Ka-band two-dimensional sum-difference beam phased-array antenna based on liquid crystal

Abstract

The invention discloses a Ka-band two-dimensional sum-difference beam liquid crystal phased-array antenna based on liquid crystal, and belongs to the technical field of microwave antennas. The antenna comprises a radiation unit, a glass substrate, an antenna floor, a liquid crystal layer, a phase shift layer, a microstrip ground, a sum-difference beam feed network and a double-layer dielectric substrate. The sum-difference feed network is used for generating a sum beam, an azimuth difference beam and a pitch difference beam, and configuring a sum channel, a pitch difference channel and an azimuth difference channel; the sum-difference feed network and the phase shifter layer are connected through metalized via holes; a beam scanning function can be realized by driving different voltages to change liquid crystal dielectric constants; the two-dimensional sum-difference beam phased-array antenna is formed by using liquid crystal phase shift, has the characteristics of low cost, low power consumption, easiness in processing and the like, and has a wide prospect in the fields of satellite tracking communication and antenna signal arrival angle estimation.

Description

A Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal Technical Field

[0001] This invention belongs to the field of microwave antenna technology, specifically relating to a Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal. Background Technology

[0002] With the continuous development of phased array technology, liquid crystal phased array antennas, as a new type of phased array antenna, are gradually emerging due to their unique advantages. Liquid crystal materials possess excellent electro-optical properties, and their dielectric constant can be adjusted by an external electric field. This characteristic enables liquid crystal phased array antennas to achieve flexible control of the beam phase. Compared with traditional phased array antennas, liquid crystal phased array antennas have many significant advantages.

[0003] In terms of cost, liquid crystal materials are relatively inexpensive, and the structural design of liquid crystal phased array antennas is relatively simple, reducing a large number of complex phase shifters and other components, thereby significantly reducing production and manufacturing costs. In terms of size and weight, liquid crystal phased array antennas do not require bulky mechanical structures and numerous electronic components, resulting in a more compact structure and lighter weight. This makes them ideal for applications with strict limitations on device size and weight, such as aerospace equipment and portable communication terminals.

[0004] In terms of power consumption, liquid crystal phased array antennas change the phase by modulating the orientation of liquid crystal molecules with an electric field, requiring less energy. Compared to the high power consumption of traditional phased array antennas with numerous phase shifters, they have a significant energy-saving advantage. Furthermore, liquid crystal phased array antennas exhibit excellent performance over a wide frequency range, adapting to the communication and detection needs of different frequency bands, further expanding their application areas.

[0005] However, despite the many advantages mentioned above, liquid crystal phased array antennas also have a significant drawback: they cannot perform angle-of-arrival estimation like digital phased arrays. Angle-of-arrival estimation is a critical function in many communication and radar systems, determining the direction of the incident signal and is essential for applications such as target location and signal tracking.

[0006] Digital phased arrays are able to estimate the angle of arrival (Angle of Arrival) because each antenna element is equipped with an independent transmit / receive channel, enabling individual digitization of the signal received by each element. By collecting and analyzing information such as the amplitude and phase of the received signal from each element, and using relevant algorithms (such as the MUSIC algorithm and the ESPRIT algorithm), the Angle of Arrival (Angle of Arrival) of the signal can be accurately calculated.

[0007] The working principle of a liquid crystal phased array antenna is to achieve phase modulation by changing the dielectric constant of the liquid crystal, and its signal processing is mainly performed in the analog domain. Liquid crystal phased array antennas typically employ a centralized signal processing approach, with multiple antenna elements sharing a single signal processing link. This prevents independent, high-precision sampling and digitization of the signals received by each antenna element. Consequently, liquid crystal phased array antennas cannot acquire detailed phase and amplitude information of the signals received by each element, which is essential for angle-of-arrival (AOA) estimation. Therefore, liquid crystal phased array antennas have inherent limitations in AOA estimation and cannot achieve the precise AOA estimation capabilities of digital phased arrays. This limits their use in applications requiring precise target localization and direction detection. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal. It introduces an orthogonal hybrid network to construct a sum-difference beam feeding structure and combines liquid crystal phase shifting to achieve beam direction control, laying the foundation for subsequent applications based on the sum-difference angle measurement principle in satellite tracking communication and antenna signal angle of arrival estimation.

[0009] The objective of this invention is achieved through the following technical solution: a Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal, the antenna comprising a radiating element, a glass substrate, an antenna ground plane, a liquid crystal layer, a phase-shifting layer, an upper dielectric substrate, a microstrip ground plane, a lower dielectric substrate, and a sum-difference beam feed network.

[0010] The radiating element is located on the upper surface of the glass substrate and consists of 16×16 two-dimensional periodically arranged metal patches; the antenna ground is a metal plate located on the lower surface of the glass substrate, with a slot at the corresponding position of each metal patch.

[0011] The phase-shifting layer is located on the upper surface of the upper dielectric substrate and consists of 16×16 two-dimensional periodically arranged metal delay lines; the liquid crystal layer is located between the antenna ground and the phase-shifting layer.

[0012] The sum and difference beam feed network is located on the lower surface of the lower dielectric substrate; the microstrip ground plane is located between the upper and lower dielectric substrates.

[0013] The metal patch has a circular structure, and the metal delay line has a spiral structure; all metal patches and metal delay lines are equidistantly distributed; the center distance between adjacent metal patches and the center distance between adjacent metal delay lines are both λ / 2, where λ is the wavelength corresponding to the center frequency of the antenna's operating frequency band.

[0014] The upper and lower dielectric substrates are printed circuit board substrates.

[0015] The sum and difference beam feed network and each metal delay line in the phase shift layer are connected by metallized vias.

[0016] The thickness of the liquid crystal layer is 0.05 mm, and the relative permittivity is adjustable in the range of 2.5 to 3.5.

[0017] The sum-difference beam feed network consists of four orthogonal hybrid networks plus a 90° phase delay line.

[0018] The sum-difference beam feed network is configured with sum channel, elevation difference channel and azimuth difference channel; the signals received through all receiving channels are in phase with the received wave in the sum channel, the phase of the received beam in the elevation difference channel is 180° between the upper and lower halves, and the phase of the received beam in the azimuth difference channel is 180° between the left and right halves.

[0019] The beneficial effects of this invention are as follows: This invention provides a liquid crystal-based sum-difference beamforming phased array antenna that can simultaneously receive sum beams, azimuth difference beams, and elevation difference beams. This invention employs a high-precision integrated design of four orthogonal hybrid networks with delay lines and a 16×16 two-dimensional liquid crystal phase-shifting layer, achieving independent feeding and beamforming for the sum channel, elevation difference channel, and azimuth difference channel. The channel isolation is excellent, and the phase consistency error is small. This design provides the necessary hardware foundation for angle-of-arrival estimation based on the sum-difference angle measurement principle, filling a key technological gap in the field of spatial signal direction sensing for liquid crystal antennas. It upgrades liquid crystal antennas from simply achieving beam pointing control to becoming intelligent antenna systems with spatial direction sensing capabilities, laying the foundation for the development of next-generation intelligent antenna technology. Attached Figure Description

[0020] Figure 1 is a side view of the Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to the present invention.

[0021] Figure 2 is a perspective view of the Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to the present invention.

[0022] Figure 3 is a schematic diagram of the structure of the radiation unit of the present invention;

[0023] Figure 4 is a schematic diagram of the antenna floor structure of the present invention;

[0024] Figure 5 is a schematic diagram of the phase-shifting layer of the present invention;

[0025] Figure 6 is a schematic diagram of the structure of the metal delay line of the present invention;

[0026] Figures 7 to 9 are schematic diagrams of the sum-difference beam feed network, where Figure 7 is the overall structure of the sum-difference beam feed network, and Figures 8 and 9 are enlarged views of the parts.

[0027] Figure 10 shows the antenna radiation patterns at 30 GHz and the beam and elevation difference beam on the elevation plane when the azimuth angle is 0°.

[0028] Figure 11 shows the antenna radiation patterns at 30 GHz and the beam and azimuth difference beam on the elevation plane when the azimuth angle is 90°.

[0029] Explanation of reference numerals in the attached figures: 1-Radiating element, 2-Glass substrate, 3-Antenna ground plane, 4-Liquid crystal layer, 5-Phase shifting layer, 6-Upper dielectric substrate, 7-Microstrip ground plane, 8-Lower dielectric substrate, 9-Sum and difference beam feed network, 101-Metal patch, 501-Metal delay line, 906-Metalized via. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] As shown in Figures 1 and 2, the present invention provides a Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal. The antenna includes a radiating element 1, a glass substrate 2, an antenna ground plane 3, a liquid crystal layer 4, a phase shifting layer 5, an upper dielectric substrate 6, a microstrip ground plane 7, a lower dielectric substrate 8, and a sum-difference beam feed network 9.

[0032] The radiating element 1 is located on the upper surface of the glass substrate 2 and consists of 16×16 two-dimensional periodically arranged metal patches 101, as shown in Figure 3. The antenna ground plane 3 is a metal plate located on the lower surface of the glass substrate 2, with slits at corresponding positions of each metal patch 101, as shown in Figure 4. In this embodiment, the thickness of both the metal patches 101 and the antenna ground plane 3 is 0.002 mm.

[0033] The phase-shifting layer 5 is located on the upper surface of the upper dielectric substrate 6 and is composed of 16×16 two-dimensional periodically arranged metal delay lines 501, as shown in Figure 5; the liquid crystal layer 4 is located between the antenna ground plane 3 and the phase-shifting layer 5.

[0034] The sum and difference beam feed network 9 is located on the lower surface of the lower dielectric substrate 8; the microstrip ground plane 7 is located between the upper dielectric substrate 6 and the lower dielectric substrate 8, and an aperture is opened on the microstrip ground plane 7 at each feed position of the sum and difference beam feed network.

[0035] As shown in Figure 2, the metal patch 101 has a circular structure, and the metal delay line 501 has a helical structure with equal pitch. The structure of the metal delay line 501 is shown in Figure 6. All metal patches 101 and metal delay lines 501 are equidistantly distributed in each direction. The center-to-center distance between adjacent metal patches 101 and adjacent metal delay lines 501 is λ / 2, where λ is the wavelength corresponding to the center frequency of the antenna operating frequency band. In this embodiment, the center frequency f0 is taken as 30 GHz. The diameter of each metal patch 101 in the radiating element 1 is approximately 1.92 mm; the center-to-center distance between any two adjacent metal patches 101 is 5 mm, and the number of patches is 16 × 16.

[0036] The upper dielectric substrate 6 and the lower dielectric substrate 8 are printed circuit board substrates. In this embodiment, both use Rogers 5880 dielectric substrates, which have a relative permittivity of 2.2. In this embodiment, the area of ​​the glass substrate 2, the upper dielectric substrate 6, and the lower dielectric substrate 8 are all 120mm × 120mm. The thickness of the upper dielectric substrate 6 and the lower dielectric substrate 8 is 0.254mm.

[0037] Each metal delay line 501 in the sum and difference beam feed network 9 and the phase shift layer 5 is connected by a metallized via 906.

[0038] The thickness of the liquid crystal layer 4 is 0.05 mm, and the relative permittivity can be adjusted in the range of 2.5 to 3.5.

[0039] The sum-difference beam feed network 9 consists of four orthogonal hybrid networks 901 and a 90° phase delay line 902, with a 45° chamfer at the microstrip corner to reduce loss. Its structure is shown in Figure 7. The sum-difference beam feed network 9 is configured with a sum channel 903, an elevation difference channel 904, and an azimuth difference channel 905. The received beam in the sum channel 903 has the same phase, the received beam in the elevation difference channel 904 has a phase difference of 180° between the upper and lower halves, and the received beam in the azimuth difference channel 905 has a phase difference of 180° between the left and right halves. Electromagnetic waves passing through the sum channel 903 can form a sum beam, electromagnetic waves passing through the elevation difference channel 904 can form an elevation difference beam, and electromagnetic waves passing through the azimuth difference channel 905 can form an azimuth difference beam. These three beams can be used to estimate the angle of arrival of the incoming signal. The sum and difference feed network and the phase shifter layer are connected through metallized vias 906; beam scanning can be achieved by changing the dielectric constant of the liquid crystal by driving different voltages.

[0040] As shown in Figure 8, the sum-difference feed network 9 includes four orthogonal hybrid networks 901 and multiple 90° phase delay lines 902. The sum-difference feed network 9 includes three input channels: a sum channel 903, a pitch difference channel 904, and an azimuth difference channel 905, and one isolation channel. The input signal of the sum channel 903 is connected to the first orthogonal hybrid network after passing through the first 90° phase delay line, and the input signal of the pitch difference channel 904 is directly connected to the first orthogonal hybrid network. The first orthogonal hybrid network splits the received signal into two outputs, where the first output signal is connected to the second orthogonal hybrid network after passing through the second 90° phase delay line, and the second output signal is connected to the fourth orthogonal hybrid network. The network consists of two quadrature hybrid networks. The second quadrature hybrid network splits the signal into two outputs. The first output signal is connected to the third 90° phase delay line before being output, while the second output signal is output directly. The input signal of the azimuth difference channel 905 is connected to the third quadrature hybrid network, and the isolation channel is also connected to the third quadrature hybrid network. The third quadrature hybrid network splits the signal into two outputs. One output signal is connected to the fourth quadrature hybrid network after passing through the fourth 90° phase delay line, while the other output signal is connected to the second quadrature hybrid network. The fourth quadrature hybrid network splits the signal into two outputs. The first output signal is output after passing through the fifth 90° phase delay line, while the other output signal is output directly. The second and fourth quadrature hybrid networks each have two output channels. These four output channels are connected to power dividers, which divide the signal energy into 256 outputs. Each output is connected to a metal delay line 501 through a metallized via 906, as shown in Figure 9.

[0041] The feeding principle is similar to that of channel 903, elevation difference channel 904, and azimuth difference channel 905. Taking the elevation difference channel 904 as an example, the radio frequency signal enters through the elevation difference channel 904, and after passing through the first orthogonal mixing network, it is divided into two signals, signal a and signal b. The phase of signal b lags behind the phase of signal a by 90°. Then, signal b passes through the second 90° phase delay line 902 for phase delay, and its phase lags behind the phase of signal a by 180°. Signal a passes through the fourth orthogonal mixing network located below and is divided into two signals, signal aa and signal ab. The phase of signal ab lags behind the phase of signal aa by 90°. Then, signal aa passes through the fifth 90° phase delay line and its phase is consistent with that of signal ab. Similarly, signal b passes through the second orthogonal mixing network located above and the third 90° phase delay to obtain two signals, signal ba and signal bb, with equal phase. Finally, the phases of signals ba and bb lag behind the phases of signals aa and ab by 180°, resulting in a 90° phase difference between the upper and lower halves of the antenna array, forming an elevation difference beam. The angle of arrival of the incoming wave signal can be estimated by using three types of beams formed by the sum and difference feed network.

[0042] The far-field radiation characteristics of the antenna described in this embodiment at 30 GHz were simulated using the commercial electromagnetic simulation software CST Studio Suite. The results are shown in Figures 10 and 11. Figures 10 and 11 show the radiation patterns of the antenna at 30 GHz with and without the beam difference beam on the elevation plane at an azimuth angle of 0°, and with and without the beam difference beam on the elevation plane at an azimuth angle of 90°. Figures 10 and 11 demonstrate the sum and difference beamforming capability of the antenna described in this embodiment, providing the necessary hardware foundation for subsequent angle of arrival estimation based on the sum and difference angle measurement principle.

[0043] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal, characterized in that, The antenna includes a radiating element (1), a glass substrate (2), an antenna ground plane (3), a liquid crystal layer (4), a phase shifting layer (5), an upper dielectric substrate (6), a microstrip ground plane (7), a lower dielectric substrate (8), and a sum-difference beam feed network (9); the radiating element (1) is located on the upper surface of the glass substrate (2) and is composed of 16×16 two-dimensional periodically arranged metal patches (101); the antenna ground plane (3) is a metal plate located on the lower surface of the glass substrate (2), with a slot at the corresponding position of each metal patch (101); the phase shifting layer (5) is located on the upper surface of the upper dielectric substrate (6) and is composed of 16×16 two-dimensional periodically arranged metal delay lines (501); the liquid crystal layer (4) is located between the antenna ground plane (3) and the phase shifting layer (5); The sum and difference beam feed network (9) is located on the lower surface of the lower dielectric substrate (8); the microstrip ground plane (7) is located between the upper dielectric substrate (6) and the lower dielectric substrate (8).

2. The Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to claim 1, characterized in that, The metal patch (101) has a circular structure, and the metal delay line (501) has a spiral structure; all metal patches (101) and metal delay lines (501) are equidistantly distributed; the center distance between adjacent metal patches (101) and the center distance between adjacent metal delay lines (501) are both λ / 2, where λ is the wavelength corresponding to the center frequency of the antenna operating frequency band.

3. The Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to claim 1, characterized in that, The upper dielectric substrate (6) and the lower dielectric substrate (8) are printed circuit board substrates.

4. The Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to claim 1, characterized in that, Each metal delay line (501) in the sum and difference beam feed network (9) and the phase shift layer (5) is connected by a metallized via (906).

5. The Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to claim 1, characterized in that, The thickness of the liquid crystal layer (4) is 0.05 mm, and the relative permittivity is adjustable in the range of 2.5 to 3.

5.

6. The Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to claim 1, characterized in that, The sum-difference beam feed network (9) is composed of four orthogonal hybrid networks (901) plus a 90° phase delay line (902).

7. The Ka-band two-dimensional sum-difference beam phased array antenna based on liquid crystal according to claim 1, characterized in that, The sum and difference beam feed network (9) is equipped with a sum channel (903), an elevation difference channel (904) and an azimuth difference channel (905).

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