A space electromagnetic energy harvesting system based on planar log-periodic antenna

Abstract

The present invention relates to a space electromagnetic energy collection system based on a planar logarithmic periodic antenna, and belongs to the field of electromagnetic technology. The system includes an improved planar logarithmic periodic antenna, an impedance matching rectifier unit and a power management unit; wherein the improved planar logarithmic periodic antenna is used to receive radio frequency signals in the 0.5GHz-3GHz frequency band in the environment; the impedance matching rectifier unit is connected to the improved planar logarithmic periodic antenna, wherein the impedance matching part realizes the maximum acquisition of the received signal, ensures that each link of the system maintains a standard impedance of 50 ohms, and the rectifier and filter part is composed of a transmission line, a fan-shaped branch and a diode rectifier array, and performs "signal-energy" conversion; the present invention improves the electromagnetic energy collection efficiency, can effectively extend the standby time of the Internet of Things terminal, and can solve the self-power supply problem of the ultra-low power consumption Internet of Things terminal, and has broad application prospects in the field of the Internet of Things.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic technology and relates to a space electromagnetic energy collection system based on a planar logarithmic periodic antenna. Background Art

[0002] Microwave energy harvesting technology has evolved from microwave wireless power transmission technology. It refers to a receiving system consisting of a receiving antenna and a rectifier circuit, which can collect and utilize electromagnetic energy of various frequency bands dispersed in space, including electromagnetic energy generated by mobile communications and wireless local area networks. Although the energy density of electromagnetic waves in space is low, they are widely distributed and have considerable utilization value and application prospects. Traditional microwave energy harvesting technology is limited to electromagnetic signals of several fixed frequency bands in space, and is gradually no longer applicable to today's increasingly rich electromagnetic environment.

[0003] The physical structure of the log-periodic antenna has the characteristics of non-frequency variation, so that its impedance, gain and other indicators can remain basically unchanged within a wide frequency band. With this advantage, the log-periodic antenna has great application prospects in the field of microwave energy collection. Although the traditional log-periodic antenna has a high gain, the three-dimensional aluminum structure design often makes the antenna cost high and the process complicated. At the same time, the bulky structure also limits the range of antenna deployment. At the same time, although the traditional planar log-periodic antenna based on the printed circuit board is easy to conform, it often has insufficient space utilization, does not consider circular polarization, poor low-frequency characteristics and other problems, and it is difficult to achieve the advantages of low cost, high gain, and wide bandwidth at the same time.

[0004] In summary, there is an urgent need for a space electromagnetic energy collection method and system based on an improved planar log-periodic antenna. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a space electromagnetic energy collection system based on a planar log-periodic antenna. By optimizing the traditional planar log-periodic antenna, the receiving band, circular polarization characteristics and low-frequency characteristics of the receiving antenna are improved; by designing an impedance matching rectifier unit, the circuit structure is simplified; by designing a power management unit, passive voltage management is achieved, reducing the loss of the traditional power management module. The system improves the collection efficiency of space electromagnetic energy through the structure, while greatly simplifying the size of the system, solving the shortcomings of the existing energy collection system, such as redundant size, low efficiency and limited working frequency band.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A space electromagnetic energy collection system based on a planar logarithmic periodic antenna, the system comprises an improved planar logarithmic periodic antenna, an impedance matching rectifier unit and a power management unit, wherein:

[0008] The improved planar log-periodic antenna is used to acquire radio frequency signals in the 0.5 GHz-3 GHz frequency band in the environment;

[0009] The impedance matching and rectifying unit is connected to the improved planar log-periodic antenna to achieve impedance matching and rectification filtering of the receiving antenna;

[0010] The power management unit is connected to the impedance matching rectification unit and is used to store and manage the DC energy output by the impedance matching rectification unit.

[0011] Optionally, the improved planar log-periodic antenna comprises a dielectric substrate, a feeding unit, a phase delay fan ring, a cross dipole and a peripheral metal layer;

[0012] The cross dipole comprises a plurality of dipole elements, and the length and width of the dipole elements are scaled in sequence along the length direction of the feeding unit according to a certain proportional factor;

[0013] Two pairs of crossed dipoles are respectively arranged on the upper surface and the lower surface of the dielectric substrate, and are centrally symmetrically arranged;

[0014] The crossed dipoles on the same side are orthogonal to each other and connected by phase-delay sector rings.

[0015] Optionally, the scaling factor τ of the improved planar log-periodic antenna satisfies:

[0016]

[0017] d n is the width of the corresponding dipole oscillator, L n is the length of the outer edge of the dipole oscillator, R n is the radius from the geometric center of the antenna to the outer edge of the corresponding dipole element, and n is the serial number of the corresponding dipole element;

[0018] The geometric vertex angle β of the dipole oscillator satisfies:

[0019]

[0020] α=2β+δ

[0021] δ is the geometric vertex angle of the aggregate line feeder in the feed unit, and α is the geometric vertex angle of the cross dipole;

[0022] The improved planar log-periodic antenna has a length L of the outer edge of each dipole element. n , Width d n The following relations are satisfied:

[0023]

[0024] Optionally, the improved planar log-periodic antenna further includes a feeding unit, which includes a collective line feeder and an auxiliary feeding unit, wherein the collective line feeder is connected to the dipole element in a fan shape, and the auxiliary feeding unit is connected to the feeding power source and the collective line feeder in a fan shape.

[0025] Optionally, the improved planar log-periodic antenna further includes a feeding source, which is disposed at one end of the feeding unit where any of the shortest dipole elements is located and is connected to the feeding unit.

[0026] Optionally, the improved planar log-periodic antenna also includes a phase delay fan ring, which implements the function of phase delay and realizes the circular polarization of the improved planar log-periodic antenna; the phase delay fan ring is arranged between the feeding units where the cross dipoles are orthogonally placed on the same side.

[0027] Optionally, the improved planar log-periodic antenna further includes a peripheral metal layer, which is arranged outside the longest and second longest dipole elements with a certain gap, and the peripheral metal layers on both sides of the plane are connected by two through holes.

[0028] Optionally, the improved planar log-periodic antenna, except for the auxiliary feeding unit, the distribution structure and size of the feeding unit, phase delay fan ring, peripheral metal layer and dipole vibrator on the upper surface of the dielectric substrate are the same as the distribution structure and size of the feeding unit, phase delay fan ring, peripheral metal layer and dipole vibrator on the lower surface of the dielectric substrate;

[0029] The improved planar log-periodic antenna has a dielectric substrate material of F4B, a relative dielectric constant of 2.65, a thickness of 1.575 mm, a square dielectric substrate with a side length of 160 mm, a geometric vertex angle β of the dipole oscillator of 40°, a geometric vertex angle δ of the aggregate line feeder of 5°, a geometric vertex angle ω1 of the fan-shaped auxiliary feeding unit of 45°, an outer radius r1 of 6.5 mm, an outer radius r1 of the phase delay ring fan of 6.5 mm, a geometric vertex angle ω2 of 225°, a width W of 1 mm, and a gap width g of 0.5 mm between the outer metal layer and the longest and second longest dipole oscillators;

[0030] The improved planar log-periodic antenna has 17 dipole elements staggeredly distributed on both sides of the collective line feeder. The longest dipole element has a length L1=52.36mm, a width d1=7.4mm, a proportional factor τ=0.9 for each dipole element, and a geometric apex angle α=85° for the cross dipoles.

[0031] Optionally, the impedance matching rectifier unit includes an input bandpass filter and a matching network, and the input filter and the matching network are composed of TL1, TL2, TL3, and TL4 transmission lines, wherein TL1 and TL2 transmission lines constitute the input bandpass filter, and TL3 and TL4 transmission lines constitute the matching network, so as to realize baseband selection and 50 ohm impedance transformation.

[0032] Optionally, the impedance matching rectifier unit further includes a rectifier diode, and the diode array is composed of two HSM276AS Schottky diodes D1 and D2, which are connected to the input filter and the matching network, and are used to rectify the RF energy after filtering and matching to achieve "signal-energy" conversion;

[0033] The impedance matching rectifier unit further includes an output straight-through filter, which is composed of TL5, TL6, TL7 transmission lines and Stub1, Stub2 fan-shaped branches, and is used to perform DC filtering on the rectified RF energy;

[0034] Optionally, the power management unit includes a weak energy management circuit, which is connected to an impedance matching rectifier unit, an auxiliary boost circuit, a maximum power point tracking circuit and a super capacitor; the weak energy management circuit works in conjunction with the auxiliary boost circuit and the maximum power point tracking circuit to convert a DC voltage input by the impedance matching rectifier circuit to a preset voltage, and outputs it to the super capacitor for storage;

[0035] The power management unit also includes an auxiliary boost circuit, and the two ends of the auxiliary boost circuit are respectively connected to the impedance matching rectifier unit and the weak energy management circuit; when the preset voltage of the power management unit is greater than the DC voltage output by the impedance matching rectifier unit, the weak energy management circuit will activate the auxiliary boost circuit to realize the boost conversion function;

[0036] The power management unit also includes a maximum power point tracking circuit, and two ends of the maximum power point tracking circuit are respectively connected to the impedance matching rectification unit and the weak energy management circuit; the maximum power point tracking circuit periodically divides and stores the DC voltage output by the impedance matching rectification unit and outputs it, so as to provide a maximum power point tracking reference voltage for the weak energy management circuit;

[0037] The power management unit also includes a super capacitor, which is connected to the DC output end of the weak energy management circuit and is responsible for storing the DC energy of constant voltage output by the weak energy management circuit.

[0038] The beneficial effects of the present invention are as follows: by adopting the improved planar logarithmic periodic antenna, the system has an ultra-wide working bandwidth, covering the 0.5GHz-3GHz spectrum range, supporting 3G, 4G, GSM and WIFI frequency bands; by designing the impedance matching rectifier unit and the power consumption management unit, the circuit structure is simplified and the energy collection efficiency of the system is improved. The whole system has the advantages of high gain, wide bandwidth, high efficiency, etc., and has certain guiding significance for space electromagnetic energy collection.

[0039] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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 in conjunction with the accompanying drawings, wherein:

[0041] Figure 1 It is a structural schematic diagram of a method and system for collecting space electromagnetic energy based on an improved planar log-periodic antenna in a specific embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of the planar structure of an improved planar log-periodic antenna in a specific embodiment of the present invention;

[0043] Figure 3 It is a schematic diagram of the front structure of an improved planar log-periodic antenna in a specific embodiment of the present invention;

[0044] Figure 4 It is a schematic diagram of the back structure of an improved planar log-periodic antenna in a specific embodiment of the present invention;

[0045] Figure 5 A return loss curve of an improved planar log-periodic antenna in a specific embodiment of the present invention;

[0046] Figure 6 An axial ratio curve of an improved planar log-periodic antenna in a specific embodiment of the present invention;

[0047] Figure 7 The three-dimensional radiation pattern of the improved planar log-periodic antenna in a specific embodiment of the present invention in the low frequency band (500MHz and 1000MHz);

[0048] Figure 8 The three-dimensional radiation pattern of the improved planar log-periodic antenna in the mid-frequency band (1500 MHz and 2000 MHz) in one specific embodiment of the present invention;

[0049] Fig. 9 The three-dimensional radiation pattern of the improved planar log-periodic antenna in a specific embodiment of the present invention in the low frequency band (2500MHz and 3000MHz);

[0050] Fig.10 A circuit block diagram of an impedance matching rectifier unit in a specific embodiment of the present invention;

[0051] Fig.11 FIG. 4 is a circuit block diagram of a power management unit in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0052] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0053] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0054] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0055] 1. In one embodiment, Figure 1 As shown, a method and system for collecting space electromagnetic energy based on an improved planar log-periodic antenna comprises an improved planar log-periodic antenna, an impedance matching rectifier unit and a power management unit; wherein,

[0056] The improved planar log-periodic antenna is used to obtain radio frequency energy in the 0.5 GHz-3 GHz frequency band in the environment;

[0057] The impedance matching and rectifying unit is connected to the improved planar log-periodic antenna to achieve impedance matching and rectification filtering of the receiving antenna;

[0058] The power management unit is connected to the impedance matching rectification unit and is used to store and manage the DC energy output by the impedance matching rectification unit.

[0059] In this embodiment, the receiving band, circular polarization characteristics and low-frequency characteristics of the receiving antenna are improved by optimizing the traditional planar logarithmic periodic antenna; the circuit structure is simplified by designing an impedance matching rectifier unit; and passive voltage management is achieved by designing a power management unit, reducing the loss of the traditional power management module. The system improves the efficiency of collecting electromagnetic energy in space through the structure, while greatly simplifying the size of the system, solving the shortcomings of the existing energy collection system, such as redundant size, low efficiency and limited working frequency band.

[0060] 2. In another embodiment, Figure 2 As shown, the improved planar log-periodic antenna comprises a dielectric substrate, a feeding unit, a phase delay fan ring, a cross dipole and a peripheral metal layer; the cross dipole comprises a plurality of dipole elements, and the length and width of the dipole elements are scaled in sequence along the length direction of the feeding unit according to a certain proportional factor; two pairs of cross dipoles are respectively arranged on the upper surface and the lower surface of the dielectric substrate, and are centrally symmetrically arranged; the cross dipoles on the same side are orthogonal to each other and are connected by the phase delay fan ring.

[0061] S11: Proportional factor τ (or periodicity), which indicates the proportional relationship between the dipole elements; the geometric vertex angle β of the dipole element; the vertex angle α of the cross dipole. The three parameters are independent of each other and jointly determine the structural composition of the antenna:

[0062]

[0063]

[0064] α=2*β+δ

[0065] Wherein: d is the distance between adjacent dipoles, L is the length of the outer edge of the dipole element, R is the radius from the geometric center of the antenna to the outer edge of the dipole element, n is the serial number of each dipole element, and δ is the geometric vertex angle of the collective line feeder in the feed unit.

[0066] S12: n dipoles of different lengths are fed by a fan-shaped collective line feeder. The feed source is connected to one end of the shortest dipole. Two adjacent dipoles are cross-fed. The cross-feeding method can play a role in the conversion from unbalanced to balanced. After the cross-dipole is fed, the electromagnetic energy will be transmitted from the feed point (feed source) along the collective line feeder, and each dipole will be excited in turn. The length of the dipole near the feed point is much smaller than the wavelength, the input impedance is very high, the current is very small, and the radiation is very weak, so it is called the transmission zone; the electromagnetic wave energy will resonate at the dipole length close to λ / 2, and the radiation reaches a peak, and this area becomes the radiation zone; the remaining small part of the energy continues to propagate forward, and the reflection at the end of the cross dipole is already very weak, becoming an unexcited zone. The current on the dipole in the radiation zone is the largest, and there is a 180-degree phase difference between the currents on adjacent dipoles in the radiation zone. Therefore, the working principle of the dipole in the radiation zone is similar to that of the Yagi antenna, the dipole in the unexcited zone is similar to a reflector, and the dipole in the transmission zone is similar to a director. The radiation pattern finally realizes the end-fire characteristic in the direction of the short dipole. Therefore, the working principle of the cross dipole ensures its wide bandwidth. The fan-shaped auxiliary feeding unit connects the feed source and the collective line feeder, and plays a certain role in impedance matching. The phase delay fan ring connects the two cross dipoles on the same side. Since the cross dipole structures are completely consistent and there is an orthogonal relationship in space, the horizontal and vertical components of the generated electric field have equal amplitudes and a phase difference of 90°, thus ensuring that the antenna has a certain circular polarization characteristic. The outer metal layer is arranged outside the longest and second longest dipoles, and a certain gap is left. The outer metal layers on both sides of the plane are connected through two through holes, and the dipole and the outer metal layer form a coupling relationship through the gap. The impedance bandwidth of the low frequency band can be effectively expanded, and the low frequency characteristics of the antenna can be improved to a certain extent.

[0067] S13: In this embodiment, the improved planar log-periodic antenna, the PCB substrate medium adopts F4B with a relative dielectric constant of 2.65 and a thickness of 1.575 mm; the shape of the PCB dielectric substrate is a square with a side length of 160 mm.

[0068] S14: In this embodiment, the improved planar log-periodic antenna, reference Figure 2 As shown, the geometric vertex angle α of the cross dipole is 85°, the proportional factor τ of each dipole is 0.9, the geometric vertex angle β of the dipole is 40°, the geometric vertex angle δ of the fan-shaped aggregate line feeder is 5°, the geometric vertex angle ω1 of the fan-shaped auxiliary feeding unit is 45°, the outer radius r1 is 6.5mm, the angle ω2 of the phase delay fan ring is 225°, the outer radius r1 is 6.5mm, the width W is 1mm, and the gap g between the dipole and the outer metal layer is 0.5mm.

[0069] S15: According to the design principle of log-periodic antenna, each dipole element of the improved planar log-periodic antenna is staggered along the collective line feeder. In order to obtain the optimal antenna bandwidth and gain, there are 17 dipole elements on each side of the antenna feeder in this embodiment, so n = 17. After optimizing the gain and bandwidth of the antenna, the length of the initial dipole element L1 = 52.36 mm and the width d1 = 7.4 mm. It can be concluded that the physical length and width of the nth dipole element are:

[0070] L n =L1*τ n-1

[0071] d n =d1*τ n-1

[0072] where n∈[1,13].

[0073] It should be noted that the antenna is fed by a coaxial cable, except for the auxiliary feeding unit, such as Figure 2 to Figure 4 , front and back views of the antenna Figure 1 The auxiliary feeding units on the front and back sides are respectively connected to the inner and outer conductors of the coaxial line, so the auxiliary feeding unit on the back side is fan-shaped, the outer radius of the fan-shaped ring is the same as the outer radius of the auxiliary feeding unit on the front side, and the inner radius is determined by the specific coaxial line used.

[0074] S16: In this example, the improved planar log-periodic antenna was subjected to a 500MHz-3.0GHz microwave full-wave simulation after the design was completed. Figure 5 The return loss curve of the improved log-periodic antenna is shown. It can be clearly seen from the figure that the S11 performance of the antenna in this example fluctuates with frequency around -9dB in the 500MHz-3GHz frequency band, meeting the needs of space electromagnetic energy collection.

[0075] S17: In order to reflect the circular polarization characteristics of the improved planar log-periodic antenna in each operating frequency band, Figure 6 The axial ratio curve of the antenna in each working frequency band is given. From the figure, it can be clearly concluded that the axial ratio of the antenna in this example shows an overall downward trend in the 500MHz-3.0GHz frequency band, and is below 8dB in the 1.5GHz-3GHz working frequency band. Therefore, the antenna has a good collection effect on electromagnetic waves of any polarization.

[0076] S18: In order to reflect the radiation directivity of the improved planar log-periodic antenna in each operating frequency band, Figure 7 to Figure 9The three-dimensional radiation pattern of the antenna in each working frequency band is given. It can be clearly seen from the figure that in the 500MHz-3GHz frequency band, the antenna gain of this example is at the level of 5.0dBi-10.0dBi, and the overall high-frequency gain is better than the low-frequency gain. The main lobe of the antenna points to the vertical direction of the antenna and has a large main lobe width. No side lobes are observed. Therefore, the energy radiation of the antenna is relatively concentrated. The antenna has a high radiation efficiency and an extremely wide working bandwidth, which meets the scenario of space electromagnetic energy collection.

[0077] 3. In another embodiment, the impedance matching rectifier unit includes an input filter and a matching network, a rectifier diode and an output pass filter.

[0078] S21: In this embodiment, if Fig.10 As shown, the input filter and matching network include transmission lines TL1 to TL4, one end of which is connected to a modified planar logarithmic periodic antenna for receiving radio frequency signals, the other end of TL1 is connected to the ground, the other end of TL2 is suspended, and TL1 and TL2 form an input bandpass filter for filtering high-frequency electromagnetic energy in non-target frequency bands; the other end of TL3 is suspended, the other end of TL4 is connected to a rectifier diode, and TL3 and TL4 form an L-type impedance matching network. In space electromagnetic energy collection, the antenna needs to transmit energy through the radio frequency transmission line after collecting it. In order to reduce standing waves, the receiving unit needs to perform impedance matching with the radio frequency transmission line, and the characteristic impedance of the radio frequency transmission line is 50Ω, so the skin effect loss is the smallest. Therefore, the antenna output impedance is generally designed to be 50Ω. The input of the rectifier circuit is the output of the receiving unit, and also needs to be impedance matched with the front-end unit. Therefore, this embodiment determines the target frequency band by changing the length and width of the transmission lines TL1 and TL2, and matches the input impedance of the rectifier diode to 50Ω by changing the length and width of the transmission lines TL3 and TL4. If it is not matched, standing waves will exist during the signal transmission process, resulting in return loss, thereby reducing the conversion efficiency of the rectifier diode.

[0079] S22: In this embodiment, if Fig.10 As shown, one end of the rectifier diodes D1 and D2 is connected to the transmission line TL4 for receiving the RF signal after filtering and impedance matching, and the other end is connected to the transmission line TL5. The other end of the transmission line TL5 is connected to the transmission lines TL6, TL7 and the output port, the other end of the transmission line TL6 is connected to the fan-shaped branch Stub1, and the other end of the transmission line TL7 is connected to the fan-shaped branch Stub2. The transmission lines TL5, TL6, TL7 and the fan-shaped branches Stub1 and Stub2 together form an output pass filter, which filters the DC signal containing the RF signal component output by the rectifier diode into a stable DC signal.

[0080] S23: In this embodiment, if Fig.10As shown, with 2.45 GHz as the target frequency band, the width W of the transmission line TL1 TL1 =2mm, length L TL1 =8.0mm. Width W of transmission line TL2 TL2 =4.1mm, length L TL2 =11.6mm. Width W of transmission line TL3 TL3 =3.0mm, length L TL3 =11.3mm. Width W of transmission line TL4 TL4 =3.0mm, length L TL4 =7.6mm. The model of the rectifier diodes D1 and D2 is HSM276AS. The width of the transmission line TL5 is W TL5 =3.0mm, length L TL5 =7.8mm. Width W of transmission line TL6 TL6 =3.0mm, length L TL6 =9.7mm. Width W of transmission line TL7 TL7 =3.0mm, length L TL7 =9.7mm. Geometric vertex angle β of fan-shaped branch Stub1 st1 =120°, radius L St1 =12.7mm. The geometric vertex angle β of the fan-shaped branch Stub2 st2 =120°, radius L St2 =12.7mm.

[0081] S24: By redesigning the impedance matching rectifier circuit, the impedance matching rectifier unit designed in this embodiment adopts a filter matching-rectification-DC filtering mode, which avoids interference from other RF signals outside the target frequency band, simplifies the circuit structure, reduces the size of the circuit, and can output a relatively stable DC signal, which is convenient for the subsequent circuit to achieve maximum power point tracking.

[0082] 4. In another embodiment, the power management unit includes a weak energy management circuit, an auxiliary boost circuit, a maximum power point tracking circuit and a super capacitor.

[0083] S31: In this embodiment, Fig.11 As shown, the output of the impedance matching rectifier unit is respectively connected to the weak energy management circuit, the auxiliary boost circuit and the maximum power point tracking circuit, the other end of the weak energy management circuit is connected to the super capacitor, and the other ends of the auxiliary boost circuit and the maximum power point tracking circuit are connected to the output of the impedance matching rectifier unit.

[0084] S32: The power management unit described in the above embodiment, when the output voltage of the impedance matching rectifier unit is lower than the starting voltage, the weak energy management circuit is in the shutdown state; otherwise, the weak energy management circuit will be activated. When the preset voltage of the power management unit is less than the DC voltage output by the impedance matching rectifier unit, the auxiliary boost unit is disabled, and the weak energy management circuit converts the output voltage of the impedance matching rectifier unit to the preset voltage; when the preset voltage of the power management unit is greater than the DC voltage output by the impedance matching rectifier unit, the auxiliary boost unit is activated, and works together with the weak energy management circuit to convert the output voltage of the impedance matching rectifier unit to the preset voltage.

[0085] S33: In the power management unit described in the above embodiment, the weak energy management circuit is disconnected at regular intervals, and at this time, the maximum power point tracking circuit performs voltage division transformation on the open-circuit output voltage of the impedance matching rectifier unit, and outputs the maximum power point tracking reference voltage to the weak energy management circuit. The weak energy management circuit will automatically adjust the charging current of the supercapacitor so that the output voltage of the impedance matching rectifier unit continues to work at the maximum power point tracking reference voltage to obtain the highest conversion efficiency.

[0086] S34: The power management unit described in the above embodiment uses a supercapacitor as an energy storage device, and the weak energy management circuit monitors the voltage value of the supercapacitor in real time. When the voltage value of the supercapacitor reaches a preset voltage, the weak energy management circuit will start overcharging protection and the charging current will be reduced to zero.

[0087] S35: Compared with the existing power management unit, the power management unit designed in this embodiment adopts an acquisition-conversion-storage mode, which does not require an external power supply and a microprocessor circuit to monitor the output voltage of the impedance matching rectifier unit, thereby reducing costs and power consumption, improving the accuracy of the output voltage, and further reducing the volume of the space electromagnetic energy collection device.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A spatial electromagnetic energy collection system based on a planar log-periodic antenna, characterized in that: The system includes an improved planar logarithmic periodic antenna, an impedance matching rectifier unit and a power management unit, wherein: The improved planar log-periodic antenna is used to acquire radio frequency signals in the 0.5 GHz-3 GHz frequency band in the environment; The impedance matching and rectifying unit is connected to the improved planar log-periodic antenna to achieve impedance matching and rectification filtering of the receiving antenna; The power management unit is connected to the impedance matching rectification unit and is used to store and manage the DC energy output by the impedance matching rectification unit; The improved planar log-periodic antenna comprises a dielectric substrate, a feeding unit, a phase delay fan ring, a cross dipole and a peripheral metal layer; The cross dipole comprises a plurality of dipole elements, and the length and width of the dipole elements are scaled in sequence along the length direction of the feeding unit according to a certain proportional factor; Two pairs of crossed dipoles are respectively arranged on the upper surface and the lower surface of the dielectric substrate, and are centrally symmetrically arranged; The crossed dipoles on the same side are orthogonal to each other and connected by a phase-delayed sector ring; The scale factor τ of the improved planar log-periodic antenna satisfies: d n is the width of the corresponding dipole oscillator, L n is the length of the outer edge of the dipole oscillator, R n is the radius from the geometric center of the antenna to the outer edge of the corresponding dipole element, and n is the serial number of the corresponding dipole element; The geometric vertex angle β of the dipole oscillator satisfies: α=2β+δ δ is the geometric vertex angle of the aggregate line feeder in the feed unit, and α is the geometric vertex angle of the cross dipole; The improved planar logarithmic periodic antenna has a length L of the outer edge of each dipole element. n , Width d n The following relations are satisfied:

2. A spatial electromagnetic energy collection system based on a planar log-periodic antenna according to claim 1, characterized in that: The improved planar log-periodic antenna also includes a feeding unit, which includes a collective line feeder and an auxiliary feeding unit. The collective line feeder is connected to the dipole element in a fan shape, and the auxiliary feeding unit is connected to the feeding source and the collective line feeder in a fan shape.

3. The spatial electromagnetic energy collection system based on a planar log-periodic antenna according to claim 1, characterized in that: The improved planar log-periodic antenna also includes a feeding source, which is arranged at one end of the feeding unit where any of the shortest dipole elements is located and connected to the feeding unit.

4. The spatial electromagnetic energy collection system based on a planar log-periodic antenna according to claim 1, characterized in that: The improved planar log-periodic antenna also includes a phase delay fan ring, which realizes the function of phase delay and realizes the circular polarization of the improved planar log-periodic antenna; the phase delay fan ring is arranged between the feeding units where the cross dipoles are orthogonally placed on the same side.

5. The spatial electromagnetic energy collection system based on planar log-periodic antenna according to claim 1, characterized in that: The improved planar log-periodic antenna also includes an outer metal layer, which is arranged outside the longest and second longest dipole elements with a certain gap, and the outer metal layers on both sides of the plane are connected through two through holes.

6. The spatial electromagnetic energy collection system based on planar log-periodic antenna according to claim 1, characterized in that: The improved planar log-periodic antenna, except for the auxiliary feeding unit, the distribution structure and size of the feeding unit, phase delay fan ring, peripheral metal layer and dipole oscillator on the upper surface of the dielectric substrate are the same as the distribution structure and size of the feeding unit, phase delay fan ring, peripheral metal layer and dipole oscillator on the lower surface of the dielectric substrate; The improved planar log-periodic antenna has a dielectric substrate material of F4B, a relative dielectric constant of 2.65, a thickness of 1.575 mm, a square dielectric substrate with a side length of 160 mm, a geometric vertex angle β of the dipole oscillator of 40°, a geometric vertex angle δ of the aggregate line feeder of 5°, a geometric vertex angle ω1 of the fan-shaped auxiliary feeding unit of 45°, an outer radius r1 of 6.5 mm, an outer radius r1 of the phase delay ring fan of 6.5 mm, a geometric vertex angle ω2 of 225°, a width W of 1 mm, and a gap width g of 0.5 mm between the outer metal layer and the longest and second longest dipole oscillators; The improved planar log-periodic antenna has 17 dipole elements staggeredly distributed on both sides of the collective line feeder. The longest dipole element has a length L1=52.36mm, a width d1=7.4mm, a proportional factor τ=0.9 for each dipole element, and a geometric apex angle α=85° for the cross dipoles.

7. The spatial electromagnetic energy collection system based on planar log-periodic antenna according to claim 1, characterized in that: The impedance matching rectifier unit includes an input bandpass filter and a matching network, wherein the input bandpass filter and the matching network are composed of TL1, TL2, TL3, and TL4 transmission lines, wherein TL1 and TL2 transmission lines constitute the input bandpass filter, and TL3 and TL4 transmission lines constitute the matching network, so as to realize baseband selection and 50 ohm impedance transformation.

8. The spatial electromagnetic energy collection system based on a planar log-periodic antenna according to claim 1, characterized in that: The impedance matching rectifier unit also includes a rectifier diode, and the diode array is composed of two HSM276AS Schottky diodes D1 and D2, which are connected to the input filter and the matching network to rectify the RF energy after filtering and matching to achieve "signal-energy" conversion; The impedance matching rectifier unit further includes an output straight-through filter, which is composed of TL5, TL6, TL7 transmission lines and Stub1, Stub2 fan-shaped branches, and is used to perform DC filtering on the rectified RF energy; The power management unit includes a weak energy management circuit, which is connected to an impedance matching rectifier unit, an auxiliary boost circuit, a maximum power point tracking circuit and a super capacitor; the weak energy management circuit works in conjunction with the auxiliary boost circuit and the maximum power point tracking circuit to convert a DC voltage input by the impedance matching rectifier circuit to a preset voltage, and outputs it to the super capacitor for storage; The power management unit also includes an auxiliary boost circuit, and two ends of the auxiliary boost circuit are respectively connected to the impedance matching rectifier unit and the weak energy management circuit; when the preset voltage of the power management unit is greater than the DC voltage output by the impedance matching rectifier unit, the weak energy management circuit will activate the auxiliary boost circuit to realize the boost conversion function; The power management unit also includes a maximum power point tracking circuit, and two ends of the maximum power point tracking circuit are respectively connected to the impedance matching rectification unit and the weak energy management circuit; the maximum power point tracking circuit periodically divides and stores the DC voltage output by the impedance matching rectification unit and outputs it, so as to provide a maximum power point tracking reference voltage for the weak energy management circuit; The power management unit also includes a super capacitor, which is connected to the DC output end of the weak energy management circuit and is responsible for storing the DC energy of constant voltage output by the weak energy management circuit.

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