A structure simplification method and its validity of filament-woven fabrics in the screen-printed antenna simulation model for RF energy harvesting
Radio frequency energy harvesting(RFEH)technology has been applied widely in the development of wearable electronic power supply systems because of its eco-friendly and highly efficient characteristics.In the RFEH system,the receiving antenna collects electromagnetic waves through electromagnetic coupling technology.Obviously,the receiving antenna plays a crucial role in the energy harvesting efficiency of the RFEH system.Generally,the antenna performance can be optimized by simulation and measurement.In the simulation of screen-printed fabric-based antenna for RFEH,the establishment of a precise structure model of the substrate fabric is the basis for the simulation analysis.However,in order to save the calculation cost,most studies ignore the interwoven structural characteristics of the fabric in establishing a simulation model,which leads to a big difference between the simulation and measurement results.To guide the actual product design and engineering application evaluation through the simulation of fabric-based antennas,it is necessary to establish a fabric-based antenna model with high simulation accuracy and low calculation cost.To obtain the structural model of screen-printed woven fabric-based antenna for RFEH with high accuracy and low calculation cost,this study constructed six different simplified structural models of filament woven fabrics firstly,including interwoven meso-structure,hole combining concave-convex structure,hole structure,plane concave-convex structure,curved concave-convex structure,and uniform structure.The interaction mechanism between the woven fabric and the electromagnetic wave was simulated.Based on this,the antenna performance with different simulated structural substrates was analyzed parametrically with porosity and roughness as variables.And then,several antennas with different simplified structural substrates were prepared to verify the feasibility of the simplified structural model of the substrate in the design of the antenna for RFEH.The results show that the interwoven meso-structure can be equivalent to a model with holes and/or a concave-convex structure model by comparing the reflectivity and transmittance.And the antenna radiation performance,gain,and efficiency with the uniform substrate structural model are significantly high.In addition,the structure model with a rough surface has a more significant effect on the antenna performance than the non-rough surface structure model.Furthermore,the model prediction and measured results of the antenna RFEH performance in the ultra-high frequency(UHF)range were compared.It is found that there is no significant difference between the two,and there is no significant difference among different simplified structure models.The maximum transmission distance of the antenna reaches 220 cm,and the received signal strength indication(RSSI)of unit area at 1 m distance exceeds 8.442 mW/cm2.The output voltage and power conversion efficiency of the antenna are up to 135 mV and 60％,respectively.Consequently,in order to save the calculation cost,the filament plain woven fabric substrate with a porosity of less than 30％and a roughness of less than 5.39 μm can be equivalent to a uniform medium model in the simulation of screen-printed antenna for RFEH in the ultra-high frequency range.An effective simulation method for woven fabric-based printed antenna for radio frequency energy harvesting in the ultra-high frequency range with high accuracy and low computational cost is provided by simplifying the fabric structure of holes and surface texture features.This method of model simplification has certain reference meanings for the model simplification of the antenna with complex structure applied to other fields.Furthermore,this high-precision simulation model contributes to predicting the performance of the fabric-based antenna and optimizing the design of the fabric-based antenna,so that fabric-based RFEH antennas can be applied to more extensive fields.
radio frequency energy harvestingantennafabric substratesimulation modelfabric structureporositytransmission distance
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