A broadband high-gain beam-scannable millimeter-wave dielectric resonator antenna

Abstract

The application provides a millimeter wave dielectric resonator antenna with wide frequency band and high gain and wide beam scanning, which comprises a four-layer structure, wherein the top layer is a dielectric layer with high dielectric constant, the second layer is a dielectric substrate with low dielectric constant, the third layer is a dielectric substrate with low dielectric constant, and the bottom layer is a dielectric substrate with low dielectric constant. Four rectangular dielectric blocks and metal grooves are integrally designed to facilitate subsequent processing. The bandwidth of the antenna is expanded to 52% in the working frequency band of 23.81-40.52 GHz by exciting and combining the dielectric resonator base film and the high-order mode. The antenna has stable high-gain radiation characteristics in the working frequency band due to the introduction of metal grooves around the dielectric blocks, and the highest gain can reach about 15.73 dBi, and the average gain can reach about 13.2 dBi. The introduction of metal walls between the antenna units reduces the coupling between the units and improves the isolation between the units to realize the wide beam scanning characteristics of the antenna. The main beam of the antenna can be scanned to ±40° and ±30° at 25 GHz and 40 GHz, respectively.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of wireless communication and antenna technology, and relates to a medium resonator antenna with a wide frequency band and a high-gain beam that can be scanned. BACKGROUND

[0002] With the rapid increase of various application and communication needs of users, the spectrum resources of the Sub-6G frequency band are difficult to meet the use needs of people, and are not easy to support wireless communication with higher transmission rates. The millimeter wave can provide a wider frequency range and higher transmission rate for mobile terminal devices, and has obvious advantages in spectrum resources. The millimeter wave antenna applied to the mobile terminal device needs to have multiple characteristics at the same time: using one set of antenna to cover as many frequency bands in FR2 as possible, thereby reducing the number of antennas used and reducing the cost; maintaining stable high-gain characteristics in the working frequency band to improve the signal-to-noise ratio of terminal reception; having a wide beam scanning capability to achieve wide-range spatial radiation beam coverage and ensure the connection between the terminal and the base station. However, there are many drawbacks in the existing terminal millimeter wave antenna design, such as large size of the antenna, which is difficult to apply to small terminal devices; narrow bandwidth of the antenna, which limits the application range; low gain of the antenna, which is difficult to ensure the signal-to-noise ratio of terminal reception; limited beam coverage range of the antenna, which is difficult to achieve wide beam scanning characteristics. Therefore, how to design a millimeter wave terminal antenna with wide frequency band, high gain and wide beam scanning characteristics in the millimeter wave frequency band has important research significance.

[0003] Traditional metal antennas usually have high loss in the millimeter wave frequency band, thereby affecting the antenna efficiency, while the medium resonator antenna has been widely concerned in the millimeter wave frequency band due to its advantages of flexible design, low loss and high radiation efficiency. In order to realize the wide frequency characteristics, the existing millimeter wave medium resonator antenna expands the bandwidth by adopting a multi-layer structure, changing the shape of the medium resonator, mixing other antennas and the like, but these designs usually have insufficient bandwidth to completely cover the 5G millimeter wave communication frequency band, and the antenna size is usually large or the antenna gain is low. In order to improve the gain of the antenna, frequency selective surface (FSS), lens technology and antenna array are applied to the medium resonator antenna, but these researches usually have limited bandwidth or do not have wide beam scanning capability. Therefore, the research on a terminal millimeter wave medium resonator antenna with wide frequency band, high gain and wide beam scanning characteristics will have strong market competitiveness. SUMMARY

[0004] The present application aims at the shortcomings and deficiencies in the prior art, and proposes a millimeter wave dielectric resonator antenna array with wide frequency band, high gain and beam scanning. By forming a 1x4 dielectric resonator antenna array with four antenna units, the spacing between the antenna units is about half a wavelength, and the introduction of metal grooves around the four rectangular dielectric blocks enables the antenna to maintain stable high gain characteristics in the entire operating frequency band. The metal walls between the dielectric resonator antenna units reduce the coupling between the units and improve the isolation between the units to achieve the wide beam scanning characteristics of the antenna. The four rectangular dielectric blocks and the metal grooves are designed integrally to facilitate subsequent manufacturing and assembly. The impedance bandwidth of the dielectric resonator antenna can cover 23.81-40.52GHz (~52%), and the antenna maintains stable high gain radiation characteristics in the operating frequency band, with an average gain of ~13.2dBi. The antenna structure is compact and meets the requirements of wide beam scanning, and the main beam can be scanned to ±40° and ±30° at 25GHz and 40GHz, respectively. The millimeter wave dielectric resonator antenna with wide frequency band, high gain and beam scanning characteristics has broad market prospects and application range.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0006] A millimeter wave dielectric resonator antenna with wide frequency band, high gain and beam scanning is formed by exciting and combining multiple resonant modes of the dielectric resonator antenna to achieve the wide frequency band characteristics of the antenna, and a 1x4 antenna array is formed by dielectric resonator antenna units and metal grooves 14, 15 are introduced around the first layer dielectric substrate to maintain stable high gain characteristics.

[0007] The dielectric resonator antenna unit adopts a four-layer structure, and the wide frequency band characteristics of the antenna are achieved by exciting and combining multiple resonant modes of the dielectric resonator antenna. From top to bottom, they are a first layer dielectric substrate 1, a second layer dielectric substrate 2, a third layer dielectric substrate 3, and a fourth layer dielectric substrate 4. It is a millimeter wave dielectric resonator antenna with wide frequency band, high gain and wide beam scanning characteristics.

[0008] The first layer dielectric substrate 1 has high dielectric constant, and four dielectric blocks 13 are integrated on the first layer dielectric substrate 1 by integrated design. The dielectric blocks 13 are provided with longitudinal metal grooves 14 and transverse metal grooves 15 around them, and the longitudinal metal grooves between adjacent dielectric blocks 13 are metal walls 16, which together constitute the top layer antenna radiation structure. The metal grooves 14 and 15 around the dielectric blocks 13 serve to improve the gain of the antenna and ensure the stability of the radiation, and the transverse metal grooves leave the position for connecting the rectangular dielectric blocks to facilitate subsequent processing and manufacturing. The metal walls 16 between adjacent dielectric blocks 13 serve to reduce the coupling between the antenna units and improve the isolation of the antenna.

[0009] The second layer dielectric substrate 2 has low dielectric constant.

[0010] The third layer dielectric substrate 3 and the fourth layer dielectric substrate 4 are both low dielectric constant, and are bonded together by the adhesive layer 5 to form a substrate integrated coaxial line (SICL) feeding network structure, and a plurality of metal holes 10 are arranged at corresponding positions. The third layer dielectric substrate 3 and the fourth layer dielectric substrate 4 are provided with an SICL inner conductor 9 fed by a gap coupling structure 8. The metal holes 10 are uniformly distributed on both sides of the SICL inner conductor 9. The upper surface of the third layer dielectric substrate 3 and the lower surface of the fourth layer dielectric substrate 4 are respectively a first layer metal ground plate 6 and a second layer metal ground plate 7. The first layer metal ground plate 6 is etched with four same transverse gap coupling structures 8 in the middle part in a transverse and side-by-side and equal-interval manner, and the side-by-side arrangement manner is consistent with the side-by-side arrangement manner of the four dielectric blocks 13 on the top layer and the center positions correspond. The SICL inner conductor 9 between the dielectric substrates 3 and 4 is used to guide the energy transmission of electromagnetic signals. The SICL inner conductor 9 is coupled to the top layer antenna radiation structure through the four gap coupling structures 8 on the top. The metal holes 10 uniformly distributed on both sides of the SICL inner conductor 9 and the metal ground plates 6 and 7 together form the outer conductor of the SICL structure, which plays a shielding role to reduce the radiation loss. A grounded co-planar waveguide (GCPW) feeding structure is introduced at the bottom of the feeding network. The upper and lower planes of the GCPW are consistent with the upper and lower surfaces of the outer conductor of the SICL, and the center conductor 11 of the GCPW is located on the same layer as the metal ground plate 6. A metal blind hole 12 is introduced in the transition part of the top of the GCPW center conductor 11 and the bottom of the SICL inner conductor 9 to connect the two, so that the electromagnetic signal can be transferred from the GCPW to the SICL feeding network.

[0011] The integrated design of the four antenna units can solve the manufacturing and assembly problems in actual processing. The use of substrate integrated coaxial line (SICL) as the feeding network to excite the antenna can obtain smaller radiation loss.

[0012] Further, the dielectric constant of the first layer dielectric substrate 1 is not less than 10.

[0013] Further, the dielectric constant of the second layer dielectric substrate 2 is not greater than 10.

[0014] Further, the third layer dielectric substrate 3 and the fourth layer dielectric substrate 4 have the same dielectric constant, and the dielectric constant selected is not greater than 10.

[0015] Further, the dielectric constant of the adhesive layer 5 is not greater than 10.

[0016] Further, the four-layer medium substrate is provided with a plurality of through holes for placing plastic screws to fix the assembled antenna.

[0017] Further, the distance between the centers of the adjacent two metal holes 10 in the plurality of metal holes 10 on both sides of the SICL inner conductor 9 is 0.6 mm.

[0018] Further, the spacing between the antenna units is 0.5 lambda 0, and the compact antenna structure makes the antenna have a wide beam scanning characteristic. Wherein lambda 0 represents the wavelength corresponding to the center frequency of the working bandwidth.

[0019] Further, metal walls are introduced between adjacent antenna units, but are not limited to the form of metal walls, which reduces the coupling between units and improves the isolation between antenna units to realize the wide beam scanning capability of the antenna.

[0020] The innovation points of the present application are analyzed as follows:

[0021] (1) The present application provides a millimeter wave dielectric resonator antenna scheme with wide frequency band, high gain and wide beam scanning characteristics.(2) The antenna bandwidth is expanded to realize super wide band design by exciting and combining the base mode and high order mode of the dielectric resonator antenna.(3) The metal grooves are introduced around the dielectric block to maintain stable high gain radiation characteristics within the impedance bandwidth.(4) The metal walls are introduced between the antenna units to reduce the coupling between the dielectric resonator antenna units and improve the isolation of the antenna to realize the wide beam scanning characteristics.(5) The dielectric block and the metal grooves are integrated to facilitate the subsequent processing and assembly of the antenna.

[0022] The protection points of the present application are as follows:

[0023] (1) Multiple rectangular dielectric blocks form an array structure, but are not limited to rectangular. Broadband design is achieved by exciting and merging the fundamental mode and higher-order modes of the antenna, and the sizes of the multiple rectangular dielectric blocks are not limited to the same size. Each dielectric block can have different sizes. (2) Metal grooves are introduced around the four dielectric blocks, but are not limited to the form of metal grooves, so that the dielectric resonator antenna has stable high gain characteristics. (3) Metal walls are introduced between the dielectric resonator antenna units, but are not limited to the form of metal walls, to reduce the coupling between the units and improve the isolation between the antenna units to achieve the antenna wide beam scanning capability. (4) The four dielectric blocks and the metal grooves are integrated into a design, but are not limited to this integrated form, which facilitates the subsequent processing and assembly of the antenna. (5) The invented antenna is not limited to the given four parallel placements to form an antenna array structure for high gain radiation. On this basis, radiation units can also be added to be used in a larger-scale antenna array design to achieve a broadband high gain antenna with stronger directional radiation or a beam scanning phased array antenna. (6) The antenna design takes the millimeter wave band as an example, but is not limited to this band. The design technology can be extended to any band.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) This invention solves the problem that previously, a single antenna could not achieve the excellent performance characteristics of wide bandwidth, high gain, and wide beam scanning. The four radiating elements of the antenna are integrated into a single design, solving the problem that each small antenna element needs to be manufactured separately and is difficult to accurately position and assemble with the printed circuit board.

[0026] (2) The present invention expands the bandwidth of the antenna by exciting and merging the fundamental mode and higher-order modes of the dielectric resonator, achieving an impedance bandwidth of 52% within the operating frequency band of 23.81-40.52 GHz, and can simultaneously cover the four frequency bands of FR2, namely N257 (26.5-29.5 GHZ), N258 (24.25-27.5 GHZ), N260 (37.0-40.0 GHZ) and N261 (27.5-28.35 GHZ).

[0027] (3) The present invention introduces metal grooves around the dielectric block, enabling the antenna to have stable high-gain radiation characteristics within the operating frequency band, with a maximum gain of ~15.73dBi and an average gain of ~13.2dBi. The introduction of metal walls between antenna elements reduces coupling between elements, improves isolation between antenna elements, and achieves wide-beam scanning characteristics. At 25GHz and 40GHz, the antenna main beam can scan to ±40° and ±30°, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1is the cross-sectional view of the overall structure of the millimeter wave dielectric resonator antenna array with wideband high-gain beam scanning according to the present application;

[0029] Figure 2(a) is a cross-sectional view of the first layer of high dielectric constant medium layer according to the present application;

[0030] Figure 2(b) is a cross-sectional view of the second layer of medium substrate according to the present application;

[0031] Figure 2(c) is a cross-sectional view of the first layer of metal floor layer according to the present application;

[0032] Figure 2(d) is a cross-sectional view of the SICL and GCPW-SICL adapter structure part according to the present application;

[0033] Figure 3 is the simulated reflection coefficient curve according to the present application;

[0034] Figure 4 is the simulated antenna gain versus frequency graph according to the present application;

[0035] In the figure: 1 first layer of medium substrate; 2 second layer of medium substrate; 3 third layer of medium substrate; 4 fourth layer of medium substrate; 5 adhesive layer; 6 first layer of metal floor layer; 7 second layer of metal floor layer; 8 gap coupling structure; 9 inner conductor of SICL; 10 metal hole; 11 center conductor of GCPW; 12 adapter blind hole of GCPW and SICL; 13 medium block; 14 longitudinal metal groove; 15 transverse metal groove; 16 metal wall between medium blocks; 17 spacing between medium blocks and coupling gaps. DETAILED DESCRIPTION

[0036] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings and technical solutions.

[0037] Referring to Figure 1 The overall structure of the millimeter wave dielectric resonator antenna array with wideband high-gain beam scanning is shown in the perspective view, which is a four-layer structure, including a first layer of high dielectric constant medium substrate 1, a second layer of low dielectric constant medium substrate 2, a third layer of low dielectric constant medium substrate 3, and a fourth layer of low dielectric constant medium substrate 4. The medium substrate 3 and the medium substrate 4 are bonded together by an adhesive layer 5.

[0038] Referring to Figure 2(a), the top layer is a high dielectric constant medium substrate 1 made of Rogers Ro3010 material (ε r= 11.2, tan δ = 0.0022), with a length of 24.8 mm, a width of 14.7 mm, and a thickness of 0.635 mm. The length of the dielectric block 13 is 5 mm, the width is 2.9 mm, and the interval 17 between each dielectric block is 5.2 mm. In order to achieve stable high gain characteristics, a longitudinal metal groove 14 and a transverse metal groove 15 are arranged on the periphery of the dielectric block 13. The length of the longitudinal metal groove 14 is 7.9 mm, the width is 0.7 mm, and the thickness is 0.635 mm. The length of the transverse metal groove 15 is 17.6 mm, the width is 0.7 mm, and the thickness is 0.635 mm. The transverse metal groove leaves a position for connecting the rectangular dielectric blocks for subsequent processing and manufacturing. A longitudinal metal wall 16 is introduced between each adjacent two dielectric blocks 13 to reduce the coupling between the antenna units and improve the antenna isolation. The length of the metal wall 16 is 9.2 mm, the width is 0.5 mm, and the thickness is 0.635 mm.

[0039] Referring to FIG. 2(b), the second layer of low dielectric constant dielectric substrate 2; the dielectric substrate 2 adopts Rogers 5880 material (ε r = 2.2, tan δ = 0.0009), with a length of 24.8 mm, a width of 14.7 mm, and a thickness of 0.254 mm.

[0040] Referring to FIG. 2(c), the first layer of metal ground layer 6, four same transverse slot coupling structures 8 are etched side by side in the middle, which are placed side by side in the same way as the four dielectric blocks on the top layer and correspond to the center position. The length of the slot is 2.5 mm, and the width is 0.5 mm. The length of the metal ground layer 6 is 24.8 mm, and the width is 20.6 mm.

[0041] Referring to FIG. 2(d), the SICL feeding network structure and the GCPW-SICL adapter part. The third layer of dielectric substrate 3 and the fourth layer of dielectric substrate 4 both adopt Rogers 5080 material (ε r = 2.2, tan δ = 0.0009). The length of the dielectric substrate 3 and 4 is 24.8 mm, the width is 20.6 mm, and the thickness is 0.254 mm. The adhesive layer 5 with a thickness of 0.1 mm, Rogers 4450 material (ε rThe medium substrates 3 and 4 are bonded together, and a plurality of metal holes 10 are arranged at corresponding positions, and an SICL inner conductor 9 fed by a slot coupling structure 8 is arranged between the third layer medium substrate 3 and the fourth layer medium substrate 4, wherein the metal holes 10 are uniformly distributed on both sides of the SICL inner conductor 9. The diameter of the metal hole 10 is 0.4 mm, the height is 0.608 mm, the distance between the centers of two adjacent metal holes is 0.6 mm, and the distance between the centers of the metal holes on both sides of the SICL inner conductor is 2.75 mm. The length of the second layer metal floor layer 7 is 24.8 mm, and the width is 20.6 mm. The number of the antenna units described in the application is four, and the SICL inner conductor 9 provides equal amplitude and in-phase feeding for the four radiation units, and is assembled and fixed with the radiation structure by a plastic screw to form a four-unit array antenna.

[0042] Since many microwave devices are in the form of surface mount technology (SMT), it is difficult to connect the individual SICL to various experimental equipment for testing in actual application. Therefore, a transition structure of a grounded co-planar waveguide (GCPW) to SICL is designed at the bottom of the feeding network, so that it can be compatible with the experimental environment. The upper and lower planes of the GCPW are consistent with the upper and lower surfaces of the outer conductor of the SICL, wherein the GCPW center conductor 11 is located at the same layer as the metal floor 6, and the length is 3 mm and the width is 0.95 mm, and the width of the inner conductor of the SICL inner conductor 9 connected with the GCPW is 0.4 mm. Since the GCPW center conductor 11 and the SICL inner conductor 9 are in different planes and cannot be directly connected, a metal blind hole 12 penetrating through the third layer medium substrate 3 is used to connect the top of the GCPW center conductor 11 and the bottom of the SICL inner conductor 9 to conduct electromagnetic signals, wherein the diameter of the metal blind hole is 0.34 mm and the height is 0.254 mm. In order to reduce the loss as much as possible and improve the energy transmission efficiency, the impedance of the metal blind hole 12, the GCPW center conductor 11 and the SICL inner conductor 9 is matched when designing the transition part.

[0043] Reference Figure 3The simulation reflection coefficient diagram of the wideband high-gain beam scanning millimeter wave dielectric resonator antenna array provided by the present application can be seen from the figure that the antenna array can cover the frequency range of 23.81-40.52GHz, the relative bandwidth is 52%, and the full coverage of N257 (26.5-29.5GHz), N258 (24.25-27.5GHz), N260 (37.0-40.0GHz) and N261 (27.5-28.35GHz) of the FR2 frequency band can be completely realized.

[0044] Reference Figure 4 For the antenna gain versus frequency graph, the antenna achieves a maximum gain of 15.73dBi at 36.5GHz, and the average gain is 13.2dBi within the entire impedance bandwidth, having a stable high-gain characteristic.

[0045] The above-described embodiments only express the implementation of the present application, but cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A millimeter-wave dielectric resonator antenna with a wide-band, high-gain beam scannable, characterized in that: The broadband characteristic of the antenna is achieved by exciting and combining multiple resonance modes of the dielectric resonator antenna. A 1×4 millimeter wave dielectric resonator antenna array is formed by dielectric resonator antenna units, and metal grooves (14, 15) are introduced on the periphery of the first dielectric substrate to maintain stable high gain characteristics. The dielectric resonator antenna unit adopts a four-layer structure, which comprises, from top to bottom, a first dielectric substrate (1), a second dielectric substrate (2), a third dielectric substrate (3), and a fourth dielectric substrate (4). The specific structure of the dielectric resonator antenna unit is as follows: The first dielectric substrate (1) has a high dielectric constant, and four dielectric blocks (13) are integrated on the first dielectric substrate (1) using an integrated design; longitudinal metal grooves (14) and transverse metal grooves (15) are provided on the periphery of the dielectric blocks (13); the longitudinal metal grooves provided between adjacent dielectric blocks (13) are metal walls (16), which together constitute a top-layer antenna radiation structure; The second dielectric substrate (2) has a low dielectric constant; The third dielectric substrate (3) and the fourth dielectric substrate (4) are both of low dielectric constant, and the two are bonded together by an adhesive layer (5) to form a substrate integrated coaxial line SICL feeding network structure, and a plurality of metal holes (10) are provided at corresponding positions, and a SICL inner conductor (9) fed through a slot coupling structure (8) is provided between the third dielectric substrate (3) and the fourth dielectric substrate (4), wherein the metal holes (10) are evenly distributed on both sides of the SICL inner conductor (9); the upper surface of the third dielectric substrate (3) and the lower surface of the fourth dielectric substrate (4) are respectively a first metal floor (6) and a second metal floor (7); the first metal floor ( 6) Four identical transverse slot coupling structures (8) are etched in parallel and at equal intervals in the middle, and their side-by-side arrangement is consistent with the side-by-side arrangement of the four dielectric blocks (13) on the top layer, and their center positions correspond to each other; the SICL inner conductor (9) located between the dielectric substrates (3) and 4 is used to guide the energy transmission of the electromagnetic signal, and the top of the SICL inner conductor (9) couples the signal to the top antenna radiation structure through the four slot coupling structures (8); the metal holes (10) on both sides of the SICL inner conductor (9) and the first layer of metal floor (6) and the second layer of metal floor (7) together form the outer conductor of the SICL structure, which plays a shielding role and thus reduces radiation loss; A grounded coplanar waveguide (GCPW) feeding structure is introduced at the bottom of the feeding network structure. The upper and lower planes of the GCPW are kept in the same height as the upper and lower surfaces of the outer conductor of the SICL. The GCPW center conductor (11) and the first layer of metal floor (6) are located on the same layer. A metal blind hole (12) is introduced into the transition part between the top of the GCPW center conductor (11) and the bottom of the SICL inner conductor (9) to connect the two so that the electromagnetic signal can be transferred from the GCPW to the SICL feeding network.

2. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: The dielectric constant of the first dielectric substrate (1) is not less than 10.

3. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: The dielectric constant of the second dielectric substrate (2) is not greater than 10.

4. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: The third dielectric substrate (3) and the fourth dielectric substrate (4) have the same dielectric constant, and the selected dielectric constant is not greater than 10.

5. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: The dielectric constant of the adhesive layer (5) is not greater than 10.

6. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: The four-layer dielectric substrate is provided with a plurality of through holes for placing plastic screws to fix and assemble the antenna.

7. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: Among the multiple metal holes (10) on both sides of the SICL inner conductor (9), the distance between the centers of two adjacent metal holes (10) is 0.6 mm.

8. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: The spacing between the antenna units is 0.5λ0, and the compact antenna structure enables the antenna to have a wide beam scanning characteristic; wherein λ0 represents the wavelength corresponding to the center frequency of the working bandwidth.

9. The wide-band, high-gain, beam-scannable millimeter-wave dielectric resonator antenna according to claim 1, characterized in that: Metal walls are introduced between adjacent antenna units to reduce coupling between units, improve isolation between antenna units and achieve wide-beam scanning capability of the antenna.

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