IM3-based beam backtracking wireless power transmission system and method

Abstract

The invention discloses a beam backtracking wireless power transmission system and method based on IM3. The system comprises a power supply end and a power receiving end. The power receiving end comprises a rectifier module, a filter module, an energy receiving antenna, a pilot signal transmitting antenna and a second harmonic transmitting antenna. The power supply end comprises a phase processing module, an energy emission phased-array antenna, a pilot signal receiving phased-array antenna and a second harmonic receiving phased-array antenna. And the phase processing module is used for generating a phase conjugate signal according to the second harmonic signal and the third-order intermodulation signal. By utilizing the characteristic that the second harmonic signal and the third-order intermodulation signal from the receiving end carry the same offset phase, physical offset of the offset phase can be realized without an additional calibration module, and a necessary phase detector and a digital compensation chip in the traditional scheme are omitted; and the dynamic adaptation of the power supply end to the power receiving end in the moving state can be realized.

Description

Technical Field

[0001] This invention belongs to the field of power transmission technology, specifically relating to a beamback wireless power transmission system and method based on IM3. Background Technology

[0002] Wireless power transfer (WPT) and wireless energy harvesting (WEH) are promising microwave / RF technologies that can extend the battery life of wireless sensors and enable battery-free devices. Currently, these technologies are widely used in various applications, including portable devices, vehicles, robots, and medical devices.

[0003] In current WPT and communication systems, efficient and stable power transmission is crucial for the continuous operation and functional expansion of various devices. Traditional wireless technologies have many limitations. For example, short-range WPT technology based on electromagnetic induction has an extremely short effective range, typically only a few centimeters, which greatly limits the flexibility of device use. While long-range WPT technology based on radio frequency (RF) can achieve power transmission over a certain distance, the beam diverges easily during signal propagation, resulting in energy dispersion in space and low energy intensity received by the receiver, making it difficult to meet the transmission efficiency requirements of practical applications.

[0004] Third-order intermodulation (IM3) signals are parasitic signals generated when two or more signals are in a linear system. Due to nonlinear factors (typically originating from the diode's own nonlinearity in rectifier systems), the second harmonic of one signal mixes with the fundamental frequency of another. IM3 has wide applications in various fields. For example, in radar systems, IM3 helps improve radar detection and anti-jamming capabilities, enabling accurate target identification and tracking in complex environments, and significantly improving the accuracy and stability of radar systems.

[0005] In WPT, the use of IM3 signals has unique advantages. IM3 signals have inherent anti-interference characteristics. Their frequency is generated by two carrier signals through nonlinear interaction, resulting in a significant frequency difference from conventional communication or interference signals. This makes them less susceptible to interference in complex electromagnetic environments, significantly reducing the impact of external noise on the power transmission link and ensuring the stability of wireless power supply. Furthermore, the generation method of IM3 signals is flexible and easy to control. By adjusting the carrier signal parameters (such as frequency and amplitude) of the input nonlinear device, the desired frequency of the IM3 signal can be easily generated to adapt to the frequency band requirements of different scenarios, avoid frequency conflicts with other wireless systems, and improve spectrum utilization.

[0006] An existing beamback WPT system that uses the fundamental frequency signal as the pilot signal, such as Figure 1As shown, it actively transmits the system's base frequency through the power receiving end (such as the equipment to be powered). The pilot signal is received by a phased array antenna, which performs phase conjugation processing to generate a power signal that can be transmitted in reverse along the pilot signal path. However, in this scheme, the pilot signal and the power signal have the same frequency, resulting in weak anti-interference capability and the pilot signal being easily overwhelmed due to excessive power signal. Furthermore, since the receiving end needs to rectify the fundamental frequency into DC, to improve rectification efficiency, the fundamental frequency signal should be input into the rectifier device as much as possible, rather than being used as a pilot signal. Summary of the Invention

[0007] The purpose of this invention is to provide a beamback wireless power transmission system and method based on IM3.

[0008] In a first aspect, the present invention provides a beamback wireless power transmission system based on IM3, which includes a power supply end and a power receiving end.

[0009] The power receiving end includes a rectifier module, a filter module, an energy receiving antenna, a pilot signal transmitting antenna, and a second harmonic transmitting antenna. The energy receiving antenna receives a dual-tone fundamental frequency signal from the power supply end and transmits it to the rectifier module, the filter module, and the load; a second harmonic signal is generated in the rectifier module, which has nonlinear characteristics. The dual-tone fundamental frequency signal and the second harmonic signal reflected by the filter module generate a third-order intermodulation signal in the rectifier module. The second harmonic signal and the third-order intermodulation signal are transmitted externally through the second harmonic receiving phased array antenna and the pilot signal receiving phased array antenna, respectively.

[0010] The power supply terminal includes a phase processing module, an energy transmission phased array antenna, a pilot signal receiving phased array antenna, and a second harmonic receiving phased array antenna. The phase processing module receives the second harmonic signal and the third-order intermodulation signal through the pilot signal receiving phased array antenna and the second harmonic receiving phased array antenna, and generates a two-tone fundamental frequency signal that is phase-conjugate with the fundamental frequency component in the third-order intermodulation signal; the two-tone fundamental frequency signal is transmitted through the energy transmission phased array antenna and coherently superimposed at the power receiving terminal.

[0011] Preferably, the phase processing module includes a first mixer, a first low-pass filter, a second mixer, a second low-pass filter, and a signal generator. The second harmonic receiving phased array antenna, the pilot signal receiving phased array antenna, and the third-order intermodulation signal are input to the first mixer. The output of the first mixer is input to the second mixer after passing through the first low-pass filter. The signal generator provides the second mixer with frequencies of... , The two local oscillator signals; , These are the two frequencies of the dual-tone fundamental frequency signal. The output signal of the second mixer is transmitted to the energy-emitting phased array antenna after passing through the second low-pass filter.

[0012] Preferably, the output signal of the second low-pass filter in the power supply terminal is amplified by a power amplifier and transmitted to the energy-emitting phased array antenna.

[0013] Preferably, the two frequencies of the dual-tone fundamental frequency signal , The frequency difference between them is 5MHz to 35MHz.

[0014] Preferably, the rectifier module adopts a rectifier structure based on Schottky diodes.

[0015] Preferably, a signal transmission trunk is formed between the energy receiving antenna and the ground wire of the receiving end. The Schottky diode and inductor in the rectifier module are connected in series between the signal transmission trunk and the ground wire.

[0016] Preferably, the energy transmitting phased array antenna and the pilot signal receiving phased array antenna share the same phased array antenna.

[0017] Preferably, the filtering module includes an RF choke connected in series on the signal transmission trunk and one or more capacitors connected in parallel between the signal transmission trunk and ground.

[0018] Preferably, the energy receiving antenna and the pilot signal transmitting antenna share the same antenna.

[0019] Secondly, the present invention provides a beamback wireless power transmission method, which uses the aforementioned beamback wireless power transmission system. The beamback wireless power transmission method includes:

[0020] The power supply end transmits a dual-tone fundamental frequency signal via an energy-emitting phased array antenna. The power receiving end receives the dual-tone fundamental frequency signal and generates a second harmonic signal and a third-order intermodulation signal to be transmitted to the power supply end during signal transmission and reflection.

[0021] The second harmonic signal and the third-order intermodulation signal undergo phase shifting during wireless transmission before being input to the power supply. The received second harmonic signal and third-order intermodulation signal are then mixed and low-pass filtered to generate the final signal. .Signal It is the low-frequency component of the mixed signal of the second harmonic signal and the third-order intermodulation signal.

[0022] The signal generator generates a frequency of The first local oscillator signal and frequency are The second local oscillator signal. , These are the two frequencies of the two-tone fundamental frequency signal. After being mixed and low-pass filtered with the first local oscillator signal, a first baseband signal is generated to compensate for phase shift during wireless transmission; After being mixed with the second local oscillator signal and low-pass filtered, a second baseband signal is generated to compensate for the phase shift in wireless transmission.

[0023] The first and second baseband signals are amplified and transmitted as dual-tone baseband signals, and coherently superimposed at the receiving end to achieve beamback and improve wireless power supply efficiency.

[0024] The present invention has the following beneficial effects.

[0025] 1. In the first mixer, the IM3 signal from the power receiving end ( ), second harmonic signal ( These are used as pilot signals and local oscillator signals, respectively. Since the pilot signals and local oscillator signals originate from the same power receiving end and propagate to the power supply phased array via the same path, they naturally carry the same offset phase. The consistency of the physical propagation path ensures that environmental changes have the same impact on both, and the residual error after cancellation is negligible. Utilizing this characteristic, this invention can achieve physical cancellation of the offset phase without an additional calibration module. Furthermore, this invention uses the IM3 signal as the pilot signal, which avoids the pilot signal being overwhelmed due to excessive power signals.

[0026] 2. This invention does not affect the power receiving end. and In both frequency band rectification scenarios, reverse backtracking is achieved through the IM3 signal in conjunction with the second harmonic signal, enabling the power supply end to dynamically adapt to the power receiving end in motion. Furthermore, by adjusting the local oscillator frequency, this invention can achieve multi-frequency band reverse backtracking without altering the hardware structure, eliminating the need to design calibration links for different individual frequencies.

[0027] 3. Existing technologies require independent calibration links for different transmission frequencies, and the hardware complexity increases linearly when extended to multiple frequency bands. In contrast, this invention achieves multi-band beamback by adjusting the local oscillator frequency, requiring only the replacement of the first and second local oscillator signals provided by the signal generator, significantly reducing hardware costs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a traditional beamback WPT system.

[0029] Figure 2 This is a schematic diagram of the overall framework of Embodiment 1 of the present invention.

[0030] Figure 3This is a schematic diagram of the circuit principle of the power receiving end in Embodiment 1 of the present invention.

[0031] Figure 4 This is a schematic diagram of the circuit principle of the power supply terminal in Embodiment 1 of the present invention.

[0032] Figure 5 This is a schematic diagram of the specific circuit in Embodiment 1 of the present invention, in which the energy receiving antenna and the pilot signal transmitting antenna are shared.

[0033] Figure 6 This is a schematic diagram of the specific circuit shared by the energy emission phased array antenna and the pilot signal receiving phased array antenna in Embodiment 1 of the present invention.

[0034] Figure 7 This is a schematic diagram illustrating the phase shift principle generated by the pilot signal during propagation in Embodiment 1 of the present invention.

[0035] Figure 8 This is the radiation pattern of the energy-emitting phased array antenna under different phase differences in Embodiment 1 of the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings.

[0037] like Figure 2 As shown, a beamback wireless power transmission system based on IM3 includes a power supply end and a power receiving end.

[0038] like Figure 2 and Figure 3 As shown, the power supply terminal includes a phase processing module, a power transmission phased array antenna (WPTTxs), a pilot signal receiving phased array antenna (Pilot Rxs), a second harmonic receiving phased array antenna (Secomd HarmonicRxs), and a power supply module (PA).

[0039] The phase processing module is used to generate a phase-conjugated signal for the second harmonic and IM3 signal (third-order intermodulation signal), so that the energy transmission phased array antenna at the power supply end uses the phase-conjugated signal as a carrier to transmit in reverse along the original pilot signal propagation path, forming coherent superposition at the power receiving end, realizing energy accumulation, and supplying power to the power receiving end.

[0040] The phase processing module includes a first mixer (Mix1), a first low-pass filter (LPF1), a second mixer (Mix2), a second low-pass filter (LPF1), and a signal generator (sg). The pilot signal receiving phased array antenna and the second harmonic receiving phased array antenna are connected to the two input interfaces (RF and LO) of the first mixer. The output interface (IF) of the first mixer and the signal generator is connected to the two input interfaces (RF and LO) of the second mixer. A first low-pass filter is provided between the first and second mixers. The output interface (IF) of the second mixer is connected to the energy transmitting phased array antenna via the second low-pass filter and a power supply module. The power supply module is a power amplifier. The signal generator is used to generate a frequency of... , The two local oscillator signals; , These are two baseband signals.

[0041] like Figure 2 and Figure 4 As shown, the power receiving terminal includes a rectifier module, a filter module, an energy storage module, a power receiving antenna (WPT Rx), a pilot signal transmitting antenna (Pilot Tx), and a second harmonic transmitting antenna (Secomd Harmonic Tx). A signal transmission trunk is formed between the power receiving antenna and the ground wire. A DC blocking capacitor C is connected sequentially on the signal transmission trunk. block The system includes a rectifier module, a filter module, and an energy storage module. The DC blocking capacitor C... block The rectifier module is connected in series between the signal transmission trunk and ground. It includes a Schottky diode and a rectifier inductor L1 connected in series between the signal transmission trunk and ground. The filter module uses an LC filter and includes an RF choke coil RF. choke Capacitors C1 and C2. The RF choke... choke The capacitors C1 and C2 are connected in series in the signal transmission trunk. The capacitors C1 and C2 are connected in parallel between the signal transmission trunk and ground. The rectifier module, filter module, and energy storage module are connected in sequence.

[0042] In this embodiment, the energy receiving antenna, the pilot signal transmitting antenna, and the second harmonic transmitting antenna are all connected to the input end of the signal transmission trunk.

[0043] In some embodiments, the energy storage module may be replaced with other forms of energy-consuming load.

[0044] The core of the beamback wireless power transmission system based on IM3 provided in this embodiment is to directly process IM3 by introducing a second harmonic. This system can achieve precise reverse orientation without a microcontroller unit. IM3 and the second harmonic signal are simultaneously emitted by the receiving antenna and travel along the same spatial path to the phased array antenna of the power supply section. The received signal is processed by a phase conjugation module to generate a phase-conjugated signal. Because the phase conjugation characteristic cancels out the channel's influence on the phase, the phased array antenna at the power supply end uses the phase-conjugated signal as a carrier to transmit it in reverse along the original pilot signal propagation path, forming coherent superposition at the receiving end, achieving energy concentration, and supplying power to the receiving end.

[0045] The wireless directional power supply method of the beamback wireless power transmission system is as follows:

[0046] Step 1: The receiving end receives a signal from the supply end at a frequency of [frequency value missing]. , The two-tone fundamental frequency signal, when passing through the rectifier module, generates a frequency of [frequency value missing] due to the nonlinear characteristics of the Schottky diode. , The second harmonic signal. After reflection by the filter module, the second harmonic signal and the dual-tone fundamental frequency signal generate a frequency of [frequency value missing] due to the nonlinear characteristics of the Schottky diode. , The IM3 signal is generated through direct mixing, upmixing, and downmixing. Direct mixing originates from the interaction of the two-tone fundamental frequency signals. Upmixing originates from the difference frequency signal of the two-tone fundamental frequency signals. Downmixing originates from the second harmonic signal.

[0047] Step 2: The second harmonic signal and IM3 signal generated by the power receiving end are transmitted to the power supply end through the second harmonic transmitting antenna and the pilot signal transmitting antenna, respectively. The second harmonic receiving phased array antenna and the pilot signal receiving phased array antenna of the power supply end receive the second harmonic signal and IM3 signal from the power receiving end, respectively.

[0048] Step 3: The phase processing module in the power supply end uses the second harmonic signal and the IM3 signal to provide directional power to the receiving end. Its working principle is as follows:

[0049] Due to the two third-order intermodulation components of the IM3 signal (frequency: , The analysis principle is similar to that of the components. To simplify the analysis, we will only analyze the frequency of the components below. The third-order intermodulation component is one of the components, and the other third-order intermodulation component will not be discussed further.

[0050] In this scheme, the receiving end needs to transmit two signals: IM3 and the second harmonic. Since the starting and ending points of the signals are the same in space, and according to Equation 4, the phase difference generated during the journey is linearly related to the frequency. Let the frequency of the pilot signal (i.e., the IM3 signal) transmitted by the receiving end be denoted as . The second harmonic frequency is The specific form can be expressed by the following formula:

[0051] (8)

[0052] (9)

[0053] in, This is the transmitted IM3 signal. t represents the transmitted second harmonic signal; t represents time.

[0054] After passing the distance After propagation, the signal received by the phased array becomes:

[0055] (10)

[0056] (11)

[0057] in, For the received IM3 signal; The received second harmonic signal; It is the frequency in the fundamental frequency signal The propagation phase, It is the frequency in the fundamental frequency signal The propagation phase.

[0058] Since the second harmonic and IM3 signals are transmitted in the same channel, the phased array antenna at the power supply end will also carry the second harmonic signal when receiving it. Phase shift.

[0059] Signal The signal is connected to the RF terminal of the first mixer. Connecting to the LO terminal of the first mixer, the output of the mixer's IF terminal can be calculated as follows:

[0060] (12)

[0061] in, This is the output signal of the first mixer.

[0062] High frequency components Independent of the target frequency, but low-frequency components To filter out the desired low-frequency components using a first low-pass filter, matching the target frequency, the following formula can be used:

[0063] (13)

[0064] in, This is the output signal of the first low-pass filter.

[0065] To achieve reverse signal orientation, the energy-emitting phased array antenna needs to transmit signals... Phase-conjugated signals.

[0066] The signal generator generates a frequency of The signal is used as the first local oscillator signal, and the signal is... After mixing with the first local oscillator signal and passing it through a low-pass filter, the result can be obtained. Phase conjugate signal:

[0067] (14)

[0068] in, This is the first output signal of the second low-pass filter.

[0069] The phase conjugate signal corresponding to the expression in Formula 14 After power amplification, the first fundamental frequency signal transmitted by the phased array antenna can be obtained, and phase is superimposed during propagation. The total phase at the receiving end is This allows for focused attention.

[0070] At the same time, the signal generator produces a frequency of The signal is used as the second local oscillator signal. After mixing and filtering with the second local oscillator signal, the following signal is obtained:

[0071] (15)

[0072] in, This is the second output signal of the second low-pass filter.

[0073] Although the phase at this time Phase of arrival as expected It has some deviation, but in practical applications, and With similar frequencies, the phase shifts produced by the two are also similar. Even with a certain phase shift, a WPT receiving antenna with good beam direction can still be produced.

[0074] In this embodiment, two base frequency signals , The frequency difference is 7.5MHz. In some embodiments, the two baseband signals , The frequency difference is less than or equal to 35MHz, preferably 5MHz to 35MHz.

[0075] In this embodiment, the energy-emitting phased array antenna transmits two baseband signals. , The phase of the signal is conjugate with the phases of the frequency w1 and frequency w2 components in the original third-order intermodulation signal, thus enabling the entire process of beamback WPT without the need for any additional microcontroller unit.

[0076] In this embodiment, the process of the receiving end generating the IM3 signal is analyzed as follows:

[0077] Step 1: Construct the equivalent model of the diode rectifier circuit and the expression for the node voltage of the two-tone signal.

[0078] To analyze the intermodulation signal generated by the nonlinear characteristics of a diode, an equivalent circuit model of a Schottky diode is constructed. This model includes an RF source. DC blocking capacitor Diode junction capacitance Diode junction resistance Choke inductor and DC load .

[0079] When a dual-tone signal is input, the junction voltage across the diode... It can be represented as

[0080] (16)

[0081] in and These are the angular frequencies of the two signals, with A and B being their respective effective values.

[0082] The IM3 signal contains the intermodulation frequency components generated by the diode. and Two components. Since the analysis principles for the two third-order intermodulation signals are the same, for the sake of simplicity, only the following analysis will focus on those components. The other component will not be discussed further.

[0083] Step 2: Derive the diode junction current expression based on Kirchhoff's current law.

[0084] According to Kirchhoff's current law, the specific expression for the junction current of a diode is:

[0085] (17)

[0086] in, This is the reverse saturation current of the diode; ( For unit charge, Emission factor Boltzmann's constant, (Kelvin temperature) This represents the amount of charge accumulated on the junction capacitance.

[0087] Step 3: Taylor expansion of diode junction current

[0088] Since the intermodulation signal is generated by the nonlinear characteristics of the diode, when the diode bias voltage is 0, the Taylor formula is used to expand equation (17) to the third order, resulting in:

[0089] (18)

[0090] in, Zero-bias junction capacitance Junction potential This is the gradient coefficient constant.

[0091] Step 4: Analysis of the Three Processes of Diode Mixing to Generate IM3

[0092] The IM3 signal generated by diode mixing involves three mixing processes:

[0093] (1) Direct mixing IMD3: It is directly generated by the cubic term in formula (18) and is the result of the interaction of two-tone fundamental frequency signals;

[0094] (2) Up-mixing IMU3: The dual-frequency excitation signal is first mixed, and the difference frequency signal (IM2) is generated by the square term in formula (18), and then mixed with the original frequency. The signal undergoes secondary mixing, still generated by the squared term in formula (18);

[0095] (3) Down-mixing IMS3: The dual-frequency excitation signal is first mixed in the first stage, and the second harmonic is generated by the square term in formula (18). And then with the original The signal is mixed twice, which is also generated by the square term in formula (18).

[0096] In this embodiment, the Taylor expansion is only retained up to the third-order term, based on the engineering analysis premise that "the third-order intermodulation signal is the main interference component". In some high-precision analysis scenarios, it can be extended to higher-order terms as needed, but the core analysis logic is consistent with the third-order expansion.

[0097] In this embodiment, the process of beamback in the power supply section is analyzed as follows:

[0098] Step 1: Constructing the far-field plane wave receiving model and the basic formula for compensating phase shift

[0099] To analyze the beamback principle of a phased array antenna, we first clarify the far-field conditions of the antenna and the equivalent model of a plane wave:

[0100] (1) Far-field region division: According to electromagnetic theory, when the distance from the antenna center to the observation point is... satisfy At that time, the spatial region is the far-field region ( This is the maximum linear dimension of the antenna. (This refers to the operating wavelength). Wireless power transmission in this system occurs in the far-field region, where the electromagnetic waves received by the antenna can be equivalent to plane waves (e.g., ...). Figure 7 As shown, This represents the wavefront distance between the plane wave and the second antenna after the plane wave reaches the first antenna. (This refers to the spacing between adjacent antennas).

[0101] (2) Derivation of the compensation phase shift formula: From the triangular relationship in Figure 7, we get ( (where is the angle between the beam and the phased array normal). The phase difference caused by this additional distance is the phase that needs to be canceled during beam backtracking. Combining distance, phase, and wavelength, we can derive:

[0102] (19)

[0103] in, This is to compensate for the phase difference between adjacent antennas. After the wave propagates in space, and For a constant value, and It exhibits a linear correlation; for the first 1 antenna (distance from the first antenna is) ), its corresponding phase is .

[0104] Step 2: Numerical calculation of phase shift compensation and beamback verification

[0105] Taking a real-world scenario as an example, we will verify the role of phase shift compensation in beam backtracking:

[0106] (1) Calculation of phase difference at the receiver: Let the angle between the beam and the normal be set. (30°), antenna spacing Substituting into formula (19), we get: That is, antenna 2 receives signals later than antenna 1. Phase.

[0107] (2) Transmitter phase compensation calculation: The direction is reversed during beam backtracking. Substituting into formula (19) again, we get This indicates that when transmitting signals, antenna 2 needs to be ahead of antenna 1. Phase, enabling the beam to trace back along the original path.

[0108] Step 3: Phased array pattern modeling based on DFT analogy

[0109] By analogy with the Discrete Fourier Transform (DFT), the expression for the phased array radiation pattern is derived:

[0110] (1) Basic principle of DFT: DFT decomposes a discrete-time signal into different discrete sequences. and reference frequency The expression is:

[0111] (20)

[0112] (2) Phased array pattern analogy: Each antenna element of the phased array is regarded as a discrete sequence. (Amplitude weight, set to 1 for simplified analysis), the reference frequency of the DFT is analogous to the phase weight. ( For wave number, (This refers to the order of antenna elements).

[0113] (3) Derivation of the radiation pattern formula: Based on the above analogy, the expression for the radiation pattern of a phased array antenna is:

[0114] (twenty one)

[0115] like Figure 8 As shown, when Time beam along the normal direction ( ), Time beam pointing This verifies that beam pointing can be precisely controlled by compensating for phase shift.

[0116] Step 4: Beamback Signal Processing Flow Based on IM3 Pilots

[0117] Using the IM3 signal as a pilot, beamback is achieved through two mixing operations. The specific process is as follows:

[0118] (1) IM3 pilot signal transmission: The receiving end generates the IM3 signal (frequency) through a Schottky diode (using Avago HSMS286, low built-in voltage / junction capacitance). = 903 MHz), the expression is: (A represents the signal amplitude, determined by the diode's nonlinear coefficient). Simultaneously, the second harmonic is emitted. (correspond Furthermore, the WPT signal and the pilot signal share the same antenna (transmitter: energy transmission and pilot reception share the same phased array; receiver: energy reception and pilot transmission share the same antenna).

[0119] (2) Received signal phase shift: When the phased array receives the IM3 signal, a phase shift occurs due to the propagation distance "d", and the received signal is: ,in , The phase shift of the second harmonic received signal is .

[0120] (3) First mixing and filtering: The second harmonic signal is used as the local oscillator signal of the first mixer, i.e. , The radio frequency signal is used as the first mixer. The intermediate frequency signal obtained through the first mixer is... The 2724MHz high-frequency component is filtered out by a low-pass filter, retaining the 918MHz signal. .

[0121] (4) Implementation of the second mixing and backtracking:

[0122] a. When the signal generator outputs a 1836MHz signal, and... After mixing and filtering This signal can naturally achieve beamback;

[0123] b. When the signal generator outputs a 1828.5MHz signal, the result after mixing and filtering is... Because the difference between the two fundamental frequencies (910.5MHz / 918MHz) is small, effective backtracking can still be achieved.

[0124] In this embodiment, IM3 is selected as the pilot signal. Its core advantage is that no additional microcontroller unit (MCU) is required. The power supply transmission signal can be directly generated through two mixing operations. Furthermore, the shared antenna design simplifies the system structure and meets the engineering practical requirements of wireless power transfer (WPT).

[0125] In this embodiment, the IM3 signal serves as a pilot signal. The IM3 signal is generated by the nonlinear characteristics of a Schottky diode. In some other embodiments, the IM3 signal can also be generated by other devices with nonlinear responses, such as RF transistors or nonlinear transmission lines. Simply adjust the device's operating point to stabilize the output. The frequency component can replace the Schottky diode as the pilot frequency generation source.

[0126] This embodiment uses a mixer to perform phase extraction. In some other embodiments, a balanced mixer (such as a dual-diode balanced structure) or a Gilbert unit active mixer is selected. These devices suppress even-order harmonic interference through differential structures, resulting in a cleaner output. phase The signal is particularly suitable for scenarios with higher requirements for spurious suppression, and can also realize the core function of beamback.

[0127] In this embodiment, the rectifier module includes only a parallel Schottky diode and a corresponding matching circuit. However, there are various structures for rectifier circuits based on Schottky diodes, such as voltage multiplication structures and series structures. Using these structures, the required rectification function can also be achieved.

Claims

1. A beamback wireless power transmission system based on IM3, comprising a power supply end and a power receiving end; the power receiving end includes a rectifier module, a filter module, and a power receiving antenna; the power supply end includes a power transmitting phased array antenna; characterized in that: The receiving end also includes a pilot signal transmitting antenna and a second harmonic transmitting antenna; the energy receiving antenna receives the dual-tone fundamental frequency signal from the power supply end and transmits it to the rectifier module, the filter module, and the load; the second harmonic signal is generated in the rectifier module with nonlinear characteristic devices; the dual-tone fundamental frequency signal and the second harmonic signal reflected by the filter module generate a third-order intermodulation signal in the rectifier module; the second harmonic signal and the third-order intermodulation signal are transmitted externally through the second harmonic receiving phased array antenna and the pilot signal receiving phased array antenna, respectively; The power supply terminal also includes a phase processing module, a pilot signal receiving phased array antenna, and a second harmonic receiving phased array antenna; the phase processing module receives the second harmonic signal and the third-order intermodulation signal through the pilot signal receiving phased array antenna and the second harmonic receiving phased array antenna, and generates a dual-tone fundamental frequency signal that is phase-conjugate with the fundamental frequency component in the third-order intermodulation signal; the dual-tone fundamental frequency signal is transmitted through the energy transmission phased array antenna.

2. The beamback wireless power transfer system based on IM3 according to claim 1, characterized in that: The phase processing module includes a first mixer, a first low-pass filter, a second mixer, a second low-pass filter, and a signal generator. The second harmonic receiving phased array antenna, the pilot signal receiving phased array antenna, and the third-order intermodulation signal are input to the first mixer. The output of the first mixer is passed through the first low-pass filter and then input to the second mixer. The signal generator provides the second mixer with frequencies of... , The two local oscillator signals; , These are the two frequencies of the dual-tone fundamental frequency signal; the output signal of the second mixer is transmitted to the energy-emitting phased array antenna after passing through the second low-pass filter.

3. The beamback wireless power transfer system based on IM3 according to claim 2, characterized in that: The output signal of the second low-pass filter in the power supply terminal is amplified by a power amplifier and transmitted to the energy-emitting phased array antenna.

4. A beamback wireless power transfer system based on IM3 according to claim 2, characterized in that: The two frequencies of the dual-tone fundamental frequency signal , The frequency difference between them is 5MHz to 15MHz.

5. A beamback wireless power transmission system based on IM3 according to claim 1, characterized in that: The rectifier module adopts a rectifier structure based on Schottky diodes.

6. A beamback wireless power transmission system based on IM3 according to claim 5, characterized in that: The energy receiving antenna and the ground wire of the receiving end form a signal transmission trunk; the Schottky diode and inductor in the rectifier module are connected in series between the signal transmission trunk and the ground wire.

7. A beamback wireless power transfer system based on IM3 according to claim 1, characterized in that: The energy-emitting phased array antenna and the pilot signal receiving phased array antenna share the same phased array antenna.

8. A beamback wireless power transmission system based on IM3 according to claim 1, characterized in that: The filtering module includes an RF choke connected in series on the signal transmission trunk and one or more capacitors connected in parallel between the signal transmission trunk and the ground wire.

9. A beamback wireless power transfer system based on IM3 according to claim 1, characterized in that: The energy receiving antenna and the pilot signal transmitting antenna share the same antenna.

10. A beamback wireless power transmission method, characterized in that: Using the beamback wireless power transmission system as described in claim 2; The beamback wireless power transfer method includes: The power supply terminal transmits dual-tone fundamental frequency signals through an energy-emitting phased array antenna. The receiving end receives the dual-tone fundamental frequency signal and generates a second harmonic signal and a third-order intermodulation signal to be transmitted to the power supply end during signal transmission and reflection. The second harmonic signal and the third-order intermodulation signal undergo phase shifting during wireless transmission before being input to the power supply. The received second harmonic signal and third-order intermodulation signal are then mixed and low-pass filtered to generate a signal. ; The signal generator generates a frequency of The first local oscillator signal and frequency are The second local oscillator signal; , These are the two frequencies of the dual-tone fundamental frequency signal; signal After being mixed and low-pass filtered with the first local oscillator signal, a first baseband signal is generated to compensate for phase shift during wireless transmission; After being mixed with the second local oscillator signal and low-pass filtered, a second baseband signal is generated to compensate for the phase shift in wireless transmission. The first and second baseband signals are amplified and transmitted as dual-tone baseband signals, and coherently superimposed at the receiving end.

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