Heterogeneous substrate integrated broadband liquid crystal phased antenna array

Abstract

The invention relates to the technical field of microwave antennas, and discloses a broadband liquid crystal phased antenna array integrated by heterogeneous substrates. The heterogeneous substrate integrated broadband liquid crystal phased antenna array comprises a radiation structure, a liquid crystal phase shifter structure and a feed network structure. The radiation structure and the feed network are arranged on two sides of the metal floor in a layered manner, so that the problem that the radiation performance of the antenna is influenced by the radiation of the microstrip feed network is solved; the radiation structure adopts a double-layer structure to realize broadband radiation, energy transmission adopts a copper column direct connection mode, a metal floor wide gap etching process is omitted, and the radiation stability and reliability are improved; non-direct-connection energy transmission between the feed network and the phase shift line is realized by adopting small-sized flat plate coupling, waveguide feed is avoided, and the overall thickness of the antenna is reduced.

Description

A broadband liquid crystal phased array integrated on a heterogeneous substrate Technical Field

[0001] This invention relates to the field of microwave antenna technology, and more specifically to a broadband liquid crystal phased array integrated on a heterogeneous substrate. Background Technology

[0002] With the rapid iteration of communication technologies, 5G technology has gradually matured and the industry scale continues to expand. However, breakthroughs are still needed in core issues such as insufficient coverage breadth and depth. These technical pain points have become an important driving force for the accelerated development of 6G. In the 6G technology system, satellite internet is one of the key supporting technologies, and it has entered a stage of rapid development in recent years. Low-Earth orbit satellite internet, with its outstanding advantages such as low transmission latency, low link loss, and flexible launch and deployment, has become the mainstream implementation path for satellite internet. It can provide efficient internet access solutions for remote areas and network coverage blind spots, and can also meet the diverse needs of mobile communication, emergency communication, and other scenarios, with extremely broad application prospects.

[0003] However, the high-speed movement of low-Earth orbit satellites relative to ground terminals poses a significant challenge to stable communication links. Traditional phased array antennas mostly use narrowband devices with limited bandwidth, and rely on mechanically scanned antennas to achieve single-beam movement. This results in inflexible beam shape adjustment, making it difficult to achieve multi-beam movement modes. Furthermore, increasing the beam scanning angle can lead to problems such as gain reduction and beamwidth widening. Traditional phased array antennas also suffer from poor integration, large size, and high cost due to the combination of multiple components. Summary of the Invention

[0004] To address the aforementioned shortcomings in the prior art, this invention aims to provide a broadband liquid crystal phased array antenna array integrated with a heterogeneous substrate, thereby solving the problems of limited bandwidth, difficulty in achieving multiple moving beam modes, and poor integration in existing traditional phased array antennas.

[0005] To achieve the aforementioned objectives, the present invention provides a broadband liquid crystal phased array antenna array integrated on a heterogeneous substrate, comprising a radiating array layer, a liquid crystal phase shifter, and a feeding network structure arranged sequentially from top to bottom, all integrated via a heterogeneous substrate; wherein: the radiating array layer comprises multiple radiating elements arranged in an M×N two-dimensional periodic pattern, each radiating element being a double-layer patch structure and comprising a first radiating element on the upper layer and a second radiating element on the lower layer; the liquid crystal phase shifter comprises multiple liquid crystal phase shifter units corresponding one-to-one with and vertically aligned with the radiating elements, each liquid crystal phase shifter unit comprising a section of metal spiral microstrip line, a liquid crystal layer covering the lower side of the metal spiral microstrip line, and a metal ground plane located below the liquid crystal layer; the metal spiral microstrip line is connected to the corresponding... The second radiating unit is electrically connected; the feeding network structure includes a feeding network, and the multiple output terminals of the feeding network are respectively coupled to one end of the corresponding metal spiral microstrip line in a non-contact energy coupling manner through a coupling structure; the coupling structure includes a first coupling patch arranged sequentially from top to bottom, a rectangular slot opened on the metal floor, and a second coupling patch located in the rectangular slot. The first coupling patch is connected to the metal spiral microstrip line, and the second coupling patch is connected to the output terminal of the feeding network through a second vertical interconnection structure; each metal spiral microstrip line is also connected to an independent bias network for applying an adjustable bias voltage to change the equivalent dielectric constant of the corresponding liquid crystal layer, thereby realizing independent phase modulation of each radiating channel, and thus realizing beam scanning in multiple dimensions.

[0006] In this invention, the radiating array layer employs a two-dimensional periodically arranged double-layer patch structure unit of M×N. Each unit comprises an upper first radiating element and a lower second radiating element. This double-layer structure generates multiple resonances through electromagnetic coupling, which is an effective means of extending the antenna's operating bandwidth.

[0007] The liquid crystal phase shifter is a distributed structure containing multiple phase shifter units, each corresponding to a radiating unit. The core of each unit is a segment of a metal spiral microstrip line, covered by a liquid crystal layer, with a metal ground plane below. The signal phase propagation speed on the microstrip line is modulated by the dielectric constant of the liquid crystal. A first vertical interconnect structure directly connects the metal spiral microstrip line and the second radiating unit, establishing a direct, short-path energy channel from the phase shifter to the radiator.

[0008] In the feed network structure and coupling structure, the output of the feed network is not directly connected to the phase shifter, but rather achieves contactless energy transfer through a unique coupling structure. This coupling structure consists of a first coupling patch connected to the microstrip line, a rectangular slot on the metal ground plane, and a second coupling patch (1101) within the slot, and is connected to the feed network through a second vertical interconnect structure. Energy is transferred through the metal ground plane and the liquid crystal layer via capacitive coupling between the two coupling patches.

[0009] The bias network sets up an independent bias network for each metal spiral microstrip line. By applying an adjustable voltage to change the molecular orientation of the liquid crystal layer in the corresponding region, the equivalent dielectric constant is continuously changed, thereby realizing independent and continuous control of the phase of the signal in that channel.

[0010] The entire antenna has a clear hierarchical architecture, which facilitates the independent design and optimization of each functional module and is conducive to three-dimensional integration to achieve a low profile. The dual-layer radiating element provides the foundation for broadband operation of the antenna. The non-contact planar coupling feeding mechanism utilizes the characteristics of capacitive coupling to naturally block the leakage of bias DC voltage to the feeding circuit, perfectly solving the problem of isolation between feeding and bias. No additional isolation components are required, simplifying the design and improving reliability. Each liquid crystal phase shifter unit is independently addressed, and by controlling the phase of each channel, arbitrary two-dimensional scanning and shaping of the beam in the elevation and azimuth dimensions can be achieved.

[0011] Furthermore, the heterogeneous substrate includes a PCB dielectric substrate, a first glass substrate, and a second glass substrate stacked from top to bottom; the first radiating unit is fabricated on the upper surface of the PCB dielectric substrate; the second radiating unit is fabricated on the upper surface of the first glass substrate; the metal spiral microstrip line is fabricated on the lower surface of the first glass substrate; the metal ground plane is fabricated on the upper surface of the second glass substrate; the feed network is fabricated on the lower surface of the second glass substrate or on a separate feed substrate; the PCB dielectric substrate and the first glass substrate are bonded together with adhesive; a cavity is formed between the first glass substrate and the second glass substrate by an encapsulation frame, and the cavity is filled with liquid crystal material to form the liquid crystal layer; this fully utilizes the advantages of different substrate materials (PCB is conducive to radiative patch processing, and glass is conducive to liquid crystal encapsulation and low-loss microwave transmission), achieving high-performance heterogeneous integration. The glass substrate provides an ideal encapsulation environment for the liquid crystal, ensuring the consistency and stability of the phase shifter performance.

[0012] Furthermore, both the first and second vertical interconnect structures are copper pillars. The first vertical interconnect structure penetrates the first glass substrate, with its top end connected to the second radiating unit and its bottom end connected to the metal spiral microstrip line. The second vertical interconnect structure penetrates the second glass substrate, with its top end connected to the second coupling patch and its bottom end connected to the feed network. The copper pillars provide a low-loss, low-inductance vertical transmission path, resulting in high signal transmission efficiency. Vertical interconnects significantly save planar layout space and are key to achieving high-density, miniaturized arrays, with a robust and reliable structure.

[0013] Furthermore, the metal spiral microstrip line is a planar spiral formed by rotating the microstrip line counterclockwise or clockwise, with a total electrical length greater than one wavelength, and it is chamfered at the corners to maintain a consistent linewidth; the metal floor is etched with multiple micro H-beams distributed along the direction of the metal spiral microstrip line.

[0014] Metal spiral microstrip lines employ a planar spiral design (such as a square spiral), with an electrical length much greater than the wavelength, enabling a larger phase change range within a limited area. Corner chamfering improves impedance continuity and reduces reflection. Miniature H-slots etched into the metal substrate, distributed along the microstrip line, are used for fine-tuning the electric field distribution beneath the microstrip line. The spiral structure achieves miniaturization and large phase shift in the phase shifter. These miniature H-slots effectively enhance the efficiency of the electric field's effect on liquid crystal molecules, thereby reducing the driving voltage, increasing phase shift sensitivity, and potentially improving the frequency response characteristics of the liquid crystal phase shifter.

[0015] Furthermore, the thickness of the liquid crystal layer is from 0.01 mm to 0.05 mm, and its relative permittivity is adjustable within the range of 2.55 to 3.75 after applying a bias voltage. The thickness range (0.01 mm to 0.05 mm) balances the driving voltage, response speed, and manufacturing difficulty. The adjustable dielectric constant range (2.55 to 3.75) directly determines the maximum phase change that the phase shifter can provide, and this range must meet the phase control range required for beam scanning.

[0016] Furthermore, in the coupling structure, the first coupling patch and the second coupling patch overlap in the vertical projection, and the two are the same or similar in size, forming a coupler in the form of a parallel plate capacitor, separated by the liquid crystal layer and the rectangular gap.

[0017] Furthermore, the feed network is a 1-to-64 microstrip power divider, arranged in a five-stage 1-to-2 T-junction microstrip power divider cascade structure. Each output of the last stage power divider in the feed network has an impedance matching stub, which is connected to the second coupling patch via the second vertical interconnect structure. This provides a mature and reliable feed network implementation scheme, ensuring that energy is evenly and efficiently distributed to all 64 radiation channels. The matching stub optimizes the overall impedance matching, guaranteeing the antenna's broadband performance.

[0018] Furthermore, the bias network includes an AC bias line connected to each of the metal spiral microstrip lines, and an RF isolation line disposed on the AC bias line. The RF isolation line is an open-circuit transmission line with a length equal to one-quarter of the operating waveguide wavelength. One end of the line is connected to the AC bias line at a distance of one-quarter of the waveguide wavelength from the connection point of the metal spiral microstrip line, and the other end is open. At the RF operating frequency, this stub presents a high impedance at its connection point that is approximately a short circuit, effectively preventing the RF signal from radiating or leaking outward through the bias line. This ensures that the RF energy is confined within the phase shifter and radiator, while not affecting the application of the low-frequency bias voltage, thus realizing RF choking on the bias line.

[0019] Furthermore, all the AC bias lines are connected to a bias voltage control circuit. This circuit calculates the required phase shift for each radiating element based on a preset beam pointing formula and converts it into a corresponding bias voltage value for independent application. The bias voltage control circuit is implemented using a field-programmable gate array (FPGA) or a microprocessor. All AC bias lines are ultimately driven by a unified bias voltage control circuit (such as an FPGA). The control circuit calculates the required phase value for each element based on the target beam pointing using phased array theory formulas. Then, it generates a corresponding analog voltage signal by looking up a table or calculating using a pre-stored voltage-phase relationship and applying it to each phase shifter element. This achieves centralized, rapid, and digital control of hundreds or thousands of phase shifter elements across the entire array. It supports complex beam scanning modes (such as circular scanning and random beam skipping) and beamforming (such as multi-beam and low sidelobes).

[0020] Furthermore, M and N are both positive integers greater than or equal to 4, and M and N may be equal or different; the center spacing between adjacent radiating elements is 0.5λ to 0.7λ, where λ is the wavelength corresponding to the center frequency of the antenna operating band, to avoid grating lobes and control mutual coupling.

[0021] Compared with existing traditional phased array antennas, the beneficial effects of this invention are as follows: 1. This invention provides a broadband liquid crystal phased array antenna array integrated on a heterogeneous substrate. The liquid crystal phase shifter adopts a forward-facing structure. The lower surface of the first glass substrate is set as a phase-shifting line layer, and the upper surface of the second glass substrate is set as a metal ground plane layer. This design abandons the traditional inverted phase-shifting line structure. The use of a metal copper pillar structure achieves efficient energy transmission from the phase-shifting line to the secondary radiating antenna. After coupling via the secondary radiating patch, the energy further excites the main radiating patch to complete signal radiation. This structure compensates for the narrow bandwidth of the antenna radiation, enabling broadband radiation. This design eliminates the traditional slot coupling method, saving the process of etching wide slots on the metal ground plane, effectively avoiding the adverse effects of slot energy radiation on the overall radiation performance of the antenna, and significantly improving the stability and reliability of the antenna structure's radiation.

[0022] 2. This invention provides a broadband liquid crystal phased array antenna array integrated on a heterogeneous substrate. Regarding the connection between the liquid crystal phase shifter and the feed network, due to the presence of the liquid crystal, a suitable connection method has been lacking. This invention uses a small planar coupling method to transmit energy from the feed network to the metal line. This structure is small in size and has weak radiated energy, making it effective for connecting the liquid crystal phase shifter and the feed network. Since the feed network and the phase shift line are not directly connected, the use of complex DC-blocking structures is avoided. This small planar coupling structure transmits radio frequency signals while blocking the bias voltage, independently biasing the microstrip phase shift line and avoiding biasing the feed network, thereby achieving two-dimensional beam control. Simultaneously, it replaces the traditional waveguide feeding method, effectively reducing the overall thickness of the antenna. Attached Figure Description

[0023] Figure 1 is a side view of the broadband liquid crystal phased array antenna array based on a heterogeneous substrate integrated according to the present invention; Figure 2 is a top view of the broadband liquid crystal phased array antenna array based on a heterogeneous substrate integrated according to the present invention; Figure 3 is a schematic diagram of the radiating structure of the broadband liquid crystal phased array antenna array based on a heterogeneous substrate integrated according to the present invention; Figure 4 is a schematic diagram of the connection between the metal spiral microstrip line phase shifter layer and the bias network in the broadband liquid crystal phased array antenna array based on a heterogeneous substrate integrated according to the present invention; Figure 5 is a schematic diagram of the metal ground plane layer in the broadband liquid crystal phased array antenna array based on a heterogeneous substrate integrated according to the present invention; Figure 6 is a schematic diagram of the stacked structure of the coupling between the phase shifter line and the feed network in the broadband liquid crystal phased array antenna array based on a heterogeneous substrate integrated according to the present invention.

[0024] Figure 7 is a schematic diagram of the feed network structure of the broadband liquid crystal phased array based on a heterogeneous substrate integrated according to the present invention; Figure 8 is a graph showing the S-parameters and gain of the broadband liquid crystal phased array based on a heterogeneous substrate integrated according to the present invention as a function of frequency; Figure 9 is a diagram showing the forward direction and beam scanning ±30° along the X-axis of the broadband liquid crystal phased array based on a heterogeneous substrate integrated according to the present invention; Figure 10 is a diagram showing the forward direction and beam scanning ±30° along the Y-axis of the broadband liquid crystal phased array based on a heterogeneous substrate integrated according to the present invention.

[0025] The components are as follows: 1. PCB dielectric substrate; 2. Adhesive; 3. First glass substrate; 4. Sealing frame; 5. Second glass substrate; 6. Power supply network; 601. Matching stub; 7. First radiating unit; 8. Second radiating unit; 9. Metal spiral microstrip line; 901. First coupling patch; 902. AC bias line; 903. RF isolation line; 10. Liquid crystal layer; 11. Metal ground plane; 1101. Second coupling patch; 1102. Micro H-beam gap; 1103. Rectangular gap; 12. First vertical interconnect structure; 13. Second vertical interconnect structure. Detailed Implementation

[0026] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0027] As shown in Figures 1-3, this invention provides a broadband liquid crystal phased array antenna array integrated on a heterogeneous substrate, which includes a radiating array layer, a liquid crystal phase shifter, and a feed network structure arranged sequentially from top to bottom, and the three are integrated through a heterogeneous substrate; wherein: the radiating array layer includes multiple radiating elements arranged in a two-dimensional periodic pattern of M×N, specifically, M and N are both positive integers greater than or equal to 4, and M and N may be equal or different; the center spacing between adjacent radiating elements is 0.5λ to 0.7λ, where λ is the wavelength corresponding to the center frequency of the antenna operating band, to avoid grating lobes and control mutual coupling. Each of the radiating units is a double-layer patch structure and includes a first radiating unit 7 located on the upper layer and a second radiating unit 8 located on the lower layer; the liquid crystal phase shifter includes a plurality of liquid crystal phase shifter units that correspond one-to-one with the radiating units and are vertically aligned. Each liquid crystal phase shifter unit includes a section of metal spiral microstrip line 9, a liquid crystal layer 10 covering the lower side of the metal spiral microstrip line 9, and a metal ground plane 11 located below the liquid crystal layer 10; the metal spiral microstrip line 9 is electrically connected to the corresponding second radiating unit 8 through a first vertical interconnect structure 12.

[0028] The power supply network structure includes a power supply network 6, and the multiple output terminals of the power supply network 6 are respectively coupled to one end of the corresponding metal spiral microstrip line 9 in a non-contact manner through a coupling structure.

[0029] The coupling structure includes a first coupling patch 901 arranged sequentially from top to bottom, a rectangular slot 1103 opened on the metal floor 11, and a second coupling patch 1101 located in the rectangular slot 1103. The first coupling patch 901 is connected to the metal spiral microstrip line 9, and the second coupling patch 1101 is connected to the output end of the power supply network 6 through the second vertical interconnect structure 13.

[0030] Each of the metal spiral microstrip lines 9 is also connected to an independent bias network for applying an adjustable bias voltage to change the equivalent dielectric constant of the corresponding liquid crystal layer 10, thereby achieving independent phase modulation of each radiation channel and thus enabling beam scanning in multiple directions.

[0031] In this invention, the radiating array layer employs a two-dimensional periodically arranged double-layer patch structure unit of M×N. Each unit includes an upper first radiating element 7 and a lower second radiating element 8. This double-layer structure generates multiple resonances through electromagnetic coupling, which is an effective means of extending the antenna's operating bandwidth.

[0032] The liquid crystal phase shifter has a distributed structure, containing multiple phase shifter units corresponding one-to-one with the radiating units. The core of each unit is a section of metal spiral microstrip line 9, covered by a liquid crystal layer 10, and with a metal ground plane 11 below it. The signal phase propagation speed on the microstrip line is modulated by the dielectric constant of the liquid crystal on it. A first vertical interconnect structure 12 directly connects the metal spiral microstrip line 9 and the second radiating unit 8, establishing a direct, short-path energy channel from the phase shifter to the radiator.

[0033] In the power supply network structure and coupling structure, the output of the power supply network 6 is not directly connected to the phase shifter, but rather achieves contactless energy transfer through a unique coupling structure. This coupling structure consists of a first coupling patch 901 connected to the microstrip line, a rectangular slot 1103 on the metal ground plane 11, and a second coupling patch 1101 (1101) within the slot, and is connected to the power supply network through a second vertical interconnect structure 13. Energy is transferred through the metal ground plane 11 and the liquid crystal layer 10 via capacitive coupling between the two coupling patches.

[0034] Each metal spiral microstrip line 9 has an independent bias network. By applying an adjustable voltage to change the molecular orientation of the corresponding liquid crystal layer 10, the equivalent dielectric constant is continuously changed, enabling independent and continuous control of the signal phase of that channel. The entire antenna has a clear layered architecture, which facilitates the independent design and optimization of each functional module and is conducive to three-dimensional integration, achieving a low profile. The double-layer radiating element provides the basis for broadband operation of the antenna. The non-contact planar coupling feeding mechanism, utilizing the capacitive coupling characteristics, naturally blocks the leakage of the bias DC voltage to the feeding network, perfectly solving the problem of isolation between feeding and biasing. No additional isolation components are required, simplifying the design and improving reliability. Each liquid crystal phase shifter unit is independently addressed, and by controlling the phase of each channel, arbitrary two-dimensional scanning and shaping of the beam in the elevation and azimuth dimensions can be achieved.

[0035] Specifically, as a particular configuration of a heterogeneous substrate, the heterogeneous substrate includes a PCB dielectric substrate 1, a first glass substrate 3, and a second glass substrate 5 stacked from top to bottom; the first radiating unit 7 is fabricated on the upper surface of the PCB dielectric substrate 1; the second radiating unit 8 is fabricated on the upper surface of the first glass substrate 3; the metal spiral microstrip line 9 is fabricated on the lower surface of the first glass substrate 3; the metal ground plane 11 is fabricated on the upper surface of the second glass substrate 5; the feed network 6 is fabricated on the lower surface of the second glass substrate 5 or on a separate feed substrate; the PCB dielectric substrate 1 and the first glass substrate 3 are bonded together by adhesive 2; a cavity is formed between the first glass substrate 3 and the second glass substrate 5 by a sealing frame 4, and the cavity is filled with liquid crystal material to form the liquid crystal layer 10; this configuration fully utilizes the advantages of different substrate materials (PCB is conducive to radiative patch processing, while glass is conducive to liquid crystal encapsulation and low-loss microwave transmission), achieving high-performance heterogeneous integration. The glass substrate provides an ideal encapsulation environment for the liquid crystal, ensuring the consistency and stability of the liquid crystal phase shifter performance.

[0036] Furthermore, both the first vertical interconnect structure 12 and the second vertical interconnect structure 13 are copper pillars. The first vertical interconnect structure 12 penetrates the first glass substrate 3, with its top end connected to the second radiating unit 8 and its bottom end connected to the metal spiral microstrip line 9. The second vertical interconnect structure 13 penetrates the second glass substrate 5, with its top end connected to the metal ground plane 11 and its bottom end connected to the feed network 6. The copper pillars provide a low-loss, low-inductance vertical transmission path, resulting in high signal transmission efficiency. Vertical interconnects significantly save planar layout space and are key to achieving high-density, miniaturized arrays, with a robust and reliable structure.

[0037] Further, as shown in Figure 4, the metal spiral microstrip line 9 is formed by rotating a microstrip line of length 4.2λ counterclockwise, with chamfered corners to maintain consistent linewidth. As shown in Figure 5, multiple micro-I-beam slots 1102 distributed along the direction of the metal spiral microstrip line 9 are etched on the metal ground plane 11. The distance between adjacent micro-I-beam slots 1102 is 0.4 mm, and micro-I-beam slots 1102 are also provided at the corners. At the same time, N×N two-dimensional periodically arranged rectangular slots 1103 are also etched on the metal ground plane 11, and a second coupling patch 1101 is etched within the rectangular slots 1103. The second coupling patch 1101 is mainly for energy transmission with the output terminal of the power supply network 6.

[0038] The metal spiral microstrip line 9 adopts a planar spiral shape (such as a square spiral), whose electrical length is much greater than the wavelength, enabling a larger phase change range within a limited area. Corner chamfering improves impedance continuity and reduces reflection. Miniature H-shaped slots 1102 etched on the metal ground plane 11, distributed along the microstrip line, are used for fine-tuning the electric field distribution below the microstrip line. The spiral structure achieves miniaturization and large phase shift of the phase shifter. The miniature H-shaped slots 1102 effectively enhance the efficiency of the electric field on the liquid crystal molecules, thereby reducing the driving voltage, increasing phase shift sensitivity, and potentially improving the frequency response characteristics of the liquid crystal phase shifter.

[0039] Furthermore, the thickness of the liquid crystal layer 10 is 0.01 mm to 0.05 mm, and its relative permittivity is adjustable within the range of 2.55 to 3.75 after applying a bias voltage. The liquid crystal layer 10 undergoes alignment treatment; when no bias voltage is applied, the liquid crystal molecules are aligned, and the liquid crystal material has the minimum permittivity. When a bias voltage is applied to the metal spiral microstrip line 9 through the AC bias line 902, the liquid crystal molecules deflect, the permittivity of the liquid crystal material changes, and the corresponding phase shift of the metal spiral microstrip line 9 changes, thereby achieving phase shift adjustment. The thickness range of the liquid crystal layer 10 (0.01 mm to 0.05 mm) balances the driving voltage, response speed, and manufacturing difficulty. The adjustable range of the permittivity of the liquid crystal layer 10 (2.55 to 3.75) directly determines the maximum phase change that the phase shifter can provide; this range must meet the phase control range required for beam scanning.

[0040] As shown in Figure 6, the main function of the coupling structure is to input the energy from the power supply network 6 into the metal spiral microstrip line. Specifically, in the coupling structure, the first coupling patch 901 and the second coupling patch 1101 overlap in the vertical projection, and their sizes are the same or similar, forming a coupler in the form of a parallel plate capacitor, separated by the liquid crystal layer 10 and the rectangular gap 1103. The first coupling patch 901 and the second coupling patch 1101 form a planar coupling, transmitting energy from the power divider network to the phase shifter. Because they are not directly connected, they act as DC current blockers.

[0041] Further, as shown in Figure 7, the feed network 6 is a 1-to-64 microstrip power divider, arranged in a five-stage 1-to-2 T-junction microstrip power divider cascade structure. Each output of the last stage power divider in the feed network 6 has an impedance matching stub 601, which is connected to the second coupling patch 1101 via the second vertical interconnect structure 13. The feed network 6 is a mature and reliable implementation scheme, ensuring that energy can be evenly and efficiently distributed to all 64 radiation channels. The matching stub 601 optimizes the overall impedance matching, guaranteeing the wideband performance of the antenna.

[0042] Furthermore, the bias network includes an AC bias line 902 connected to each of the metal spiral microstrip lines 9, and an RF isolation line 903 disposed on the AC bias line 902. The RF isolation line 903 is an open-circuit transmission line with a length equal to one-quarter of the working waveguide wavelength. One end of the line is connected to the AC bias line 902 at a distance of one-quarter of the waveguide wavelength from the connection point with the metal spiral microstrip line 9, and the other end is open. At the RF operating frequency, this stub presents a high impedance at its connection point that is approximately a short circuit, effectively preventing the RF signal from radiating or leaking outward through the bias line, ensuring that the RF energy is confined within the phase shifter and radiator, while not affecting the application of the low-frequency bias voltage, thus realizing RF choke on the bias line.

[0043] Furthermore, all the AC bias lines 902 are connected to a bias voltage control circuit. This circuit calculates the required phase shift for each radiating element based on a preset beam pointing formula and converts it into a corresponding bias voltage value for independent application. The bias voltage control circuit is implemented using a field-programmable gate array (FPGA) or a microprocessor. All AC bias lines 902 are ultimately driven by a unified bias voltage control circuit (such as an FPGA). The control circuit calculates the required phase value for each element based on the target beam pointing using phased array theory formulas. Then, it generates a corresponding analog voltage signal by looking up a table or calculating a pre-stored voltage-phase relationship and applying it to each phase shifter element. This achieves centralized, rapid, and digital control of hundreds or thousands of phase shifter elements in the entire array. It supports complex beam scanning modes (such as circular scanning and random beam skipping) and beamforming (such as multi-beam and low sidelobes).

[0044] In this embodiment, Figure 8 shows an S-shaped structure of a broadband liquid crystal phased array integrated on a heterogeneous substrate. 11 Curves showing parameter and gain variations with frequency; S-axis of a liquid crystal phased array antenna. 11 The parameters are all less than -10dB in the frequency range of 17.5GHz-21.5GHz, demonstrating the excellent matching impedance and broadband characteristics of the liquid crystal phased array antenna described in this embodiment. Figure 9 shows the beam pattern of the liquid crystal phased array antenna at 17.5GHz along the X-axis. The highest gain is 15.17dBi in the 0° direction, 14.23dBi in the -30° direction, and 14.48dBi in the +30° direction. Figure 10 shows the beam pattern of the liquid crystal phased array antenna at 17.5GHz along the Y-axis. The highest gain is 15.17dBi in the 0° direction, 14.03dBi in the -30° direction, and 14.31dBi in the +30° direction. This demonstrates the excellent beam scanning capability of the liquid crystal phased array antenna described in this embodiment.

[0045] In summary, the antenna described in this embodiment divides the radiating structure, the feed network 6, and the liquid crystal phase shifter into three parts. By designing the radiating structure and the feed network 6 on the upper and lower sides of the metal ground plane 11, interference from the feed network 6 to the radiating structure is avoided. Simultaneously, the phase shifter adopts a forward-facing structure, with the lower surface of the first glass substrate 3 serving as the phase shifter layer and the upper surface of the second glass substrate 5 serving as the metal ground plane 11 layer; this design abandons the traditional inverted phase shifter structure.

[0046] This invention employs copper pillars for connection, achieving efficient energy transmission from the phase-shifting line layer to the secondary radiating antenna. After coupling via the secondary radiating patch, the energy further excites the primary radiating patch to complete signal radiation. This structure compensates for the narrow bandwidth of the antenna radiation, enabling broadband radiation. This design eliminates the need for etching wide slots in the metal ground plane 11, a process common in traditional solutions, effectively avoiding the adverse effects of slot energy radiation on the overall antenna radiation performance and significantly improving the stability and reliability of the antenna structure's radiation.

Claims

1. A broadband liquid crystal phased array integrated on a heterogeneous substrate, characterized in that, The structure comprises a radiation array layer, a liquid crystal phase shifter, and a power supply network structure arranged sequentially from top to bottom, all integrated via a heterogeneous substrate. The radiation array layer includes multiple radiation units arranged in a two-dimensional M×N pattern. Each radiation unit is a double-layer patch structure, comprising a first radiation unit (7) on the upper layer and a second radiation unit (8) on the lower layer. The liquid crystal phase shifter comprises multiple liquid crystal phase shifter units that correspond one-to-one with and are vertically aligned with the radiation units. Each liquid crystal phase shifter unit comprises a section of metal spiral microstrip line (9), a liquid crystal layer (10) covering the underside of the metal spiral microstrip line (9), and a metal ground plane (11) below the liquid crystal layer (10). The metal spiral microstrip line (9) is electrically connected to the corresponding second radiation unit (8) via a first vertical interconnect structure (12). The power supply network structure includes a power supply network (6). The multiple output terminals of the ) are respectively coupled to one end of the corresponding metal spiral microstrip line (9) through a coupling structure in a non-contact energy coupling manner; the coupling structure includes a first coupling patch (901) arranged sequentially from top to bottom, a rectangular slot (1103) opened on the metal floor (11), and a second coupling patch (1101) located in the rectangular slot (1103). The first coupling patch (901) is connected to the metal spiral microstrip line (9), and the second coupling patch (1101) is connected to the output terminal of the feed network (6) through a second vertical interconnection structure (13); each metal spiral microstrip line (9) is also connected to an independent bias network for applying an adjustable bias voltage to change the equivalent dielectric constant of the corresponding liquid crystal layer (10), thereby realizing independent phase modulation of each radiation channel, and thus realizing beam scanning in multiple directions.

2. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 1, characterized in that, The heterogeneous substrate includes a PCB dielectric substrate (1), a first glass substrate (3), and a second glass substrate (5) stacked from top to bottom; the first radiating unit (7) is fabricated on the upper surface of the PCB dielectric substrate (1); the second radiating unit (8) is fabricated on the upper surface of the first glass substrate (3); the metal spiral microstrip line (9) is fabricated on the lower surface of the first glass substrate (3); the metal ground plane (11) is fabricated on the upper surface of the second glass substrate (5); the power supply network (6) is fabricated on the lower surface of the second glass substrate (5) or on an independent power supply substrate; the PCB dielectric substrate (1) and the first glass substrate (3) are bonded together by adhesive (2); a cavity is formed between the first glass substrate (3) and the second glass substrate (5) by a sealing frame (4), and the cavity is filled with liquid crystal material to form the liquid crystal layer (10).

3. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 2, characterized in that, Both the first vertical interconnect structure (12) and the second vertical interconnect structure (13) are copper pillars; the first vertical interconnect structure (12) penetrates the first glass substrate (3), its top end is connected to the second radiating unit (8), and its bottom end is connected to the metal spiral microstrip line (9); the second vertical interconnect structure (13) penetrates the second glass substrate (5), its top end is connected to the second coupling patch (1101), and its bottom end is connected to the power supply network (6).

4. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 2, characterized in that, The metal spiral microstrip line (9) is a planar spiral line formed by rotating the microstrip line counterclockwise or clockwise. The total electrical length is greater than one wavelength. It is chamfered at the corners to maintain a consistent line width. The metal ground plate (11) is etched with multiple micro H-shaped slots (1102) distributed along the direction of the metal spiral microstrip line (9).

5. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 1, characterized in that, The thickness of the liquid crystal layer (10) is 0.01 mm to 0.05 mm, and its relative permittivity is adjustable between 2.55 and 3.75 after applying a bias voltage.

6. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 1, characterized in that, In the coupling structure, the first coupling patch (901) and the second coupling patch (1101) overlap in the vertical projection, and the two are the same or similar in size, forming a coupler in the form of a parallel plate capacitor, which is separated by the liquid crystal layer (10) and the rectangular gap (1103).

7. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 1, characterized in that, The power supply network (6) is a microstrip power divider that is divided into 64 by 1, and is a cascaded structure of a five-stage T-junction microstrip power divider that is divided into two by 1. Each output terminal of the last stage power divider of the power supply network (6) is provided with an impedance matching stub (601). The impedance matching stub (601) is connected to the second coupling patch (1101) through the second vertical interconnection structure (13).

8. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 1, characterized in that, The bias network includes an AC bias line (902) connected to each of the metal spiral microstrip lines (9), and an RF isolation line (903) disposed on the AC bias line (902); the RF isolation line (903) is an open transmission line with a length equal to one-quarter of the working waveguide wavelength, one end of which is connected to the AC bias line (902) at a distance of one-quarter of the waveguide wavelength from the connection point with the metal spiral microstrip line (9), and the other end is open.

9. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to claim 8, characterized in that, All of the AC bias lines (902) are connected to a bias voltage control circuit, which calculates the required phase shift for each radiating element based on a preset beam pointing formula and converts it into a corresponding bias voltage value for independent application; the bias voltage control circuit is implemented by a field programmable gate array or a microprocessor.

10. The broadband liquid crystal phased array integrated on a heterogeneous substrate according to any one of claims 1-9, characterized in that, M and N are both positive integers greater than or equal to 4, and M and N may be equal or different; the center-to-center spacing between adjacent radiating elements is 0.5λ to 0.7λ, where λ is the wavelength corresponding to the center frequency of the antenna operating band.

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