| With the rapid development of the Internet of Things technology and the continuous emergence of low-power electronic devices,energy supply of these electronic devices has become a research hotspot in the field.Aiming at the abundant energy that exists naturally in the environment,harvesting and utilizing these energy through artificial means has a very broad application prospect.Aiming at the radio frequency energy and vibration energy in the environment,this paper proposes the energy harvesting technology of radio frequency and vibration based on piezoelectric materials.By adding piezoelectric materials to the antenna dielectric layer,forming a structure that integrates the two kinds of energy harvesting,which breaking the traditional single limitation of energy harvesting.The design and optimization scheme of the high-efficiency rectifier circuit is proposed,and the corresponding rectifier circuit structure is optimized.Finally,two hybrid energy harvesting systems are designed,then tested and analyzed.The specific steps and results are as follows:1.A dual-band energy harvesting antenna based on PVDF piezoelectric material is designed.The antenna uses a PVDF piezoelectric film as a dielectric layer material,and its surface is covered with a copper sticker as a radiating unit,thereby achieving a miniaturized design of the antenna.The measured bandwidth of the designed antenna is 2.3GHz-2.7GHz and 5.6GHz-6.2GHz,which can cover the 2.4GHz wireless Wi-Fi frequency band and the 5.8GHz common ISM communication frequency band.The resonance frequency points are 2.48 GHz and 5.95 GHz,and the corresponding gain amplitudes values are 0.77 dB and 2.47dB;2.An energy harvesting antenna based on FR4 board and PVDF piezoelectric material is designed.The antenna is etched on FR4 board and a PVDF piezoelectric film is pasted on the lower surface of FR4 board.Both of them constitute the dielectric layer of the antenna.The designed measured bandwidth of the antenna is 2.1GHz-2.5GHz,which can cover the 2.4GHz wireless Wi-Fi frequency band,the resonance frequency point is 2.4GHz,and the gain amplitude is-3.4dB;3.For two different antennas,two types of RF rectifier circuits are designed.This article first selects the SMS7630 diode as a rectifier device,tunes and optimizes the capacitance and load value of the rectifier circuit,and then builds corresponding matching networks.The single-band antenna rectifier circuit is completed by etching the microstrip line on the FR4 board,and the final measured rectification efficiency is 51% at 2.4GHz.The dual-band antenna rectifier circuit is completed by packaging the PCB board.The actual measured rectifier efficiency at the corresponding resonant frequency points of 2.4GHz and 5.8GHz is 51% and 57% respectively;4.A low-frequency rectifier circuit is designed for the vibration energy harvesting by the piezoelectric film.In order to obtain a higher and more stable output voltage,the circuit is optimized and simulated in Multisim software.The measured output voltage amplitude is 3V and the effective value is 2.12V;The voltage conversion is 106.1%,the ripple voltage is 0.2V,the ripple voltage coefficient is 6.67%,and the time required to reach steady-state voltage is 0.41 seconds;5.A vibration experiment platform is designed,and two hybrid energy harvesting systems are set up,tested and analyzed.The single-band RF antenna hybrid energy harvesting system has an output voltage and power of 1.34 V and 179.6?W respectively under the RF input excitation of-3dBm;and an output voltage and power of 1.12 V and 624.8?W under the excitation of 17 Hz vibration.The dual-band RF antenna hybrid energy harvesting system can output voltage and power of 1.82 V and 331.24?W respectively under the RF input excitation of 3dBm;under 16 Hz vibration excitation,it can output the maximum voltage and power of 1.07 V and 572.45?W.The output energy magnitude can fully meet the self-power requirements of low-power electronics and sensor nodes. |
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