rectifier circuit

Abstract

The objective is to provide a highly efficient rectifier circuit by improving the symmetry of the layout of the rectifier circuit, which includes diodes and the wiring and transmission lines containing them. Furthermore, the aim is to provide a rectifier circuit suitable for use with rectennas. [Solution] The diode pair is formed by connecting a first diode connected to a first input terminal and a second diode connected to a second input terminal in opposite polarities in series via node B, a transmission line connected in parallel to both ends of the diode pair, and an output connection line connecting node B and an output terminal, wherein the diode pair and the transmission line are arranged symmetrically with respect to a straight line passing through the midpoint of node B and the transmission line.

Description

Technical Field

[0001] The present invention relates to a high-frequency rectifier circuit, and particularly to a rectifier circuit suitable for a rectenna.

Background Art

[0002] As a power receiving device in a power transmission system using microwaves, for example, a rectenna is known. For example, FIG. 14 shows an example of power transmission to a moving body such as a drone. When efficiently transmitting power to a wireless device such as a drone, it is important to improve the efficiency of the rectifier circuit and the DC / DC conversion circuit. In such wireless power transmission, since the loss of space propagation is large, the larger the frequency is, the relatively larger the antenna aperture area with respect to the wavelength becomes, and high gain is expected. For such reasons, in recent years, the high-frequency region of 20 GHz or more has been attracting attention, but it is known that the higher the frequency, the more remarkable the decrease in the efficiency of the rectifier circuit.

[0003] As described in Non-Patent Document 1, various circuits are known for the rectifier circuit. For example, when assuming a constant voltage load such as a lithium-ion battery as the output load of the power receiving device, it is necessary to convert the received voltage to a low voltage. Since the efficiency of the DC / DC conversion circuit decreases as the conversion ratio increases, the inventors studied based on the double-current rectifier circuit known as a rectifier circuit with a low output voltage. However, the conventional double-current rectifier circuit had the following technical problems. FIG. 15(a) shows a matching circuit and a double-current rectifier circuit diagram, and FIG. 15(b) shows a wiring diagram of the rectifier circuit. At high frequencies, the influence of the parasitic inductance shown in FIG. 15(b) cannot be ignored. Due to the difference between V d1 and V d2 high-frequency components leak out to the output terminals, resulting in a decrease in rectification efficiency. Furthermore, while toroidal coils have traditionally been used for matching and RF choke inductors, these toroidal coils are not suitable for high frequencies above 1 GHz. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Kyohei Yamada, [Invited Lecture] 6.78MHz Current Doubler Rectifier Circuit Using a High-Q Inductor, IEICE Technical Report, EE2017-10, WPT2017-15 (2017-07) [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a highly efficient rectifier circuit by improving the symmetry of the layout of a rectifier circuit that includes a diode and wiring and transmission lines containing the diode. Furthermore, the aim is to provide a rectifier circuit suitable for use with rectennas. [Means for solving the problem]

[0006] The rectifier circuit according to the present invention comprises a diode pair in which a first diode connected to a first input terminal and a second diode connected to a second input terminal are connected in series with opposite polarities via node B, a transmission line connected in parallel to both ends of the diode pair, and an output connection line connecting node B and an output terminal, wherein the diode pair and the transmission line are arranged symmetrically with respect to a straight line passing through the midpoint of node B and the transmission line. Here, a high-frequency signal (RF signal) is either input to one of the pair of diodes and the other is connected to ground (GND), or a differential high-frequency signal is input to the input terminals of the pair of diodes, the first and second diodes.

[0007] The present invention is characterized by arranging the diode pair symmetrically such that node B of the series-connected first diode and second diode are the midpoint, so that the rectifier circuit layout has opposite polarities to each other. This suppresses even-order harmonics generated by the first and second diodes, reducing losses due to harmonic signals. Although a diode pair has parallel parasitic capacitance, by connecting an inductive transmission line in parallel and causing parallel resonance, the reflection loss of high-frequency signals input from the input terminal pair can be reduced.

[0008] Here, it is preferable that node B and the midpoint of the transmission line lie on the axis of symmetry, and since node B contains both DC signals and harmonic signals, it is preferable to extract only the DC signal from the output terminal, and as a means to do so, the output connection line may be an RF choke circuit, or it may be a spiral inductor. Alternatively, instead of the RF choke circuit described above, a λ / 4 transmission line that is 1 / 4 wavelength at the input frequency may be used to extract the DC signal.

[0009] Such a rectifier circuit can be used for a rectenna, with one input terminal connected to the antenna and the other to ground, or with the first and second input terminals connected to the antenna and a differential high-frequency signal input to the first and second input terminals. This suppresses even-order harmonics generated in the diode pair. In this case, the shape of the transmission line can be not only a straight line or an arc, but also a spiral-shaped spiral inductor. Here, for example, as shown in Figure 9, it is important to arrange the nodes symmetrically with respect to a hypothetical straight line passing through node B and the midpoint of the transmission line. Furthermore, when differential high-frequency signals are input to both terminals of a diode pair, a GND via may be provided at the midpoint of the transmission line, or this midpoint may be connected to the GND via. By doing so, a closed circuit of a DC signal including a DC load connected to the output terminal and a GND via is realized, and the design freedom of the antenna is increased. Also, in the present invention, a transmission line that magnetically couples with the transmission line and inputs a high-frequency signal to the first input terminal or the second input terminal not connected to the ground may be provided, or a transmission line that magnetically couples with the transmission line and inputs a differential high-frequency signal to the first input terminal and the second input terminal may be provided. By doing so, it is not necessary to directly and mechanically connect the antenna connected to the input terminal and the diode pair, and the mounting of the antenna to the rectifier circuit is simplified.

Effect of the Invention

[0010] In the rectifier circuit according to the present invention, since the node B of the diode pair is laid out so as to be an ideal midpoint with respect to the RF input from the antenna, even-order harmonics generated in the first diode and the second diode are suppressed. Also, the transmission line can be made to act as an inductor for matching with respect to the high-frequency signal.

Brief Description of the Drawings

[0011] [Figure 1] An example of the rectifier circuit according to the present invention is shown. [Figure 2] A comparison of rectification efficiency is shown. [Figure 3] An example in which the first input terminal is connected to the antenna and the second input terminal is connected to GND is shown. [Figure 4] An example in which a spiral inductor is used instead of the RF choke circuit is shown. [Figure 5] An example in which a λ / 4 transmission line and a MIM capacitor are combined instead of the RF choke circuit is shown. [Figure 6] An example in which a λ / 4 transmission line and a λ / 4 open stub are combined instead of the RF choke circuit is shown. [Figure 7] An example in which a λ / 8 open stub is connected in parallel to the DC load with respect to FIG. 6 is shown. [Figure 8]An example of inputting a differential high-frequency signal to a pair of input terminals is shown. [Figure 9] An example of using a spiral inductor instead of a transmission line is shown. [Figure 10] An example of loading a GND via at the midpoint of a transmission line is shown. [Figure 11] An example of connecting the midpoint of a transmission line and a GND via is shown. [Figure 12] An example of arranging a resistor between a transmission line and a GND via is shown. [Figure 13] An example of inputting a high-frequency signal by electromagnetic coupling is shown. [Figure 14] ] An example of a microwave power transmission system is shown. [Figure 15] (a) shows a conventional matching circuit and a double-current rectifying circuit, and (b) shows an explanatory diagram of the influence of wiring.

Embodiments for Carrying Out the Invention

[0012] A configuration example of a rectifying circuit for a rectenna according to the present invention will be described based on the following figures, but the present invention is not limited thereto.

[0013] Fig. 1 shows a basic configuration example of the rectifying circuit according to the present invention. The first diode 11 and the second diode 21 are connected in series at node B with opposite polarities. The first input terminal 12 is arranged at the end of the first diode 11, and the second input terminal 22 is arranged at the end of the second diode 21 in line symmetry with respect to node B, and has a transmission line 31 connected in parallel to both ends of the diode pair. Node B is connected to the output terminal 32 via an RF choke circuit 33. Thereby, a direct current can be taken out from node B. The rectifying circuit according to the present invention is characterized in that the diode pair (11, 21) and the transmission line are arranged in line symmetry with respect to a virtual straight line passing through node B and the midpoint of the transmission line 31. The operation method involves connecting an antenna to one of the first input terminal 12 and the second input terminal 22, and connecting the other to GND, or connecting an antenna to both the first input terminal 12 and the second input terminal 22 and inputting a differential high-frequency signal. Here, even-order harmonics generated by the first diode 11 and the second diode 21 are suppressed, and the transmission line has an impedance matching function for high-frequency signals.

[0014] Figure 2 shows the change in rectification efficiency with respect to input power (W) when a frequency of 10 GHz is input to the first and second input terminals (12, 22). Figure 15 shows that the wiring according to the present invention has improved rectification efficiency compared to the conventional wiring. Even an improvement of just a few percent can have a significant effect in reducing power loss in the case of high-input power rectennas.

[0015] Next, we will describe an example of mounting the circuit board. Figure 3 shows a pair of diodes (11, 21) arranged symmetrically with respect to a hypothetical straight line passing through node B and the midpoint of transmission line 31, and the second input terminal 22 connected to the GND layer via GND via 23 with respect to transmission line 31. In this case, the first input terminal 12 will be connected to the antenna. Figure 4 shows an example in which a spiral inductor 32 is used instead of the RF choke circuit 33. In this case, by using a spiral inductor with a sufficiently large reactance value for the DC load connected to the output terminal, signals above the fundamental frequency are open-ended, and a DC signal is output. When considering mounting on a circuit board, spiral inductors are easier to implement.

[0016] Figure 5 shows an example in which, instead of the RF choke circuit 33, a λ / 4 transmission line 40 is used in which one end is short-circuited at a high frequency by a MIM capacitor (Metal-Insulator-Metal capacitor) 41 connected to GND vias 42a and 42b. Here, the reactance value of the MIM capacitor is assumed to be sufficiently smaller than the DC load connected to the output terminal. As shown in Figure 5, the layout symmetry is improved by arranging the MIM capacitors connected to the GND vias in an upper and lower position. Here, since the λ / 4 transmission line 40 can be considered a λ / 4 short-circuit stub for high-frequency signals, the fundamental wave and odd-order harmonics are terminated with an open circuit, and the even-order harmonics are terminated with a short circuit, resulting in the output of a DC signal. Figure 6 shows an example where the MIM capacitor and GND via are replaced with a λ / 4 open stub 43. This approach allows us to ignore the parasitic inductance of the GND via, enabling a highly accurate design.

[0017] Figure 7 shows an example in which a λ / 8 transmission line 44a is added between the output terminal 32 and the embodiment shown in Figure 6, and a λ / 8 open stub 44b is connected in parallel to the DC load. This suppresses even-order harmonics from passing through the DC load.

[0018] Figure 8 shows an example of implementation as a rectenna, where the first input terminal 12 and the second input terminal 22 are connected to an antenna and a differential high-frequency signal is input. In this case as well, line symmetry is ensured with respect to a hypothetical straight line passing through node B and the midpoint of the transmission line. As shown in Figure 10, when implementing for a rectenna, a GND via 36c may be mounted at the midpoint of transmission lines 36a and 36b, or, as shown in Figure 11, the midpoint of transmission line 36 may be connected to the GND via 36c. This configuration creates a closed circuit for the DC signal, including the DC load connected to the output terminal and the GND via, eliminating the need to create a closed circuit for the DC signal on the antenna side. Furthermore, as shown in Figure 12, placing a resistor 36d between the transmission line and the GND via 36c can suppress imbalances in differential high-frequency signals.

[0019] Figure 13 shows an example in which a λ / 4 transmission line 38 is arranged to be electromagnetically coupled to the transmission line 37. The λ / 4 transmission line 38 is not connected to ground, and the midpoint of the transmission line 37 is connected to the GND via 37a. Input terminals (12, 22) are provided at both ends of the λ / 4 transmission line 38. The circuit operates by inputting a high-frequency signal to one terminal and connecting the other to ground, or by inputting differential high-frequency signals to both input terminals. This eliminates the need to connect the antenna linearly to the diode pair. [Explanation of symbols]

[0020] 11. First diode 12. First Input Terminal 21 Second Diode 22 Second Input Terminal 23 GND via 31 Transmission lines 32 output terminals 33 RF Choke Circuit 34 Spiral Inductor

Claims

1. A diode pair is formed by connecting a first diode connected to the first input terminal and a second diode connected to the second input terminal in series with opposite polarities via node B. A transmission line connected in parallel to both ends of the diode pair, It has an output connection line connecting the node B and the output terminal, A rectifier circuit characterized in that the diode pair and the transmission line are arranged symmetrically with respect to a straight line passing through node B and the midpoint of the transmission line.

2. The rectifier circuit according to claim 1, characterized in that the output connection line is an RF choke circuit.

3. The rectifier circuit according to claim 1, characterized in that the output connection line is a spiral inductor.

4. The rectifier circuit according to claim 1, characterized in that the output connection line has a λ / 4 transmission line which is 1 / 4 wavelength at the input frequency.

5. The rectifier according to any one of claims 1 to 4, characterized in that a high-frequency signal is input from one of the first input terminal and the second input terminal, and the other is connected to ground.

6. The rectifier circuit according to any one of claims 1 to 4, characterized in that differential high-frequency signals are input to the first input terminal and the second input terminal.

7. The rectifier circuit according to claim 5, characterized in that it has a transmission line that is electromagnetically coupled to the transmission line and inputs a high-frequency signal to the first input terminal or the second input terminal which is not connected to ground.

8. The rectifier circuit according to claim 6, characterized in that it has a transmission line that is electromagnetically coupled to the transmission line and inputs differential high-frequency signals to the first input terminal and the second input terminal.

9. The rectifier circuit according to claim 6 or 8, characterized in that the midpoint of the transmission line is connected to ground.

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