JP2012075227A - Rectenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rectenna device having high efficiency even for a high-frequency wave such as a millimeter wave or the like.SOLUTION: A rectenna device has: receiving means receiving a radio wave; rectifying means rectifying the radio wave received by the receiving means; and a resonance circuit whose impedance becomes zero for an even-order high harmonic wave of the radio wave rectified by the rectifying means, and becomes infinite for an odd-order high harmonic wave.

Description

  The present invention relates to a rectenna device.

    Since the rectenna (received rectification antenna; rectenna (abbreviation of rectifying antenna)) used for microwave wireless power transmission has been invented in the 1960s, various types have been developed and published. The rectenna is divided into a rectifier circuit portion and an antenna portion. Known rectenna rectifier circuits are roughly divided into a basic single shunt rectifier circuit and other rectifier circuits.

FIG. 14 is an equivalent circuit diagram of a rectenna device 900 using a single shunt rectifier circuit. FIG. 15 is a diagram for explaining the operation of the single shunt rectifier circuit.
As illustrated in FIG. 14, the single shunt rectifier circuit 910 includes a diode 911, a λg / 4 line 912, and a capacitor 913. Although the single shunt rectifier circuit 910 has a simple configuration, as shown in FIG. 13, the output filter composed of the λg / 4 line 912 and the capacitor 913 simultaneously performs harmonic processing and smoothing, so that full-wave rectification is possible. The theoretical efficiency is 100%.

In the rectenna apparatus, it has been proposed to increase the efficiency by using a capacitor and optimizing the λg / 4 line.
For example, in Patent Document 1, among the diode, λg / 4 line, and capacitor, which are the basic components of a single shunt rectifier circuit in the rectenna device, the λg / 4 line is in the range of λg / 22.5 to λg / 14. To optimize efficiency with weak microwave intensity.

  A capacitor essential in a single shunt rectifier circuit is theoretically required to have an infinite capacity in order to realize 100% conversion efficiency. Further, an actual capacitor operates as a capacitor up to a certain frequency, but may operate as an inductor at a higher frequency.

Moreover, in the prior art described in Patent Document 2, only one wave, for example, the second harmonic wave is cut off among the harmonic waves generated in the received signal. In order to block the second harmonic in the input stage, an open stub having a quarter of the wavelength λ ₂ of the _second harmonic is formed, and a filter is formed by a line connecting the rectifiers. Further, a rectifier and a quarter line of the fundamental wave λg are connected to the tip of the line, and a capacitor is connected to the quarter line. With this configuration, the fundamental wave reflected by the output means and returned in reverse phase is combined in the same phase and incident on the rectifying means, so that it can be rectified at a peak value that is double that of half-wave rectification. -DC conversion efficiency is improved.
Furthermore, in the prior art described in Patent Document 2, a plurality of harmonics generated from a diode are formed by forming a 1/4 open stub in accordance with each harmonic so as to block a plurality of high frequencies at the input filter unit. In contrast, the efficiency is improved by setting the impedance to zero.

JP 2007-116515 A JP-A-5-335811

However, the single-shunt rectifier circuit according to the prior art described in Patent Document 1 requires a capacitor having a large capacity, and depending on the capacitor used, the impedance increases as the frequency increases. It becomes increasingly difficult to operate as an ideal capacitor. As a result, when a high frequency such as a millimeter wave is used, there is a problem that the conversion efficiency when the received signal is converted into direct current is lowered.
In the prior art described in Patent Document 2, a plurality of harmonics generated by the rectifier is reflected to improve efficiency. However, since a capacitor is used in the output filter unit, a capacitor having a large capacity is used. is necessary. Also, depending on the capacitor used, the impedance increases with increasing frequency, and it becomes gradually difficult to operate as an ideal capacitor at high frequencies such as millimeter waves. As a result, when a high frequency such as a millimeter wave is used, there is a problem that the conversion efficiency when the received signal is converted into direct current is lowered.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a highly efficient rectenna apparatus even at a high frequency such as a microwave or a millimeter wave.

  In order to achieve the above object, the rectenna device of the present invention includes a receiving means for receiving radio waves, a rectifying means for rectifying the radio waves received by the receiving means, and an impedance of harmonics of the radio waves rectified by the rectifying means, And a resonance circuit that is zero for even-order harmonics and infinite for odd-order harmonics.

  In the rectenna apparatus according to the present invention, the resonant circuit includes a first transmission line having a length of ¼ of a wavelength λ on a transmission line of a fundamental wave of a radio wave received by the receiving unit, and the first transmission. A second transmission line having a length ¼ of wavelength λ on the transmission line of the fundamental wave of the radio wave received by the receiving means connected between the path and the load, and an output terminal of the first transmission line A plurality of first distributed constant lines connected in parallel to each other and a plurality of second distributed constant lines connected in parallel to input terminals of the second transmission line. The constant line has a transmission line length L represented by L = λ / 4m (m is an integer from 2 to n), m are different from each other, and the first distributed constant line has L = λ (2m− 1) A transmission line length L expressed by / 4m (m is an integer from 2 to n), and m is different from each other. It may be.

  Further, in the rectenna device according to the present invention, the resonance circuit includes an LC resonance circuit in which a plurality of inductors and capacitors corresponding to each harmonic of the received radio wave are connected in parallel, and the LC resonance circuit includes: One end may be grounded, and the other end may be connected to a connection point between the rectifying means and the load.

  The rectenna device according to the present invention may include a capacitor connected in parallel with the resonance circuit, connected at one end to the connection point between the resonance circuit and the load, and grounded at the other end.

  According to the present invention, the load resonance circuit is used to perform the harmonic processing so that the impedance is 0 (zero) for the even-order harmonics and ∞ (infinity) for the odd-order harmonics. A highly efficient rectenna apparatus can be realized even at high frequencies such as waves or millimeter waves.

It is an equivalent circuit diagram of the rectenna device according to the first embodiment. It is an equivalent circuit diagram of a class F amplifier circuit. It is an equivalent circuit diagram for simulation of the rectenna device according to the embodiment. FIG. 6 is an equivalent circuit diagram for simulation of a rectenna device according to the prior art. It is a figure which shows the electric current and voltage waveform of the input in the rectenna apparatus 100 based on a prior art, and the electric current and voltage waveform of an output. It is a figure showing the change of the voltage and current waveform of the diode in the rectenna apparatus 100 which concerns on a prior art, the current waveform which flows through (lambda) / 4 track | line, conversion efficiency, and a reflectance. It is a figure which shows the electric current and voltage waveform of the input in the rectenna apparatus 1a of the embodiment, and the electric current and voltage waveform of an output. It is a figure showing the voltage / current waveform of the diode in the rectenna apparatus 1a which concerns on the same embodiment, the current waveform which flows through a (lambda) / 4 line | wire, and the change of conversion efficiency and a reflectance. It is the equivalent circuit schematic of the rectenna apparatus which concerns on 2nd Embodiment. FIG. 3 is an equivalent circuit diagram for simulation of the rectenna device in the same embodiment It is a figure which shows the electric current and voltage waveform of an input in the rectenna apparatus 200a of the embodiment, and the electric current and voltage waveform of an output. It is a figure showing the change of the voltage / current waveform of the diode in the rectenna apparatus 200a which concerns on the same embodiment, the current waveform which flows through a λ / 4 line, conversion efficiency, and reflectance. It is an equivalent circuit diagram of a class F amplifier using an LC resonance circuit in the prior art. It is the equivalent circuit schematic of the rectenna apparatus using the single shunt rectifier circuit based on a prior art. It is a figure explaining operation | movement of the single shunt rectifier circuit based on a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the embodiment which concerns, A various change is possible within the range of the technical thought.

[First Embodiment]
FIG. 1 is an equivalent circuit diagram of the rectenna device according to the present embodiment.
In FIG. 1, a rectenna device 1 according to the present embodiment includes an antenna 11 (receiving means), a circulator 12, a resistor 13, a transmission line 21, a capacitor 23, a rectifying unit 30 (rectifying means), and a load resonance circuit 40 (resonance circuit). I have.
A load 51 is connected to the rectenna device 1.
As shown in FIG. 1, the difference of the present embodiment from the prior art is that a load resonance circuit 40 is provided instead of the capacitor section 140 of the prior art.

The circulator 12 is a three-terminal passive element that guides a transmission signal to a transmission unit and a reception signal to a reception unit in order to perform transmission / reception via the antenna 11. The circulator 12 outputs the signal received by the antenna 11 to the transmission path 21.
The resistor 13 has one end connected to the circulator 12 and the other end grounded. The resistor 13 replaces the output unit.

  One end of the capacitor 23 is connected to the circulator 12 via the transmission line 21, and the other end is connected to the branch 31. Reference numeral 22 represents a parasitic capacitance of the capacitor 23 when a package component is used for the capacitor 23.

The rectifying unit 30 includes a branch 31, a diode 33, and a transmission path 34. The branch 31 has an input terminal connected to the other end of the capacitor 23, one end of the output terminal connected to the cathode of the diode 33, and the other end of the output terminal connected to the λ / 4 line T ₁₁ of the load resonance circuit 40. Yes.
The diode 33 has a cathode connected to one end of the output terminal of the branch 31 and an anode grounded via the transmission line 34. Reference numeral 32 denotes a parasitic capacitance of the diode 33 when a package component is used for the diode 33.
The strip line 32 is connected in parallel with the diode 33, one end is connected to the branch 31, and the other end is connected to the transmission path 34.

The load resonant circuit 40 includes a λ / 4 line T ₁₁ (first transmission line), a λ / 4 line T ₁₂ (second transmission line), a high frequency processing (Harmonic treatment) stub (distributed constant line) T _{2 to} T _n ( A first distributed constant line), compensation stubs T ₂ ^{* to} T _n ^* (second distributed constant line), branches 41, 43, 45 and 46, and transmission lines 42 and 44. The branches 41, 43, 45 and 46 are, for example, a Wilkinson power distribution circuit or a Q-match session power distribution circuit using a microstrip line.
In FIG. 1, only the transmission lines 42 and 44 are shown, but n−1 transmission lines of the load resonance circuit 40 are provided. Stub _{T 2} are longer than stub _{T 3,} the stub _{T 3} is longer than the stub _{T 4.} Moreover, the stub _{T 2} are resonate against 2f _0, stub _{T n} is resonates with 2f _n. Incidentally, f ₀ represents the fundamental frequency of the resonator.

The high-frequency processing stubs T _{2 to} T _n and the compensation stubs T ₂ ^{* to} T _n ^* are stubs in the class F amplifier. The stub is a structure formed by grooves or the like formed in a parallel plate line so as to achieve consistency so as to cancel a reflected wave caused by a load.

  As the load resonance circuit 40, for example, a load resonance circuit used in a class F amplifier circuit described in Document 1 below is used.

  Reference 1: Ryo Ishikawa, Kenta Kuroda et al., 5.8 GHz band F class high efficiency amplifier for SSPS using GaN HEMT, IEICE, SPS2008-04, 2008

  The class F power amplifier means that the output value of the quarter wavelength transmission line 2 is short-circuited with respect to the high frequency, and the load of the amplifying element 1, that is, the input value of the quarter wavelength transmission line 2 is changed to the fundamental wave and the odd order. It is a circuit that achieves high-efficiency power amplification by opening the high frequency and shorting the even-order high frequency. As a result, harmonic processing can be performed so that the impedance is 0 (zero) for even harmonics and the impedance is ∞ (infinite) for odd harmonics, and the rectified waveform is shaped by harmonic synthesis to increase efficiency. Is possible.

  Next, referring to FIG. 1, an example of a procedure for setting constants and the like of each unit will be described. FIG. 2 is an equivalent circuit diagram of the class F amplifier circuit. In FIG. 2, a sine wave oscillation circuit 70 is an oscillation circuit in which the antenna 11 is replaced. The output of the sine wave oscillation circuit 70 is input to the gate of the switching element via the transmission path. The switching element has a source grounded and a drain connected to the input of the class F amplifier circuit. The drain of the switching element is connected to the power supply voltage Vdd through a choke coil. The gate of the switching element is connected to the bias voltage Vg through a choke coil.

The electrical length of each stub (T _{2 to} T _n ) of the load resonance circuit 40 is calculated using the following equation (1) as shown in FIG. Further, the electrical length of each stub (T ₂ ^{* to} T _n ^* ) of the class F amplifier circuit 40 is calculated using the following equation (2) as shown in FIG.

L _m = λ ₀ / 4m (m = 2, 3,..., N) (1)

L _m ^* = λ0 (2m−1) / 4m (m = 2, 3,..., N) (2)

In Expressions (1) and (2), λ is the wavelength of the signal input from the sine wave oscillation circuit (signal source) 70. Further, the transmission line _{T 12} to the transmission line _{T 11} is set to λ _0/4.

Next, an outline of the operation of the class F amplifier circuit will be described.
In FIG. 2, when the half-wave rectified current flowing through the switching element is expanded into a Fourier series, the frequency component I _d is expressed as the following equation (3).

I _d = I _max (1 / π + 1 / 2π · cosωt + 1 / 3π · cos2ωt-2 / 15π · cos4ωt + 2 / 35π · cos6ωt−) (3)

In Expression (3), ω is an angular frequency of the frequency input from the antenna 11. As shown in Expression (3), only the even-order high-frequency components exist in addition to the fundamental wave component. For this reason, if the voltage applied to the drain of the switching element is composed only of a fundamental wave having a phase opposite to that of the current and odd harmonics, power can be generated with a power factor of 100% with respect to the fundamental wave. And all the harmonics are in a state where power consumption is zero.
To achieve such a state, when the impedance viewed from the output of the switching element is an even-order harmonic, it is short-circuited (only current is present), open at odd-order harmonics (only voltage is present), and fundamental wave Current and voltage are completely opposite to each other and the power factor is minus one.
By setting the stub line length so that the relationship is as described above, harmonic processing is performed so that the impedance is 0 for even harmonics and ∞ (infinite) for odd harmonics. be able to.

Next, in the rectenna device 1 according to the present embodiment shown in FIG. 1, in the range 60 including the rectifying unit 30 and the load resonance circuit 140, the line lengths and the stub lengths are expressed by equations (1) and (2), and the transmission line. T ₁₁ = λ _0/4, calculates and sets a transmission path _{T 12} = _{λ 0/4.} Note that the calculated line lengths and stub lengths may be finely adjusted based on actual measurement values, for example.

Next, simulation results in the rectenna device 1 according to the present embodiment and the rectenna device 100 according to the related art will be described with reference to FIGS.
FIG. 3 is an equivalent circuit diagram for simulation of the rectenna device 1a in the present embodiment. The antenna 11 in FIG. 1 is replaced with a sine wave oscillation circuit 70.

  On the other hand, FIG. 4 is an equivalent circuit diagram for simulation of the rectenna apparatus 100 in the prior art. The same functional units as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 4, the rectenna device 100 includes a sine wave oscillation circuit 70, a circulator 12, a resistor 13, a transmission path 21, a capacitor 23, a rectifying unit 30, a capacitor unit 140, a λ / 4 line 151, a λ / 4 line 152, and a load 51. It has. The capacitor unit 140 includes a branch 141, a capacitor 143, and a transmission path 144. Reference numerals 22 and 142 represent parasitic capacitances of the capacitors 23 and 143 when package components are used for the capacitors 23 and 143, respectively.

The simulation condition is the input power that obtains the maximum conversion efficiency when the oscillation frequency is set to 2.45 [GHz] and the input power P is changed from 10 [mW] to 1000 [mW] in increments of 10 [mW]. A circuit simulation was performed. The simulation was performed by setting the input power P to 750 [mW].
In addition, the constants of all the components in the range 160 including the rectifying unit 30, the capacitor unit 140, the λ / 4 line 151, and the λ / 4 line 152 and the line length of the transmission line were optimized using a known method.

FIG. 5 is a diagram illustrating an input current / voltage waveform and an output current / voltage waveform in the rectenna apparatus 100 according to the related art. 5A is an input voltage waveform g1, FIG. 5B is an input current waveform g2, FIG. 5C is an output voltage waveform g3, and FIG. 5D is an output voltage waveform. This is a current waveform g4. The horizontal axis in FIGS. 5A to 5D is the time axis, the vertical axis in FIGS. 5A and 5C represents the voltage value, and FIGS. 5B and 5D. ) Represents the current value.
As shown by the solid line g3 in FIG. 5C and the solid line g4 in FIG. 5D, the output voltage and the output current are AC waveforms.

FIG. 6 is a diagram illustrating changes in the voltage / current waveform of the diode, the current waveform flowing through the λ / 4 line, the conversion efficiency, and the reflectance in the rectenna device 100 according to the conventional technology. 6A shows the voltage waveform g11 of the input to the diode 33, FIG. 6B shows the current waveform g12 of the input to the diode 33, and FIG. 6C shows the current flowing through the λ / 4 line. Waveform g13 and FIG. 6D are diagrams showing changes in conversion efficiency g14 and reflectance g15. 6A to 6C, the horizontal axis represents time, the vertical axis in FIG. 6A represents the voltage value, and the vertical axis in FIGS. 6B and 6C represents the current value. Represents. The horizontal axis of FIG.6 (d) represents the input electric power P, and the vertical axis | shaft represents the conversion efficiency and the reflectance.
As indicated by a solid line g14 in FIG. 6D, the conversion efficiency of the rectenna device 100 in the prior art is about 65%.

Next, the simulation result performed about this embodiment is demonstrated using FIG.3, FIG.7 and FIG.8. In the circuit diagram of FIG. 3, a sinusoidal input power is applied to the sine wave oscillation circuit 70, the oscillation frequency is set to 2.45 [GHz], and the input power P is from 10 [mW] to 1000 [mW]. A circuit simulation was performed with the input power to obtain the maximum conversion efficiency when changed in steps of 10 [mW]. The simulation was performed with the input power P set at 750 [mW].
In the load resonance circuit 40, the number of stubs is n = 7. The electrical length of each stub ^{_{(T 2 ~T n, T 2}} * ~T n *) of the load resonance circuit 40, were calculated using the equations (1) and (2). Further, the transmission line _{T 11} = _{λ 0/4,} and set to the transmission line _{T 12} = _{λ 0/4.}
Rectifier 30, in a range 60 including the load resonance circuit 40, the stub to the transmission line T ₁₁ and T ₁₂ except the line length of the transmission line were optimized using techniques known constant of each component.

FIG. 7 is a diagram showing an input current / voltage waveform and an output current / voltage waveform in the rectenna apparatus 1a of the present embodiment. 7A shows an input voltage waveform g21, FIG. 7B shows an input current waveform g22, FIG. 7C shows an output voltage waveform g23, and FIG. 7D shows an output voltage waveform g21. This is a current waveform g24. The horizontal axis in FIGS. 7A to 7D represents time, the vertical axis in FIGS. 7A and 7C represents the voltage value, and FIGS. 7B and 7D. The vertical axis of represents the current value.
As shown by the solid line g23 in FIG. 7C and the solid line g24 in FIG. 7D, the waveforms of the output voltage and output current are compared with the solid line g3 in FIG. 5C and the solid line g4 in FIG. The waveform is close to direct current.

FIG. 8 is a diagram showing changes in the voltage / current waveform of the diode, the current waveform flowing through the λ / 4 line, the conversion efficiency, and the reflectance in the rectenna device 1a according to the present embodiment. 8A shows a voltage waveform g31 of the input to the diode 33, FIG. 8B shows a current waveform g32 of the input to the diode 33, and FIG. 8C shows a current flowing through the λ / 4 line. Waveform g33 and FIG. 8D are diagrams showing changes in conversion efficiency g34 and reflectance g35. 8A to 8C is a time axis, the vertical axis of FIG. 8A represents a voltage value, and the vertical axes of FIGS. 8B and 8C are current values. Represents a value. In FIG. 8D, the horizontal axis represents input power P, and the vertical axis represents conversion efficiency and reflectance.
As shown by the solid line g34 in FIG. 8D, the conversion efficiency of the rectenna apparatus 1a in this embodiment is about 71%, which is higher than about 65% of the conversion efficiency of the rectenna apparatus 100 in the prior art.
Further, the voltage waveform g31 flowing through the diode 33 in FIG. 8A is clearly closer to a rectangular wave than the voltage waveform g11 flowing through the diode 33 in FIG. When each harmonic processing is performed as theoretically, the voltage waveform of the diode 33 becomes a rectangular wave.
In addition, since the voltages of the third harmonic, the fifth harmonic,... Are returned to the diode 33 by reflection, the voltage of the diode 33 is obtained when each harmonic processing is performed theoretically. The waveform is a rectangular wave.

  For this reason, the rectenna circuit in the present embodiment indicates that more complete harmonic processing is performed. It should be noted that although the output waveforms g23 and g24 are substantially DC waveforms, the conversion efficiency remains at about 71% because in FIG. 3, there is a slight reflection at each discontinuous point in the circuit diagram. It is also considered that this is due to the influence of the current flowing in the reverse direction through the diode.

As described above, in the rectenna device, the capacitor is used in the rectifier circuit in the prior art, but in the present embodiment, the load resonant circuit is used in the rectifier unit. As a result, harmonic processing can be performed such that the impedance is 0 (zero) for even harmonics and the impedance is ∞ (infinite) for odd harmonics, and the rectified waveform is shaped by harmonic synthesis. High efficiency can be achieved even at high frequencies such as millimeter waves.
Further, in this embodiment, since the capacitor used in the conventional single shunt rectifier circuit is not used, a capacitor having a large capacity becomes unnecessary, and the capacitor does not operate as a capacitor at a high frequency. The efficiency deterioration of the rectifier circuit can be prevented. As a result, high efficiency can be achieved even at high frequencies such as microwaves or millimeter waves.

[Second Embodiment]
FIG. 9 is an equivalent circuit diagram of the rectenna device 200 in the present embodiment. Functional units having the same functions as those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 9, the rectenna device 200 according to the present embodiment includes an antenna 11, a circulator 12, a resistor 13, a transmission path 21, a capacitor 23, a rectifying unit 30, a load resonance circuit 40, a capacitor unit 240, and a λ / 4 line 251. Yes. That is, the rectenna device 200 according to the present embodiment includes a capacitor unit 240 in the subsequent stage of the load resonance circuit 40 in addition to the first embodiment.
The capacitor unit 240 includes a branch 241, a capacitor 243, and a transmission path 244. Reference numeral 242 represents a parasitic capacitance of the capacitor 243 when a package component is used for the capacitor 243.
A load 51 is connected to the rectenna device 200.

In the rectenna apparatus 200 according to this embodiment, a method for setting constants, line lengths, and the like of each component will be described. The electrical length of each stub (T _{2 to} T _n , T ₂ ^{* to} T _n ^* ) of the load resonance circuit 40 is calculated using the formula (1) and the formula (2) as in the first embodiment, transmission line _{T 11} = _{λ 0/4,} set to the transmission line _{T 12} = _{λ 0/4.}
In the range 260 including the rectifying unit 30, the load resonance circuit 40, the capacitor unit 240, and the λ / 4 line 251, the line lengths of transmission lines other than the stub and the transmission line T ₁₁ and the transmission line T _{12 and} the constants of the respective components are The calculation is performed using a known method.

Next, simulation results in the rectenna device 200 according to the present embodiment and the rectenna device 200a according to the related art will be described with reference to FIGS.
FIG. 10 is an equivalent circuit diagram for simulation of the rectenna device according to the present embodiment. The antenna 11 in FIG. 1 is replaced with a sine wave oscillation circuit 70. The sine wave oscillation circuit 70 provides sinusoidal input power, sets the oscillation frequency to 2.45 [GHz], and changes the input power P from 10 [mW] to 1000 [mW] in increments of 10 [mW]. The circuit simulation was performed with the input power to obtain the maximum conversion efficiency. The simulation was performed with the input power P set to 750 [mW].
In the load resonance circuit 40, the number of stubs is n = 7. Also, the rectifying section 30, in the range 260 including the load resonant circuit 40, the stub and the transmission path T _11, the line length of the transmission line other than the transmission line T _12, the constant of each component is calculated by using a known technique.

FIG. 11 is a diagram showing an input current / voltage waveform and an output current / voltage waveform in the rectenna apparatus 200a of the present embodiment. 11A shows the input voltage waveform g41, FIG. 11B shows the input current waveform g42, FIG. 11C shows the output voltage waveform g43, and FIG. 11D shows the output. A current waveform g44. The horizontal axis of FIGS. 11A to 11D is a time axis, the vertical axis of FIGS. 11A and 11C represents a voltage value, and FIGS. 11B and 11D. ) Represents the current value.
As shown by the solid line g43 in FIG. 11C and the solid line g44 in FIG. 11D, the waveforms of the output voltage and output current are the simulation results of the first embodiment due to the effect of the capacitor unit 240. FIG. ) And the solid line g24 in FIG. 7D, the AC component is further reduced.

FIG. 12 is a diagram illustrating changes in the voltage / current waveform of the diode, the current waveform flowing through the λ / 4 line, the conversion efficiency, and the reflectance in the rectenna device 200a according to the present embodiment. 12A shows the voltage waveform g51 of the input to the diode 33, FIG. 12B shows the current waveform g52 of the input to the diode 33, and FIG. 12C shows the current flowing through the λ / 4 line. A waveform g53 and FIG. 12D are diagrams showing changes in the conversion efficiency g54 and the reflectance g55. The horizontal axis in FIGS. 12A to 12C is the time axis, the vertical axis in FIG. 12A represents the voltage value, and the vertical axes in FIGS. 12B and 12C are the currents. Represents a value. The horizontal axis of FIG.12 (d) represents the input electric power P, and the vertical axis | shaft represents the conversion efficiency and the reflectance.
As shown by the solid line g54 in FIG. 12D, the conversion efficiency of the rectenna device 200a in the present embodiment is equivalent to the first embodiment (about 71%), and is about 65% of the conversion efficiency of the rectenna device 100 in the prior art. taller than.
Further, the voltage waveform g51 flowing through the diode 33 in FIG. 12A is close to a rectangular wave, similar to the voltage waveform g31 flowing through the diode 33 in FIG. 8A, which is the simulation result of the first embodiment.

As described above, in the rectenna device, the capacitor unit is further provided in the subsequent stage of the load resonance circuit of the first embodiment, so that a more ideal rectification process can be performed than in the first embodiment. As a result, harmonic processing can be performed so that the impedance is 0 for even harmonics and ∞ for odd harmonics, and the rectified waveform is shaped by harmonic synthesis, even at high frequencies such as microwaves or millimeter waves. High efficiency can be achieved.
In this embodiment, only the capacitor 243 is additionally used in the subsequent stage of the load resonance circuit of the first embodiment, and the capacitor used in the conventional single shunt rectifier circuit is not used. . This eliminates the need for a capacitor having a large capacity, and further prevents deterioration of the efficiency of the rectifier circuit due to the fact that the capacitor does not operate as a capacitor at a high frequency. As a result, high efficiency can be achieved even at high frequencies such as microwaves or millimeter waves.

[Third Embodiment]
In the first and second embodiments, the load resonant circuit 40, which is a distributed constant line for each harmonic, is used as the resonant circuit, and the impedance is 0 for even harmonics and ∞ for odd harmonics. The example to do was explained. In the third embodiment, an example in which an LC resonance circuit is used as the resonance circuit will be described.

  FIG. 13 is an equivalent circuit diagram of a class F amplifier using an LC resonance circuit in the prior art. As shown in FIG. 13, the rectenna device 500 according to the prior art includes an antenna 11, a high frequency choke 501, a switching element 502 (FET), a capacitor 511, a λ / 4 line 521, and an LC resonance unit 530. A load 51 is connected to the rectenna device 500.

In the switching element 502, an input signal is input to the gate, the source is grounded, and the drain is connected to one end of the capacitor 511. Further, the drain of the switching element 502 is connected to the power supply voltage Vdd via the high frequency choke 501. One end of the capacitor 511 is connected to the antenna 11, the drain of the switching element 502 and one end of the high-frequency choke 501, and the other end is connected to one end of the λ / 4 line 521.
The λ / 4 line 521 has one end connected to the other end of the capacitor 511 and the other end connected to the LC resonance unit 530 and the load 51.

  The LC resonance unit 530 includes an inductor 531 and a capacitor 532. The inductor 531 and the capacitor 532 are connected in parallel, one end of the inductor 531 and the capacitor 532 is connected to the other end of the λ / 4 line 521 and the load 51, and the other end of the inductor 531 and the capacitor 532 is grounded. The LC resonating unit 530 resonates at the fundamental frequency.

  This LC resonance part 530 becomes a short circuit with respect to a high frequency. However, when viewed from the drain of the switching element 502 via the λ / 4 line 521, the LC resonance unit 530 becomes an open circuit due to the impedance conversion action of the λ / 4 line 521 with respect to odd harmonics. Further, the LC resonating unit 530 becomes a short circuit without the impedance conversion action of the λ / 4 line 521 acting on the even harmonics. For this reason, when a sufficient bias is applied to the switching element 502 and a high frequency signal is input, the voltage waveform of the drain becomes a rectangular wave by the fundamental wave and odd harmonic components, and the current waveform of the drain becomes the fundamental wave and even harmonics. A half-wave rectified waveform consisting of

  Therefore, even when the LC resonance unit 530 corresponding to each harmonic is used instead of the load resonance circuit 40 of FIG. 3, the diode 33 has an impedance of 0 for the even-order harmonics and an odd-order harmonic. Since harmonics can achieve ∞ impedance, it is possible to realize a rectenna device with higher conversion efficiency than the prior art. Alternatively, even when the LC resonance unit 530 corresponding to each harmonic is used instead of the load resonance circuit 40 of FIG. 9, the impedance is 0 for even harmonics and the impedance is for odd harmonics. Since ∞ can be realized, a rectenna device with higher conversion efficiency than the conventional technology can be realized.

  As described above, in the rectenna device, the LC resonance circuit corresponding to each harmonic of the received signal is used in the circuit portion using the capacitor in the conventional technique, so that the impedance is 0 for the even-order harmonics and 0 for the odd-order harmonics. Harmonic processing with an impedance of ∞ can be performed, the rectified waveform is shaped by harmonic synthesis, and high efficiency can be achieved even at high frequencies such as microwaves or millimeter waves.

  The rectenna apparatus of the present invention can be used alone or in combination. The rectenna device of the present invention is useful for wireless power transmission, but can also be used for energy harvesting called energy harvesting, and is extremely versatile.

DESCRIPTION OF SYMBOLS 1 ... Rectenna apparatus 11 ... Antenna 12 ... Circulator 13 ... Resistance 21, 34, 42, 44 ... Transmission path 22, 32 ... Parasitic capacitance 23 ... Capacitor 30 ... rectifier 31,41,43,45,46 ... branch 33 ... diodes 40 ... load resonance circuit _{T 11, T 12 ··· λ /} 4 line _T 2 _{through T} n ... high frequency processing stub T ₂ ^* ~T _n ^* ··· compensation stub 51 ... load 530 ... LC resonant portion

Claims (4)

A receiving means for receiving radio waves;
Rectifying means for rectifying radio waves received by the receiving means;
Resonance circuit in which the impedance of the harmonics of the radio waves rectified by the rectifier is zero for even harmonics and infinite for odd harmonics;
A rectenna device comprising: The resonant circuit is:
A first transmission line having a length of ¼ of the wavelength λ on the transmission line of the fundamental wave of the radio wave received by the receiving means;
A second transmission line having a length of ¼ of the wavelength λ on the transmission line of the fundamental wave of the radio wave received by the receiving means connected between the first transmission line and a load;
A plurality of first distributed constant lines connected in parallel to each other to an output terminal of the first transmission line;
A plurality of second distributed constant lines connected in parallel with each other to the input terminal of the second transmission line;
With
The first distributed constant line has a transmission line length L represented by L = λ / 4m (m is an integer from 2 to n), and m is different from each other.
The first distributed constant line has a transmission line length L represented by L = λ (2m−1) / 4m (m is an integer from 2 to n), and m is different from each other. Item 12. The rectenna device according to Item 1. The resonant circuit includes an LC resonant circuit in which a plurality of inductors and capacitors corresponding to each harmonic of received radio waves are connected in parallel.
The rectenna device according to claim 1, wherein one end of the LC resonance circuit is grounded and the other end is connected to a connection point between the rectifying unit and the load. One end is connected to the connection point in parallel with the resonance circuit and the resonance circuit, the load,
The rectenna device according to any one of claims 1 to 3, further comprising a capacitor whose other end is grounded.

Images