KR102593833B1 - Waveform Design for Multi-user Wideband Wireless Power Transfer with Non-linear Energy Harvester - Google Patents

Abstract

A broadband multi-user wireless power transmission method and device considering a nonlinear energy harvester are presented. The wireless power transmission method in a multi-path channel proposed by the present invention includes the steps of arranging channels of a plurality of receivers for receiving TR (Time Reversal) waveforms transmitted from a transmitter in reverse chronological order; arranging channels in reverse chronological order; A step of generating a TR (Time Reversal) waveform using the channels of a plurality of receivers, and aligning the phase difference between the components of the TR waveform to be received at each receiver receiving the TR waveform from the transmitter to be in phase at the transmitter to create a PATR It includes the step of generating a (Phase Aligned Time Reversal) waveform. In another aspect, the method for transmitting wireless power in a multi-path channel proposed by the present invention converts the phase difference between the components of the wireless power signal to be received at each of the plurality of receivers receiving the wireless power signal from the transmitter into in-phase. Setting a phase shift value for alignment and generating a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in phase using the set phase shift value in the transmitter. Includes.

Description

Wideband multi-user wireless power transmission waveform design considering non-linear energy harvester {Waveform Design for Multi-user Wideband Wireless Power Transfer with Non-linear Energy Harvester}

The present invention relates to a broadband multi-user wireless power transmission method and device considering a nonlinear energy harvester.

WPT (Wireless Power Transfer) is a technology that wirelessly supplies power to various small wireless communication devices that make up the IoT (Internet of Things) network.

Unlike magnetic resonance-type power transmission techniques, WPT using RF (Radio Frequency) signals can extend the power transmission distance to several meters, and the received RF signals are converted to DC (Direct current) by an energy harvester used as an energy receiver. ) is rectified and supplies power to the battery.

However, RF signals propagate through broadband channels, and it is difficult for the receiver to receive a signal with sufficient power due to the effects of path loss and inter-symbol interference due to multi-path channels.

Due to this problem, WPT using RF signals requires a different type of waveform design than that of existing wireless power transmission in order to increase the power of the received signal at the receiver.

In the WPT-related technology according to the prior art, the waveform was designed considering only the operation of the linear region of the energy harvester. This is a method that assumes that the relationship between the power of the RF received signal and the output power of the energy harvester converted to DC is linearly proportional.

However, an energy harvester considering an actual diode-based rectifier shows nonlinear RF-to-DC conversion characteristics in which DC output power increases exponentially for RF received signals above a certain power due to the nonlinear operation characteristics of the diode.

In the nonlinear operating region of a real energy harvester, the DC output power increases exponentially with respect to the power of the RF received signal, so a waveform with a larger peak amplitude is more energy transfer efficient than a WPT waveform with a larger average received power. Because it is high, most of the harvested power obtained through the energy harvester is obtained from the peak component of the received signal.

The peak amplitude signal refers to the signal in the signal section with the largest amplitude among signals received during one cycle of the received signal.

Figure 1 is a graph showing the relationship between input signals and output signals in the operating area of an energy harvester according to the prior art.

Referring to the relationship between the input signal 110 and the output signal 120 in the operating area of the energy harvester shown in Figure 1, the average received power of the RF received signal has one larger peak than the larger waveform (ST 132). It shows that the DC output voltage of the waveform (PATR (131)) in which the amplitude signal exists is larger.

The prior art [1] designs the power transmission waveform considering a WPT system with a single transmission antenna and a single user. In the prior art [1], considering linear EH (Energy Harvesting), a single-tone waveform was proposed that focuses power on the most dominant frequency in the frequency response of the channel. However, the single-tone waveform in nonlinear EH has poor energy transfer efficiency.

Prior art [2] proposed a model that expressed the nonlinear characteristics of EH through Taylor expansion. Additionally, the optimal power transmission waveform in the WPT system using the model was proposed. The proposed waveform can be obtained through software that solves the convex problem, and has the disadvantage of being very computationally complex and designed in the frequency domain, making it difficult to implement as an actual WPT system.

The prior art [3] proposed a more sophisticated nonlinear EH model than the prior art [2]. The optimal power transmission waveform in a WPT system with a single transmit antenna and a single user was proposed. However, like the prior art [2], the computational complexity of the waveform design is very complex and it has the disadvantage of being designed in the frequency domain.

[P1] Korean Patent No. 10-2179030 (2020.11.10) [P2] Korean Patent No. 10-2153809 (2020.09.02)

[1] M. Ku, Y. Han, H. Lai, Y. Chen, and K. J. R. Liu, “Power waveforming: Wireless power transfer beyond time reversal,” IEEE Trans. Signal Process., vol. 64, no. 22, pp. 5819-5834, Nov. 2016. [2] B. Clerckx and E. Bayguzina, “Waveform design for wireless power transfer,” IEEE Trans. Signal Process., vol. 64, no. 23, pp. 6313-6328, Dec. 2016. [3] M. R. Vedady Moghadam, Y. Zeng, and R. Zhang, "Waveform optimization for radio-frequency wireless power transfer: (invited paper)," in IEEE SPAWC, SPK, Japan, 2017, pp. 1-6.

The technical problem to be achieved by the present invention is to provide a multi-path channel and transmission for a specific user in a broadband wireless power transmission system through a TR (Time Reversal) filter, which is designed by inverting the channel impulse response (CIR) with respect to time in the transmitter and converting it to a complex conjugate. The aim is to provide a TR waveform generation method and system for maximizing SINR (Signal to Interference plus Noise Ratio) using matched filtering with the signal. In addition, in order to improve wireless power transmission efficiency in a multi-path channel environment compared to the conventional WPT waveform technique, based on the proposed TR waveform, each user's desired signal and IUI (Inter User Interface) caused by other users are generated. The purpose of this study is to provide a method and system for generating PATR (Phase Aligned Time Reversal) waveforms that align the phases of interference.

In one aspect, the method of wireless power transmission in a multi-path channel proposed by the present invention includes arranging channels of a plurality of receivers for receiving a TR (Time Reversal) waveform transmitted from a transmitter in reverse order with respect to time, generating a TR (Time Reversal) waveform using channels of a plurality of receivers arranged in reverse order, and synchronizing the phase difference between the components of the TR waveform to be received at each receiver receiving the TR waveform from the transmitter. It includes the step of aligning in phase to generate a PATR (Phase Aligned Time Reversal) waveform.

The step of generating a PATR waveform by aligning the phase difference between the components of the TR waveform to be received at each receiver receiving the TR waveform from the transmitter to be in phase at the transmitter includes the channel of the first receiver among the plurality of receivers and the first receiver. The phase difference between the coherent element consisting of matched filtering with the TR waveform received from the channel and the non-coherent element resulting from non-coherent filtering with the TR waveform received from the channel of the first receiver and the second receiver is in phase. Sort.

The step of generating a TR waveform using channels of a plurality of receivers arranged in reverse order with respect to time includes a plurality of channels to reduce the effect of power reduction of the TR waveform received at the receiver due to the random phase of the information symbol in wireless power transmission. Using the non-linear characteristics of the receiver's energy harvester, a TR waveform is generated as a deterministic periodic signal, which is a peak amplitude signal of a predetermined size or more.

The step of generating a TR waveform using the channels of a plurality of receivers arranged in reverse order of time includes complex conjugating the channels of a plurality of receivers arranged in reverse order of time, and then complex conjugating the channels of the plurality of receivers arranged in reverse order of time. The TR waveform is generated by adding up all of the receiver's channels.

The step of arranging the channels of the plurality of receivers for receiving the TR waveform transmitted from the transmitter in reverse chronological order includes placing the channels of the plurality of receivers in reverse chronological order to reduce complexity in the process of generating the TR waveform. By arranging them, a TR waveform in the time domain is generated.

In another aspect, the method for transmitting wireless power in a multi-path channel proposed by the present invention converts the phase difference between the components of the wireless power signal to be received at each of the plurality of receivers receiving the wireless power signal from the transmitter into in-phase. Setting a phase shift value for alignment and generating a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in phase using the set phase shift value in the transmitter. Includes.

The step of setting a phase shift value to align the phase difference between the components of the wireless power signal to be received in each of the plurality of receivers receiving the wireless power signal from the transmitter to the same phase is the peak amplitude signal of the received wireless power signal. A coherent element consisting of matched filtering between the TR waveform received from the first receiver and the channel of the first receiver among the plurality of receivers to maximize the sum of the magnitude, and the channel of the first receiver and the TR waveform received from the second receiver. Set the phase shift value so that the phase between non-coherent elements due to non-coherent filtering with the TR waveform matches.

In order to maximize the sum of the magnitudes of the peak amplitude signals of the received wireless power signals according to an embodiment of the present invention, the peak amplitude signals in each of the plurality of receivers are expressed as a determinant, and each of the plurality of receivers is based on the determinant. The phase component of the main eigenvector is obtained through eigenvalue decomposition, and the optimal phase shift value is set using the phase component of the main eigenvector.

The step of generating a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in-phase using the set phase shift value in the transmitter is a step of generating an Energy (EH) waveform in each of the plurality of receivers. Harvesting) In order to increase the power, the phase shift value set above is used to adjust the phase difference between the IUI (Inter User Interference) and the desired signal generated from each of the plurality of receivers in a wireless power transmission environment in a multi-path channel. Sort by

The wireless power signal to be received by each of the plurality of receivers according to an embodiment of the present invention is a complex conjugate of the channels of the plurality of receivers arranged in reverse chronological order, and the channels of the plurality of receivers arranged in reverse chronological order. Then, it may be a TR (Time Reversal) waveform generated by addition.

According to an embodiment of the present invention, the channels of the plurality of receivers are arranged in reverse order of time to generate a TR waveform in the time domain, so that the transmitter as the number of the plurality of transmitting antennas and the plurality of receivers of the transmitter increases. A PATR waveform can be generated by flexibly expanding in the time domain using CIR (Channel Impulse Response) between a plurality of transmitting antennas and the plurality of receivers.

In another aspect, in the multi-user wireless power transmission system including a transmitter with a plurality of transmission antennas and a plurality of receivers proposed by the present invention, the transmitter receives a TR (Time Reversal) waveform transmitted from the transmitter. The channels of the plurality of receivers are arranged in reverse order of time, the channels of the plurality of receivers arranged in reverse order of time are complex conjugated, and then added to generate a TR (Time Reversal) waveform.

The transmitter uses the non-linear characteristics of the energy harvesters of a plurality of receivers to reduce the effect of power reduction of the TR waveform received at the receiver due to the random phase of the information symbol in wireless power transmission, and determines the peak amplitude signal of a predetermined size or more ( TR waveform is generated as a periodic signal in deterministic form.

The transmitter generates a TR waveform in the time domain by arranging the channels of the plurality of receivers in reverse chronological order to reduce complexity in the process of generating the TR waveform.

In another aspect, in the multi-user wireless power transmission system including a transmitter and a plurality of receivers with a plurality of transmission antennas proposed in the present invention, the plurality of receivers each include an energy harvester, and the transmitter receives the PATR sets a phase shift value to align the phase difference between the components of the wireless power signal to be in-phase, and maximizes the sum of the peak amplitude signals of the wireless power signal aligned to the same phase using the set phase shift value. (Phase Aligned Time Reversal) Creates a waveform.

The transmitter is a coherent element consisting of matched filtering between a channel of a first receiver among the plurality of receivers and a TR waveform received from the first receiver to maximize the sum of the magnitude of the peak amplitude signal of the received wireless power signal, and The phase shift value may be set so that the phase between the channel of the first receiver and the non-coherent element resulting from non-coherent filtering with the TR waveform received from the second receiver matches the phase.

The transmitter represents the peak amplitude signal at each of the plurality of receivers as a determinant to maximize the sum of the magnitudes of the peak amplitude signals of the received wireless power signal, and calculates an eigenvalue for each of the plurality of receivers based on the determinant. The phase component of the main eigenvector is obtained through decomposition, and the optimal phase shift value is set using the phase component of the main eigenvector.

The transmitter uses the set phase shift value to increase the EH (Energy Harvesting) power of each of the plurality of receivers to prevent Inter User Interference (IUI) generated from each of the plurality of receivers in a wireless power transmission environment in a multi-path channel. and aligning the phase difference between the desired signals to be in phase.

The transmitter transmits a wireless power signal to the plurality of receivers, and the wireless power signal arranges the channels of the plurality of receivers in reverse chronological order, and complex conjugates the channels of the plurality of receivers arranged in reverse chronological order. Then, it is a TR (Time Reversal) waveform generated by adding the channels of the plurality of receivers in reverse order of time to generate a TR waveform in the time domain, so that the plurality of transmitting antennas of the transmitter and the plurality of receivers As the number increases, a PATR waveform is generated by flexibly expanding in the time domain using CIR (Channel Impulse Response) between the plurality of transmitting antennas of the transmitter and the plurality of receivers.

Through the TR waveform generated according to embodiments of the present invention, the TR (Time Reversal) filter, which is designed by inverting the channel impulse response (CIR) with respect to time at the transmitter and converting it to a complex conjugate, is applied to a specific user in a broadband wireless power transmission system. SINR (Signal to Interference plus Noise Ratio) can be maximized by using matched filtering between multi-path channels and transmission signals. In addition, based on the proposed TR waveform, a multi-path Wireless power transmission efficiency in a channel environment can be improved compared to the conventional WPT waveform technique.

Figure 1 is a graph showing the relationship between input signals and output signals in the operating area of an energy harvester according to the prior art.
Figure 2 is a diagram showing the configuration of a broadband multi-user wireless power transmission system considering a nonlinear energy harvester according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a method of wireless power transmission in a multi-path channel using a TR waveform according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating a method of wireless power transmission in a multi-path channel using a PATR waveform according to an embodiment of the present invention.
Figure 5 is a diagram showing TR waveforms and PATR waveforms for a plurality of users in a multi-user wireless power transmission system according to an embodiment of the present invention.
Figure 6 is a graph comparing the EH power sum to the power magnitude of the transmission waveform according to an embodiment of the present invention.
Figure 7 is a graph comparing the EH power sum with respect to an increase in the number of transmit antennas according to an embodiment of the present invention.
Figure 8 is a graph comparing the EH power sum to the number of users according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

The present invention proposes a technique for designing a broadband multi-user wireless power transmission waveform considering a nonlinear energy harvester.

TR (Time Reversal) waveform is suitable for wireless power transmission (Wimultaneous Wireless Information and Power Transfer (WPT)) considering the nonlinear operation characteristics of energy harvesters.

The TR filter, which is designed by time-inverting the CIR (Channel Impulse Response) from the transmitter of the wireless power transmission system and complex conjugate, uses matched filtering between the multi-path channel and the transmission signal for a specific user in the broadband wireless power transmission system. It was proposed to maximize SINR (Signal to Interference plus Noise Ratio).

In the present invention, a received signal composed of matched filtering with a multi-path channel for a specific user and a TR transmission signal is referred to as a desired signal.

This TR waveform can be usefully used in a wireless power transmission system using nonlinear EH (Energy Harvesting) by generating a high peak amplitude signal using the characteristics of a multi-path channel without increasing transmission power, and can be used point-to-point. It can produce the highest peak amplitude signal in a point communication system.

Existing WPT waveforms designed considering the nonlinear EH model are designed in the frequency domain and have high design complexity. On the other hand, the TR waveform can be designed simply in the time domain and at the same time configure the optimal peak amplitude signal.

In existing wireless information transmission, the TR waveform is composed of a transmitted signal by convolution with an information symbol having a probability distribution, resulting in unwanted phase rotation in the received signal.

In the present invention, since wireless power transmission does not require an information signal transmission process, the TR waveform suitable for wireless power transmission is based on the fact that an increase in the power of the received signal can be achieved by configuring the transmission signal with deterministic symbols. suggests.

The TR waveform according to an embodiment of the present invention can be the optimal waveform in a point-to-point wireless power transmission system. However, when multiple users exist, IUI (Inter User Interference) is generated in the received signal of each user, Reduces the peak amplitude and thus may reduce EH efficiency.

Therefore, based on the TR waveform according to an embodiment of the present invention, we propose a PATR (Phase Aligned Time Reversal) waveform that aligns the phases of each user's request signal and the IUI generated under the influence of other users to match. Through the PATR waveform according to an embodiment of the present invention, wireless power transmission efficiency in a multi-user environment can be greatly improved compared to the existing WPT waveform technique.

Figure 2 is a diagram showing the configuration of a broadband multi-user wireless power transmission system considering a nonlinear energy harvester according to an embodiment of the present invention.

The proposed broadband multi-user wireless power transmission system considering the nonlinear energy harvester includes a transmitter 210 with a plurality of transmission antennas and a plurality of receivers 220.

First, each parameter of the broadband multi-user wireless power transmission system model considering the proposed nonlinear energy harvester will be described with reference to FIG. 2.

A MIMO WPT system is shown including a power transmitter 210 with M transmit antennas and U receivers 220. Each of the U receivers 220 includes an energy harvester.

The received signal of the U-th receiver can be expressed as follows:

here, represents the channel between the mth transmitting antenna and the uth receiver, represents the transmission signal of the mth transmission antenna, represents noise.

The proposed TR transmission waveform, which has a period of L and repeats R times according to an embodiment of the present invention, can be expressed as the following equation:

here, represents the channel normalization factor.

In the existing broadband wireless information transmission system, the TR signal is composed of convolution with random information symbols with probability distribution. However, in order to reduce the effect of reduced received signal power due to the random phase of information symbols in wireless power transmission, the existing TR signal was proposed as a periodic signal in a deterministic form in a given multi-path channel as described above.

The channel between the mth transmitting antenna and the uth receiver according to an embodiment of the present invention can be expressed as the following equation:

here, represents the channel path loss, represents the channel gain of the lth channel tap, represents the power delay profile of the channel, where am.

The energy harvest achieved by the energy harvester of the receiver according to an embodiment of the present invention is as follows:

here, is the load resistance value, is the receiver antenna resistance value, is the thermal voltage, is the reverse saturation current, represents the diode ideality coefficient.

A transmitter 210 having a plurality of transmission antennas in a broadband multi-user wireless power transmission system considering a nonlinear energy harvester according to an embodiment of the present invention includes a plurality of receivers 220 for receiving a TR (Time Reversal) waveform transmitted from the transmitter. ) channels are arranged in reverse order of time, the channels of the plurality of receivers arranged in reverse order of time are complex conjugated, and then added to generate a TR (Time Reversal) waveform.

The transmitter 210 according to an embodiment of the present invention uses the nonlinear characteristics of the energy harvesters of a plurality of receivers in advance to reduce the effect of power reduction of the TR waveform received at the receiver due to the random phase of the information symbol in wireless power transmission. A TR waveform is generated as a deterministic periodic signal, which is a peak amplitude signal of a certain size or greater.

The transmitter 210 according to an embodiment of the present invention generates a TR waveform in the time domain by arranging the channels of the plurality of receivers in reverse chronological order to reduce complexity in the process of generating the TR waveform.

Each of the plurality of receivers 220 in the broadband multi-user wireless power transmission system considering the nonlinear energy harvester according to an embodiment of the present invention includes an energy harvester.

A plurality of receivers 220 according to an embodiment of the present invention receive a wireless power signal from a transmitter. The transmitter 210 sets a phase shift value to align the phase difference between the components of the wireless power signal to be received by the plurality of receivers 220 into in-phase, and uses the set phase shift value to align the components into in-phase. Generates a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signal.

The transmitter 210 according to an embodiment of the present invention uses the channel of the first receiver among the plurality of receivers and the first receiver to maximize the sum of the magnitude of the peak amplitude signal of the wireless power signal to be received by the plurality of receivers 220. Phase shift so that the phase between the coherent element consisting of matched filtering with the TR waveform received from and the non-coherent element resulting from non-coherent filtering with the TR waveform received from the channel of the first receiver and the second receiver matches. Set the value.

The transmitter 210 according to an embodiment of the present invention divides the peak amplitude signal from each of the plurality of receivers into a determinant in order to maximize the sum of the magnitudes of the peak amplitude signals of the wireless power signals to be received from the plurality of receivers 220. The phase component of the main eigenvector is obtained through eigenvalue decomposition for each of the plurality of receivers based on the determinant, and the optimal phase shift value is set using the phase component of the main eigenvector.

The transmitter 210 according to an embodiment of the present invention uses the set phase shift value to increase the EH (Energy Harvesting) power of each of the plurality of receivers in a wireless power transmission environment in a multi-path channel. The phase difference between IUI (Inter User Interference) and the desired signal that occurs is aligned to be in phase.

The transmitter 210 according to an embodiment of the present invention transmits wireless power signals to the plurality of receivers 220. The wireless power signal according to an embodiment of the present invention is a TR (Time It may be a Reversal waveform. By arranging the channels of the plurality of receivers in reverse chronological order to generate a TR waveform in the time domain, as the number of the plurality of transmitting antennas and the plurality of receivers increases, the plurality of transmitting antennas and the plurality of transmitting antennas of the transmitter increase. A PATR waveform can be generated by flexibly expanding in the time domain using CIR (Channel Impulse Response) between receivers.

FIG. 3 is a diagram illustrating a method of wireless power transmission in a multi-path channel using a TR waveform according to an embodiment of the present invention.

The method of generating a TR waveform in the proposed broadband multi-user wireless power transmission method considering a nonlinear energy harvester includes arranging channels of a plurality of receivers in reverse chronological order to receive a TR (Time Reversal) waveform transmitted from a transmitter. (310), generating a TR (Time Reversal) waveform using channels of a plurality of receivers arranged in reverse order of time (320), and configuring a TR waveform to be received at each receiver receiving the TR waveform from the transmitter. It includes a step 330 of generating a Phase Aligned Time Reversal (PATR) waveform by aligning the phase differences between elements to be in-phase in the transmitter.

In step 310, channels of a plurality of receivers for receiving a TR (Time Reversal) waveform transmitted from a transmitter are arranged in reverse chronological order.

According to an embodiment of the present invention, in order to reduce complexity in the process of generating the TR waveform, the TR waveform in the time domain can be generated by arranging the channels of the plurality of receivers in reverse chronological order.

In step 320, a TR (Time Reversal) waveform is generated using channels of a plurality of receivers arranged in reverse order with respect to time.

According to an embodiment of the present invention, in order to reduce the effect of power reduction of the TR waveform received at the receiver due to the random phase of the information symbol in wireless power transmission, the non-linear characteristics of the energy harvesters of the plurality of receivers are used to reduce the effect of the peak of more than a predetermined size. A TR waveform can be generated as a periodic signal in a deterministic form, which is an amplitude signal. More specifically, a TR waveform can be generated by complex conjugating the channels of a plurality of receivers arranged in reverse order of time, and then adding all of the complex conjugate channels of the plurality of receivers.

In step 330, each receiver receiving the TR waveform from the transmitter aligns the phase differences between the components of the TR waveform to be received in phase to generate a PATR (Phase Aligned Time Reversal) waveform.

According to an embodiment of the present invention, a coherent element consisting of matched filtering between a channel of a first receiver among a plurality of receivers and a TR waveform received from the first receiver, and a channel of the first receiver and a TR waveform received from the second receiver Phase differences between non-coherent elements due to non-coherent filtering with the TR waveform can be aligned in phase.

As such, according to an embodiment of the present invention, the TR waveform used in existing wireless information transmission is proposed as a form suitable for wireless power transmission. In addition, unlike the design of the existing WPT waveform in the frequency domain, the present invention allows the waveform to be designed relatively simply through CIR in the time domain. The proposed PATR waveform can increase EH power in the energy receiver by aligning the phase difference between the IUI component occurring for each user and the request signal component to be in phase in a multi-user WPT environment.

According to an embodiment of the present invention, wireless power transmission efficiency can be improved because EH power is increased by utilizing the gain of a multi-path channel. In addition, no separate communication process is required other than the channel learning process to obtain CIR from the transmitter, and power can be transmitted efficiently to EH users equipped with actual rectifiers with non-linear characteristics.

FIG. 4 is a diagram illustrating a method of wireless power transmission in a multi-path channel using a PATR waveform according to an embodiment of the present invention.

The method of generating a PATR waveform in the proposed broadband multi-user wireless power transmission method considering a nonlinear energy harvester is to convert the phase difference between the components of the wireless power signal to be received at each of the plurality of receivers receiving the wireless power signal from the transmitter into in-phase. Step 410 of setting a phase shift value for alignment, and generating a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in phase using the set phase shift value in the transmitter. It includes a generating step (420).

In step 410, a phase shift value is set to align the phase difference between the components of the wireless power signal to be received in each of the plurality of receivers that receive the wireless power signal from the transmitter to the same phase.

According to an embodiment of the present invention, matched filtering is performed between the channel of the first receiver among the plurality of receivers and the TR waveform received from the first receiver to maximize the sum of the magnitude of the peak amplitude signal of the received wireless power signal. The phase shift value may be set so that the phase between the coherent element and the non-coherent element resulting from non-coherent filtering between the channel of the first receiver and the TR waveform received from the second receiver matches the phase.

According to an embodiment of the present invention, in order to maximize the sum of the magnitude of the peak amplitude signal of the received wireless power signal, the peak amplitude signal in each of the plurality of receivers is expressed as a determinant, and the plurality of receivers are based on the determinant. The phase component of the main eigenvector can be obtained through eigenvalue decomposition for each, and the optimal phase shift value can be set using the phase component of the main eigenvector.

In step 420, the transmitter uses the set phase shift value to generate a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in phase.

According to an embodiment of the present invention, IUI occurring in each of a plurality of receivers in a wireless power transmission environment in a multi-path channel using the set phase shift value to increase EH (Energy Harvesting) power in each of the plurality of receivers The phase difference between (Inter User Interference) and desired signals can be aligned to be in phase.

The wireless power signal to be received by each of the plurality of receivers according to an embodiment of the present invention is a complex conjugate of the channels of the plurality of receivers arranged in reverse chronological order, and the channels of the plurality of receivers arranged in reverse chronological order. Then, it may be a TR (Time Reversal) waveform generated by addition.

According to an embodiment of the present invention, the channels of the plurality of receivers are arranged in reverse order of time to generate a TR waveform in the time domain, so that the transmitter increases as the number of the plurality of transmitting antennas and the plurality of receivers of the transmitter increases. A PATR waveform can be generated by flexibly expanding in the time domain using CIR (Channel Impulse Response) between the plurality of transmitting antennas and the plurality of receivers.

Hereinafter, a PATR waveform design process for multiple users in a wireless power transmission system according to an embodiment of the present invention will be described.

First, the proposed PATR waveform design process in a system for multiple receivers with a single transmit antenna (M = 1) and two users (U = 2) is explained as an example.

The proposed TR waveform that achieves optimal performance in a single-user environment can be constructed by arranging the channels between two users in the transmit antenna in reverse order with respect to time, complex conjugate, and then adding them, which can be expressed as the following equation:

Since most of the power obtained from the nonlinear energy harvester is obtained from the peak amplitude signal of the received signal, the peak amplitude signal of the received signal can be analyzed. The peak amplitude signal of each user's received signal can be expressed as follows:

The peak amplitude signal of each user's received signal is divided into a coherent term consisting of coherent filtering between that user's channel and the transmitted signal, and a non-coherent term, which is an IUI component due to non-coherent filtering with the transmitted signal for other users. It consists of runt elements (non-coherent terms).

The peak amplitude signal of the received signal, which is composed of the sum of the two signals, may decrease in size due to the phase difference between the two components.

The phase difference between the two components is equal to the phase of the non-coherent component and can be estimated at the transmitter as:

The purpose of the PATR waveform according to an embodiment of the present invention is to increase the size of the peak amplitude signal of the received signal by aligning the phases of the two components constituting the peak amplitude signal of the received signal to be in phase, so that the transmitted signal phase at the transmitter is Perform a pre-rotation of . Therefore, the transmitted signal of the PATR waveform has a phase shift value class can be added and designed as follows:

here, class Can be set as follows using the estimated phase difference value:

or

Applying the proposed PATR waveform, the peak amplitude signal component of each user's received signal can be expressed as the following equation:

In this way, the phases of the coherent and non-coherent components that make up the peak amplitude signal of the received signal for both users are completely matched. Therefore, the magnitude of the peak amplitude signal of the received signal, which is the sum of the two components, increases. In conclusion, the output DC power of the energy harvester increases.

Figure 5 is a diagram showing TR waveforms and PATR waveforms for a plurality of users in a multi-user wireless power transmission system according to an embodiment of the present invention.

Figure 5(a) is a graph showing the TR waveforms of each of the two users, and Figure 5(b) is a graph showing the PATR waveforms of each of the two users.

In the graph of FIG. 5, the received signal of the TR waveform according to the embodiment of the present invention has a reduced amplitude of the peak amplitude signal of the received signal, which is the sum of the two elements, due to the phase difference between the coherent element and the non-coherent element. It can be confirmed that the phases of the two elements of the received signal of the PATR waveform according to the embodiment of the invention match, and the magnitude of the peak amplitude signal of the received signal increases.

Next, the proposed PATR waveform design process in a system for multiple receivers with multiple transmit antennas and multiple users is explained as an example.

As the number of multiple transmit antennas and multiple users increases, there is a limit to estimating the phase difference of all coherent elements and non-coherent elements and reflecting this to achieve perfectly aligned received signals from all users.

Therefore, the waveform is designed to maximize the sum of the peak amplitude signal magnitudes of the received signals of all users by setting the phase shift value so that the coherent elements and non-coherent elements in each user match as much as possible.

The transmitted signal of the mth transmitting antenna can be expressed as the following equation:

The peak amplitude signal component of the u-th user's received signal can be expressed as the following equation:

From the peak amplitude signal of the received signal, the actual channel between all users at all transmitting antennas is defined as follows:

defined Using , the peak amplitude signal of the received signal can be expressed as the following equation:

Then, the peak amplitude signals of all users' received signals can be expressed in the form of a matrix as shown below:

The sum of squares of the peak amplitude signals of all received signals can be expressed as follows:

A phase vector that maximizes the above components by the Rayleigh quotient Is It consists of the phase of the dominant eigenvector corresponding to the largest eigenvalue of and can be expressed as the following equation:

here, Is It is the largest eigenvector of .

By applying the obtained optimal phase shift value, the PATR waveform in a multi-user environment can be designed as follows:

Figure 6 is a graph comparing the EH power sum to the power magnitude of the transmission waveform according to an embodiment of the present invention.

Referring to Figure 6, when there are 2 and 4 users, the sum of the users' EH (Energy Harvesting) power according to the power size of each transmission waveform was compared.

The ST waveform is a waveform proposed in the prior art [1] and is the optimal WPT waveform in linear EH. In the nonlinear EH model, the TR and PATR waveforms show better EH performance compared to the ST waveform, and the PATR waveform achieves better received power performance than the TR waveform due to the influence of phase alignment of the received signal.

Figure 7 is a graph comparing the EH power sum with respect to an increase in the number of transmit antennas according to an embodiment of the present invention.

Referring to Figure 7, when there are 4 users and the transmission power is fixed, the sum of the users' EH powers according to the increase in the number of transmission antennas is compared.

It can be seen that under constant transmission power, the sum of the EH powers of the TR and PATR waveforms increases as the number of transmit antennas increases, and PATR achieves a reception power approximately 1.33 times higher than the TR waveform.

Figure 8 is a graph comparing the EH power sum to the number of users according to an embodiment of the present invention.

Referring to FIG. 8, when the number of transmission antennas and transmission power are fixed, the sum of reception power achieved depending on the number of users is compared.

In PATR, as the number of EH users increases, a gain in received power can be obtained through phase alignment, resulting in EH power up to 2.43 times greater than that of the TR waveform. Through this, it can be confirmed that the proposed PATR achieves a higher sum of received power as the number of users increases at a constant number of transmit antennas and transmit power.

In a WPT system with multiple users through the PATR waveform according to an embodiment of the present invention, the phases of IUI occurring for each user are aligned in-phase to increase the peak amplitude of the received signal, so that all users can achieve EH power gain. You can get it.

According to an embodiment of the present invention, wireless power is continuously supplied to multiple small wireless devices at the same time through a broadband multi-user wireless power transmission waveform considering the nonlinear energy harvester, providing convenience in management and maintenance, and spatial constraints in wireless device placement. can be alleviated.

In addition, according to an embodiment of the present invention, power can be appropriately supplied to multiple users at the same time, so it is suitable for application to an IoT network or wireless sensor network where many small wireless devices exist, which are increasing exponentially with the development of communication technology. do.

As such, the present invention supplies power wirelessly in a system with multiple wireless devices, making it convenient to manage and maintain the devices, and spatial constraints on wireless device placement are alleviated, making it suitable for application to IoT networks.

With the development of wireless communication technology and the formation of IoT networks in homes, offices, and factories, there is an increasing demand for technology that wirelessly supplies power from a distance to various wireless devices that make up the network. If power can be supplied wirelessly, it will provide great convenience in maintenance and management, and the proposed technology can be used appropriately because devices can be freely placed.

The proposed technology has excellent EH performance in an environment where many devices exist, so it is advantageous for continuously supplying power in a network with many devices. Therefore, the demand for the technology proposed in the present invention will increase to meet the wireless charging needs of IoT networks where the number of wireless devices is increasing.

The device described above may be implemented with hardware components, software components, and/or a combination of hardware components and software components. For example, devices and components described in embodiments may include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), It may be implemented using one or more general-purpose or special-purpose computers, such as a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. A processing device may execute an operating system (OS) and one or more software applications that run on the operating system. Additionally, a processing device may access, store, manipulate, process, and generate data in response to the execution of software. For ease of understanding, a single processing device may be described as being used; however, those skilled in the art will understand that a processing device includes multiple processing elements and/or multiple types of processing elements. It can be seen that it may include. For example, a processing device may include a plurality of processors or one processor and one controller. Additionally, other processing configurations, such as parallel processors, are possible.

Software may include a computer program, code, instructions, or a combination of one or more of these, which may configure a processing unit to operate as desired, or may be processed independently or collectively. You can command the device. Software and/or data may be used on any type of machine, component, physical device, virtual equipment, computer storage medium or device to be interpreted by or to provide instructions or data to a processing device. It can be embodied in . Software may be distributed over networked computer systems and stored or executed in a distributed manner. Software and data may be stored on one or more computer-readable recording media.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., singly or in combination. Program instructions recorded on the medium may be specially designed and configured for the embodiment or may be known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. -Includes optical media (magneto-optical media) and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include machine language code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

As described above, although the embodiments have been described with limited examples and drawings, various modifications and variations can be made by those skilled in the art from the above description. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent.

Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the claims described below.

Claims (20)

In a method of wireless power transmission in a multi-path channel,
Arranging channels of a plurality of receivers for receiving a TR (Time Reversal) waveform transmitted from a transmitter in reverse chronological order; and
A step of generating a TR (Time Reversal) waveform using channels of a plurality of receivers arranged in reverse order of time.
Including,
A step of generating a PATR (Phase Aligned Time Reversal) waveform by aligning the phase difference between the components of the TR waveform to be received at each receiver receiving the TR waveform from the transmitter to be in phase at the transmitter.
It further includes,
The step of generating a PATR waveform by aligning the phase difference between the components of the TR waveform to be received at each receiver receiving the TR waveform from the transmitter to be in phase at the transmitter,
A coherent element consisting of matched filtering between the channel of the first receiver among the plurality of receivers and the TR waveform received from the first receiver, and non-coherent filtering between the channel of the first receiver and the TR waveform received from the second receiver. aligning the phase differences between non-coherent elements into in-phase.
Method for wireless power transmission in multipath channel. In a method of wireless power transmission in a multi-path channel,
Arranging channels of a plurality of receivers for receiving a TR (Time Reversal) waveform transmitted from a transmitter in reverse chronological order; and
A step of generating a TR (Time Reversal) waveform using channels of a plurality of receivers arranged in reverse order of time.
Including,
The step of generating a TR waveform using channels of a plurality of receivers arranged in reverse chronological order includes:
In wireless power transmission, in order to reduce the effect of power reduction of the TR waveform received at the receiver due to the random phase of the information symbol, the non-linear characteristics of the energy harvesters of the plurality of receivers are used to generate a deterministic signal with a peak amplitude of more than a predetermined size. Generating a TR waveform as a periodic signal of
Method for wireless power transmission in multipath channel. According to paragraph 1,
The step of generating a TR waveform using channels of a plurality of receivers arranged in reverse chronological order includes:
After complex-conjugating the channels of a plurality of receivers arranged in the reverse order of time, generating a TR waveform by adding all of the complex-conjugated channels of the plurality of receivers.
Method for wireless power transmission in multipath channel. According to paragraph 1,
The step of arranging channels of a plurality of receivers for receiving the TR waveform transmitted from the transmitter in reverse chronological order,
In order to reduce the complexity of the TR waveform generation process, the TR waveform in the time domain is generated by arranging the channels of the plurality of receivers in reverse order with respect to time.
Method for wireless power transmission in multipath channel. In a method of wireless power transmission in a multi-path channel,
Setting a phase shift value to align phase differences between components of a wireless power signal to be received in each of a plurality of receivers that receive a wireless power signal from a transmitter to be in phase; and
Generating a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in phase using the set phase shift value in the transmitter.
Including,
The step of setting a phase shift value to align the phase difference between the components of the wireless power signal to be received from each of the plurality of receivers that receive the wireless power signal from the transmitter to be in phase,
A coherent element consisting of matched filtering between a channel of a first receiver among a plurality of receivers and a TR waveform received from the first receiver to maximize the sum of the magnitude of the peak amplitude signal of the received wireless power signal, and the first Setting the phase shift value to match the phase between the channel of the receiver and the non-coherent elements due to non-coherent filtering with the TR waveform received at the second receiver.
Method for wireless power transmission in multipath channel. According to clause 5,
In order to maximize the sum of the magnitude of the peak amplitude signal of the received wireless power signal, the peak amplitude signal at each of the plurality of receivers is expressed as a determinant, and eigenvalue decomposition for each of the plurality of receivers is performed based on the determinant. Obtain the phase component of the main eigenvector and set the phase shift value using the phase component of the main eigenvector.
Method for wireless power transmission in multipath channel. In a method of wireless power transmission in a multi-path channel,
Setting a phase shift value to align phase differences between components of a wireless power signal to be received in each of a plurality of receivers that receive a wireless power signal from a transmitter to be in phase; and
Generating a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in phase using the set phase shift value in the transmitter.
Including,
The step of generating a PATR (Phase Aligned Time Reversal) waveform that maximizes the sum of the peak amplitude signals of the wireless power signals aligned in phase using the set phase shift value in the transmitter,
In order to increase the EH (Energy Harvesting) power in each of the plurality of receivers, the set phase shift value is used to detect Inter User Interference (IUI) and requests (IUI) occurring in each of the plurality of receivers in a wireless power transmission environment in a multi-path channel ( desired) to align the phase difference between signals to be in-phase.
Method for wireless power transmission in multipath channel. According to clause 5,
The wireless power signal to be received by each of the plurality of receivers is:
A TR (Time Reversal) waveform generated by arranging the channels of a plurality of receivers in reverse order of time, complex conjugate the channels of a plurality of receivers arranged in reverse order of time, and then adding them together.
Method for wireless power transmission in multipath channel. According to clause 8,
By arranging the channels of the plurality of receivers in reverse chronological order to generate a TR waveform in the time domain, as the number of the plurality of transmitting antennas and the plurality of receivers increases, the plurality of transmitting antennas and the plurality of transmitting antennas of the transmitter increase. Generates a PATR waveform by flexibly expanding in the time domain using CIR (Channel Impulse Response) between receivers.
Method for wireless power transmission in multipath channel. In a multi-user wireless power transmission system including a transmitter with a plurality of transmission antennas and a plurality of receivers,
The transmitter is,
The channels of a plurality of receivers for receiving the TR (Time Reversal) waveform transmitted from the transmitter are arranged in reverse order of time, the channels of the plurality of receivers arranged in reverse order of time are complex conjugated, and then added to TR (Time Reversal) generates a waveform,
In wireless power transmission, in order to reduce the effect of power reduction of the TR waveform received at the receiver due to the random phase of the information symbol, the non-linear characteristics of the energy harvesters of the plurality of receivers are used to generate a deterministic signal with a peak amplitude of more than a predetermined size. Generating a TR waveform as a periodic signal of
Multi-user wireless power transmission system. According to clause 10,
The transmitter is,
In order to reduce the complexity of the TR waveform generation process, the TR waveform in the time domain is generated by arranging the channels of the plurality of receivers in reverse order with respect to time.
Multi-user wireless power transmission system. In a multi-user wireless power transmission system including a transmitter with a plurality of transmission antennas and a plurality of receivers,
The plurality of receivers,
Each includes an energy harvester,
The transmitter is,
Set a phase shift value to align the phase difference between the components of the received wireless power signal into in-phase, and use the set phase shift value to maximize the sum of the peak amplitude signals of the wireless power signal aligned in-phase. Generates a PATR (Phase Aligned Time Reversal) waveform,
A coherent element consisting of matched filtering between a channel of a first receiver among a plurality of receivers and a TR waveform received from the first receiver to maximize the sum of the magnitude of the peak amplitude signal of the received wireless power signal, and the first Setting the phase shift value to match the phase between the channel of the receiver and the non-coherent elements due to non-coherent filtering with the TR waveform received at the second receiver.
Multi-user wireless power transmission system. According to clause 12,
The transmitter is,
In order to maximize the sum of the magnitude of the peak amplitude signal of the received wireless power signal, the peak amplitude signal at each of the plurality of receivers is expressed as a determinant, and eigenvalue decomposition for each of the plurality of receivers is performed based on the determinant. Obtain the phase component of the main eigenvector and set the phase shift value using the phase component of the main eigenvector.
Multi-user wireless power transmission system. According to clause 12,
The transmitter is,
In order to increase the EH (Energy Harvesting) power in each of the plurality of receivers, the set phase shift value is used to detect Inter User Interference (IUI) and requests (IUI) occurring in each of the plurality of receivers in a wireless power transmission environment in a multi-path channel ( desired) to align the phase difference between signals to be in-phase.
Multi-user wireless power transmission system. According to clause 12,
The transmitter is,
Transmitting a wireless power signal to the plurality of receivers, the wireless power signal arranges the channels of the plurality of receivers in reverse chronological order, and complex conjugates the channels of the plurality of receivers arranged in reverse chronological order, It is a TR (Time Reversal) waveform created by adding -,
By arranging the channels of the plurality of receivers in reverse chronological order to generate a TR waveform in the time domain, as the number of the plurality of transmitting antennas and the plurality of receivers increases, the plurality of transmitting antennas and the plurality of transmitting antennas of the transmitter increase. Generates a PATR waveform by flexibly expanding in the time domain using CIR (Channel Impulse Response) between receivers.
Multi-user wireless power transmission system. delete delete delete delete delete