arrays (C1 -45, C2 -45) while having a phase difference of -90° from each other, so a beam with a -45° polarization is formed in the spatial direction inclined about 30° to the left with respect to the normal of the antenna array.

[0041] The input signal T3 is branched into four branch signals by the RF matrix 340. The first branch signal reaches the sub-array (C1 +45) of the first column without phase shift. The second, third, and fourth branch signals reach the sub-array (C1 -45) of the first column, the sub-array (C2 +45) of the second column, and the sub-array (C2 -45) of the second column, respectively, after receiving phase shifts of 180°, 90°, and 270°. The phase shift (180°) of the second branch signal is solely for polarization synthesis. The phase shift (90°) of the third branch signal is solely for beamforming. The phase shift (270°) of the fourth branch signal is the sum of the phase shift (90°) for beamforming and the phase shift (180°) for polarization synthesis.

[0042] The first and second branch signals corresponding to the input signal T3 are radiated by the sub-arrays (C1 +45, C1 -45) of the first column C1 while having a phase difference of 180°, so a beam with a 0° (H) polarization is formed (i.e., polarization synthesis occurs). The third and fourth branch signals are radiated by the sub-arrays (C1 +45, C1 -45) of the first column (C1) while having a phase difference of 180°, so a beam with a 0° (H) polarization is formed (i.e., polarization synthesis occurs). Also, the first branch signal radiated by the sub-array (C1 +45) of the first column and the third branch signal radiated by the sub-array (C2 +45) of the second column have a phase difference of +90° from each other. The second branch signal radiated by the sub-array (C1 -45) of the first column and the fourth branch signal radiated by the sub-array (C2 -45) of the second column have a phase difference of +90° from each other. Therefore, a beam with a 0° (H) polarization is formed in the spatial direction inclined about 30° to the right with respect to the normal of the antenna array.

[0043] The input signal T4 is branched into four branch signals by the RF matrix 340. The first branch signal reaches the sub-array (C1 +45) of the first column without phase shift. The second branch signal, the third branch signal, and the fourth branch signal reach the sub-array (C1 -45) of the first column, the sub-array (C2 +45) of the second column, and the sub-array (C2 -45) of the third column, respectively, after receiving phase shifts of 180°, 90°, and 270°.

[0044] The first branch signal and the second branch signal corresponding to the input signal T4 are radiated by the sub-arrays (C1 +45, C1 -45) of the first column C1 while maintaining a phase difference of 0°, thus forming a beam having a 90° (V) polarization (i.e., polarization synthesis occurs). The third branch signal and the fourth branch signal are radiated by the sub-arrays (C1 +45, C1 -45) of the first column C1 while maintaining a phase difference of 0°, thus forming a beam having a 90° (V) polarization (i.e., polarization synthesis occurs). Also, the first branch signal radiated by the sub-array (C1 +45) of the first column and the third branch signal radiated by the sub-array (C2 +45) of the second column have a phase difference of +90° with respect to each other, and the second branch signal radiated by the sub-array (C1 -45) of the first column and the fourth branch signal radiated by the sub-array (C2 -45) of the second column have a phase difference of +90° with respect to each other. Therefore, a beam having a 90° polarization is formed in a spatial direction inclined to the right by approximately 30° with respect to the normal of the antenna array.

[0045] Figure 5a is an example of an RF matrix 500 implemented using a quadrature hybrid coupler (QHC) according to an aspect of the present disclosure. The QHC is also referred to as a "branch-line coupler" or a "90° Hybrid coupler". Figure 5b shows the pattern of the beam formed using the RF matrix 500 illustrated in Figure 5a and the dual polarization characteristics of the beam. It should be noted that the polarization characteristics of the beam illustrated in Figure 5b are opposite to those shown in Figure 4b. That is, in Figure 4b, the beam at the 10 o'clock direction has a +45° / -45° orthogonal polarization, while in Figure 5b, the beam at the 2 o'clock direction has a +45° / -45° orthogonal polarization. As mentioned in relation to Figure 2, strictly speaking, "a beam with a + / -45° orthogonal polarization is formed in the 2 o'clock direction" means that a beam with a +45° linear polarization and a beam with a -45° linear polarization are formed in the direction of the 2 o'clock, and "a beam with a V / H orthogonal polarization is formed in the 10 o'clock direction" means that a beam with a 90° (V) linear polarization and a beam with a 0° (H) linear polarization are formed in the direction of the 10 o'clock.

[0046] The RF matrix 500 illustrated in Figure 5a has four input ports (displayed as white circles) on a PCB, three QHCs 510a, 510b, 510c formed by conductive strips, and four output ports (displayed as black circles).

[0047] As shown in the enlarged view of Figure 5a, each of the QHCs 510a, 510b, 510c has four arms (i.e., the first arm to the fourth arm). When a signal is input to the first arm, outputs appear at the second arm and the third arm, and no output appears at the fourth arm. Also, there is a 90° (i.e., λ / 4) phase difference between the output signals of the second arm and the third arm. The QHCs 510a, 510b, 510c are in an up / down / left / right symmetric form. When a signal is input to the second arm, outputs appear at the first arm and the fourth arm, and no output is produced at the third arm. That is, it operates in a completely symmetric structure.

[0048] The input signal T1 reaches the sub-array (C1 +45) of the first column through "the first input port - the first arm of the first QHC510a - the second arm of the first QHC510a - the first output port". Also, the input signal T1 reaches the sub-array (C2 +45) of the second column through "the first input port - the first arm of the first QHC510a - (90° phase delay) - the third arm of the first QHC510a - the third output port". Therefore, from the perspective of the input signal T1, the radio signal radiated from the sub-array (C2 +45) of the second column has a 90° phase delay compared to the radio signal radiated from the sub-array (C1 +45) of the first column. As shown in FIG. 5b, a beam with a +45° polarization is formed in a spatial direction inclined approximately 30° to the right with respect to the normal of the antenna array.

[0049] The input signal T2 reaches the sub-array (C1 -45) of the first column through "the second input port - the first arm of the second QHC510b - the second arm of the second QHC510b - the second output port". Also, the input signal T2 reaches the sub-array (C2 -45) of the second column through "the second input port - the first arm of the second QHC510b - (90° phase delay) - the third arm of the second QHC510b - the fourth output port". Therefore, from the perspective of the input signal T2, the radio signal radiated from the sub-array (C2 -45) of the second column has a 90° phase delay compared to the radio signal radiated from the sub-array (C1 -45) of the first column. As shown in FIG. 5b, a beam with a +45° polarization is formed in a spatial direction inclined approximately 30° to the right with respect to the normal of the antenna array.

[0050] The input signal T3 reaches the sub-array (C1 +45) of the first column through "the third input port - the fourth arm of the third QHC510c - (90° phase delay) - the second arm of the third QHC510c - the fourth arm of the first QHC510a - (90° phase delay) - the second arm of the first QHC510a - the first output port". Also, the input signal T3 reaches the sub-array (C2 +45) of the second column through "the third input port - the fourth arm of the third QHC510c - (90° phase delay) - the second arm of the third QHC510c - the fourth arm of the first QHC510a - the third arm of the first QHC510a - the third output port". Also, the input signal T3 is supplied to the sub-array (C1 -45) of the first column through "the third input port - the fourth arm of the third QHC510c - the third arm of the third QHC510c - (90° phase delay) - the fourth arm of the second QHC510b - (90° phase delay) - the second arm of the second QHC510b - the second output port". Also, the input signal T3 is supplied to the sub-array (C2 -45) of the second column through "the third input port - the fourth arm of the third QHC510c - the third arm of the third QHC510c - (90° phase delay) - the fourth arm of the second QHC510b - the third arm of the second QHC510b - the fourth output port".

[0051] Therefore, from the perspective of the input signal T3, the radio signal radiated from the sub-array (C1 - 45) of the first column has a phase delay of 0° compared to the radio signal radiated from the sub-array (C1 + 45) of the first column, and the radio signal radiated from the sub-array (C1 - 45) of the first column has a phase delay of 0° compared to the radio signal radiated from the sub-array (C2 + 45) of the second column. As a result, a beam having a polarization of 90° (V) is formed (i.e., polarization synthesis occurs). Also, the radio signal radiated from the sub-array (C1 + 45) of the first column has a phase delay of 90° compared to the radio signal radiated from the sub-array (C2 + 45) of the second column, and the radio signal radiated from the sub-array (C1 - 45) of the first column has a phase delay of 90° compared to the radio signal radiated from the sub-array (C2 - 45) of the second column. Therefore, as shown in FIG. 5b, a beam having a polarization of 90° (V) is formed in the spatial direction inclined by approximately 30° to the left with respect to the normal of the antenna array.

[0052] The input signal T4 reaches the sub-array (C1 +45) of the first column through "the fourth input port - the first arm of the third QHC510c - the second arm of the third QHC510c - the fourth arm of the first QHC510a - (90° phase delay) - the second arm of the first QHC510a - the first output port". Also, the input signal T4 reaches the sub-array (C2 +45) of the second column through "the fourth input port - the first arm of the third QHC510c - the second arm of the third QHC510c - the fourth arm of the first QHC510a - the third arm of the first QHC510a - the third output port". Also, the input signal T4 is made to reach the sub-array (C1 -45) of the first column through "the fourth input port - the first arm of the third QHC510c - (90° phase delay) - the third arm of the third QHC510c - (90° phase delay) - the fourth arm of the second QHC510b - (90° phase delay) - the second arm of the second QHC510b - the second output port". Also, the input signal T4 is supplied to the sub-array (C2 -45) of the second column through "the fourth input port - the first arm of the third QHC510c - (90° phase delay) - the third arm of the third QHC510c - (90° phase delay) - the fourth arm of the second QHC510b - the third arm of the second QHC510b - the fourth output port".

[0053] Therefore, from the perspective of the input signal T4, the radio signal radiated from the sub-array (C1 - 45) of the first column has a 180° phase delay compared to the radio signal radiated from the sub-array (C1 + 45) of the first column, and the radio signal radiated from the sub-array (C1 - 45) of the first column has a 180° phase delay compared to the radio signal radiated from the sub-array (C2 + 45) of the second column. As a result, a beam with a 0° (H) polarization is formed (i.e., polarization synthesis occurs). Also, the radio signal radiated from the sub-array (C1 + 45) of the first column has a 90° phase delay compared to the radio signal radiated from the sub-array (C2 + 45) of the second column, and the radio signal radiated from the sub-array (C1 - 45) of the first column has a 90° phase delay compared to the radio signal radiated from the sub-array (C2 - 45) of the second column. Therefore, as shown in FIG. 5b, a beam with a 0° (H) polarization is formed in the spatial direction inclined approximately 30° to the left with respect to the normal of the antenna array.

[0054] FIG. 6a illustrates a 4T4R polarization diversity antenna system according to another embodiment of the present invention that utilizes an antenna array including heterogeneous dual-polarization antenna units.

[0055] The antenna system illustrated in FIG. 6a does not require signal processing in the digital domain or the RF domain and generates spatially multiplexed orthogonal polarization beams similar to those in FIG. 1 or FIG. 3 using heterogeneous dual-polarization antenna units. Therefore, the Tx signals T1, T2, T3, T4 shown in FIG. 6a are signals to which polarization synthesis in the digital domain is not applied. Similarly, polarization synthesis in the digital domain is not applied to the Rx signals either.

[0056] Referring to FIG. 6a, an antenna array in which heterogeneous dual-polarization antenna units are arranged in four columns is illustrated. The two left columns are composed of +45° / -45° dual-polarization antenna units, and the two right columns are composed of V / H dual-polarization antenna units.

[0057] In each column, the antenna elements 601a, 601b, 602a, and 602b are connected to the feeder lines 611a, 611b, 612a, and 612b for each polarization. For example, in each of the first and second columns, the first antenna element 601a with +45° polarization is connected to the first feeder line 611a to form the first sub-array, and the second antenna element 601b with -45° polarization is connected to the second feeder line 611b to form the second sub-array. In each of the third and fourth columns, the first antenna element 602a with 90° (V) polarization is connected to the first feeder line 612a to form the first sub-array, and the second antenna element 602b with 0° (H) polarization is connected to the second feeder line 612b to form the second sub-array. Therefore, in the dual-polarized antenna array illustrated in FIG. 6a, the antenna elements 601a, 601b, 602a, and 602b are divided into eight sub-arrays.

[0058] To form beams for each polarization using the antenna array illustrated in FIG. 6a, the sub-arrays having the same polarization are connected to each other in the RF domain. That is, a pair of sub-arrays for each polarization are coupled to each other in the RF domain so as to be connected to one RF chain 630. As a result, the antenna system is 4T4R. The coupling of the sub-arrays is achieved by configuring a simple RF combiner on the RF domain.

[0059] As described below, an antenna panel is formed such that a first region (or a first surface) of the antenna panel in which antenna units having +45° / -45° polarization are arranged and a second region (or a second surface) of the antenna panel in which antenna units having V / H polarization are arranged form a predetermined obtuse angle (90° < θ < 180°). The first region and the second region form, for example, 120°. Therefore, with the antenna panel bent in the longitudinal direction, the +45° / -45° dual-polarization antenna array and the H / L dual-polarization antenna array are arranged so as to be directed in spatially different directions. With such a configuration, a beam having +45° / -45° polarization and a beam having V / H polarization are mechanically steered in the spatial direction facing the two regions of the antenna panel. Therefore, by appropriately adjusting the angle θ formed by the two regions of the antenna panel, the antenna system of FIG. 6a can generate a spatially multiplexed orthogonal polarization beam similar to that of FIG. 1 or FIG. 3.

[0060] The antenna system of FIG. 6a requires only a simple RF component such as an RF combiner for forming a spatially multiplexed beam pattern, and does not require hardware for signal processing in the digital domain (required for the antenna system of FIG. 1), thereby also improving the heat generation problem. Further, the antenna system of FIG. 6a can maintain a more accurate interval between beams compared to the antenna system shown in FIG. 3, and can minimize the region where beams having different dual polarizations, which particularly affect the SINR performance, overlap with each other.

[0061] 6b to 6d are diagrams for explaining the structure of an antenna panel in which heterogeneous dual-polarization antenna units are arranged, which is adopted in the antenna system of FIG. 6a, and the usefulness of the structure.

[0062] FIG. 6b is a plan view of an exemplary antenna panel 600 employed in the antenna system of FIG. 6a. Referring to FIG. 6b, a +45° / −45° dual-polarization antenna unit 601 is arranged on the left half 610 of the antenna panel 600, and an H / V dual-polarization antenna unit 602 is arranged on the right half 620 of the antenna panel 600.

[0063] If the left half 610 and the right half 620 form one flat surface (see the front view of FIG. 6c(a)), by introducing a phase difference between RF signals applied to dual-polarization antenna units having the same polarization characteristics, a pair of spatially multiplexed beam patterns as illustrated in FIG. 6c(b) can be obtained. On the other hand, when the left side surface 610 of the antenna panel 600 and the right side surface 620 of the antenna panel form a predetermined obtuse angle θ (see the front view of FIG. 6d(a)), a pair of beam patterns as illustrated in FIG. 6d(b) can be obtained without phase adjustment of the RF signals applied to dual-polarization antenna units having the same polarization characteristics. In the beam pattern of FIG. 6c(b), there are significant sidelobes around the main lobe, while in the beam pattern of FIG. 6d(b), there are negligible sidelobes. That is, it can be seen that the structure of the antenna panel as shown in FIG. 6d(a) and the arrangement of heterogeneous dual-polarization antenna units are relatively useful for spatial polarization multiplexing.

[0064] Furthermore, by combining the structure of the antenna panel 600 as shown in FIG. 6d(a) with RF beamforming, the beam may be directed in a spatial direction larger than the spatial direction provided by the angle θ formed by two regions of the antenna panel. For example, in the left half 610 of the antenna panel 600 illustrated in FIG. 6d(a), by making the RF path from the first column subarray to the RF chain 630 longer than the RF path from the second column subarray to the RF chain 630, a beam having an orthogonal polarization of +45° / −45° is formed more to the left than the spatial direction facing the left half 610 of the antenna panel 600. Therefore, by combining the structure of the antenna panel 600 illustrated in FIG. 6d(a) with RF beamforming, the angle θ formed by the left half 610 and the right half 620 of the antenna panel 600 may be made larger (i.e., closer to 180°). In such a context, FIG. 6e illustrates a configuration in which subarrays of the same polarization located in different columns are connected to the RF chain 630 by RF paths of different lengths.

[0065] FIG. 7a illustrates an antenna panel 700 in which heterogeneous dual-polarization antenna units that are bent in the longitudinal direction and also bent in the width direction according to another embodiment of the present invention are arranged.

[0066] Referring to FIG. 7a, the bending in the longitudinal direction x divides the antenna panel into a left region and a right region, and the bending in the width direction y further divides the antenna panel into an upper region and a lower region. In other words, the antenna panel on which the antenna elements are arranged is divided into four regions (surfaces) facing different directions.

[0067] Note that the + / -45° antenna elements 701 and the V / H antenna elements 702 are alternately arranged in four regions (surfaces) so that antenna elements having the same dual polarization are not arranged on two adjacent surfaces in the horizontal or vertical direction of the antenna panel. For example, the V / H dual-polarization antenna unit 702 is arranged on the upper left surface of the antenna panel, the + / -45° dual-polarization antenna unit 701 is arranged on the upper right surface, the + / -45° dual-polarization antenna unit 701 is arranged on the lower left surface, and the V / H dual-polarization antenna unit 702 is arranged on the lower right surface.

[0068] Similar to the antenna panel 600 shown in FIG. 6a, for each region (surface) of the antenna panel 700 illustrated in FIG. 7a, the antenna elements in each column are connected to a feeder line for each polarization to form a subarray. Further, subarrays located in different columns having the same polarization are connected to each other in the RF domain. That is, in a given region (surface) of the antenna panel 700, a pair of subarrays located in different columns for each polarization are coupled to each other in the RF domain so as to be connected to one RF chain. Thereby, the antenna system using the antenna panel 700 illustrated in FIG. 7a supports 8T8R.

[0069] As an alternative, the + / -45° dual-polarization antenna units 701 arranged on the upper right surface and the lower left surface of the antenna panel 700 may be connected to a pair of RF chains, and the V / H dual-polarization antenna units 702 arranged on the upper left surface and the lower right surface of the antenna panel may be connected to another pair of RF chains. Thereby, the antenna system using the antenna panel 700 illustrated in FIG. 7a can also support 4T4R.

[0070] The ±45° dual-polarization antenna unit 701 arranged on the upper right forms a first beam having +45° / -45° orthogonal polarization, the V / H dual-polarization antenna unit 702 arranged on the upper left forms a second beam having V / H orthogonal polarization, the ±45° dual-polarization antenna unit 701 arranged on the lower left forms a third beam having +45° / -45° orthogonal polarization, and the V / H dual-polarization antenna unit arranged on the lower right forms a fourth beam having V / H orthogonal polarization. The respective spatial directions towards which the first beam to the fourth beam are directed coincide with the spatial directions facing the corresponding surfaces of the antenna panel. Therefore, the first beam to the fourth beam are formed in different spatial directions from each other.

[0071] On the other hand, as illustrated in FIG. 7b, the third beam and the fourth beam formed by the dual-polarization antenna units arranged in the lower left region and the lower right region can cover the shadow areas not covered by the first beam and the second beam formed by the antenna elements arranged in the upper right region and the upper left region. Therefore, a smaller number of dual-polarization antenna units are arranged in the lower left region and the lower right region (which provide the main coverage of the antenna system) than in the upper right region and the upper left region.

[0072] The above description merely exemplarily explains the technical idea of the embodiments of the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various modifications and deformations without departing from the essential characteristics of the present invention. Therefore, this embodiment is not intended to limit the technical idea of the present invention but to explain it, and the scope of the technical idea of the present invention is not limited by such embodiments. The protection scope of the present invention should be interpreted by the scope of the claims, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

[0073] [CROSS-REFERENCE TO RELATED APPLICATION] This patent application claims priority to Patent Application No. 10-2021-0127532, filed in Korea on September 27, 2021, and Patent Application No. 10-2022-0110149, filed in Korea on September 1, 2022, which are incorporated herein by reference in their entirety.

Claims

1. An antenna array including a first row of dual-polarization antenna units and a second row of dual-polarization antenna units, and an RF matrix, each of the dual-polarization antenna units including a first antenna element and a second antenna element that are perpendicular to each other, and in each row, the first antenna elements being conductively connected to form a first sub-array and the second antenna elements being conductively connected to form a second sub-array, the RF matrix branching each of the RF input signals into a plurality of branch signals, selectively adjusting the phases of the plurality of branch signals, and generating RF output signals provided to the first sub-array of the first row, the second sub-array of the first row, the first sub-array of the second row, and the second sub-array of the second row, a polarization diversity antenna system in which, when the RF output signals are radiated by the dual-polarization antenna units, a first beam having a + / −45° polarization and a second beam having a 0° / 90° polarization are formed, and the first beam and the second beam are formed in spatially different directions from each other.

2. The polarization diversity antenna system according to claim 1, wherein the RF matrix is implemented by a quadrature hybrid coupler (QHC) formed on a PCB.

3. The RF matrix is a first QHC, a second QHC, and a third QHC, a first input port connected to a first arm of the first QHC, a second input port connected to a first arm of the second QHC, a third input port connected to a fourth arm of the third QHC, and a fourth input port connected to a first arm of the third QHC, a first output port connected to a second arm of the first QHC, a second output port connected to a third arm of the first QHC, a third output port connected to a second arm of the second QHC, and a fourth output port connected to a third arm of the second QHC, and includes the polarization diversity antenna system according to claim 2, wherein a second arm of the third QHC is connected to a fourth arm of the first QHC, and a third arm of the third QHC is connected to a fourth arm of the second QHC.

4. The first input port, the second input port, the third input port, and the fourth input port are connected to the first sub-array of the first column, the first sub-array of the second column, the second sub-array of the first column, and the second sub-array of the second column, respectively, of the polarization diversity antenna system according to claim 3.

5. The first input port, the second input port, the third input port, and the fourth input port are connected to an RF chain that supplies the RF input signal, respectively, of the polarization diversity antenna system according to claim 3.

6. The RF matrix selectively adjusts the phases of the plurality of branch signals based on a phase difference for forming the first beam and the second beam and a phase difference for determining the polarization of the first beam and the second beam, of the polarization diversity antenna system according to claim 1.

7. Among the RF input signals, the phases adjusted by the RF matrix for a pair of RF input signals propagated by the first beam are defined to achieve a desired spatial direction in which the first beam is formed, of the polarization diversity antenna system according to claim 6.

8. Among the RF input signals, the phases adjusted by the RF matrix for a pair of RF input signals propagated by the second beam are defined to achieve a desired spatial direction and polarization synthesis in which the second beam is formed, of the polarization diversity antenna system according to claim 6.

9. The dual-polarization antenna unit has + / −45° polarization characteristics, of the polarization diversity antenna system according to claim 1.

10. The 0° / 90° polarization of the second beam is obtained by polarization synthesis, of the polarization diversity antenna system according to claim 9.

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