A high-efficiency omni-directional rectenna based on class-f harmonic rejection structure

Abstract

The application discloses a high-efficiency omnidirectional rectenna based on a class-F harmonic suppression structure and belongs to the rectenna field, comprising: a plurality of rectenna units which are arranged at equal intervals and rotate around the same center and are used for receiving radio frequency energy; the rectenna unit comprises a receiving antenna and a rectifier circuit; the receiving antenna comprises an antenna radiation structure, a metal floor and a feed microstrip line; a U-shaped groove is arranged on a region of the antenna radiation structure which is close to the metal floor, and a rectangular groove is arranged in the U-shaped groove; the U-shaped groove and the rectangular groove are used for suppressing the radiation of the second harmonic and the third harmonic; the rectifier circuit is arranged on the upper surface of a PCB and is used for rectifying the output signal of the antenna radiation structure by the microstrip line and electronic components; and the plurality of rectenna units are connected through a direct current synthesis network, so that the size of the rectenna can be reduced and the efficiency of the rectenna can be improved.

Description

Technical Field

[0001] This invention belongs to the field of microwave rectifier antenna technology, and particularly relates to a high-efficiency omnidirectional rectifier antenna based on a Class F harmonic suppression structure. Background Technology

[0002] In the rapid development of modern technology, the contradiction between energy demand and supply is becoming increasingly prominent. On the one hand, with the widespread application of many emerging technologies such as the Internet of Things (IoT), wireless sensor networks (WSN), and wearable devices, the number of devices is growing exponentially, leading to increasingly diversified and decentralized energy demands.

[0003] In recent years, microwave wireless power transmission has gradually shifted from high-power to low-power transmission, relying on antennas as a carrier for power transfer. Compared to the magnetic resonant coupling method commonly used in high-power transmission, using antennas reduces the size of the transmission carrier and facilitates integration with other devices. Furthermore, antenna design offers greater flexibility and allows for integration with rectifier circuits to form rectifier antennas, making it a more valuable research subject.

[0004] With the continuous and in-depth research into wireless communication technology, not only is the ambient microwave energy density gradually increasing, but the power consumption of components such as sensors in wireless sensing nodes is also gradually decreasing. This makes it possible to collect this energy to power low-power sensors. Compared with traditional power supply methods (cable connection or battery use), collecting microwave energy for power supply greatly reduces dependence on the power supply environment and also reduces the cost of manual power supply maintenance. It is a research direction with high potential and high economic benefits.

[0005] As the most critical component of the receiver in a microwave energy harvesting system, the rectifier antenna's role is to convert the microwave energy emitted by the transmitting antenna into a DC voltage output. Its core module comprises two parts: the receiving antenna and the rectifier circuit. The receiving antenna is responsible for receiving radio frequency (RF) energy from the environment, while the rectifier current is responsible for rectifying the received RF energy into a DC voltage output. Typically, the receiving antenna's efficiency can reach over 90%, therefore, the efficiency of the rectifier antenna is largely determined by the rectification efficiency of the rectifier circuit.

[0006] The rectification efficiency of a rectifier circuit is generally determined by the following two aspects: First, impedance matching plays a decisive role in the performance parameters of a rectifier circuit. Poor impedance matching design will cause a large amount of radio frequency energy input to the rectifier circuit to be reflected, thus significantly reducing the circuit's energy conversion efficiency. It is worth noting that research in this area in academia and engineering has reached a mature stage. Researchers, through theoretical modeling and simulation optimization, have designed circuits that can mostly achieve high levels of impedance matching performance, laying a solid foundation for improving rectification efficiency. Second, in the study of loss mechanisms in rectifier circuits, nonlinear losses of rectifier devices dominate. Rectifier elements, typically represented by Schottky diodes, exhibit significant power dissipation characteristics during energy conversion in the microwave and millimeter-wave frequency bands. This loss mainly originates from the radiation of high-order harmonic components induced by the nonlinear junction capacitance and charge transport characteristics within the device, as well as conduction losses generated by the on-state voltage drop and reverse recovery current.

[0007] To improve the efficiency of rectifier antennas, many scholars both domestically and internationally have conducted extensive research. In 2014, in the paper "J. Guo, H. Zhang, and X. Zhu, 'Theoretical analysis of RF-DC conversion efficiency for class-F rectifiers,' IEEE Trans. Microw. Theory Techn., vol. 62, no. 4, pp. 977–985, Apr. 2014," J. Guo et al. introduced harmonic suppression technology, commonly used in power amplifiers, into the design of rectifier circuits. Its working principle is to short-circuit the circuit during even harmonics and keep it open during odd harmonics, suppressing harmonics and reshaping the current and voltage waveforms, thereby improving the overall rectification efficiency. Through theoretical analysis, simulation, and physical verification, the results show that the overall efficiency of the rectifier circuit using the class-F structure is more than 5% higher than that of the circuit without the class-F structure. However, traditional Class-F rectifier circuits typically require the introduction of open or short-circuit stubs of different electrical lengths. Although the efficiency of the rectifier circuit is improved, the system complexity and size are increased.

[0008] In modern radio frequency (RF) environments, there are numerous and widely distributed RF signal sources, such as wireless communication base stations, Wi-Fi routers, and broadcast television towers, each emitting signals with different directions and frequencies. To avoid directional antennas missing some RF energy due to pointing issues, the paper "M. Kumar, S. Kumar A, and A. Sharma, 'Planar Orbicular Rectenna Array System With 3-D Uniform Coverage for Wireless Powering of IoT Nodes'", IEEE Trans. Microw. Theory Techn., vol. 71, no. 3, pp. 1366–1373, Mar. 2023., utilizes multiple end-fire antennas arranged in a ring to form an antenna array, achieving omnidirectional reception of RF energy. Simultaneously, by combining the antenna and rectifier antenna, and based on complex conjugate matching theory, direct matching between the antenna output impedance and the rectifier circuit input impedance is achieved, thus avoiding the introduction of additional matching circuits in traditional rectifier circuits and significantly reducing the complexity and size of the rectifier antenna system. However, the size and layout of its rectifier antenna make it difficult to further improve the efficiency of the rectifier antenna by introducing methods such as harmonic suppression structures. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention proposes a high-efficiency omnidirectional rectifier antenna based on a Class-F harmonic suppression structure, thereby resolving the issues present in the prior art.

[0010] To achieve the above objectives, the present invention provides a high-efficiency omnidirectional rectifier antenna based on a class-F harmonic suppression structure, comprising:

[0011] Several rectifier antenna units are rotated around the same center and distributed at equal intervals. The rectifier antennas are used to receive radio frequency energy. The rectifier antennas are disposed on the surface of a double-layer PCB board. The rectifier antenna unit includes a receiving antenna and a rectifier circuit.

[0012] The receiving antenna includes an antenna radiating structure, a metal ground plane, and a feed microstrip line; wherein the antenna radiating structure and the metal ground plane are disposed on the lower surface of the PCB board, and the feed microstrip line is disposed on the upper surface of the PCB board.

[0013] The antenna radiating structure has a U-shaped groove near the metal floor, and a rectangular groove is provided inside the U-shaped groove; the U-shaped groove and the rectangular groove are used to suppress the radiation of the second and third harmonics;

[0014] The rectifier circuit is disposed on the upper surface of the PCB board. The rectifier circuit includes a first microstrip line, a second microstrip line and a third microstrip line, wherein the first microstrip line is connected to the power supply microstrip line, the first microstrip line and the second microstrip line are connected through a diode, and the first microstrip line and the third microstrip line are connected through an inductor.

[0015] Several rectifier antenna units are connected by a DC combining network, which includes several microstrip lines and circular metal patches connected to the microstrip lines; wherein the microstrip lines are connected to a third microstrip line, and the circular metal patches are disposed at the rotation center of the rectifier antenna units.

[0016] Optionally, the metal ground planes of all the rectifier antenna units form a polygonal shape, and a circular gap is provided at the center of the rotation of the metal ground planes. The number of rectifier antenna units corresponds to the polygonal shape formed by the metal ground planes of all the rectifier antenna units.

[0017] Optionally, the number of rectifier antenna elements is 5, and the metal ground planes of all the rectifier antenna elements form a pentagonal shape.

[0018] Optionally, the first microstrip line is a quarter-wavelength microstrip line.

[0019] Optionally, the antenna radiation structure is a rectangular metal patch, and a U-shaped groove is provided in the lower half of the rectangular metal patch, in the area close to the metal ground, with the axis of symmetry of the rectangular groove and the U-shaped groove coinciding.

[0020] Optionally, the operating frequency of the rectifier antenna is 2.45 GHz.

[0021] Optionally, the end of the third microstrip line furthest from the first microstrip line is connected to a metal ground plane via a metallized via.

[0022] Optionally, the first microstrip line is arranged parallel to the second microstrip line, and the first microstrip line is arranged perpendicular to the third microstrip line.

[0023] Optionally, the negative terminal of the diode is connected to the first microstrip line, and the positive terminal of the diode is connected to the second microstrip line.

[0024] Optionally, the optimal operating power is 3dBm.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] (1) In this invention, the receiving antenna is an end-fire antenna. By adjusting the structure of the receiving antenna, the antenna and the rectifier circuit can form a conjugate match, eliminating the need for an additional matching circuit, reducing the complexity of the rectifier antenna, and also helping to reduce the size of the rectifier antenna and improve the system integration.

[0027] (2) Compared to traditional Class-F rectifier circuits that introduce open or short-circuit stubs of different electrical lengths to achieve Class-F rectification, this invention combines the receiving antenna and rectifier circuit. A harmonic suppression structure is added to the radiation structure of the receiving antenna, making the impedance of the receiving antenna close to zero at the second and third harmonic frequencies. After impedance transformation via a quarter-wavelength microstrip line, the impedance at the diode connection is an open circuit for both the second and third harmonics, resulting in zero second harmonic voltage and zero third harmonic current generated by the diode. This reshapes the current and voltage waveforms, achieving Class-F rectification. While improving the efficiency of the rectifier antenna, this invention simplifies the rectifier circuit and makes its layout easier.

[0028] (3) The present invention arranges the designed rectifier antenna unit in a centrally symmetrical manner to obtain many radio frequency energy receiving angles and realize omnidirectional reception of radio frequency energy.

[0029] (4) The rectifier antenna for radio frequency energy harvesting of the present invention has strict design parameters and clear design steps.

[0030] (5) Compared with existing rectifier antennas, the present invention has a simpler structure and significantly improved efficiency. Attached Figure Description

[0031] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0032] Figure 1 This is a schematic diagram of a single rectifier antenna unit embodiment of the present invention;

[0033] Figure 2 The impedance simulation diagram of the receiving antenna of a single rectifier antenna unit in an embodiment of the present invention is shown.

[0034] Figure 3 This is a schematic diagram illustrating the principle of an embodiment of the present invention;

[0035] Figure 4 This is a current spectrum analysis diagram across the diode in an embodiment of the present invention;

[0036] Figure 5 This is a voltage spectrum analysis diagram across the diode in an embodiment of the present invention;

[0037] Figure 6 This is a physical diagram of a rectifier antenna embodiment of the present invention;

[0038] Figure 7The following are simulation results of the energy conversion efficiency of the rectifier antenna unit of this invention under different received powers at an operating frequency of 2.45 GHz, according to an embodiment of this invention.

[0039] Figure 8 The embodiment of the present invention operates at a frequency of 2.45 GHz and a received power density of 320 mW / m. 2 At that time, the test radiation pattern of the normalized DC voltage output by the rectifier antenna unit;

[0040] Figure 9 The embodiment of the present invention operates at a frequency of 2.45 GHz and a received power density of 320 mW / m. 2 The test radiation pattern is the normalized DC voltage output of the rectifier antenna omnidirectional array. Detailed Implementation

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0043] This invention discloses a high-efficiency omnidirectional rectifier antenna based on a Class F harmonic suppression structure; the circuit of the rectifier antenna unit and the antenna are printed on a double-layer PCB board. The metal ground plane and the antenna radiating structure are printed on the lower layer of the PCB board, while the antenna feed microstrip line, the microstrip structure of the rectifier circuit, the DC combining network, and other components are printed and soldered on the upper layer of the PCB board.

[0044] The antenna radiating structure, metal ground plane, and antenna feed microstrip line constitute the receiving antenna in the rectifier antenna. The microstrip structure and components of the rectifier circuit form the radio frequency rectification section, and the DC combining network is used to integrate the rectifier circuit, realizing the function of converting the received radio frequency energy into DC.

[0045] This invention, through joint design, enables direct conjugate matching between the receiving antenna and the rectifier circuit, eliminating the need for an additional matching circuit and reducing the complexity of the rectifier antenna. By adding two slots to the antenna's radiating structure, this invention suppresses the radiation of the second and third harmonics. The impedance at the second and third harmonic frequencies of the receiving antenna is close to a short circuit. After impedance transformation via a quarter-wavelength microstrip line, the impedance at the diode connection is a short circuit for the second harmonic and an open circuit for the third harmonic. This makes the second harmonic voltage and third harmonic current generated by the diode zero, reshaping the current and voltage waveforms. The voltage and current waveforms passing through the diode resemble a Class-F shape (the voltage waveform is similar to a square wave), reducing switching losses during diode rectification. This improves the overall rectification efficiency. Furthermore, this invention achieves omnidirectional reception of radio frequency energy by centrally symmetrically arranging the designed rectifier antenna unit.

[0046] The above technical solution is described in detail below:

[0047] This invention provides a high-efficiency omnidirectional rectifier antenna based on a Class F harmonic suppression structure.

[0048] This rectifier antenna consists of an end-fire antenna with second and third harmonic suppression and a Class-F rectifier circuit. The two are directly conjugate-matched, requiring no additional matching circuit. The impedance at the second and third harmonic frequencies of the receiving antenna is close to a short circuit. After impedance transformation via a quarter-wavelength microstrip line, the impedance at the diode connection is a second harmonic short circuit and a third harmonic open circuit. This ensures that the second harmonic voltage and third harmonic current generated by the diode are zero, reshaping the current and voltage waveforms. This results in a Class-F shaped voltage waveform (similar to a square wave), reducing switching losses during diode rectification and thus improving overall rectification efficiency. The five rectifier antenna elements are centrally symmetrical, achieving omnidirectional reception of radio frequency energy.

[0049] The circuitry and antenna of the rectifier antenna are printed on a double-layer PCB board. The metal ground plane and antenna radiating structure are printed on the lower layer of the PCB board, while the antenna feed microstrip line, DC combining network, microstrip structure of the rectifier circuit, and components are printed and soldered on the upper layer of the PCB board.

[0050] The rectifier antenna consists of five identical rectifier antenna elements, which are centrally symmetrically distributed on a pentagonal PCB board. Each rectifier antenna element includes a receiving antenna and a rectifier circuit.

[0051] The receiving antenna in the rectifier antenna unit consists of an antenna radiating structure, a metal ground plane, and an antenna feed microstrip line. The antenna radiating structure is a rectangular metal patch perpendicular to the antenna feed microstrip line and printed on the lower layer of the PCB board. A U-shaped slot and a rectangular slot are etched on the antenna radiating structure. The two slot structures are mirror-symmetrically distributed about the central axis of the antenna feed microstrip line. The distance between the U-shaped slot and the lower boundary of the radiating structure is G1, and the distance between the U-shaped slot and the lower boundary of the radiating structure is G2, which are used to suppress the radiation of the second and third harmonics.

[0052] The metal ground plane is a pentagon with a side length of L1. The antenna radiating structure consists of five rectangles, each with a length of L2 and a width of W1, arranged sequentially along the five sides of the pentagonal metal ground plane, separated from the ground plane by gaps of width S1. A U-shaped slot and a rectangular slot are etched on the left side of the antenna radiating structure. The long side of the U-shaped slot is L3, the short side is L4, and the width is W2. The rectangular slot is L5 long and W3 wide. The antenna's feed microstrip line, rectifier circuit microstrip structure, and components are composed of five identical, centrally symmetrical units. Within each unit, the feed microstrip line is L6 long and W4 wide.

[0053] The rectifier circuit in the rectifier antenna unit consists of a microstrip structure and surface-mount components. The microstrip structure and surface-mount components are printed and soldered onto the upper layer of a PCB board. The rectifier circuit unit comprises three microstrip lines, a diode, and an inductor. The first microstrip line is a quarter-wavelength microstrip line located at the right end of the antenna's feed microstrip line and parallel to it. The second microstrip line is parallel to the first microstrip line, and its end, the end furthest from the first microstrip line, is connected to a metal ground plane via a metal via. The cathode of the diode is connected to the first microstrip line, and the anode of the diode is connected to the second microstrip line. The third microstrip line is perpendicular to both the first and second microstrip lines. The inductor is connected between the first and third microstrip lines.

[0054] The rectifier antenna consists of five rectifier antenna elements with the above-described structure. These five elements are centrally and rotationally symmetrically distributed on the same PCB board, with each element responsible for receiving radio frequency energy in its corresponding direction. The upper middle section of the PCB board contains a DC combining network, which is composed of five microstrip lines connected to circular metal patches. This network connects to the DC output terminals of each rectifier antenna element, serving as the positive terminal for the overall DC output of the rectifier antenna. The metal ground plane serves as the negative terminal for the DC output.

[0055] The rectifier antenna operates at a frequency of 2.45 GHz, employs Class F harmonic suppression rectification, and enables omnidirectional reception of radio frequency energy. Its optimal input power is 3 dBm. This design method is applicable to the design of rectifier antennas in any microwave frequency band.

[0056] The beneficial effects of this invention are:

[0057] (1) In this invention, the receiving antenna is an end-fire antenna. By adjusting the structure of the receiving antenna, the antenna and the rectifier circuit can form a conjugate match, eliminating the need for an additional matching circuit, reducing the complexity of the rectifier antenna, and also helping to reduce the size of the rectifier antenna and improve the system integration.

[0058] (2) Compared to traditional Class-F rectifier circuits that introduce open or short-circuit stubs of different electrical lengths to achieve Class-F rectification, this invention combines the receiving antenna and rectifier circuit. A harmonic suppression structure is added to the radiation structure of the receiving antenna, making the impedance of the receiving antenna close to zero at the second and third harmonic frequencies. After impedance transformation via a quarter-wavelength first microstrip line, the impedance at the diode connection is an open circuit for both the second and third harmonics, resulting in zero second harmonic voltage and zero third harmonic current generated by the diode. This reshapes the current and voltage waveforms, achieving Class-F rectification. While improving the efficiency of the rectifier antenna, this invention simplifies the rectifier circuit and makes its layout easier.

[0059] (3) The present invention arranges the designed rectifier antenna unit in a centrally symmetrical manner to obtain many radio frequency energy receiving angles and realize omnidirectional reception of radio frequency energy.

[0060] (4) The rectifier antenna for radio frequency energy harvesting of the present invention has strict design parameters and clear design steps.

[0061] (5) Compared with existing rectifier antennas, the present invention has a simpler structure and significantly improved efficiency.

[0062] (6) This invention provides a detailed description of the rectifier antennas used and demonstrates their working principle.

[0063] The above technical solution will be described in detail with reference to the accompanying drawings and related data:

[0064] like Figure 1 As shown, this invention proposes a high-efficiency omnidirectional rectifier antenna unit based on a Class F harmonic suppression structure. The circuitry and antenna of the rectifier antenna unit are printed on a double-layer PCB board. The metal ground plane and antenna radiating structure are printed on the lower layer of the PCB board, while the antenna feed microstrip line, DC combining network, microstrip structure of the rectifier circuit, and components are printed and soldered on the upper layer of the PCB board. The antenna radiating structure is rectangular with a length L2 = 34.35 mm and a width W1 = 5.25 mm. A gap of S1 = 1 mm separates the antenna radiating structure from the edge of the metal ground plane.

[0065] The present invention further adds a "U" shaped slot to the rectangular radiating structure, which can effectively suppress the radiation of the second harmonic by the antenna, so that the impedance of the antenna at the second harmonic frequency is close to zero. The harmonics generated in the rectifier circuit can be reflected back to the circuit for re-rectification. The distance between the "U" shaped slot and the lower boundary of the radiating structure is G1 = 1 mm, the length of the long side is L3 = 13.88 mm, the length of the short side is L4 = 2.2 mm, and the width is W2 = 0.4 mm.

[0066] This invention further adds a rectangular slot to the aforementioned radiating structure, which effectively suppresses the antenna's radiation of the second harmonic, making the antenna's impedance close to zero at the second harmonic frequency. This allows the harmonics generated in the rectifier circuit to be reflected back to the circuit for re-rectification. The rectangular slot is 2.3mm away from the lower boundary of the radiating structure, has a length of L5 = 13.48mm, and a width of W3 = 0.4mm. The antenna's feed microstrip line is located on the upper layer of the PCB and is used to transmit the RF energy received by the receiving antenna to the rectifier circuit. It has a length of L6 = 12mm and a width of W4 = 2mm.

[0067] The rectifier circuit unit in this invention consists of three microstrip lines, a diode, and an inductor. The specific circuit dimensions are as follows: the first microstrip line has a length of L7 = 14.4 mm and a width of W5 = 0.3 mm; the second microstrip line has a length of L8 = 13.9 mm and a width of W6 = 0.5 mm; the third microstrip line has a length of L9 = 5.1 mm and a width of W7 = 1 mm. The end of the second microstrip line is connected to the metal ground plane of the lower layer of the PCB through a metallized via. The inductor is a Murata product with an inductance value of 470 nH; the Schottky diode is an Infineon product, model BAT15-03W.

[0068] Figure 2 This figure shows the simulation results of the impedance of the receiving antenna of a single rectified antenna unit in the frequency range of 2GHz-8GHz. The solid line in the figure represents the real part of the antenna impedance, and the dashed line represents the imaginary part. The horizontal axis represents the frequency in GHz, and the vertical axis represents the impedance in Ω. As can be seen from the figure, the antenna impedance at the fundamental frequency of 2.45GHz is (18.8-j*16.6)Ω, the impedance at the second harmonic frequency of 4.9GHz is (2.6-j*13.4)Ω, and the impedance at the third harmonic frequency of 7.35GHz is (2-j*15)Ω. It is evident that the antenna impedance at the second and third harmonic frequencies is close to zero, indicating that the receiving antenna has a good suppression effect on the second and third harmonics.

[0069] Figure 3 This is a schematic diagram of the design principle of the present invention. In the diagram, Z1 represents the impedance of the receiving antenna. Figure 3The results show that the antenna impedance is close to zero at the second harmonic frequency f2 = 4.9 GHz and the third harmonic frequency f3 = 7.35 GHz. Therefore, the idealized analysis can be expressed as:

[0070] Z1 = 0, when f = f2, f3

[0071] According to transmission line theory, the impedance Z2 at the first microstrip line after Z1 undergoes impedance transformation via a quarter-wavelength microstrip line can be expressed as follows:

[0072]

[0073] Due to the DC blocking characteristic of inductors, the output impedance Z3 can be expressed as Z3 = ∞. When f = f2, f3, Z2 and Z3 are connected in parallel, and the impedance Z4 at the diode connection can be obtained, which can be expressed as:

[0074]

[0075] At the diode connection point, the second harmonic is approximately short-circuited and the third harmonic is approximately open-circuited. This makes the second harmonic voltage generated by the diode zero and the third harmonic current zero, thus reshaping the current and voltage waveforms. This makes the voltage and current waveforms passing through the diode resemble a Class-F shape (the voltage waveform resembles a square wave), reducing the switching losses in the diode rectification process and thereby improving the overall rectification efficiency.

[0076] Figure 4 The voltage spectrum analysis diagram across the diode is shown. Figure 4 The horizontal axis represents the frequency in GHz, and the vertical axis represents the voltage in decibels. From... Figure 4 It can be seen that at a frequency of 4.9 GHz, the second harmonic of the diode voltage is well suppressed, indicating that the impedance short-circuit effect of the second harmonic is achieved.

[0077] Figure 5 The diagram shows the current spectrum analysis across the diode. Figure 5 The horizontal axis represents the frequency in GHz, and the vertical axis represents the current in decibels. From Figure 5 It can be seen that at a frequency of 7.35 GHz, the third harmonic of the diode current is well suppressed, indicating that the impedance open circuit effect for the third harmonic is achieved.

[0078] like Figure 6 As shown, based on Figure 1 The design incorporates five rectifier antenna elements arranged symmetrically at the center, resulting in a high-efficiency omnidirectional rectifier antenna based on a Class F harmonic suppression structure. This antenna is printed on a 1mm thick sheet with a side length of L. 10The rectifier antenna is constructed on a pentagonal dielectric substrate with a diameter of 80.6 mm. The substrate material is FR4 with a dielectric constant εr of 4.4 and a loss tangent tanδ of 0.02. The metal ground plane is also a pentagon with a side length L1 = 70 mm. Each rectifier antenna element in the rectifier antenna is responsible for receiving radio frequency (RF) energy in its corresponding direction, achieving omnidirectional RF energy reception. The upper middle section of the PCB board is a DC combining network, consisting of five microstrip lines and circular metal patches, connected to the DC output terminals of each rectifier antenna element, serving as the positive terminal of the overall DC output of the rectifier antenna. The metal ground plane serves as the negative terminal of the DC output.

[0079] Figure 7 The results show the energy conversion efficiency of the rectifier antenna unit in this invention at different received powers when the operating frequency is 2.45 GHz. Figure 7 The numbers on the vertical axis represent the energy conversion efficiency, expressed as a percentage (%). As shown in the figure, the rectifier antenna achieves a rectification efficiency of 74.9% when the received power is 3 dBm. Figure 7 The discrepancy between the measurement results and the simulation results is due to circuit fabrication errors, which is within an acceptable range.

[0080] Figure 8 At an operating frequency of 2.45 GHz, the rectifier antenna unit of this invention achieves a received power density of 320 mW / m. 2 At that time, the test radiation pattern of the normalized DC voltage output of the rectifier antenna unit shows that the -3dB voltage beamwidth of the E plane is 60° and the -3dB voltage beamwidth of the H plane is 113°, which indicates that the rectifier antenna unit has good end-fire characteristics and is suitable for further expansion into an omnidirectional rectifier antenna array.

[0081] Figure 9 At an operating frequency of 2.45 GHz, the omnidirectional rectifier antenna array of this invention achieves a received power density of 320 mW / m. 2 At that time, the test radiation pattern of the normalized DC voltage output of the rectifier antenna omnidirectional array is shown in the voltage radiation patterns of the E-plane and H-plane. It can be seen that the received voltage fluctuates little with the change of direction, and has good omnidirectional characteristics.

[0082] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high efficiency omni-directional rectenna based on a class-F harmonic rejection structure, characterized by, The application relates to an antenna. The antenna comprises: a plurality of rectifying antenna units rotating around the same center and equidistantly distributed, which are used for receiving radio frequency energy in corresponding directions; the rectifying antenna is arranged on the surface of a double-layer PCB board, wherein the rectifying antenna unit comprises a receiving antenna and a rectifying circuit; the receiving antenna comprises an antenna radiation structure, a metal ground plate and a feeding microstrip line; wherein the antenna radiation structure and the metal ground plate are arranged on the lower surface of the PCB board, and the feeding microstrip line is arranged on the upper surface of the PCB board; a U-shaped groove is arranged on the area of the antenna radiation structure close to the metal ground plate, and a rectangular groove is arranged in the U-shaped groove; the U-shaped groove and the rectangular groove are used for suppressing the radiation of the second harmonic and the third harmonic; the rectifying circuit is arranged on the upper surface of the PCB board, and the rectifying circuit comprises a first microstrip line, a second microstrip line and a third microstrip line, wherein the first microstrip line is connected with the feeding microstrip line, the first microstrip line is connected with the second microstrip line through a diode, and the first microstrip line is connected with the third microstrip line through an inductor; a plurality of rectifying antenna units are connected through a direct current synthesis network, the direct current synthesis network comprises a plurality of microstrip lines and a circular metal patch connected with the plurality of microstrip lines; wherein the microstrip line is connected with the second microstrip line, and the circular metal patch is arranged at the center of rotation of the rectifying antenna unit.

2. The antenna according to claim 1, wherein the metal ground plates of all the rectifying antenna units form a polygonal shape, a circular gap is arranged at the center position of the rotation of the metal ground plates, and the number of the rectifying antenna units corresponds to the polygonal shape formed by the metal ground plates of all the rectifying antenna units.

3. The antenna according to claim 1, wherein the number of the rectifying antenna units is 5, and the metal ground plates of all the rectifying antenna units form a pentagonal shape.

4. The antenna according to claim 1, wherein the first microstrip line is a quarter-wave microstrip line.

5. The antenna according to claim 1, wherein the antenna radiation structure is a rectangular metal patch, a U-shaped groove is arranged in the area of the lower half of the rectangular metal patch close to the metal ground plate, and the rectangular groove is coincident with the symmetry axis of the U-shaped groove.

6. The antenna according to claim 1, wherein the working frequency of the rectifying antenna is 2.45 GHz.

7. The antenna according to claim 1, wherein one end of the third microstrip line away from the first microstrip line is connected with the metal ground plate through a metallized via hole.

8. The antenna according to claim 1, wherein the first microstrip line and the second microstrip line are arranged in parallel, and the first microstrip line and the third microstrip line are arranged perpendicularly.

9. The antenna according to claim 1, wherein the negative electrode of the diode is connected with the first microstrip line, and the positive electrode of the diode is connected with the second microstrip line.

10. The antenna according to claim 1, wherein the optimal working power is 3 dBm.

Images