A racket-shaped dual-frequency circularly polarized rectenna

Abstract

The present invention discloses a dual-frequency circularly polarized rectifier antenna with a racket-shaped structure. The present invention operates in the 2.45GHz frequency band and the 5.8GHz frequency band. The antenna includes a microstrip receiving antenna with a racket-shaped structure and a rectifier circuit; the rectifier circuit includes an input matching circuit, a DC blocking capacitor C1, a voltage doubler rectifier, an L-shaped harmonic suppression structure, a voltage stabilizing capacitor C2 and a load. The input matching circuit of the microstrip receiving antenna and the rectifier circuit are connected through an SMA head, the output end of the input matching circuit is connected to the input end of the voltage doubler rectifier through the DC blocking capacitor C1, and the output end of the voltage doubler rectifier is connected to the load through the L-shaped harmonic suppression structure. The polarization modes of the two frequency bands of the present invention are both circular polarization, which can not only collect energy in multiple frequency bands, but also effectively reduce polarization loss compared to traditional linearly polarized antennas, thereby improving the efficiency of energy reception.

Description

Technical Field

[0001] The invention belongs to the field of wireless energy transmission and relates to a dual-frequency circularly polarized rectenna with a racket-shaped structure. Background Art

[0002] In recent years, with the rapid development of wireless communication technology, the environment we live in is increasingly filled with electromagnetic energy. Furthermore, with the advent of the 5G era, the Internet of Things (IoT) has also experienced rapid growth. The IoT relies on a wide variety of sensors, and providing these sensors with long-term and effective power is a thorny issue. Traditionally, batteries have limited lifespans, resulting in high maintenance costs, and the use of large numbers of batteries inevitably harms the environment.

[0003] By collecting RF energy from the environment, rectennas can effectively and efficiently power these low-power sensor devices over the long term. Most existing rectennas are linearly polarized. Circularly polarized antennas offer lower polarization loss than linearly polarized antennas, further improving energy conversion efficiency. Consequently, research on circularly polarized rectennas is growing. However, existing circularly polarized antennas are often complex, using multi-layer structures. They only operate in a single frequency band, limiting their energy collection capabilities. Summary of the Invention

[0004] In view of this, an object of the present invention is to provide a dual-frequency circularly polarized rectenna with a racket-shaped structure for improving energy collection efficiency.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A racket-shaped dual-frequency circularly polarized rectenna operating in the 2.45 GHz and 5.8 GHz frequency bands, comprising a racket-shaped microstrip receiving antenna and a rectifier circuit;

[0007] The rectifier circuit includes an input matching circuit, a DC blocking capacitor C1, a voltage doubler rectifier, an L-shaped harmonic suppression structure, a voltage stabilizing capacitor C2 and a load;

[0008] The microstrip receiving antenna and the input matching circuit of the rectifier circuit are connected via an SMA connector, the output end of the input matching circuit is connected to the input end of the voltage doubler rectifier via a DC blocking capacitor C1, and the output end of the voltage doubler rectifier is connected to the load via an L-shaped harmonic suppression structure;

[0009] The microstrip receiving antenna is used to collect electromagnetic waves in space and convert them into guided waves to transmit the collected energy to the rectifier circuit;

[0010] The input matching circuit, on the one hand, matches the impedance of the microstrip receiving antenna and the voltage doubler rectifier; on the other hand, acts as an equal power divider to transmit power to the voltage doubler rectifier;

[0011] The voltage doubler rectifier is used to convert radio frequency energy into direct current energy;

[0012] The L-shaped harmonic suppression structure is used to suppress the high-order harmonics generated during the rectification process;

[0013] The voltage stabilizing capacitor C2 is used to reduce the ripple factor of the output voltage.

[0014] Furthermore, the microstrip receiving antenna is composed of a pair of racket-shaped microstrip patches, both of which are located under a dielectric substrate. Coaxial feeding is adopted for the feeding method. The coaxial outer core is connected to the patch P2, and the coaxial inner core passes through the dielectric substrate and is connected to a microstrip line on the dielectric substrate. The microstrip line on the dielectric substrate is connected to the patch P1 through a metal probe.

[0015] Furthermore, the patch P2 has an elliptical slot E1, which prevents the metal probe from being short-circuited with the patch P2 and improves the impedance bandwidth.

[0016] Furthermore, the input matching circuit is in the form of a coupled line, which is composed of a microstrip line MLIN1, two sections of coupled lines MCLIN1 and MCLIN2, and microstrip lines MLIN2 and MLIN3.

[0017] Furthermore, there are two voltage-doubling rectifiers, which adopt differential rectification and realize quadruple voltage rectification through a parallel structure;

[0018] The first voltage doubling rectifier is composed of a first DC blocking capacitor C1, a diode D1, a diode D2, and a first short-circuited microstrip line MLIN4; the anode of the diode D1 is connected to the L-shaped harmonic suppression structure, the cathode of the diode D1 is connected to the anode of the diode D2 and one end of the first DC blocking capacitor C1, and the other end of the first DC blocking capacitor C1 is connected to an output end of the input matching circuit; the cathode of the diode D2 is connected to one end of the first short-circuited microstrip line MLIN4, and the other end of the first short-circuited microstrip line MLIN4 is grounded;

[0019] The second voltage doubling rectifier is composed of a second DC blocking capacitor C1, a diode D3, a diode D4, and a second short-circuited microstrip line MLIN4; one end of the second short-circuited microstrip line MLIN4 is grounded, and the other end is connected to the anode of the diode D3. The cathode of the diode D3 is connected to one end of the second DC blocking capacitor C1 and the anode of the diode D4. The other end of the second DC blocking capacitor C1 is connected to the other output end of the input matching circuit; the cathode of the diode D4 is connected to the L-shaped harmonic suppression structure.

[0020] Furthermore, the length of the short-circuit microstrip line MLIN4 is one eighth of the wavelength of 5.8 GHz.

[0021] Furthermore, the DC blocking capacitor C1 prevents DC generated by the voltage doubler rectifier from backtracking, thereby causing energy loss.

[0022] Furthermore, the L-shaped harmonic suppression structure mainly suppresses 2.45GHz and 5.8GHz harmonics; it includes a microstrip line MLIN5, a coupled line MCLIN3, an open line MLIN7, a microstrip line MLIN6, a coupled line MCLIN4 and an open line MLIN8;

[0023] The microstrip line MLIN5, coupled line MCLIN3 and open line MLIN7 are used to suppress 2.45GHz harmonics. The length of the microstrip line MLIN5 is one quarter of the 2.45GHz wavelength, and the length of the coupled line MCLIN3 and open line MLIN7 is one quarter of the 2.45GHz wavelength.

[0024] The microstrip line MLIN6, coupled line MCLIN4 and open line MLIN8 are used to suppress 5.8 GHz harmonics. The length of the microstrip line MLIN6 is one quarter of the 5.8 GHz wavelength, and the length of the coupled line MCLIN4 and open line MLIN8 is one quarter of the 5.8 GHz wavelength.

[0025] The beneficial effects of the present invention are:

[0026] (1) The receiving antenna of the present invention is a racket-shaped dipole antenna that operates at 2.45 GHz and 5.8 GHz, and the polarization modes of both frequency bands are circular polarization. It can not only collect energy from multiple frequency bands, but also effectively reduce polarization loss compared to traditional linearly polarized antennas, thereby improving the efficiency of energy reception.

[0027] (2) The rectifier circuit of the present invention is composed of two voltage-doubling rectifiers connected in parallel, which can not only effectively increase the output DC voltage, but also has a higher rectification efficiency than the traditional single-tube series-parallel rectifier.

[0028] (3) The input matching circuit and L-shaped harmonic suppression structure of the present invention both adopt the form of coupled lines. Compared with the traditional fan-shaped branch method, it not only effectively reduces the area of ​​the rectifier circuit, but also achieves high performance of multiple frequencies, and realizes efficient rectification of dual frequencies of 2.45 GHz and 5.8 GHz.

[0029] (4) The output end of the rectifier diode D2 and the input end of the rectifier diode D3 of the present invention are grounded through a microstrip line MLIN4, the length of which is one-eighth of the 5.8 GHz wavelength. Compared with the direct grounding of the traditional rectifier circuit, the microstrip line not only compensates the input impedance of the diode, but also acts as a bandpass filter, further improving the rectification efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0031] Figure 1 This is a structural diagram of the rectenna described in the present invention.

[0032] Figure 2 This is a three-dimensional structural diagram of the receiving antenna described in the present invention.

[0033] Figure 3 This is a planar structural diagram of the receiving antenna patch described in the present invention.

[0034] Figure 4 It is the return loss of the rectenna described in the present invention.

[0035] Figure 5 This is the radiation pattern of the rectenna described in the present invention.

[0036] Figure 6 is the circular polarization elevation angle of the rectenna described in the present invention.

[0037] Figure 7 This is the axial ratio bandwidth diagram of the rectenna described in the present invention.

[0038] Figure 8 This is a diagram of the rectifying efficiency of the rectifying antenna described in the present invention. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art can easily understand the advantages and effects of the present invention through the contents disclosed in this specification. It should be noted that the drawings are only schematic diagrams, not physical drawings, and cannot be understood as limiting the present invention. The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components. In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back" and the like indicating an orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be understood as limiting the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to the specific circumstances. Similarly, those skilled in the art should also understand the corresponding "length", "width", "gap" and other descriptions.

[0040] See also Figures 1 to 8 ,like Figure 1As shown, a racket-shaped dual-frequency circularly polarized rectenna includes a receiving antenna, an SMA female connector, an SMA male connector, and a rectifier circuit; the rectifier circuit includes an input matching circuit in the form of a coupled bandpass filter, a quadruple voltage circuit formed by two parallel voltage-doubling rectifiers, an L-shaped harmonic suppression circuit, and a load.

[0041] The receiving antenna and the input matching circuit of the rectifier circuit are connected through an SMA head, the output end of the input matching circuit is connected to the input end of the rectifier through the DC blocking capacitor C1, the output end of the rectifier is connected to the input end of the L-shaped harmonic suppression structure, the output end of the L-shaped harmonic suppression structure is connected to the load, and the voltage stabilizing capacitor C2 is used to reduce the ripple factor of the output voltage.

[0042] The receiving antenna is used to collect microwave energy in space and convert it into guided waves;

[0043] The input matching circuit: on the one hand, matches the rectifier circuit and the receiving antenna; on the other hand, acts as a power divider to equally divide the energy and transmit it to the two parallel rectifiers;

[0044] The two voltage-doubling rectifiers are connected in parallel to form a quadruple voltage rectifier, and the output end of the rectifier diode D2 and the input end of the rectifier diode D3 are grounded via a microstrip line MLIN4;

[0045] The L-shaped harmonic suppression structure is used to filter out high-order harmonics generated during the rectification process.

[0046] The present embodiment is a racket-shaped dual-frequency circularly polarized rectenna. Unlike the traditional method of using multiple dipoles to achieve circular polarization, the present embodiment uses a single planar dipole structure and designs the two dipole arms into a racket shape to achieve circular polarization. The three-dimensional structure of the receiving antenna is shown in FIG. Figure 2 As shown, the antenna is a pair of dipole patches with a racket-shaped structure. Patches P1 and P2 are both located under a dielectric substrate with a size of 70*70*1.6mm. 3 The board is FR4, and the feeding method adopts coaxial feeding. The coaxial outer core is connected to the patch P2, and the coaxial inner core passes through the dielectric substrate and is connected to the microstrip line L above. The microstrip line L is connected to the patch P1 through a probe to feed P1. Figure 3 The figure shows the planar structure of the patch. An elliptical slot E1 is provided on the patch P1 to extend the impedance bandwidth.

[0047] The specific structure of this embodiment is as follows: the receiving antenna is connected to the rectifier circuit through an SMA connector. The dielectric plate used in the rectifier circuit is RO4350B. The input matching circuit of the rectifier circuit is composed of two coupled lines MCLIN1 and MCLIN2 and microstrip lines MLIN2 and MLIN3. The microstrip line MLIN1 is a 50-ohm microstrip line. The length, width, and gap of the coupled line MCLIN1 are 5.4 mm, 2.3 mm, and 0.7 mm, respectively; the length, width, and gap of the coupled line MCLIN2 are 10.7 mm, 2.7 mm, and 0.4 mm, respectively; the microstrip line MLIN2 is 15 mm long and 2.7 mm wide; and the microstrip line MLIN3 is 8.3 mm long and 2.5 mm wide. The voltage-doubling rectifier in the upper half of the rectifier circuit consists of a DC-blocking capacitor C1, diodes D1 and D2, and a short-circuited microstrip line MLIN4. When the RF energy is in the positive half, diode D2 conducts, charging capacitor C1. When the RF energy is in the negative half, diode D1 conducts. Due to the energy stored in capacitor C1, the voltage doubles when D1 conducts, thus achieving voltage-doubling rectification. The voltage-doubling rectifier in the lower half of the rectifier circuit consists of a DC-blocking capacitor C1, diodes D3 and D4, and a short-circuited microstrip line MLIN4. D3 conducts in the negative half to charge C1, and D4 conducts in the positive half to achieve voltage-doubling rectification. This forms differential rectification with the voltage-doubling rectifier in the upper half, and the two are connected in parallel to achieve quadruple voltage rectification. The DC blocking capacitor C1 is a Murata GQM series high-frequency capacitor with a value of 100pF. The rectifier diodes are all HSMS286C diodes. The short-circuited microstrip line MLIN4 is one-eighth the 5.8GHz wavelength and has a characteristic impedance of 100 ohms. The output harmonic suppression structure is an L-shaped structure. Microstrip line MLIN5, coupled line MCLIN3, and open line MLIN7 are used to suppress 5.8GHz harmonics, while microstrip line MLIN6, coupled line MCLIN4, and open line MLIN8 are used to suppress 2.45GHz harmonics. Microstrip line MLIN5 is 8.6mm long, coupled line MCLIN3 is 6.8mm long with a gap of 0.6mm, and open line MLIN7 is 4.3mm long. The coupled line MCLIN3 and open microstrip line MLIN7 are adjusted to suppress the 5.8GHz harmonic. The microstrip line MLIN6 is 18 mm long, the coupled line MCLIN4 is 13 mm long, with a gap of 0.3 mm. The open-circuit line MLIN8 is 9.6 mm long. Adjusting the coupled line MCLIN4 and the open-circuit microstrip line MLIN8 suppresses 2.45 GHz harmonics. The voltage stabilizing capacitor C2 has a value of 100 pF. In this embodiment, an 1800 ohm resistor is used as the load. The antenna dimensions were optimized using HFSS, and the rectifier circuit dimensions were optimized using ADS. Rectifier diodes D1, D2, D3, and D4 are all HSMS286C.

[0048] The working process of this embodiment is as follows: the receiving antenna collects radio frequency energy in the environment, and divides the collected energy into two parallel voltage-doubling rectifiers through the matching circuit. The two parallel voltage-doubling rectifiers form a four-fold voltage rectification in a differential form. The rectifier transmits the rectified energy into the L-shaped harmonic suppression structure, which only allows DC to pass through, and reflects the high-order harmonics generated during the rectification process back to the rectifier for further rectification. The DC component acts on the load to provide it with DC energy. At the same time, the voltage-stabilizing capacitor C2 also has the function of energy storage, which can make the output DC energy more stable, reduce the ripple coefficient, and thus make the input DC component smoother and more stable, thereby improving the stability of the system.

[0049] The performance of the racket-shaped dual-frequency circularly polarized rectenna of this embodiment is analyzed below:

[0050] like Figure 4 As shown, the antenna exhibits dual-band characteristics and has a good impedance bandwidth in both frequency bands. At low frequencies, the impedance bandwidth is 1.64 GHz (1.73 to 3.37 GHz), and at high frequencies, it is 3.12 GHz (4.88 to 8 GHz). It has a wide impedance bandwidth in both frequency bands. It covers the 2.4 / 5.2 / 5.8-GHz WLAN and 3.3 GHz 5G communication bands, and can collect energy in multiple frequency bands, especially in the WLAN band, which is also the main application band of rectennas today.

[0051] like Figure 5 (a) to (b) are the radiation patterns of the antenna at 2.45 GHz and 5.8 GHz. It can be seen from the figures that the radiation pattern at 2.45 GHz is in the form of a dipole with a maximum gain of 2.6 dBi. The maximum gain at 5.8 GHz is also 2.6 dBi, and the radiation pattern is omnidirectional.

[0052] like Figure 6 (a) to (b) are the circular polarization elevation angle diagrams of the antenna at 2.45 GHz and 5.8 GHz. As can be seen from the figures, the maximum circular polarization elevation angle is 84 degrees at 2.45 GHz, and the maximum circular polarization elevation angle is 56.45 degrees at 5.8 GHz. It can be seen that both frequency bands have good circular polarization elevation angles and have excellent circular polarization characteristics.

[0053] like Figure 7 is the circular polarization axial ratio bandwidth of the antenna. It can be seen from the figure that the circular polarization bandwidth in the low frequency band is 1.94 GHz (2.35-4.29 GHz), and the circular polarization bandwidth in the high frequency band is 650 MHz (5.48-6.13 GHz). It can be seen that there are excellent circular polarization bandwidths in both frequency bands. The axial ratio is 1.87 dB at 2.45 GHz and 1.48 dB at 5.8 GHz, and the performance is very good.

[0054] Figure 8 The figure shows the rectification efficiency of the rectenna at 2.45GHz and 5.8GHz. It can be seen that the highest rectification efficiency at 2.45Ghz is 80%, and the highest rectification efficiency at 5.8GHz is 79%. High-efficiency rectification is achieved in both frequency bands. Generally, traditional rectennas can only work in a single frequency band, and the highest rectification efficiency is between 60% and 70%.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A racket-shaped dual-band circularly polarized rectenna operating in the 2.45 GHz and 5.8 GHz frequency bands, characterized in that: The antenna comprises a microstrip receiving antenna with a racket-shaped structure and a rectifier circuit; The rectifier circuit includes an input matching circuit, a DC blocking capacitor C1, a voltage doubler rectifier, an L-shaped harmonic suppression structure, a voltage stabilizing capacitor C2 and a load; The microstrip receiving antenna and the input matching circuit of the rectifier circuit are connected via an SMA connector, the output end of the input matching circuit is connected to the input end of the voltage doubler rectifier via a DC blocking capacitor C1, and the output end of the voltage doubler rectifier is connected to the load via an L-shaped harmonic suppression structure; The microstrip receiving antenna is used to collect electromagnetic waves in space and convert them into guided waves to transmit the collected energy to the rectifier circuit; The input matching circuit, on the one hand, matches the impedance of the microstrip receiving antenna and the voltage doubler rectifier; on the other hand, acts as an equal power divider to transmit power to the voltage doubler rectifier; The voltage doubler rectifier is used to convert radio frequency energy into direct current energy; The L-shaped harmonic suppression structure is used to suppress the high-order harmonics generated during the rectification process; The voltage stabilizing capacitor C2 is used to reduce the ripple factor of the output voltage; The microstrip receiving antenna is composed of a pair of racket-shaped microstrip patches. Patch P1 and patch P2 are both located below a dielectric substrate and are fed using coaxial feeding. The coaxial outer core is connected to patch P2, and the coaxial inner core passes through the dielectric substrate and is connected to a microstrip line on the dielectric substrate. The microstrip line on the dielectric substrate is connected to patch P1 via a metal probe. The patch P2 has an elliptical slot E1, which prevents the metal probe from short-circuiting with the patch P2 and improves the impedance bandwidth. The input matching circuit is in the form of a coupled line, and is composed of a microstrip line MLIN1, two sections of coupled lines MCLIN1 and MCLIN2, and microstrip lines MLIN2 and MLIN3.

2. The racket-shaped dual-frequency circularly polarized rectenna according to claim 1, characterized in that: The DC blocking capacitor C1 prevents the DC generated by the voltage doubler rectifier from backtracking, which causes energy loss.

3. The racket-shaped dual-frequency circularly polarized rectenna according to claim 1, characterized in that: The L-shaped harmonic suppression structure mainly suppresses 2.45GHz and 5.8GHz harmonics; It includes a microstrip line MLIN5, a coupled line MCLIN3, an open line MLIN7, a microstrip line MLIN6, a coupled line MCLIN4 and an open line MLIN8; The microstrip line MLIN5, coupled line MCLIN3 and open line MLIN7 are used to suppress 2.45GHz harmonics. The length of the microstrip line MLIN5 is one quarter of the 2.45GHz wavelength, and the length of the coupled line MCLIN3 and open line MLIN7 is one quarter of the 2.45GHz wavelength. The microstrip line MLIN6, coupled line MCLIN4 and open line MLIN8 are used to suppress 5.8 GHz harmonics. The length of the microstrip line MLIN6 is one quarter of the 5.8 GHz wavelength, and the length of the coupled line MCLIN4 and open line MLIN8 is one quarter of the 5.8 GHz wavelength.

4. The racket-shaped dual-frequency circularly polarized rectenna according to claim 1, characterized in that: There are two voltage-doubling rectifiers, which adopt differential rectification and realize quadruple voltage rectification through parallel structure; The first voltage doubling rectifier is composed of a first DC blocking capacitor C1, a diode D1, a diode D2, and a first short-circuited microstrip line MLIN4; the anode of the diode D1 is connected to the L-shaped harmonic suppression structure, the cathode of the diode D1 is connected to the anode of the diode D2 and one end of the first DC blocking capacitor C1, and the other end of the first DC blocking capacitor C1 is connected to an output end of the input matching circuit; the cathode of the diode D2 is connected to one end of the first short-circuited microstrip line MLIN4, and the other end of the first short-circuited microstrip line MLIN4 is grounded; The second voltage doubling rectifier is composed of a second DC blocking capacitor C1, a diode D3, a diode D4, and a second short-circuited microstrip line MLIN4; one end of the second short-circuited microstrip line MLIN4 is grounded, and the other end is connected to the anode of the diode D3, the cathode of the diode D3 is connected to one end of the second DC blocking capacitor C1 and the anode of the diode D4, and the other end of the second DC blocking capacitor C1 is connected to the other output end of the input matching circuit; the cathode of the diode D4 is connected to the L-shaped harmonic suppression structure.

5. The racket-shaped dual-frequency circularly polarized rectenna according to claim 4, characterized in that: The length of the short-circuit microstrip line MLIN4 is one eighth of the 5.8 GHz wavelength.

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