Circuit designs Energy harvesting Energy propagation Energy propagation model Industrial research Internet of things Internet protocols MAC protocol for radio frequency power harvesting MAC protocols for RF power harvesting Mac protocols Medium access control Power harvesting Propagation models RF circuit design RF powered wireless networks RF-harvesting techniques Radio frequency circuit Radio frequency circuit design Radio frequency power Radio frequency powered wireless network Radio frequency-harvesting technique Radio waves Radiofrequencies Sensor networks Surveys Timing circuits Wireless networks energy harvesting energy propagation models