High-efficiency omnidirectional rectification antenna based on F-type harmonic suppression structure

Abstract

The invention discloses a high-efficiency omnidirectional rectification antenna based on an F-type harmonic suppression structure, and belongs to the field of rectification antennae, and the high-efficiency omnidirectional rectification antenna comprises a plurality of rectification antenna units which rotate around the same center and are distributed at equal intervals, and the rectification antenna units are used for receiving radio frequency energy; the rectification antenna unit comprises a receiving antenna and a rectification circuit; the receiving antenna comprises an antenna radiation structure, a metal floor and a feed microstrip line; a U-shaped groove is formed in the area, close to the metal floor, of the antenna radiation structure, and a rectangular groove is formed in the U-shaped groove; the U-shaped groove and the rectangular groove are used for inhibiting radiation to second harmonic and third harmonic; the rectifying circuit is arranged on the upper surface of the PCB and is used for rectifying an output signal of the antenna radiation structure by the microstrip line and the electronic component; the plurality of rectification antenna units are connected through the DC synthesis network so that the size of the rectification antenna can be reduced and the efficiency of arranging the antenna can be enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave rectennas, and in particular relates to a high-efficiency omnidirectional rectenna based on a class F harmonic suppression structure. Background Art

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

[0003] In recent years, microwave wireless energy transmission has gradually shifted from high-power transmission to low-power transmission, using antennas as a carrier for energy transmission. Compared to the magnetic resonance coupling method commonly used for high-power wireless energy transmission, using antennas for energy transmission can reduce the size of the transmission carrier, facilitating integration with other devices. Furthermore, antenna design specifications are more flexible and adaptable, and they can be easily integrated with rectifier circuits to form rectennas, making them a more valuable research target.

[0004] With the continuous advancement of wireless communication technology, the density of ambient microwave energy is gradually increasing, while the power consumption of components such as sensors in wireless sensor nodes is gradually decreasing. This makes it possible to harvest this energy to power low-power sensors. Compared with traditional power supply methods (cable connections or batteries), harvesting microwave energy for power supply significantly reduces dependence on the power supply environment and reduces the cost of manual power supply maintenance, making it a research direction with high potential and high economic benefits.

[0005] As the most critical component of the receiving end of a microwave energy harvesting system, the rectenna converts the microwave energy emitted by the transmitting antenna into a DC voltage output. Its core module consists of two parts: the receiving antenna and the rectifier circuit. The receiving antenna receives RF energy from the environment, while the rectifier circuit converts the RF energy received by the receiving antenna into a DC voltage output. The receiving antenna typically achieves a reception efficiency exceeding 90%, so the efficiency of the rectifier circuit largely determines the efficiency of the rectifier circuit.

[0006] The rectification efficiency of a rectifier circuit is generally determined by the following two aspects. First, the degree of impedance matching plays a decisive role in the performance parameters of a rectifier circuit. Poor impedance matching can cause significant reflection of the RF energy input to the rectifier circuit, significantly reducing the circuit's energy conversion efficiency. It is worth noting that research in this area has reached a mature stage in academia and engineering. Through theoretical modeling and simulation optimization, researchers have designed circuits that can mostly achieve a high level of impedance matching performance, laying a solid foundation for improving rectification efficiency. Second, in the study of loss mechanisms in rectifier circuits, nonlinear losses in rectifier devices dominate. Rectifier components, typically represented by Schottky diodes, exhibit significant power dissipation characteristics during energy conversion in the microwave and millimeter wave bands. This loss is primarily due to 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 caused by the on-state voltage drop and reverse recovery current.

[0007] To improve the efficiency of rectennas, numerous scholars, both domestic and international, 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, April 2014," J. Guo et al. incorporated harmonic suppression techniques commonly used in power amplifiers into rectifier circuit design. This technique works by short-circuiting the circuit at even harmonics and keeping it open at odd harmonics, suppressing the circuit's harmonics and reshaping the current and voltage waveforms, thereby improving overall rectification efficiency. Through theoretical analysis, simulation, and field verification, their results show that the overall efficiency of rectifier circuits using a class-F structure can be improved by over 5% compared to circuits without it. However, traditional Class-F rectifier circuits usually require the introduction of open-circuit or short-circuit branches of different electrical lengths. Although this improves the efficiency of the rectifier circuit, it increases the system complexity and size.

[0008] In modern radio frequency environments, RF signal sources are numerous and widely distributed, such as wireless communication base stations, Wi-Fi routers, and broadcast towers. These sources transmit signals in varying directions and frequencies. To prevent directional antennas from missing some RF energy due to pointing errors, 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 pattern to form an antenna array, achieving omnidirectional reception of RF energy. Furthermore, by combining an antenna with a rectenna, the authors achieve direct matching between the antenna output impedance and the rectifier circuit input impedance based on complex conjugate matching theory. This eliminates the need for additional matching circuits in traditional rectifier circuits and significantly reduces the complexity and size of the rectenna system. However, the size and layout of the rectenna make it difficult to further introduce methods such as harmonic suppression structures to further improve the efficiency of the rectenna. Summary of the Invention

[0009] In order to solve the above technical problems, the present invention proposes a high-efficiency omnidirectional rectifying antenna based on a Class F harmonic suppression structure to solve the problems existing in the above-mentioned prior art.

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

[0011] A plurality of rectenna units rotating about the same center and distributed at equal intervals, the rectenna being used to receive radio frequency energy; the rectenna being arranged on the surface of a double-layer PCB board, wherein the rectenna unit includes a receiving antenna and a rectifier circuit;

[0012] The receiving antenna includes an antenna radiation structure, a metal floor and a feeding microstrip line; wherein the antenna radiation structure and the metal floor 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;

[0013] A U-shaped groove is provided on the antenna radiation structure in an area close to 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 harmonic and the third harmonic;

[0014] The rectifier circuit is arranged on the upper surface of the PCB board, and 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 feeding microstrip line, the first microstrip line is connected to the second microstrip line through a diode, and the first microstrip line is connected to the third microstrip line through an inductor;

[0015] Several of the rectenna units are connected through a DC synthesis network, which includes several microstrip lines and circular metal patches connected to the several microstrip lines; wherein the microstrip lines are connected to a third microstrip line, and the circular metal patch is arranged at the rotation center of the rectenna unit.

[0016] Optionally, the metal floors of all the rectifying antenna units form a polygonal shape, a circular gap is set at the center position of the rotation of the metal floor, and the number of the rectifying antenna units corresponds to the polygonal shape formed by the metal floors of all the rectifying antenna units.

[0017] Optionally, the number of the rectenna units is 5, and the metal floors of all the rectenna units 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 an area close to the metal floor, and the symmetry axis of the rectangular groove coincides with the axis of symmetry of the U-shaped groove.

[0020] Optionally, the bandwidth of the rectenna is 2.45 GHz.

[0021] Optionally, one end of the third microstrip line away from the first microstrip line is connected to the metal floor through a metallized via.

[0022] Optionally, 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 perpendicular to each other.

[0023] Optionally, 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.

[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) The receiving antenna in the present invention is an end-fire antenna. By adjusting the receiving antenna structure, a conjugate match is formed between the antenna and the rectifier circuit, without the need for an additional matching circuit. This reduces the complexity of the rectifier antenna, is also beneficial for reducing the size of the rectifier antenna, and improves the integration of the system.

[0027] (2) Compared with the traditional Class-F rectifier circuit, open or short-circuited branches of different electrical lengths are introduced to achieve Class-F rectification. In the present invention, the receiving antenna and the rectifier circuit are jointly designed, and a harmonic suppression structure is added on the basis of the radiation structure of the receiving antenna, so that the impedance of the receiving antenna at the second harmonic and third harmonic frequency points is close to zero. After the impedance transformation of the quarter-wavelength microstrip line, the impedance at the diode connection is the second harmonic open circuit and the third harmonic open circuit, which can make the second harmonic voltage generated by the diode zero and the third harmonic current zero, reshape the current and voltage waveforms, and realize Class-F rectification. While improving the efficiency of the rectifier antenna, the rectifier circuit is simpler and the layout is easier.

[0028] (3) The present invention arranges the designed rectenna units in a centrally symmetrical arrangement to obtain a plurality of RF energy receiving angles, thereby achieving omnidirectional reception of RF energy.

[0029] (4) The rectenna used for radio frequency energy collection in the present invention has strict design parameters and clear design steps.

[0030] (5) Compared with the existing rectenna, the present invention has a simpler structure and significantly improved efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

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

[0033] Figure 2 This is an impedance simulation diagram of a single rectenna unit receiving antenna according to an embodiment of the present invention;

[0034] Figure 3 Schematic diagram of the principle of an embodiment of the present invention;

[0035] Figure 4 1 is a current spectrum analysis diagram of the two ends of the diode according to an embodiment of the present invention;

[0036] Figure 5 2 is a voltage spectrum analysis diagram of the diode at both ends according to an embodiment of the present invention;

[0037] Figure 6 A physical diagram of a rectenna embodiment of the present invention;

[0038] Figure 7The simulation results of the energy conversion efficiency of the rectenna unit of the embodiment of the present invention at different received powers when the operating frequency is 2.45 GHz;

[0039] Figure 8 The embodiment of the present invention is a working frequency of 2.45 GHz and a receiving power density of 320 mW / m 2 When , the rectenna unit outputs the normalized test pattern of DC voltage;

[0040] Figure 9 The embodiment of the present invention is a working frequency of 2.45 GHz and a receiving power density of 320 mW / m 2 When , the rectenna omnidirectional array outputs the test pattern after the DC voltage is normalized. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

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

[0043] The present invention discloses a high-efficiency omnidirectional rectenna based on a Class F harmonic suppression structure. The circuit and antenna of the rectenna unit are printed on a double-layer PCB. The metal floor and antenna radiation structure are printed on the lower layer of the PCB, while the antenna feed microstrip line, the microstrip structure of the rectifier circuit, the DC synthesis network, and components are printed and soldered on the upper layer of the PCB.

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

[0045] The present invention, through joint design, enables the receiving antenna and the rectifier circuit to directly achieve a conjugate matching connection, without the need to design an additional matching circuit, thereby reducing the complexity of the rectifier antenna. The present invention suppresses the radiation of the second harmonic and the third harmonic by adding two slots in the antenna radiation structure. The impedance of the second and third harmonic frequency points of the receiving antenna is close to a short circuit. After the impedance transformation of the quarter-wavelength microstrip line, the impedance at the diode connection is a second harmonic short circuit and a third harmonic open circuit, which can make the second harmonic voltage generated by the diode zero and the third harmonic current zero, reshape the current and voltage waveforms, and make the voltage and current waveforms passing through the diode similar to the Class-F shape (the voltage waveform is similar to a square wave), reducing the switching loss during the diode rectification process. Thereby improving the overall rectification efficiency. The present invention further arranges the designed rectifier antenna units in a central symmetrical layout to achieve omnidirectional reception of radio frequency energy.

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

[0047] The present invention provides a high-efficiency omnidirectional rectifying antenna based on a class F harmonic suppression structure.

[0048] The rectenna is composed of an end-fire antenna with second and third harmonic suppression effects and a Class-F rectifier circuit. The two are directly connected in a conjugate matching manner without the need for an additional matching circuit. The impedance of the receiving antenna at the second and third harmonic frequency points is close to a short circuit. After the impedance transformation of the quarter-wavelength microstrip line, the impedance at the diode connection is a second harmonic short circuit and a third harmonic open circuit, which can make the second harmonic voltage generated by the diode zero and the third harmonic current zero, reshaping the current and voltage waveforms so that the voltage and current waveforms passing through the diode are similar to the Class-F shape (the voltage waveform is similar to a square wave), reducing the switching loss during the diode rectification process. This improves the overall rectification efficiency. The five rectenna units are centrally symmetrical, realizing omnidirectional reception of RF energy.

[0049] The rectenna circuit and antenna are printed on a two-layer PCB. The metal floor and antenna radiation structure are printed on the lower layer of the PCB, while the antenna feed microstrip line, DC synthesis network, rectifier circuit microstrip structure, and components are printed and soldered on the upper layer.

[0050] The rectenna consists of five identical rectenna units, which are symmetrically distributed on a pentagonal PCB. The rectenna unit includes a receiving antenna and a rectifier circuit.

[0051] The receiving antenna in the rectenna 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, printed on the lower layer of the PCB. Etched into the antenna radiating structure are a U-shaped slot and a rectangular slot. The two slots are arranged in mirror-image symmetry 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, respectively. This serves to suppress the antenna's radiation of second and third harmonics.

[0052] The metal floor is a pentagon with a side length of L1. The antenna radiating structure consists of five rectangles with a length of L2 and a width of W1. These are arranged on the five sides of the pentagonal metal floor, separated from the edges by a gap 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 and W3. The antenna's feed microstrip line, the rectifier circuit's microstrip structure, and the components are arranged symmetrically around the center of five identical units. Within each unit, the feed microstrip line is L6 and W4.

[0053] The rectifier circuit in the rectifier antenna unit is composed of a microstrip structure and patch components. The microstrip structure and patch components are printed and soldered on the upper layer of the PCB board, respectively. The rectifier circuit unit is composed of 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 the antenna's feed microstrip line. The second microstrip line is parallel to the first microstrip line, and the end of the second microstrip line, that is, the end away from the first microstrip line, is connected to the metal floor through 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 the first and second microstrip lines. The inductor is connected between the first and third microstrip lines.

[0054] The rectenna is composed of five rectenna units with the aforementioned structure, arranged rotationally symmetrically on a single PCB. Each unit receives RF energy in a corresponding direction. The DC synthesis network, consisting of five microstrip lines connected by circular metal patches, is located in the middle of the upper PCB. This network connects to the DC output of each rectenna unit and serves as the positive terminal for the overall DC output of the rectenna. The metal ground serves as the negative terminal for the DC output.

[0055] The rectenna has a bandwidth of 2.45 GHz, is a Class F harmonic suppression rectifier, and can achieve omnidirectional reception of radio frequency energy. The optimal input power is 3 dBm. The design method of this rectenna is applicable to the design of rectennas in any microwave frequency band.

[0056] Beneficial effects of the present invention:

[0057] (1) The receiving antenna in the present invention is an end-fire antenna. By adjusting the receiving antenna structure, a conjugate match is formed between the antenna and the rectifier circuit, without the need for an additional matching circuit. This reduces the complexity of the rectifier antenna, is also beneficial for reducing the size of the rectifier antenna, and improves the integration of the system.

[0058] (2) Compared with the traditional Class-F rectifier circuit, open or short-circuited branches of different electrical lengths are introduced to achieve Class-F rectification. In the present invention, the receiving antenna and the rectifier circuit are jointly designed, and a harmonic suppression structure is added on the basis of the radiation structure of the receiving antenna, so that the impedance of the receiving antenna at the second harmonic and third harmonic frequency points is close to zero. After the impedance transformation of the first microstrip line of a quarter wavelength, the impedance at the diode connection is the second harmonic open circuit and the third harmonic open circuit, which can make the second harmonic voltage generated by the diode zero and the third harmonic current zero, reshape the current and voltage waveforms, and realize Class-F rectification. While improving the efficiency of the rectifier antenna, the rectifier circuit is simpler and the layout is easier.

[0059] (3) The present invention arranges the designed rectenna units in a centrally symmetrical arrangement to obtain a plurality of RF energy receiving angles, thereby achieving omnidirectional reception of RF energy.

[0060] (4) The rectenna used for radio frequency energy collection in the present invention has strict design parameters and clear design steps.

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

[0062] (6) The present invention provides a detailed introduction to the rectennas used and demonstrates their working principles.

[0063] The above technical solution is described in detail with reference to the accompanying drawings and relevant data:

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

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

[0066] The present invention further adds a rectangular slot to the aforementioned radiating structure, effectively suppressing the antenna's second harmonic radiation. This effectively reduces the antenna's impedance at the second harmonic frequency, reducing it to near-zero. This allows the harmonics generated by the rectifier circuit to be reflected back to the circuit for further rectification. The rectangular slot is located at a distance G2 = 2.3 mm from the lower boundary of the radiating structure, has a length L5 = 13.48 mm, and a width W3 = 0.4 mm. The antenna's feed microstrip line, located on the upper layer of the PCB and used to transmit RF energy received by the receiving antenna to the rectifier circuit, has a length L6 = 12 mm and a width W4 = 2 mm.

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

[0068] Figure 2 This is the simulation result of the impedance of the receiving antenna of a single rectifying antenna unit of the present invention at a frequency of 2GHz-8GHz. The solid line in the figure represents the real part of the antenna impedance, the dotted line represents the imaginary part of the antenna impedance, the horizontal axis represents the frequency in GHz, and the vertical axis represents the impedance magnitude in Ω. It can be seen from the figure that 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 can be seen that the antenna impedance of the receiving antenna 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 figure, Z1 represents the impedance of the receiving antenna. Figure 3The results show that the antenna impedance of the receiving antenna at the second harmonic frequency f2 = 4.9 GHz and the third harmonic frequency f3 = 7.35 GHz is close to zero, so the idealized analysis can be expressed as:

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

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

[0072]

[0073] Due to the DC isolation characteristic of the inductor, the output impedance Z3 can be expressed as Z3 = ∞. When f = f2, f3, the impedance Z4 at the diode connection point can be obtained by connecting Z2 and Z3 in parallel, which can be expressed as:

[0074]

[0075] At the diode connection, the second harmonic is similar to a short circuit and the third harmonic is similar to an open circuit, which can make the second harmonic voltage generated by the diode zero and the third harmonic current zero, reshape the current and voltage waveforms, and make the voltage and current waveforms passing through the diode similar to the class-F shape (the voltage waveform is similar to a square wave), reducing the switching loss in the diode rectification process, thereby improving the overall rectification efficiency.

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

[0077] Figure 5 is the current spectrum analysis diagram at both ends of the diode, Figure 5 The horizontal axis represents the frequency in GHz, and the vertical axis represents the decibel value of the current. Figure 5 It can be seen that when the frequency is 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 rectenna unit is designed in the middle, and five rectenna units are placed symmetrically in the center to obtain the high-efficiency omnidirectional rectenna designed in this example based on the F-type harmonic suppression structure. The antenna is printed on a piece of 1mm thick and L side length. 10=80.6mm pentagonal dielectric substrate made of FR4, with a dielectric constant εr of 4.4 and a loss tangent tanδ of 0.02. The metal floor is a pentagon with a side length of L1 = 70mm. Each rectenna unit in the rectenna is responsible for receiving RF energy in a corresponding direction, achieving omnidirectional reception of RF energy. The DC synthesis network, consisting of five microstrip lines and circular metal patches, is connected to the DC output of each rectenna unit and serves as the positive terminal of the rectenna's overall DC output. The metal floor serves as the negative terminal of the DC output.

[0079] Figure 7 The figure shows the simulation results of the energy conversion efficiency of the rectenna unit of the present 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 in %. As can be seen from the figure, when the receiving power of the rectenna is 3dBm, the rectification efficiency reaches 74.9%. Figure 7 There is a certain error between the measurement results and the simulation results, which is introduced by the circuit processing error and is within an acceptable range.

[0080] Figure 8 When the operating frequency is 2.45GHz, the receiving power density of the rectenna unit of the present invention is 320mW / m 2 When the rectenna unit outputs the normalized DC voltage, the test radiation pattern shows that the -3dB voltage lobe width of the E plane is 60°, and the -3dB voltage lobe width of the H plane is 113°. This shows that the rectenna unit has good end-fire characteristics and is suitable for further expansion into an omnidirectional rectenna array.

[0081] Figure 9 When the operating frequency is 2.45GHz, the receiving power density of the omnidirectional rectifying antenna array of the present invention is 320mW / m 2 When the rectenna omnidirectional array outputs the normalized DC voltage test pattern, it can be seen from the E-plane and H-plane voltage patterns that the received voltage fluctuates little with the change of direction, and has good omnidirectional characteristics.

[0082] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A high-efficiency omnidirectional rectenna based on a Class F harmonic suppression structure, characterized in that: include: A plurality of rectenna units rotating about the same center and distributed at equal intervals, the rectenna units being used to receive radio frequency energy in corresponding directions; The rectenna is arranged on the surface of a double-layer PCB board, wherein the rectenna unit includes a receiving antenna and a rectifier circuit; The receiving antenna includes an antenna radiation structure, a metal floor and a feeding microstrip line; The antenna radiation structure and the metal floor 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 provided on the antenna radiation structure in an area close to 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 harmonic and the third harmonic; The rectifier circuit is arranged on the upper surface of the PCB board, and 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 feeding microstrip line, the first microstrip line is connected to the second microstrip line through a diode, and the first microstrip line is connected to the third microstrip line through an inductor; Several of the rectenna units are connected through a DC synthesis network, which includes several microstrip lines and circular metal patches connected to the several microstrip lines; wherein the microstrip lines are connected to a third microstrip line, and the circular metal patch is arranged at the rotation center of the rectenna unit.

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

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

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

5. The antenna according to claim 1, wherein The antenna radiation structure is a rectangular metal patch. A U-shaped groove is provided in the lower half of the rectangular metal patch, in an area close to the metal floor. The symmetry axes of the rectangular groove and the U-shaped groove coincide with each other.

6. The antenna according to claim 1, wherein The bandwidth of the rectenna 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 to the metal floor through a metallized via.

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

9. The antenna according to claim 1, wherein: 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.

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

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