Apparatus and method for RF beamforming wireless power transmission based on TDD communication

A power transmitting unit (PTU) for wireless power transmission (WPT) includes a communication transceiver and a power controller. The communication transceiver connects a communication link with at least one power receiving unit (PRU) through legacy communication and exchanges parameters necessary for the WPT through the connected communication link. The power controller is configured to transmit, to the PRU, a PTU beacon containing information about a dedicated power slot (DPS) allocated to the PRU in a super frame including a plurality of DPSs, to receive a PRU beacon from the PRU, to extract a phase difference between a plurality of antennas by analyzing a continuous wave (CW) of the PRU beacon, and to transmit power to the PRU in the allocated DPS in consideration of the phase difference.

TECHNICAL FIELD

The present disclosure relates in general to wireless power transmission (WPT) technology and, more particularly, to an apparatus and method for radio frequency (RF) beamforming WPT based on time division duplex (TDD) communication.

BACKGROUND

Wireless power transmission (WPT) mainly includes non-radiative techniques using electromagnetic induction or magnetic resonance and radiative techniques using a radio frequency (RF) beam. In the non-radiative techniques, power is transferred over short distances by magnetic fields using inductive coupling between coils of wire or by electric fields using capacitive coupling between metal electrodes. In the radiative techniques, power is transferred by beams of electromagnetic radiation.

Among the radiative techniques, RF wireless power transmission (RF WPT) refers to a technique of wirelessly transmitting electric power through radio waves. The RF WPT technique not only achieves longer range transmission, but also allows omnidirectional transmission to several receiver devices. However, power efficiency is very low.

SUMMARY

The present disclosure provides an apparatus and method for controlling radio frequency (RF) beamforming wireless power transmission (WPT) based on time division duplex (TDD) communication.

According to embodiments of the present disclosure, a power transmitting unit (PTU) for wireless power transmission (WPT) includes a communication transceiver connecting a communication link with at least one power receiving unit (PRU) through legacy communication and exchanging parameters necessary for the WPT through the connected communication link; and a power controller configured to transmit, to the PRU, a PTU beacon containing information about a dedicated power slot (DPS) allocated to the PRU in a super frame including a plurality of DPSs, to receive a PRU beacon from the PRU, to extract a phase difference between a plurality of antennas by analyzing a continuous wave (CW) of the PRU beacon, and to transmit power to the PRU in the allocated DPS in consideration of the phase difference.

In the PTU, transmitting the PTU beacon, receiving the PRU beacon, and transmitting the power may be performed through a frequency region adjacent to a guard band in an industrial scientific medical (ISM) band, and the adjacent frequency region may occupy a predetermined band from each of a start frequency and an end frequency of the ISM band.

The super frame may be defined as a signal period from transmission of one PTU beacon to transmission of a next PTU beacon, and the super frame may contain 2SODPSs according to a slot order (SO) value for defining a length of a field in a system. A first DPS of 2SODPSs may be used for PTU beacon transmission, and a second DPS to a 2SOth DPS of 2SODPSs may be used for PRU beacon transmission and power transmission.

According to embodiments of the present disclosure, a power receiving unit (PRU) for wireless power transmission (WPT) includes a communication transceiver connecting a communication link with a power transmitting unit (PTU) through legacy communication and exchanging parameters necessary for the WPT through the connected communication link; and a power controller configured to receive, from the PTU, a PTU beacon containing information about a dedicated power slot (DPS) allocated to the PRU in a super frame including a plurality of DPSs, to transmit a PRU beacon to the PTU in the allocated DPS, and to receive power from the PTU in the allocated DPS.

In the PRU, receiving the PTU beacon, transmitting the PRU beacon, and receiving the power may be performed through a frequency region adjacent to a guard band in an industrial scientific medical (ISM) band, and the adjacent frequency region may occupy a predetermined band from each of a start frequency and an end frequency of the ISM band.

The super frame may be defined as a signal period from transmission of one PTU beacon to transmission of a next PTU beacon, and the super frame may contain 2SODPSs according to a slot order (SO) value for defining a length of a field in a system. A first DPS of 2SODPSs may be used for PTU beacon transmission, and a second DPS to a 2SOth DPS of 2SODPSs may be used for PRU beacon transmission and power transmission.

According to embodiments of the present disclosure, a method for controlling wireless power transmission (WPT) at a power transmitting unit (PTU) includes, at a communication transceiver, connecting a communication link with at least one power receiving unit (PRU) through legacy communication; at the communication transceiver, exchanging parameters necessary for the WPT through the connected communication link; at a power controller, transmitting, to the PRU, a PTU beacon containing information about a dedicated power slot (DPS) allocated to the PRU in a super frame including a plurality of DPSs; at the power controller, receiving a PRU beacon from the PRU; at the power controller, extracting a phase difference between a plurality of antennas by analyzing a continuous wave (CW) of the PRU beacon; and at the power controller, transmitting power to the PRU in the allocated DPS in consideration of the phase difference.

In the method, transmitting the PTU beacon, receiving the PRU beacon, and transmitting the power may be performed through a frequency region adjacent to a guard band in an industrial scientific medical (ISM) band, and the adjacent frequency region may occupy a predetermined band from each of a start frequency and an end frequency of the ISM band.

The super frame may be defined as a signal period from transmission of one PTU beacon to transmission of a next PTU beacon, and the super frame may contain 2SODPSs according to a slot order (SO) value for defining a length of a field in a system. A first DPS of 2SODPSs may be used for PTU beacon transmission, and a second DPS to a 2SOth DPS of 2SODPSs may be used for PRU beacon transmission and power transmission.

According to embodiments of the present disclosure, a method for controlling wireless power transmission (WPT) at a power receiving unit (PRU) includes, at a communication transceiver, connecting a communication link with a power transmitting unit (PTU) through legacy communication; at the communication transceiver, exchanging parameters necessary for the WPT through the connected communication link; at a power controller, receiving, from the PTU, a PTU beacon containing information about a dedicated power slot (DPS) allocated to the PRU in a super frame including a plurality of DPSs; at the power controller, transmitting a PRU beacon to the PTU in the allocated DPS; and at the power controller, receiving power from the PTU in the allocated DPS.

In the method, receiving the PTU beacon, transmitting the PRU beacon, and receiving the power may be performed through a frequency region adjacent to a guard band in an industrial scientific medical (ISM) band, and the adjacent frequency region may occupy a predetermined band from each of a start frequency and an end frequency of the ISM band.

The super frame may be defined as a signal period from transmission of one PTU beacon to transmission of a next PTU beacon, and the super frame may contain 2SODPSs according to a slot order (SO) value for defining a length of a field in a system. A first DPS of 2SODPSs may be used for PTU beacon transmission, and a second DPS to a 2SOth DPS of 2SODPSs may be used for PRU beacon transmission and power transmission.

According to the present disclosure, performing the WPT through RF beamforming can overcome very low power efficiency of typical RF WPT technique. In particular, each antenna of an antenna array forms a directional beam pattern and thereby transmits power only to a focused target. This transmission scheme can increase power transmission efficiency.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that the disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

In the following description of embodiments, techniques that are well known in the art and not directly related to the present disclosure are not described. This is to clearly convey the subject matter of the present disclosure by omitting an unnecessary explanation. For the same reason, some elements in the drawings are exaggerated, omitted, or schematically illustrated. Also, the size of each element does not entirely reflect the actual size. In the disclosure, the same or corresponding elements are denoted by the same reference numerals.

Wireless power transmission (WPT) according to embodiments of the present disclosure is made through radio frequency (RF) beamforming and is controlled based on time division duplex (TDD) communication. At the outset, a WPT system according to an embodiment of the present disclosure will be described.FIG. 1is a block diagram illustrating an RF beamforming WPT system based on TDD communication according to an embodiment of the present disclosure.

Referring toFIG. 1, the WPT system according to an embodiment includes a power transmitting unit (PTU)100and at least one power receiving unit (PRU)200. The PTU100is an apparatus that wirelessly transmits power to the PRU200, and the PRU200is an apparatus that wirelessly receives power from the PTU100. That is, the PRU200is charged through WPT.

The PTU100includes a communication transceiver110(also referred to as L-TX/RX) and a power controller120(also referred to as P-TX/RX). The communication transceiver110is a component for communicating with the PRU200through legacy communication. The power controller120transmits a PTU beacon to the PRU200and receives a PRU beacon from the PRU200. Also, the power controller120wirelessly transmits power to the PRU200. In particular, the power controller120includes an antenna array composed of a plurality of antennas. Each antenna forms a directional beam pattern having a specific angle by using constructive or destructive interference between signals and transmits power only to one corresponding PRU200in a time resource allocated only to the corresponding PRU200, that is, in a dedicated power slot (DPS). This transmission scheme can increase power transmission efficiency.

The PRU200includes a communication transceiver210(also referred to as L-TX/RX) and a power controller220(also referred to as P-TX/RX). The communication transceiver210is a component for communicating with the PTU100through legacy communication. The power controller220transmits the PRU beacon to the PTU100and receives the PTU beacon from the PTU100. Also, the power controller220wirelessly receives power from the PTU100.

Now, the timing of performing WPT between the PTU100and the PRU200will be described.FIG. 2is a diagram illustrating the timing for WPT according to an embodiment of the present disclosure.

Referring toFIG. 2, at first timing T1, the communication transceiver110of the PTU100and the communication transceiver210of the PRU200perform legacy communication with each other through a suitable protocol, e.g., Zigbee, Wi-Fi, BLE, or ULP, thereby establish a communication link between the PTU100and the PRU200, and exchange information necessary for WPT.

At second timing T2, the power controller120of the PTU100transmits the PTU beacon containing scheduling information to the PRU200. The PTU beacon contains information about a slot allocated to the PRU200in a super frame (SF) including a plurality of DPSs.

Then, at third timing T3, the power controller130of the PRU200transmits the PRU beacon containing a continuous wave (CW) to the PTU100. Thus, analyzing the CW of the PRU beacon, the power controller120of the PTU100can extract a phase difference between the PRU200and respective antennas of the power controller120.

Then, at fourth timing T4, the power controller120of the PTU100transmits intensively power in a slot allocated to the corresponding PRU200in consideration of the extracted phase difference.

Next, frequency resources used for WPT according to an embodiment of the present disclosure will be described.FIGS. 3 and 4are diagrams illustrating a frequency band used for WPT according to an embodiment of the present disclosure.

Referring toFIG. 3, basically, an industrial scientific medical (ISM) band is used. The ISM band has a guard band (GB) to avoid interference between different legacy communications. That is, the GB is an empty frequency band used to prevent excess leakage of a radio signal from affecting another allocated band. All of the PTU beacon transmission, the PRU beacon transmission, and the power transmission are performed through frequency regions (U) each adjacent to the GB provided for the legacy communication (L) in the ISM band. That is, in the ISM band, the legacy communication (L) is performed between both adjacent frequency regions (U).

Referring toFIG. 4, frequencies for the adjacent frequency regions (U) are allocated in units of a resource block (i.e., RF WPT PRB) of 1 MHz. The reason is that the PTU beacon transmission, the PRU beacon transmission, and the power transmissions should occupy 1 MHz or less. For example, the adjacent frequency region (U) may occupy a predetermined band (e.g., 5 MHz) from each of the start frequency (S) and the end frequency (E) of the 2.4 or 5.8 GHz ISM band. In this case, the adjacent frequency regions (U) may be, for example, a 2.4-2.405 GHz band, a 2.495-2.5 GHz band, a 5.725-5.730 GHz band, and/or a 5.870-5.875 GHz band.

As such, when the resource blocks (RF WPT PRBs) each having bandwidth of 1 MHz are allocated to occupy a 5 MHz band from each of the start frequency (S) and the end frequency (E), the 2.4 or 5.8 GHz ISM band has ten resource blocks (PRBs).

Next, a super frame which is a time resource used in WPT according to an embodiment of the present disclosure will be described.FIG. 5is a diagram illustrating a frame structure used for WPT according to an embodiment of the present disclosure.

Referring toFIG. 5, the WPT is controlled using a super frame (SF) structure based on TDD communication. One SF has a plurality of slots, i.e., dedicated power slots (DPSs). One SF is defined as a signal period from transmission of one PTU beacon to transmission of the next PTU beacon. One super frame (SF) contains 2SODPSs according to a slot order (SO) value for defining the length of a field in the system. The SO value is defined in IE field part of Super Frame Specification of the PRU beacon, and may be specified in the range from 0 to 7. The first slot DPS #0is necessarily used for the PTU. That is, the first slot DPS #0is used for PTU beacon transmission. The next slots, that is, from the second slot DPS #1to the 2SOth slot DPS #2SO−1 are used for PRU beacon transmission and power transmission. In such slots, a sub-slot (RS) for the PRU beacon transmission and a sub-slot (PS) for the power transmission are defined. The PTU beacon is used for scheduling power transmission to a plurality of PRUs200according to priorities and used for synchronization of the plurality of PRUs200through variable DPS allocation.

The PRU beacon may be received in every DPS according to a request of the PRU. Alternatively, after the PRU beacon is received once, the DPS may be continuously allocated, and the sub-slot (RS) for the PRU beacon and an empty weight sub-slot (VS) may be used for WPT. The PRU200to which the corresponding slot (DPS) is allocated transmits the PRU beacon to the PTU100. The PRU beacon contains a beacon part having the requirements of the PRU200for receiving power and a continuous wave (CW) behind the beacon part.

Hereinafter, a method for TDD communication based WPT according to an embodiment of the present disclosure will be described.FIG. 6is a flow diagram illustrating a method for TDD communication based WPT according to an embodiment of the present disclosure.

Referring toFIG. 6, when power is supplied, the PTU100enters an idle mode at step S100.

In addition, when receiving an RF beamforming WPT start command, the PTU100is changed to a setting state at step S200. In the setting state, the PTU100establishes a communication link with at least one PRU200using legacy communication. At this time, the communication transceiver110of the PTU100and the communication transceiver210of the PRU200may use a suitable communication technique (e.g., Zigbee, Wi-Fi, BLE, ULP) available in the ISM band to establish a communication link with each other. When a plurality of PRUs200are connected through links, the PTU100determines the priorities of the PRUs200sequentially, that is, PRU #1, PRU #2, . . . , PRU #k (e.g., k=127). In addition, the communication transceiver110of the PTU100and the communication transceiver210of the PRU200exchange messages containing information necessary for WPT through the established communication link.

Specifically, when the communication link is established between the PTU100and the PRU200through the legacy communication, the communication transceiver110of the PTU100transmits an RF WPT Connection message to the PRU200at step S210so as to declare the start of WPT. Upon receiving the RF WPT Connection message through the communication transceiver210, the PRU200recognizes the start of WPT.

Then, at step S220, the PRU200transmits a PRU Static Parameter message to the PTU100through the communication transceiver210, and thus the PTU100receives the PRU Static Parameter message through the communication transceiver110. The PRU Static Parameter message contains static parameters indicating static characteristics of the PRU200. The static parameters of the PRU200may include, for example, rectifier maximum power, rectifier maximum voltage, rectifier maximum constant voltage, and rectifier desired constant voltage.

Then, at step S230, the PTU100transmits a PTU Static Parameter message to the PRU200through the communication transceiver110, and thus the PRU200receives the PTU Static Parameter message through the communication transceiver210. The PTU Static Parameter message contains static parameters indicating static characteristics of the PTU100. The static parameters of the PTU100may include, for example, PTU RF WPT transmit power, PTU support number of devices (which means the maximum number of PRUs to which the PTU100can allocate DPSs to be used for WPT), PTU TX output adjustment (which means the amount of radiation power of the PTU100), tREP parameter option (which means a time difference between PRU beacon transmission and short-period WPT in TDD-based signal exchange), and PRU ID distribution (which means a unique ID of each PRU allocated by the PTU100).

Then, at step S240, the PRU200transmits a PRU Dynamic Parameter message to the PTU100through the communication transceiver210, and thus the PTU100receives the PRU Dynamic Parameter message through the communication transceiver110. The PRU Dynamic Parameter message contains dynamic parameters indicating dynamic characteristics of the PRU200. The dynamic parameters of the PRU200may include, for example, rectifier dynamic voltage, rectifier dynamic current, battery dynamic voltage, battery dynamic current, battery temperature, and rectifier desired minimum voltage.

Then, at step S250, the PTU100transmits a PTU Probe Response message indicating a final approval of WPT to the PRU200through the communication transceiver110, and thus the PRU200receives the PTU Probe Response message through the communication transceiver210. The PTU Probe Response message contains parameters for requirements and information necessary for WPT. The parameters contained in the PTU Probe Response message may include, for example, requested CW time (which means the duration time of a continuous wave (CW)), requested CW frequency (which means the frequency of CW), RF WPT priority order of designated PRU number (which means the WPT priority of a corresponding PRU200), and current number of accessed PRUs (which means the total number of connected PRUs200).

After the message exchange between the PTU100and the PRU200is completed as described above, the PTU100allocates slots (DPSs) for WPT to the plurality of PRUs200having priorities determined through scheduling. Then, at step S300, the PTU100transmits, to the PRU200through the power controller120, the PTU beacon containing information on the slot (DPS) allocated to the corresponding PRU200. Therefore, the PRU200receives the PTU beacon through the power controller220. Then, the PRU200is synchronized on the super frame according to the allocated slot (DPS). The PTU beacon is transmitted in DPS #0which is the first slot in the super frame including a plurality of slots (DPSs). Particularly, the PTU beacon is transmitted through the above-mentioned frequency region (U) adjacent to the guard band (GB) of the ISM band.

Then, at step S400, the PRU200transmits the PRU beacon in the allocated slot (at least one of the DPS #1to #127) to the PTU100through the communication transceiver210. Therefore, the PTU100receives the PRU beacon through the communication transceiver110. The PRU beacon contains the CW of a specific frequency. Particularly, the PRU beacon is also transmitted through the adjacent frequency region (U).

After receiving the PRU beacon, the PTU100extracts a phase difference between the PRU200and each antennas of the PTU100by analyzing the CW of the PRU beacon. Then, based on the extracted phase difference, the PTU100transmits power to the PRU200through the power controller120. Therefore, the PRU200can receive power during the allocated slot (DPS) through the power controller220. This power is also transmitted through the adjacent frequency region (U).

Meanwhile, after the step S200, the PTU100continuously monitors the states of the plurality of PRUs200through the legacy communication. If any problem such as foreign object damage (FOD) or over charge occurs, the PTU100terminates and initializes a procedure.

The above-described methods according to various embodiments of the present disclosure may be implemented as instructions stored in a non-transitory computer-readable recording medium in a programming module form. When the instructions are executed by a processor, the processor may execute a function corresponding to the instructions. The non-transitory computer-readable recording medium may include magnetic media such as a hard disk, a floppy disk, and a magnetic tape, optical media such as a compact disc read only memory (CD-ROM) and a digital versatile disc (DVD), magneto-optical media such as a floptical disk, and hardware devices specially configured to store and perform a program instruction. In addition, the program instructions may include high class language codes, which can be executed in a computer by using an interpreter, as well as machine codes made by a compiler. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the various embodiments, and vice versa.

While the present disclosure has been particularly shown and described with reference to an exemplary embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the present disclosure as defined by the appended claims.