A directional pattern reconfigurable array antenna based on 4D printing

Abstract

This invention discloses a pattern-reconfigurable array antenna based on 4D printing, comprising an upper substrate, a middle substrate, and a lower substrate. The upper substrate houses a microstrip Yagi radiating element, an irregular metallic ground plane, and peripheral guiding elements. The lower substrate houses a feed network. Six through-holes are provided on the substrates and the ground plane to prevent contact between the two ground planes and the coaxial outer conductor. The peripheral guiding elements are made of PLMC material, and their shape memory effect is triggered by thermal response to achieve a "flat-to-70° folding" structural switching of the antenna, thereby completing pattern reconfiguration. Compared to existing technologies, the antenna designed in this invention is small in size, low in cost, and simple in structure, requiring no additional control unit. It is expected to be applied in satellite communication, base station terminals, radar detection, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of flexible reconfigurable antenna technology, specifically relating to a pattern reconfigurable array antenna based on 4D printing. Background Technology

[0002] In the 1880s, German physicist Hertz created the first antenna, propelling humanity into the era of wireless communication. Through technological evolution and the maturation of electromagnetic wave theory, antennas have become one of the key components determining the overall performance of modern communication systems.

[0003] With the rapid development of the Internet of Things (IoT), 5G, and smart wearable devices, wireless communication systems are placing stringent demands on antenna performance: they must achieve full coverage across multiple frequency bands and modes within a limited physical space, adapt to complex electromagnetic environments, and simultaneously meet the integration requirements of flexible or deformable carriers. Traditional rigid antennas are difficult to adapt to these requirements due to their structural characteristics, thus spurring a surge in the research and development of new antennas such as reconfigurable antennas and flexible antennas.

[0004] Existing reconfigurable antenna technologies mostly employ solutions such as PIN diode switches, varactor diodes, radio frequency micro-electro-mechanical systems (MEMS), mechanical actuators, metamaterials, and liquid crystal materials. These solutions achieve reconfigurable performance parameters by embedding electronic switching components in the antenna radiating element or feed network to regulate the antenna current distribution. However, they require additional control circuitry, are prone to introducing high losses, and negatively impact antenna radiation performance. Furthermore, the discrete control characteristics of these "switches" limit continuous parameter tuning, directly restricting the performance ceiling of reconfigurable antennas. If a mechanical control scheme is used, the low plasticity of the materials and mechanical fatigue after long-term use will significantly affect the realization of reconfigurable characteristics and stable operation.

[0005] Reconfigurable antenna technology is based on the fundamental principles of electromagnetic wave radiation. By controlling the electromagnetic wave characteristics of the antenna radiation, it achieves flexible adjustments to performance parameters such as frequency, polarization, and radiation direction. Therefore, developing a material and implementation method that can flexibly change the antenna's structural form is crucial for breakthroughs in reconfigurable antenna technology.

[0006] Shape memory polymers (SMPs), as a class of smart materials, possess initial shape memory properties. Under external stimuli such as heat, electricity, light, and magnetism, they can be temporarily shaped and fixed. When the same external stimuli are triggered again, they can actively return to their initial shape. This property is called the shape memory effect. SMPs and their composite materials have advantages such as fast shape recovery speed, diverse design forms, light weight, and easy processing, providing a material basis for the development of new antennas.

[0007] Shape memory polylactic acid-trimethylene carbonate (PLMC), as a novel SMP material, combines good biocompatibility with excellent shape memory effect. It achieves shape memory functionality through physical entanglement of molecular chains, eliminating the need for complex chemical cross-linking, and its mechanical properties can be flexibly controlled, demonstrating broad application prospects in fields such as biomedicine. However, this material is not yet widely used in the field of flexible reconfigurable antennas.

[0008] Based on this, a pattern reconfigurable antenna based on the thermal response shape memory effect of PLMC is designed to solve the defects of existing reconfigurable antennas such as high loss, discontinuous performance tuning, and insufficient stability, and to adapt to the application requirements of modern communication equipment. This has become a key research direction in the field of antenna technology. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a pattern reconfigurable array antenna based on 4D printing. The antenna provided by the present invention has excellent flexibility, low loss, and strong mechanical stability. It does not require complex control circuits, has a simple structure, and stable electrical performance. It can realize flexible pattern reconfiguration, adapt to the "flexible integration and multi-mode coverage" requirements of Internet of Things (IoT), 5G, and smart wearable devices, and solve the problems of high loss, limited parameter tuning, or insufficient mechanical stability of existing reconfigurable antennas.

[0010] This invention provides a pattern reconfigurable array antenna based on 4D printing, comprising an upper substrate (S1), an intermediate substrate (S2), and a lower substrate (S3). The upper substrate (S1) is provided with a microstrip Yagi radiating element, an irregular metal ground plane, and peripheral directional elements. The lower substrate (S3) is provided with a feed network. Six coaxial mounting through-holes are correspondingly formed on the upper substrate, intermediate substrate, lower substrate, and the corresponding printed metal ground plane. These through-holes are used to pass through a coaxial line connecting the feed network of the lower substrate and the microstrip Yagi radiating element of the upper substrate. The inner walls of the through-holes are insulated to prevent electrical contact between the irregular metal ground plane of the upper substrate, the metal ground plane of the feed network of the lower substrate, and the outer conductor core of the coaxial line, thus eliminating the risk of short circuits. Six coaxial mounting vias are evenly distributed in a ring around the center of the array. The vias penetrate the upper substrate, middle substrate, lower substrate and the corresponding metal ground plane. The inner walls of the vias are treated with copper plating insulation process. Only the inner conductor of the coaxial line is electrically connected to the corresponding radiating array element and the feed port, which completely avoids accidental contact between the upper and lower metal ground planes and the outer conductor of the coaxial line and ensures the stability of the antenna feed.

[0011] The metal ground planes described in this invention are all copper conductive layers printed on the surface of the corresponding dielectric substrate, which are different from the general ground reference planes. Their core function is to provide current reference for the antenna radiating element, improve impedance matching and suppress reverse radiation. The irregular metal ground plane of the upper substrate is also used as the grounding reflector of the microstrip Yagi radiating element, and the metal ground plane of the lower substrate is the reference ground of the feed network.

[0012] The outer periphery of the upper substrate (S1) is made of PLMC material. Its shape memory effect is triggered by thermal response to realize the structural switching of the antenna from "flat to 70° folding", thereby completing the pattern reconstruction.

[0013] The PLMC used to guide the oscillator around the upper substrate (S1) is prepared by ring-opening polymerization of two monomers, racemic lactide (DLLA) and trimethylene carbonate (TMC), which has both shape memory effect and biocompatibility. The mechanical properties, degradation rate and glass transition temperature (Tg) are controlled by adjusting the ratio of the two comonomers to achieve the shape memory effect.

[0014] The dielectric substrate body that carries the microstrip Yagi radiation array elements and the irregular metal ground plane in the upper substrate (S1), as well as the intermediate substrate (S2), all adopt a relative permittivity. Loss tangent The material is F4BM220; the lower substrate (S3) uses a relative permittivity. Loss tangent The upper substrate (S1) is divided into two functional areas: one is the main body of the dielectric substrate that carries the radiation structure, which uses low-loss, high-flexibility F4BM220 material to ensure antenna radiation efficiency and structural flexibility; the other is the deformable guide oscillator part set on the periphery of the upper substrate, which uses PLMC shape memory polymer material to achieve structural shape switching through thermal response and complete antenna pattern reconstruction.

[0015] The power supply network is based on a Luzzato power divider with a 1-to-3 disc shape. Each of the three output ports is cascaded with a Wilkinson power divider to form a six-way equal-phase output network. The electrical characteristics of each output port are consistent, ensuring the amplitude and phase consistency of the array unit excitation.

[0016] The reconfigurable pattern array antenna operates in the frequency band of 4.92-5.36 GHz and has two stable operating states: flat and 70° folded.

[0017] The resonant frequency in the flat state is 5.17 GHz, the relative bandwidth is 7.93%, it exhibits wide-beam omnidirectional radiation characteristics, and the peak gain is 1.67 dBi;

[0018] The resonant frequency at 70° fold is 5.14 GHz, and the peak gain is 6.74 dBi.

[0019] The two arms of the excitation element of the microstrip Yagi radiating array are printed on the upper and lower surfaces of the upper substrate (S1), respectively. The arm located on the lower surface of the upper substrate (S1) is directly electrically connected to an irregular metal ground plane printed on the lower surface of the upper substrate (S1). By utilizing the mirror current characteristics of this metal ground plane, the currents of the two arms of the excitation element are reversed. This structural design eliminates the complex balun structure required by traditional microstrip antennas, simplifying the overall antenna structure while significantly reducing feed insertion loss and effectively improving the antenna's radiation efficiency.

[0020] This invention discloses a pattern reconfigurable array antenna based on 4D printing. PLMC is used as the guiding element material, and its thermal response shape memory effect is utilized to achieve pattern reconfiguration without the need for additional control circuitry. This solves the problems of high loss, limited tuning, and insufficient mechanical stability in existing reconfigurable antennas. Simultaneously, the three-substrate layered structure and optimized feed network balance the antenna's flexibility, miniaturization, and electrical performance stability, expanding the application scenarios of intelligent biomedical materials in communication devices. This provides a new path for the miniaturized and multifunctional antenna design of modern communication systems and has significant engineering application value. Attached Figure Description

[0021] Figure 1 This is a top view of the antenna structure provided in an embodiment of the present invention; it shows the distribution of the microstrip Yagi radiating element, the irregular metal ground plane, and the peripheral PLMC guide element on the surface of the upper substrate (S1), and labels the names of key components; wherein, 1 is the microstrip Yagi radiating element; 2 is the peripheral guide element; and 3 is the irregular metal ground plane;

[0022] Figure 2 The exploded view of the antenna structure provided in the embodiment of the present invention shows the stacking relationship of the upper substrate (S1), the middle substrate (S2), and the lower substrate (S3) in layers, and clarifies the connection position of the coaxial line to the antenna element and the uniform distribution of the six through holes.

[0023] Figure 3 This is a schematic diagram of the power supply network structure provided in an embodiment of the present invention; a six-channel equal-phase output network with a 1-to-3 disc-type Luzzato power divider as its core is drawn, with the locations of the input ports, three intermediate cascade ports, six final output ports, and isolation resistors marked, demonstrating the ring-symmetrical circuit layout characteristics. Wherein, 4 is the input port; 5 is the cascade port; 6 is the 100... Isolation resistor; 7 is the output port; 8 is 150Ω. Isolation resistor;

[0024] Figure 4 The antenna electrical performance return loss curve provided in the embodiment of the present invention is shown in the figure. The horizontal axis is the frequency (unit: GHz) and the vertical axis is the return loss (unit: dB). The two curves are labeled "flat state" and "70° folded state" respectively, which show the frequency response characteristics under different states.

[0025] Figure 5 The three-dimensional radiation pattern of the antenna in the flat state provided in the embodiment of the present invention is marked with a peak gain of 1.67 dBi, which reflects the morphological characteristics of wide beam omnidirectional radiation.

[0026] Figure 6 The three-dimensional radiation pattern of the antenna in a 70° folded state provided in the embodiment of the present invention is marked with a peak gain of 6.74 dBi, showing the structural characteristics of directional beam convergence;

[0027] Figure 7 It is a two-dimensional radiation pattern (covering the beam distribution characteristics of two states), which intuitively presents the difference between omnidirectional and directional radiation. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a pattern reconfigurable array antenna based on 4D printing, such as... Figure 1 , Figure 2 As shown, the proposed antenna has a three-layer structure, including an upper substrate (S1), a middle substrate (S2), and a lower substrate (S3). The upper substrate (S1) houses a microstrip Yagi radiating element, an irregular metal ground plane, and peripheral directional elements. The lower substrate (S3) houses a feed network, which is coaxially connected to the antenna elements. Six coaxial mounting vias are coaxially formed on the upper substrate, middle substrate, lower substrate, and corresponding printed metal ground planes. These vias are used to pass through the coaxial line connecting the feed network of the lower substrate to the microstrip Yagi radiating element of the upper substrate. The inner walls of the vias are insulated to prevent electrical contact between the irregular metal ground plane of the upper substrate, the metal ground plane of the feed network of the lower substrate, and the outer conductor of the coaxial line, thus eliminating the risk of short circuits. By triggering the shape memory effect of the PLMC through thermal response, the antenna achieves a "flat-to-70° folding" structural switch, thereby completing the radiation pattern reconstruction.

[0030] In one embodiment of the present invention, the material used to guide the oscillator around the upper substrate (S1) is shape memory polylactic acid-trimethylene carbonate (PLMC). PLMC is prepared by ring-opening polymerization of two monomers, racemic lactide (DLLA) and trimethylene carbonate (TMC). It has both shape memory effect and biocompatibility. The mechanical properties, degradation rate and glass transition temperature (Tg) can be controlled by adjusting the ratio of the two comonomers. It does not require complex chemical crosslinking. The shape memory effect can be achieved through the physical entanglement of molecular chains. The shape memory cycle process is as follows: the PLMC with the initial flat shape is guided to the oscillator and heated to above Tg to soften it. Under the action of external force, it is folded to 70° to form a temporary shape. Then, the external force is maintained and the temperature is cooled. After the external force is removed, the temporary shape is fixed and the strain energy is stored. Finally, it is heated to above Tg again, the strain energy is released, and the material returns to the initial flat shape.

[0031] In one embodiment of the present invention, the upper substrate (S1) and the intermediate substrate (S2) adopt a dielectric constant. Loss tangent The F4BM220 material is used, which has low loss and good flexibility, ensuring both the antenna's radiation performance and flexibility requirements; the lower substrate (S3) uses a dielectric constant... Loss tangent The FR4 material possesses excellent mechanical strength and electrical properties, making it suitable for the deployment requirements of the power supply network. The main substrate of the upper substrate (S1) and the peripheral guide oscillator are fabricated using an integrated 4D printing process. The F4BM220 material of the main substrate and the PLMC material of the guide oscillator are seamlessly bonded during the printing process, ensuring both the integrity of the antenna structure and the ability to achieve differentiated material performance design for different functional areas.

[0032] like Figure 3 The diagram shows a power supply network structure provided in an embodiment of the present invention. The power supply network is centered on a 1-to-3 disc-type Luzzato power divider, with each of the three output ports cascaded with a Wilkinson power divider, forming a six-way equal-phase output network. The Luzzato power divider successfully solves the problem that the isolation resistors of the three Wilkinson power dividers cannot be simultaneously arranged in a plane, thereby significantly optimizing the circuit layout without sacrificing the isolation performance of the devices. Furthermore, due to its ring-shaped symmetrical structure, the output ports have good amplitude and phase consistency, which can ensure the amplitude and phase uniformity of the array unit excitation, thereby improving the radiation performance of the antenna.

[0033] In one embodiment of the present invention, the two arms of the excitation oscillator of the microstrip Yagi radiating element are printed on the upper and lower surfaces of the upper substrate (S1), respectively. The arm located on the lower surface of the upper substrate (S1) is directly electrically connected to the irregular metal ground plane printed on the lower surface of the upper substrate (S1). By utilizing the mirror current characteristics of the metal ground plane, the currents of the two arms of the excitation oscillator are reversed, eliminating the complex balun structure, simplifying the antenna structure, reducing the insertion loss of the antenna, and improving the radiation performance.

[0034] like Figure 4 The figure shows the return loss curves of the antenna under two states provided in the embodiment of the present invention. Figure 5 , Figure 6 and Figure 7 The two-dimensional and three-dimensional radiation patterns are shown for two states. Simulation results show that the antenna operates in the 4.92-5.36 GHz frequency band and maintains stable electrical performance in both states: In the flat state, the resonant frequency is 5.17 GHz, the operating frequency band covers 4.955-5.364 GHz, the relative bandwidth is 7.93%, the three-dimensional radiation pattern is relatively loose, the spatial extension range of the beam is wide, exhibiting wide-beam omnidirectional radiation characteristics, and the peak gain is 1.67 dBi; In the 70° folded state, the resonant frequency is 5.14 GHz, the frequency band is 4.92-5.33 GHz, the radiation pattern shape is significantly contracted, the directional focusing capability is significantly enhanced, the peak gain is increased to 6.74 dBi, and the effective switching of the radiation pattern is successfully achieved.

[0035] The antenna of this invention controls the direction of the directional vibrator element by changing the external temperature, achieving the conversion between omnidirectional and directional radiation. First, the antenna in its initial shape is heated to above the glass transition temperature Tg to soften it, and then deformed into a temporary shape under external force. Subsequently, the external force is maintained while the temperature is cooled down, and after the external force is removed, the temporary shape is fixed, while storing strain energy. Finally, it is heated again to above the glass transition temperature Tg, the strain energy is released, and the material returns to its original shape.

[0036] To verify the antenna's practicality, key parameters such as return loss, radiation pattern, and peak gain were simulated using HFSS electromagnetic simulation software. The simulation results show that the antenna exhibits stable electrical performance in both operating states, with low loss, gain meeting design requirements, excellent flexibility and mechanical stability, and pattern reconfiguration without additional control circuitry, making it suitable for the communication needs of the Internet of Things (IoT), 5G, and smart wearable devices. To further demonstrate the performance advantages of this antenna, a comparison of key parameters between this invention and existing mainstream reconfigurable antenna solutions is shown in Table 1.

[0037] Table 1. Comparison of key parameters between the present invention and existing mainstream reconfigurable antenna solutions.

[0038] As shown in Table 1, compared with the existing mainstream reconfigurable antenna solutions, the present invention achieves stable pattern reconstruction and a significant increase in gain without the need for additional control circuitry. It also has the core advantages of low loss, high flexibility, simple structure, and low cost, perfectly meeting the needs of modern wireless communication equipment for miniaturized, flexible, and multifunctional integrated antennas.

[0039] The core innovation of this invention lies in using PLMC material as a directional oscillator and utilizing its thermal response shape memory effect to achieve pattern reconstruction, which solves the problems of high loss, limited tuning, and insufficient mechanical stability of existing reconfigurable antennas. At the same time, the structural design and feeding network of the antenna are optimized, taking into account the flexibility, miniaturization and electrical performance stability of the antenna, and expanding the application scenarios of smart biomedical materials in the field of communication devices.

[0040] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0041] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are only intended to aid in understanding the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A pattern reconfigurable array antenna based on 4D printing, characterized in that, The system includes an upper substrate, a middle substrate, and a lower substrate. The upper substrate is provided with a microstrip Yagi radiating array element, an irregular metal ground plane, and a peripheral guide oscillator. The lower substrate is provided with a feed network. Six coaxial mounting through holes are correspondingly opened on the upper substrate, the middle substrate, the lower substrate, and the corresponding metal ground plane. The through holes are used to pass through coaxial lines connecting the feed network and the radiating array element. The inner walls of the through holes are insulated to prevent electrical contact between the irregular metal ground plane of the upper substrate, the metal ground plane of the feed network of the lower substrate, and the outer conductor of the coaxial lines. The outer periphery of the upper substrate is made of PLMC material. Its shape memory effect is triggered by thermal response to realize the antenna's "flat-70° folding" structural switching, thereby completing the pattern reconstruction.

2. The pattern reconfigurable array antenna based on 4D printing according to claim 1, characterized in that, The PLMC used to guide the oscillator around the upper substrate is prepared by ring-opening polymerization of two monomers, racemic lactide and trimethylene carbonate, which has both shape memory effect and biocompatibility. The mechanical properties, degradation rate and glass transition temperature are controlled by adjusting the ratio of the two comonomers to achieve the shape memory effect.

3. The pattern reconfigurable array antenna based on 4D printing according to claim 1, characterized in that, The dielectric substrate portion of the upper substrate that carries the microstrip Yagi radiating array elements and the irregular metallic ground plane, as well as the intermediate substrate, all adopt a relative permittivity. Loss tangent The material is F4BM220; the lower substrate uses a material with a relative permittivity of 100%. Loss tangent FR4 material.

4. The pattern reconfigurable array antenna based on 4D printing according to claim 1, characterized in that, The power supply network is based on a Luzzato power divider with a 1-to-3 disc shape. Each of the three output ports is cascaded with a Wilkinson power divider to form a six-way equal-phase output network. The electrical characteristics of each output port are consistent, ensuring the amplitude and phase consistency of the array unit excitation.

5. The pattern reconfigurable array antenna based on 4D printing according to claim 1, characterized in that, The reconfigurable pattern array antenna operates in the frequency band of 4.92-5.36 GHz and has two stable operating states: flat and 70° folded. The resonant frequency in the flat state is 5.17 GHz, the operating frequency band covers 4.955-5.364 GHz, the relative bandwidth is 7.93%, it exhibits wide beam omnidirectional radiation characteristics, and the peak gain is 1.67 dBi; The resonant frequency in the 70° folded state is 5.14 GHz, the operating frequency band covers 4.92-5.33 GHz, the relative bandwidth is 7.98%, it exhibits directional high-gain radiation characteristics, and the peak gain is 6.74 dBi.

6. The pattern reconfigurable array antenna based on 4D printing according to claim 1, characterized in that, The two arms of the excitation oscillator of the microstrip Yagi radiation array are located on the upper and lower surfaces of the upper substrate, respectively. The arm located on the lower surface of the upper substrate is directly electrically connected to an irregular metal ground plane printed on the lower surface of the upper substrate. By utilizing the mirror current characteristics of the metal ground plane, the currents of the two arms of the excitation oscillator are reversed.

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