JP3817715B2 - Microwave / DC power converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microwave / direct current power (DC) converter using a high-speed cyclotron wave of an electron stream. This microwave / DC power converter can be used as a power receiving device in a microwave energy transmission system.
[0002]
[Prior art]
In recent decades, new problems have arisen in realizing wireless power transmission (WPT). That is, it is a problem related to reverse conversion of high-power microwave energy into direct current energy. However, there is no doubt that microwave technology will find a wide range of applications in the future in this field.
[0003]
Well-known rectennas with Schottky diodes have played a major role in realizing the possibility of highly efficient microwave radio transmission. However, this rectenna does not seem to be effective when trying to implement a high-power wireless transmission system on an industrial scale in the future. This is because of the following problems.
• The output level is low for a single rectenna element.
-The output voltage is low, so it is necessary to connect a diode in series.
・ There is a danger that it is likely to be overloaded even with relatively low levels of microwaves and direct current, and the possibility of damage is high.
[0004]
In industrial scale energy systems, high power and high voltage devices are always required to reduce losses and increase reliability.
[0005]
FIG. 3A is a schematic configuration diagram of a conventional cyclotron / microwave converter (CWC) (Vladimir A. Vanke, et al., “Cyclotron Wave Converter of Microwaves into DC”, IEICE Trans. Electron., Vol. E81-C, No. 7, July, 1998, p. 1136). The CWC 30 includes an electron gun 31, a microwave cavity 32, and a collector 33 arranged along the z-axis. A microwave cavity 32, usually called a Cuccia coupler, contains a reaction space 35 and is placed in a uniform static magnetic field having a magnetic flux density B1 in the z direction by an external static magnetic field device (not shown). The conversion region 34 between the microwave cavity 32 and the collector 33 is placed in another external static magnetic field having a magnetic flux density B2 in the -z direction (FIG. 3B).
[0006]
When the microwave power P having the frequency F is input to the microwave cavity 32, the microwave power P induces an orthogonal electric field that changes at the frequency F in the reaction space 35 of the microwave cavity 32. When an electron stream is generated by the electron gun 31 and the electron stream is sent to the center of the reaction space 35 by the electron lens, the electron stream has a frequency F (which is equal to the cyclotron frequency Fc) by the orthogonal electric field induced by the microwave. Perform high-speed cyclotron rotation.
[0007]
In the conversion region 34, the rotating electron flow receives an additional Lorentz force due to the radial component of the reversing static magnetic field (z1 <z <z2 in FIG. 3B), and the pitch angle of the velocity vector is changed from the rotation direction to the z axis. Increase the velocity component in the z-axis direction. Thus, the electron flow shifts to a spiral motion, and the energy of the cyclotron wave is converted to the energy of a synchronous wave having the same polarity.
[0008]
The accelerated electron stream 36 enters the collector 33, where its kinetic energy is taken out by the load resistor 37 as DC current energy.
[0009]
The cyclotron / microwave converter has a potentially high output capability, and has already been tested with an output of about 10kW. This is already well known in various publications. See, for example, US Pat. No. 3,462,636 and Russian Patent 2119691.
[0010]
[Problems to be solved by the invention]
However, this type of cyclotron to microwave converter requires a high intensity static magnetic field corresponding to a cyclotron with a frequency equal to the frequency of the external microwave source. Such a requirement causes a great technical problem especially in the short centimeter wave and millimeter wave bands.
[0011]
The present invention provides a cyclotron / microwave converter that does not require a large-scale static magnetic field apparatus, that is, a microwave / DC power converter.
[0012]
[Means for Solving the Problems]
The present invention makes it possible to reduce the magnetic field strength to half or less by using two microwave cavities each having a uniform electric field and a multipole electric field in the reaction space.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Specifically, the microwave / DC power converter according to the present invention imparts rotational motion to an electron flow by a microwave supplied from the outside in a reaction space, and the kinetic energy of the electron flow is converted to direct current in a current converter. In the microwave / DC power conversion device that converts the electric current to take out, the reaction space includes 2 · n (n = 2, 3,...) Electrodes arranged in parallel and axisymmetrically around the central axis. It is characterized by this.
[0014]
More specifically,
a) an electron source that emits electrons;
b) a first reactor that gives initial rotational motion to electrons sent from an electron source and sends them to the following multipole reactor;
c) Consists of 2 · n (n = 2, 3, ...) electrodes arranged in parallel and axisymmetric about the central axis, and gives cyclotron motion to the electrons by the energy of microwaves supplied from outside A multipole reactor;
d) a motion transducer that converts the rotational motion of electrons leaving the multipole reactor into axial motion;
e) a current transducer for extracting a direct current from an electron stream having axial kinetic energy;
Shall be provided.
[0015]
【Example】
A cyclotron / microwave converter (CWC) as an embodiment of the microwave / DC power converter according to the present invention will be described with reference to FIGS. FIGS. 1A and 1B are a schematic configuration diagram of the CWC of this embodiment and a magnetic field intensity distribution diagram in the z-axis direction, and the positions in the z-axis direction in both diagrams correspond to each other. In FIG. 1B, B (z) is a z-direction component of magnetic field induction on the z-axis, and Fc is a cyclotron frequency corresponding to the value of B (z).
[0016]
The electron gun 1 generates an electron beam 2 having a circular cross section, and enters the first microwave cavity 3 along the z axis. Since no current flows through the resistor (resistor) 13 in the normal operation mode, the potential of the first microwave cavity 3 is equal to the voltage U of the voltage source 12.
[0017]
The first microwave cavity 3 has a resonance frequency that is ½ of the frequency F of the incident power microwave P. A very small part (1% or less) of the power of the incident microwave P is supplied to the first microwave cavity 3 via the power separator 6, the frequency divider 5 and the phase shifter 4. The orthogonal electric field in the reaction space of the first microwave cavity 3 causes the electron beam 2 to rotate an initial small rotation around the z axis together with a resonant uniform static magnetic field (Fc = F / 2; see FIG. 1B).
[0018]
In the reaction space of the second microwave cavity 7, four rod-shaped electrodes (quadrupole electrodes) are arranged in parallel to each other and axisymmetric with respect to the z axis. Each of these quadrupole electrodes operates at a frequency F due to the microwave P. Since the electrodes are two sets, the rotation frequency of the electron beam rotating in the reaction space surrounded by them is F / 2. It becomes. For this reason, the operating frequency of the first microwave cavity 3 is F / 2. Similarly, when 2 · n electrodes are provided in the second microwave cavity, the rotation frequency of the electron beam is F / n, and the operating frequency of the first microwave cavity is also F / n.
[0019]
Under the same magnetic field, such a quadrupole electric field (Fc = F / 2) may accelerate or decelerate the orthogonal rotation of the electron beam 2 depending on the initial phase (phase at the time of incidence). There is also. The phase shifter 4 increases the initial rotation radius of the electron beam 2, and the phase of the electron beam rotation is set to an optimum position so that the energy of the external microwave source is efficiently converted into the rotation energy around the z axis of the electron beam 2. To come.
[0020]
The same voltage U (see FIG. 1A) is also applied to the drift tube 8, but here the static magnetic field is changed in both direction and strength (REV region in FIG. 1B). The axial velocity of the rotating electron beam increases in the divergent magnetic field in this REV region. The radial component of the static magnetic field creates such a process when the rotational energy of the electron beam is converted to the additional energy of axial motion. At the same time, the motion pattern of the electron beam also changes and takes the shape of a spatial helix (the energy of the fast cyclotron wave is converted to the energy of a synchronous wave of the same polarity). Here, it should be emphasized that the optimum energy conversion in the REV region always occurs in an asymmetric reversal magnetic field regardless of the value of the CWC parameter (in FIG. 1B, the value of B2 is Smaller than the value of B1).
[0021]
After passing through the REV region, the accelerated electron beam enters the collector region 11 where the kinetic energy of the electron beam is extracted and converted to direct current (DC) energy. This energy appears at the load resistor 14. The magnetic field distribution here depends on the specific configuration of the collector 11, but usually takes the form of a decreasing field, as schematically shown by the dotted line in FIG. The additional electrode 9 is applied with a voltage by the voltage source 10 and has a potential slightly lower than the potential of the collector 11. The additional electrode 9 generates a local electric field at the orifice (small hole) of the collector 11 and prevents secondary generated electrons from coming out.
[0022]
Resistor 13 creates a simple current control system. That is, any small current flowing through the wall of the first microwave cavity 3, the second microwave cavity 7 or the drift tube 8 (caused by an overload of microwaves or direct current) greatly reduces its potential U, The current of the electron gun 1 is decreased.
[0023]
FIG. 2 shows an equivalent circuit of the first and second microwave cavities 3, 7. In FIG. 2, the reaction space of the first microwave cavity 3 is drawn along the z-axis (y = 0 plane), and the quadrupole reaction space of the second microwave cavity 7 is the z-axis (perpendicular to the paper). (Z = within a constant value plane). Both cavities 3, 7 have different resonance frequencies, different electrode arrangements, different equivalent capacitances and equivalent inductances. The first microwave cavity 3 gives the electron beam a small initial rotation with a frequency F / 2. This initial rotation is necessary to cause a reaction in the second microwave cavity 7 where the electric field is zero on the quadrupole field axis. FIG. 2 shows the moment when the potential (voltage) of the electrode is + V, −V. The cross section of the electron beam is represented by a black dot written as -e, and this position corresponds to the optimum phase (y = -x at the center of this electron beam cross section). The adjustment of the electron beam to the optimum position is performed by the phase shifter 4. The cross-sectional projection of the electron beam motion is circular, as shown by the dotted line in FIG.
[0024]
Finally, the present invention includes any embodiment conceived by those having ordinary skill in the art, and includes any variation derived from one embodiment described above. For example, a cyclotron / microwave converter having a hexapole field arrangement (ie, n = 3) in which six electrodes are arranged in parallel and axisymmetrically in the second microwave cavity is also within the scope of the present invention. included. In this case, correspondingly, the first microwave cavity operates at 1/3 the frequency of the second microwave cavity, and the magnetic field strength is only 1/3.
[0025]
【The invention's effect】
Since the microwave / DC power converter according to the present invention operates at a frequency 1 / n of the frequency of an external microwave source, it is a static magnetic field device much smaller than the conventional one operating at the same frequency. That's it. Therefore, the entire apparatus can be reduced in size and the energy conversion efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram (A) of a cyclotron / microwave converter (CWC) as an embodiment of a microwave / DC power converter according to the present invention, and an intensity distribution diagram of magnetic flux in the z-axis direction (B) ).
FIG. 2 is an equivalent circuit diagram of the first and second microwave cavities of the CWC of the embodiment.
FIG. 3 is a schematic configuration diagram (A) of a conventional CWC and a magnetic flux intensity distribution diagram (B) in the z-axis direction.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electron gun 2 ... Electron beam 3 ... 1st microwave cavity 4 ... Phase shifter 5 ... Frequency divider 6 ... Power separator 7 ... 2nd microwave cavity 8 ... Drift tube 9 ... Additional electrode 10 ... Voltage source 11 ... Collector 12 ... Voltage source 14 ... Load resistance 31 ... Electron gun 32 ... Microwave cavity 33 ... Collector 34 ... Conversion region 35 ... Reaction space 36 ... Electron flow 37 ... Load resistance

Claims (5)

In the microwave / DC power conversion device, in the reaction space, the electron stream is rotationally moved by microwaves supplied from the outside, and the kinetic energy of the electron stream is converted into a DC current by the current converter and extracted. Comprises 2 · n (n = 2, 3,...) Electrodes arranged in parallel and axisymmetrically around the central axis. a) an electron source that emits electrons;
b) a first reactor that gives initial rotational motion to electrons sent from the electron source and sends them to the following multipole reactor;
c) Equipped with 2 · n (n = 2, 3, ...) electrodes arranged in parallel and axisymmetric about the central axis, and gives cyclotron motion to the electrons by the energy of microwaves supplied from the outside A multipole reactor;
d) a motion transducer that converts the rotational motion of electrons exiting the multipole reactor into axial motion;
e) a current transducer for extracting a direct current from an electron stream having axial kinetic energy;
A microwave / DC power converter characterized by comprising: The microwave / DC power converter according to claim 2, wherein a phase controller for controlling a phase of electrons entering the multipole reactor with respect to a position of the electrode is provided in the first reactor. . 4. The microwave / DC power converter according to claim 2, wherein a resistance for preventing overcurrent is provided between the electron source, the first reactor, and the multipole reactor. 5. An additional electrode to which a voltage slightly lower than that of the current converter is applied is provided immediately before the current converter in order to prevent secondary generated electrons from exiting from the current converter. Item 5. The microwave / DC power converter according to any one of Items 2 to 4.

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