KR20200057593A - Wireless power transmit apparatus - Google Patents

Abstract

According to an embodiment of the present invention, provided is a wireless power transmission device which has high power transmission efficiency at low costs. The wireless power transmission device comprises: a reception antenna transmitting a beacon signal and receiving a power signal; a transmission array antenna in which a plurality of unit antennas transmitting the power signal are arranged; a plurality of phase shifters beam forming the power signal transmitted by each of the unit antennas; and a control unit calculating a phase of the power signal to be shifted by the phase shifter for each of the plurality of unit antennas. The phase shifter is one of bi-state to quad-state phase shifters.

Description

Wireless power transmission device {WIRELESS POWER TRANSMIT APPARATUS}

The present technology relates to a wireless power transmission device.

Various electronic devices, such as mobile phones and tablets, are mainly charged by a wired charging method, but in recent years, a wireless charging method has been introduced mainly on a mobile phone. In the wireless charging method, a magnetic induction type wireless charging using two coils located close to each other is also used.

Meanwhile, interest in technology for transmitting power within a medium distance using an RF signal is increasing. A power transmission system using microwaves emits RF signals from an antenna, and receiving electronics collects them through an antenna to receive power. In order to increase power transmission efficiency in a microwave power transmission apparatus, an array antenna including a plurality of unit antennas is used or an antenna having a high gain is used.

The method of using a plurality of unit antennas is to perform a beam forming (beam forming) to transmit power to the power signal toward the location of the receiving electronic device, and the method of using a high gain antenna mechanically fits the location of the receiver to the transmission antenna Adjust the direction of.

In the beam steering type power transmission system, the transmitter estimates the position of the receiver from the phase information of the beacon signal received from the receiver, and transmits a power signal that is an RF signal toward the receiver. Since the phase information of the beacon signal collected by each unit antenna varies according to the distance between the receiver and the transmitter, the position of the receiver can be estimated through the beacon signal.

In order to obtain high power transmission efficiency with a wireless power transmission apparatus, a retrodirective method is used as described above, and the reverse directivity method is used in a Fresnel region in which a beam is not properly formed using a general beam forming method. Effective when a receiver is present.

In order to transmit power, the beam must be steered in the direction of the estimated receiver through the beacon signal. For beam steering, a high precision phase shifter is required for each unit antenna included in the array antenna. However, the phase shifter having high precision has high driving power and the power lost is also large, so the power transmission efficiency of the power transmission system using the same is low. Furthermore, since the phase shifter with high precision is expensive, the price of the existing power transmission system including it is high.

This embodiment is intended to solve the above-mentioned disadvantages of the prior art. One of the problems to be solved by the present embodiment is to provide a wireless power transmission device having a high power transmission efficiency at a low price compared to the prior art.

The wireless power transmission apparatus according to the present embodiment transmits a beacon signal, a receiving antenna receiving a power signal, a transmitting array antenna arranged with a plurality of unit antennas transmitting power signals, and unit antennas, respectively. It includes a plurality of phase shifters (beam shifting) for beam forming the power signal to be transmitted and a control unit for calculating a phase of the power signal to be shifted by a phase shifter for each of the plurality of unit antennas. bi-state to quad-state phase shifter.

The wireless power transmission apparatus according to the present embodiment has an advantage of having an economical price while maintaining high power transmission efficiency.

1 is a block diagram showing an outline of a wireless power transmission apparatus 10 according to the present embodiment.
FIG. 2 schematically shows a phase shifter, a phase detector, and a control unit, and schematically shows a process of detecting a phase difference of a beacon signal for each unit antenna when a beacon signal is received.
3 is a schematic diagram for explaining that the control unit according to the present embodiment determines the phase of the power signal.
4 (a), 4 (b) and 4 (c) are diagrams illustrating a phase shifter that can be used in the wireless power transmission apparatus according to the present embodiment.
5 is a diagram illustrating an outline of a phase shifter, a phase detector, and a control unit when transmitting a power signal.
6 is a diagram illustrating the layout of a three-state phase shifter.
FIG. 7 shows a 64 state (6 bit) phase shift, 8 state (4 bit) phase shift, and 2 state (1) using a wireless power transmission device (conventional) and a reverse direction method when the reverse direction method is not used. bit) It is a diagram showing received power according to a distance of a wireless power transmission device using a phase shifter and a three-state phase shifter.

An overview of the wireless power transmission apparatus 10 according to this embodiment will be described with reference to the accompanying drawings. 1 is a block diagram showing an outline of a wireless power transmission apparatus 10 according to the present embodiment. Referring to FIG. 1, the wireless power transmission apparatus according to the present embodiment includes: a beam array (beam) a transmission array antenna 600 in which a plurality of unit antennas for transmitting a power signal are arranged, and a power signal transmitted by the unit antennas, respectively. It includes a plurality of phase shifter (forming) (phase shifter 400) and a controller 700 for calculating the phase of the power signal to the phase shifter for each of the plurality of unit antennas, the phase shifter 400 has two states ( bi-state to quad-state phase shifter. In one embodiment, the wireless power transmission apparatus 10 provides a beacon signal, and may further include a receiver RX for receiving the transmitted power signal.

2 shows an overview of the phase shifter 400, the phase detector 500 and the control unit 700, and outlines the process of detecting the phase difference of the beacon signal for each unit antenna when receiving a beacon signal. It is a drawing shown. 1 and 2, the receiver RX transmits a beacon signal to a receiving antenna. Each unit antenna receives a beacon signal and outputs it to the first power divider 710.

The first power divider 710 divides the beacon signal and provides it to the bidirectional couplers 730. The bidirectional coupler 730 outputs the divided beacon signal to the phase detector 740. A part of the beacon signal received by the unit antenna disposed at the end may be provided as a 50 Ω termination (750) by the bidirectional coupler 730.

In the illustrated embodiment, the phase detector 740 detects a phase difference between a beacon signal (blue dotted line) detected by one unit antenna and a beacon signal (red dotted line) detected by another unit antenna, and the detected phase difference information (Δφ ₁ , Δφ ₂ ) is provided to the control unit 700. In the illustrated embodiment, the beacon signals provided to one phase detector 740 may be beacon signals detected by unit antennas adjacent to each other.

3 is a schematic diagram for explaining that the control unit 700 according to the present embodiment determines the phase of the power signal. 1 to 3, the beacon signal transmitted by the reception antenna reaches a unit antenna included in the array antenna 600 through different paths r1, r2, r3, r4, and r5.

Since the beacon signal passes through different paths r1, r2, r3, r4, and r5, each path has a different length, so the beacon signals received by the unit antennas have different phases. The bar graph extended in the horizontal direction in FIG. 3 (a) schematically represents the phase of the beacon signal received by the unit antenna, and the phase of the signal reached via the short path r3 is small and the relatively long path r1, The phase of the signal reached via r5) was largely displayed. The controller 700 calculates the phase angle of the beacon signal received by each unit antenna from the phase difference information output by the phase detector 500.

FIG. 3 (b) is a diagram schematically showing a process in which the control unit determines a phase angle to be shifted by the phase shifter 400 transmitted by each unit antenna from the phase angle of the beacon signal received by each unit antenna. Referring to FIG. 3 (b), among the values obtained by multiplying the phase resolution of the phase shifter 400 by an integer multiple, the sum of the phase angles at which the unit antenna receives the beacon signal is the closest to the integer multiple of 360 °. The shifter 400 determines the phase value to be shifted.

When each unit antenna transmits a power signal that has not undergone a phase shift process, a phase difference occurs due to a length difference of a path, so transmission efficiency may be reduced due to interference between power signals in a location where the receiver RX is located. Accordingly, the control unit 700 changes the phase angle of the phase shifter 500 to shift the phase angle of the power signal to be transmitted for each unit antenna so that the power signals transmitted by the unit antennas may generate constructive interference at the position of the receiver RX. Decide.

The path through which the power signal reaches the receiving antenna RX from the unit antenna is the same path that differs only in the direction from the path where the beacon signal reaches the unit antenna. Accordingly, the power signal transmitted by each unit antenna is the same as the phase of the beacon signal received by the unit antenna when it reaches the receiver (RX) antenna.

)를 취하고, 이를 위상 해상도(

)로 나누어 반올림을 취한 몫과 가장 가까운 정수를 위상 해상도에 곱하여 위상 천이기의 위상각을 얻으며, 이는 아래의 수학식 1과 같이 연산할 수 있다. When the sum of the phase angles of the beacon signals received by the corresponding unit antenna is selected from among values multiplied by the resolution of the phase shifter as illustrated in FIG. 3 (b), the receiver RX selects a value closest to the integer multiple of 360 degrees. The power signal of does not decrease power efficiency due to constructive interference. In one embodiment, the control unit 700 is a pair of phase values that the unit antenna receives the beacon signal (-

), And the phase resolution (

Divide by) to obtain the phase angle of the phase shifter by multiplying the rounded quotient and the nearest integer to the phase resolution, which can be calculated as shown in Equation 1 below.

[]: Gaussian function, {}: rounded

The wireless power transmission apparatus according to the prior art uses a phase shifter having a high phase resolution, but the higher the resolution of the phase that the phase shifter can shift, the greater the power required to drive the phase shifter and the power loss in the driving process. It is large and the price is high. However, the phase shifter of this embodiment has a relatively low power loss and provides a cost advantage despite the use of a low-resolution phase shifter.

In one embodiment, the wireless power transmission apparatus according to the present embodiment has a phase resolution of 90 ° as illustrated in FIG. 4 (a), a reference phase, a reference phase + 90 °, a reference phase + 180 °, a reference phase A four-state phase shifter that can shift phase to + 270 ° can be used. In another embodiment, the wireless power transmission device has a phase resolution of 120 ° as illustrated in FIG. 4 (b), so that the phase can be shifted to a reference phase, a reference phase + 120 °, and a reference phase + 240 ° 3 State phase shifters can be used. In another embodiment, the wireless power transmission device has a phase resolution of 180 ° as illustrated in FIG. 4 (c), and uses a two-state phase shifter capable of shifting the phase to the reference phase and the reference phase + 180 °. Can be.

The switches used in FIGS. 4 (a) to 4 (c) may be semiconductor RF switches. For example, the semiconductor RF switch is a semiconductor-based switch capable of branching a signal path, and may be any one of a PIN diode or an RF switch using a transistor. The RF switch can change the signal path, and the signal path selected by the RF switch has a different length delay, so that the phase of the signal is changed. The semiconductor RF switch is shown as a single pole 4 throw (SP4T) switch as shown in Fig. 4 (a), or as a single pole 3 throw (SP3T) switch as shown in Fig. 4 (b) or as shown in Fig. 4 (c) It can be a single pole double throw (SPDT) switch.

5 is a diagram showing an outline of the phase shifter 400, the phase detector 500, and the control unit 700 when transmitting a power signal. 1 and 5, the oscillator 100 generates a power signal that is a radio frequency (RF) signal for power transmission, and the power amplifier 200 amplifies it as a large signal and provides it to the power distributor 300. . The power divider 300 distributes and provides power signals amplified by the power amplifier 200 for each antenna.

The control unit 700 controls the phase shifter 400 by determining the phase of the distributed signal as described above. The power signals phase-shifted by the phase shifter 400 are distributed by the second power divider 720, and the distributed power signals are provided to the bidirectional couplers 730, respectively. The first power divider 710 merges the power signals output from the bidirectional coupler 730 and provides them to the unit antenna. Each unit antenna is radiated in a phase shifted by each phase shifter 700.

In the prior art, a 3 dB hybrid coupler was used to separate the power signal, which caused the power to be split in half and lost transmission power. Since this embodiment uses a bidirectional coupler circuit, it is possible to reduce transmission power loss during transmission, and provides an advantage that a beacon signal between adjacent antennas can be input to a phase detection circuit without the need for a switching circuit.

Experimental Example

Hereinafter, an experimental example of the wireless power transmission apparatus according to the present embodiment will be described. The phase shifter used a three-state phase shifter illustrated in FIG. 6 (see FIG. 4 (b)). Table 1 below is a table showing the experimental results.

Type of phase shifter Phase resolution (deg.) Phase shifter loss (dB) Algorithm error (dB)
* Tx = 32x32, Rx = 1x1 ideal 0.1 0 0 4-bit 22.5 6 ~ 9 -0.06 3 states 120 2.8 ~ 3.2 -2.3

As illustrated in Table 1, when a 64-state phase shifter is used, the phase shifter has a good resolution characteristic of 22.5 degrees. However, the phase shifter losses range from 6 to 9 dB, and the sum of losses due to algorithm errors amounts to approximately 6.06 to 9.06 dB. On the other hand, the phase resolution of a low-cost three-state phase shifter is only 120% and 20% of the phase resolution of a 64-state phase shifter, but the loss occurring in the phase shifter is only 2.8 to 3.2 dB, and an algorithm error It can be seen that the sum of the losses due to is only about 5.1 to 5.6 dB.

FIG. 7 shows a 64 state (6 bit) phase shift, 8 state (4 bit) phase shift, and 2 state (1) using a wireless power transmission device (conventional) and a reverse direction method when the reverse direction method is not used. bit) It is a diagram showing received power according to a distance of a wireless power transmission device using a phase shifter and a three-state phase shifter. Referring to FIG. 7, it can be seen that the wireless power transmission apparatus that does not use the reverse-direction method receives the lowest power regardless of the distance between the transmitter and the receiver.

The 64 state (6 bit) phase shifter and the 8 state (4 bit) phase shifter using the reverse-direction method are displayed by overlapping the received power values, and have the highest received power performance among comparison targets.

In contrast, a wireless power transmission device using a three-state phase shifter receives about 2.5 dBm lower than a wireless power transmission device using a 64-state (6 bit) phase shifter and an 8-state (4 bit) phase shifter within a distance of 1 m. It can be seen that there is only a difference in power characteristics. Therefore, according to the present embodiment, the three-state phase shifter is provided with the advantage of good price / performance compared to the 64-state (6 bit) phase shifter and the 8-state (4 bit) phase shifter.

In order to help the understanding of the present invention, it has been described with reference to the embodiment shown in the drawings, but this is an embodiment for the implementation, it is only an example, and those skilled in the art, various modifications and equivalents therefrom It will be understood that other embodiments are possible. Therefore, the true technical protection scope of the present invention should be defined by the appended claims.

100: oscillator 200: power amplifier
300: power divider 400: phase shift
500: phase detector 600: transmit antenna
700: control unit 750: 50 ohm termination
710: first power divider 720: second power divider
730: bidirectional coupler 740: phase comparator

Claims (10)

The wireless power transmission device is:
A transmission array antenna in which a plurality of unit antennas transmitting power signals are arranged;
A plurality of phase shifters for beam forming the power signals transmitted by the unit antennas, respectively; And
For each of the plurality of unit antennas includes a control unit for calculating the phase of the power signal to the phase shifter,
The phase shifter is a bi-state (qua-state) to a four-state (quad-state) phase shifter any one of the wireless power transmission device. According to claim 1,
The phase shifter,
A wireless power transmission device that is a bi-state phase shifter that outputs a phase of an input signal by shifting a reference phase or a reference phase + 180 °. According to claim 1,
The phase shifter,
A wireless power transmission device that is a tri-state phase shifter that delays and outputs the phase of an input signal to one of a reference phase, a reference phase + 120 °, and a reference phase + 240 °. According to claim 1,
The phase shifter,
Four-phase phase shifter (quad-state phase shifter) wireless power transmission device that outputs by shifting the phase of the input signal to any one of a reference phase, a reference phase + 90 °, a reference phase + 180 ° and a reference phase + 270 °. According to claim 1,
The control unit,
Among the values obtained by multiplying the resolution of the phase shifter, the unit antenna determines the value closest to the integer multiple of 360 °, which is the sum of the phase values received by the unit antenna, as the phase value of the power signal to which the phase shifter shifts. Wireless power transmission device. According to claim 1,
The control unit,
A wireless power transmission apparatus for determining, by a phase angle of a phase shifter, a value obtained by multiplying a phase resolution by an integer value close to a quotient obtained by dividing a pair of phase values received by the unit antenna by the phase resolution. According to claim 1,
The wireless power transmission device,
A phase detection circuit unit including a plurality of unit phase detection circuits, the unit phase detection circuit comprising:
A first power divider for dividing the power of the beacon signal received by the unit antenna,
A phase comparator that receives the unit antennas and detects a phase difference between beacon signals that are divided and provides the control unit to the controller.
And a bi-directional coupler that provides a beacon signal divided by the first power divider to the phase comparator. The method of claim 7,
The unit phase detection circuit,
Further comprising a second power divider for dividing the power signal provided by the phase shifter,
The bidirectional coupler provides a power signal divided by the second power divider to the first power divider,
The first power divider is a wireless power transmission device that merges the provided power signals and provides them to the unit antenna. According to claim 1,
The wireless power transmission device,
An oscillator generating a power signal at a predetermined frequency,
And a power amplifier for amplifying the power of the signal generated by the oscillator. According to claim 1,
The wireless power transmission device,
A beacon (beacon) signal, the wireless power transmission device further comprises a receiving antenna for receiving the power signal.

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