Broadband circularly polarized phased-array antenna based on liquid crystal

Abstract

The invention discloses a liquid crystal-based Ka-band broadband circularly polarized phased-array antenna, and belongs to the technical field of microwave antennas. The antenna comprises a radiation structure and a feed structure. The radiation structure comprises a radiation unit, a liquid crystal layer, a grounding plate, a control circuit, a bias network and a radio frequency direct current isolation structure. The control circuit is realized by an FPGA (Field Programmable Gate Array) and is connected with the radiation unit through a bias network; the radio frequency direct current isolation structure is used for isolating direct current and radio frequency signals; the feed structure adopts a waveguide feed mode and forms a wave beam in a specified direction through phase compensation of the array units; the bandwidth of the antenna array is increased by using a sequential rotation feed mode, the offset line arrangement of the array is designed, and the radio frequency direct current isolation design is added, so that the technical problem that the circularly polarized bandwidth of the liquid crystal phased-array antenna is relatively narrow is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave antennas, and in particular relates to a broadband circularly polarized phased array antenna based on liquid crystal. Background Art

[0002] With the rapid development of communication technology, fifth-generation mobile communication technology (5G) has gradually matured and the industry continues to expand. However, issues such as insufficient coverage breadth and depth still need to be addressed. These shortcomings of 5G technology have driven the development of 6G technology, which will support lower transmission latency, faster transmission rates, wider coverage, and more efficient data transmission and processing. Satellite internet, as one of the key technologies of 6G, has seen rapid development in recent years. The development of satellite internet technology has opened up new possibilities for the expansion of global communication networks and the popularization of internet access. By deploying satellites in multiple orbits and utilizing communication capabilities in different frequency bands, satellite internet can provide efficient internet access services to remote areas, while also supporting mobile and emergency communication needs, showing broad application prospects. Low-orbit satellite internet, with its advantages of low transmission latency, low link loss, and flexible launch, is the primary implementation method for satellite internet.

[0003] Because low-orbit satellites move rapidly relative to ground terminals, mechanically scanned antennas can only achieve single-beam movement and cannot change beam shape or implement multiple mobile beam modes. The use of mechanically movable devices often leads to new problems such as reduced reliability and increased weight. Therefore, maintaining a continuous connection with traditional mechanical antennas, mainly parabolic antennas, is very difficult. Phased array antennas achieve beam scanning by controlling the feed phase of each antenna element. Therefore, phased array antennas can quickly align extremely narrow satellite signal beams, solving the problem of real-time satellite-to-ground tracking, and are essential equipment for the large-scale application of satellite internet.

[0004] Traditional phased array antennas primarily use active devices to control the phase of antenna elements, thereby achieving beam scanning. However, active devices are relatively expensive, increasing the cost of the antenna. Furthermore, active devices generate significant heat and consume significant power during operation. Consequently, phased array antennas based on functional materials have recently gained attention. Liquid crystal, as an electrically tunable material, exhibits a dielectric constant that changes with bias voltage. Furthermore, its losses do not significantly change with increasing frequency. Liquid crystal-based phased array antennas offer advantages such as simple processing, a low profile, a simple structure, low cost, low power consumption, light weight, and ease of integration, making them suitable for Ka-band low-orbit satellite internet terminals.

[0005] Circularly polarized antennas can effectively resist signal attenuation and interference caused by different polarization modes. In satellite communications, the polarization direction of the signal may change due to the relative motion between the satellite and the ground station. Circularly polarized antennas can ensure signal stability in such situations, improving communication reliability.

[0006] At present, there are still some defects in liquid crystal-based phased array antennas: (1) Currently, liquid crystal-based phased array antennas are mainly linearly polarized, and there is little research on circularly polarized liquid crystal phased array antennas; (2) Currently, the bandwidth of liquid crystal-based circularly polarized antennas is relatively narrow, while circularly polarized antennas have strong anti-interference performance and play an important role in satellite Internet, so there is an urgent need to expand the bandwidth of circularly polarized liquid crystal phased array antennas. Summary of the Invention

[0007] The purpose of the present invention is to overcome the technical problems in the above-mentioned prior art of the limited research on circular polarization of liquid crystal phased array antennas and the narrow bandwidth, and to provide a broadband circularly polarized phased array antenna based on liquid crystal, which adopts liquid crystal phased array units, utilizes phase compensation, and adopts waveguide feeding to form a beam in a specified direction.

[0008] The technical problem proposed by the present invention is solved as follows:

[0009] A liquid crystal-based broadband circularly polarized phased array antenna, comprising a radiation structure and a feed structure;

[0010] The radiation structure includes a first dielectric substrate 1, a ground plate 2, a sealing frame 3, a liquid crystal layer 4, a phase shifter 5, a second dielectric substrate 6, a third dielectric substrate 7, a first radiation unit 8, a second radiation unit 9, a control circuit, a bias network and an RF DC isolation structure; the first dielectric substrate 1 and the second dielectric substrate 6 are parallel to each other and there is a gap between them; the first radiation unit 8 is located on the upper surface of the first dielectric substrate 1, and includes an N×N two-dimensional periodic array of metal patches 801, where N is a positive integer ≥2, and each metal patch array 801 is composed of a 3×3 two-dimensional periodic array of first metal patches. The first radiating element 8 is composed of a third dielectric substrate 7 located on the upper surface of the first radiating element 8; the second radiating element 9 is located on the upper surface of the third dielectric substrate 7 and includes a second metal patch 901 arranged in an N×N two-dimensional periodic pattern; the phase shifter 5 is located on the upper surface of the second dielectric substrate 6 and includes a metal spiral 501 arranged in an N×N two-dimensional periodic pattern; the ground plate 2 is a metal plate that fully covers the lower surface of the first dielectric substrate 1 and is etched with a gap; the sealing frame 3 surrounds the edges of the upper surface of the second dielectric substrate 6 and is connected to the first dielectric substrate 1 to form a sealed liquid crystal cell; the liquid crystal cell is filled with a liquid crystal layer 4;

[0011] The control circuit is implemented by FPGA, and the bias network is an N×N DC bias line. The control circuit is connected to the N×N metal spiral 501 through the N×N DC bias line to control the bias voltage of the metal spiral 501. The RF DC isolation structure is an N×N structure with a length of λ g / 4 open transmission line 202, λ g One end of the open transmission line 202 is connected to the DC bias line and the metal spiral line 501 is connected to the point λ g / 4, the other end is open;

[0012] The feeding structure is located below the radiating structure and adopts a metal waveguide 10 , with the waveguide opening being located directly below the second dielectric substrate 6 .

[0013] Furthermore, the metal patch array 801 is a 3×3 array composed of diagonally cut first square metal patches. The sides of the first square metal patches are parallel to the sides of the first dielectric substrate 1 and are equidistantly distributed in each direction. The center distance between adjacent metal patch arrays 801 is 0.6λ, where λ is the wavelength corresponding to the center frequency of the antenna operating frequency band, and the cut angle size is 0.8mm. Within the metal patch array 801, the spacing between adjacent first metal patches is 0.3mm.

[0014] Furthermore, the second metal patch 901 is a second square metal patch with diagonally cut corners, the sides of the second square metal patch are parallel to the sides of the first square metal patch, and the cutting angle is in the same direction as the cutting angle of the first metal patch; the second radiation units 901 are equidistantly distributed in each direction, and the center distance between adjacent second radiation units 901 is 0.6λ, λ is the wavelength corresponding to the center frequency of the antenna working frequency band, and the cutting angle size is 0.25mm.

[0015] Furthermore, H-shaped slots arranged in an N×N two-dimensional periodic pattern are etched on the ground plate 2 , and the period of the H-shaped slots is the same as that of the metal patch array 801 and the second metal patch 901 .

[0016] Furthermore, the first dielectric substrate 1 and the second dielectric substrate 6 are glass substrates, and the third dielectric substrate 7 is a printed circuit board substrate.

[0017] Furthermore, the relative dielectric constant of the first dielectric substrate 1 and the second dielectric substrate 6 is 5.14; the area of ​​the first dielectric substrate 1 is 62 mm×65.6 mm, and the thickness is 0.7 mm; the area of ​​the second dielectric substrate 6 is 62 mm×72 mm, and the thickness is 0.7 mm.

[0018] Furthermore, the third dielectric substrate 7 adopts Taconic's TLY-3 substrate, with a relative dielectric constant of 2.33, an area of ​​the third dielectric substrate 7 of 52 mm×52 mm, and a thickness of 0.35 mm.

[0019] Furthermore, the thickness of the liquid crystal layer 4 is 0.05 mm, and the relative dielectric constant is adjusted in the range of 2.5 to 3.5.

[0020] Furthermore, N=8.

[0021] Furthermore, the feeding structure adopts a metal waveguide 10, and the thickness of the waveguide metal wall is 1 mm.

[0022] Furthermore, the liquid crystal layer 4 is oriented so that when no bias voltage is applied, the liquid crystal molecules point in the same direction and the liquid crystal material has a minimum dielectric constant; when a bias voltage is applied to the metal spiral 501, the liquid crystal molecules are deflected, the dielectric constant of the liquid crystal material changes, and the phase shift of the corresponding metal spiral 501 changes, thereby achieving the adjustment of the antenna radiation characteristics.

[0023] Furthermore, the control circuit calculates the required offset phase and corresponding bias voltage value for each metal spiral 501 according to the sequential rotation feed phase compensation principle and the set antenna beam azimuth angle, and applies a bias voltage to each metal spiral 501 through the bias network.

[0024] The beneficial effects of the present invention are:

[0025] The antenna described in the present invention adopts the form of liquid crystal material combined with a phased array antenna. By applying a bias voltage to change the dielectric constant of the liquid crystal material, the phase shift amount of the spiral phase shifter is adjusted. Compared with the beam scanning antenna of the prior art loaded with RF switches such as diodes, this adjustment method makes the power consumption of each unit lower, the phase accuracy higher, the scanning angle switching more flexible, and has the advantage of being able to achieve large-angle scanning in the pitch plane at any azimuth angle.

[0026] The antenna of the present invention adopts two layers of radiating units. Compared with a single layer of radiating units, the two layers of radiating units of the present invention realize circular polarization, have a wider axial ratio bandwidth and impedance bandwidth, and the gain of the antenna is also higher.

[0027] The antenna described in this invention utilizes sequential rotational feeding technology to form an array of antenna elements, significantly improving antenna gain while also enabling a wider array bandwidth. Dynamic scanning of the antenna beam is achieved through independent control of the phase shifters in each antenna element. Furthermore, a radio frequency DC isolation structure is designed to prevent the impact of DC bias circuits on antenna radiation performance. Compared to existing liquid crystal phased array antennas, the antenna described in this invention offers a simpler structure, lower loss, better circular polarization characteristics, and a wider bandwidth, making it highly valuable for applications in the Ka band. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a side view of the liquid crystal-based broadband circularly polarized phased array antenna of the present invention;

[0029] Figure 2 A top view of the liquid crystal-based broadband circularly polarized phased array antenna according to the present invention;

[0030] Figure 3 Schematic diagram of the connection relationship between the control circuit, bias network and RF DC isolation structure in the liquid crystal-based broadband circularly polarized phased array antenna of the present invention;

[0031] Figure 4 11 is a graph showing an S11 parameter curve and an axial ratio characteristic curve of the broadband circularly polarized phased array antenna based on liquid crystal according to an embodiment;

[0032] Figure 5 : This is the radiation pattern of the beam of the antenna in the embodiment at 27.5 GHz in the elevation plane with an azimuth angle of 90°. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and examples.

[0034] This embodiment provides a broadband circularly polarized phased array antenna based on liquid crystal, the side view of which is shown in FIG. Figure 1 As shown, the top view is Figure 2 As shown, it includes a radiation structure and a feed structure.

[0035] The radiation structure includes a first dielectric substrate 1, a ground plate 2, a sealing frame 3, a liquid crystal layer 4, a phase shifter 5, a second dielectric substrate 6, a third dielectric substrate 7, a first radiation unit 8, a second radiation unit 9, a control circuit, a bias network and an RF DC isolation structure; the first dielectric substrate 1 and the second dielectric substrate 6 are parallel to each other and a distance is left between them; the first radiation unit 8 is located on the upper surface of the first dielectric substrate 1, and includes an N×N two-dimensional periodic array of metal patches 801, where N is a positive integer ≥2, and each metal patch array 801 is composed of 3×3 two-dimensional periodic arrays of first metal patches; the third dielectric substrate 7 is parallel to the first dielectric substrate 1 and the second dielectric substrate 6 is parallel to each other and a distance is left between them; the first radiation unit 8 is located on the upper surface of the first dielectric substrate 1, and includes an N×N two-dimensional periodic array of metal patches 801, where N is a positive integer ≥2, and each metal patch array 801 is composed of 3×3 two-dimensional periodic arrays of first metal patches; The dielectric substrate 7 is located on the upper surface of the first radiating element 8; the second radiating element 9 is located on the upper surface of the third dielectric substrate 7 and includes a second metal patch 901 arranged in an N×N two-dimensional periodic pattern; the phase shifter 5 is located on the upper surface of the second dielectric substrate 6 and includes a metal spiral 501 arranged in an N×N two-dimensional periodic pattern; the ground plate 2 is a metal plate that fully covers the lower surface of the first dielectric substrate 1 and is etched with H-shaped gaps arranged in an N×N two-dimensional periodic pattern; the sealing frame 3 surrounds the edges of the upper surface of the second dielectric substrate 6 and is connected to the first dielectric substrate 1 to form a sealed liquid crystal cell; the liquid crystal cell is filled with a liquid crystal layer 4.

[0036] Since the ground plate 2 is grounded, the dielectric constant of the liquid crystal can be changed by simply adjusting the voltage applied to the metal spiral 501. Figure 3Schematic diagram of the connection relationship between the control circuit, bias network and RF DC isolation structure.

[0037] The control circuit is implemented using an FPGA, and the bias network consists of an N×N array of DC bias lines. The control circuit is connected to the N×N array of metal spirals 501 via these DC bias lines to control the bias voltage of the metal spirals 501. The length of the metal spirals 501 ensures that the phase shift of the phase shifter 5 is greater than 360°. In a 2×2 array of four metal spirals 501, the two diagonal metal spirals 501 are of the same length, while the two metal spirals 501 in the same row or column are of different lengths. To utilize sequential rotational feeding, the two metal spirals 501 in the same row of the 2×2 array are parallel at their initial ends and perpendicular to each other at their final ends (rotation is from outside to inside).

[0038] Liquid crystal devices require both DC bias signals and RF signals, so it is important to isolate the DC and RF signals. If the RF signal flows directly to the DC bias port, the DC bias line will form a large inductance, causing RF impedance mismatch and reducing the transmission or radiation efficiency of the device. Therefore, in this embodiment, an RF-DC isolation structure is also provided. The RF-DC isolation structure is N×N and has a length of one quarter of the waveguide wavelength (λ g / 4) of the open transmission line 202 (inductor); one end of the open transmission line 202 is connected to the DC bias line at a distance of λ from the DC-RF connection point (the connection point between the DC bias line and the metal spiral line) g / 4, and the other end is open; the connection point between the open transmission line 202 and the DC bias line is equivalent to a radio frequency short-circuit point, and the radio frequency signal will no longer continue to be transmitted along the bias line when it reaches the short-circuit point.

[0039] The feeding structure, located below the radiating structure, utilizes a metal waveguide 10, with the waveguide opening located directly below the second dielectric substrate 6. When an RF signal is fed into the waveguide 10, the electromagnetic wave couples to the phase shifter 5. When the electromagnetic wave reaches the end of the phase shifter 5, it passes through the gap in the ground plane and radiates out through the first radiating element 8 and the second radiating element 9.

[0040] In this embodiment, both the first dielectric substrate 1 and the second dielectric substrate 6 are glass substrates with a relative dielectric constant of 5.14. The first dielectric substrate 1 has an area of ​​62 mm × 65.6 mm, the second dielectric substrate 6 has an area of ​​62 mm × 72 mm, and the thicknesses of the first and second dielectric substrates 1 and 6 are 0.7 mm and 0.7 mm, respectively. The third dielectric substrate 7 is a Taconic TLY-3 substrate with a relative dielectric constant of 2.33, an area of ​​52 mm × 52 mm, and a thickness of 0.35 mm. The liquid crystal layer 4 has a thickness of 0.05 mm, and the relative dielectric constant is adjustable within a range of 2.5 to 3.5. The ground plane 2, first radiating element 8, and second radiating element 9 are all 0.002 mm thick. The center frequency f0 is 27.5 GHz. Each first metal patch in the first radiating element 8 has a side length of 0.12λ (approximately 1.35 mm), and a cut angle of 0.8 mm. The spacing between each two adjacent first metal patches in the 3×3 array in the first radiating unit 8 in the horizontal and vertical directions is 0.3 mm. The center distance between each two adjacent 3×3 metal patch arrays in the horizontal and vertical directions in the first radiating unit 8 is 6.5 mm, and the number of arrays is 8×8. The side length of each second metal patch in the second radiating unit 9 is 0.18λ, approximately 2 mm, and the cut angle size is 0.25 mm. The center distance between each two adjacent metal patches in the horizontal and vertical directions is 6.5 mm, and the number of patches is 8×8. The metal wall thickness of the metal waveguide 10 is 1 mm. By independently adjusting the bias voltage of the phase shifter 501 in each radiating unit, the dielectric constant of the liquid crystal of the unit is changed, and the phase compensation of the unit is adjusted. Combined with the beam steering algorithm, the radiation state of each radiating unit in the desired radiation direction can be quickly determined. The control circuit can quickly change the radiation state of each unit to achieve continuous dynamic scanning of the beam in the upper half space.

[0041] The commercial electromagnetic simulation software CST Studio Suite was used to simulate the far-field radiation characteristics of the antenna in this embodiment at 27.5 GHz. The results are as follows: Figure 4 and Figure 5 shown.

[0042] in, Figure 4 is the antenna's S 11 Parameters and axis ratio characteristic diagram, Figure 5 This is the radiation pattern of the antenna beam at 27.5 GHz in the elevation plane with an azimuth angle of 90°, demonstrating the broadband circular polarization characteristics and beam scanning capability of the antenna described in this embodiment.

[0043] The antenna described in this embodiment uses a spiral metal phase shifter, which can control the phase shift amount by changing the bias voltage of the phase shifter, thereby achieving beam scanning; it uses a two-layer rectangular radiating patch structure with cut corners to achieve a liquid crystal-based circularly polarized phased array antenna while ensuring antenna gain.

[0044] The antenna described in this embodiment uses sequential rotational feeding to form an array of antenna elements, addressing the issue of reduced bandwidth associated with array antennas. Metal waveguide feeding avoids the significant losses associated with microstrip line feeding, thereby improving antenna gain. Compared to existing liquid crystal phased array antennas, this invention offers advantages such as circular polarization, wide antenna bandwidth, and low feed network losses.

[0045] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A broadband circularly polarized phased array antenna based on liquid crystal, characterized in that: Including radiation structure and feed structure; The radiation structure comprises a first dielectric substrate (1), a ground plate (2), a sealing frame (3), a liquid crystal layer (4), a phase shifter (5), a second dielectric substrate (6), a third dielectric substrate (7), a first radiation unit (8), a second radiation unit (9), a control circuit, a bias network and a radio frequency direct current isolation structure; The first dielectric substrate (1) and the second dielectric substrate (6) are parallel to each other and spaced apart; the first radiation unit (8) is located on the upper surface of the first dielectric substrate (1), and comprises an N×N two-dimensional periodically arranged metal patch array (801), where N is a positive integer ≥ 2, and each metal patch array (801) is composed of 3×3 two-dimensional periodically arranged first metal patches; the third dielectric substrate (7) is located on the upper surface of the first radiation unit (8); The second radiation unit (9) is located on the upper surface of the third dielectric substrate (7), and includes second metal patches (901) arranged in an N×N two-dimensional periodic pattern; The phase shifter (5) is located on the upper surface of the second dielectric substrate (6) and includes metal spirals (501) arranged in an N×N two-dimensional periodic pattern; the ground plate (2) is a metal plate, which is etched with a gap on the basis of fully covering the lower surface of the first dielectric substrate (1); the sealing frame (3) surrounds the edges of the upper surface of the second dielectric substrate (6) and is connected to the first dielectric substrate (1) to form a sealed liquid crystal box; the liquid crystal box is filled with a liquid crystal layer (4); The control circuit is implemented by FPGA, and the bias network is an N×N DC bias line; the control circuit is connected to the N×N metal spiral lines (501) respectively through the N×N DC bias lines, and is used to control the bias voltage of the metal spiral lines (501); The RF DC isolation structure is N×N and the length is λ g / 4 open transmission line (202), λ g is the waveguide wavelength; one end of the open transmission line (202) is connected to the DC bias line at a distance λ from the connection point of the metal spiral line (501) g / 4, the other end is open; The feeding structure is located below the radiation structure and adopts a metal waveguide (10), and the waveguide port is located directly below the second dielectric substrate (6).

2. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The metal patch array (801) is a 3×3 array composed of diagonally cut first square metal patches, the sides of the first square metal patches are parallel to the sides of the first dielectric substrate (1), and are equidistantly distributed in each direction. The center distance between adjacent metal patch arrays (801) is 0.6λ, where λ is the wavelength corresponding to the center frequency of the antenna operating frequency band, and the cut angle size is 0.8mm. In the metal patch array (801), the spacing between adjacent first metal patches is 0.3mm.

3. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The second metal patch (901) is a diagonally cut second square metal patch, the side of the second square metal patch is parallel to the side of the first square metal patch, and the cut angle is in the same direction as the cut angle of the first metal patch; the second radiation units (901) are equidistantly distributed in each direction, the center distance between adjacent second radiation units (901) is 0.6λ, λ is the wavelength corresponding to the center frequency of the antenna working frequency band, and the cut angle size is 0.25mm.

4. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: H-shaped gaps arranged in an N×N two-dimensional periodic pattern are etched on the ground plate (2), and the period of the H-shaped gaps is the same as that of the metal patch array (801) and the second metal patch (901).

5. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The first dielectric substrate (1) and the second dielectric substrate (6) are glass substrates, and the third dielectric substrate (7) is a printed circuit board substrate.

6. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The relative dielectric constant of the first dielectric substrate (1) and the second dielectric substrate (6) is 5.14; the area of ​​the first dielectric substrate (1) is 62 mm×65.6 mm, and the thickness is 0.7 mm; the area of ​​the second dielectric substrate (6) is 62 mm×72 mm, and the thickness is 0.7 mm; The third dielectric substrate (7) adopts Taconic's TLY-3 substrate, with a relative dielectric constant of 2.

33. The area of ​​the third dielectric substrate (7) is 52 mm×52 mm, and the thickness of the third dielectric substrate (7) is 0.35 mm.

7. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The thickness of the liquid crystal layer (4) is 0.05 mm, and the relative dielectric constant can be adjusted in the range of 2.5 to 3.

5.

8. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The feeding structure adopts a metal waveguide (10), and the thickness of the waveguide metal wall is 1 mm.

9. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The liquid crystal layer (4) is subjected to an alignment treatment. When no bias voltage is applied, the liquid crystal molecules are aligned in the same direction, and the liquid crystal material has a minimum dielectric constant. When a bias voltage is applied to the metal spiral line (501), the liquid crystal molecules are deflected, the dielectric constant of the liquid crystal material changes, and the phase shift amount of the corresponding metal spiral line (501) changes, thereby achieving adjustment of the antenna radiation characteristics.

10. The liquid crystal-based broadband circularly polarized phased array antenna according to claim 1, characterized in that: The control circuit calculates the required offset phase and corresponding bias voltage value of each metal helix (501) according to the sequential rotation feed phase compensation principle and the set antenna beam azimuth angle, and applies the bias voltage to each metal helix (501) through the bias network.

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