JP3385472B2 - Rectenna and how to increase rectenna power - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectenna that is used for microwave energy transmission and rectifies and outputs the received microwaves, and a method for increasing the power of the rectenna.

[0002]

2. Description of the Related Art Conventionally, the technical development of microwave wireless power transmission for converting electric energy into microwave and transmitting the power wirelessly has been advanced. This technology realizes wireless power transmission to mountain peaks and remote islands on the ground, and power transmission to other satellites in outer space.

To date, power transmission experiments have been carried out for mobile objects such as model airplanes and airships, and their application to inspection robots moving in gas pipes is also considered. When the purpose is to supply power to a robot, power transmission with an increased power density is assumed, and it is essential to increase the power of one rectenna element, which is a microwave power receiving and rectifying element.

Most of the conventional studies on increasing the power of rectennas have been carried out by increasing the power of the diodes used in the rectenna rectifier circuit by connecting a large number of diodes in series / parallel. This is the method that was designed.

However, in the former method, the performance of the rectenna largely depends on the performance of the diode. In the latter method, as the number of connected diodes increases, the efficiency decreases and the cost increases.

[0006]

As described above, in the conventional technology for increasing the power in the rectenna, there are problems that the performance depends on the diode, the efficiency is lowered, and the cost is increased.

[0007] Therefore, an object of the present invention is to provide a rectenna capable of efficiently increasing the power consumption at low cost regardless of the performance of the diode, and a method of increasing the power consumption thereof.

[0008]

In order to achieve the above object, a rectenna according to the present invention is provided with a plurality of transmission lines for receiving received microwave power only by a microstrip line.
Power distribution circuit section for equipartition the road (no absorption resistance Will
(Corresponding to a Kinson type power distribution circuit) and a plurality of rectification circuit units that are connected to each of the plurality of transmission lines and that rectify and smooth output the power-distributed microwaves.

[0009]

The rectifying circuit section has a rectifying circuit in which a distribution microwave input end and a reference potential line are connected via a rectifying element, and a line width λ / 4 whose one end is connected to the distribution microwave input end. And a filter circuit in which a capacitive element is connected to the other end of the transmission line (where λ is the effective wavelength of the microwave).

It is characterized in that a capacitor is interposed in front of the distribution output terminal of the power distribution circuit section.

In the rectenna having the above-mentioned configuration, the number of distributions of the power distribution circuit section is selected according to the input power of the received microwave.

That is, the present invention provides a rectenna capable of receiving and rectifying a large amount of electric power which has never existed before by combining a power distribution circuit unit and a rectification circuit unit.

The rectenna according to the present invention is used for microwave energy transmission, and the microwave-DC conversion efficiency is the most important, unlike that for communication. The power distribution circuit unit used in communication or the like is a Wilkinson type power distribution circuit with an absorption resistance. The absorption resistance absorbs the reflection due to the mismatch on the output side and keeps the even distribution of electric power. In the rectenna, however, the electric power is rectified and becomes direct current, so that the reflection of microwave is extremely small. Therefore, to save space, the Wilkinson type power distribution circuit with no absorption resistance was connected to the rectifier circuit to increase the power of the rectenna. The loss of the power distribution circuit unit manufactured for the present invention was 5 to 7%.

This power distribution circuit section is divided into 2 distributions, 4 distributions, and 8 distributions.
By increasing the distribution and the number of distributions, it is possible to easily configure a rectenna having a maximum microwave-DC conversion efficiency with various input powers. The rectenna has the maximum microwave-to-DC conversion efficiency at a certain value with respect to the input microwave intensity, but it has the characteristic that the efficiency decreases when the microwave is strong or weak at the peak. Further, the microwave energy beam has a strong central intensity, and the intensity becomes weaker as the distance from the center increases. Therefore, it is possible to construct an array type rectenna that exhibits the maximum performance at all power densities by changing only the distribution number with the same rectenna for the basic design with the same performance.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the structure of a rectenna according to the present invention. In this rectenna, a microwave integrated circuit is formed by forming a microstrip line on a dielectric substrate having a ground layer formed on the back surface. Figure 1
The substrate is omitted and only the shape of the microstrip line is shown.

In FIG. 1, A is a microwave input end to which the microwave received by an antenna part (not shown) is input, and the microwave input to this input end A is first supplied to the power distribution circuit part. .

This power distribution circuit section is constructed of a Wilkinson type without absorption resistance, and the supplied microwaves are equally distributed to the two transmission lines, and each distribution output is equally distributed to the two transmission lines. Then, the microwaves are equally distributed to the four transmission lines. The Wilkinson type has a feature that a signal is distributed to an output end without loss by passing the signal through a λ / 4 line (λ is an effective wavelength of an input microwave) having a characteristic impedance that satisfies a certain condition.

The microwaves equally distributed to each transmission line are supplied to the rectification circuit section after the direct current component is cut by the chip capacitor C arranged in series with the transmission line.
The chip capacitor C also has a function of preventing the DC power obtained in the rectifying circuit unit at the subsequent stage from flowing back to the power receiving antenna unit.

The rectifier circuit section includes a rectifier circuit and a filter circuit.

The rectifier circuit has an input terminal (chip capacitor C
Is connected to the ground line G through one or more (two series and two parallel in the figure) diodes D,
Rectify the distributed microwaves. The number of diodes D is arbitrarily selected according to the performance of the diodes.

In the filter circuit, one end of the λ / 4 line E is connected to the input end, and the other end has an open stub of about λ / 8 (the line width is widened to form a capacitance with the ground layer on the back surface of the substrate). The capacitor rectification circuit (F) is connected to the rectification circuit to smooth the microwave rectification output of the rectification circuit to obtain a constant DC power. In the present embodiment, a filter having a λ / 4 line and a λ / 8 open stub F is connected in two stages in series.

The end of the transmission line drawn out from the open stub F is referred to as the output end B. The DC power obtained in each distribution system is taken out from the output terminal B, appropriately combined and used as the output power.

Here, in the rectenna having the above structure, the input microwaves are equally distributed to the four transmission lines, but the number of distributions can be set arbitrarily. FIG. 2 shows the measurement results of the microwave input power-DC (RF-DC) conversion efficiency when the distribution numbers are 1, 2, 4, and 8.

In FIG. 2, a is the case of a rectenna having a distribution number of 1 (single unit), and the maximum conversion efficiency of 77.5% was obtained when the input power was 1.3 W. At this time, the characteristic impedance was 250Ω and the output power was 1.0W. b is the case of a rectenna having a distribution number of 2, and a maximum conversion efficiency of 75.7% was obtained with an input power of 1.5 W on one line. At this time, the characteristic impedance was 150Ω and the combined output power was 2.1W. c is the case of a rectenna with a distribution number of 4, and a maximum conversion efficiency of 73.0% was obtained with an input power of 4.5 W on one line. At this time, the characteristic impedance was 70Ω and the combined output power was 4.1W. d is the case of a rectenna with a distribution number of 8, and a maximum conversion efficiency of 68.6% was obtained with an input power of 11.5 W on one line. At this time, the characteristic impedance was 30Ω and the combined output power was 6.7W.

As is clear from the measurement result of FIG. 2, the optimum input power differs depending on the distribution number. From this, it is understood that the rectenna having the optimum conversion efficiency can be realized by appropriately selecting the distribution number for various input powers. In this case, it is less costly than changing the number of diodes to obtain the same effect.

[0028]

As described above, according to the present invention, it is possible to provide a rectenna and a method for increasing the power consumption of the rectenna, which can efficiently realize the large power consumption at low cost regardless of the performance of the diode.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a rectenna according to the present invention.

FIG. 2 is a characteristic diagram showing a measurement result of microwave-DC conversion efficiency for each distribution number of a rectenna according to the present invention.

[Explanation of symbols]

A: Power receiving microwave input terminal B: DC power output end C ... Chip capacitor D ... Diode E ... λ / 4 line F ... Open stub G: Ground track

─────────────────────────────────────────────────── --Continued front page (56) Reference JP 2000-278887 (JP, A) JP 5-335811 (JP, A) JP 3-55902 (JP, A) Rectenna for microwave power transmission Experimental Study on Connection Method of Devices, IEICE Transactions on Electronics B, Japan, Electronic Information and Communication, July 1999, Vol. J82-B No. 7,1374-1383 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02J 17/00 H01P 1/20-1/219 H01P 5/12

Claims (5)

(57) [Claims] 1. The microwave of the received microwave power
A power distribution circuit unit that equally distributes to a plurality of transmission lines only by strip lines, and a plurality of rectification circuit units that are respectively connected to the plurality of transmission lines and that rectify and smooth output the power-distributed microwaves. A rectenna characterized by comprising: 2. The power distribution circuit unit comprises a λ / 4 line (λ
Is an equal distribution of 2 lines only by the effective wavelength of the microwave)
The rectenna according to claim 1 , further comprising n (n is a natural number) stages of circuits . 3. The rectifier circuit section comprises a rectifier circuit in which a distribution microwave input end and a reference potential line are connected via a rectifying element, and a line width λ whose one end is connected to the distribution microwave input end. 2. The rectenna according to claim 1, further comprising a filter circuit in which a capacitive element is connected to the other end of the transmission line of / 4 (λ is the effective wavelength of the microwave). 4. The rectenna according to claim 1, wherein a capacitor is provided in front of a distribution output end of the power distribution circuit section. 5. The received microwave power is supplied to a microwave.
A power distribution circuit unit that equally distributes to a plurality of transmission lines only by strip lines, and a plurality of rectification circuit units that are provided in each of the plurality of transmission lines and that rectify and smooth output the power-distributed microwaves. The method for increasing the power of a rectenna according to claim 1, wherein the number of distributions of the power distribution circuit unit is selected according to the input power of the received microwave.