JP7041859B2 - Rectenna device - Google Patents

Description

The present invention relates to a rectenna device that receives electric power via electromagnetic waves.

A rectenna device is used to obtain electric power by receiving high-frequency electric power such as microwaves transmitted from a transmitter on the ground or in the air by a moving body such as an airplane, an automobile, or a ship.

In particular, in order to prolong the driving time of the projectile, it is effective to increase the capacity of the mounted battery, but the weight of the battery also increases accordingly, so that it is not a fundamental solution. Further, since a connection portion is indispensable for connecting the battery to the circuit, this connection portion becomes a failure factor and is a problem in improving reliability in an unmanned operation system.

As a charging system suitable for an unmanned operation system, for example, Non-Patent Document 1 shows a rectenna device having a front-back integrated structure in which an aramid honeycomb material is used as a substrate and a structural member and a rectifier circuit is provided in the immediate vicinity of the back surface of a patch antenna. ing. By using such microwave power transmission technology, it is possible to configure a wireless power transfer system that does not require a connection portion.

Further, Non-Patent Document 2 discloses a rectenna device using a microstrip antenna having a balanced two-wire configuration and a microstrip line.

Further, Patent Document 1 shows an antenna having a circular microstrip configuration that can be used as a rectenna.

Japanese Unexamined Patent Publication No. 2003-78338

Ozawa, Tanaka "Application of microwave power transmission technology to electric airplanes" IHI Technical Report Vol.55 No.1 (2015) "Rectenna Technology Program: Ultra Light 2.45 GHz Rectenna and 20 GHz Rectenna", by William C. Brown, Prepared for National Aeronautics and Space Administration, NASA Lewis Research Center, Contract NAS3-22764.

According to the microwave power transmission technology shown in Non-Patent Document 1, 1 g / W having a very light mass-output power ratio can be obtained as a rectenna operating in the 5.8 GHz band.

However, such a conventional rectenna device has basically the same cross-sectional structure as a device used on the ground, and is intended to reduce the weight of its constituent material in order to apply it to a projectile. rice field. In other words, a lightweight product with high heat dissipation suitable for projectile applications has not yet been provided. For example, in the case of the rectenna device having a microstrip configuration shown in Patent Document 1, since the antenna and the rectifier circuit are composed of separate substrates, [antenna substrate]-[adhesive sheet]-[honeycomb substrate] -[Adhesive sheet]-[Circuit board], which is a multi-layer structure. In this case, a honeycomb structural material is used to reduce the weight of the antenna, but since an adhesive sheet is required for adhesion to the dielectric substrate, there is a problem that the weight increases and the manufacturing process becomes complicated. Further, in terms of heat dissipation, heat dissipation is poor because the ground plate of the rectifier circuit that dissipates heat generated by the loss of the rectifier circuit is located at an intermediate position in the cross section of the rectenna. Further, if the rectifier circuit board is made thin for weight reduction, there is a problem that the conductor loss of the microstrip line increases and the output decreases.

Further, in the balanced two-wire configuration shown in Non-Patent Document 2, the antenna and the rectifier circuit can be configured on the same surface, but there is a problem that the antenna and the rectifier circuit are not suitable for heat dissipation because the conductor area is small.

As described above, a rectenna device that is lightweight, has high heat dissipation, and is easy to manufacture has not yet been provided.

Therefore, an object of the present invention is to provide a rectenna device that is lightweight, has high heat dissipation, and is easy to manufacture.

The rectenna device of the present invention is
It includes a first dielectric layer, a first conductor layer in contact with the first dielectric layer, and a second conductor layer separated in parallel from the first dielectric layer via the second dielectric layer. The first conductor layer includes a coplanar waveguide composed of a main line and a ground conductor pattern, a coplanar waveguide feeding patch antenna connected to the main line, and an input filter pattern and an output filter connected to the main line. A rectifying element having a pattern and connecting between the main line and the ground conductor pattern between the input filter pattern and the output filter pattern is provided on the surface of the first conductor layer.

In the conventional microstrip structure, the transmission loss increases as the dielectric substrate becomes thinner, but in the above structure, the main line and the circuit connected to the main line form a coplanar waveguide structure, so that the loss is irrelevant. In addition, it is possible to reduce the weight by making it thinner. Further, in the conventional structure in which the microstrip antenna and the rectifier circuit are attached, the heat dissipation surface is located inside from the outside air contact surface to a plurality of layers, whereas in the above structure, the main line of the Coplanar waveguide is used. And since the ground conductor pattern is arranged on the surface in contact with the outside air, the heat dissipation efficiency is very high.

According to the present invention, a rectenna device having a high mass-output power ratio can be obtained by being lightweight and having high heat dissipation. Moreover, since the structure is simple, a rectenna device that is easy to manufacture can be obtained. Further, by providing the rectenna device having a high mass-output power ratio, for example, the mass ratio of the power receiving unit to the total mass of the projectile becomes small, so that the weight ratio of other loads on the projectile can be increased.

1 (A) is a plan view of the rectenna device 100 according to the embodiment of the present invention, and FIG. 1 (B) is a cross-sectional view thereof. FIG. 2A is a plan view of the antenna portion of the rectenna device 100 according to the embodiment of the present invention, and FIG. 2B is a cross-sectional view of the portion. FIG. 3 is a configuration diagram showing the rectenna device 100 shown in FIGS. 1 (A) and 1 (B) in blocks according to function. FIG. 4 is a block diagram of a rectenna device including a plurality of rectennas arranged in an array. FIG. 5 is a block diagram of a system with a plurality of rectennas arranged in an array. FIG. 6 is a plan view of the rectenna device 101 in which a plurality of rectennas arranged in an array are connected. FIG. 7 is a plan view of the rectenna device 102 in which a plurality of rectennas arranged in an array are connected. FIG. 8 is a plan view of the rectenna device 103 in which the connection structure between the patch antenna and the main line is different from that shown in FIG. FIG. 9 is a plan view of the rectenna device 104 in which the connection structure between the patch antenna and the main line is different from that shown in FIG.

1 (A) is a plan view of the rectenna device 100 according to the embodiment of the present invention, and FIG. 1 (B) is a cross-sectional view thereof.

The rectenna device 100 includes a first circuit board 10, a second circuit board 20, and a spacer 31.

The first circuit board 10 is a board in which a copper foil 12 is bonded to an insulator base material 11, and is, for example, a glass epoxy board (FR-4 board). The copper foil 12 is patterned in a predetermined pattern described later.

The second circuit board 20 is a board in which a copper foil 22 is bonded to an insulator base material 21, and is, for example, a glass epoxy board (FR-4 board). The copper foil 22 is not specially patterned. In other words, it is a copper foil on the entire surface.

The spacer 31 is kept parallel between the first circuit board 10 and the second circuit board 20 at regular intervals to secure a gap 30. The spacer 31 is made of a cross-shaped or frame-shaped low dielectric constant insulator material sandwiched between the first circuit board 10 and the second circuit board 20.

The insulator base material 11 of the first circuit board 10 corresponds to the "first dielectric layer" of the present invention, and the copper foil 12 of the first circuit board 10 corresponds to the "first conductor layer" of the present invention. Further, the copper foil 22 of the second circuit board 20 corresponds to the "second conductor layer" of the present invention. The void 30 corresponds to the "second dielectric layer" of the present invention.

As shown in FIG. 1A, the copper foil 12 of the first circuit board 10 is composed of a main line SL and a ground conductor pattern GND to form a coplanar waveguide. Further, the copper foil 12 is formed with a circular patch P having notches N facing in the 45-degree direction. The main line SL is connected to the patch P. The patch P, the ground conductor pattern GND, the insulator base material 11 and the void 30 constitute a Coplanar waveguide feeding patch antenna PA. The operation of this coplanar waveguide feeding patch antenna (hereinafter, simply referred to as “patch antenna”) PA will be described in detail later.

The input filter pattern F1 and the output filter pattern F2 are connected to the main line SL. The input filter pattern F1 is composed of stubs ST11 and ST12 protruding in the orthogonal direction from the main line SL. Further, the output filter pattern F2 is composed of stubs ST21 and ST22 protruding in the orthogonal direction from the main line SL. These stubs ST11, ST12, ST21, and ST22 are all 1/4 wavelength open stubs.

On the surface of the first circuit board 10, a rectifying element 3 connected between the input filter pattern F1 and the output filter pattern F2 between the main line SL and the ground conductor pattern GND is mounted. The rectifying element 3 is, for example, a Schottky barrier diode.

The rectenna device 100 receives electromagnetic waves incident from the upper surface in the directions shown in FIGS. 1 (A) and 1 (B). At that time, the copper foil 22 as the second conductor layer reflects the electromagnetic wave received from the upper surface toward the upper surface, and enhances the gain of the patch antenna PA. The larger the gap 30, the larger the volume of the antenna, and the higher the gain of the antenna. Since the weight ratio of the spacer 31 in the entire rectenna device 100 is small, even if the spacer 31 is increased in order to increase the gap 30, the weight increase of the entire rectenna device 100 is small.

2 (A) is a plan view of the patch antenna PA portion, and FIG. 2 (B) is a cross-sectional view of the BB portion in FIG. 2 (A).

As shown in FIG. 2B, the gap between the patch P and the ground conductor pattern GND is represented by Gap, and the distance between the patch P and the ground conductor pattern GND facing the patch P is represented by d.
When the above interval d is about 0.03 wavelength, if Gap> 2d, it acts as a patch antenna (microstrip antenna). Further, if there is no ground conductor pattern GND facing the patch P, it acts as an omnidirectional slot antenna (Folded dipole).

In this embodiment, in order to improve the antenna radiation efficiency while maintaining the characteristics of the Coplanar waveguide, the interval d is set to about 0.25 wavelength and G << d. The operation is assumed to be similar to that of a slot antenna, but here it is called a "coplanar waveguide feeding patch antenna" in the sense of "an antenna having a patch-shaped radiating element fed from a coplanar waveguide".

FIG. 3 is a configuration diagram showing the rectenna device 100 shown in FIGS. 1 (A) and 1 (B) in blocks according to function. An input filter based on the input filter pattern F1, a rectifying element 3 and an output filter based on the output filter pattern F2 are longitudinally connected between the antenna by the patch antenna PA and the DC load.

The input filter F1 is a low frequency pass filter or a band pass filter that passes only the received frequency (frequency of the electromagnetic wave transmitted from the transmitter). The operation of this input filter F1 is as follows.

-The harmonics generated by the non-linear voltage-current characteristics of the rectifying element 3 are cut off, and the re-radiation of the harmonics from the patch antenna PA is suppressed.

-Match the impedance of the patch antenna PA and the rectifying element 3.

That is, the impedance seen from the rectifying element 3 on the input filter F1 side is the impedance of the patch antenna PA at the received frequency, and is substantially open at the harmonic frequency of the received frequency.

The output filter F2 is a low frequency pass filter or a band blocking filter that passes only a DC component. The operation of this output filter F2 is as follows.

-Cut off the power receiving frequency component and its harmonic component to the DC load side.

-Match the impedance of the rectifying element 3 and the DC load.

That is, the impedance seen from the rectifying element 3 on the output filter F2 side is the impedance of the DC load in direct current, and is substantially short-circuited at the even-order harmonic frequency of the received frequency and substantially at the odd-order harmonic frequency of the received frequency. It is open.

The rectifying element 3 is provided between the input filter F1 and the output filter F2. The distance between the rectifying element 3 and the output filter F2 is a length corresponding to or near 1/4 wavelength of the fundamental frequency of the RF signal. The fundamental wave of the input RF signal is totally reflected by the output filter, and the standing wave becomes an antinode at the connection position of the rectifying element 3. Further, the impedance seen from the output filter side from the rectifying element 3 looks open for the odd harmonics of 3f, 5f, ..., And short for the even harmonics of 2f, 4f, .... A half-wave double current flows through the rectifying element 3 due to the synthesis of the harmonics, and the voltage doubler rectification operation is performed.

The second circuit board 20 is only used to hold the copper foil 22 as the second conductor layer. The copper foil 22 may be on the lower surface side of the insulator base material 21. Further, instead of the second circuit board 20, a metal mesh or a metal foil that acts as a reflector may be provided.

Here, the features of the rectenna device of the present embodiment are listed in comparison with the rectenna device of the comparative example. In the rectenna device of the comparative example, the transmission line includes a rectenna having a microstrip line structure.

[Main parameters of characteristic impedance]
In the rectenna device of the comparative example, the capacitance generated between the main line and the ground conductor pattern formed on the opposite surface of the main line is the main parameter that determines the characteristic impedance. Therefore, the thickness of the dielectric layer cannot be arbitrarily reduced. On the other hand, in the rectenna device of the present embodiment, the capacitance generated between the main line SL and the ground conductor pattern GND on the same surface as the main line SL is the main parameter that determines the characteristic impedance, and is the dielectric layer. Since it is not affected by the thickness of the track, it can be made thinner as a whole.

[Calculation example of 50Ω line width]
Assuming that the thickness of the dielectric layer is 0.1 mm, the relative permittivity of the dielectric layer is 3.2, and the thickness of the conductor pattern (copper foil) is 18 μm, in the rectener device of the comparative example, the width of the main line is used to form a 50Ω line. Is 0.22 mm, whereas in the rectener device of the present embodiment, if the gap between the main line and the ground conductor pattern is 0.15 mm, the line width of the main line is 3 mm. In this way, the line width of the main line can be increased. That is, when the thickness of the dielectric substrate is reduced, the line width is also narrowed in the microstrip line, which causes an increase in conductor loss, but in the Coplanar waveguide, the line width is adjusted by adjusting the gap between the main line and the ground conductor pattern. Since it is defined more widely, it is possible to construct a circuit having a lower loss than that of a microstrip line.

[Arrangement of rectifier circuit]
In the rectenna device of the comparative example, the substrate on which the antenna is formed and the substrate on which the rectifier circuit is formed are bonded together, whereas in the rectenna device of the present embodiment, the rectifier circuit is formed on the antenna forming surface which is the heat dissipation surface of the substrate. Because it is integrally configured, the overall thickness and weight can be reduced.

[Arrangement of ground conductor pattern]
In the rectenna device of the comparative example, the ground conductor pattern is arranged in the center of the multilayer board, whereas in the rectenna device of the present embodiment, the ground conductor pattern is placed on the antenna forming surface of the board, which is the heat dissipation surface in contact with the outside air. Since it is formed, heat dissipation is improved. That is, heat is generated by the conductor loss of the Coplanar waveguide and the loss in the rectifier circuit by the input filter pattern F1, the output filter pattern F2 and the rectifier element 3, but since these heat generating portions are exposed to the outside air, heat is dissipated. Very efficient. Further, since it is not necessary to use a honeycomb structural material or an adhesive sheet for adhering to the dielectric substrate, the weight is reduced as a whole and the manufacturing is easy.

[Rectifier element connection structure]
In the rectenna device of the comparative example, it is necessary to provide a through hole in order to connect the rectifying element to the ground conductor pattern, whereas in the rectenna device of the present embodiment, the through hole is unnecessary.

Next, an example of a rectenna device including a plurality of rectennas will be shown.

FIG. 4 is a block diagram of a rectenna device in which a plurality of rectennas arranged in an array are connected. In FIGS. 1A and 1B, one unit of the rectenna device is shown, but as shown in FIG. 4, the rectenna array system is configured by connecting the outputs of the rectifier circuits of a plurality of rectenna devices. do.

In FIG. 4, a plurality of sets of rectenna rectifier circuit outputs connected in parallel are configured, and the plurality of sets are connected in series and connected to the rectenna control circuit. The rectenna control circuit controls the input impedance of the rectenna control circuit so that each rectenna operates with the highest efficiency.

FIG. 5 is a block diagram of a system with a plurality of rectennas arranged in an array. Unlike the example shown in FIG. 4, a plurality of sets of rectenna rectifier circuit outputs connected in series are configured, and the plurality of sets are connected in parallel.

As described above, how to connect a plurality of rectennas varies, but the connection structure may be appropriately defined so that each rectenna operates with the highest efficiency.

FIG. 6 is a plan view of the rectenna device 101 in which a plurality of rectennas arranged in an array are connected. Although the cross-sectional view is omitted, the basic structure is as shown in FIG. 1 (B).

In the rectenna device 101, the coplanar waveguide is composed of the main line SL formed on the upper surface of the first circuit board 10 and the ground conductor pattern GND. Further, the rectenna device 101 includes a plurality of coplanar waveguide feeding patch antennas PA including a circular patch P, a ground conductor pattern GND, and a ground conductor pattern facing the patch P.

The input filter pattern F1 and the output filter pattern F2 are connected to the main line SL. The input filter pattern F1 is composed of stubs ST11, ST12, ST13, and ST14 protruding in the orthogonal direction from the main line SL. Further, the output filter pattern F2 is composed of stubs ST21 and ST22 protruding in the orthogonal direction from the main line SL.

On the surface of the first circuit board 10, a rectifying element 3 connected between the input filter pattern F1 and the output filter pattern F2 between the main line SL and the ground conductor pattern GND is mounted.

One rectenna is composed of the patch antenna PA, the input filter pattern F1, the rectifying element 3, and the output filter pattern F2. The electrical length L between the output filter F2, which is a short-circuit point of the receiving frequency (fundamental wave), and the patch P of the adjacent patch antenna PA is designed to be 1/4 wavelength. As a result, the impedance looking into the output filter F2 side from the adjacent patch antenna PA becomes infinite (open). Therefore, it is possible to superimpose a DC voltage on the Coplanar waveguide.

In this way, the rectennas can be connected in series by connecting the output of the output filter F2 of the rectenna to the patch P of the adjacent rectennas.

The output of each rectenna is connected to the DC bus line Bus provided at the end of the first circuit board 10. In the range shown in FIG. 6, two rectennas connected in series are connected in parallel to the DC bus line Bus.

It should be noted that, for example, by configuring the rectified voltage to be smoothed by the open stub without mounting a chip capacitor, a rectenna with low loss and high power conversion efficiency is configured. Further, since it is substantially composed of only the conductor pattern formed on the heat radiation surface side, a lighter and thinner rectenna device is configured. Further, since the chip capacitor and its soldering are not required, it is excellent in terms of cost, manufacturability, and reliability.

In this way, a rectenna device in which a plurality of rectennas are arrayed in a two-dimensional plane can be configured.

FIG. 7 is a plan view of the rectenna device 102 whose structure of the patch antenna is different from that shown in FIG. The patch antenna PA included in the rectenna device 102 is a linearly polarized Coplanar waveguide feeding patch antenna having a rectangular patch P. Other configurations are the same as those of the rectenna device 101 shown in FIG. The polarization direction in the rectenna device 102 is the short side direction of the first circuit board 10. In this way, the rectenna device provided with the linearly polarized patch antenna can be similarly arrayed.

FIG. 8 is a plan view of the rectenna device 103 in which a plurality of rectennas arranged in an array are connected. The connection structure between the patch antenna and the main line is different from that of the rectenna device 101 shown in FIG. In the example shown in FIG. 8, a plurality of patch antenna PAs are pulled out from predetermined positions of the continuous main line SL. That is, for each patch antenna PA, the feeding line drawn from each patch P is connected to the main line SL.

One rectenna is composed of the patch antenna PA, the input filter pattern F1, the rectifying element 3, and the output filter pattern F2. The electrical length L between the output filter F2, which is the short-circuit point of the received frequency (fundamental wave), and the connection portion of the patch P of the adjacent patch antenna PA to the main line SL is designed to be 1/4 wavelength. ing. As a result, the impedance looking into the output filter F2 side from the feeding line of the adjacent patch antenna PA becomes infinite (open). Other configurations are the same as those of the rectenna device 101 shown in FIG.

FIG. 9 is a plan view of the rectenna device 104 in which a plurality of rectennas arranged in an array are connected. The connection structure between the patch antenna and the main line is different from that of the rectenna device 102 shown in FIG. 7. In the example shown in FIG. 9, a plurality of patch antenna PAs are pulled out from predetermined positions of the continuous main line SL. The patch antenna PA included in the rectenna device 104 is a linearly polarized Coplanar waveguide feeding patch antenna having a rectangular patch P. The polarization direction in the rectenna device 104 is the short side direction of the first circuit board 10. In this way, the rectenna device provided with the linearly polarized patch antenna can be similarly arrayed.

In the rectenna device 103 shown in FIG. 8 and the rectenna device 104 shown in FIG. 9, since the main line SL is not connected to the radiation portion of the patch P, the influence of the antenna characteristics by the connection of the main line SL to the patch P is small. Therefore, a general-purpose design becomes possible.

Finally, the description of the embodiments described above is exemplary in all respects and not restrictive. Modifications and changes can be made as appropriate for those skilled in the art. For example, in the examples shown in FIGS. 1A and 1B, the space between the first circuit board 10 and the second circuit board 20 may be filled with a foamable resin sheet having a small specific weight. Further, the copper foil as the second conductor layer may be attached to the lower surface of the foamable resin sheet without using the second circuit board 20. Further, a metal mesh or a metal foil may be provided without providing the resin sheet.

Bus ... DC bus line F1 ... Input filter pattern F2 ... Output filter pattern GND ... Ground conductor pattern N ... Notch P ... Patch PA ... Coplanar waveguide feeding patch antenna SL ... Main line ST11, ST12, ST13, ST14 ... Stub ST21, ST22 ... Stub 3 ... Rectifying element 10 ... First circuit board 11 ... Insulator base material (first dielectric layer)
12 ... Copper foil (first conductor layer)
20 ... Second circuit board 21 ... Insulator base material 22 ... Copper foil (second conductor layer)
30 ... Void (second dielectric layer)
31 ... Spacer 100-104 ... Rectenna device

Claims (4)

A first dielectric layer, a first conductor layer in contact with the first dielectric layer, and a second conductor layer separated in parallel from the first dielectric layer via a second dielectric layer which is a gap are provided. Prepare,
The first conductor layer includes a coplanar waveguide composed of a main line and a ground conductor pattern, a coplanar waveguide feeding patch antenna connected to the main line, and an input filter pattern and an output connected to the main line. With a filter pattern,
On the surface of the first conductor layer, a rectifying element connected between the input filter pattern and the output filter pattern and between the main line and the ground conductor pattern is provided .
The gap between the patch of the Coplanar waveguide feeding patch antenna and the ground conductor pattern is smaller than the distance between the patch and the second conductor layer facing the patch.
The distance between the patch and the second conductor layer facing the patch is a quarter effective wavelength .
A rectenna device that features that. The rectenna device according to claim 1, wherein the first dielectric layer is an insulator base material of a first circuit board, and the first conductor layer is a copper foil of the first circuit board. The rectenna device according to claim 2, wherein the second conductor layer is a copper foil of a second circuit board. The rectenna apparatus according to any one of claims 1 to 3, further comprising a spacer for maintaining a distance between the first dielectric layer and the second conductor layer.

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