A polarization-insensitive electromagnetic rectifying surface

Abstract

The present invention discloses a polarization-insensitive electromagnetic rectifying surface, which solves the problems that the efficiency of the rectifying surface is easily affected by the polarization direction of the incident electromagnetic wave, the matching and DC synthesis circuits are complex, and the energy loss is relatively large. The upper surface of the dielectric substrate (2) of the rectifying surface includes m rows and n columns of rectifying surface units (1) with the same size and shape, where m and n are positive integers greater than or equal to 2, and an output filter circuit (4). The lower surface of the dielectric substrate (2) is covered by a metal ground (3), and the lower surface includes pads (14) with metallized vias (13) and Schottky diodes (15); each rectifying surface unit (1) includes 1 energy receiving unit (11), 4 microstrip lines (12), 4 metallized vias (13), 4 pads (14) located on the lower surface, and 4 Schottky diodes (15). The present invention has the advantages of being insensitive to the polarization direction of the incident wave, having a simple structure, and high rectifying efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave radio frequency devices, and particularly relates to a polarization-insensitive electromagnetic rectifying surface in microwave radio frequency devices. Background Art

[0002] An electromagnetic rectifying surface can capture spatial electromagnetic energy in a specific frequency range and convert it into direct current electrical energy by loading Schottky diodes in a periodic electromagnetic structure, and has broad application prospects in long-distance wireless power transmission systems and wireless energy harvesting systems. For example, in the event of natural disasters such as earthquakes and snowstorms, where power is interrupted in the affected areas, the use of an electromagnetic rectifying surface can quickly meet the power consumption needs of the victims and achieve emergency power supply, providing guarantee for timely rescue and the lives of the victims. Another example is that, without undersea cables, the electromagnetic rectifying surface can directly transmit the electrical energy generated by offshore wind power to the land, which not only extends the service life of the wind power generation equipment but also reduces the cost of undersea cabling. In addition, with the wide spread of electric vehicles, the electromagnetic rectifying surface can make long-distance wireless automatic charging of electric vehicles possible, which can not only solve the cumbersome process of plugging and unplugging the power cord at a fixed power source during charging of electric vehicles, but also help alleviate the problem of insufficient number of electric vehicle charging piles, facilitate the further popularization of electric vehicles, and promote the development of green cities and green transportation.

[0003] The literature "Designing an efficient rectifying cut-wire metasurface for electromagnetic energy harvesting" published in the journal Applied Physics Letters in 2017 proposed a rectifying metasurface based on a cut-wire structure. This metasurface can achieve the collection and rectification of electromagnetic energy at a working frequency of 6.75 GHz. However, its structural characteristics determine that this rectifying surface can only receive electromagnetic wave energy in a single polarization direction, and the energy capture efficiency is extremely susceptible to the polarization direction of spatial electromagnetic waves. Once there is polarization mismatch, its working efficiency will rapidly decrease, greatly limiting the application of this rectifying surface. In the same year, the literature "A metasurface for conversion of electromagnetic radiation to DC" published in the journal Applied Physics Letters proposed a rectifying metasurface operating at 3 GHz. Although this rectifying surface is insensitive to the polarization direction of incident electromagnetic waves, its matching network is relatively complex, resulting in relatively large losses, reducing the efficiency, and the processing cost of the multi-layer structure is also relatively high.

[0004] In summary, the main problems faced by the current electromagnetic rectifying surface are how to make the electromagnetic rectifying surface insensitive to the polarization direction of the incident wave, how to simplify the matching circuit between the energy receiving unit and the rectifying part, reduce the loss of the rectifying surface, and improve the efficiency of the rectifying surface. Summary of the Invention

[0005] The object of the present invention is to propose a polarization-insensitive electromagnetic rectifying surface, which overcomes the shortcomings of the existing rectifying surface being easily affected by the polarization of the incident wave and the complex circuit structure, and solves the problem of low efficiency of the existing rectifying surface.

[0006] The technical solution of the present invention is as follows: The upper surface of the dielectric substrate 2 includes m rows and n columns of rectifying surface units 1 with the same size and shape, where m and n are positive integers greater than or equal to 2, and an output filter circuit 4. The lower surface of the dielectric substrate 2 is covered by a metal ground 3, and the lower surface includes pads 14 with metallized vias 13 and Schottky diodes 15. Each rectifying surface unit 1 includes 1 energy receiving unit 11, 4 microstrip lines 12, 4 metallized vias 13, 4 pads 14 located on the lower surface, and 4 Schottky diodes 15. The rectifying surface unit 1 is square. The energy receiving unit 11 is located at the center of the rectifying surface unit 1 and has a cross-shaped symmetric structure, with the lateral and longitudinal lengths both less than the side length of the rectifying surface unit 1. The 4 microstrip lines 12 have equal length and width and are distributed in an X shape, located on the two diagonals of the rectifying surface unit 1 respectively, with one end connected to the corners of the energy receiving unit 11 and the other end connected to the four vertices of the rectifying surface unit 1. The 4 metallized vias 13 are respectively located on the 4 arms of the energy receiving unit 11, distributed in a symmetric structure, with the upper ends connected to the 4 arms of the energy receiving unit 11 and the lower ends respectively connected to the 4 pads 14. The pads 14 are formed by etching a square ring 16 on the metal ground 3, with the center connected to the upper surface metal of the energy receiving unit 11 through the metallized via 13 and the other end connected to the anode of the Schottky diode 15. The 4 Schottky diodes 15 are symmetrically distributed with respect to the rectifying surface unit 1, with the anodes connected to the pads 14 and the cathodes connected to the metal ground 3. The output filter circuit 4 is composed of a chip inductor 41, a chip capacitor 42, and a grounded metallized via 43, connecting the output port 5 and the microstrip line 12. Among them, one end of the chip inductor 41 is connected to the microstrip line 12 near the edge of the edge rectifying surface unit 1, and the other end is connected to the output port 5. The two ends of the chip capacitor 42 are respectively connected to the output port 5 and the grounded metallized via 43, and the 4 grounded metallized vias 43 are arranged longitudinally at equal intervals. Each rectifying surface unit 1 is respectively connected to 4 adjacent rectifying surface units 1 on its upper left, lower left, upper right, and lower right through the 4 microstrip lines 12 at the four corners, and the adjacent rectifying surface units 1 on the left and right and above and below are not connected. The principle of the technical solution of the present invention is as follows: By reasonably designing the size of the energy receiving unit 11, the electromagnetic wave energy of a specific frequency in space can be captured. Due to the symmetric structure of the rectifying surface, it is not sensitive to the polarization direction of the incident electromagnetic wave. The captured electromagnetic wave energy enters the Schottky diode 15 through the metal via 13 and the pad 14 and is converted into DC energy. By adjusting the position of the metallized via 13 relative to the energy receiving unit 11, the impedance matching between the Schottky diode 15 and the energy receiving unit 11 can be achieved. The microstrip line 12 conducts the DC energy, and finally a relatively pure DC energy is obtained by the output filter circuit 4. Each rectifying surface unit 1 includes 4 Schottky diodes 15, and its power capacity is larger than that of a rectifying surface unit with a single Schottky diode.

[0007] Advantages and beneficial effects of the present invention:

[0008] The electromagnetic rectifying surface proposed by the present invention adopts a symmetric geometric structure to receive electromagnetic waves in space, making the rectifying surface insensitive to the polarization direction of incident electromagnetic waves, and maintaining a high energy capture efficiency for electromagnetic waves of various polarization directions. Matching the Schottky diode directly with the energy receiving unit simplifies the matching circuit structure and is beneficial to improving the energy conversion efficiency. The energy receiving unit and the DC synthesis network are on the same layer, with a simpler structure and reduced circuit cost. The use of a multi-diode structure increases the power capacity of the rectifying surface. Description of the drawings

[0009] Figure 1 is the front pattern of the rectifying surface of the present invention

[0010] Figure 2 is the back pattern of the rectifying surface of the present invention

[0011] Figure 3 is the front pattern of the rectifying surface unit of the present invention

[0012] Figure 4 is the back pattern of the rectifying surface unit of the present invention

[0013] Figure 5 is the simulation result diagram of the energy capture efficiency of the rectifying surface unit

[0014] Figure 6 is the simulation result diagram of the energy conversion efficiency and output voltage of the rectifying surface unit varying with the input power Detailed implementation manners

[0015] The following further describes the present invention in conjunction with the drawings and specific embodiments: As Figure 1 shown, the upper surface of the dielectric substrate 2 includes m rows and n columns of rectifying surface units 1 with the same size and shape, where m and n are positive integers greater than or equal to 2, and an output filter circuit 4. As Figure 2 shown, the lower surface of the dielectric substrate 2 is covered by a metal ground 3, and the lower surface includes pads 14 with metallized vias 13 and Schottky diodes 15. As Figure 3 and Figure 4As shown in the figure, each rectifying surface unit 1 includes an energy receiving unit 11, four microstrip lines 12, four metallized vias 13, four pads 14 located on the lower surface, and four Schottky diodes 15; the rectifying surface unit 1 is square; the energy receiving unit 11 is located at the center of the rectifying surface unit 1 and has a cross-shaped symmetric structure, with the transverse and longitudinal lengths both smaller than the side length of the rectifying surface unit 1; the four microstrip lines 12 are equal in length and width and are distributed in an X shape, respectively located on the two diagonals of the rectifying surface unit 1, with one end connected to the corners of the energy receiving unit 11 and the other end connected to the four vertices of the rectifying surface unit 1; the four metallized vias 13 are respectively located on the four arms of the energy receiving unit 11 and are symmetrically distributed, with the upper ends connected to the four arms of the energy receiving unit 11 and the lower ends respectively connected to the four pads 14; the pads 14 are formed by etching a square ring 16 on the metal ground 3, with the center connected to the upper surface metal of the energy receiving unit 11 through the metallized via 13 and the other end connected to the anode of the Schottky diode 15; the four Schottky diodes 15 are symmetrically distributed with respect to the rectifying surface unit 1, with the anodes connected to the pads 14 and the cathodes connected to the metal ground 3; the output filter circuit 4 is composed of a chip inductor 41, a chip capacitor 42, and a grounded metallized via 43, and is connected to the output port 5 and the microstrip line 12; among them, one end of the chip inductor 41 is connected to the microstrip line 12 near the edge of the edge rectifying surface unit 1, and the other end is connected to the output port 5, both ends of the chip capacitor 42 are respectively connected to the output port 5 and the grounded metallized via 43, and the four grounded metallized vias 43 are arranged longitudinally at equal intervals; each rectifying surface unit 1 is respectively connected to the four adjacent rectifying surface units 1 above, below, left, and right of it through the four corner microstrip lines 12, and there is no connection between the adjacent rectifying surface units 1 on the left and right and above and below.

[0016] To further illustrate the feasibility of the above technical solution, the following gives its specific design example. For the polarization-insensitive electromagnetic rectifying surface, the dielectric substrate uses an F4B substrate with a thickness of 0.8 mm and a relative dielectric constant of 2.6, the Schottky diode is BAT15-03W, the DC output inductor is 12 nH, and the capacitor is 47 pF. The rectifying surface is distributed with 5 rows and 5 columns of rectifying surface units, and the DC output adopts a parallel form. The rectifying surface operates at 2.45 GHz, and the DC output terminal is connected to a 20-ohm load. When uniform plane electromagnetic waves with different polarization directions irradiate the rectifying surface, the energy capture efficiency of the rectifying surface for the electromagnetic waves is as Figure 5 shown. It can be seen that even when the polarization direction of the incident wave is changing, the rectifying surface can still maintain a high energy capture efficiency at 2.45 GHz. The simulation results show that theoretically, the maximum energy capture efficiency of the rectifying surface can reach 100%, and in the range of 2.425 GHz - 2.478 GHz, the absorption efficiency is above 50%. The simulation curves of the energy conversion efficiency of a single rectifying surface unit and the output DC voltage are asFigure 6 As shown, when the input power is 13.5 dBm, the maximum energy conversion efficiency can reach 80.7%, and the output DC voltage is 3.17 V, that is, a single unit can output 16.5 mW of DC power under a 20.4 mW RF input power. It can be seen therefrom that the entire rectifying surface can output 412.5 mW of DC output power.

Claims

1. A polarization-insensitive electromagnetic rectifying surface, characterized in that: The upper surface of the dielectric substrate (2) includes m rows and n columns of rectifying surface units (1) with the same size and shape, where m and n are positive integers greater than or equal to 2, and an output filter circuit (4). The lower surface of the dielectric substrate (2) is covered by a metal ground (3), and the lower surface includes pads (14) with metallized vias (13) and Schottky diodes (15); each rectifying surface unit (1) includes 1 energy receiving unit (11), 4 microstrip lines (12), 4 metallized vias (13), 4 pads (14) located on the lower surface, and 4 Schottky diodes (15); the rectifying surface unit (1) is square; the energy receiving unit (11) is located at the center of the rectifying surface unit (1), has a cross-shaped symmetric structure, and the lateral and longitudinal lengths are both less than the side length of the rectifying surface unit (1); the 4 microstrip lines (12) have equal length and width, are distributed in an X shape, are respectively located on the two diagonals of the rectifying surface unit (1), one end is connected to the corner of the energy receiving unit (11), and the other end is connected to the four vertices of the rectifying surface unit (1); the 4 metallized vias (13) are respectively located on the 4 arms of the energy receiving unit (11), are symmetrically distributed, the upper ends are connected to the 4 arms of the energy receiving unit (11), and the lower ends are respectively connected to 4 pads (14); the pads (14) are formed by etching a square ring (16) on the metal ground (3), the center is connected to the upper surface metal of the energy receiving unit (11) through a metallized via (13), and the other end is connected to the anode of the Schottky diode (15); the 4 Schottky diodes (15) are symmetrically distributed with respect to the rectifying surface unit (1), the anodes are connected to the pads (14), and the cathodes are connected to the metal ground (3); the output filter circuit (4) is composed of a chip inductor (41), a chip capacitor (42) and a grounded metallized via (43), and is connected to the output port (5) and the microstrip line (12); among them, one end of the chip inductor (41) is connected to the microstrip line (12) near the edge of the edge rectifying surface unit (1), the other end is connected to the output port (5), the two ends of the chip capacitor (42) are respectively connected to the output port (5) and the grounded metallized via (43), and the 4 grounded metallized vias (43) are arranged longitudinally at equal intervals; each rectifying surface unit (1) is connected to 4 adjacent rectifying surface units (1) above, below, left, and right through the microstrip lines (12) at the four corners, and the adjacent rectifying surface units (1) on the left and right and above and below are not connected.

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